Adding upstream version 1.22.1.upstream/1.22.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

32 files changed, 9369 insertions, 0 deletions

diff --git a/src/strconv/atob.go b/src/strconv/atob.go
new file mode 100644
index 0000000..0a49500
--- /dev/null
+++ b/src/strconv/atob.go
@@ -0,0 +1,35 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv
+
+// ParseBool returns the boolean value represented by the string.
+// It accepts 1, t, T, TRUE, true, True, 0, f, F, FALSE, false, False.
+// Any other value returns an error.
+func ParseBool(str string) (bool, error) {
+	switch str {
+	case "1", "t", "T", "true", "TRUE", "True":
+		return true, nil
+	case "0", "f", "F", "false", "FALSE", "False":
+		return false, nil
+	}
+	return false, syntaxError("ParseBool", str)
+}
+
+// FormatBool returns "true" or "false" according to the value of b.
+func FormatBool(b bool) string {
+	if b {
+		return "true"
+	}
+	return "false"
+}
+
+// AppendBool appends "true" or "false", according to the value of b,
+// to dst and returns the extended buffer.
+func AppendBool(dst []byte, b bool) []byte {
+	if b {
+		return append(dst, "true"...)
+	}
+	return append(dst, "false"...)
+}
diff --git a/src/strconv/atob_test.go b/src/strconv/atob_test.go
new file mode 100644
index 0000000..40d43a9
--- /dev/null
+++ b/src/strconv/atob_test.go
@@ -0,0 +1,91 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv_test
+
+import (
+	"bytes"
+	. "strconv"
+	"testing"
+)
+
+type atobTest struct {
+	in  string
+	out bool
+	err error
+}
+
+var atobtests = []atobTest{
+	{"", false, ErrSyntax},
+	{"asdf", false, ErrSyntax},
+	{"0", false, nil},
+	{"f", false, nil},
+	{"F", false, nil},
+	{"FALSE", false, nil},
+	{"false", false, nil},
+	{"False", false, nil},
+	{"1", true, nil},
+	{"t", true, nil},
+	{"T", true, nil},
+	{"TRUE", true, nil},
+	{"true", true, nil},
+	{"True", true, nil},
+}
+
+func TestParseBool(t *testing.T) {
+	for _, test := range atobtests {
+		b, e := ParseBool(test.in)
+		if test.err != nil {
+			// expect an error
+			if e == nil {
+				t.Errorf("ParseBool(%s) = nil; want %s", test.in, test.err)
+			} else {
+				// NumError assertion must succeed; it's the only thing we return.
+				if e.(*NumError).Err != test.err {
+					t.Errorf("ParseBool(%s) = %s; want %s", test.in, e, test.err)
+				}
+			}
+		} else {
+			if e != nil {
+				t.Errorf("ParseBool(%s) = %s; want nil", test.in, e)
+			}
+			if b != test.out {
+				t.Errorf("ParseBool(%s) = %t; want %t", test.in, b, test.out)
+			}
+		}
+	}
+}
+
+var boolString = map[bool]string{
+	true:  "true",
+	false: "false",
+}
+
+func TestFormatBool(t *testing.T) {
+	for b, s := range boolString {
+		if f := FormatBool(b); f != s {
+			t.Errorf("FormatBool(%v) = %q; want %q", b, f, s)
+		}
+	}
+}
+
+type appendBoolTest struct {
+	b   bool
+	in  []byte
+	out []byte
+}
+
+var appendBoolTests = []appendBoolTest{
+	{true, []byte("foo "), []byte("foo true")},
+	{false, []byte("foo "), []byte("foo false")},
+}
+
+func TestAppendBool(t *testing.T) {
+	for _, test := range appendBoolTests {
+		b := AppendBool(test.in, test.b)
+		if !bytes.Equal(b, test.out) {
+			t.Errorf("AppendBool(%q, %v) = %q; want %q", test.in, test.b, b, test.out)
+		}
+	}
+}
diff --git a/src/strconv/atoc.go b/src/strconv/atoc.go
new file mode 100644
index 0000000..f6fdd14
--- /dev/null
+++ b/src/strconv/atoc.go
@@ -0,0 +1,105 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv
+
+const fnParseComplex = "ParseComplex"
+
+// convErr splits an error returned by parseFloatPrefix
+// into a syntax or range error for ParseComplex.
+func convErr(err error, s string) (syntax, range_ error) {
+	if x, ok := err.(*NumError); ok {
+		x.Func = fnParseComplex
+		x.Num = cloneString(s)
+		if x.Err == ErrRange {
+			return nil, x
+		}
+	}
+	return err, nil
+}
+
+// ParseComplex converts the string s to a complex number
+// with the precision specified by bitSize: 64 for complex64, or 128 for complex128.
+// When bitSize=64, the result still has type complex128, but it will be
+// convertible to complex64 without changing its value.
+//
+// The number represented by s must be of the form N, Ni, or N±Ni, where N stands
+// for a floating-point number as recognized by ParseFloat, and i is the imaginary
+// component. If the second N is unsigned, a + sign is required between the two components
+// as indicated by the ±. If the second N is NaN, only a + sign is accepted.
+// The form may be parenthesized and cannot contain any spaces.
+// The resulting complex number consists of the two components converted by ParseFloat.
+//
+// The errors that ParseComplex returns have concrete type *NumError
+// and include err.Num = s.
+//
+// If s is not syntactically well-formed, ParseComplex returns err.Err = ErrSyntax.
+//
+// If s is syntactically well-formed but either component is more than 1/2 ULP
+// away from the largest floating point number of the given component's size,
+// ParseComplex returns err.Err = ErrRange and c = ±Inf for the respective component.
+func ParseComplex(s string, bitSize int) (complex128, error) {
+	size := 64
+	if bitSize == 64 {
+		size = 32 // complex64 uses float32 parts
+	}
+
+	orig := s
+
+	// Remove parentheses, if any.
+	if len(s) >= 2 && s[0] == '(' && s[len(s)-1] == ')' {
+		s = s[1 : len(s)-1]
+	}
+
+	var pending error // pending range error, or nil
+
+	// Read real part (possibly imaginary part if followed by 'i').
+	re, n, err := parseFloatPrefix(s, size)
+	if err != nil {
+		err, pending = convErr(err, orig)
+		if err != nil {
+			return 0, err
+		}
+	}
+	s = s[n:]
+
+	// If we have nothing left, we're done.
+	if len(s) == 0 {
+		return complex(re, 0), pending
+	}
+
+	// Otherwise, look at the next character.
+	switch s[0] {
+	case '+':
+		// Consume the '+' to avoid an error if we have "+NaNi", but
+		// do this only if we don't have a "++" (don't hide that error).
+		if len(s) > 1 && s[1] != '+' {
+			s = s[1:]
+		}
+	case '-':
+		// ok
+	case 'i':
+		// If 'i' is the last character, we only have an imaginary part.
+		if len(s) == 1 {
+			return complex(0, re), pending
+		}
+		fallthrough
+	default:
+		return 0, syntaxError(fnParseComplex, orig)
+	}
+
+	// Read imaginary part.
+	im, n, err := parseFloatPrefix(s, size)
+	if err != nil {
+		err, pending = convErr(err, orig)
+		if err != nil {
+			return 0, err
+		}
+	}
+	s = s[n:]
+	if s != "i" {
+		return 0, syntaxError(fnParseComplex, orig)
+	}
+	return complex(re, im), pending
+}
diff --git a/src/strconv/atoc_test.go b/src/strconv/atoc_test.go
new file mode 100644
index 0000000..4c1aad0
--- /dev/null
+++ b/src/strconv/atoc_test.go
@@ -0,0 +1,229 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv_test
+
+import (
+	"math"
+	"math/cmplx"
+	"reflect"
+	. "strconv"
+	"testing"
+)
+
+var (
+	infp0 = complex(math.Inf(+1), 0)
+	infm0 = complex(math.Inf(-1), 0)
+	inf0p = complex(0, math.Inf(+1))
+	inf0m = complex(0, math.Inf(-1))
+
+	infpp = complex(math.Inf(+1), math.Inf(+1))
+	infpm = complex(math.Inf(+1), math.Inf(-1))
+	infmp = complex(math.Inf(-1), math.Inf(+1))
+	infmm = complex(math.Inf(-1), math.Inf(-1))
+)
+
+type atocTest struct {
+	in  string
+	out complex128
+	err error
+}
+
+func TestParseComplex(t *testing.T) {
+	tests := []atocTest{
+		// Clearly invalid
+		{"", 0, ErrSyntax},
+		{" ", 0, ErrSyntax},
+		{"(", 0, ErrSyntax},
+		{")", 0, ErrSyntax},
+		{"i", 0, ErrSyntax},
+		{"+i", 0, ErrSyntax},
+		{"-i", 0, ErrSyntax},
+		{"1I", 0, ErrSyntax},
+		{"10  + 5i", 0, ErrSyntax},
+		{"3+", 0, ErrSyntax},
+		{"3+5", 0, ErrSyntax},
+		{"3+5+5i", 0, ErrSyntax},
+
+		// Parentheses
+		{"()", 0, ErrSyntax},
+		{"(i)", 0, ErrSyntax},
+		{"(0)", 0, nil},
+		{"(1i)", 1i, nil},
+		{"(3.0+5.5i)", 3.0 + 5.5i, nil},
+		{"(1)+1i", 0, ErrSyntax},
+		{"(3.0+5.5i", 0, ErrSyntax},
+		{"3.0+5.5i)", 0, ErrSyntax},
+
+		// NaNs
+		{"NaN", complex(math.NaN(), 0), nil},
+		{"NANi", complex(0, math.NaN()), nil},
+		{"nan+nAni", complex(math.NaN(), math.NaN()), nil},
+		{"+NaN", 0, ErrSyntax},
+		{"-NaN", 0, ErrSyntax},
+		{"NaN-NaNi", 0, ErrSyntax},
+
+		// Infs
+		{"Inf", infp0, nil},
+		{"+inf", infp0, nil},
+		{"-inf", infm0, nil},
+		{"Infinity", infp0, nil},
+		{"+INFINITY", infp0, nil},
+		{"-infinity", infm0, nil},
+		{"+infi", inf0p, nil},
+		{"0-infinityi", inf0m, nil},
+		{"Inf+Infi", infpp, nil},
+		{"+Inf-Infi", infpm, nil},
+		{"-Infinity+Infi", infmp, nil},
+		{"inf-inf", 0, ErrSyntax},
+
+		// Zeros
+		{"0", 0, nil},
+		{"0i", 0, nil},
+		{"-0.0i", 0, nil},
+		{"0+0.0i", 0, nil},
+		{"0e+0i", 0, nil},
+		{"0e-0+0i", 0, nil},
+		{"-0.0-0.0i", 0, nil},
+		{"0e+012345", 0, nil},
+		{"0x0p+012345i", 0, nil},
+		{"0x0.00p-012345i", 0, nil},
+		{"+0e-0+0e-0i", 0, nil},
+		{"0e+0+0e+0i", 0, nil},
+		{"-0e+0-0e+0i", 0, nil},
+
+		// Regular non-zeroes
+		{"0.1", 0.1, nil},
+		{"0.1i", 0 + 0.1i, nil},
+		{"0.123", 0.123, nil},
+		{"0.123i", 0 + 0.123i, nil},
+		{"0.123+0.123i", 0.123 + 0.123i, nil},
+		{"99", 99, nil},
+		{"+99", 99, nil},
+		{"-99", -99, nil},
+		{"+1i", 1i, nil},
+		{"-1i", -1i, nil},
+		{"+3+1i", 3 + 1i, nil},
+		{"30+3i", 30 + 3i, nil},
+		{"+3e+3-3e+3i", 3e+3 - 3e+3i, nil},
+		{"+3e+3+3e+3i", 3e+3 + 3e+3i, nil},
+		{"+3e+3+3e+3i+", 0, ErrSyntax},
+
+		// Separators
+		{"0.1", 0.1, nil},
+		{"0.1i", 0 + 0.1i, nil},
+		{"0.1_2_3", 0.123, nil},
+		{"+0x_3p3i", 0x3p3i, nil},
+		{"0_0+0x_0p0i", 0, nil},
+		{"0x_10.3p-8+0x3p3i", 0x10.3p-8 + 0x3p3i, nil},
+		{"+0x_1_0.3p-8+0x_3_0p3i", 0x10.3p-8 + 0x30p3i, nil},
+		{"0x1_0.3p+8-0x_3p3i", 0x10.3p+8 - 0x3p3i, nil},
+
+		// Hexadecimals
+		{"0x10.3p-8+0x3p3i", 0x10.3p-8 + 0x3p3i, nil},
+		{"+0x10.3p-8+0x3p3i", 0x10.3p-8 + 0x3p3i, nil},
+		{"0x10.3p+8-0x3p3i", 0x10.3p+8 - 0x3p3i, nil},
+		{"0x1p0", 1, nil},
+		{"0x1p1", 2, nil},
+		{"0x1p-1", 0.5, nil},
+		{"0x1ep-1", 15, nil},
+		{"-0x1ep-1", -15, nil},
+		{"-0x2p3", -16, nil},
+		{"0x1e2", 0, ErrSyntax},
+		{"1p2", 0, ErrSyntax},
+		{"0x1e2i", 0, ErrSyntax},
+
+		// ErrRange
+		// next float64 - too large
+		{"+0x1p1024", infp0, ErrRange},
+		{"-0x1p1024", infm0, ErrRange},
+		{"+0x1p1024i", inf0p, ErrRange},
+		{"-0x1p1024i", inf0m, ErrRange},
+		{"+0x1p1024+0x1p1024i", infpp, ErrRange},
+		{"+0x1p1024-0x1p1024i", infpm, ErrRange},
+		{"-0x1p1024+0x1p1024i", infmp, ErrRange},
+		{"-0x1p1024-0x1p1024i", infmm, ErrRange},
+		// the border is ...158079
+		// borderline - okay
+		{"+0x1.fffffffffffff7fffp1023+0x1.fffffffffffff7fffp1023i", 1.7976931348623157e+308 + 1.7976931348623157e+308i, nil},
+		{"+0x1.fffffffffffff7fffp1023-0x1.fffffffffffff7fffp1023i", 1.7976931348623157e+308 - 1.7976931348623157e+308i, nil},
+		{"-0x1.fffffffffffff7fffp1023+0x1.fffffffffffff7fffp1023i", -1.7976931348623157e+308 + 1.7976931348623157e+308i, nil},
+		{"-0x1.fffffffffffff7fffp1023-0x1.fffffffffffff7fffp1023i", -1.7976931348623157e+308 - 1.7976931348623157e+308i, nil},
+		// borderline - too large
+		{"+0x1.fffffffffffff8p1023", infp0, ErrRange},
+		{"-0x1fffffffffffff.8p+971", infm0, ErrRange},
+		{"+0x1.fffffffffffff8p1023i", inf0p, ErrRange},
+		{"-0x1fffffffffffff.8p+971i", inf0m, ErrRange},
+		{"+0x1.fffffffffffff8p1023+0x1.fffffffffffff8p1023i", infpp, ErrRange},
+		{"+0x1.fffffffffffff8p1023-0x1.fffffffffffff8p1023i", infpm, ErrRange},
+		{"-0x1fffffffffffff.8p+971+0x1fffffffffffff.8p+971i", infmp, ErrRange},
+		{"-0x1fffffffffffff8p+967-0x1fffffffffffff8p+967i", infmm, ErrRange},
+		// a little too large
+		{"1e308+1e308i", 1e+308 + 1e+308i, nil},
+		{"2e308+2e308i", infpp, ErrRange},
+		{"1e309+1e309i", infpp, ErrRange},
+		{"0x1p1025+0x1p1025i", infpp, ErrRange},
+		{"2e308", infp0, ErrRange},
+		{"1e309", infp0, ErrRange},
+		{"0x1p1025", infp0, ErrRange},
+		{"2e308i", inf0p, ErrRange},
+		{"1e309i", inf0p, ErrRange},
+		{"0x1p1025i", inf0p, ErrRange},
+		// way too large
+		{"+1e310+1e310i", infpp, ErrRange},
+		{"+1e310-1e310i", infpm, ErrRange},
+		{"-1e310+1e310i", infmp, ErrRange},
+		{"-1e310-1e310i", infmm, ErrRange},
+		// under/overflow exponent
+		{"1e-4294967296", 0, nil},
+		{"1e-4294967296i", 0, nil},
+		{"1e-4294967296+1i", 1i, nil},
+		{"1+1e-4294967296i", 1, nil},
+		{"1e-4294967296+1e-4294967296i", 0, nil},
+		{"1e+4294967296", infp0, ErrRange},
+		{"1e+4294967296i", inf0p, ErrRange},
+		{"1e+4294967296+1e+4294967296i", infpp, ErrRange},
+		{"1e+4294967296-1e+4294967296i", infpm, ErrRange},
+	}
+	for i := range tests {
+		test := &tests[i]
+		if test.err != nil {
+			test.err = &NumError{Func: "ParseComplex", Num: test.in, Err: test.err}
+		}
+		got, err := ParseComplex(test.in, 128)
+		if !reflect.DeepEqual(err, test.err) {
+			t.Fatalf("ParseComplex(%q, 128) = %v, %v; want %v, %v", test.in, got, err, test.out, test.err)
+		}
+		if !(cmplx.IsNaN(test.out) && cmplx.IsNaN(got)) && got != test.out {
+			t.Fatalf("ParseComplex(%q, 128) = %v, %v; want %v, %v", test.in, got, err, test.out, test.err)
+		}
+
+		if complex128(complex64(test.out)) == test.out {
+			got, err := ParseComplex(test.in, 64)
+			if !reflect.DeepEqual(err, test.err) {
+				t.Fatalf("ParseComplex(%q, 64) = %v, %v; want %v, %v", test.in, got, err, test.out, test.err)
+			}
+			got64 := complex64(got)
+			if complex128(got64) != test.out {
+				t.Fatalf("ParseComplex(%q, 64) = %v, %v; want %v, %v", test.in, got, err, test.out, test.err)
+			}
+		}
+	}
+}
+
+// Issue 42297: allow ParseComplex(s, not_32_or_64) for legacy reasons
+func TestParseComplexIncorrectBitSize(t *testing.T) {
+	const s = "1.5e308+1.0e307i"
+	const want = 1.5e308 + 1.0e307i
+
+	for _, bitSize := range []int{0, 10, 100, 256} {
+		c, err := ParseComplex(s, bitSize)
+		if err != nil {
+			t.Fatalf("ParseComplex(%q, %d) gave error %s", s, bitSize, err)
+		}
+		if c != want {
+			t.Fatalf("ParseComplex(%q, %d) = %g (expected %g)", s, bitSize, c, want)
+		}
+	}
+}
diff --git a/src/strconv/atof.go b/src/strconv/atof.go
new file mode 100644
index 0000000..8fc9042
--- /dev/null
+++ b/src/strconv/atof.go
@@ -0,0 +1,709 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv
+
+// decimal to binary floating point conversion.
+// Algorithm:
+//   1) Store input in multiprecision decimal.
+//   2) Multiply/divide decimal by powers of two until in range [0.5, 1)
+//   3) Multiply by 2^precision and round to get mantissa.
+
+import "math"
+
+var optimize = true // set to false to force slow-path conversions for testing
+
+// commonPrefixLenIgnoreCase returns the length of the common
+// prefix of s and prefix, with the character case of s ignored.
+// The prefix argument must be all lower-case.
+func commonPrefixLenIgnoreCase(s, prefix string) int {
+	n := len(prefix)
+	if n > len(s) {
+		n = len(s)
+	}
+	for i := 0; i < n; i++ {
+		c := s[i]
+		if 'A' <= c && c <= 'Z' {
+			c += 'a' - 'A'
+		}
+		if c != prefix[i] {
+			return i
+		}
+	}
+	return n
+}
+
+// special returns the floating-point value for the special,
+// possibly signed floating-point representations inf, infinity,
+// and NaN. The result is ok if a prefix of s contains one
+// of these representations and n is the length of that prefix.
+// The character case is ignored.
+func special(s string) (f float64, n int, ok bool) {
+	if len(s) == 0 {
+		return 0, 0, false
+	}
+	sign := 1
+	nsign := 0
+	switch s[0] {
+	case '+', '-':
+		if s[0] == '-' {
+			sign = -1
+		}
+		nsign = 1
+		s = s[1:]
+		fallthrough
+	case 'i', 'I':
+		n := commonPrefixLenIgnoreCase(s, "infinity")
+		// Anything longer than "inf" is ok, but if we
+		// don't have "infinity", only consume "inf".
+		if 3 < n && n < 8 {
+			n = 3
+		}
+		if n == 3 || n == 8 {
+			return math.Inf(sign), nsign + n, true
+		}
+	case 'n', 'N':
+		if commonPrefixLenIgnoreCase(s, "nan") == 3 {
+			return math.NaN(), 3, true
+		}
+	}
+	return 0, 0, false
+}
+
+func (b *decimal) set(s string) (ok bool) {
+	i := 0
+	b.neg = false
+	b.trunc = false
+
+	// optional sign
+	if i >= len(s) {
+		return
+	}
+	switch {
+	case s[i] == '+':
+		i++
+	case s[i] == '-':
+		b.neg = true
+		i++
+	}
+
+	// digits
+	sawdot := false
+	sawdigits := false
+	for ; i < len(s); i++ {
+		switch {
+		case s[i] == '_':
+			// readFloat already checked underscores
+			continue
+		case s[i] == '.':
+			if sawdot {
+				return
+			}
+			sawdot = true
+			b.dp = b.nd
+			continue
+
+		case '0' <= s[i] && s[i] <= '9':
+			sawdigits = true
+			if s[i] == '0' && b.nd == 0 { // ignore leading zeros
+				b.dp--
+				continue
+			}
+			if b.nd < len(b.d) {
+				b.d[b.nd] = s[i]
+				b.nd++
+			} else if s[i] != '0' {
+				b.trunc = true
+			}
+			continue
+		}
+		break
+	}
+	if !sawdigits {
+		return
+	}
+	if !sawdot {
+		b.dp = b.nd
+	}
+
+	// optional exponent moves decimal point.
+	// if we read a very large, very long number,
+	// just be sure to move the decimal point by
+	// a lot (say, 100000).  it doesn't matter if it's
+	// not the exact number.
+	if i < len(s) && lower(s[i]) == 'e' {
+		i++
+		if i >= len(s) {
+			return
+		}
+		esign := 1
+		if s[i] == '+' {
+			i++
+		} else if s[i] == '-' {
+			i++
+			esign = -1
+		}
+		if i >= len(s) || s[i] < '0' || s[i] > '9' {
+			return
+		}
+		e := 0
+		for ; i < len(s) && ('0' <= s[i] && s[i] <= '9' || s[i] == '_'); i++ {
+			if s[i] == '_' {
+				// readFloat already checked underscores
+				continue
+			}
+			if e < 10000 {
+				e = e*10 + int(s[i]) - '0'
+			}
+		}
+		b.dp += e * esign
+	}
+
+	if i != len(s) {
+		return
+	}
+
+	ok = true
+	return
+}
+
+// readFloat reads a decimal or hexadecimal mantissa and exponent from a float
+// string representation in s; the number may be followed by other characters.
+// readFloat reports the number of bytes consumed (i), and whether the number
+// is valid (ok).
+func readFloat(s string) (mantissa uint64, exp int, neg, trunc, hex bool, i int, ok bool) {
+	underscores := false
+
+	// optional sign
+	if i >= len(s) {
+		return
+	}
+	switch {
+	case s[i] == '+':
+		i++
+	case s[i] == '-':
+		neg = true
+		i++
+	}
+
+	// digits
+	base := uint64(10)
+	maxMantDigits := 19 // 10^19 fits in uint64
+	expChar := byte('e')
+	if i+2 < len(s) && s[i] == '0' && lower(s[i+1]) == 'x' {
+		base = 16
+		maxMantDigits = 16 // 16^16 fits in uint64
+		i += 2
+		expChar = 'p'
+		hex = true
+	}
+	sawdot := false
+	sawdigits := false
+	nd := 0
+	ndMant := 0
+	dp := 0
+loop:
+	for ; i < len(s); i++ {
+		switch c := s[i]; true {
+		case c == '_':
+			underscores = true
+			continue
+
+		case c == '.':
+			if sawdot {
+				break loop
+			}
+			sawdot = true
+			dp = nd
+			continue
+
+		case '0' <= c && c <= '9':
+			sawdigits = true
+			if c == '0' && nd == 0 { // ignore leading zeros
+				dp--
+				continue
+			}
+			nd++
+			if ndMant < maxMantDigits {
+				mantissa *= base
+				mantissa += uint64(c - '0')
+				ndMant++
+			} else if c != '0' {
+				trunc = true
+			}
+			continue
+
+		case base == 16 && 'a' <= lower(c) && lower(c) <= 'f':
+			sawdigits = true
+			nd++
+			if ndMant < maxMantDigits {
+				mantissa *= 16
+				mantissa += uint64(lower(c) - 'a' + 10)
+				ndMant++
+			} else {
+				trunc = true
+			}
+			continue
+		}
+		break
+	}
+	if !sawdigits {
+		return
+	}
+	if !sawdot {
+		dp = nd
+	}
+
+	if base == 16 {
+		dp *= 4
+		ndMant *= 4
+	}
+
+	// optional exponent moves decimal point.
+	// if we read a very large, very long number,
+	// just be sure to move the decimal point by
+	// a lot (say, 100000).  it doesn't matter if it's
+	// not the exact number.
+	if i < len(s) && lower(s[i]) == expChar {
+		i++
+		if i >= len(s) {
+			return
+		}
+		esign := 1
+		if s[i] == '+' {
+			i++
+		} else if s[i] == '-' {
+			i++
+			esign = -1
+		}
+		if i >= len(s) || s[i] < '0' || s[i] > '9' {
+			return
+		}
+		e := 0
+		for ; i < len(s) && ('0' <= s[i] && s[i] <= '9' || s[i] == '_'); i++ {
+			if s[i] == '_' {
+				underscores = true
+				continue
+			}
+			if e < 10000 {
+				e = e*10 + int(s[i]) - '0'
+			}
+		}
+		dp += e * esign
+	} else if base == 16 {
+		// Must have exponent.
+		return
+	}
+
+	if mantissa != 0 {
+		exp = dp - ndMant
+	}
+
+	if underscores && !underscoreOK(s[:i]) {
+		return
+	}
+
+	ok = true
+	return
+}
+
+// decimal power of ten to binary power of two.
+var powtab = []int{1, 3, 6, 9, 13, 16, 19, 23, 26}
+
+func (d *decimal) floatBits(flt *floatInfo) (b uint64, overflow bool) {
+	var exp int
+	var mant uint64
+
+	// Zero is always a special case.
+	if d.nd == 0 {
+		mant = 0
+		exp = flt.bias
+		goto out
+	}
+
+	// Obvious overflow/underflow.
+	// These bounds are for 64-bit floats.
+	// Will have to change if we want to support 80-bit floats in the future.
+	if d.dp > 310 {
+		goto overflow
+	}
+	if d.dp < -330 {
+		// zero
+		mant = 0
+		exp = flt.bias
+		goto out
+	}
+
+	// Scale by powers of two until in range [0.5, 1.0)
+	exp = 0
+	for d.dp > 0 {
+		var n int
+		if d.dp >= len(powtab) {
+			n = 27
+		} else {
+			n = powtab[d.dp]
+		}
+		d.Shift(-n)
+		exp += n
+	}
+	for d.dp < 0 || d.dp == 0 && d.d[0] < '5' {
+		var n int
+		if -d.dp >= len(powtab) {
+			n = 27
+		} else {
+			n = powtab[-d.dp]
+		}
+		d.Shift(n)
+		exp -= n
+	}
+
+	// Our range is [0.5,1) but floating point range is [1,2).
+	exp--
+
+	// Minimum representable exponent is flt.bias+1.
+	// If the exponent is smaller, move it up and
+	// adjust d accordingly.
+	if exp < flt.bias+1 {
+		n := flt.bias + 1 - exp
+		d.Shift(-n)
+		exp += n
+	}
+
+	if exp-flt.bias >= 1<<flt.expbits-1 {
+		goto overflow
+	}
+
+	// Extract 1+flt.mantbits bits.
+	d.Shift(int(1 + flt.mantbits))
+	mant = d.RoundedInteger()
+
+	// Rounding might have added a bit; shift down.
+	if mant == 2<<flt.mantbits {
+		mant >>= 1
+		exp++
+		if exp-flt.bias >= 1<<flt.expbits-1 {
+			goto overflow
+		}
+	}
+
+	// Denormalized?
+	if mant&(1<<flt.mantbits) == 0 {
+		exp = flt.bias
+	}
+	goto out
+
+overflow:
+	// ±Inf
+	mant = 0
+	exp = 1<<flt.expbits - 1 + flt.bias
+	overflow = true
+
+out:
+	// Assemble bits.
+	bits := mant & (uint64(1)<<flt.mantbits - 1)
+	bits |= uint64((exp-flt.bias)&(1<<flt.expbits-1)) << flt.mantbits
+	if d.neg {
+		bits |= 1 << flt.mantbits << flt.expbits
+	}
+	return bits, overflow
+}
+
+// Exact powers of 10.
+var float64pow10 = []float64{
+	1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9,
+	1e10, 1e11, 1e12, 1e13, 1e14, 1e15, 1e16, 1e17, 1e18, 1e19,
+	1e20, 1e21, 1e22,
+}
+var float32pow10 = []float32{1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9, 1e10}
+
+// If possible to convert decimal representation to 64-bit float f exactly,
+// entirely in floating-point math, do so, avoiding the expense of decimalToFloatBits.
+// Three common cases:
+//
+//	value is exact integer
+//	value is exact integer * exact power of ten
+//	value is exact integer / exact power of ten
+//
+// These all produce potentially inexact but correctly rounded answers.
+func atof64exact(mantissa uint64, exp int, neg bool) (f float64, ok bool) {
+	if mantissa>>float64info.mantbits != 0 {
+		return
+	}
+	f = float64(mantissa)
+	if neg {
+		f = -f
+	}
+	switch {
+	case exp == 0:
+		// an integer.
+		return f, true
+	// Exact integers are <= 10^15.
+	// Exact powers of ten are <= 10^22.
+	case exp > 0 && exp <= 15+22: // int * 10^k
+		// If exponent is big but number of digits is not,
+		// can move a few zeros into the integer part.
+		if exp > 22 {
+			f *= float64pow10[exp-22]
+			exp = 22
+		}
+		if f > 1e15 || f < -1e15 {
+			// the exponent was really too large.
+			return
+		}
+		return f * float64pow10[exp], true
+	case exp < 0 && exp >= -22: // int / 10^k
+		return f / float64pow10[-exp], true
+	}
+	return
+}
+
+// If possible to compute mantissa*10^exp to 32-bit float f exactly,
+// entirely in floating-point math, do so, avoiding the machinery above.
+func atof32exact(mantissa uint64, exp int, neg bool) (f float32, ok bool) {
+	if mantissa>>float32info.mantbits != 0 {
+		return
+	}
+	f = float32(mantissa)
+	if neg {
+		f = -f
+	}
+	switch {
+	case exp == 0:
+		return f, true
+	// Exact integers are <= 10^7.
+	// Exact powers of ten are <= 10^10.
+	case exp > 0 && exp <= 7+10: // int * 10^k
+		// If exponent is big but number of digits is not,
+		// can move a few zeros into the integer part.
+		if exp > 10 {
+			f *= float32pow10[exp-10]
+			exp = 10
+		}
+		if f > 1e7 || f < -1e7 {
+			// the exponent was really too large.
+			return
+		}
+		return f * float32pow10[exp], true
+	case exp < 0 && exp >= -10: // int / 10^k
+		return f / float32pow10[-exp], true
+	}
+	return
+}
+
+// atofHex converts the hex floating-point string s
+// to a rounded float32 or float64 value (depending on flt==&float32info or flt==&float64info)
+// and returns it as a float64.
+// The string s has already been parsed into a mantissa, exponent, and sign (neg==true for negative).
+// If trunc is true, trailing non-zero bits have been omitted from the mantissa.
+func atofHex(s string, flt *floatInfo, mantissa uint64, exp int, neg, trunc bool) (float64, error) {
+	maxExp := 1<<flt.expbits + flt.bias - 2
+	minExp := flt.bias + 1
+	exp += int(flt.mantbits) // mantissa now implicitly divided by 2^mantbits.
+
+	// Shift mantissa and exponent to bring representation into float range.
+	// Eventually we want a mantissa with a leading 1-bit followed by mantbits other bits.
+	// For rounding, we need two more, where the bottom bit represents
+	// whether that bit or any later bit was non-zero.
+	// (If the mantissa has already lost non-zero bits, trunc is true,
+	// and we OR in a 1 below after shifting left appropriately.)
+	for mantissa != 0 && mantissa>>(flt.mantbits+2) == 0 {
+		mantissa <<= 1
+		exp--
+	}
+	if trunc {
+		mantissa |= 1
+	}
+	for mantissa>>(1+flt.mantbits+2) != 0 {
+		mantissa = mantissa>>1 | mantissa&1
+		exp++
+	}
+
+	// If exponent is too negative,
+	// denormalize in hopes of making it representable.
+	// (The -2 is for the rounding bits.)
+	for mantissa > 1 && exp < minExp-2 {
+		mantissa = mantissa>>1 | mantissa&1
+		exp++
+	}
+
+	// Round using two bottom bits.
+	round := mantissa & 3
+	mantissa >>= 2
+	round |= mantissa & 1 // round to even (round up if mantissa is odd)
+	exp += 2
+	if round == 3 {
+		mantissa++
+		if mantissa == 1<<(1+flt.mantbits) {
+			mantissa >>= 1
+			exp++
+		}
+	}
+
+	if mantissa>>flt.mantbits == 0 { // Denormal or zero.
+		exp = flt.bias
+	}
+	var err error
+	if exp > maxExp { // infinity and range error
+		mantissa = 1 << flt.mantbits
+		exp = maxExp + 1
+		err = rangeError(fnParseFloat, s)
+	}
+
+	bits := mantissa & (1<<flt.mantbits - 1)
+	bits |= uint64((exp-flt.bias)&(1<<flt.expbits-1)) << flt.mantbits
+	if neg {
+		bits |= 1 << flt.mantbits << flt.expbits
+	}
+	if flt == &float32info {
+		return float64(math.Float32frombits(uint32(bits))), err
+	}
+	return math.Float64frombits(bits), err
+}
+
+const fnParseFloat = "ParseFloat"
+
+func atof32(s string) (f float32, n int, err error) {
+	if val, n, ok := special(s); ok {
+		return float32(val), n, nil
+	}
+
+	mantissa, exp, neg, trunc, hex, n, ok := readFloat(s)
+	if !ok {
+		return 0, n, syntaxError(fnParseFloat, s)
+	}
+
+	if hex {
+		f, err := atofHex(s[:n], &float32info, mantissa, exp, neg, trunc)
+		return float32(f), n, err
+	}
+
+	if optimize {
+		// Try pure floating-point arithmetic conversion, and if that fails,
+		// the Eisel-Lemire algorithm.
+		if !trunc {
+			if f, ok := atof32exact(mantissa, exp, neg); ok {
+				return f, n, nil
+			}
+		}
+		f, ok := eiselLemire32(mantissa, exp, neg)
+		if ok {
+			if !trunc {
+				return f, n, nil
+			}
+			// Even if the mantissa was truncated, we may
+			// have found the correct result. Confirm by
+			// converting the upper mantissa bound.
+			fUp, ok := eiselLemire32(mantissa+1, exp, neg)
+			if ok && f == fUp {
+				return f, n, nil
+			}
+		}
+	}
+
+	// Slow fallback.
+	var d decimal
+	if !d.set(s[:n]) {
+		return 0, n, syntaxError(fnParseFloat, s)
+	}
+	b, ovf := d.floatBits(&float32info)
+	f = math.Float32frombits(uint32(b))
+	if ovf {
+		err = rangeError(fnParseFloat, s)
+	}
+	return f, n, err
+}
+
+func atof64(s string) (f float64, n int, err error) {
+	if val, n, ok := special(s); ok {
+		return val, n, nil
+	}
+
+	mantissa, exp, neg, trunc, hex, n, ok := readFloat(s)
+	if !ok {
+		return 0, n, syntaxError(fnParseFloat, s)
+	}
+
+	if hex {
+		f, err := atofHex(s[:n], &float64info, mantissa, exp, neg, trunc)
+		return f, n, err
+	}
+
+	if optimize {
+		// Try pure floating-point arithmetic conversion, and if that fails,
+		// the Eisel-Lemire algorithm.
+		if !trunc {
+			if f, ok := atof64exact(mantissa, exp, neg); ok {
+				return f, n, nil
+			}
+		}
+		f, ok := eiselLemire64(mantissa, exp, neg)
+		if ok {
+			if !trunc {
+				return f, n, nil
+			}
+			// Even if the mantissa was truncated, we may
+			// have found the correct result. Confirm by
+			// converting the upper mantissa bound.
+			fUp, ok := eiselLemire64(mantissa+1, exp, neg)
+			if ok && f == fUp {
+				return f, n, nil
+			}
+		}
+	}
+
+	// Slow fallback.
+	var d decimal
+	if !d.set(s[:n]) {
+		return 0, n, syntaxError(fnParseFloat, s)
+	}
+	b, ovf := d.floatBits(&float64info)
+	f = math.Float64frombits(b)
+	if ovf {
+		err = rangeError(fnParseFloat, s)
+	}
+	return f, n, err
+}
+
+// ParseFloat converts the string s to a floating-point number
+// with the precision specified by bitSize: 32 for float32, or 64 for float64.
+// When bitSize=32, the result still has type float64, but it will be
+// convertible to float32 without changing its value.
+//
+// ParseFloat accepts decimal and hexadecimal floating-point numbers
+// as defined by the Go syntax for [floating-point literals].
+// If s is well-formed and near a valid floating-point number,
+// ParseFloat returns the nearest floating-point number rounded
+// using IEEE754 unbiased rounding.
+// (Parsing a hexadecimal floating-point value only rounds when
+// there are more bits in the hexadecimal representation than
+// will fit in the mantissa.)
+//
+// The errors that ParseFloat returns have concrete type *NumError
+// and include err.Num = s.
+//
+// If s is not syntactically well-formed, ParseFloat returns err.Err = ErrSyntax.
+//
+// If s is syntactically well-formed but is more than 1/2 ULP
+// away from the largest floating point number of the given size,
+// ParseFloat returns f = ±Inf, err.Err = ErrRange.
+//
+// ParseFloat recognizes the string "NaN", and the (possibly signed) strings "Inf" and "Infinity"
+// as their respective special floating point values. It ignores case when matching.
+//
+// [floating-point literals]: https://go.dev/ref/spec#Floating-point_literals
+func ParseFloat(s string, bitSize int) (float64, error) {
+	f, n, err := parseFloatPrefix(s, bitSize)
+	if n != len(s) && (err == nil || err.(*NumError).Err != ErrSyntax) {
+		return 0, syntaxError(fnParseFloat, s)
+	}
+	return f, err
+}
+
+func parseFloatPrefix(s string, bitSize int) (float64, int, error) {
+	if bitSize == 32 {
+		f, n, err := atof32(s)
+		return float64(f), n, err
+	}
+	return atof64(s)
+}
diff --git a/src/strconv/atof_test.go b/src/strconv/atof_test.go
new file mode 100644
index 0000000..7b287b4
--- /dev/null
+++ b/src/strconv/atof_test.go
@@ -0,0 +1,754 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv_test
+
+import (
+	"math"
+	"math/rand"
+	"reflect"
+	. "strconv"
+	"strings"
+	"sync"
+	"testing"
+)
+
+type atofTest struct {
+	in  string
+	out string
+	err error
+}
+
+var atoftests = []atofTest{
+	{"", "0", ErrSyntax},
+	{"1", "1", nil},
+	{"+1", "1", nil},
+	{"1x", "0", ErrSyntax},
+	{"1.1.", "0", ErrSyntax},
+	{"1e23", "1e+23", nil},
+	{"1E23", "1e+23", nil},
+	{"100000000000000000000000", "1e+23", nil},
+	{"1e-100", "1e-100", nil},
+	{"123456700", "1.234567e+08", nil},
+	{"99999999999999974834176", "9.999999999999997e+22", nil},
+	{"100000000000000000000001", "1.0000000000000001e+23", nil},
+	{"100000000000000008388608", "1.0000000000000001e+23", nil},
+	{"100000000000000016777215", "1.0000000000000001e+23", nil},
+	{"100000000000000016777216", "1.0000000000000003e+23", nil},
+	{"-1", "-1", nil},
+	{"-0.1", "-0.1", nil},
+	{"-0", "-0", nil},
+	{"1e-20", "1e-20", nil},
+	{"625e-3", "0.625", nil},
+
+	// Hexadecimal floating-point.
+	{"0x1p0", "1", nil},
+	{"0x1p1", "2", nil},
+	{"0x1p-1", "0.5", nil},
+	{"0x1ep-1", "15", nil},
+	{"-0x1ep-1", "-15", nil},
+	{"-0x1_ep-1", "-15", nil},
+	{"0x1p-200", "6.223015277861142e-61", nil},
+	{"0x1p200", "1.6069380442589903e+60", nil},
+	{"0x1fFe2.p0", "131042", nil},
+	{"0x1fFe2.P0", "131042", nil},
+	{"-0x2p3", "-16", nil},
+	{"0x0.fp4", "15", nil},
+	{"0x0.fp0", "0.9375", nil},
+	{"0x1e2", "0", ErrSyntax},
+	{"1p2", "0", ErrSyntax},
+
+	// zeros
+	{"0", "0", nil},
+	{"0e0", "0", nil},
+	{"-0e0", "-0", nil},
+	{"+0e0", "0", nil},
+	{"0e-0", "0", nil},
+	{"-0e-0", "-0", nil},
+	{"+0e-0", "0", nil},
+	{"0e+0", "0", nil},
+	{"-0e+0", "-0", nil},
+	{"+0e+0", "0", nil},
+	{"0e+01234567890123456789", "0", nil},
+	{"0.00e-01234567890123456789", "0", nil},
+	{"-0e+01234567890123456789", "-0", nil},
+	{"-0.00e-01234567890123456789", "-0", nil},
+	{"0x0p+01234567890123456789", "0", nil},
+	{"0x0.00p-01234567890123456789", "0", nil},
+	{"-0x0p+01234567890123456789", "-0", nil},
+	{"-0x0.00p-01234567890123456789", "-0", nil},
+
+	{"0e291", "0", nil}, // issue 15364
+	{"0e292", "0", nil}, // issue 15364
+	{"0e347", "0", nil}, // issue 15364
+	{"0e348", "0", nil}, // issue 15364
+	{"-0e291", "-0", nil},
+	{"-0e292", "-0", nil},
+	{"-0e347", "-0", nil},
+	{"-0e348", "-0", nil},
+	{"0x0p126", "0", nil},
+	{"0x0p127", "0", nil},
+	{"0x0p128", "0", nil},
+	{"0x0p129", "0", nil},
+	{"0x0p130", "0", nil},
+	{"0x0p1022", "0", nil},
+	{"0x0p1023", "0", nil},
+	{"0x0p1024", "0", nil},
+	{"0x0p1025", "0", nil},
+	{"0x0p1026", "0", nil},
+	{"-0x0p126", "-0", nil},
+	{"-0x0p127", "-0", nil},
+	{"-0x0p128", "-0", nil},
+	{"-0x0p129", "-0", nil},
+	{"-0x0p130", "-0", nil},
+	{"-0x0p1022", "-0", nil},
+	{"-0x0p1023", "-0", nil},
+	{"-0x0p1024", "-0", nil},
+	{"-0x0p1025", "-0", nil},
+	{"-0x0p1026", "-0", nil},
+
+	// NaNs
+	{"nan", "NaN", nil},
+	{"NaN", "NaN", nil},
+	{"NAN", "NaN", nil},
+
+	// Infs
+	{"inf", "+Inf", nil},
+	{"-Inf", "-Inf", nil},
+	{"+INF", "+Inf", nil},
+	{"-Infinity", "-Inf", nil},
+	{"+INFINITY", "+Inf", nil},
+	{"Infinity", "+Inf", nil},
+
+	// largest float64
+	{"1.7976931348623157e308", "1.7976931348623157e+308", nil},
+	{"-1.7976931348623157e308", "-1.7976931348623157e+308", nil},
+	{"0x1.fffffffffffffp1023", "1.7976931348623157e+308", nil},
+	{"-0x1.fffffffffffffp1023", "-1.7976931348623157e+308", nil},
+	{"0x1fffffffffffffp+971", "1.7976931348623157e+308", nil},
+	{"-0x1fffffffffffffp+971", "-1.7976931348623157e+308", nil},
+	{"0x.1fffffffffffffp1027", "1.7976931348623157e+308", nil},
+	{"-0x.1fffffffffffffp1027", "-1.7976931348623157e+308", nil},
+
+	// next float64 - too large
+	{"1.7976931348623159e308", "+Inf", ErrRange},
+	{"-1.7976931348623159e308", "-Inf", ErrRange},
+	{"0x1p1024", "+Inf", ErrRange},
+	{"-0x1p1024", "-Inf", ErrRange},
+	{"0x2p1023", "+Inf", ErrRange},
+	{"-0x2p1023", "-Inf", ErrRange},
+	{"0x.1p1028", "+Inf", ErrRange},
+	{"-0x.1p1028", "-Inf", ErrRange},
+	{"0x.2p1027", "+Inf", ErrRange},
+	{"-0x.2p1027", "-Inf", ErrRange},
+
+	// the border is ...158079
+	// borderline - okay
+	{"1.7976931348623158e308", "1.7976931348623157e+308", nil},
+	{"-1.7976931348623158e308", "-1.7976931348623157e+308", nil},
+	{"0x1.fffffffffffff7fffp1023", "1.7976931348623157e+308", nil},
+	{"-0x1.fffffffffffff7fffp1023", "-1.7976931348623157e+308", nil},
+	// borderline - too large
+	{"1.797693134862315808e308", "+Inf", ErrRange},
+	{"-1.797693134862315808e308", "-Inf", ErrRange},
+	{"0x1.fffffffffffff8p1023", "+Inf", ErrRange},
+	{"-0x1.fffffffffffff8p1023", "-Inf", ErrRange},
+	{"0x1fffffffffffff.8p+971", "+Inf", ErrRange},
+	{"-0x1fffffffffffff8p+967", "-Inf", ErrRange},
+	{"0x.1fffffffffffff8p1027", "+Inf", ErrRange},
+	{"-0x.1fffffffffffff9p1027", "-Inf", ErrRange},
+
+	// a little too large
+	{"1e308", "1e+308", nil},
+	{"2e308", "+Inf", ErrRange},
+	{"1e309", "+Inf", ErrRange},
+	{"0x1p1025", "+Inf", ErrRange},
+
+	// way too large
+	{"1e310", "+Inf", ErrRange},
+	{"-1e310", "-Inf", ErrRange},
+	{"1e400", "+Inf", ErrRange},
+	{"-1e400", "-Inf", ErrRange},
+	{"1e400000", "+Inf", ErrRange},
+	{"-1e400000", "-Inf", ErrRange},
+	{"0x1p1030", "+Inf", ErrRange},
+	{"0x1p2000", "+Inf", ErrRange},
+	{"0x1p2000000000", "+Inf", ErrRange},
+	{"-0x1p1030", "-Inf", ErrRange},
+	{"-0x1p2000", "-Inf", ErrRange},
+	{"-0x1p2000000000", "-Inf", ErrRange},
+
+	// denormalized
+	{"1e-305", "1e-305", nil},
+	{"1e-306", "1e-306", nil},
+	{"1e-307", "1e-307", nil},
+	{"1e-308", "1e-308", nil},
+	{"1e-309", "1e-309", nil},
+	{"1e-310", "1e-310", nil},
+	{"1e-322", "1e-322", nil},
+	// smallest denormal
+	{"5e-324", "5e-324", nil},
+	{"4e-324", "5e-324", nil},
+	{"3e-324", "5e-324", nil},
+	// too small
+	{"2e-324", "0", nil},
+	// way too small
+	{"1e-350", "0", nil},
+	{"1e-400000", "0", nil},
+
+	// Near denormals and denormals.
+	{"0x2.00000000000000p-1010", "1.8227805048890994e-304", nil}, // 0x00e0000000000000
+	{"0x1.fffffffffffff0p-1010", "1.8227805048890992e-304", nil}, // 0x00dfffffffffffff
+	{"0x1.fffffffffffff7p-1010", "1.8227805048890992e-304", nil}, // rounded down
+	{"0x1.fffffffffffff8p-1010", "1.8227805048890994e-304", nil}, // rounded up
+	{"0x1.fffffffffffff9p-1010", "1.8227805048890994e-304", nil}, // rounded up
+
+	{"0x2.00000000000000p-1022", "4.450147717014403e-308", nil},  // 0x0020000000000000
+	{"0x1.fffffffffffff0p-1022", "4.4501477170144023e-308", nil}, // 0x001fffffffffffff
+	{"0x1.fffffffffffff7p-1022", "4.4501477170144023e-308", nil}, // rounded down
+	{"0x1.fffffffffffff8p-1022", "4.450147717014403e-308", nil},  // rounded up
+	{"0x1.fffffffffffff9p-1022", "4.450147717014403e-308", nil},  // rounded up
+
+	{"0x1.00000000000000p-1022", "2.2250738585072014e-308", nil}, // 0x0010000000000000
+	{"0x0.fffffffffffff0p-1022", "2.225073858507201e-308", nil},  // 0x000fffffffffffff
+	{"0x0.ffffffffffffe0p-1022", "2.2250738585072004e-308", nil}, // 0x000ffffffffffffe
+	{"0x0.ffffffffffffe7p-1022", "2.2250738585072004e-308", nil}, // rounded down
+	{"0x1.ffffffffffffe8p-1023", "2.225073858507201e-308", nil},  // rounded up
+	{"0x1.ffffffffffffe9p-1023", "2.225073858507201e-308", nil},  // rounded up
+
+	{"0x0.00000003fffff0p-1022", "2.072261e-317", nil},  // 0x00000000003fffff
+	{"0x0.00000003456780p-1022", "1.694649e-317", nil},  // 0x0000000000345678
+	{"0x0.00000003456787p-1022", "1.694649e-317", nil},  // rounded down
+	{"0x0.00000003456788p-1022", "1.694649e-317", nil},  // rounded down (half to even)
+	{"0x0.00000003456790p-1022", "1.6946496e-317", nil}, // 0x0000000000345679
+	{"0x0.00000003456789p-1022", "1.6946496e-317", nil}, // rounded up
+
+	{"0x0.0000000345678800000000000000000000000001p-1022", "1.6946496e-317", nil}, // rounded up
+
+	{"0x0.000000000000f0p-1022", "7.4e-323", nil}, // 0x000000000000000f
+	{"0x0.00000000000060p-1022", "3e-323", nil},   // 0x0000000000000006
+	{"0x0.00000000000058p-1022", "3e-323", nil},   // rounded up
+	{"0x0.00000000000057p-1022", "2.5e-323", nil}, // rounded down
+	{"0x0.00000000000050p-1022", "2.5e-323", nil}, // 0x0000000000000005
+
+	{"0x0.00000000000010p-1022", "5e-324", nil},  // 0x0000000000000001
+	{"0x0.000000000000081p-1022", "5e-324", nil}, // rounded up
+	{"0x0.00000000000008p-1022", "0", nil},       // rounded down
+	{"0x0.00000000000007fp-1022", "0", nil},      // rounded down
+
+	// try to overflow exponent
+	{"1e-4294967296", "0", nil},
+	{"1e+4294967296", "+Inf", ErrRange},
+	{"1e-18446744073709551616", "0", nil},
+	{"1e+18446744073709551616", "+Inf", ErrRange},
+	{"0x1p-4294967296", "0", nil},
+	{"0x1p+4294967296", "+Inf", ErrRange},
+	{"0x1p-18446744073709551616", "0", nil},
+	{"0x1p+18446744073709551616", "+Inf", ErrRange},
+
+	// Parse errors
+	{"1e", "0", ErrSyntax},
+	{"1e-", "0", ErrSyntax},
+	{".e-1", "0", ErrSyntax},
+	{"1\x00.2", "0", ErrSyntax},
+	{"0x", "0", ErrSyntax},
+	{"0x.", "0", ErrSyntax},
+	{"0x1", "0", ErrSyntax},
+	{"0x.1", "0", ErrSyntax},
+	{"0x1p", "0", ErrSyntax},
+	{"0x.1p", "0", ErrSyntax},
+	{"0x1p+", "0", ErrSyntax},
+	{"0x.1p+", "0", ErrSyntax},
+	{"0x1p-", "0", ErrSyntax},
+	{"0x.1p-", "0", ErrSyntax},
+	{"0x1p+2", "4", nil},
+	{"0x.1p+2", "0.25", nil},
+	{"0x1p-2", "0.25", nil},
+	{"0x.1p-2", "0.015625", nil},
+
+	// https://www.exploringbinary.com/java-hangs-when-converting-2-2250738585072012e-308/
+	{"2.2250738585072012e-308", "2.2250738585072014e-308", nil},
+	// https://www.exploringbinary.com/php-hangs-on-numeric-value-2-2250738585072011e-308/
+	{"2.2250738585072011e-308", "2.225073858507201e-308", nil},
+
+	// A very large number (initially wrongly parsed by the fast algorithm).
+	{"4.630813248087435e+307", "4.630813248087435e+307", nil},
+
+	// A different kind of very large number.
+	{"22.222222222222222", "22.22222222222222", nil},
+	{"2." + strings.Repeat("2", 4000) + "e+1", "22.22222222222222", nil},
+	{"0x1.1111111111111p222", "7.18931911124017e+66", nil},
+	{"0x2.2222222222222p221", "7.18931911124017e+66", nil},
+	{"0x2." + strings.Repeat("2", 4000) + "p221", "7.18931911124017e+66", nil},
+
+	// Exactly halfway between 1 and math.Nextafter(1, 2).
+	// Round to even (down).
+	{"1.00000000000000011102230246251565404236316680908203125", "1", nil},
+	{"0x1.00000000000008p0", "1", nil},
+	// Slightly lower; still round down.
+	{"1.00000000000000011102230246251565404236316680908203124", "1", nil},
+	{"0x1.00000000000007Fp0", "1", nil},
+	// Slightly higher; round up.
+	{"1.00000000000000011102230246251565404236316680908203126", "1.0000000000000002", nil},
+	{"0x1.000000000000081p0", "1.0000000000000002", nil},
+	{"0x1.00000000000009p0", "1.0000000000000002", nil},
+	// Slightly higher, but you have to read all the way to the end.
+	{"1.00000000000000011102230246251565404236316680908203125" + strings.Repeat("0", 10000) + "1", "1.0000000000000002", nil},
+	{"0x1.00000000000008" + strings.Repeat("0", 10000) + "1p0", "1.0000000000000002", nil},
+
+	// Halfway between x := math.Nextafter(1, 2) and math.Nextafter(x, 2)
+	// Round to even (up).
+	{"1.00000000000000033306690738754696212708950042724609375", "1.0000000000000004", nil},
+	{"0x1.00000000000018p0", "1.0000000000000004", nil},
+
+	// Halfway between 1090544144181609278303144771584 and 1090544144181609419040633126912
+	// (15497564393479157p+46, should round to even 15497564393479156p+46, issue 36657)
+	{"1090544144181609348671888949248", "1.0905441441816093e+30", nil},
+	// slightly above, rounds up
+	{"1090544144181609348835077142190", "1.0905441441816094e+30", nil},
+
+	// Underscores.
+	{"1_23.50_0_0e+1_2", "1.235e+14", nil},
+	{"-_123.5e+12", "0", ErrSyntax},
+	{"+_123.5e+12", "0", ErrSyntax},
+	{"_123.5e+12", "0", ErrSyntax},
+	{"1__23.5e+12", "0", ErrSyntax},
+	{"123_.5e+12", "0", ErrSyntax},
+	{"123._5e+12", "0", ErrSyntax},
+	{"123.5_e+12", "0", ErrSyntax},
+	{"123.5__0e+12", "0", ErrSyntax},
+	{"123.5e_+12", "0", ErrSyntax},
+	{"123.5e+_12", "0", ErrSyntax},
+	{"123.5e_-12", "0", ErrSyntax},
+	{"123.5e-_12", "0", ErrSyntax},
+	{"123.5e+1__2", "0", ErrSyntax},
+	{"123.5e+12_", "0", ErrSyntax},
+
+	{"0x_1_2.3_4_5p+1_2", "74565", nil},
+	{"-_0x12.345p+12", "0", ErrSyntax},
+	{"+_0x12.345p+12", "0", ErrSyntax},
+	{"_0x12.345p+12", "0", ErrSyntax},
+	{"0x__12.345p+12", "0", ErrSyntax},
+	{"0x1__2.345p+12", "0", ErrSyntax},
+	{"0x12_.345p+12", "0", ErrSyntax},
+	{"0x12._345p+12", "0", ErrSyntax},
+	{"0x12.3__45p+12", "0", ErrSyntax},
+	{"0x12.345_p+12", "0", ErrSyntax},
+	{"0x12.345p_+12", "0", ErrSyntax},
+	{"0x12.345p+_12", "0", ErrSyntax},
+	{"0x12.345p_-12", "0", ErrSyntax},
+	{"0x12.345p-_12", "0", ErrSyntax},
+	{"0x12.345p+1__2", "0", ErrSyntax},
+	{"0x12.345p+12_", "0", ErrSyntax},
+
+	{"1e100x", "0", ErrSyntax},
+	{"1e1000x", "0", ErrSyntax},
+}
+
+var atof32tests = []atofTest{
+	// Hex
+	{"0x1p-100", "7.888609e-31", nil},
+	{"0x1p100", "1.2676506e+30", nil},
+
+	// Exactly halfway between 1 and the next float32.
+	// Round to even (down).
+	{"1.000000059604644775390625", "1", nil},
+	{"0x1.000001p0", "1", nil},
+	// Slightly lower.
+	{"1.000000059604644775390624", "1", nil},
+	{"0x1.0000008p0", "1", nil},
+	{"0x1.000000fp0", "1", nil},
+	// Slightly higher.
+	{"1.000000059604644775390626", "1.0000001", nil},
+	{"0x1.000002p0", "1.0000001", nil},
+	{"0x1.0000018p0", "1.0000001", nil},
+	{"0x1.0000011p0", "1.0000001", nil},
+	// Slightly higher, but you have to read all the way to the end.
+	{"1.000000059604644775390625" + strings.Repeat("0", 10000) + "1", "1.0000001", nil},
+	{"0x1.000001" + strings.Repeat("0", 10000) + "1p0", "1.0000001", nil},
+
+	// largest float32: (1<<128) * (1 - 2^-24)
+	{"340282346638528859811704183484516925440", "3.4028235e+38", nil},
+	{"-340282346638528859811704183484516925440", "-3.4028235e+38", nil},
+	{"0x.ffffffp128", "3.4028235e+38", nil},
+	{"-340282346638528859811704183484516925440", "-3.4028235e+38", nil},
+	{"-0x.ffffffp128", "-3.4028235e+38", nil},
+	// next float32 - too large
+	{"3.4028236e38", "+Inf", ErrRange},
+	{"-3.4028236e38", "-Inf", ErrRange},
+	{"0x1.0p128", "+Inf", ErrRange},
+	{"-0x1.0p128", "-Inf", ErrRange},
+	// the border is 3.40282356779...e+38
+	// borderline - okay
+	{"3.402823567e38", "3.4028235e+38", nil},
+	{"-3.402823567e38", "-3.4028235e+38", nil},
+	{"0x.ffffff7fp128", "3.4028235e+38", nil},
+	{"-0x.ffffff7fp128", "-3.4028235e+38", nil},
+	// borderline - too large
+	{"3.4028235678e38", "+Inf", ErrRange},
+	{"-3.4028235678e38", "-Inf", ErrRange},
+	{"0x.ffffff8p128", "+Inf", ErrRange},
+	{"-0x.ffffff8p128", "-Inf", ErrRange},
+
+	// Denormals: less than 2^-126
+	{"1e-38", "1e-38", nil},
+	{"1e-39", "1e-39", nil},
+	{"1e-40", "1e-40", nil},
+	{"1e-41", "1e-41", nil},
+	{"1e-42", "1e-42", nil},
+	{"1e-43", "1e-43", nil},
+	{"1e-44", "1e-44", nil},
+	{"6e-45", "6e-45", nil}, // 4p-149 = 5.6e-45
+	{"5e-45", "6e-45", nil},
+
+	// Smallest denormal
+	{"1e-45", "1e-45", nil}, // 1p-149 = 1.4e-45
+	{"2e-45", "1e-45", nil},
+	{"3e-45", "3e-45", nil},
+
+	// Near denormals and denormals.
+	{"0x0.89aBcDp-125", "1.2643093e-38", nil},  // 0x0089abcd
+	{"0x0.8000000p-125", "1.1754944e-38", nil}, // 0x00800000
+	{"0x0.1234560p-125", "1.671814e-39", nil},  // 0x00123456
+	{"0x0.1234567p-125", "1.671814e-39", nil},  // rounded down
+	{"0x0.1234568p-125", "1.671814e-39", nil},  // rounded down
+	{"0x0.1234569p-125", "1.671815e-39", nil},  // rounded up
+	{"0x0.1234570p-125", "1.671815e-39", nil},  // 0x00123457
+	{"0x0.0000010p-125", "1e-45", nil},         // 0x00000001
+	{"0x0.00000081p-125", "1e-45", nil},        // rounded up
+	{"0x0.0000008p-125", "0", nil},             // rounded down
+	{"0x0.0000007p-125", "0", nil},             // rounded down
+
+	// 2^92 = 8388608p+69 = 4951760157141521099596496896 (4.9517602e27)
+	// is an exact power of two that needs 8 decimal digits to be correctly
+	// parsed back.
+	// The float32 before is 16777215p+68 = 4.95175986e+27
+	// The halfway is 4.951760009. A bad algorithm that thinks the previous
+	// float32 is 8388607p+69 will shorten incorrectly to 4.95176e+27.
+	{"4951760157141521099596496896", "4.9517602e+27", nil},
+}
+
+type atofSimpleTest struct {
+	x float64
+	s string
+}
+
+var (
+	atofOnce               sync.Once
+	atofRandomTests        []atofSimpleTest
+	benchmarksRandomBits   [1024]string
+	benchmarksRandomNormal [1024]string
+)
+
+func initAtof() {
+	atofOnce.Do(initAtofOnce)
+}
+
+func initAtofOnce() {
+	// The atof routines return NumErrors wrapping
+	// the error and the string. Convert the table above.
+	for i := range atoftests {
+		test := &atoftests[i]
+		if test.err != nil {
+			test.err = &NumError{"ParseFloat", test.in, test.err}
+		}
+	}
+	for i := range atof32tests {
+		test := &atof32tests[i]
+		if test.err != nil {
+			test.err = &NumError{"ParseFloat", test.in, test.err}
+		}
+	}
+
+	// Generate random inputs for tests and benchmarks
+	if testing.Short() {
+		atofRandomTests = make([]atofSimpleTest, 100)
+	} else {
+		atofRandomTests = make([]atofSimpleTest, 10000)
+	}
+	for i := range atofRandomTests {
+		n := uint64(rand.Uint32())<<32 | uint64(rand.Uint32())
+		x := math.Float64frombits(n)
+		s := FormatFloat(x, 'g', -1, 64)
+		atofRandomTests[i] = atofSimpleTest{x, s}
+	}
+
+	for i := range benchmarksRandomBits {
+		bits := uint64(rand.Uint32())<<32 | uint64(rand.Uint32())
+		x := math.Float64frombits(bits)
+		benchmarksRandomBits[i] = FormatFloat(x, 'g', -1, 64)
+	}
+
+	for i := range benchmarksRandomNormal {
+		x := rand.NormFloat64()
+		benchmarksRandomNormal[i] = FormatFloat(x, 'g', -1, 64)
+	}
+}
+
+func TestParseFloatPrefix(t *testing.T) {
+	for i := range atoftests {
+		test := &atoftests[i]
+		if test.err != nil {
+			continue
+		}
+		// Adding characters that do not extend a number should not invalidate it.
+		// Test a few. The "i" and "init" cases test that we accept "infi", "infinit"
+		// correctly as "inf" with suffix.
+		for _, suffix := range []string{" ", "q", "+", "-", "<", "=", ">", "(", ")", "i", "init"} {
+			in := test.in + suffix
+			_, n, err := ParseFloatPrefix(in, 64)
+			if err != nil {
+				t.Errorf("ParseFloatPrefix(%q, 64): err = %v; want no error", in, err)
+			}
+			if n != len(test.in) {
+				t.Errorf("ParseFloatPrefix(%q, 64): n = %d; want %d", in, n, len(test.in))
+			}
+		}
+	}
+}
+
+func testAtof(t *testing.T, opt bool) {
+	initAtof()
+	oldopt := SetOptimize(opt)
+	for i := 0; i < len(atoftests); i++ {
+		test := &atoftests[i]
+		out, err := ParseFloat(test.in, 64)
+		outs := FormatFloat(out, 'g', -1, 64)
+		if outs != test.out || !reflect.DeepEqual(err, test.err) {
+			t.Errorf("ParseFloat(%v, 64) = %v, %v want %v, %v",
+				test.in, out, err, test.out, test.err)
+		}
+
+		if float64(float32(out)) == out {
+			out, err := ParseFloat(test.in, 32)
+			out32 := float32(out)
+			if float64(out32) != out {
+				t.Errorf("ParseFloat(%v, 32) = %v, not a float32 (closest is %v)", test.in, out, float64(out32))
+				continue
+			}
+			outs := FormatFloat(float64(out32), 'g', -1, 32)
+			if outs != test.out || !reflect.DeepEqual(err, test.err) {
+				t.Errorf("ParseFloat(%v, 32) = %v, %v want %v, %v  # %v",
+					test.in, out32, err, test.out, test.err, out)
+			}
+		}
+	}
+	for _, test := range atof32tests {
+		out, err := ParseFloat(test.in, 32)
+		out32 := float32(out)
+		if float64(out32) != out {
+			t.Errorf("ParseFloat(%v, 32) = %v, not a float32 (closest is %v)", test.in, out, float64(out32))
+			continue
+		}
+		outs := FormatFloat(float64(out32), 'g', -1, 32)
+		if outs != test.out || !reflect.DeepEqual(err, test.err) {
+			t.Errorf("ParseFloat(%v, 32) = %v, %v want %v, %v  # %v",
+				test.in, out32, err, test.out, test.err, out)
+		}
+	}
+	SetOptimize(oldopt)
+}
+
+func TestAtof(t *testing.T) { testAtof(t, true) }
+
+func TestAtofSlow(t *testing.T) { testAtof(t, false) }
+
+func TestAtofRandom(t *testing.T) {
+	initAtof()
+	for _, test := range atofRandomTests {
+		x, _ := ParseFloat(test.s, 64)
+		switch {
+		default:
+			t.Errorf("number %s badly parsed as %b (expected %b)", test.s, x, test.x)
+		case x == test.x:
+		case math.IsNaN(test.x) && math.IsNaN(x):
+		}
+	}
+	t.Logf("tested %d random numbers", len(atofRandomTests))
+}
+
+var roundTripCases = []struct {
+	f float64
+	s string
+}{
+	// Issue 2917.
+	// This test will break the optimized conversion if the
+	// FPU is using 80-bit registers instead of 64-bit registers,
+	// usually because the operating system initialized the
+	// thread with 80-bit precision and the Go runtime didn't
+	// fix the FP control word.
+	{8865794286000691 << 39, "4.87402195346389e+27"},
+	{8865794286000692 << 39, "4.8740219534638903e+27"},
+}
+
+func TestRoundTrip(t *testing.T) {
+	for _, tt := range roundTripCases {
+		old := SetOptimize(false)
+		s := FormatFloat(tt.f, 'g', -1, 64)
+		if s != tt.s {
+			t.Errorf("no-opt FormatFloat(%b) = %s, want %s", tt.f, s, tt.s)
+		}
+		f, err := ParseFloat(tt.s, 64)
+		if f != tt.f || err != nil {
+			t.Errorf("no-opt ParseFloat(%s) = %b, %v want %b, nil", tt.s, f, err, tt.f)
+		}
+		SetOptimize(true)
+		s = FormatFloat(tt.f, 'g', -1, 64)
+		if s != tt.s {
+			t.Errorf("opt FormatFloat(%b) = %s, want %s", tt.f, s, tt.s)
+		}
+		f, err = ParseFloat(tt.s, 64)
+		if f != tt.f || err != nil {
+			t.Errorf("opt ParseFloat(%s) = %b, %v want %b, nil", tt.s, f, err, tt.f)
+		}
+		SetOptimize(old)
+	}
+}
+
+// TestRoundTrip32 tries a fraction of all finite positive float32 values.
+func TestRoundTrip32(t *testing.T) {
+	step := uint32(997)
+	if testing.Short() {
+		step = 99991
+	}
+	count := 0
+	for i := uint32(0); i < 0xff<<23; i += step {
+		f := math.Float32frombits(i)
+		if i&1 == 1 {
+			f = -f // negative
+		}
+		s := FormatFloat(float64(f), 'g', -1, 32)
+
+		parsed, err := ParseFloat(s, 32)
+		parsed32 := float32(parsed)
+		switch {
+		case err != nil:
+			t.Errorf("ParseFloat(%q, 32) gave error %s", s, err)
+		case float64(parsed32) != parsed:
+			t.Errorf("ParseFloat(%q, 32) = %v, not a float32 (nearest is %v)", s, parsed, parsed32)
+		case parsed32 != f:
+			t.Errorf("ParseFloat(%q, 32) = %b (expected %b)", s, parsed32, f)
+		}
+		count++
+	}
+	t.Logf("tested %d float32's", count)
+}
+
+// Issue 42297: a lot of code in the wild accidentally calls ParseFloat(s, 10)
+// or ParseFloat(s, 0), so allow bitSize values other than 32 and 64.
+func TestParseFloatIncorrectBitSize(t *testing.T) {
+	const s = "1.5e308"
+	const want = 1.5e308
+
+	for _, bitSize := range []int{0, 10, 100, 128} {
+		f, err := ParseFloat(s, bitSize)
+		if err != nil {
+			t.Fatalf("ParseFloat(%q, %d) gave error %s", s, bitSize, err)
+		}
+		if f != want {
+			t.Fatalf("ParseFloat(%q, %d) = %g (expected %g)", s, bitSize, f, want)
+		}
+	}
+}
+
+func BenchmarkAtof64Decimal(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		ParseFloat("33909", 64)
+	}
+}
+
+func BenchmarkAtof64Float(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		ParseFloat("339.7784", 64)
+	}
+}
+
+func BenchmarkAtof64FloatExp(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		ParseFloat("-5.09e75", 64)
+	}
+}
+
+func BenchmarkAtof64Big(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		ParseFloat("123456789123456789123456789", 64)
+	}
+}
+
+func BenchmarkAtof64RandomBits(b *testing.B) {
+	initAtof()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		ParseFloat(benchmarksRandomBits[i%1024], 64)
+	}
+}
+
+func BenchmarkAtof64RandomFloats(b *testing.B) {
+	initAtof()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		ParseFloat(benchmarksRandomNormal[i%1024], 64)
+	}
+}
+
+func BenchmarkAtof64RandomLongFloats(b *testing.B) {
+	initAtof()
+	samples := make([]string, len(atofRandomTests))
+	for i, t := range atofRandomTests {
+		samples[i] = FormatFloat(t.x, 'g', 20, 64)
+	}
+	b.ResetTimer()
+	idx := 0
+	for i := 0; i < b.N; i++ {
+		ParseFloat(samples[idx], 64)
+		idx++
+		if idx == len(samples) {
+			idx = 0
+		}
+	}
+}
+
+func BenchmarkAtof32Decimal(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		ParseFloat("33909", 32)
+	}
+}
+
+func BenchmarkAtof32Float(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		ParseFloat("339.778", 32)
+	}
+}
+
+func BenchmarkAtof32FloatExp(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		ParseFloat("12.3456e32", 32)
+	}
+}
+
+func BenchmarkAtof32Random(b *testing.B) {
+	n := uint32(997)
+	var float32strings [4096]string
+	for i := range float32strings {
+		n = (99991*n + 42) % (0xff << 23)
+		float32strings[i] = FormatFloat(float64(math.Float32frombits(n)), 'g', -1, 32)
+	}
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		ParseFloat(float32strings[i%4096], 32)
+	}
+}
+
+func BenchmarkAtof32RandomLong(b *testing.B) {
+	n := uint32(997)
+	var float32strings [4096]string
+	for i := range float32strings {
+		n = (99991*n + 42) % (0xff << 23)
+		float32strings[i] = FormatFloat(float64(math.Float32frombits(n)), 'g', 20, 32)
+	}
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		ParseFloat(float32strings[i%4096], 32)
+	}
+}
diff --git a/src/strconv/atoi.go b/src/strconv/atoi.go
new file mode 100644
index 0000000..520d826
--- /dev/null
+++ b/src/strconv/atoi.go
@@ -0,0 +1,332 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv
+
+import "errors"
+
+// lower(c) is a lower-case letter if and only if
+// c is either that lower-case letter or the equivalent upper-case letter.
+// Instead of writing c == 'x' || c == 'X' one can write lower(c) == 'x'.
+// Note that lower of non-letters can produce other non-letters.
+func lower(c byte) byte {
+	return c | ('x' - 'X')
+}
+
+// ErrRange indicates that a value is out of range for the target type.
+var ErrRange = errors.New("value out of range")
+
+// ErrSyntax indicates that a value does not have the right syntax for the target type.
+var ErrSyntax = errors.New("invalid syntax")
+
+// A NumError records a failed conversion.
+type NumError struct {
+	Func string // the failing function (ParseBool, ParseInt, ParseUint, ParseFloat, ParseComplex)
+	Num  string // the input
+	Err  error  // the reason the conversion failed (e.g. ErrRange, ErrSyntax, etc.)
+}
+
+func (e *NumError) Error() string {
+	return "strconv." + e.Func + ": " + "parsing " + Quote(e.Num) + ": " + e.Err.Error()
+}
+
+func (e *NumError) Unwrap() error { return e.Err }
+
+// cloneString returns a string copy of x.
+//
+// All ParseXXX functions allow the input string to escape to the error value.
+// This hurts strconv.ParseXXX(string(b)) calls where b is []byte since
+// the conversion from []byte must allocate a string on the heap.
+// If we assume errors are infrequent, then we can avoid escaping the input
+// back to the output by copying it first. This allows the compiler to call
+// strconv.ParseXXX without a heap allocation for most []byte to string
+// conversions, since it can now prove that the string cannot escape Parse.
+//
+// TODO: Use strings.Clone instead? However, we cannot depend on "strings"
+// since it incurs a transitive dependency on "unicode".
+// Either move strings.Clone to an internal/bytealg or make the
+// "strings" to "unicode" dependency lighter (see https://go.dev/issue/54098).
+func cloneString(x string) string { return string([]byte(x)) }
+
+func syntaxError(fn, str string) *NumError {
+	return &NumError{fn, cloneString(str), ErrSyntax}
+}
+
+func rangeError(fn, str string) *NumError {
+	return &NumError{fn, cloneString(str), ErrRange}
+}
+
+func baseError(fn, str string, base int) *NumError {
+	return &NumError{fn, cloneString(str), errors.New("invalid base " + Itoa(base))}
+}
+
+func bitSizeError(fn, str string, bitSize int) *NumError {
+	return &NumError{fn, cloneString(str), errors.New("invalid bit size " + Itoa(bitSize))}
+}
+
+const intSize = 32 << (^uint(0) >> 63)
+
+// IntSize is the size in bits of an int or uint value.
+const IntSize = intSize
+
+const maxUint64 = 1<<64 - 1
+
+// ParseUint is like ParseInt but for unsigned numbers.
+//
+// A sign prefix is not permitted.
+func ParseUint(s string, base int, bitSize int) (uint64, error) {
+	const fnParseUint = "ParseUint"
+
+	if s == "" {
+		return 0, syntaxError(fnParseUint, s)
+	}
+
+	base0 := base == 0
+
+	s0 := s
+	switch {
+	case 2 <= base && base <= 36:
+		// valid base; nothing to do
+
+	case base == 0:
+		// Look for octal, hex prefix.
+		base = 10
+		if s[0] == '0' {
+			switch {
+			case len(s) >= 3 && lower(s[1]) == 'b':
+				base = 2
+				s = s[2:]
+			case len(s) >= 3 && lower(s[1]) == 'o':
+				base = 8
+				s = s[2:]
+			case len(s) >= 3 && lower(s[1]) == 'x':
+				base = 16
+				s = s[2:]
+			default:
+				base = 8
+				s = s[1:]
+			}
+		}
+
+	default:
+		return 0, baseError(fnParseUint, s0, base)
+	}
+
+	if bitSize == 0 {
+		bitSize = IntSize
+	} else if bitSize < 0 || bitSize > 64 {
+		return 0, bitSizeError(fnParseUint, s0, bitSize)
+	}
+
+	// Cutoff is the smallest number such that cutoff*base > maxUint64.
+	// Use compile-time constants for common cases.
+	var cutoff uint64
+	switch base {
+	case 10:
+		cutoff = maxUint64/10 + 1
+	case 16:
+		cutoff = maxUint64/16 + 1
+	default:
+		cutoff = maxUint64/uint64(base) + 1
+	}
+
+	maxVal := uint64(1)<<uint(bitSize) - 1
+
+	underscores := false
+	var n uint64
+	for _, c := range []byte(s) {
+		var d byte
+		switch {
+		case c == '_' && base0:
+			underscores = true
+			continue
+		case '0' <= c && c <= '9':
+			d = c - '0'
+		case 'a' <= lower(c) && lower(c) <= 'z':
+			d = lower(c) - 'a' + 10
+		default:
+			return 0, syntaxError(fnParseUint, s0)
+		}
+
+		if d >= byte(base) {
+			return 0, syntaxError(fnParseUint, s0)
+		}
+
+		if n >= cutoff {
+			// n*base overflows
+			return maxVal, rangeError(fnParseUint, s0)
+		}
+		n *= uint64(base)
+
+		n1 := n + uint64(d)
+		if n1 < n || n1 > maxVal {
+			// n+d overflows
+			return maxVal, rangeError(fnParseUint, s0)
+		}
+		n = n1
+	}
+
+	if underscores && !underscoreOK(s0) {
+		return 0, syntaxError(fnParseUint, s0)
+	}
+
+	return n, nil
+}
+
+// ParseInt interprets a string s in the given base (0, 2 to 36) and
+// bit size (0 to 64) and returns the corresponding value i.
+//
+// The string may begin with a leading sign: "+" or "-".
+//
+// If the base argument is 0, the true base is implied by the string's
+// prefix following the sign (if present): 2 for "0b", 8 for "0" or "0o",
+// 16 for "0x", and 10 otherwise. Also, for argument base 0 only,
+// underscore characters are permitted as defined by the Go syntax for
+// [integer literals].
+//
+// The bitSize argument specifies the integer type
+// that the result must fit into. Bit sizes 0, 8, 16, 32, and 64
+// correspond to int, int8, int16, int32, and int64.
+// If bitSize is below 0 or above 64, an error is returned.
+//
+// The errors that ParseInt returns have concrete type *NumError
+// and include err.Num = s. If s is empty or contains invalid
+// digits, err.Err = ErrSyntax and the returned value is 0;
+// if the value corresponding to s cannot be represented by a
+// signed integer of the given size, err.Err = ErrRange and the
+// returned value is the maximum magnitude integer of the
+// appropriate bitSize and sign.
+//
+// [integer literals]: https://go.dev/ref/spec#Integer_literals
+func ParseInt(s string, base int, bitSize int) (i int64, err error) {
+	const fnParseInt = "ParseInt"
+
+	if s == "" {
+		return 0, syntaxError(fnParseInt, s)
+	}
+
+	// Pick off leading sign.
+	s0 := s
+	neg := false
+	if s[0] == '+' {
+		s = s[1:]
+	} else if s[0] == '-' {
+		neg = true
+		s = s[1:]
+	}
+
+	// Convert unsigned and check range.
+	var un uint64
+	un, err = ParseUint(s, base, bitSize)
+	if err != nil && err.(*NumError).Err != ErrRange {
+		err.(*NumError).Func = fnParseInt
+		err.(*NumError).Num = cloneString(s0)
+		return 0, err
+	}
+
+	if bitSize == 0 {
+		bitSize = IntSize
+	}
+
+	cutoff := uint64(1 << uint(bitSize-1))
+	if !neg && un >= cutoff {
+		return int64(cutoff - 1), rangeError(fnParseInt, s0)
+	}
+	if neg && un > cutoff {
+		return -int64(cutoff), rangeError(fnParseInt, s0)
+	}
+	n := int64(un)
+	if neg {
+		n = -n
+	}
+	return n, nil
+}
+
+// Atoi is equivalent to ParseInt(s, 10, 0), converted to type int.
+func Atoi(s string) (int, error) {
+	const fnAtoi = "Atoi"
+
+	sLen := len(s)
+	if intSize == 32 && (0 < sLen && sLen < 10) ||
+		intSize == 64 && (0 < sLen && sLen < 19) {
+		// Fast path for small integers that fit int type.
+		s0 := s
+		if s[0] == '-' || s[0] == '+' {
+			s = s[1:]
+			if len(s) < 1 {
+				return 0, syntaxError(fnAtoi, s0)
+			}
+		}
+
+		n := 0
+		for _, ch := range []byte(s) {
+			ch -= '0'
+			if ch > 9 {
+				return 0, syntaxError(fnAtoi, s0)
+			}
+			n = n*10 + int(ch)
+		}
+		if s0[0] == '-' {
+			n = -n
+		}
+		return n, nil
+	}
+
+	// Slow path for invalid, big, or underscored integers.
+	i64, err := ParseInt(s, 10, 0)
+	if nerr, ok := err.(*NumError); ok {
+		nerr.Func = fnAtoi
+	}
+	return int(i64), err
+}
+
+// underscoreOK reports whether the underscores in s are allowed.
+// Checking them in this one function lets all the parsers skip over them simply.
+// Underscore must appear only between digits or between a base prefix and a digit.
+func underscoreOK(s string) bool {
+	// saw tracks the last character (class) we saw:
+	// ^ for beginning of number,
+	// 0 for a digit or base prefix,
+	// _ for an underscore,
+	// ! for none of the above.
+	saw := '^'
+	i := 0
+
+	// Optional sign.
+	if len(s) >= 1 && (s[0] == '-' || s[0] == '+') {
+		s = s[1:]
+	}
+
+	// Optional base prefix.
+	hex := false
+	if len(s) >= 2 && s[0] == '0' && (lower(s[1]) == 'b' || lower(s[1]) == 'o' || lower(s[1]) == 'x') {
+		i = 2
+		saw = '0' // base prefix counts as a digit for "underscore as digit separator"
+		hex = lower(s[1]) == 'x'
+	}
+
+	// Number proper.
+	for ; i < len(s); i++ {
+		// Digits are always okay.
+		if '0' <= s[i] && s[i] <= '9' || hex && 'a' <= lower(s[i]) && lower(s[i]) <= 'f' {
+			saw = '0'
+			continue
+		}
+		// Underscore must follow digit.
+		if s[i] == '_' {
+			if saw != '0' {
+				return false
+			}
+			saw = '_'
+			continue
+		}
+		// Underscore must also be followed by digit.
+		if saw == '_' {
+			return false
+		}
+		// Saw non-digit, non-underscore.
+		saw = '!'
+	}
+	return saw != '_'
+}
diff --git a/src/strconv/atoi_test.go b/src/strconv/atoi_test.go
new file mode 100644
index 0000000..d7f8f25
--- /dev/null
+++ b/src/strconv/atoi_test.go
@@ -0,0 +1,677 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv_test
+
+import (
+	"errors"
+	"fmt"
+	"reflect"
+	. "strconv"
+	"testing"
+)
+
+type parseUint64Test struct {
+	in  string
+	out uint64
+	err error
+}
+
+var parseUint64Tests = []parseUint64Test{
+	{"", 0, ErrSyntax},
+	{"0", 0, nil},
+	{"1", 1, nil},
+	{"12345", 12345, nil},
+	{"012345", 12345, nil},
+	{"12345x", 0, ErrSyntax},
+	{"98765432100", 98765432100, nil},
+	{"18446744073709551615", 1<<64 - 1, nil},
+	{"18446744073709551616", 1<<64 - 1, ErrRange},
+	{"18446744073709551620", 1<<64 - 1, ErrRange},
+	{"1_2_3_4_5", 0, ErrSyntax}, // base=10 so no underscores allowed
+	{"_12345", 0, ErrSyntax},
+	{"1__2345", 0, ErrSyntax},
+	{"12345_", 0, ErrSyntax},
+	{"-0", 0, ErrSyntax},
+	{"-1", 0, ErrSyntax},
+	{"+1", 0, ErrSyntax},
+}
+
+type parseUint64BaseTest struct {
+	in   string
+	base int
+	out  uint64
+	err  error
+}
+
+var parseUint64BaseTests = []parseUint64BaseTest{
+	{"", 0, 0, ErrSyntax},
+	{"0", 0, 0, nil},
+	{"0x", 0, 0, ErrSyntax},
+	{"0X", 0, 0, ErrSyntax},
+	{"1", 0, 1, nil},
+	{"12345", 0, 12345, nil},
+	{"012345", 0, 012345, nil},
+	{"0x12345", 0, 0x12345, nil},
+	{"0X12345", 0, 0x12345, nil},
+	{"12345x", 0, 0, ErrSyntax},
+	{"0xabcdefg123", 0, 0, ErrSyntax},
+	{"123456789abc", 0, 0, ErrSyntax},
+	{"98765432100", 0, 98765432100, nil},
+	{"18446744073709551615", 0, 1<<64 - 1, nil},
+	{"18446744073709551616", 0, 1<<64 - 1, ErrRange},
+	{"18446744073709551620", 0, 1<<64 - 1, ErrRange},
+	{"0xFFFFFFFFFFFFFFFF", 0, 1<<64 - 1, nil},
+	{"0x10000000000000000", 0, 1<<64 - 1, ErrRange},
+	{"01777777777777777777777", 0, 1<<64 - 1, nil},
+	{"01777777777777777777778", 0, 0, ErrSyntax},
+	{"02000000000000000000000", 0, 1<<64 - 1, ErrRange},
+	{"0200000000000000000000", 0, 1 << 61, nil},
+	{"0b", 0, 0, ErrSyntax},
+	{"0B", 0, 0, ErrSyntax},
+	{"0b101", 0, 5, nil},
+	{"0B101", 0, 5, nil},
+	{"0o", 0, 0, ErrSyntax},
+	{"0O", 0, 0, ErrSyntax},
+	{"0o377", 0, 255, nil},
+	{"0O377", 0, 255, nil},
+
+	// underscores allowed with base == 0 only
+	{"1_2_3_4_5", 0, 12345, nil}, // base 0 => 10
+	{"_12345", 0, 0, ErrSyntax},
+	{"1__2345", 0, 0, ErrSyntax},
+	{"12345_", 0, 0, ErrSyntax},
+
+	{"1_2_3_4_5", 10, 0, ErrSyntax}, // base 10
+	{"_12345", 10, 0, ErrSyntax},
+	{"1__2345", 10, 0, ErrSyntax},
+	{"12345_", 10, 0, ErrSyntax},
+
+	{"0x_1_2_3_4_5", 0, 0x12345, nil}, // base 0 => 16
+	{"_0x12345", 0, 0, ErrSyntax},
+	{"0x__12345", 0, 0, ErrSyntax},
+	{"0x1__2345", 0, 0, ErrSyntax},
+	{"0x1234__5", 0, 0, ErrSyntax},
+	{"0x12345_", 0, 0, ErrSyntax},
+
+	{"1_2_3_4_5", 16, 0, ErrSyntax}, // base 16
+	{"_12345", 16, 0, ErrSyntax},
+	{"1__2345", 16, 0, ErrSyntax},
+	{"1234__5", 16, 0, ErrSyntax},
+	{"12345_", 16, 0, ErrSyntax},
+
+	{"0_1_2_3_4_5", 0, 012345, nil}, // base 0 => 8 (0377)
+	{"_012345", 0, 0, ErrSyntax},
+	{"0__12345", 0, 0, ErrSyntax},
+	{"01234__5", 0, 0, ErrSyntax},
+	{"012345_", 0, 0, ErrSyntax},
+
+	{"0o_1_2_3_4_5", 0, 012345, nil}, // base 0 => 8 (0o377)
+	{"_0o12345", 0, 0, ErrSyntax},
+	{"0o__12345", 0, 0, ErrSyntax},
+	{"0o1234__5", 0, 0, ErrSyntax},
+	{"0o12345_", 0, 0, ErrSyntax},
+
+	{"0_1_2_3_4_5", 8, 0, ErrSyntax}, // base 8
+	{"_012345", 8, 0, ErrSyntax},
+	{"0__12345", 8, 0, ErrSyntax},
+	{"01234__5", 8, 0, ErrSyntax},
+	{"012345_", 8, 0, ErrSyntax},
+
+	{"0b_1_0_1", 0, 5, nil}, // base 0 => 2 (0b101)
+	{"_0b101", 0, 0, ErrSyntax},
+	{"0b__101", 0, 0, ErrSyntax},
+	{"0b1__01", 0, 0, ErrSyntax},
+	{"0b10__1", 0, 0, ErrSyntax},
+	{"0b101_", 0, 0, ErrSyntax},
+
+	{"1_0_1", 2, 0, ErrSyntax}, // base 2
+	{"_101", 2, 0, ErrSyntax},
+	{"1_01", 2, 0, ErrSyntax},
+	{"10_1", 2, 0, ErrSyntax},
+	{"101_", 2, 0, ErrSyntax},
+}
+
+type parseInt64Test struct {
+	in  string
+	out int64
+	err error
+}
+
+var parseInt64Tests = []parseInt64Test{
+	{"", 0, ErrSyntax},
+	{"0", 0, nil},
+	{"-0", 0, nil},
+	{"+0", 0, nil},
+	{"1", 1, nil},
+	{"-1", -1, nil},
+	{"+1", 1, nil},
+	{"12345", 12345, nil},
+	{"-12345", -12345, nil},
+	{"012345", 12345, nil},
+	{"-012345", -12345, nil},
+	{"98765432100", 98765432100, nil},
+	{"-98765432100", -98765432100, nil},
+	{"9223372036854775807", 1<<63 - 1, nil},
+	{"-9223372036854775807", -(1<<63 - 1), nil},
+	{"9223372036854775808", 1<<63 - 1, ErrRange},
+	{"-9223372036854775808", -1 << 63, nil},
+	{"9223372036854775809", 1<<63 - 1, ErrRange},
+	{"-9223372036854775809", -1 << 63, ErrRange},
+	{"-1_2_3_4_5", 0, ErrSyntax}, // base=10 so no underscores allowed
+	{"-_12345", 0, ErrSyntax},
+	{"_12345", 0, ErrSyntax},
+	{"1__2345", 0, ErrSyntax},
+	{"12345_", 0, ErrSyntax},
+	{"123%45", 0, ErrSyntax},
+}
+
+type parseInt64BaseTest struct {
+	in   string
+	base int
+	out  int64
+	err  error
+}
+
+var parseInt64BaseTests = []parseInt64BaseTest{
+	{"", 0, 0, ErrSyntax},
+	{"0", 0, 0, nil},
+	{"-0", 0, 0, nil},
+	{"1", 0, 1, nil},
+	{"-1", 0, -1, nil},
+	{"12345", 0, 12345, nil},
+	{"-12345", 0, -12345, nil},
+	{"012345", 0, 012345, nil},
+	{"-012345", 0, -012345, nil},
+	{"0x12345", 0, 0x12345, nil},
+	{"-0X12345", 0, -0x12345, nil},
+	{"12345x", 0, 0, ErrSyntax},
+	{"-12345x", 0, 0, ErrSyntax},
+	{"98765432100", 0, 98765432100, nil},
+	{"-98765432100", 0, -98765432100, nil},
+	{"9223372036854775807", 0, 1<<63 - 1, nil},
+	{"-9223372036854775807", 0, -(1<<63 - 1), nil},
+	{"9223372036854775808", 0, 1<<63 - 1, ErrRange},
+	{"-9223372036854775808", 0, -1 << 63, nil},
+	{"9223372036854775809", 0, 1<<63 - 1, ErrRange},
+	{"-9223372036854775809", 0, -1 << 63, ErrRange},
+
+	// other bases
+	{"g", 17, 16, nil},
+	{"10", 25, 25, nil},
+	{"holycow", 35, (((((17*35+24)*35+21)*35+34)*35+12)*35+24)*35 + 32, nil},
+	{"holycow", 36, (((((17*36+24)*36+21)*36+34)*36+12)*36+24)*36 + 32, nil},
+
+	// base 2
+	{"0", 2, 0, nil},
+	{"-1", 2, -1, nil},
+	{"1010", 2, 10, nil},
+	{"1000000000000000", 2, 1 << 15, nil},
+	{"111111111111111111111111111111111111111111111111111111111111111", 2, 1<<63 - 1, nil},
+	{"1000000000000000000000000000000000000000000000000000000000000000", 2, 1<<63 - 1, ErrRange},
+	{"-1000000000000000000000000000000000000000000000000000000000000000", 2, -1 << 63, nil},
+	{"-1000000000000000000000000000000000000000000000000000000000000001", 2, -1 << 63, ErrRange},
+
+	// base 8
+	{"-10", 8, -8, nil},
+	{"57635436545", 8, 057635436545, nil},
+	{"100000000", 8, 1 << 24, nil},
+
+	// base 16
+	{"10", 16, 16, nil},
+	{"-123456789abcdef", 16, -0x123456789abcdef, nil},
+	{"7fffffffffffffff", 16, 1<<63 - 1, nil},
+
+	// underscores
+	{"-0x_1_2_3_4_5", 0, -0x12345, nil},
+	{"0x_1_2_3_4_5", 0, 0x12345, nil},
+	{"-_0x12345", 0, 0, ErrSyntax},
+	{"_-0x12345", 0, 0, ErrSyntax},
+	{"_0x12345", 0, 0, ErrSyntax},
+	{"0x__12345", 0, 0, ErrSyntax},
+	{"0x1__2345", 0, 0, ErrSyntax},
+	{"0x1234__5", 0, 0, ErrSyntax},
+	{"0x12345_", 0, 0, ErrSyntax},
+
+	{"-0_1_2_3_4_5", 0, -012345, nil}, // octal
+	{"0_1_2_3_4_5", 0, 012345, nil},   // octal
+	{"-_012345", 0, 0, ErrSyntax},
+	{"_-012345", 0, 0, ErrSyntax},
+	{"_012345", 0, 0, ErrSyntax},
+	{"0__12345", 0, 0, ErrSyntax},
+	{"01234__5", 0, 0, ErrSyntax},
+	{"012345_", 0, 0, ErrSyntax},
+
+	{"+0xf", 0, 0xf, nil},
+	{"-0xf", 0, -0xf, nil},
+	{"0x+f", 0, 0, ErrSyntax},
+	{"0x-f", 0, 0, ErrSyntax},
+}
+
+type parseUint32Test struct {
+	in  string
+	out uint32
+	err error
+}
+
+var parseUint32Tests = []parseUint32Test{
+	{"", 0, ErrSyntax},
+	{"0", 0, nil},
+	{"1", 1, nil},
+	{"12345", 12345, nil},
+	{"012345", 12345, nil},
+	{"12345x", 0, ErrSyntax},
+	{"987654321", 987654321, nil},
+	{"4294967295", 1<<32 - 1, nil},
+	{"4294967296", 1<<32 - 1, ErrRange},
+	{"1_2_3_4_5", 0, ErrSyntax}, // base=10 so no underscores allowed
+	{"_12345", 0, ErrSyntax},
+	{"_12345", 0, ErrSyntax},
+	{"1__2345", 0, ErrSyntax},
+	{"12345_", 0, ErrSyntax},
+}
+
+type parseInt32Test struct {
+	in  string
+	out int32
+	err error
+}
+
+var parseInt32Tests = []parseInt32Test{
+	{"", 0, ErrSyntax},
+	{"0", 0, nil},
+	{"-0", 0, nil},
+	{"1", 1, nil},
+	{"-1", -1, nil},
+	{"12345", 12345, nil},
+	{"-12345", -12345, nil},
+	{"012345", 12345, nil},
+	{"-012345", -12345, nil},
+	{"12345x", 0, ErrSyntax},
+	{"-12345x", 0, ErrSyntax},
+	{"987654321", 987654321, nil},
+	{"-987654321", -987654321, nil},
+	{"2147483647", 1<<31 - 1, nil},
+	{"-2147483647", -(1<<31 - 1), nil},
+	{"2147483648", 1<<31 - 1, ErrRange},
+	{"-2147483648", -1 << 31, nil},
+	{"2147483649", 1<<31 - 1, ErrRange},
+	{"-2147483649", -1 << 31, ErrRange},
+	{"-1_2_3_4_5", 0, ErrSyntax}, // base=10 so no underscores allowed
+	{"-_12345", 0, ErrSyntax},
+	{"_12345", 0, ErrSyntax},
+	{"1__2345", 0, ErrSyntax},
+	{"12345_", 0, ErrSyntax},
+	{"123%45", 0, ErrSyntax},
+}
+
+type numErrorTest struct {
+	num, want string
+}
+
+var numErrorTests = []numErrorTest{
+	{"0", `strconv.ParseFloat: parsing "0": failed`},
+	{"`", "strconv.ParseFloat: parsing \"`\": failed"},
+	{"1\x00.2", `strconv.ParseFloat: parsing "1\x00.2": failed`},
+}
+
+func init() {
+	// The parse routines return NumErrors wrapping
+	// the error and the string. Convert the tables above.
+	for i := range parseUint64Tests {
+		test := &parseUint64Tests[i]
+		if test.err != nil {
+			test.err = &NumError{"ParseUint", test.in, test.err}
+		}
+	}
+	for i := range parseUint64BaseTests {
+		test := &parseUint64BaseTests[i]
+		if test.err != nil {
+			test.err = &NumError{"ParseUint", test.in, test.err}
+		}
+	}
+	for i := range parseInt64Tests {
+		test := &parseInt64Tests[i]
+		if test.err != nil {
+			test.err = &NumError{"ParseInt", test.in, test.err}
+		}
+	}
+	for i := range parseInt64BaseTests {
+		test := &parseInt64BaseTests[i]
+		if test.err != nil {
+			test.err = &NumError{"ParseInt", test.in, test.err}
+		}
+	}
+	for i := range parseUint32Tests {
+		test := &parseUint32Tests[i]
+		if test.err != nil {
+			test.err = &NumError{"ParseUint", test.in, test.err}
+		}
+	}
+	for i := range parseInt32Tests {
+		test := &parseInt32Tests[i]
+		if test.err != nil {
+			test.err = &NumError{"ParseInt", test.in, test.err}
+		}
+	}
+}
+
+func TestParseUint32(t *testing.T) {
+	for i := range parseUint32Tests {
+		test := &parseUint32Tests[i]
+		out, err := ParseUint(test.in, 10, 32)
+		if uint64(test.out) != out || !reflect.DeepEqual(test.err, err) {
+			t.Errorf("ParseUint(%q, 10, 32) = %v, %v want %v, %v",
+				test.in, out, err, test.out, test.err)
+		}
+	}
+}
+
+func TestParseUint64(t *testing.T) {
+	for i := range parseUint64Tests {
+		test := &parseUint64Tests[i]
+		out, err := ParseUint(test.in, 10, 64)
+		if test.out != out || !reflect.DeepEqual(test.err, err) {
+			t.Errorf("ParseUint(%q, 10, 64) = %v, %v want %v, %v",
+				test.in, out, err, test.out, test.err)
+		}
+	}
+}
+
+func TestParseUint64Base(t *testing.T) {
+	for i := range parseUint64BaseTests {
+		test := &parseUint64BaseTests[i]
+		out, err := ParseUint(test.in, test.base, 64)
+		if test.out != out || !reflect.DeepEqual(test.err, err) {
+			t.Errorf("ParseUint(%q, %v, 64) = %v, %v want %v, %v",
+				test.in, test.base, out, err, test.out, test.err)
+		}
+	}
+}
+
+func TestParseInt32(t *testing.T) {
+	for i := range parseInt32Tests {
+		test := &parseInt32Tests[i]
+		out, err := ParseInt(test.in, 10, 32)
+		if int64(test.out) != out || !reflect.DeepEqual(test.err, err) {
+			t.Errorf("ParseInt(%q, 10 ,32) = %v, %v want %v, %v",
+				test.in, out, err, test.out, test.err)
+		}
+	}
+}
+
+func TestParseInt64(t *testing.T) {
+	for i := range parseInt64Tests {
+		test := &parseInt64Tests[i]
+		out, err := ParseInt(test.in, 10, 64)
+		if test.out != out || !reflect.DeepEqual(test.err, err) {
+			t.Errorf("ParseInt(%q, 10, 64) = %v, %v want %v, %v",
+				test.in, out, err, test.out, test.err)
+		}
+	}
+}
+
+func TestParseInt64Base(t *testing.T) {
+	for i := range parseInt64BaseTests {
+		test := &parseInt64BaseTests[i]
+		out, err := ParseInt(test.in, test.base, 64)
+		if test.out != out || !reflect.DeepEqual(test.err, err) {
+			t.Errorf("ParseInt(%q, %v, 64) = %v, %v want %v, %v",
+				test.in, test.base, out, err, test.out, test.err)
+		}
+	}
+}
+
+func TestParseUint(t *testing.T) {
+	switch IntSize {
+	case 32:
+		for i := range parseUint32Tests {
+			test := &parseUint32Tests[i]
+			out, err := ParseUint(test.in, 10, 0)
+			if uint64(test.out) != out || !reflect.DeepEqual(test.err, err) {
+				t.Errorf("ParseUint(%q, 10, 0) = %v, %v want %v, %v",
+					test.in, out, err, test.out, test.err)
+			}
+		}
+	case 64:
+		for i := range parseUint64Tests {
+			test := &parseUint64Tests[i]
+			out, err := ParseUint(test.in, 10, 0)
+			if test.out != out || !reflect.DeepEqual(test.err, err) {
+				t.Errorf("ParseUint(%q, 10, 0) = %v, %v want %v, %v",
+					test.in, out, err, test.out, test.err)
+			}
+		}
+	}
+}
+
+func TestParseInt(t *testing.T) {
+	switch IntSize {
+	case 32:
+		for i := range parseInt32Tests {
+			test := &parseInt32Tests[i]
+			out, err := ParseInt(test.in, 10, 0)
+			if int64(test.out) != out || !reflect.DeepEqual(test.err, err) {
+				t.Errorf("ParseInt(%q, 10, 0) = %v, %v want %v, %v",
+					test.in, out, err, test.out, test.err)
+			}
+		}
+	case 64:
+		for i := range parseInt64Tests {
+			test := &parseInt64Tests[i]
+			out, err := ParseInt(test.in, 10, 0)
+			if test.out != out || !reflect.DeepEqual(test.err, err) {
+				t.Errorf("ParseInt(%q, 10, 0) = %v, %v want %v, %v",
+					test.in, out, err, test.out, test.err)
+			}
+		}
+	}
+}
+
+func TestAtoi(t *testing.T) {
+	switch IntSize {
+	case 32:
+		for i := range parseInt32Tests {
+			test := &parseInt32Tests[i]
+			out, err := Atoi(test.in)
+			var testErr error
+			if test.err != nil {
+				testErr = &NumError{"Atoi", test.in, test.err.(*NumError).Err}
+			}
+			if int(test.out) != out || !reflect.DeepEqual(testErr, err) {
+				t.Errorf("Atoi(%q) = %v, %v want %v, %v",
+					test.in, out, err, test.out, testErr)
+			}
+		}
+	case 64:
+		for i := range parseInt64Tests {
+			test := &parseInt64Tests[i]
+			out, err := Atoi(test.in)
+			var testErr error
+			if test.err != nil {
+				testErr = &NumError{"Atoi", test.in, test.err.(*NumError).Err}
+			}
+			if test.out != int64(out) || !reflect.DeepEqual(testErr, err) {
+				t.Errorf("Atoi(%q) = %v, %v want %v, %v",
+					test.in, out, err, test.out, testErr)
+			}
+		}
+	}
+}
+
+func bitSizeErrStub(name string, bitSize int) error {
+	return BitSizeError(name, "0", bitSize)
+}
+
+func baseErrStub(name string, base int) error {
+	return BaseError(name, "0", base)
+}
+
+func noErrStub(name string, arg int) error {
+	return nil
+}
+
+type parseErrorTest struct {
+	arg     int
+	errStub func(name string, arg int) error
+}
+
+var parseBitSizeTests = []parseErrorTest{
+	{-1, bitSizeErrStub},
+	{0, noErrStub},
+	{64, noErrStub},
+	{65, bitSizeErrStub},
+}
+
+var parseBaseTests = []parseErrorTest{
+	{-1, baseErrStub},
+	{0, noErrStub},
+	{1, baseErrStub},
+	{2, noErrStub},
+	{36, noErrStub},
+	{37, baseErrStub},
+}
+
+func equalError(a, b error) bool {
+	if a == nil {
+		return b == nil
+	}
+	if b == nil {
+		return a == nil
+	}
+	return a.Error() == b.Error()
+}
+
+func TestParseIntBitSize(t *testing.T) {
+	for i := range parseBitSizeTests {
+		test := &parseBitSizeTests[i]
+		testErr := test.errStub("ParseInt", test.arg)
+		_, err := ParseInt("0", 0, test.arg)
+		if !equalError(testErr, err) {
+			t.Errorf("ParseInt(\"0\", 0, %v) = 0, %v want 0, %v",
+				test.arg, err, testErr)
+		}
+	}
+}
+
+func TestParseUintBitSize(t *testing.T) {
+	for i := range parseBitSizeTests {
+		test := &parseBitSizeTests[i]
+		testErr := test.errStub("ParseUint", test.arg)
+		_, err := ParseUint("0", 0, test.arg)
+		if !equalError(testErr, err) {
+			t.Errorf("ParseUint(\"0\", 0, %v) = 0, %v want 0, %v",
+				test.arg, err, testErr)
+		}
+	}
+}
+
+func TestParseIntBase(t *testing.T) {
+	for i := range parseBaseTests {
+		test := &parseBaseTests[i]
+		testErr := test.errStub("ParseInt", test.arg)
+		_, err := ParseInt("0", test.arg, 0)
+		if !equalError(testErr, err) {
+			t.Errorf("ParseInt(\"0\", %v, 0) = 0, %v want 0, %v",
+				test.arg, err, testErr)
+		}
+	}
+}
+
+func TestParseUintBase(t *testing.T) {
+	for i := range parseBaseTests {
+		test := &parseBaseTests[i]
+		testErr := test.errStub("ParseUint", test.arg)
+		_, err := ParseUint("0", test.arg, 0)
+		if !equalError(testErr, err) {
+			t.Errorf("ParseUint(\"0\", %v, 0) = 0, %v want 0, %v",
+				test.arg, err, testErr)
+		}
+	}
+}
+
+func TestNumError(t *testing.T) {
+	for _, test := range numErrorTests {
+		err := &NumError{
+			Func: "ParseFloat",
+			Num:  test.num,
+			Err:  errors.New("failed"),
+		}
+		if got := err.Error(); got != test.want {
+			t.Errorf(`(&NumError{"ParseFloat", %q, "failed"}).Error() = %v, want %v`, test.num, got, test.want)
+		}
+	}
+}
+
+func TestNumErrorUnwrap(t *testing.T) {
+	err := &NumError{Err: ErrSyntax}
+	if !errors.Is(err, ErrSyntax) {
+		t.Error("errors.Is failed, wanted success")
+	}
+}
+
+func BenchmarkParseInt(b *testing.B) {
+	b.Run("Pos", func(b *testing.B) {
+		benchmarkParseInt(b, 1)
+	})
+	b.Run("Neg", func(b *testing.B) {
+		benchmarkParseInt(b, -1)
+	})
+}
+
+type benchCase struct {
+	name string
+	num  int64
+}
+
+func benchmarkParseInt(b *testing.B, neg int) {
+	cases := []benchCase{
+		{"7bit", 1<<7 - 1},
+		{"26bit", 1<<26 - 1},
+		{"31bit", 1<<31 - 1},
+		{"56bit", 1<<56 - 1},
+		{"63bit", 1<<63 - 1},
+	}
+	for _, cs := range cases {
+		b.Run(cs.name, func(b *testing.B) {
+			s := fmt.Sprintf("%d", cs.num*int64(neg))
+			for i := 0; i < b.N; i++ {
+				out, _ := ParseInt(s, 10, 64)
+				BenchSink += int(out)
+			}
+		})
+	}
+}
+
+func BenchmarkAtoi(b *testing.B) {
+	b.Run("Pos", func(b *testing.B) {
+		benchmarkAtoi(b, 1)
+	})
+	b.Run("Neg", func(b *testing.B) {
+		benchmarkAtoi(b, -1)
+	})
+}
+
+func benchmarkAtoi(b *testing.B, neg int) {
+	cases := []benchCase{
+		{"7bit", 1<<7 - 1},
+		{"26bit", 1<<26 - 1},
+		{"31bit", 1<<31 - 1},
+	}
+	if IntSize == 64 {
+		cases = append(cases, []benchCase{
+			{"56bit", 1<<56 - 1},
+			{"63bit", 1<<63 - 1},
+		}...)
+	}
+	for _, cs := range cases {
+		b.Run(cs.name, func(b *testing.B) {
+			s := fmt.Sprintf("%d", cs.num*int64(neg))
+			for i := 0; i < b.N; i++ {
+				out, _ := Atoi(s)
+				BenchSink += out
+			}
+		})
+	}
+}
diff --git a/src/strconv/bytealg.go b/src/strconv/bytealg.go
new file mode 100644
index 0000000..6fe1624
--- /dev/null
+++ b/src/strconv/bytealg.go
@@ -0,0 +1,14 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !compiler_bootstrap
+
+package strconv
+
+import "internal/bytealg"
+
+// index returns the index of the first instance of c in s, or -1 if missing.
+func index(s string, c byte) int {
+	return bytealg.IndexByteString(s, c)
+}
diff --git a/src/strconv/bytealg_bootstrap.go b/src/strconv/bytealg_bootstrap.go
new file mode 100644
index 0000000..12d96e5
--- /dev/null
+++ b/src/strconv/bytealg_bootstrap.go
@@ -0,0 +1,17 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build compiler_bootstrap
+
+package strconv
+
+// index returns the index of the first instance of c in s, or -1 if missing.
+func index(s string, c byte) int {
+	for i := 0; i < len(s); i++ {
+		if s[i] == c {
+			return i
+		}
+	}
+	return -1
+}
diff --git a/src/strconv/ctoa.go b/src/strconv/ctoa.go
new file mode 100644
index 0000000..c16a2e5
--- /dev/null
+++ b/src/strconv/ctoa.go
@@ -0,0 +1,27 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv
+
+// FormatComplex converts the complex number c to a string of the
+// form (a+bi) where a and b are the real and imaginary parts,
+// formatted according to the format fmt and precision prec.
+//
+// The format fmt and precision prec have the same meaning as in FormatFloat.
+// It rounds the result assuming that the original was obtained from a complex
+// value of bitSize bits, which must be 64 for complex64 and 128 for complex128.
+func FormatComplex(c complex128, fmt byte, prec, bitSize int) string {
+	if bitSize != 64 && bitSize != 128 {
+		panic("invalid bitSize")
+	}
+	bitSize >>= 1 // complex64 uses float32 internally
+
+	// Check if imaginary part has a sign. If not, add one.
+	im := FormatFloat(imag(c), fmt, prec, bitSize)
+	if im[0] != '+' && im[0] != '-' {
+		im = "+" + im
+	}
+
+	return "(" + FormatFloat(real(c), fmt, prec, bitSize) + im + "i)"
+}
diff --git a/src/strconv/ctoa_test.go b/src/strconv/ctoa_test.go
new file mode 100644
index 0000000..8b77898
--- /dev/null
+++ b/src/strconv/ctoa_test.go
@@ -0,0 +1,53 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv_test
+
+import (
+	. "strconv"
+	"testing"
+)
+
+func TestFormatComplex(t *testing.T) {
+	tests := []struct {
+		c       complex128
+		fmt     byte
+		prec    int
+		bitSize int
+		out     string
+	}{
+		// a variety of signs
+		{1 + 2i, 'g', -1, 128, "(1+2i)"},
+		{3 - 4i, 'g', -1, 128, "(3-4i)"},
+		{-5 + 6i, 'g', -1, 128, "(-5+6i)"},
+		{-7 - 8i, 'g', -1, 128, "(-7-8i)"},
+
+		// test that fmt and prec are working
+		{3.14159 + 0.00123i, 'e', 3, 128, "(3.142e+00+1.230e-03i)"},
+		{3.14159 + 0.00123i, 'f', 3, 128, "(3.142+0.001i)"},
+		{3.14159 + 0.00123i, 'g', 3, 128, "(3.14+0.00123i)"},
+
+		// ensure bitSize rounding is working
+		{1.2345678901234567 + 9.876543210987654i, 'f', -1, 128, "(1.2345678901234567+9.876543210987654i)"},
+		{1.2345678901234567 + 9.876543210987654i, 'f', -1, 64, "(1.2345679+9.876543i)"},
+
+		// other cases are handled by FormatFloat tests
+	}
+	for _, test := range tests {
+		out := FormatComplex(test.c, test.fmt, test.prec, test.bitSize)
+		if out != test.out {
+			t.Fatalf("FormatComplex(%v, %q, %d, %d) = %q; want %q",
+				test.c, test.fmt, test.prec, test.bitSize, out, test.out)
+		}
+	}
+}
+
+func TestFormatComplexInvalidBitSize(t *testing.T) {
+	defer func() {
+		if r := recover(); r == nil {
+			t.Fatalf("expected panic due to invalid bitSize")
+		}
+	}()
+	_ = FormatComplex(1+2i, 'g', -1, 100)
+}
diff --git a/src/strconv/decimal.go b/src/strconv/decimal.go
new file mode 100644
index 0000000..b580018
--- /dev/null
+++ b/src/strconv/decimal.go
@@ -0,0 +1,415 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Multiprecision decimal numbers.
+// For floating-point formatting only; not general purpose.
+// Only operations are assign and (binary) left/right shift.
+// Can do binary floating point in multiprecision decimal precisely
+// because 2 divides 10; cannot do decimal floating point
+// in multiprecision binary precisely.
+
+package strconv
+
+type decimal struct {
+	d     [800]byte // digits, big-endian representation
+	nd    int       // number of digits used
+	dp    int       // decimal point
+	neg   bool      // negative flag
+	trunc bool      // discarded nonzero digits beyond d[:nd]
+}
+
+func (a *decimal) String() string {
+	n := 10 + a.nd
+	if a.dp > 0 {
+		n += a.dp
+	}
+	if a.dp < 0 {
+		n += -a.dp
+	}
+
+	buf := make([]byte, n)
+	w := 0
+	switch {
+	case a.nd == 0:
+		return "0"
+
+	case a.dp <= 0:
+		// zeros fill space between decimal point and digits
+		buf[w] = '0'
+		w++
+		buf[w] = '.'
+		w++
+		w += digitZero(buf[w : w+-a.dp])
+		w += copy(buf[w:], a.d[0:a.nd])
+
+	case a.dp < a.nd:
+		// decimal point in middle of digits
+		w += copy(buf[w:], a.d[0:a.dp])
+		buf[w] = '.'
+		w++
+		w += copy(buf[w:], a.d[a.dp:a.nd])
+
+	default:
+		// zeros fill space between digits and decimal point
+		w += copy(buf[w:], a.d[0:a.nd])
+		w += digitZero(buf[w : w+a.dp-a.nd])
+	}
+	return string(buf[0:w])
+}
+
+func digitZero(dst []byte) int {
+	for i := range dst {
+		dst[i] = '0'
+	}
+	return len(dst)
+}
+
+// trim trailing zeros from number.
+// (They are meaningless; the decimal point is tracked
+// independent of the number of digits.)
+func trim(a *decimal) {
+	for a.nd > 0 && a.d[a.nd-1] == '0' {
+		a.nd--
+	}
+	if a.nd == 0 {
+		a.dp = 0
+	}
+}
+
+// Assign v to a.
+func (a *decimal) Assign(v uint64) {
+	var buf [24]byte
+
+	// Write reversed decimal in buf.
+	n := 0
+	for v > 0 {
+		v1 := v / 10
+		v -= 10 * v1
+		buf[n] = byte(v + '0')
+		n++
+		v = v1
+	}
+
+	// Reverse again to produce forward decimal in a.d.
+	a.nd = 0
+	for n--; n >= 0; n-- {
+		a.d[a.nd] = buf[n]
+		a.nd++
+	}
+	a.dp = a.nd
+	trim(a)
+}
+
+// Maximum shift that we can do in one pass without overflow.
+// A uint has 32 or 64 bits, and we have to be able to accommodate 9<<k.
+const uintSize = 32 << (^uint(0) >> 63)
+const maxShift = uintSize - 4
+
+// Binary shift right (/ 2) by k bits.  k <= maxShift to avoid overflow.
+func rightShift(a *decimal, k uint) {
+	r := 0 // read pointer
+	w := 0 // write pointer
+
+	// Pick up enough leading digits to cover first shift.
+	var n uint
+	for ; n>>k == 0; r++ {
+		if r >= a.nd {
+			if n == 0 {
+				// a == 0; shouldn't get here, but handle anyway.
+				a.nd = 0
+				return
+			}
+			for n>>k == 0 {
+				n = n * 10
+				r++
+			}
+			break
+		}
+		c := uint(a.d[r])
+		n = n*10 + c - '0'
+	}
+	a.dp -= r - 1
+
+	var mask uint = (1 << k) - 1
+
+	// Pick up a digit, put down a digit.
+	for ; r < a.nd; r++ {
+		c := uint(a.d[r])
+		dig := n >> k
+		n &= mask
+		a.d[w] = byte(dig + '0')
+		w++
+		n = n*10 + c - '0'
+	}
+
+	// Put down extra digits.
+	for n > 0 {
+		dig := n >> k
+		n &= mask
+		if w < len(a.d) {
+			a.d[w] = byte(dig + '0')
+			w++
+		} else if dig > 0 {
+			a.trunc = true
+		}
+		n = n * 10
+	}
+
+	a.nd = w
+	trim(a)
+}
+
+// Cheat sheet for left shift: table indexed by shift count giving
+// number of new digits that will be introduced by that shift.
+//
+// For example, leftcheats[4] = {2, "625"}.  That means that
+// if we are shifting by 4 (multiplying by 16), it will add 2 digits
+// when the string prefix is "625" through "999", and one fewer digit
+// if the string prefix is "000" through "624".
+//
+// Credit for this trick goes to Ken.
+
+type leftCheat struct {
+	delta  int    // number of new digits
+	cutoff string // minus one digit if original < a.
+}
+
+var leftcheats = []leftCheat{
+	// Leading digits of 1/2^i = 5^i.
+	// 5^23 is not an exact 64-bit floating point number,
+	// so have to use bc for the math.
+	// Go up to 60 to be large enough for 32bit and 64bit platforms.
+	/*
+		seq 60 | sed 's/^/5^/' | bc |
+		awk 'BEGIN{ print "\t{ 0, \"\" }," }
+		{
+			log2 = log(2)/log(10)
+			printf("\t{ %d, \"%s\" },\t// * %d\n",
+				int(log2*NR+1), $0, 2**NR)
+		}'
+	*/
+	{0, ""},
+	{1, "5"},                                           // * 2
+	{1, "25"},                                          // * 4
+	{1, "125"},                                         // * 8
+	{2, "625"},                                         // * 16
+	{2, "3125"},                                        // * 32
+	{2, "15625"},                                       // * 64
+	{3, "78125"},                                       // * 128
+	{3, "390625"},                                      // * 256
+	{3, "1953125"},                                     // * 512
+	{4, "9765625"},                                     // * 1024
+	{4, "48828125"},                                    // * 2048
+	{4, "244140625"},                                   // * 4096
+	{4, "1220703125"},                                  // * 8192
+	{5, "6103515625"},                                  // * 16384
+	{5, "30517578125"},                                 // * 32768
+	{5, "152587890625"},                                // * 65536
+	{6, "762939453125"},                                // * 131072
+	{6, "3814697265625"},                               // * 262144
+	{6, "19073486328125"},                              // * 524288
+	{7, "95367431640625"},                              // * 1048576
+	{7, "476837158203125"},                             // * 2097152
+	{7, "2384185791015625"},                            // * 4194304
+	{7, "11920928955078125"},                           // * 8388608
+	{8, "59604644775390625"},                           // * 16777216
+	{8, "298023223876953125"},                          // * 33554432
+	{8, "1490116119384765625"},                         // * 67108864
+	{9, "7450580596923828125"},                         // * 134217728
+	{9, "37252902984619140625"},                        // * 268435456
+	{9, "186264514923095703125"},                       // * 536870912
+	{10, "931322574615478515625"},                      // * 1073741824
+	{10, "4656612873077392578125"},                     // * 2147483648
+	{10, "23283064365386962890625"},                    // * 4294967296
+	{10, "116415321826934814453125"},                   // * 8589934592
+	{11, "582076609134674072265625"},                   // * 17179869184
+	{11, "2910383045673370361328125"},                  // * 34359738368
+	{11, "14551915228366851806640625"},                 // * 68719476736
+	{12, "72759576141834259033203125"},                 // * 137438953472
+	{12, "363797880709171295166015625"},                // * 274877906944
+	{12, "1818989403545856475830078125"},               // * 549755813888
+	{13, "9094947017729282379150390625"},               // * 1099511627776
+	{13, "45474735088646411895751953125"},              // * 2199023255552
+	{13, "227373675443232059478759765625"},             // * 4398046511104
+	{13, "1136868377216160297393798828125"},            // * 8796093022208
+	{14, "5684341886080801486968994140625"},            // * 17592186044416
+	{14, "28421709430404007434844970703125"},           // * 35184372088832
+	{14, "142108547152020037174224853515625"},          // * 70368744177664
+	{15, "710542735760100185871124267578125"},          // * 140737488355328
+	{15, "3552713678800500929355621337890625"},         // * 281474976710656
+	{15, "17763568394002504646778106689453125"},        // * 562949953421312
+	{16, "88817841970012523233890533447265625"},        // * 1125899906842624
+	{16, "444089209850062616169452667236328125"},       // * 2251799813685248
+	{16, "2220446049250313080847263336181640625"},      // * 4503599627370496
+	{16, "11102230246251565404236316680908203125"},     // * 9007199254740992
+	{17, "55511151231257827021181583404541015625"},     // * 18014398509481984
+	{17, "277555756156289135105907917022705078125"},    // * 36028797018963968
+	{17, "1387778780781445675529539585113525390625"},   // * 72057594037927936
+	{18, "6938893903907228377647697925567626953125"},   // * 144115188075855872
+	{18, "34694469519536141888238489627838134765625"},  // * 288230376151711744
+	{18, "173472347597680709441192448139190673828125"}, // * 576460752303423488
+	{19, "867361737988403547205962240695953369140625"}, // * 1152921504606846976
+}
+
+// Is the leading prefix of b lexicographically less than s?
+func prefixIsLessThan(b []byte, s string) bool {
+	for i := 0; i < len(s); i++ {
+		if i >= len(b) {
+			return true
+		}
+		if b[i] != s[i] {
+			return b[i] < s[i]
+		}
+	}
+	return false
+}
+
+// Binary shift left (* 2) by k bits.  k <= maxShift to avoid overflow.
+func leftShift(a *decimal, k uint) {
+	delta := leftcheats[k].delta
+	if prefixIsLessThan(a.d[0:a.nd], leftcheats[k].cutoff) {
+		delta--
+	}
+
+	r := a.nd         // read index
+	w := a.nd + delta // write index
+
+	// Pick up a digit, put down a digit.
+	var n uint
+	for r--; r >= 0; r-- {
+		n += (uint(a.d[r]) - '0') << k
+		quo := n / 10
+		rem := n - 10*quo
+		w--
+		if w < len(a.d) {
+			a.d[w] = byte(rem + '0')
+		} else if rem != 0 {
+			a.trunc = true
+		}
+		n = quo
+	}
+
+	// Put down extra digits.
+	for n > 0 {
+		quo := n / 10
+		rem := n - 10*quo
+		w--
+		if w < len(a.d) {
+			a.d[w] = byte(rem + '0')
+		} else if rem != 0 {
+			a.trunc = true
+		}
+		n = quo
+	}
+
+	a.nd += delta
+	if a.nd >= len(a.d) {
+		a.nd = len(a.d)
+	}
+	a.dp += delta
+	trim(a)
+}
+
+// Binary shift left (k > 0) or right (k < 0).
+func (a *decimal) Shift(k int) {
+	switch {
+	case a.nd == 0:
+		// nothing to do: a == 0
+	case k > 0:
+		for k > maxShift {
+			leftShift(a, maxShift)
+			k -= maxShift
+		}
+		leftShift(a, uint(k))
+	case k < 0:
+		for k < -maxShift {
+			rightShift(a, maxShift)
+			k += maxShift
+		}
+		rightShift(a, uint(-k))
+	}
+}
+
+// If we chop a at nd digits, should we round up?
+func shouldRoundUp(a *decimal, nd int) bool {
+	if nd < 0 || nd >= a.nd {
+		return false
+	}
+	if a.d[nd] == '5' && nd+1 == a.nd { // exactly halfway - round to even
+		// if we truncated, a little higher than what's recorded - always round up
+		if a.trunc {
+			return true
+		}
+		return nd > 0 && (a.d[nd-1]-'0')%2 != 0
+	}
+	// not halfway - digit tells all
+	return a.d[nd] >= '5'
+}
+
+// Round a to nd digits (or fewer).
+// If nd is zero, it means we're rounding
+// just to the left of the digits, as in
+// 0.09 -> 0.1.
+func (a *decimal) Round(nd int) {
+	if nd < 0 || nd >= a.nd {
+		return
+	}
+	if shouldRoundUp(a, nd) {
+		a.RoundUp(nd)
+	} else {
+		a.RoundDown(nd)
+	}
+}
+
+// Round a down to nd digits (or fewer).
+func (a *decimal) RoundDown(nd int) {
+	if nd < 0 || nd >= a.nd {
+		return
+	}
+	a.nd = nd
+	trim(a)
+}
+
+// Round a up to nd digits (or fewer).
+func (a *decimal) RoundUp(nd int) {
+	if nd < 0 || nd >= a.nd {
+		return
+	}
+
+	// round up
+	for i := nd - 1; i >= 0; i-- {
+		c := a.d[i]
+		if c < '9' { // can stop after this digit
+			a.d[i]++
+			a.nd = i + 1
+			return
+		}
+	}
+
+	// Number is all 9s.
+	// Change to single 1 with adjusted decimal point.
+	a.d[0] = '1'
+	a.nd = 1
+	a.dp++
+}
+
+// Extract integer part, rounded appropriately.
+// No guarantees about overflow.
+func (a *decimal) RoundedInteger() uint64 {
+	if a.dp > 20 {
+		return 0xFFFFFFFFFFFFFFFF
+	}
+	var i int
+	n := uint64(0)
+	for i = 0; i < a.dp && i < a.nd; i++ {
+		n = n*10 + uint64(a.d[i]-'0')
+	}
+	for ; i < a.dp; i++ {
+		n *= 10
+	}
+	if shouldRoundUp(a, a.dp) {
+		n++
+	}
+	return n
+}
diff --git a/src/strconv/decimal_test.go b/src/strconv/decimal_test.go
new file mode 100644
index 0000000..13a127f
--- /dev/null
+++ b/src/strconv/decimal_test.go
@@ -0,0 +1,127 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv_test
+
+import (
+	. "strconv"
+	"testing"
+)
+
+type shiftTest struct {
+	i     uint64
+	shift int
+	out   string
+}
+
+var shifttests = []shiftTest{
+	{0, -100, "0"},
+	{0, 100, "0"},
+	{1, 100, "1267650600228229401496703205376"},
+	{1, -100,
+		"0.00000000000000000000000000000078886090522101180541" +
+			"17285652827862296732064351090230047702789306640625",
+	},
+	{12345678, 8, "3160493568"},
+	{12345678, -8, "48225.3046875"},
+	{195312, 9, "99999744"},
+	{1953125, 9, "1000000000"},
+}
+
+func TestDecimalShift(t *testing.T) {
+	for i := 0; i < len(shifttests); i++ {
+		test := &shifttests[i]
+		d := NewDecimal(test.i)
+		d.Shift(test.shift)
+		s := d.String()
+		if s != test.out {
+			t.Errorf("Decimal %v << %v = %v, want %v",
+				test.i, test.shift, s, test.out)
+		}
+	}
+}
+
+type roundTest struct {
+	i               uint64
+	nd              int
+	down, round, up string
+	int             uint64
+}
+
+var roundtests = []roundTest{
+	{0, 4, "0", "0", "0", 0},
+	{12344999, 4, "12340000", "12340000", "12350000", 12340000},
+	{12345000, 4, "12340000", "12340000", "12350000", 12340000},
+	{12345001, 4, "12340000", "12350000", "12350000", 12350000},
+	{23454999, 4, "23450000", "23450000", "23460000", 23450000},
+	{23455000, 4, "23450000", "23460000", "23460000", 23460000},
+	{23455001, 4, "23450000", "23460000", "23460000", 23460000},
+
+	{99994999, 4, "99990000", "99990000", "100000000", 99990000},
+	{99995000, 4, "99990000", "100000000", "100000000", 100000000},
+	{99999999, 4, "99990000", "100000000", "100000000", 100000000},
+
+	{12994999, 4, "12990000", "12990000", "13000000", 12990000},
+	{12995000, 4, "12990000", "13000000", "13000000", 13000000},
+	{12999999, 4, "12990000", "13000000", "13000000", 13000000},
+}
+
+func TestDecimalRound(t *testing.T) {
+	for i := 0; i < len(roundtests); i++ {
+		test := &roundtests[i]
+		d := NewDecimal(test.i)
+		d.RoundDown(test.nd)
+		s := d.String()
+		if s != test.down {
+			t.Errorf("Decimal %v RoundDown %d = %v, want %v",
+				test.i, test.nd, s, test.down)
+		}
+		d = NewDecimal(test.i)
+		d.Round(test.nd)
+		s = d.String()
+		if s != test.round {
+			t.Errorf("Decimal %v Round %d = %v, want %v",
+				test.i, test.nd, s, test.down)
+		}
+		d = NewDecimal(test.i)
+		d.RoundUp(test.nd)
+		s = d.String()
+		if s != test.up {
+			t.Errorf("Decimal %v RoundUp %d = %v, want %v",
+				test.i, test.nd, s, test.up)
+		}
+	}
+}
+
+type roundIntTest struct {
+	i     uint64
+	shift int
+	int   uint64
+}
+
+var roundinttests = []roundIntTest{
+	{0, 100, 0},
+	{512, -8, 2},
+	{513, -8, 2},
+	{640, -8, 2},
+	{641, -8, 3},
+	{384, -8, 2},
+	{385, -8, 2},
+	{383, -8, 1},
+	{1, 100, 1<<64 - 1},
+	{1000, 0, 1000},
+}
+
+func TestDecimalRoundedInteger(t *testing.T) {
+	for i := 0; i < len(roundinttests); i++ {
+		test := roundinttests[i]
+		d := NewDecimal(test.i)
+		d.Shift(test.shift)
+		int := d.RoundedInteger()
+		if int != test.int {
+			t.Errorf("Decimal %v >> %v RoundedInteger = %v, want %v",
+				test.i, test.shift, int, test.int)
+		}
+	}
+}
diff --git a/src/strconv/doc.go b/src/strconv/doc.go
new file mode 100644
index 0000000..fa20f90
--- /dev/null
+++ b/src/strconv/doc.go
@@ -0,0 +1,56 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package strconv implements conversions to and from string representations
+// of basic data types.
+//
+// # Numeric Conversions
+//
+// The most common numeric conversions are Atoi (string to int) and Itoa (int to string).
+//
+//	i, err := strconv.Atoi("-42")
+//	s := strconv.Itoa(-42)
+//
+// These assume decimal and the Go int type.
+//
+// [ParseBool], [ParseFloat], [ParseInt], and [ParseUint] convert strings to values:
+//
+//	b, err := strconv.ParseBool("true")
+//	f, err := strconv.ParseFloat("3.1415", 64)
+//	i, err := strconv.ParseInt("-42", 10, 64)
+//	u, err := strconv.ParseUint("42", 10, 64)
+//
+// The parse functions return the widest type (float64, int64, and uint64),
+// but if the size argument specifies a narrower width the result can be
+// converted to that narrower type without data loss:
+//
+//	s := "2147483647" // biggest int32
+//	i64, err := strconv.ParseInt(s, 10, 32)
+//	...
+//	i := int32(i64)
+//
+// [FormatBool], [FormatFloat], [FormatInt], and [FormatUint] convert values to strings:
+//
+//	s := strconv.FormatBool(true)
+//	s := strconv.FormatFloat(3.1415, 'E', -1, 64)
+//	s := strconv.FormatInt(-42, 16)
+//	s := strconv.FormatUint(42, 16)
+//
+// [AppendBool], [AppendFloat], [AppendInt], and [AppendUint] are similar but
+// append the formatted value to a destination slice.
+//
+// # String Conversions
+//
+// [Quote] and [QuoteToASCII] convert strings to quoted Go string literals.
+// The latter guarantees that the result is an ASCII string, by escaping
+// any non-ASCII Unicode with \u:
+//
+//	q := strconv.Quote("Hello, 世界")
+//	q := strconv.QuoteToASCII("Hello, 世界")
+//
+// [QuoteRune] and [QuoteRuneToASCII] are similar but accept runes and
+// return quoted Go rune literals.
+//
+// [Unquote] and [UnquoteChar] unquote Go string and rune literals.
+package strconv
diff --git a/src/strconv/eisel_lemire.go b/src/strconv/eisel_lemire.go
new file mode 100644
index 0000000..03842e5
--- /dev/null
+++ b/src/strconv/eisel_lemire.go
@@ -0,0 +1,884 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv
+
+// This file implements the Eisel-Lemire ParseFloat algorithm, published in
+// 2020 and discussed extensively at
+// https://nigeltao.github.io/blog/2020/eisel-lemire.html
+//
+// The original C++ implementation is at
+// https://github.com/lemire/fast_double_parser/blob/644bef4306059d3be01a04e77d3cc84b379c596f/include/fast_double_parser.h#L840
+//
+// This Go re-implementation closely follows the C re-implementation at
+// https://github.com/google/wuffs/blob/ba3818cb6b473a2ed0b38ecfc07dbbd3a97e8ae7/internal/cgen/base/floatconv-submodule-code.c#L990
+//
+// Additional testing (on over several million test strings) is done by
+// https://github.com/nigeltao/parse-number-fxx-test-data/blob/5280dcfccf6d0b02a65ae282dad0b6d9de50e039/script/test-go-strconv.go
+
+import (
+	"math"
+	"math/bits"
+)
+
+func eiselLemire64(man uint64, exp10 int, neg bool) (f float64, ok bool) {
+	// The terse comments in this function body refer to sections of the
+	// https://nigeltao.github.io/blog/2020/eisel-lemire.html blog post.
+
+	// Exp10 Range.
+	if man == 0 {
+		if neg {
+			f = math.Float64frombits(0x8000000000000000) // Negative zero.
+		}
+		return f, true
+	}
+	if exp10 < detailedPowersOfTenMinExp10 || detailedPowersOfTenMaxExp10 < exp10 {
+		return 0, false
+	}
+
+	// Normalization.
+	clz := bits.LeadingZeros64(man)
+	man <<= uint(clz)
+	const float64ExponentBias = 1023
+	retExp2 := uint64(217706*exp10>>16+64+float64ExponentBias) - uint64(clz)
+
+	// Multiplication.
+	xHi, xLo := bits.Mul64(man, detailedPowersOfTen[exp10-detailedPowersOfTenMinExp10][1])
+
+	// Wider Approximation.
+	if xHi&0x1FF == 0x1FF && xLo+man < man {
+		yHi, yLo := bits.Mul64(man, detailedPowersOfTen[exp10-detailedPowersOfTenMinExp10][0])
+		mergedHi, mergedLo := xHi, xLo+yHi
+		if mergedLo < xLo {
+			mergedHi++
+		}
+		if mergedHi&0x1FF == 0x1FF && mergedLo+1 == 0 && yLo+man < man {
+			return 0, false
+		}
+		xHi, xLo = mergedHi, mergedLo
+	}
+
+	// Shifting to 54 Bits.
+	msb := xHi >> 63
+	retMantissa := xHi >> (msb + 9)
+	retExp2 -= 1 ^ msb
+
+	// Half-way Ambiguity.
+	if xLo == 0 && xHi&0x1FF == 0 && retMantissa&3 == 1 {
+		return 0, false
+	}
+
+	// From 54 to 53 Bits.
+	retMantissa += retMantissa & 1
+	retMantissa >>= 1
+	if retMantissa>>53 > 0 {
+		retMantissa >>= 1
+		retExp2 += 1
+	}
+	// retExp2 is a uint64. Zero or underflow means that we're in subnormal
+	// float64 space. 0x7FF or above means that we're in Inf/NaN float64 space.
+	//
+	// The if block is equivalent to (but has fewer branches than):
+	//   if retExp2 <= 0 || retExp2 >= 0x7FF { etc }
+	if retExp2-1 >= 0x7FF-1 {
+		return 0, false
+	}
+	retBits := retExp2<<52 | retMantissa&0x000FFFFFFFFFFFFF
+	if neg {
+		retBits |= 0x8000000000000000
+	}
+	return math.Float64frombits(retBits), true
+}
+
+func eiselLemire32(man uint64, exp10 int, neg bool) (f float32, ok bool) {
+	// The terse comments in this function body refer to sections of the
+	// https://nigeltao.github.io/blog/2020/eisel-lemire.html blog post.
+	//
+	// That blog post discusses the float64 flavor (11 exponent bits with a
+	// -1023 bias, 52 mantissa bits) of the algorithm, but the same approach
+	// applies to the float32 flavor (8 exponent bits with a -127 bias, 23
+	// mantissa bits). The computation here happens with 64-bit values (e.g.
+	// man, xHi, retMantissa) before finally converting to a 32-bit float.
+
+	// Exp10 Range.
+	if man == 0 {
+		if neg {
+			f = math.Float32frombits(0x80000000) // Negative zero.
+		}
+		return f, true
+	}
+	if exp10 < detailedPowersOfTenMinExp10 || detailedPowersOfTenMaxExp10 < exp10 {
+		return 0, false
+	}
+
+	// Normalization.
+	clz := bits.LeadingZeros64(man)
+	man <<= uint(clz)
+	const float32ExponentBias = 127
+	retExp2 := uint64(217706*exp10>>16+64+float32ExponentBias) - uint64(clz)
+
+	// Multiplication.
+	xHi, xLo := bits.Mul64(man, detailedPowersOfTen[exp10-detailedPowersOfTenMinExp10][1])
+
+	// Wider Approximation.
+	if xHi&0x3FFFFFFFFF == 0x3FFFFFFFFF && xLo+man < man {
+		yHi, yLo := bits.Mul64(man, detailedPowersOfTen[exp10-detailedPowersOfTenMinExp10][0])
+		mergedHi, mergedLo := xHi, xLo+yHi
+		if mergedLo < xLo {
+			mergedHi++
+		}
+		if mergedHi&0x3FFFFFFFFF == 0x3FFFFFFFFF && mergedLo+1 == 0 && yLo+man < man {
+			return 0, false
+		}
+		xHi, xLo = mergedHi, mergedLo
+	}
+
+	// Shifting to 54 Bits (and for float32, it's shifting to 25 bits).
+	msb := xHi >> 63
+	retMantissa := xHi >> (msb + 38)
+	retExp2 -= 1 ^ msb
+
+	// Half-way Ambiguity.
+	if xLo == 0 && xHi&0x3FFFFFFFFF == 0 && retMantissa&3 == 1 {
+		return 0, false
+	}
+
+	// From 54 to 53 Bits (and for float32, it's from 25 to 24 bits).
+	retMantissa += retMantissa & 1
+	retMantissa >>= 1
+	if retMantissa>>24 > 0 {
+		retMantissa >>= 1
+		retExp2 += 1
+	}
+	// retExp2 is a uint64. Zero or underflow means that we're in subnormal
+	// float32 space. 0xFF or above means that we're in Inf/NaN float32 space.
+	//
+	// The if block is equivalent to (but has fewer branches than):
+	//   if retExp2 <= 0 || retExp2 >= 0xFF { etc }
+	if retExp2-1 >= 0xFF-1 {
+		return 0, false
+	}
+	retBits := retExp2<<23 | retMantissa&0x007FFFFF
+	if neg {
+		retBits |= 0x80000000
+	}
+	return math.Float32frombits(uint32(retBits)), true
+}
+
+// detailedPowersOfTen{Min,Max}Exp10 is the power of 10 represented by the
+// first and last rows of detailedPowersOfTen. Both bounds are inclusive.
+const (
+	detailedPowersOfTenMinExp10 = -348
+	detailedPowersOfTenMaxExp10 = +347
+)
+
+// detailedPowersOfTen contains 128-bit mantissa approximations (rounded down)
+// to the powers of 10. For example:
+//
+//   - 1e43 ≈ (0xE596B7B0_C643C719                   * (2 ** 79))
+//   - 1e43 = (0xE596B7B0_C643C719_6D9CCD05_D0000000 * (2 ** 15))
+//
+// The mantissas are explicitly listed. The exponents are implied by a linear
+// expression with slope 217706.0/65536.0 ≈ log(10)/log(2).
+//
+// The table was generated by
+// https://github.com/google/wuffs/blob/ba3818cb6b473a2ed0b38ecfc07dbbd3a97e8ae7/script/print-mpb-powers-of-10.go
+var detailedPowersOfTen = [...][2]uint64{
+	{0x1732C869CD60E453, 0xFA8FD5A0081C0288}, // 1e-348
+	{0x0E7FBD42205C8EB4, 0x9C99E58405118195}, // 1e-347
+	{0x521FAC92A873B261, 0xC3C05EE50655E1FA}, // 1e-346
+	{0xE6A797B752909EF9, 0xF4B0769E47EB5A78}, // 1e-345
+	{0x9028BED2939A635C, 0x98EE4A22ECF3188B}, // 1e-344
+	{0x7432EE873880FC33, 0xBF29DCABA82FDEAE}, // 1e-343
+	{0x113FAA2906A13B3F, 0xEEF453D6923BD65A}, // 1e-342
+	{0x4AC7CA59A424C507, 0x9558B4661B6565F8}, // 1e-341
+	{0x5D79BCF00D2DF649, 0xBAAEE17FA23EBF76}, // 1e-340
+	{0xF4D82C2C107973DC, 0xE95A99DF8ACE6F53}, // 1e-339
+	{0x79071B9B8A4BE869, 0x91D8A02BB6C10594}, // 1e-338
+	{0x9748E2826CDEE284, 0xB64EC836A47146F9}, // 1e-337
+	{0xFD1B1B2308169B25, 0xE3E27A444D8D98B7}, // 1e-336
+	{0xFE30F0F5E50E20F7, 0x8E6D8C6AB0787F72}, // 1e-335
+	{0xBDBD2D335E51A935, 0xB208EF855C969F4F}, // 1e-334
+	{0xAD2C788035E61382, 0xDE8B2B66B3BC4723}, // 1e-333
+	{0x4C3BCB5021AFCC31, 0x8B16FB203055AC76}, // 1e-332
+	{0xDF4ABE242A1BBF3D, 0xADDCB9E83C6B1793}, // 1e-331
+	{0xD71D6DAD34A2AF0D, 0xD953E8624B85DD78}, // 1e-330
+	{0x8672648C40E5AD68, 0x87D4713D6F33AA6B}, // 1e-329
+	{0x680EFDAF511F18C2, 0xA9C98D8CCB009506}, // 1e-328
+	{0x0212BD1B2566DEF2, 0xD43BF0EFFDC0BA48}, // 1e-327
+	{0x014BB630F7604B57, 0x84A57695FE98746D}, // 1e-326
+	{0x419EA3BD35385E2D, 0xA5CED43B7E3E9188}, // 1e-325
+	{0x52064CAC828675B9, 0xCF42894A5DCE35EA}, // 1e-324
+	{0x7343EFEBD1940993, 0x818995CE7AA0E1B2}, // 1e-323
+	{0x1014EBE6C5F90BF8, 0xA1EBFB4219491A1F}, // 1e-322
+	{0xD41A26E077774EF6, 0xCA66FA129F9B60A6}, // 1e-321
+	{0x8920B098955522B4, 0xFD00B897478238D0}, // 1e-320
+	{0x55B46E5F5D5535B0, 0x9E20735E8CB16382}, // 1e-319
+	{0xEB2189F734AA831D, 0xC5A890362FDDBC62}, // 1e-318
+	{0xA5E9EC7501D523E4, 0xF712B443BBD52B7B}, // 1e-317
+	{0x47B233C92125366E, 0x9A6BB0AA55653B2D}, // 1e-316
+	{0x999EC0BB696E840A, 0xC1069CD4EABE89F8}, // 1e-315
+	{0xC00670EA43CA250D, 0xF148440A256E2C76}, // 1e-314
+	{0x380406926A5E5728, 0x96CD2A865764DBCA}, // 1e-313
+	{0xC605083704F5ECF2, 0xBC807527ED3E12BC}, // 1e-312
+	{0xF7864A44C633682E, 0xEBA09271E88D976B}, // 1e-311
+	{0x7AB3EE6AFBE0211D, 0x93445B8731587EA3}, // 1e-310
+	{0x5960EA05BAD82964, 0xB8157268FDAE9E4C}, // 1e-309
+	{0x6FB92487298E33BD, 0xE61ACF033D1A45DF}, // 1e-308
+	{0xA5D3B6D479F8E056, 0x8FD0C16206306BAB}, // 1e-307
+	{0x8F48A4899877186C, 0xB3C4F1BA87BC8696}, // 1e-306
+	{0x331ACDABFE94DE87, 0xE0B62E2929ABA83C}, // 1e-305
+	{0x9FF0C08B7F1D0B14, 0x8C71DCD9BA0B4925}, // 1e-304
+	{0x07ECF0AE5EE44DD9, 0xAF8E5410288E1B6F}, // 1e-303
+	{0xC9E82CD9F69D6150, 0xDB71E91432B1A24A}, // 1e-302
+	{0xBE311C083A225CD2, 0x892731AC9FAF056E}, // 1e-301
+	{0x6DBD630A48AAF406, 0xAB70FE17C79AC6CA}, // 1e-300
+	{0x092CBBCCDAD5B108, 0xD64D3D9DB981787D}, // 1e-299
+	{0x25BBF56008C58EA5, 0x85F0468293F0EB4E}, // 1e-298
+	{0xAF2AF2B80AF6F24E, 0xA76C582338ED2621}, // 1e-297
+	{0x1AF5AF660DB4AEE1, 0xD1476E2C07286FAA}, // 1e-296
+	{0x50D98D9FC890ED4D, 0x82CCA4DB847945CA}, // 1e-295
+	{0xE50FF107BAB528A0, 0xA37FCE126597973C}, // 1e-294
+	{0x1E53ED49A96272C8, 0xCC5FC196FEFD7D0C}, // 1e-293
+	{0x25E8E89C13BB0F7A, 0xFF77B1FCBEBCDC4F}, // 1e-292
+	{0x77B191618C54E9AC, 0x9FAACF3DF73609B1}, // 1e-291
+	{0xD59DF5B9EF6A2417, 0xC795830D75038C1D}, // 1e-290
+	{0x4B0573286B44AD1D, 0xF97AE3D0D2446F25}, // 1e-289
+	{0x4EE367F9430AEC32, 0x9BECCE62836AC577}, // 1e-288
+	{0x229C41F793CDA73F, 0xC2E801FB244576D5}, // 1e-287
+	{0x6B43527578C1110F, 0xF3A20279ED56D48A}, // 1e-286
+	{0x830A13896B78AAA9, 0x9845418C345644D6}, // 1e-285
+	{0x23CC986BC656D553, 0xBE5691EF416BD60C}, // 1e-284
+	{0x2CBFBE86B7EC8AA8, 0xEDEC366B11C6CB8F}, // 1e-283
+	{0x7BF7D71432F3D6A9, 0x94B3A202EB1C3F39}, // 1e-282
+	{0xDAF5CCD93FB0CC53, 0xB9E08A83A5E34F07}, // 1e-281
+	{0xD1B3400F8F9CFF68, 0xE858AD248F5C22C9}, // 1e-280
+	{0x23100809B9C21FA1, 0x91376C36D99995BE}, // 1e-279
+	{0xABD40A0C2832A78A, 0xB58547448FFFFB2D}, // 1e-278
+	{0x16C90C8F323F516C, 0xE2E69915B3FFF9F9}, // 1e-277
+	{0xAE3DA7D97F6792E3, 0x8DD01FAD907FFC3B}, // 1e-276
+	{0x99CD11CFDF41779C, 0xB1442798F49FFB4A}, // 1e-275
+	{0x40405643D711D583, 0xDD95317F31C7FA1D}, // 1e-274
+	{0x482835EA666B2572, 0x8A7D3EEF7F1CFC52}, // 1e-273
+	{0xDA3243650005EECF, 0xAD1C8EAB5EE43B66}, // 1e-272
+	{0x90BED43E40076A82, 0xD863B256369D4A40}, // 1e-271
+	{0x5A7744A6E804A291, 0x873E4F75E2224E68}, // 1e-270
+	{0x711515D0A205CB36, 0xA90DE3535AAAE202}, // 1e-269
+	{0x0D5A5B44CA873E03, 0xD3515C2831559A83}, // 1e-268
+	{0xE858790AFE9486C2, 0x8412D9991ED58091}, // 1e-267
+	{0x626E974DBE39A872, 0xA5178FFF668AE0B6}, // 1e-266
+	{0xFB0A3D212DC8128F, 0xCE5D73FF402D98E3}, // 1e-265
+	{0x7CE66634BC9D0B99, 0x80FA687F881C7F8E}, // 1e-264
+	{0x1C1FFFC1EBC44E80, 0xA139029F6A239F72}, // 1e-263
+	{0xA327FFB266B56220, 0xC987434744AC874E}, // 1e-262
+	{0x4BF1FF9F0062BAA8, 0xFBE9141915D7A922}, // 1e-261
+	{0x6F773FC3603DB4A9, 0x9D71AC8FADA6C9B5}, // 1e-260
+	{0xCB550FB4384D21D3, 0xC4CE17B399107C22}, // 1e-259
+	{0x7E2A53A146606A48, 0xF6019DA07F549B2B}, // 1e-258
+	{0x2EDA7444CBFC426D, 0x99C102844F94E0FB}, // 1e-257
+	{0xFA911155FEFB5308, 0xC0314325637A1939}, // 1e-256
+	{0x793555AB7EBA27CA, 0xF03D93EEBC589F88}, // 1e-255
+	{0x4BC1558B2F3458DE, 0x96267C7535B763B5}, // 1e-254
+	{0x9EB1AAEDFB016F16, 0xBBB01B9283253CA2}, // 1e-253
+	{0x465E15A979C1CADC, 0xEA9C227723EE8BCB}, // 1e-252
+	{0x0BFACD89EC191EC9, 0x92A1958A7675175F}, // 1e-251
+	{0xCEF980EC671F667B, 0xB749FAED14125D36}, // 1e-250
+	{0x82B7E12780E7401A, 0xE51C79A85916F484}, // 1e-249
+	{0xD1B2ECB8B0908810, 0x8F31CC0937AE58D2}, // 1e-248
+	{0x861FA7E6DCB4AA15, 0xB2FE3F0B8599EF07}, // 1e-247
+	{0x67A791E093E1D49A, 0xDFBDCECE67006AC9}, // 1e-246
+	{0xE0C8BB2C5C6D24E0, 0x8BD6A141006042BD}, // 1e-245
+	{0x58FAE9F773886E18, 0xAECC49914078536D}, // 1e-244
+	{0xAF39A475506A899E, 0xDA7F5BF590966848}, // 1e-243
+	{0x6D8406C952429603, 0x888F99797A5E012D}, // 1e-242
+	{0xC8E5087BA6D33B83, 0xAAB37FD7D8F58178}, // 1e-241
+	{0xFB1E4A9A90880A64, 0xD5605FCDCF32E1D6}, // 1e-240
+	{0x5CF2EEA09A55067F, 0x855C3BE0A17FCD26}, // 1e-239
+	{0xF42FAA48C0EA481E, 0xA6B34AD8C9DFC06F}, // 1e-238
+	{0xF13B94DAF124DA26, 0xD0601D8EFC57B08B}, // 1e-237
+	{0x76C53D08D6B70858, 0x823C12795DB6CE57}, // 1e-236
+	{0x54768C4B0C64CA6E, 0xA2CB1717B52481ED}, // 1e-235
+	{0xA9942F5DCF7DFD09, 0xCB7DDCDDA26DA268}, // 1e-234
+	{0xD3F93B35435D7C4C, 0xFE5D54150B090B02}, // 1e-233
+	{0xC47BC5014A1A6DAF, 0x9EFA548D26E5A6E1}, // 1e-232
+	{0x359AB6419CA1091B, 0xC6B8E9B0709F109A}, // 1e-231
+	{0xC30163D203C94B62, 0xF867241C8CC6D4C0}, // 1e-230
+	{0x79E0DE63425DCF1D, 0x9B407691D7FC44F8}, // 1e-229
+	{0x985915FC12F542E4, 0xC21094364DFB5636}, // 1e-228
+	{0x3E6F5B7B17B2939D, 0xF294B943E17A2BC4}, // 1e-227
+	{0xA705992CEECF9C42, 0x979CF3CA6CEC5B5A}, // 1e-226
+	{0x50C6FF782A838353, 0xBD8430BD08277231}, // 1e-225
+	{0xA4F8BF5635246428, 0xECE53CEC4A314EBD}, // 1e-224
+	{0x871B7795E136BE99, 0x940F4613AE5ED136}, // 1e-223
+	{0x28E2557B59846E3F, 0xB913179899F68584}, // 1e-222
+	{0x331AEADA2FE589CF, 0xE757DD7EC07426E5}, // 1e-221
+	{0x3FF0D2C85DEF7621, 0x9096EA6F3848984F}, // 1e-220
+	{0x0FED077A756B53A9, 0xB4BCA50B065ABE63}, // 1e-219
+	{0xD3E8495912C62894, 0xE1EBCE4DC7F16DFB}, // 1e-218
+	{0x64712DD7ABBBD95C, 0x8D3360F09CF6E4BD}, // 1e-217
+	{0xBD8D794D96AACFB3, 0xB080392CC4349DEC}, // 1e-216
+	{0xECF0D7A0FC5583A0, 0xDCA04777F541C567}, // 1e-215
+	{0xF41686C49DB57244, 0x89E42CAAF9491B60}, // 1e-214
+	{0x311C2875C522CED5, 0xAC5D37D5B79B6239}, // 1e-213
+	{0x7D633293366B828B, 0xD77485CB25823AC7}, // 1e-212
+	{0xAE5DFF9C02033197, 0x86A8D39EF77164BC}, // 1e-211
+	{0xD9F57F830283FDFC, 0xA8530886B54DBDEB}, // 1e-210
+	{0xD072DF63C324FD7B, 0xD267CAA862A12D66}, // 1e-209
+	{0x4247CB9E59F71E6D, 0x8380DEA93DA4BC60}, // 1e-208
+	{0x52D9BE85F074E608, 0xA46116538D0DEB78}, // 1e-207
+	{0x67902E276C921F8B, 0xCD795BE870516656}, // 1e-206
+	{0x00BA1CD8A3DB53B6, 0x806BD9714632DFF6}, // 1e-205
+	{0x80E8A40ECCD228A4, 0xA086CFCD97BF97F3}, // 1e-204
+	{0x6122CD128006B2CD, 0xC8A883C0FDAF7DF0}, // 1e-203
+	{0x796B805720085F81, 0xFAD2A4B13D1B5D6C}, // 1e-202
+	{0xCBE3303674053BB0, 0x9CC3A6EEC6311A63}, // 1e-201
+	{0xBEDBFC4411068A9C, 0xC3F490AA77BD60FC}, // 1e-200
+	{0xEE92FB5515482D44, 0xF4F1B4D515ACB93B}, // 1e-199
+	{0x751BDD152D4D1C4A, 0x991711052D8BF3C5}, // 1e-198
+	{0xD262D45A78A0635D, 0xBF5CD54678EEF0B6}, // 1e-197
+	{0x86FB897116C87C34, 0xEF340A98172AACE4}, // 1e-196
+	{0xD45D35E6AE3D4DA0, 0x9580869F0E7AAC0E}, // 1e-195
+	{0x8974836059CCA109, 0xBAE0A846D2195712}, // 1e-194
+	{0x2BD1A438703FC94B, 0xE998D258869FACD7}, // 1e-193
+	{0x7B6306A34627DDCF, 0x91FF83775423CC06}, // 1e-192
+	{0x1A3BC84C17B1D542, 0xB67F6455292CBF08}, // 1e-191
+	{0x20CABA5F1D9E4A93, 0xE41F3D6A7377EECA}, // 1e-190
+	{0x547EB47B7282EE9C, 0x8E938662882AF53E}, // 1e-189
+	{0xE99E619A4F23AA43, 0xB23867FB2A35B28D}, // 1e-188
+	{0x6405FA00E2EC94D4, 0xDEC681F9F4C31F31}, // 1e-187
+	{0xDE83BC408DD3DD04, 0x8B3C113C38F9F37E}, // 1e-186
+	{0x9624AB50B148D445, 0xAE0B158B4738705E}, // 1e-185
+	{0x3BADD624DD9B0957, 0xD98DDAEE19068C76}, // 1e-184
+	{0xE54CA5D70A80E5D6, 0x87F8A8D4CFA417C9}, // 1e-183
+	{0x5E9FCF4CCD211F4C, 0xA9F6D30A038D1DBC}, // 1e-182
+	{0x7647C3200069671F, 0xD47487CC8470652B}, // 1e-181
+	{0x29ECD9F40041E073, 0x84C8D4DFD2C63F3B}, // 1e-180
+	{0xF468107100525890, 0xA5FB0A17C777CF09}, // 1e-179
+	{0x7182148D4066EEB4, 0xCF79CC9DB955C2CC}, // 1e-178
+	{0xC6F14CD848405530, 0x81AC1FE293D599BF}, // 1e-177
+	{0xB8ADA00E5A506A7C, 0xA21727DB38CB002F}, // 1e-176
+	{0xA6D90811F0E4851C, 0xCA9CF1D206FDC03B}, // 1e-175
+	{0x908F4A166D1DA663, 0xFD442E4688BD304A}, // 1e-174
+	{0x9A598E4E043287FE, 0x9E4A9CEC15763E2E}, // 1e-173
+	{0x40EFF1E1853F29FD, 0xC5DD44271AD3CDBA}, // 1e-172
+	{0xD12BEE59E68EF47C, 0xF7549530E188C128}, // 1e-171
+	{0x82BB74F8301958CE, 0x9A94DD3E8CF578B9}, // 1e-170
+	{0xE36A52363C1FAF01, 0xC13A148E3032D6E7}, // 1e-169
+	{0xDC44E6C3CB279AC1, 0xF18899B1BC3F8CA1}, // 1e-168
+	{0x29AB103A5EF8C0B9, 0x96F5600F15A7B7E5}, // 1e-167
+	{0x7415D448F6B6F0E7, 0xBCB2B812DB11A5DE}, // 1e-166
+	{0x111B495B3464AD21, 0xEBDF661791D60F56}, // 1e-165
+	{0xCAB10DD900BEEC34, 0x936B9FCEBB25C995}, // 1e-164
+	{0x3D5D514F40EEA742, 0xB84687C269EF3BFB}, // 1e-163
+	{0x0CB4A5A3112A5112, 0xE65829B3046B0AFA}, // 1e-162
+	{0x47F0E785EABA72AB, 0x8FF71A0FE2C2E6DC}, // 1e-161
+	{0x59ED216765690F56, 0xB3F4E093DB73A093}, // 1e-160
+	{0x306869C13EC3532C, 0xE0F218B8D25088B8}, // 1e-159
+	{0x1E414218C73A13FB, 0x8C974F7383725573}, // 1e-158
+	{0xE5D1929EF90898FA, 0xAFBD2350644EEACF}, // 1e-157
+	{0xDF45F746B74ABF39, 0xDBAC6C247D62A583}, // 1e-156
+	{0x6B8BBA8C328EB783, 0x894BC396CE5DA772}, // 1e-155
+	{0x066EA92F3F326564, 0xAB9EB47C81F5114F}, // 1e-154
+	{0xC80A537B0EFEFEBD, 0xD686619BA27255A2}, // 1e-153
+	{0xBD06742CE95F5F36, 0x8613FD0145877585}, // 1e-152
+	{0x2C48113823B73704, 0xA798FC4196E952E7}, // 1e-151
+	{0xF75A15862CA504C5, 0xD17F3B51FCA3A7A0}, // 1e-150
+	{0x9A984D73DBE722FB, 0x82EF85133DE648C4}, // 1e-149
+	{0xC13E60D0D2E0EBBA, 0xA3AB66580D5FDAF5}, // 1e-148
+	{0x318DF905079926A8, 0xCC963FEE10B7D1B3}, // 1e-147
+	{0xFDF17746497F7052, 0xFFBBCFE994E5C61F}, // 1e-146
+	{0xFEB6EA8BEDEFA633, 0x9FD561F1FD0F9BD3}, // 1e-145
+	{0xFE64A52EE96B8FC0, 0xC7CABA6E7C5382C8}, // 1e-144
+	{0x3DFDCE7AA3C673B0, 0xF9BD690A1B68637B}, // 1e-143
+	{0x06BEA10CA65C084E, 0x9C1661A651213E2D}, // 1e-142
+	{0x486E494FCFF30A62, 0xC31BFA0FE5698DB8}, // 1e-141
+	{0x5A89DBA3C3EFCCFA, 0xF3E2F893DEC3F126}, // 1e-140
+	{0xF89629465A75E01C, 0x986DDB5C6B3A76B7}, // 1e-139
+	{0xF6BBB397F1135823, 0xBE89523386091465}, // 1e-138
+	{0x746AA07DED582E2C, 0xEE2BA6C0678B597F}, // 1e-137
+	{0xA8C2A44EB4571CDC, 0x94DB483840B717EF}, // 1e-136
+	{0x92F34D62616CE413, 0xBA121A4650E4DDEB}, // 1e-135
+	{0x77B020BAF9C81D17, 0xE896A0D7E51E1566}, // 1e-134
+	{0x0ACE1474DC1D122E, 0x915E2486EF32CD60}, // 1e-133
+	{0x0D819992132456BA, 0xB5B5ADA8AAFF80B8}, // 1e-132
+	{0x10E1FFF697ED6C69, 0xE3231912D5BF60E6}, // 1e-131
+	{0xCA8D3FFA1EF463C1, 0x8DF5EFABC5979C8F}, // 1e-130
+	{0xBD308FF8A6B17CB2, 0xB1736B96B6FD83B3}, // 1e-129
+	{0xAC7CB3F6D05DDBDE, 0xDDD0467C64BCE4A0}, // 1e-128
+	{0x6BCDF07A423AA96B, 0x8AA22C0DBEF60EE4}, // 1e-127
+	{0x86C16C98D2C953C6, 0xAD4AB7112EB3929D}, // 1e-126
+	{0xE871C7BF077BA8B7, 0xD89D64D57A607744}, // 1e-125
+	{0x11471CD764AD4972, 0x87625F056C7C4A8B}, // 1e-124
+	{0xD598E40D3DD89BCF, 0xA93AF6C6C79B5D2D}, // 1e-123
+	{0x4AFF1D108D4EC2C3, 0xD389B47879823479}, // 1e-122
+	{0xCEDF722A585139BA, 0x843610CB4BF160CB}, // 1e-121
+	{0xC2974EB4EE658828, 0xA54394FE1EEDB8FE}, // 1e-120
+	{0x733D226229FEEA32, 0xCE947A3DA6A9273E}, // 1e-119
+	{0x0806357D5A3F525F, 0x811CCC668829B887}, // 1e-118
+	{0xCA07C2DCB0CF26F7, 0xA163FF802A3426A8}, // 1e-117
+	{0xFC89B393DD02F0B5, 0xC9BCFF6034C13052}, // 1e-116
+	{0xBBAC2078D443ACE2, 0xFC2C3F3841F17C67}, // 1e-115
+	{0xD54B944B84AA4C0D, 0x9D9BA7832936EDC0}, // 1e-114
+	{0x0A9E795E65D4DF11, 0xC5029163F384A931}, // 1e-113
+	{0x4D4617B5FF4A16D5, 0xF64335BCF065D37D}, // 1e-112
+	{0x504BCED1BF8E4E45, 0x99EA0196163FA42E}, // 1e-111
+	{0xE45EC2862F71E1D6, 0xC06481FB9BCF8D39}, // 1e-110
+	{0x5D767327BB4E5A4C, 0xF07DA27A82C37088}, // 1e-109
+	{0x3A6A07F8D510F86F, 0x964E858C91BA2655}, // 1e-108
+	{0x890489F70A55368B, 0xBBE226EFB628AFEA}, // 1e-107
+	{0x2B45AC74CCEA842E, 0xEADAB0ABA3B2DBE5}, // 1e-106
+	{0x3B0B8BC90012929D, 0x92C8AE6B464FC96F}, // 1e-105
+	{0x09CE6EBB40173744, 0xB77ADA0617E3BBCB}, // 1e-104
+	{0xCC420A6A101D0515, 0xE55990879DDCAABD}, // 1e-103
+	{0x9FA946824A12232D, 0x8F57FA54C2A9EAB6}, // 1e-102
+	{0x47939822DC96ABF9, 0xB32DF8E9F3546564}, // 1e-101
+	{0x59787E2B93BC56F7, 0xDFF9772470297EBD}, // 1e-100
+	{0x57EB4EDB3C55B65A, 0x8BFBEA76C619EF36}, // 1e-99
+	{0xEDE622920B6B23F1, 0xAEFAE51477A06B03}, // 1e-98
+	{0xE95FAB368E45ECED, 0xDAB99E59958885C4}, // 1e-97
+	{0x11DBCB0218EBB414, 0x88B402F7FD75539B}, // 1e-96
+	{0xD652BDC29F26A119, 0xAAE103B5FCD2A881}, // 1e-95
+	{0x4BE76D3346F0495F, 0xD59944A37C0752A2}, // 1e-94
+	{0x6F70A4400C562DDB, 0x857FCAE62D8493A5}, // 1e-93
+	{0xCB4CCD500F6BB952, 0xA6DFBD9FB8E5B88E}, // 1e-92
+	{0x7E2000A41346A7A7, 0xD097AD07A71F26B2}, // 1e-91
+	{0x8ED400668C0C28C8, 0x825ECC24C873782F}, // 1e-90
+	{0x728900802F0F32FA, 0xA2F67F2DFA90563B}, // 1e-89
+	{0x4F2B40A03AD2FFB9, 0xCBB41EF979346BCA}, // 1e-88
+	{0xE2F610C84987BFA8, 0xFEA126B7D78186BC}, // 1e-87
+	{0x0DD9CA7D2DF4D7C9, 0x9F24B832E6B0F436}, // 1e-86
+	{0x91503D1C79720DBB, 0xC6EDE63FA05D3143}, // 1e-85
+	{0x75A44C6397CE912A, 0xF8A95FCF88747D94}, // 1e-84
+	{0xC986AFBE3EE11ABA, 0x9B69DBE1B548CE7C}, // 1e-83
+	{0xFBE85BADCE996168, 0xC24452DA229B021B}, // 1e-82
+	{0xFAE27299423FB9C3, 0xF2D56790AB41C2A2}, // 1e-81
+	{0xDCCD879FC967D41A, 0x97C560BA6B0919A5}, // 1e-80
+	{0x5400E987BBC1C920, 0xBDB6B8E905CB600F}, // 1e-79
+	{0x290123E9AAB23B68, 0xED246723473E3813}, // 1e-78
+	{0xF9A0B6720AAF6521, 0x9436C0760C86E30B}, // 1e-77
+	{0xF808E40E8D5B3E69, 0xB94470938FA89BCE}, // 1e-76
+	{0xB60B1D1230B20E04, 0xE7958CB87392C2C2}, // 1e-75
+	{0xB1C6F22B5E6F48C2, 0x90BD77F3483BB9B9}, // 1e-74
+	{0x1E38AEB6360B1AF3, 0xB4ECD5F01A4AA828}, // 1e-73
+	{0x25C6DA63C38DE1B0, 0xE2280B6C20DD5232}, // 1e-72
+	{0x579C487E5A38AD0E, 0x8D590723948A535F}, // 1e-71
+	{0x2D835A9DF0C6D851, 0xB0AF48EC79ACE837}, // 1e-70
+	{0xF8E431456CF88E65, 0xDCDB1B2798182244}, // 1e-69
+	{0x1B8E9ECB641B58FF, 0x8A08F0F8BF0F156B}, // 1e-68
+	{0xE272467E3D222F3F, 0xAC8B2D36EED2DAC5}, // 1e-67
+	{0x5B0ED81DCC6ABB0F, 0xD7ADF884AA879177}, // 1e-66
+	{0x98E947129FC2B4E9, 0x86CCBB52EA94BAEA}, // 1e-65
+	{0x3F2398D747B36224, 0xA87FEA27A539E9A5}, // 1e-64
+	{0x8EEC7F0D19A03AAD, 0xD29FE4B18E88640E}, // 1e-63
+	{0x1953CF68300424AC, 0x83A3EEEEF9153E89}, // 1e-62
+	{0x5FA8C3423C052DD7, 0xA48CEAAAB75A8E2B}, // 1e-61
+	{0x3792F412CB06794D, 0xCDB02555653131B6}, // 1e-60
+	{0xE2BBD88BBEE40BD0, 0x808E17555F3EBF11}, // 1e-59
+	{0x5B6ACEAEAE9D0EC4, 0xA0B19D2AB70E6ED6}, // 1e-58
+	{0xF245825A5A445275, 0xC8DE047564D20A8B}, // 1e-57
+	{0xEED6E2F0F0D56712, 0xFB158592BE068D2E}, // 1e-56
+	{0x55464DD69685606B, 0x9CED737BB6C4183D}, // 1e-55
+	{0xAA97E14C3C26B886, 0xC428D05AA4751E4C}, // 1e-54
+	{0xD53DD99F4B3066A8, 0xF53304714D9265DF}, // 1e-53
+	{0xE546A8038EFE4029, 0x993FE2C6D07B7FAB}, // 1e-52
+	{0xDE98520472BDD033, 0xBF8FDB78849A5F96}, // 1e-51
+	{0x963E66858F6D4440, 0xEF73D256A5C0F77C}, // 1e-50
+	{0xDDE7001379A44AA8, 0x95A8637627989AAD}, // 1e-49
+	{0x5560C018580D5D52, 0xBB127C53B17EC159}, // 1e-48
+	{0xAAB8F01E6E10B4A6, 0xE9D71B689DDE71AF}, // 1e-47
+	{0xCAB3961304CA70E8, 0x9226712162AB070D}, // 1e-46
+	{0x3D607B97C5FD0D22, 0xB6B00D69BB55C8D1}, // 1e-45
+	{0x8CB89A7DB77C506A, 0xE45C10C42A2B3B05}, // 1e-44
+	{0x77F3608E92ADB242, 0x8EB98A7A9A5B04E3}, // 1e-43
+	{0x55F038B237591ED3, 0xB267ED1940F1C61C}, // 1e-42
+	{0x6B6C46DEC52F6688, 0xDF01E85F912E37A3}, // 1e-41
+	{0x2323AC4B3B3DA015, 0x8B61313BBABCE2C6}, // 1e-40
+	{0xABEC975E0A0D081A, 0xAE397D8AA96C1B77}, // 1e-39
+	{0x96E7BD358C904A21, 0xD9C7DCED53C72255}, // 1e-38
+	{0x7E50D64177DA2E54, 0x881CEA14545C7575}, // 1e-37
+	{0xDDE50BD1D5D0B9E9, 0xAA242499697392D2}, // 1e-36
+	{0x955E4EC64B44E864, 0xD4AD2DBFC3D07787}, // 1e-35
+	{0xBD5AF13BEF0B113E, 0x84EC3C97DA624AB4}, // 1e-34
+	{0xECB1AD8AEACDD58E, 0xA6274BBDD0FADD61}, // 1e-33
+	{0x67DE18EDA5814AF2, 0xCFB11EAD453994BA}, // 1e-32
+	{0x80EACF948770CED7, 0x81CEB32C4B43FCF4}, // 1e-31
+	{0xA1258379A94D028D, 0xA2425FF75E14FC31}, // 1e-30
+	{0x096EE45813A04330, 0xCAD2F7F5359A3B3E}, // 1e-29
+	{0x8BCA9D6E188853FC, 0xFD87B5F28300CA0D}, // 1e-28
+	{0x775EA264CF55347D, 0x9E74D1B791E07E48}, // 1e-27
+	{0x95364AFE032A819D, 0xC612062576589DDA}, // 1e-26
+	{0x3A83DDBD83F52204, 0xF79687AED3EEC551}, // 1e-25
+	{0xC4926A9672793542, 0x9ABE14CD44753B52}, // 1e-24
+	{0x75B7053C0F178293, 0xC16D9A0095928A27}, // 1e-23
+	{0x5324C68B12DD6338, 0xF1C90080BAF72CB1}, // 1e-22
+	{0xD3F6FC16EBCA5E03, 0x971DA05074DA7BEE}, // 1e-21
+	{0x88F4BB1CA6BCF584, 0xBCE5086492111AEA}, // 1e-20
+	{0x2B31E9E3D06C32E5, 0xEC1E4A7DB69561A5}, // 1e-19
+	{0x3AFF322E62439FCF, 0x9392EE8E921D5D07}, // 1e-18
+	{0x09BEFEB9FAD487C2, 0xB877AA3236A4B449}, // 1e-17
+	{0x4C2EBE687989A9B3, 0xE69594BEC44DE15B}, // 1e-16
+	{0x0F9D37014BF60A10, 0x901D7CF73AB0ACD9}, // 1e-15
+	{0x538484C19EF38C94, 0xB424DC35095CD80F}, // 1e-14
+	{0x2865A5F206B06FB9, 0xE12E13424BB40E13}, // 1e-13
+	{0xF93F87B7442E45D3, 0x8CBCCC096F5088CB}, // 1e-12
+	{0xF78F69A51539D748, 0xAFEBFF0BCB24AAFE}, // 1e-11
+	{0xB573440E5A884D1B, 0xDBE6FECEBDEDD5BE}, // 1e-10
+	{0x31680A88F8953030, 0x89705F4136B4A597}, // 1e-9
+	{0xFDC20D2B36BA7C3D, 0xABCC77118461CEFC}, // 1e-8
+	{0x3D32907604691B4C, 0xD6BF94D5E57A42BC}, // 1e-7
+	{0xA63F9A49C2C1B10F, 0x8637BD05AF6C69B5}, // 1e-6
+	{0x0FCF80DC33721D53, 0xA7C5AC471B478423}, // 1e-5
+	{0xD3C36113404EA4A8, 0xD1B71758E219652B}, // 1e-4
+	{0x645A1CAC083126E9, 0x83126E978D4FDF3B}, // 1e-3
+	{0x3D70A3D70A3D70A3, 0xA3D70A3D70A3D70A}, // 1e-2
+	{0xCCCCCCCCCCCCCCCC, 0xCCCCCCCCCCCCCCCC}, // 1e-1
+	{0x0000000000000000, 0x8000000000000000}, // 1e0
+	{0x0000000000000000, 0xA000000000000000}, // 1e1
+	{0x0000000000000000, 0xC800000000000000}, // 1e2
+	{0x0000000000000000, 0xFA00000000000000}, // 1e3
+	{0x0000000000000000, 0x9C40000000000000}, // 1e4
+	{0x0000000000000000, 0xC350000000000000}, // 1e5
+	{0x0000000000000000, 0xF424000000000000}, // 1e6
+	{0x0000000000000000, 0x9896800000000000}, // 1e7
+	{0x0000000000000000, 0xBEBC200000000000}, // 1e8
+	{0x0000000000000000, 0xEE6B280000000000}, // 1e9
+	{0x0000000000000000, 0x9502F90000000000}, // 1e10
+	{0x0000000000000000, 0xBA43B74000000000}, // 1e11
+	{0x0000000000000000, 0xE8D4A51000000000}, // 1e12
+	{0x0000000000000000, 0x9184E72A00000000}, // 1e13
+	{0x0000000000000000, 0xB5E620F480000000}, // 1e14
+	{0x0000000000000000, 0xE35FA931A0000000}, // 1e15
+	{0x0000000000000000, 0x8E1BC9BF04000000}, // 1e16
+	{0x0000000000000000, 0xB1A2BC2EC5000000}, // 1e17
+	{0x0000000000000000, 0xDE0B6B3A76400000}, // 1e18
+	{0x0000000000000000, 0x8AC7230489E80000}, // 1e19
+	{0x0000000000000000, 0xAD78EBC5AC620000}, // 1e20
+	{0x0000000000000000, 0xD8D726B7177A8000}, // 1e21
+	{0x0000000000000000, 0x878678326EAC9000}, // 1e22
+	{0x0000000000000000, 0xA968163F0A57B400}, // 1e23
+	{0x0000000000000000, 0xD3C21BCECCEDA100}, // 1e24
+	{0x0000000000000000, 0x84595161401484A0}, // 1e25
+	{0x0000000000000000, 0xA56FA5B99019A5C8}, // 1e26
+	{0x0000000000000000, 0xCECB8F27F4200F3A}, // 1e27
+	{0x4000000000000000, 0x813F3978F8940984}, // 1e28
+	{0x5000000000000000, 0xA18F07D736B90BE5}, // 1e29
+	{0xA400000000000000, 0xC9F2C9CD04674EDE}, // 1e30
+	{0x4D00000000000000, 0xFC6F7C4045812296}, // 1e31
+	{0xF020000000000000, 0x9DC5ADA82B70B59D}, // 1e32
+	{0x6C28000000000000, 0xC5371912364CE305}, // 1e33
+	{0xC732000000000000, 0xF684DF56C3E01BC6}, // 1e34
+	{0x3C7F400000000000, 0x9A130B963A6C115C}, // 1e35
+	{0x4B9F100000000000, 0xC097CE7BC90715B3}, // 1e36
+	{0x1E86D40000000000, 0xF0BDC21ABB48DB20}, // 1e37
+	{0x1314448000000000, 0x96769950B50D88F4}, // 1e38
+	{0x17D955A000000000, 0xBC143FA4E250EB31}, // 1e39
+	{0x5DCFAB0800000000, 0xEB194F8E1AE525FD}, // 1e40
+	{0x5AA1CAE500000000, 0x92EFD1B8D0CF37BE}, // 1e41
+	{0xF14A3D9E40000000, 0xB7ABC627050305AD}, // 1e42
+	{0x6D9CCD05D0000000, 0xE596B7B0C643C719}, // 1e43
+	{0xE4820023A2000000, 0x8F7E32CE7BEA5C6F}, // 1e44
+	{0xDDA2802C8A800000, 0xB35DBF821AE4F38B}, // 1e45
+	{0xD50B2037AD200000, 0xE0352F62A19E306E}, // 1e46
+	{0x4526F422CC340000, 0x8C213D9DA502DE45}, // 1e47
+	{0x9670B12B7F410000, 0xAF298D050E4395D6}, // 1e48
+	{0x3C0CDD765F114000, 0xDAF3F04651D47B4C}, // 1e49
+	{0xA5880A69FB6AC800, 0x88D8762BF324CD0F}, // 1e50
+	{0x8EEA0D047A457A00, 0xAB0E93B6EFEE0053}, // 1e51
+	{0x72A4904598D6D880, 0xD5D238A4ABE98068}, // 1e52
+	{0x47A6DA2B7F864750, 0x85A36366EB71F041}, // 1e53
+	{0x999090B65F67D924, 0xA70C3C40A64E6C51}, // 1e54
+	{0xFFF4B4E3F741CF6D, 0xD0CF4B50CFE20765}, // 1e55
+	{0xBFF8F10E7A8921A4, 0x82818F1281ED449F}, // 1e56
+	{0xAFF72D52192B6A0D, 0xA321F2D7226895C7}, // 1e57
+	{0x9BF4F8A69F764490, 0xCBEA6F8CEB02BB39}, // 1e58
+	{0x02F236D04753D5B4, 0xFEE50B7025C36A08}, // 1e59
+	{0x01D762422C946590, 0x9F4F2726179A2245}, // 1e60
+	{0x424D3AD2B7B97EF5, 0xC722F0EF9D80AAD6}, // 1e61
+	{0xD2E0898765A7DEB2, 0xF8EBAD2B84E0D58B}, // 1e62
+	{0x63CC55F49F88EB2F, 0x9B934C3B330C8577}, // 1e63
+	{0x3CBF6B71C76B25FB, 0xC2781F49FFCFA6D5}, // 1e64
+	{0x8BEF464E3945EF7A, 0xF316271C7FC3908A}, // 1e65
+	{0x97758BF0E3CBB5AC, 0x97EDD871CFDA3A56}, // 1e66
+	{0x3D52EEED1CBEA317, 0xBDE94E8E43D0C8EC}, // 1e67
+	{0x4CA7AAA863EE4BDD, 0xED63A231D4C4FB27}, // 1e68
+	{0x8FE8CAA93E74EF6A, 0x945E455F24FB1CF8}, // 1e69
+	{0xB3E2FD538E122B44, 0xB975D6B6EE39E436}, // 1e70
+	{0x60DBBCA87196B616, 0xE7D34C64A9C85D44}, // 1e71
+	{0xBC8955E946FE31CD, 0x90E40FBEEA1D3A4A}, // 1e72
+	{0x6BABAB6398BDBE41, 0xB51D13AEA4A488DD}, // 1e73
+	{0xC696963C7EED2DD1, 0xE264589A4DCDAB14}, // 1e74
+	{0xFC1E1DE5CF543CA2, 0x8D7EB76070A08AEC}, // 1e75
+	{0x3B25A55F43294BCB, 0xB0DE65388CC8ADA8}, // 1e76
+	{0x49EF0EB713F39EBE, 0xDD15FE86AFFAD912}, // 1e77
+	{0x6E3569326C784337, 0x8A2DBF142DFCC7AB}, // 1e78
+	{0x49C2C37F07965404, 0xACB92ED9397BF996}, // 1e79
+	{0xDC33745EC97BE906, 0xD7E77A8F87DAF7FB}, // 1e80
+	{0x69A028BB3DED71A3, 0x86F0AC99B4E8DAFD}, // 1e81
+	{0xC40832EA0D68CE0C, 0xA8ACD7C0222311BC}, // 1e82
+	{0xF50A3FA490C30190, 0xD2D80DB02AABD62B}, // 1e83
+	{0x792667C6DA79E0FA, 0x83C7088E1AAB65DB}, // 1e84
+	{0x577001B891185938, 0xA4B8CAB1A1563F52}, // 1e85
+	{0xED4C0226B55E6F86, 0xCDE6FD5E09ABCF26}, // 1e86
+	{0x544F8158315B05B4, 0x80B05E5AC60B6178}, // 1e87
+	{0x696361AE3DB1C721, 0xA0DC75F1778E39D6}, // 1e88
+	{0x03BC3A19CD1E38E9, 0xC913936DD571C84C}, // 1e89
+	{0x04AB48A04065C723, 0xFB5878494ACE3A5F}, // 1e90
+	{0x62EB0D64283F9C76, 0x9D174B2DCEC0E47B}, // 1e91
+	{0x3BA5D0BD324F8394, 0xC45D1DF942711D9A}, // 1e92
+	{0xCA8F44EC7EE36479, 0xF5746577930D6500}, // 1e93
+	{0x7E998B13CF4E1ECB, 0x9968BF6ABBE85F20}, // 1e94
+	{0x9E3FEDD8C321A67E, 0xBFC2EF456AE276E8}, // 1e95
+	{0xC5CFE94EF3EA101E, 0xEFB3AB16C59B14A2}, // 1e96
+	{0xBBA1F1D158724A12, 0x95D04AEE3B80ECE5}, // 1e97
+	{0x2A8A6E45AE8EDC97, 0xBB445DA9CA61281F}, // 1e98
+	{0xF52D09D71A3293BD, 0xEA1575143CF97226}, // 1e99
+	{0x593C2626705F9C56, 0x924D692CA61BE758}, // 1e100
+	{0x6F8B2FB00C77836C, 0xB6E0C377CFA2E12E}, // 1e101
+	{0x0B6DFB9C0F956447, 0xE498F455C38B997A}, // 1e102
+	{0x4724BD4189BD5EAC, 0x8EDF98B59A373FEC}, // 1e103
+	{0x58EDEC91EC2CB657, 0xB2977EE300C50FE7}, // 1e104
+	{0x2F2967B66737E3ED, 0xDF3D5E9BC0F653E1}, // 1e105
+	{0xBD79E0D20082EE74, 0x8B865B215899F46C}, // 1e106
+	{0xECD8590680A3AA11, 0xAE67F1E9AEC07187}, // 1e107
+	{0xE80E6F4820CC9495, 0xDA01EE641A708DE9}, // 1e108
+	{0x3109058D147FDCDD, 0x884134FE908658B2}, // 1e109
+	{0xBD4B46F0599FD415, 0xAA51823E34A7EEDE}, // 1e110
+	{0x6C9E18AC7007C91A, 0xD4E5E2CDC1D1EA96}, // 1e111
+	{0x03E2CF6BC604DDB0, 0x850FADC09923329E}, // 1e112
+	{0x84DB8346B786151C, 0xA6539930BF6BFF45}, // 1e113
+	{0xE612641865679A63, 0xCFE87F7CEF46FF16}, // 1e114
+	{0x4FCB7E8F3F60C07E, 0x81F14FAE158C5F6E}, // 1e115
+	{0xE3BE5E330F38F09D, 0xA26DA3999AEF7749}, // 1e116
+	{0x5CADF5BFD3072CC5, 0xCB090C8001AB551C}, // 1e117
+	{0x73D9732FC7C8F7F6, 0xFDCB4FA002162A63}, // 1e118
+	{0x2867E7FDDCDD9AFA, 0x9E9F11C4014DDA7E}, // 1e119
+	{0xB281E1FD541501B8, 0xC646D63501A1511D}, // 1e120
+	{0x1F225A7CA91A4226, 0xF7D88BC24209A565}, // 1e121
+	{0x3375788DE9B06958, 0x9AE757596946075F}, // 1e122
+	{0x0052D6B1641C83AE, 0xC1A12D2FC3978937}, // 1e123
+	{0xC0678C5DBD23A49A, 0xF209787BB47D6B84}, // 1e124
+	{0xF840B7BA963646E0, 0x9745EB4D50CE6332}, // 1e125
+	{0xB650E5A93BC3D898, 0xBD176620A501FBFF}, // 1e126
+	{0xA3E51F138AB4CEBE, 0xEC5D3FA8CE427AFF}, // 1e127
+	{0xC66F336C36B10137, 0x93BA47C980E98CDF}, // 1e128
+	{0xB80B0047445D4184, 0xB8A8D9BBE123F017}, // 1e129
+	{0xA60DC059157491E5, 0xE6D3102AD96CEC1D}, // 1e130
+	{0x87C89837AD68DB2F, 0x9043EA1AC7E41392}, // 1e131
+	{0x29BABE4598C311FB, 0xB454E4A179DD1877}, // 1e132
+	{0xF4296DD6FEF3D67A, 0xE16A1DC9D8545E94}, // 1e133
+	{0x1899E4A65F58660C, 0x8CE2529E2734BB1D}, // 1e134
+	{0x5EC05DCFF72E7F8F, 0xB01AE745B101E9E4}, // 1e135
+	{0x76707543F4FA1F73, 0xDC21A1171D42645D}, // 1e136
+	{0x6A06494A791C53A8, 0x899504AE72497EBA}, // 1e137
+	{0x0487DB9D17636892, 0xABFA45DA0EDBDE69}, // 1e138
+	{0x45A9D2845D3C42B6, 0xD6F8D7509292D603}, // 1e139
+	{0x0B8A2392BA45A9B2, 0x865B86925B9BC5C2}, // 1e140
+	{0x8E6CAC7768D7141E, 0xA7F26836F282B732}, // 1e141
+	{0x3207D795430CD926, 0xD1EF0244AF2364FF}, // 1e142
+	{0x7F44E6BD49E807B8, 0x8335616AED761F1F}, // 1e143
+	{0x5F16206C9C6209A6, 0xA402B9C5A8D3A6E7}, // 1e144
+	{0x36DBA887C37A8C0F, 0xCD036837130890A1}, // 1e145
+	{0xC2494954DA2C9789, 0x802221226BE55A64}, // 1e146
+	{0xF2DB9BAA10B7BD6C, 0xA02AA96B06DEB0FD}, // 1e147
+	{0x6F92829494E5ACC7, 0xC83553C5C8965D3D}, // 1e148
+	{0xCB772339BA1F17F9, 0xFA42A8B73ABBF48C}, // 1e149
+	{0xFF2A760414536EFB, 0x9C69A97284B578D7}, // 1e150
+	{0xFEF5138519684ABA, 0xC38413CF25E2D70D}, // 1e151
+	{0x7EB258665FC25D69, 0xF46518C2EF5B8CD1}, // 1e152
+	{0xEF2F773FFBD97A61, 0x98BF2F79D5993802}, // 1e153
+	{0xAAFB550FFACFD8FA, 0xBEEEFB584AFF8603}, // 1e154
+	{0x95BA2A53F983CF38, 0xEEAABA2E5DBF6784}, // 1e155
+	{0xDD945A747BF26183, 0x952AB45CFA97A0B2}, // 1e156
+	{0x94F971119AEEF9E4, 0xBA756174393D88DF}, // 1e157
+	{0x7A37CD5601AAB85D, 0xE912B9D1478CEB17}, // 1e158
+	{0xAC62E055C10AB33A, 0x91ABB422CCB812EE}, // 1e159
+	{0x577B986B314D6009, 0xB616A12B7FE617AA}, // 1e160
+	{0xED5A7E85FDA0B80B, 0xE39C49765FDF9D94}, // 1e161
+	{0x14588F13BE847307, 0x8E41ADE9FBEBC27D}, // 1e162
+	{0x596EB2D8AE258FC8, 0xB1D219647AE6B31C}, // 1e163
+	{0x6FCA5F8ED9AEF3BB, 0xDE469FBD99A05FE3}, // 1e164
+	{0x25DE7BB9480D5854, 0x8AEC23D680043BEE}, // 1e165
+	{0xAF561AA79A10AE6A, 0xADA72CCC20054AE9}, // 1e166
+	{0x1B2BA1518094DA04, 0xD910F7FF28069DA4}, // 1e167
+	{0x90FB44D2F05D0842, 0x87AA9AFF79042286}, // 1e168
+	{0x353A1607AC744A53, 0xA99541BF57452B28}, // 1e169
+	{0x42889B8997915CE8, 0xD3FA922F2D1675F2}, // 1e170
+	{0x69956135FEBADA11, 0x847C9B5D7C2E09B7}, // 1e171
+	{0x43FAB9837E699095, 0xA59BC234DB398C25}, // 1e172
+	{0x94F967E45E03F4BB, 0xCF02B2C21207EF2E}, // 1e173
+	{0x1D1BE0EEBAC278F5, 0x8161AFB94B44F57D}, // 1e174
+	{0x6462D92A69731732, 0xA1BA1BA79E1632DC}, // 1e175
+	{0x7D7B8F7503CFDCFE, 0xCA28A291859BBF93}, // 1e176
+	{0x5CDA735244C3D43E, 0xFCB2CB35E702AF78}, // 1e177
+	{0x3A0888136AFA64A7, 0x9DEFBF01B061ADAB}, // 1e178
+	{0x088AAA1845B8FDD0, 0xC56BAEC21C7A1916}, // 1e179
+	{0x8AAD549E57273D45, 0xF6C69A72A3989F5B}, // 1e180
+	{0x36AC54E2F678864B, 0x9A3C2087A63F6399}, // 1e181
+	{0x84576A1BB416A7DD, 0xC0CB28A98FCF3C7F}, // 1e182
+	{0x656D44A2A11C51D5, 0xF0FDF2D3F3C30B9F}, // 1e183
+	{0x9F644AE5A4B1B325, 0x969EB7C47859E743}, // 1e184
+	{0x873D5D9F0DDE1FEE, 0xBC4665B596706114}, // 1e185
+	{0xA90CB506D155A7EA, 0xEB57FF22FC0C7959}, // 1e186
+	{0x09A7F12442D588F2, 0x9316FF75DD87CBD8}, // 1e187
+	{0x0C11ED6D538AEB2F, 0xB7DCBF5354E9BECE}, // 1e188
+	{0x8F1668C8A86DA5FA, 0xE5D3EF282A242E81}, // 1e189
+	{0xF96E017D694487BC, 0x8FA475791A569D10}, // 1e190
+	{0x37C981DCC395A9AC, 0xB38D92D760EC4455}, // 1e191
+	{0x85BBE253F47B1417, 0xE070F78D3927556A}, // 1e192
+	{0x93956D7478CCEC8E, 0x8C469AB843B89562}, // 1e193
+	{0x387AC8D1970027B2, 0xAF58416654A6BABB}, // 1e194
+	{0x06997B05FCC0319E, 0xDB2E51BFE9D0696A}, // 1e195
+	{0x441FECE3BDF81F03, 0x88FCF317F22241E2}, // 1e196
+	{0xD527E81CAD7626C3, 0xAB3C2FDDEEAAD25A}, // 1e197
+	{0x8A71E223D8D3B074, 0xD60B3BD56A5586F1}, // 1e198
+	{0xF6872D5667844E49, 0x85C7056562757456}, // 1e199
+	{0xB428F8AC016561DB, 0xA738C6BEBB12D16C}, // 1e200
+	{0xE13336D701BEBA52, 0xD106F86E69D785C7}, // 1e201
+	{0xECC0024661173473, 0x82A45B450226B39C}, // 1e202
+	{0x27F002D7F95D0190, 0xA34D721642B06084}, // 1e203
+	{0x31EC038DF7B441F4, 0xCC20CE9BD35C78A5}, // 1e204
+	{0x7E67047175A15271, 0xFF290242C83396CE}, // 1e205
+	{0x0F0062C6E984D386, 0x9F79A169BD203E41}, // 1e206
+	{0x52C07B78A3E60868, 0xC75809C42C684DD1}, // 1e207
+	{0xA7709A56CCDF8A82, 0xF92E0C3537826145}, // 1e208
+	{0x88A66076400BB691, 0x9BBCC7A142B17CCB}, // 1e209
+	{0x6ACFF893D00EA435, 0xC2ABF989935DDBFE}, // 1e210
+	{0x0583F6B8C4124D43, 0xF356F7EBF83552FE}, // 1e211
+	{0xC3727A337A8B704A, 0x98165AF37B2153DE}, // 1e212
+	{0x744F18C0592E4C5C, 0xBE1BF1B059E9A8D6}, // 1e213
+	{0x1162DEF06F79DF73, 0xEDA2EE1C7064130C}, // 1e214
+	{0x8ADDCB5645AC2BA8, 0x9485D4D1C63E8BE7}, // 1e215
+	{0x6D953E2BD7173692, 0xB9A74A0637CE2EE1}, // 1e216
+	{0xC8FA8DB6CCDD0437, 0xE8111C87C5C1BA99}, // 1e217
+	{0x1D9C9892400A22A2, 0x910AB1D4DB9914A0}, // 1e218
+	{0x2503BEB6D00CAB4B, 0xB54D5E4A127F59C8}, // 1e219
+	{0x2E44AE64840FD61D, 0xE2A0B5DC971F303A}, // 1e220
+	{0x5CEAECFED289E5D2, 0x8DA471A9DE737E24}, // 1e221
+	{0x7425A83E872C5F47, 0xB10D8E1456105DAD}, // 1e222
+	{0xD12F124E28F77719, 0xDD50F1996B947518}, // 1e223
+	{0x82BD6B70D99AAA6F, 0x8A5296FFE33CC92F}, // 1e224
+	{0x636CC64D1001550B, 0xACE73CBFDC0BFB7B}, // 1e225
+	{0x3C47F7E05401AA4E, 0xD8210BEFD30EFA5A}, // 1e226
+	{0x65ACFAEC34810A71, 0x8714A775E3E95C78}, // 1e227
+	{0x7F1839A741A14D0D, 0xA8D9D1535CE3B396}, // 1e228
+	{0x1EDE48111209A050, 0xD31045A8341CA07C}, // 1e229
+	{0x934AED0AAB460432, 0x83EA2B892091E44D}, // 1e230
+	{0xF81DA84D5617853F, 0xA4E4B66B68B65D60}, // 1e231
+	{0x36251260AB9D668E, 0xCE1DE40642E3F4B9}, // 1e232
+	{0xC1D72B7C6B426019, 0x80D2AE83E9CE78F3}, // 1e233
+	{0xB24CF65B8612F81F, 0xA1075A24E4421730}, // 1e234
+	{0xDEE033F26797B627, 0xC94930AE1D529CFC}, // 1e235
+	{0x169840EF017DA3B1, 0xFB9B7CD9A4A7443C}, // 1e236
+	{0x8E1F289560EE864E, 0x9D412E0806E88AA5}, // 1e237
+	{0xF1A6F2BAB92A27E2, 0xC491798A08A2AD4E}, // 1e238
+	{0xAE10AF696774B1DB, 0xF5B5D7EC8ACB58A2}, // 1e239
+	{0xACCA6DA1E0A8EF29, 0x9991A6F3D6BF1765}, // 1e240
+	{0x17FD090A58D32AF3, 0xBFF610B0CC6EDD3F}, // 1e241
+	{0xDDFC4B4CEF07F5B0, 0xEFF394DCFF8A948E}, // 1e242
+	{0x4ABDAF101564F98E, 0x95F83D0A1FB69CD9}, // 1e243
+	{0x9D6D1AD41ABE37F1, 0xBB764C4CA7A4440F}, // 1e244
+	{0x84C86189216DC5ED, 0xEA53DF5FD18D5513}, // 1e245
+	{0x32FD3CF5B4E49BB4, 0x92746B9BE2F8552C}, // 1e246
+	{0x3FBC8C33221DC2A1, 0xB7118682DBB66A77}, // 1e247
+	{0x0FABAF3FEAA5334A, 0xE4D5E82392A40515}, // 1e248
+	{0x29CB4D87F2A7400E, 0x8F05B1163BA6832D}, // 1e249
+	{0x743E20E9EF511012, 0xB2C71D5BCA9023F8}, // 1e250
+	{0x914DA9246B255416, 0xDF78E4B2BD342CF6}, // 1e251
+	{0x1AD089B6C2F7548E, 0x8BAB8EEFB6409C1A}, // 1e252
+	{0xA184AC2473B529B1, 0xAE9672ABA3D0C320}, // 1e253
+	{0xC9E5D72D90A2741E, 0xDA3C0F568CC4F3E8}, // 1e254
+	{0x7E2FA67C7A658892, 0x8865899617FB1871}, // 1e255
+	{0xDDBB901B98FEEAB7, 0xAA7EEBFB9DF9DE8D}, // 1e256
+	{0x552A74227F3EA565, 0xD51EA6FA85785631}, // 1e257
+	{0xD53A88958F87275F, 0x8533285C936B35DE}, // 1e258
+	{0x8A892ABAF368F137, 0xA67FF273B8460356}, // 1e259
+	{0x2D2B7569B0432D85, 0xD01FEF10A657842C}, // 1e260
+	{0x9C3B29620E29FC73, 0x8213F56A67F6B29B}, // 1e261
+	{0x8349F3BA91B47B8F, 0xA298F2C501F45F42}, // 1e262
+	{0x241C70A936219A73, 0xCB3F2F7642717713}, // 1e263
+	{0xED238CD383AA0110, 0xFE0EFB53D30DD4D7}, // 1e264
+	{0xF4363804324A40AA, 0x9EC95D1463E8A506}, // 1e265
+	{0xB143C6053EDCD0D5, 0xC67BB4597CE2CE48}, // 1e266
+	{0xDD94B7868E94050A, 0xF81AA16FDC1B81DA}, // 1e267
+	{0xCA7CF2B4191C8326, 0x9B10A4E5E9913128}, // 1e268
+	{0xFD1C2F611F63A3F0, 0xC1D4CE1F63F57D72}, // 1e269
+	{0xBC633B39673C8CEC, 0xF24A01A73CF2DCCF}, // 1e270
+	{0xD5BE0503E085D813, 0x976E41088617CA01}, // 1e271
+	{0x4B2D8644D8A74E18, 0xBD49D14AA79DBC82}, // 1e272
+	{0xDDF8E7D60ED1219E, 0xEC9C459D51852BA2}, // 1e273
+	{0xCABB90E5C942B503, 0x93E1AB8252F33B45}, // 1e274
+	{0x3D6A751F3B936243, 0xB8DA1662E7B00A17}, // 1e275
+	{0x0CC512670A783AD4, 0xE7109BFBA19C0C9D}, // 1e276
+	{0x27FB2B80668B24C5, 0x906A617D450187E2}, // 1e277
+	{0xB1F9F660802DEDF6, 0xB484F9DC9641E9DA}, // 1e278
+	{0x5E7873F8A0396973, 0xE1A63853BBD26451}, // 1e279
+	{0xDB0B487B6423E1E8, 0x8D07E33455637EB2}, // 1e280
+	{0x91CE1A9A3D2CDA62, 0xB049DC016ABC5E5F}, // 1e281
+	{0x7641A140CC7810FB, 0xDC5C5301C56B75F7}, // 1e282
+	{0xA9E904C87FCB0A9D, 0x89B9B3E11B6329BA}, // 1e283
+	{0x546345FA9FBDCD44, 0xAC2820D9623BF429}, // 1e284
+	{0xA97C177947AD4095, 0xD732290FBACAF133}, // 1e285
+	{0x49ED8EABCCCC485D, 0x867F59A9D4BED6C0}, // 1e286
+	{0x5C68F256BFFF5A74, 0xA81F301449EE8C70}, // 1e287
+	{0x73832EEC6FFF3111, 0xD226FC195C6A2F8C}, // 1e288
+	{0xC831FD53C5FF7EAB, 0x83585D8FD9C25DB7}, // 1e289
+	{0xBA3E7CA8B77F5E55, 0xA42E74F3D032F525}, // 1e290
+	{0x28CE1BD2E55F35EB, 0xCD3A1230C43FB26F}, // 1e291
+	{0x7980D163CF5B81B3, 0x80444B5E7AA7CF85}, // 1e292
+	{0xD7E105BCC332621F, 0xA0555E361951C366}, // 1e293
+	{0x8DD9472BF3FEFAA7, 0xC86AB5C39FA63440}, // 1e294
+	{0xB14F98F6F0FEB951, 0xFA856334878FC150}, // 1e295
+	{0x6ED1BF9A569F33D3, 0x9C935E00D4B9D8D2}, // 1e296
+	{0x0A862F80EC4700C8, 0xC3B8358109E84F07}, // 1e297
+	{0xCD27BB612758C0FA, 0xF4A642E14C6262C8}, // 1e298
+	{0x8038D51CB897789C, 0x98E7E9CCCFBD7DBD}, // 1e299
+	{0xE0470A63E6BD56C3, 0xBF21E44003ACDD2C}, // 1e300
+	{0x1858CCFCE06CAC74, 0xEEEA5D5004981478}, // 1e301
+	{0x0F37801E0C43EBC8, 0x95527A5202DF0CCB}, // 1e302
+	{0xD30560258F54E6BA, 0xBAA718E68396CFFD}, // 1e303
+	{0x47C6B82EF32A2069, 0xE950DF20247C83FD}, // 1e304
+	{0x4CDC331D57FA5441, 0x91D28B7416CDD27E}, // 1e305
+	{0xE0133FE4ADF8E952, 0xB6472E511C81471D}, // 1e306
+	{0x58180FDDD97723A6, 0xE3D8F9E563A198E5}, // 1e307
+	{0x570F09EAA7EA7648, 0x8E679C2F5E44FF8F}, // 1e308
+	{0x2CD2CC6551E513DA, 0xB201833B35D63F73}, // 1e309
+	{0xF8077F7EA65E58D1, 0xDE81E40A034BCF4F}, // 1e310
+	{0xFB04AFAF27FAF782, 0x8B112E86420F6191}, // 1e311
+	{0x79C5DB9AF1F9B563, 0xADD57A27D29339F6}, // 1e312
+	{0x18375281AE7822BC, 0xD94AD8B1C7380874}, // 1e313
+	{0x8F2293910D0B15B5, 0x87CEC76F1C830548}, // 1e314
+	{0xB2EB3875504DDB22, 0xA9C2794AE3A3C69A}, // 1e315
+	{0x5FA60692A46151EB, 0xD433179D9C8CB841}, // 1e316
+	{0xDBC7C41BA6BCD333, 0x849FEEC281D7F328}, // 1e317
+	{0x12B9B522906C0800, 0xA5C7EA73224DEFF3}, // 1e318
+	{0xD768226B34870A00, 0xCF39E50FEAE16BEF}, // 1e319
+	{0xE6A1158300D46640, 0x81842F29F2CCE375}, // 1e320
+	{0x60495AE3C1097FD0, 0xA1E53AF46F801C53}, // 1e321
+	{0x385BB19CB14BDFC4, 0xCA5E89B18B602368}, // 1e322
+	{0x46729E03DD9ED7B5, 0xFCF62C1DEE382C42}, // 1e323
+	{0x6C07A2C26A8346D1, 0x9E19DB92B4E31BA9}, // 1e324
+	{0xC7098B7305241885, 0xC5A05277621BE293}, // 1e325
+	{0xB8CBEE4FC66D1EA7, 0xF70867153AA2DB38}, // 1e326
+	{0x737F74F1DC043328, 0x9A65406D44A5C903}, // 1e327
+	{0x505F522E53053FF2, 0xC0FE908895CF3B44}, // 1e328
+	{0x647726B9E7C68FEF, 0xF13E34AABB430A15}, // 1e329
+	{0x5ECA783430DC19F5, 0x96C6E0EAB509E64D}, // 1e330
+	{0xB67D16413D132072, 0xBC789925624C5FE0}, // 1e331
+	{0xE41C5BD18C57E88F, 0xEB96BF6EBADF77D8}, // 1e332
+	{0x8E91B962F7B6F159, 0x933E37A534CBAAE7}, // 1e333
+	{0x723627BBB5A4ADB0, 0xB80DC58E81FE95A1}, // 1e334
+	{0xCEC3B1AAA30DD91C, 0xE61136F2227E3B09}, // 1e335
+	{0x213A4F0AA5E8A7B1, 0x8FCAC257558EE4E6}, // 1e336
+	{0xA988E2CD4F62D19D, 0xB3BD72ED2AF29E1F}, // 1e337
+	{0x93EB1B80A33B8605, 0xE0ACCFA875AF45A7}, // 1e338
+	{0xBC72F130660533C3, 0x8C6C01C9498D8B88}, // 1e339
+	{0xEB8FAD7C7F8680B4, 0xAF87023B9BF0EE6A}, // 1e340
+	{0xA67398DB9F6820E1, 0xDB68C2CA82ED2A05}, // 1e341
+	{0x88083F8943A1148C, 0x892179BE91D43A43}, // 1e342
+	{0x6A0A4F6B948959B0, 0xAB69D82E364948D4}, // 1e343
+	{0x848CE34679ABB01C, 0xD6444E39C3DB9B09}, // 1e344
+	{0xF2D80E0C0C0B4E11, 0x85EAB0E41A6940E5}, // 1e345
+	{0x6F8E118F0F0E2195, 0xA7655D1D2103911F}, // 1e346
+	{0x4B7195F2D2D1A9FB, 0xD13EB46469447567}, // 1e347
+}
diff --git a/src/strconv/example_test.go b/src/strconv/example_test.go
new file mode 100644
index 0000000..428fde4
--- /dev/null
+++ b/src/strconv/example_test.go
@@ -0,0 +1,440 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv_test
+
+import (
+	"fmt"
+	"log"
+	"strconv"
+)
+
+func ExampleAppendBool() {
+	b := []byte("bool:")
+	b = strconv.AppendBool(b, true)
+	fmt.Println(string(b))
+
+	// Output:
+	// bool:true
+}
+
+func ExampleAppendFloat() {
+	b32 := []byte("float32:")
+	b32 = strconv.AppendFloat(b32, 3.1415926535, 'E', -1, 32)
+	fmt.Println(string(b32))
+
+	b64 := []byte("float64:")
+	b64 = strconv.AppendFloat(b64, 3.1415926535, 'E', -1, 64)
+	fmt.Println(string(b64))
+
+	// Output:
+	// float32:3.1415927E+00
+	// float64:3.1415926535E+00
+}
+
+func ExampleAppendInt() {
+	b10 := []byte("int (base 10):")
+	b10 = strconv.AppendInt(b10, -42, 10)
+	fmt.Println(string(b10))
+
+	b16 := []byte("int (base 16):")
+	b16 = strconv.AppendInt(b16, -42, 16)
+	fmt.Println(string(b16))
+
+	// Output:
+	// int (base 10):-42
+	// int (base 16):-2a
+}
+
+func ExampleAppendQuote() {
+	b := []byte("quote:")
+	b = strconv.AppendQuote(b, `"Fran & Freddie's Diner"`)
+	fmt.Println(string(b))
+
+	// Output:
+	// quote:"\"Fran & Freddie's Diner\""
+}
+
+func ExampleAppendQuoteRune() {
+	b := []byte("rune:")
+	b = strconv.AppendQuoteRune(b, '☺')
+	fmt.Println(string(b))
+
+	// Output:
+	// rune:'☺'
+}
+
+func ExampleAppendQuoteRuneToASCII() {
+	b := []byte("rune (ascii):")
+	b = strconv.AppendQuoteRuneToASCII(b, '☺')
+	fmt.Println(string(b))
+
+	// Output:
+	// rune (ascii):'\u263a'
+}
+
+func ExampleAppendQuoteToASCII() {
+	b := []byte("quote (ascii):")
+	b = strconv.AppendQuoteToASCII(b, `"Fran & Freddie's Diner"`)
+	fmt.Println(string(b))
+
+	// Output:
+	// quote (ascii):"\"Fran & Freddie's Diner\""
+}
+
+func ExampleAppendUint() {
+	b10 := []byte("uint (base 10):")
+	b10 = strconv.AppendUint(b10, 42, 10)
+	fmt.Println(string(b10))
+
+	b16 := []byte("uint (base 16):")
+	b16 = strconv.AppendUint(b16, 42, 16)
+	fmt.Println(string(b16))
+
+	// Output:
+	// uint (base 10):42
+	// uint (base 16):2a
+}
+
+func ExampleAtoi() {
+	v := "10"
+	if s, err := strconv.Atoi(v); err == nil {
+		fmt.Printf("%T, %v", s, s)
+	}
+
+	// Output:
+	// int, 10
+}
+
+func ExampleCanBackquote() {
+	fmt.Println(strconv.CanBackquote("Fran & Freddie's Diner ☺"))
+	fmt.Println(strconv.CanBackquote("`can't backquote this`"))
+
+	// Output:
+	// true
+	// false
+}
+
+func ExampleFormatBool() {
+	v := true
+	s := strconv.FormatBool(v)
+	fmt.Printf("%T, %v\n", s, s)
+
+	// Output:
+	// string, true
+}
+
+func ExampleFormatFloat() {
+	v := 3.1415926535
+
+	s32 := strconv.FormatFloat(v, 'E', -1, 32)
+	fmt.Printf("%T, %v\n", s32, s32)
+
+	s64 := strconv.FormatFloat(v, 'E', -1, 64)
+	fmt.Printf("%T, %v\n", s64, s64)
+
+	// fmt.Println uses these arguments to print floats
+	fmt64 := strconv.FormatFloat(v, 'g', -1, 64)
+	fmt.Printf("%T, %v\n", fmt64, fmt64)
+
+	// Output:
+	// string, 3.1415927E+00
+	// string, 3.1415926535E+00
+	// string, 3.1415926535
+}
+
+func ExampleFormatInt() {
+	v := int64(-42)
+
+	s10 := strconv.FormatInt(v, 10)
+	fmt.Printf("%T, %v\n", s10, s10)
+
+	s16 := strconv.FormatInt(v, 16)
+	fmt.Printf("%T, %v\n", s16, s16)
+
+	// Output:
+	// string, -42
+	// string, -2a
+}
+
+func ExampleFormatUint() {
+	v := uint64(42)
+
+	s10 := strconv.FormatUint(v, 10)
+	fmt.Printf("%T, %v\n", s10, s10)
+
+	s16 := strconv.FormatUint(v, 16)
+	fmt.Printf("%T, %v\n", s16, s16)
+
+	// Output:
+	// string, 42
+	// string, 2a
+}
+
+func ExampleIsGraphic() {
+	shamrock := strconv.IsGraphic('☘')
+	fmt.Println(shamrock)
+
+	a := strconv.IsGraphic('a')
+	fmt.Println(a)
+
+	bel := strconv.IsGraphic('\007')
+	fmt.Println(bel)
+
+	// Output:
+	// true
+	// true
+	// false
+}
+
+func ExampleIsPrint() {
+	c := strconv.IsPrint('\u263a')
+	fmt.Println(c)
+
+	bel := strconv.IsPrint('\007')
+	fmt.Println(bel)
+
+	// Output:
+	// true
+	// false
+}
+
+func ExampleItoa() {
+	i := 10
+	s := strconv.Itoa(i)
+	fmt.Printf("%T, %v\n", s, s)
+
+	// Output:
+	// string, 10
+}
+
+func ExampleParseBool() {
+	v := "true"
+	if s, err := strconv.ParseBool(v); err == nil {
+		fmt.Printf("%T, %v\n", s, s)
+	}
+
+	// Output:
+	// bool, true
+}
+
+func ExampleParseFloat() {
+	v := "3.1415926535"
+	if s, err := strconv.ParseFloat(v, 32); err == nil {
+		fmt.Printf("%T, %v\n", s, s)
+	}
+	if s, err := strconv.ParseFloat(v, 64); err == nil {
+		fmt.Printf("%T, %v\n", s, s)
+	}
+	if s, err := strconv.ParseFloat("NaN", 32); err == nil {
+		fmt.Printf("%T, %v\n", s, s)
+	}
+	// ParseFloat is case insensitive
+	if s, err := strconv.ParseFloat("nan", 32); err == nil {
+		fmt.Printf("%T, %v\n", s, s)
+	}
+	if s, err := strconv.ParseFloat("inf", 32); err == nil {
+		fmt.Printf("%T, %v\n", s, s)
+	}
+	if s, err := strconv.ParseFloat("+Inf", 32); err == nil {
+		fmt.Printf("%T, %v\n", s, s)
+	}
+	if s, err := strconv.ParseFloat("-Inf", 32); err == nil {
+		fmt.Printf("%T, %v\n", s, s)
+	}
+	if s, err := strconv.ParseFloat("-0", 32); err == nil {
+		fmt.Printf("%T, %v\n", s, s)
+	}
+	if s, err := strconv.ParseFloat("+0", 32); err == nil {
+		fmt.Printf("%T, %v\n", s, s)
+	}
+
+	// Output:
+	// float64, 3.1415927410125732
+	// float64, 3.1415926535
+	// float64, NaN
+	// float64, NaN
+	// float64, +Inf
+	// float64, +Inf
+	// float64, -Inf
+	// float64, -0
+	// float64, 0
+}
+
+func ExampleParseInt() {
+	v32 := "-354634382"
+	if s, err := strconv.ParseInt(v32, 10, 32); err == nil {
+		fmt.Printf("%T, %v\n", s, s)
+	}
+	if s, err := strconv.ParseInt(v32, 16, 32); err == nil {
+		fmt.Printf("%T, %v\n", s, s)
+	}
+
+	v64 := "-3546343826724305832"
+	if s, err := strconv.ParseInt(v64, 10, 64); err == nil {
+		fmt.Printf("%T, %v\n", s, s)
+	}
+	if s, err := strconv.ParseInt(v64, 16, 64); err == nil {
+		fmt.Printf("%T, %v\n", s, s)
+	}
+
+	// Output:
+	// int64, -354634382
+	// int64, -3546343826724305832
+}
+
+func ExampleParseUint() {
+	v := "42"
+	if s, err := strconv.ParseUint(v, 10, 32); err == nil {
+		fmt.Printf("%T, %v\n", s, s)
+	}
+	if s, err := strconv.ParseUint(v, 10, 64); err == nil {
+		fmt.Printf("%T, %v\n", s, s)
+	}
+
+	// Output:
+	// uint64, 42
+	// uint64, 42
+}
+
+func ExampleQuote() {
+	// This string literal contains a tab character.
+	s := strconv.Quote(`"Fran & Freddie's Diner	☺"`)
+	fmt.Println(s)
+
+	// Output:
+	// "\"Fran & Freddie's Diner\t☺\""
+}
+
+func ExampleQuoteRune() {
+	s := strconv.QuoteRune('☺')
+	fmt.Println(s)
+
+	// Output:
+	// '☺'
+}
+
+func ExampleQuoteRuneToASCII() {
+	s := strconv.QuoteRuneToASCII('☺')
+	fmt.Println(s)
+
+	// Output:
+	// '\u263a'
+}
+
+func ExampleQuoteRuneToGraphic() {
+	s := strconv.QuoteRuneToGraphic('☺')
+	fmt.Println(s)
+
+	s = strconv.QuoteRuneToGraphic('\u263a')
+	fmt.Println(s)
+
+	s = strconv.QuoteRuneToGraphic('\u000a')
+	fmt.Println(s)
+
+	s = strconv.QuoteRuneToGraphic('	') // tab character
+	fmt.Println(s)
+
+	// Output:
+	// '☺'
+	// '☺'
+	// '\n'
+	// '\t'
+}
+
+func ExampleQuoteToASCII() {
+	// This string literal contains a tab character.
+	s := strconv.QuoteToASCII(`"Fran & Freddie's Diner	☺"`)
+	fmt.Println(s)
+
+	// Output:
+	// "\"Fran & Freddie's Diner\t\u263a\""
+}
+
+func ExampleQuoteToGraphic() {
+	s := strconv.QuoteToGraphic("☺")
+	fmt.Println(s)
+
+	// This string literal contains a tab character.
+	s = strconv.QuoteToGraphic("This is a \u263a	\u000a")
+	fmt.Println(s)
+
+	s = strconv.QuoteToGraphic(`" This is a ☺ \n "`)
+	fmt.Println(s)
+
+	// Output:
+	// "☺"
+	// "This is a ☺\t\n"
+	// "\" This is a ☺ \\n \""
+}
+
+func ExampleQuotedPrefix() {
+	s, err := strconv.QuotedPrefix("not a quoted string")
+	fmt.Printf("%q, %v\n", s, err)
+	s, err = strconv.QuotedPrefix("\"double-quoted string\" with trailing text")
+	fmt.Printf("%q, %v\n", s, err)
+	s, err = strconv.QuotedPrefix("`or backquoted` with more trailing text")
+	fmt.Printf("%q, %v\n", s, err)
+	s, err = strconv.QuotedPrefix("'\u263a' is also okay")
+	fmt.Printf("%q, %v\n", s, err)
+
+	// Output:
+	// "", invalid syntax
+	// "\"double-quoted string\"", <nil>
+	// "`or backquoted`", <nil>
+	// "'☺'", <nil>
+}
+
+func ExampleUnquote() {
+	s, err := strconv.Unquote("You can't unquote a string without quotes")
+	fmt.Printf("%q, %v\n", s, err)
+	s, err = strconv.Unquote("\"The string must be either double-quoted\"")
+	fmt.Printf("%q, %v\n", s, err)
+	s, err = strconv.Unquote("`or backquoted.`")
+	fmt.Printf("%q, %v\n", s, err)
+	s, err = strconv.Unquote("'\u263a'") // single character only allowed in single quotes
+	fmt.Printf("%q, %v\n", s, err)
+	s, err = strconv.Unquote("'\u2639\u2639'")
+	fmt.Printf("%q, %v\n", s, err)
+
+	// Output:
+	// "", invalid syntax
+	// "The string must be either double-quoted", <nil>
+	// "or backquoted.", <nil>
+	// "☺", <nil>
+	// "", invalid syntax
+}
+
+func ExampleUnquoteChar() {
+	v, mb, t, err := strconv.UnquoteChar(`\"Fran & Freddie's Diner\"`, '"')
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Println("value:", string(v))
+	fmt.Println("multibyte:", mb)
+	fmt.Println("tail:", t)
+
+	// Output:
+	// value: "
+	// multibyte: false
+	// tail: Fran & Freddie's Diner\"
+}
+
+func ExampleNumError() {
+	str := "Not a number"
+	if _, err := strconv.ParseFloat(str, 64); err != nil {
+		e := err.(*strconv.NumError)
+		fmt.Println("Func:", e.Func)
+		fmt.Println("Num:", e.Num)
+		fmt.Println("Err:", e.Err)
+		fmt.Println(err)
+	}
+
+	// Output:
+	// Func: ParseFloat
+	// Num: Not a number
+	// Err: invalid syntax
+	// strconv.ParseFloat: parsing "Not a number": invalid syntax
+}
diff --git a/src/strconv/export_test.go b/src/strconv/export_test.go
new file mode 100644
index 0000000..8c03a7f
--- /dev/null
+++ b/src/strconv/export_test.go
@@ -0,0 +1,10 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv
+
+var (
+	BitSizeError = bitSizeError
+	BaseError    = baseError
+)
diff --git a/src/strconv/fp_test.go b/src/strconv/fp_test.go
new file mode 100644
index 0000000..fd73958
--- /dev/null
+++ b/src/strconv/fp_test.go
@@ -0,0 +1,142 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv_test
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+	"testing"
+)
+
+func pow2(i int) float64 {
+	switch {
+	case i < 0:
+		return 1 / pow2(-i)
+	case i == 0:
+		return 1
+	case i == 1:
+		return 2
+	}
+	return pow2(i/2) * pow2(i-i/2)
+}
+
+// Wrapper around strconv.ParseFloat(x, 64).  Handles dddddp+ddd (binary exponent)
+// itself, passes the rest on to strconv.ParseFloat.
+func myatof64(s string) (f float64, ok bool) {
+	if mant, exp, ok := strings.Cut(s, "p"); ok {
+		n, err := strconv.ParseInt(mant, 10, 64)
+		if err != nil {
+			return 0, false
+		}
+		e, err1 := strconv.Atoi(exp)
+		if err1 != nil {
+			println("bad e", exp)
+			return 0, false
+		}
+		v := float64(n)
+		// We expect that v*pow2(e) fits in a float64,
+		// but pow2(e) by itself may not. Be careful.
+		if e <= -1000 {
+			v *= pow2(-1000)
+			e += 1000
+			for e < 0 {
+				v /= 2
+				e++
+			}
+			return v, true
+		}
+		if e >= 1000 {
+			v *= pow2(1000)
+			e -= 1000
+			for e > 0 {
+				v *= 2
+				e--
+			}
+			return v, true
+		}
+		return v * pow2(e), true
+	}
+	f1, err := strconv.ParseFloat(s, 64)
+	if err != nil {
+		return 0, false
+	}
+	return f1, true
+}
+
+// Wrapper around strconv.ParseFloat(x, 32).  Handles dddddp+ddd (binary exponent)
+// itself, passes the rest on to strconv.ParseFloat.
+func myatof32(s string) (f float32, ok bool) {
+	if mant, exp, ok := strings.Cut(s, "p"); ok {
+		n, err := strconv.Atoi(mant)
+		if err != nil {
+			println("bad n", mant)
+			return 0, false
+		}
+		e, err1 := strconv.Atoi(exp)
+		if err1 != nil {
+			println("bad p", exp)
+			return 0, false
+		}
+		return float32(float64(n) * pow2(e)), true
+	}
+	f64, err1 := strconv.ParseFloat(s, 32)
+	f1 := float32(f64)
+	if err1 != nil {
+		return 0, false
+	}
+	return f1, true
+}
+
+func TestFp(t *testing.T) {
+	f, err := os.Open("testdata/testfp.txt")
+	if err != nil {
+		t.Fatal("testfp: open testdata/testfp.txt:", err)
+	}
+	defer f.Close()
+
+	s := bufio.NewScanner(f)
+
+	for lineno := 1; s.Scan(); lineno++ {
+		line := s.Text()
+		if len(line) == 0 || line[0] == '#' {
+			continue
+		}
+		a := strings.Split(line, " ")
+		if len(a) != 4 {
+			t.Error("testdata/testfp.txt:", lineno, ": wrong field count")
+			continue
+		}
+		var s string
+		var v float64
+		switch a[0] {
+		case "float64":
+			var ok bool
+			v, ok = myatof64(a[2])
+			if !ok {
+				t.Error("testdata/testfp.txt:", lineno, ": cannot atof64 ", a[2])
+				continue
+			}
+			s = fmt.Sprintf(a[1], v)
+		case "float32":
+			v1, ok := myatof32(a[2])
+			if !ok {
+				t.Error("testdata/testfp.txt:", lineno, ": cannot atof32 ", a[2])
+				continue
+			}
+			s = fmt.Sprintf(a[1], v1)
+			v = float64(v1)
+		}
+		if s != a[3] {
+			t.Error("testdata/testfp.txt:", lineno, ": ", a[0], " ", a[1], " ", a[2], " (", v, ") ",
+				"want ", a[3], " got ", s)
+		}
+	}
+	if s.Err() != nil {
+		t.Fatal("testfp: read testdata/testfp.txt: ", s.Err())
+	}
+}
diff --git a/src/strconv/ftoa.go b/src/strconv/ftoa.go
new file mode 100644
index 0000000..c514e66
--- /dev/null
+++ b/src/strconv/ftoa.go
@@ -0,0 +1,570 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Binary to decimal floating point conversion.
+// Algorithm:
+//   1) store mantissa in multiprecision decimal
+//   2) shift decimal by exponent
+//   3) read digits out & format
+
+package strconv
+
+import "math"
+
+// TODO: move elsewhere?
+type floatInfo struct {
+	mantbits uint
+	expbits  uint
+	bias     int
+}
+
+var float32info = floatInfo{23, 8, -127}
+var float64info = floatInfo{52, 11, -1023}
+
+// FormatFloat converts the floating-point number f to a string,
+// according to the format fmt and precision prec. It rounds the
+// result assuming that the original was obtained from a floating-point
+// value of bitSize bits (32 for float32, 64 for float64).
+//
+// The format fmt is one of
+// 'b' (-ddddp±ddd, a binary exponent),
+// 'e' (-d.dddde±dd, a decimal exponent),
+// 'E' (-d.ddddE±dd, a decimal exponent),
+// 'f' (-ddd.dddd, no exponent),
+// 'g' ('e' for large exponents, 'f' otherwise),
+// 'G' ('E' for large exponents, 'f' otherwise),
+// 'x' (-0xd.ddddp±ddd, a hexadecimal fraction and binary exponent), or
+// 'X' (-0Xd.ddddP±ddd, a hexadecimal fraction and binary exponent).
+//
+// The precision prec controls the number of digits (excluding the exponent)
+// printed by the 'e', 'E', 'f', 'g', 'G', 'x', and 'X' formats.
+// For 'e', 'E', 'f', 'x', and 'X', it is the number of digits after the decimal point.
+// For 'g' and 'G' it is the maximum number of significant digits (trailing
+// zeros are removed).
+// The special precision -1 uses the smallest number of digits
+// necessary such that ParseFloat will return f exactly.
+func FormatFloat(f float64, fmt byte, prec, bitSize int) string {
+	return string(genericFtoa(make([]byte, 0, max(prec+4, 24)), f, fmt, prec, bitSize))
+}
+
+// AppendFloat appends the string form of the floating-point number f,
+// as generated by FormatFloat, to dst and returns the extended buffer.
+func AppendFloat(dst []byte, f float64, fmt byte, prec, bitSize int) []byte {
+	return genericFtoa(dst, f, fmt, prec, bitSize)
+}
+
+func genericFtoa(dst []byte, val float64, fmt byte, prec, bitSize int) []byte {
+	var bits uint64
+	var flt *floatInfo
+	switch bitSize {
+	case 32:
+		bits = uint64(math.Float32bits(float32(val)))
+		flt = &float32info
+	case 64:
+		bits = math.Float64bits(val)
+		flt = &float64info
+	default:
+		panic("strconv: illegal AppendFloat/FormatFloat bitSize")
+	}
+
+	neg := bits>>(flt.expbits+flt.mantbits) != 0
+	exp := int(bits>>flt.mantbits) & (1<<flt.expbits - 1)
+	mant := bits & (uint64(1)<<flt.mantbits - 1)
+
+	switch exp {
+	case 1<<flt.expbits - 1:
+		// Inf, NaN
+		var s string
+		switch {
+		case mant != 0:
+			s = "NaN"
+		case neg:
+			s = "-Inf"
+		default:
+			s = "+Inf"
+		}
+		return append(dst, s...)
+
+	case 0:
+		// denormalized
+		exp++
+
+	default:
+		// add implicit top bit
+		mant |= uint64(1) << flt.mantbits
+	}
+	exp += flt.bias
+
+	// Pick off easy binary, hex formats.
+	if fmt == 'b' {
+		return fmtB(dst, neg, mant, exp, flt)
+	}
+	if fmt == 'x' || fmt == 'X' {
+		return fmtX(dst, prec, fmt, neg, mant, exp, flt)
+	}
+
+	if !optimize {
+		return bigFtoa(dst, prec, fmt, neg, mant, exp, flt)
+	}
+
+	var digs decimalSlice
+	ok := false
+	// Negative precision means "only as much as needed to be exact."
+	shortest := prec < 0
+	if shortest {
+		// Use Ryu algorithm.
+		var buf [32]byte
+		digs.d = buf[:]
+		ryuFtoaShortest(&digs, mant, exp-int(flt.mantbits), flt)
+		ok = true
+		// Precision for shortest representation mode.
+		switch fmt {
+		case 'e', 'E':
+			prec = max(digs.nd-1, 0)
+		case 'f':
+			prec = max(digs.nd-digs.dp, 0)
+		case 'g', 'G':
+			prec = digs.nd
+		}
+	} else if fmt != 'f' {
+		// Fixed number of digits.
+		digits := prec
+		switch fmt {
+		case 'e', 'E':
+			digits++
+		case 'g', 'G':
+			if prec == 0 {
+				prec = 1
+			}
+			digits = prec
+		default:
+			// Invalid mode.
+			digits = 1
+		}
+		var buf [24]byte
+		if bitSize == 32 && digits <= 9 {
+			digs.d = buf[:]
+			ryuFtoaFixed32(&digs, uint32(mant), exp-int(flt.mantbits), digits)
+			ok = true
+		} else if digits <= 18 {
+			digs.d = buf[:]
+			ryuFtoaFixed64(&digs, mant, exp-int(flt.mantbits), digits)
+			ok = true
+		}
+	}
+	if !ok {
+		return bigFtoa(dst, prec, fmt, neg, mant, exp, flt)
+	}
+	return formatDigits(dst, shortest, neg, digs, prec, fmt)
+}
+
+// bigFtoa uses multiprecision computations to format a float.
+func bigFtoa(dst []byte, prec int, fmt byte, neg bool, mant uint64, exp int, flt *floatInfo) []byte {
+	d := new(decimal)
+	d.Assign(mant)
+	d.Shift(exp - int(flt.mantbits))
+	var digs decimalSlice
+	shortest := prec < 0
+	if shortest {
+		roundShortest(d, mant, exp, flt)
+		digs = decimalSlice{d: d.d[:], nd: d.nd, dp: d.dp}
+		// Precision for shortest representation mode.
+		switch fmt {
+		case 'e', 'E':
+			prec = digs.nd - 1
+		case 'f':
+			prec = max(digs.nd-digs.dp, 0)
+		case 'g', 'G':
+			prec = digs.nd
+		}
+	} else {
+		// Round appropriately.
+		switch fmt {
+		case 'e', 'E':
+			d.Round(prec + 1)
+		case 'f':
+			d.Round(d.dp + prec)
+		case 'g', 'G':
+			if prec == 0 {
+				prec = 1
+			}
+			d.Round(prec)
+		}
+		digs = decimalSlice{d: d.d[:], nd: d.nd, dp: d.dp}
+	}
+	return formatDigits(dst, shortest, neg, digs, prec, fmt)
+}
+
+func formatDigits(dst []byte, shortest bool, neg bool, digs decimalSlice, prec int, fmt byte) []byte {
+	switch fmt {
+	case 'e', 'E':
+		return fmtE(dst, neg, digs, prec, fmt)
+	case 'f':
+		return fmtF(dst, neg, digs, prec)
+	case 'g', 'G':
+		// trailing fractional zeros in 'e' form will be trimmed.
+		eprec := prec
+		if eprec > digs.nd && digs.nd >= digs.dp {
+			eprec = digs.nd
+		}
+		// %e is used if the exponent from the conversion
+		// is less than -4 or greater than or equal to the precision.
+		// if precision was the shortest possible, use precision 6 for this decision.
+		if shortest {
+			eprec = 6
+		}
+		exp := digs.dp - 1
+		if exp < -4 || exp >= eprec {
+			if prec > digs.nd {
+				prec = digs.nd
+			}
+			return fmtE(dst, neg, digs, prec-1, fmt+'e'-'g')
+		}
+		if prec > digs.dp {
+			prec = digs.nd
+		}
+		return fmtF(dst, neg, digs, max(prec-digs.dp, 0))
+	}
+
+	// unknown format
+	return append(dst, '%', fmt)
+}
+
+// roundShortest rounds d (= mant * 2^exp) to the shortest number of digits
+// that will let the original floating point value be precisely reconstructed.
+func roundShortest(d *decimal, mant uint64, exp int, flt *floatInfo) {
+	// If mantissa is zero, the number is zero; stop now.
+	if mant == 0 {
+		d.nd = 0
+		return
+	}
+
+	// Compute upper and lower such that any decimal number
+	// between upper and lower (possibly inclusive)
+	// will round to the original floating point number.
+
+	// We may see at once that the number is already shortest.
+	//
+	// Suppose d is not denormal, so that 2^exp <= d < 10^dp.
+	// The closest shorter number is at least 10^(dp-nd) away.
+	// The lower/upper bounds computed below are at distance
+	// at most 2^(exp-mantbits).
+	//
+	// So the number is already shortest if 10^(dp-nd) > 2^(exp-mantbits),
+	// or equivalently log2(10)*(dp-nd) > exp-mantbits.
+	// It is true if 332/100*(dp-nd) >= exp-mantbits (log2(10) > 3.32).
+	minexp := flt.bias + 1 // minimum possible exponent
+	if exp > minexp && 332*(d.dp-d.nd) >= 100*(exp-int(flt.mantbits)) {
+		// The number is already shortest.
+		return
+	}
+
+	// d = mant << (exp - mantbits)
+	// Next highest floating point number is mant+1 << exp-mantbits.
+	// Our upper bound is halfway between, mant*2+1 << exp-mantbits-1.
+	upper := new(decimal)
+	upper.Assign(mant*2 + 1)
+	upper.Shift(exp - int(flt.mantbits) - 1)
+
+	// d = mant << (exp - mantbits)
+	// Next lowest floating point number is mant-1 << exp-mantbits,
+	// unless mant-1 drops the significant bit and exp is not the minimum exp,
+	// in which case the next lowest is mant*2-1 << exp-mantbits-1.
+	// Either way, call it mantlo << explo-mantbits.
+	// Our lower bound is halfway between, mantlo*2+1 << explo-mantbits-1.
+	var mantlo uint64
+	var explo int
+	if mant > 1<<flt.mantbits || exp == minexp {
+		mantlo = mant - 1
+		explo = exp
+	} else {
+		mantlo = mant*2 - 1
+		explo = exp - 1
+	}
+	lower := new(decimal)
+	lower.Assign(mantlo*2 + 1)
+	lower.Shift(explo - int(flt.mantbits) - 1)
+
+	// The upper and lower bounds are possible outputs only if
+	// the original mantissa is even, so that IEEE round-to-even
+	// would round to the original mantissa and not the neighbors.
+	inclusive := mant%2 == 0
+
+	// As we walk the digits we want to know whether rounding up would fall
+	// within the upper bound. This is tracked by upperdelta:
+	//
+	// If upperdelta == 0, the digits of d and upper are the same so far.
+	//
+	// If upperdelta == 1, we saw a difference of 1 between d and upper on a
+	// previous digit and subsequently only 9s for d and 0s for upper.
+	// (Thus rounding up may fall outside the bound, if it is exclusive.)
+	//
+	// If upperdelta == 2, then the difference is greater than 1
+	// and we know that rounding up falls within the bound.
+	var upperdelta uint8
+
+	// Now we can figure out the minimum number of digits required.
+	// Walk along until d has distinguished itself from upper and lower.
+	for ui := 0; ; ui++ {
+		// lower, d, and upper may have the decimal points at different
+		// places. In this case upper is the longest, so we iterate from
+		// ui==0 and start li and mi at (possibly) -1.
+		mi := ui - upper.dp + d.dp
+		if mi >= d.nd {
+			break
+		}
+		li := ui - upper.dp + lower.dp
+		l := byte('0') // lower digit
+		if li >= 0 && li < lower.nd {
+			l = lower.d[li]
+		}
+		m := byte('0') // middle digit
+		if mi >= 0 {
+			m = d.d[mi]
+		}
+		u := byte('0') // upper digit
+		if ui < upper.nd {
+			u = upper.d[ui]
+		}
+
+		// Okay to round down (truncate) if lower has a different digit
+		// or if lower is inclusive and is exactly the result of rounding
+		// down (i.e., and we have reached the final digit of lower).
+		okdown := l != m || inclusive && li+1 == lower.nd
+
+		switch {
+		case upperdelta == 0 && m+1 < u:
+			// Example:
+			// m = 12345xxx
+			// u = 12347xxx
+			upperdelta = 2
+		case upperdelta == 0 && m != u:
+			// Example:
+			// m = 12345xxx
+			// u = 12346xxx
+			upperdelta = 1
+		case upperdelta == 1 && (m != '9' || u != '0'):
+			// Example:
+			// m = 1234598x
+			// u = 1234600x
+			upperdelta = 2
+		}
+		// Okay to round up if upper has a different digit and either upper
+		// is inclusive or upper is bigger than the result of rounding up.
+		okup := upperdelta > 0 && (inclusive || upperdelta > 1 || ui+1 < upper.nd)
+
+		// If it's okay to do either, then round to the nearest one.
+		// If it's okay to do only one, do it.
+		switch {
+		case okdown && okup:
+			d.Round(mi + 1)
+			return
+		case okdown:
+			d.RoundDown(mi + 1)
+			return
+		case okup:
+			d.RoundUp(mi + 1)
+			return
+		}
+	}
+}
+
+type decimalSlice struct {
+	d      []byte
+	nd, dp int
+}
+
+// %e: -d.ddddde±dd
+func fmtE(dst []byte, neg bool, d decimalSlice, prec int, fmt byte) []byte {
+	// sign
+	if neg {
+		dst = append(dst, '-')
+	}
+
+	// first digit
+	ch := byte('0')
+	if d.nd != 0 {
+		ch = d.d[0]
+	}
+	dst = append(dst, ch)
+
+	// .moredigits
+	if prec > 0 {
+		dst = append(dst, '.')
+		i := 1
+		m := min(d.nd, prec+1)
+		if i < m {
+			dst = append(dst, d.d[i:m]...)
+			i = m
+		}
+		for ; i <= prec; i++ {
+			dst = append(dst, '0')
+		}
+	}
+
+	// e±
+	dst = append(dst, fmt)
+	exp := d.dp - 1
+	if d.nd == 0 { // special case: 0 has exponent 0
+		exp = 0
+	}
+	if exp < 0 {
+		ch = '-'
+		exp = -exp
+	} else {
+		ch = '+'
+	}
+	dst = append(dst, ch)
+
+	// dd or ddd
+	switch {
+	case exp < 10:
+		dst = append(dst, '0', byte(exp)+'0')
+	case exp < 100:
+		dst = append(dst, byte(exp/10)+'0', byte(exp%10)+'0')
+	default:
+		dst = append(dst, byte(exp/100)+'0', byte(exp/10)%10+'0', byte(exp%10)+'0')
+	}
+
+	return dst
+}
+
+// %f: -ddddddd.ddddd
+func fmtF(dst []byte, neg bool, d decimalSlice, prec int) []byte {
+	// sign
+	if neg {
+		dst = append(dst, '-')
+	}
+
+	// integer, padded with zeros as needed.
+	if d.dp > 0 {
+		m := min(d.nd, d.dp)
+		dst = append(dst, d.d[:m]...)
+		for ; m < d.dp; m++ {
+			dst = append(dst, '0')
+		}
+	} else {
+		dst = append(dst, '0')
+	}
+
+	// fraction
+	if prec > 0 {
+		dst = append(dst, '.')
+		for i := 0; i < prec; i++ {
+			ch := byte('0')
+			if j := d.dp + i; 0 <= j && j < d.nd {
+				ch = d.d[j]
+			}
+			dst = append(dst, ch)
+		}
+	}
+
+	return dst
+}
+
+// %b: -ddddddddp±ddd
+func fmtB(dst []byte, neg bool, mant uint64, exp int, flt *floatInfo) []byte {
+	// sign
+	if neg {
+		dst = append(dst, '-')
+	}
+
+	// mantissa
+	dst, _ = formatBits(dst, mant, 10, false, true)
+
+	// p
+	dst = append(dst, 'p')
+
+	// ±exponent
+	exp -= int(flt.mantbits)
+	if exp >= 0 {
+		dst = append(dst, '+')
+	}
+	dst, _ = formatBits(dst, uint64(exp), 10, exp < 0, true)
+
+	return dst
+}
+
+// %x: -0x1.yyyyyyyyp±ddd or -0x0p+0. (y is hex digit, d is decimal digit)
+func fmtX(dst []byte, prec int, fmt byte, neg bool, mant uint64, exp int, flt *floatInfo) []byte {
+	if mant == 0 {
+		exp = 0
+	}
+
+	// Shift digits so leading 1 (if any) is at bit 1<<60.
+	mant <<= 60 - flt.mantbits
+	for mant != 0 && mant&(1<<60) == 0 {
+		mant <<= 1
+		exp--
+	}
+
+	// Round if requested.
+	if prec >= 0 && prec < 15 {
+		shift := uint(prec * 4)
+		extra := (mant << shift) & (1<<60 - 1)
+		mant >>= 60 - shift
+		if extra|(mant&1) > 1<<59 {
+			mant++
+		}
+		mant <<= 60 - shift
+		if mant&(1<<61) != 0 {
+			// Wrapped around.
+			mant >>= 1
+			exp++
+		}
+	}
+
+	hex := lowerhex
+	if fmt == 'X' {
+		hex = upperhex
+	}
+
+	// sign, 0x, leading digit
+	if neg {
+		dst = append(dst, '-')
+	}
+	dst = append(dst, '0', fmt, '0'+byte((mant>>60)&1))
+
+	// .fraction
+	mant <<= 4 // remove leading 0 or 1
+	if prec < 0 && mant != 0 {
+		dst = append(dst, '.')
+		for mant != 0 {
+			dst = append(dst, hex[(mant>>60)&15])
+			mant <<= 4
+		}
+	} else if prec > 0 {
+		dst = append(dst, '.')
+		for i := 0; i < prec; i++ {
+			dst = append(dst, hex[(mant>>60)&15])
+			mant <<= 4
+		}
+	}
+
+	// p±
+	ch := byte('P')
+	if fmt == lower(fmt) {
+		ch = 'p'
+	}
+	dst = append(dst, ch)
+	if exp < 0 {
+		ch = '-'
+		exp = -exp
+	} else {
+		ch = '+'
+	}
+	dst = append(dst, ch)
+
+	// dd or ddd or dddd
+	switch {
+	case exp < 100:
+		dst = append(dst, byte(exp/10)+'0', byte(exp%10)+'0')
+	case exp < 1000:
+		dst = append(dst, byte(exp/100)+'0', byte((exp/10)%10)+'0', byte(exp%10)+'0')
+	default:
+		dst = append(dst, byte(exp/1000)+'0', byte(exp/100)%10+'0', byte((exp/10)%10)+'0', byte(exp%10)+'0')
+	}
+
+	return dst
+}
diff --git a/src/strconv/ftoa_test.go b/src/strconv/ftoa_test.go
new file mode 100644
index 0000000..3512ccf
--- /dev/null
+++ b/src/strconv/ftoa_test.go
@@ -0,0 +1,324 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv_test
+
+import (
+	"math"
+	"math/rand"
+	. "strconv"
+	"testing"
+)
+
+type ftoaTest struct {
+	f    float64
+	fmt  byte
+	prec int
+	s    string
+}
+
+func fdiv(a, b float64) float64 { return a / b }
+
+const (
+	below1e23 = 99999999999999974834176
+	above1e23 = 100000000000000008388608
+)
+
+var ftoatests = []ftoaTest{
+	{1, 'e', 5, "1.00000e+00"},
+	{1, 'f', 5, "1.00000"},
+	{1, 'g', 5, "1"},
+	{1, 'g', -1, "1"},
+	{1, 'x', -1, "0x1p+00"},
+	{1, 'x', 5, "0x1.00000p+00"},
+	{20, 'g', -1, "20"},
+	{20, 'x', -1, "0x1.4p+04"},
+	{1234567.8, 'g', -1, "1.2345678e+06"},
+	{1234567.8, 'x', -1, "0x1.2d687cccccccdp+20"},
+	{200000, 'g', -1, "200000"},
+	{200000, 'x', -1, "0x1.86ap+17"},
+	{200000, 'X', -1, "0X1.86AP+17"},
+	{2000000, 'g', -1, "2e+06"},
+	{1e10, 'g', -1, "1e+10"},
+
+	// g conversion and zero suppression
+	{400, 'g', 2, "4e+02"},
+	{40, 'g', 2, "40"},
+	{4, 'g', 2, "4"},
+	{.4, 'g', 2, "0.4"},
+	{.04, 'g', 2, "0.04"},
+	{.004, 'g', 2, "0.004"},
+	{.0004, 'g', 2, "0.0004"},
+	{.00004, 'g', 2, "4e-05"},
+	{.000004, 'g', 2, "4e-06"},
+
+	{0, 'e', 5, "0.00000e+00"},
+	{0, 'f', 5, "0.00000"},
+	{0, 'g', 5, "0"},
+	{0, 'g', -1, "0"},
+	{0, 'x', 5, "0x0.00000p+00"},
+
+	{-1, 'e', 5, "-1.00000e+00"},
+	{-1, 'f', 5, "-1.00000"},
+	{-1, 'g', 5, "-1"},
+	{-1, 'g', -1, "-1"},
+
+	{12, 'e', 5, "1.20000e+01"},
+	{12, 'f', 5, "12.00000"},
+	{12, 'g', 5, "12"},
+	{12, 'g', -1, "12"},
+
+	{123456700, 'e', 5, "1.23457e+08"},
+	{123456700, 'f', 5, "123456700.00000"},
+	{123456700, 'g', 5, "1.2346e+08"},
+	{123456700, 'g', -1, "1.234567e+08"},
+
+	{1.2345e6, 'e', 5, "1.23450e+06"},
+	{1.2345e6, 'f', 5, "1234500.00000"},
+	{1.2345e6, 'g', 5, "1.2345e+06"},
+
+	// Round to even
+	{1.2345e6, 'e', 3, "1.234e+06"},
+	{1.2355e6, 'e', 3, "1.236e+06"},
+	{1.2345, 'f', 3, "1.234"},
+	{1.2355, 'f', 3, "1.236"},
+	{1234567890123456.5, 'e', 15, "1.234567890123456e+15"},
+	{1234567890123457.5, 'e', 15, "1.234567890123458e+15"},
+	{108678236358137.625, 'g', -1, "1.0867823635813762e+14"},
+
+	{1e23, 'e', 17, "9.99999999999999916e+22"},
+	{1e23, 'f', 17, "99999999999999991611392.00000000000000000"},
+	{1e23, 'g', 17, "9.9999999999999992e+22"},
+
+	{1e23, 'e', -1, "1e+23"},
+	{1e23, 'f', -1, "100000000000000000000000"},
+	{1e23, 'g', -1, "1e+23"},
+
+	{below1e23, 'e', 17, "9.99999999999999748e+22"},
+	{below1e23, 'f', 17, "99999999999999974834176.00000000000000000"},
+	{below1e23, 'g', 17, "9.9999999999999975e+22"},
+
+	{below1e23, 'e', -1, "9.999999999999997e+22"},
+	{below1e23, 'f', -1, "99999999999999970000000"},
+	{below1e23, 'g', -1, "9.999999999999997e+22"},
+
+	{above1e23, 'e', 17, "1.00000000000000008e+23"},
+	{above1e23, 'f', 17, "100000000000000008388608.00000000000000000"},
+	{above1e23, 'g', 17, "1.0000000000000001e+23"},
+
+	{above1e23, 'e', -1, "1.0000000000000001e+23"},
+	{above1e23, 'f', -1, "100000000000000010000000"},
+	{above1e23, 'g', -1, "1.0000000000000001e+23"},
+
+	{fdiv(5e-304, 1e20), 'g', -1, "5e-324"},   // avoid constant arithmetic
+	{fdiv(-5e-304, 1e20), 'g', -1, "-5e-324"}, // avoid constant arithmetic
+
+	{32, 'g', -1, "32"},
+	{32, 'g', 0, "3e+01"},
+
+	{100, 'x', -1, "0x1.9p+06"},
+	{100, 'y', -1, "%y"},
+
+	{math.NaN(), 'g', -1, "NaN"},
+	{-math.NaN(), 'g', -1, "NaN"},
+	{math.Inf(0), 'g', -1, "+Inf"},
+	{math.Inf(-1), 'g', -1, "-Inf"},
+	{-math.Inf(0), 'g', -1, "-Inf"},
+
+	{-1, 'b', -1, "-4503599627370496p-52"},
+
+	// fixed bugs
+	{0.9, 'f', 1, "0.9"},
+	{0.09, 'f', 1, "0.1"},
+	{0.0999, 'f', 1, "0.1"},
+	{0.05, 'f', 1, "0.1"},
+	{0.05, 'f', 0, "0"},
+	{0.5, 'f', 1, "0.5"},
+	{0.5, 'f', 0, "0"},
+	{1.5, 'f', 0, "2"},
+
+	// https://www.exploringbinary.com/java-hangs-when-converting-2-2250738585072012e-308/
+	{2.2250738585072012e-308, 'g', -1, "2.2250738585072014e-308"},
+	// https://www.exploringbinary.com/php-hangs-on-numeric-value-2-2250738585072011e-308/
+	{2.2250738585072011e-308, 'g', -1, "2.225073858507201e-308"},
+
+	// Issue 2625.
+	{383260575764816448, 'f', 0, "383260575764816448"},
+	{383260575764816448, 'g', -1, "3.8326057576481645e+17"},
+
+	// Issue 29491.
+	{498484681984085570, 'f', -1, "498484681984085570"},
+	{-5.8339553793802237e+23, 'g', -1, "-5.8339553793802237e+23"},
+
+	// Issue 52187
+	{123.45, '?', 0, "%?"},
+	{123.45, '?', 1, "%?"},
+	{123.45, '?', -1, "%?"},
+
+	// rounding
+	{2.275555555555555, 'x', -1, "0x1.23456789abcdep+01"},
+	{2.275555555555555, 'x', 0, "0x1p+01"},
+	{2.275555555555555, 'x', 2, "0x1.23p+01"},
+	{2.275555555555555, 'x', 16, "0x1.23456789abcde000p+01"},
+	{2.275555555555555, 'x', 21, "0x1.23456789abcde00000000p+01"},
+	{2.2755555510520935, 'x', -1, "0x1.2345678p+01"},
+	{2.2755555510520935, 'x', 6, "0x1.234568p+01"},
+	{2.275555431842804, 'x', -1, "0x1.2345668p+01"},
+	{2.275555431842804, 'x', 6, "0x1.234566p+01"},
+	{3.999969482421875, 'x', -1, "0x1.ffffp+01"},
+	{3.999969482421875, 'x', 4, "0x1.ffffp+01"},
+	{3.999969482421875, 'x', 3, "0x1.000p+02"},
+	{3.999969482421875, 'x', 2, "0x1.00p+02"},
+	{3.999969482421875, 'x', 1, "0x1.0p+02"},
+	{3.999969482421875, 'x', 0, "0x1p+02"},
+}
+
+func TestFtoa(t *testing.T) {
+	for i := 0; i < len(ftoatests); i++ {
+		test := &ftoatests[i]
+		s := FormatFloat(test.f, test.fmt, test.prec, 64)
+		if s != test.s {
+			t.Error("testN=64", test.f, string(test.fmt), test.prec, "want", test.s, "got", s)
+		}
+		x := AppendFloat([]byte("abc"), test.f, test.fmt, test.prec, 64)
+		if string(x) != "abc"+test.s {
+			t.Error("AppendFloat testN=64", test.f, string(test.fmt), test.prec, "want", "abc"+test.s, "got", string(x))
+		}
+		if float64(float32(test.f)) == test.f && test.fmt != 'b' {
+			s := FormatFloat(test.f, test.fmt, test.prec, 32)
+			if s != test.s {
+				t.Error("testN=32", test.f, string(test.fmt), test.prec, "want", test.s, "got", s)
+			}
+			x := AppendFloat([]byte("abc"), test.f, test.fmt, test.prec, 32)
+			if string(x) != "abc"+test.s {
+				t.Error("AppendFloat testN=32", test.f, string(test.fmt), test.prec, "want", "abc"+test.s, "got", string(x))
+			}
+		}
+	}
+}
+
+func TestFtoaPowersOfTwo(t *testing.T) {
+	for exp := -2048; exp <= 2048; exp++ {
+		f := math.Ldexp(1, exp)
+		if !math.IsInf(f, 0) {
+			s := FormatFloat(f, 'e', -1, 64)
+			if x, _ := ParseFloat(s, 64); x != f {
+				t.Errorf("failed roundtrip %v => %s => %v", f, s, x)
+			}
+		}
+		f32 := float32(f)
+		if !math.IsInf(float64(f32), 0) {
+			s := FormatFloat(float64(f32), 'e', -1, 32)
+			if x, _ := ParseFloat(s, 32); float32(x) != f32 {
+				t.Errorf("failed roundtrip %v => %s => %v", f32, s, float32(x))
+			}
+		}
+	}
+}
+
+func TestFtoaRandom(t *testing.T) {
+	N := int(1e4)
+	if testing.Short() {
+		N = 100
+	}
+	t.Logf("testing %d random numbers with fast and slow FormatFloat", N)
+	for i := 0; i < N; i++ {
+		bits := uint64(rand.Uint32())<<32 | uint64(rand.Uint32())
+		x := math.Float64frombits(bits)
+
+		shortFast := FormatFloat(x, 'g', -1, 64)
+		SetOptimize(false)
+		shortSlow := FormatFloat(x, 'g', -1, 64)
+		SetOptimize(true)
+		if shortSlow != shortFast {
+			t.Errorf("%b printed as %s, want %s", x, shortFast, shortSlow)
+		}
+
+		prec := rand.Intn(12) + 5
+		shortFast = FormatFloat(x, 'e', prec, 64)
+		SetOptimize(false)
+		shortSlow = FormatFloat(x, 'e', prec, 64)
+		SetOptimize(true)
+		if shortSlow != shortFast {
+			t.Errorf("%b printed as %s, want %s", x, shortFast, shortSlow)
+		}
+	}
+}
+
+func TestFormatFloatInvalidBitSize(t *testing.T) {
+	defer func() {
+		if r := recover(); r == nil {
+			t.Fatalf("expected panic due to invalid bitSize")
+		}
+	}()
+	_ = FormatFloat(3.14, 'g', -1, 100)
+}
+
+var ftoaBenches = []struct {
+	name    string
+	float   float64
+	fmt     byte
+	prec    int
+	bitSize int
+}{
+	{"Decimal", 33909, 'g', -1, 64},
+	{"Float", 339.7784, 'g', -1, 64},
+	{"Exp", -5.09e75, 'g', -1, 64},
+	{"NegExp", -5.11e-95, 'g', -1, 64},
+	{"LongExp", 1.234567890123456e-78, 'g', -1, 64},
+
+	{"Big", 123456789123456789123456789, 'g', -1, 64},
+	{"BinaryExp", -1, 'b', -1, 64},
+
+	{"32Integer", 33909, 'g', -1, 32},
+	{"32ExactFraction", 3.375, 'g', -1, 32},
+	{"32Point", 339.7784, 'g', -1, 32},
+	{"32Exp", -5.09e25, 'g', -1, 32},
+	{"32NegExp", -5.11e-25, 'g', -1, 32},
+	{"32Shortest", 1.234567e-8, 'g', -1, 32},
+	{"32Fixed8Hard", math.Ldexp(15961084, -125), 'e', 8, 32},
+	{"32Fixed9Hard", math.Ldexp(14855922, -83), 'e', 9, 32},
+
+	{"64Fixed1", 123456, 'e', 3, 64},
+	{"64Fixed2", 123.456, 'e', 3, 64},
+	{"64Fixed3", 1.23456e+78, 'e', 3, 64},
+	{"64Fixed4", 1.23456e-78, 'e', 3, 64},
+	{"64Fixed12", 1.23456e-78, 'e', 12, 64},
+	{"64Fixed16", 1.23456e-78, 'e', 16, 64},
+	// From testdata/testfp.txt
+	{"64Fixed12Hard", math.Ldexp(6965949469487146, -249), 'e', 12, 64},
+	{"64Fixed17Hard", math.Ldexp(8887055249355788, 665), 'e', 17, 64},
+	{"64Fixed18Hard", math.Ldexp(6994187472632449, 690), 'e', 18, 64},
+
+	// Trigger slow path (see issue #15672).
+	// The shortest is: 8.034137530808823e+43
+	{"Slowpath64", 8.03413753080882349e+43, 'e', -1, 64},
+	// This denormal is pathological because the lower/upper
+	// halfways to neighboring floats are:
+	// 622666234635.321003e-320 ~= 622666234635.321e-320
+	// 622666234635.321497e-320 ~= 622666234635.3215e-320
+	// making it hard to find the 3rd digit
+	{"SlowpathDenormal64", 622666234635.3213e-320, 'e', -1, 64},
+}
+
+func BenchmarkFormatFloat(b *testing.B) {
+	for _, c := range ftoaBenches {
+		b.Run(c.name, func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				FormatFloat(c.float, c.fmt, c.prec, c.bitSize)
+			}
+		})
+	}
+}
+
+func BenchmarkAppendFloat(b *testing.B) {
+	dst := make([]byte, 30)
+	for _, c := range ftoaBenches {
+		b.Run(c.name, func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				AppendFloat(dst[:0], c.float, c.fmt, c.prec, c.bitSize)
+			}
+		})
+	}
+}
diff --git a/src/strconv/ftoaryu.go b/src/strconv/ftoaryu.go
new file mode 100644
index 0000000..2e7bf71
--- /dev/null
+++ b/src/strconv/ftoaryu.go
@@ -0,0 +1,569 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv
+
+import (
+	"math/bits"
+)
+
+// binary to decimal conversion using the Ryū algorithm.
+//
+// See Ulf Adams, "Ryū: Fast Float-to-String Conversion" (doi:10.1145/3192366.3192369)
+//
+// Fixed precision formatting is a variant of the original paper's
+// algorithm, where a single multiplication by 10^k is required,
+// sharing the same rounding guarantees.
+
+// ryuFtoaFixed32 formats mant*(2^exp) with prec decimal digits.
+func ryuFtoaFixed32(d *decimalSlice, mant uint32, exp int, prec int) {
+	if prec < 0 {
+		panic("ryuFtoaFixed32 called with negative prec")
+	}
+	if prec > 9 {
+		panic("ryuFtoaFixed32 called with prec > 9")
+	}
+	// Zero input.
+	if mant == 0 {
+		d.nd, d.dp = 0, 0
+		return
+	}
+	// Renormalize to a 25-bit mantissa.
+	e2 := exp
+	if b := bits.Len32(mant); b < 25 {
+		mant <<= uint(25 - b)
+		e2 += b - 25
+	}
+	// Choose an exponent such that rounded mant*(2^e2)*(10^q) has
+	// at least prec decimal digits, i.e
+	//     mant*(2^e2)*(10^q) >= 10^(prec-1)
+	// Because mant >= 2^24, it is enough to choose:
+	//     2^(e2+24) >= 10^(-q+prec-1)
+	// or q = -mulByLog2Log10(e2+24) + prec - 1
+	q := -mulByLog2Log10(e2+24) + prec - 1
+
+	// Now compute mant*(2^e2)*(10^q).
+	// Is it an exact computation?
+	// Only small positive powers of 10 are exact (5^28 has 66 bits).
+	exact := q <= 27 && q >= 0
+
+	di, dexp2, d0 := mult64bitPow10(mant, e2, q)
+	if dexp2 >= 0 {
+		panic("not enough significant bits after mult64bitPow10")
+	}
+	// As a special case, computation might still be exact, if exponent
+	// was negative and if it amounts to computing an exact division.
+	// In that case, we ignore all lower bits.
+	// Note that division by 10^11 cannot be exact as 5^11 has 26 bits.
+	if q < 0 && q >= -10 && divisibleByPower5(uint64(mant), -q) {
+		exact = true
+		d0 = true
+	}
+	// Remove extra lower bits and keep rounding info.
+	extra := uint(-dexp2)
+	extraMask := uint32(1<<extra - 1)
+
+	di, dfrac := di>>extra, di&extraMask
+	roundUp := false
+	if exact {
+		// If we computed an exact product, d + 1/2
+		// should round to d+1 if 'd' is odd.
+		roundUp = dfrac > 1<<(extra-1) ||
+			(dfrac == 1<<(extra-1) && !d0) ||
+			(dfrac == 1<<(extra-1) && d0 && di&1 == 1)
+	} else {
+		// otherwise, d+1/2 always rounds up because
+		// we truncated below.
+		roundUp = dfrac>>(extra-1) == 1
+	}
+	if dfrac != 0 {
+		d0 = false
+	}
+	// Proceed to the requested number of digits
+	formatDecimal(d, uint64(di), !d0, roundUp, prec)
+	// Adjust exponent
+	d.dp -= q
+}
+
+// ryuFtoaFixed64 formats mant*(2^exp) with prec decimal digits.
+func ryuFtoaFixed64(d *decimalSlice, mant uint64, exp int, prec int) {
+	if prec > 18 {
+		panic("ryuFtoaFixed64 called with prec > 18")
+	}
+	// Zero input.
+	if mant == 0 {
+		d.nd, d.dp = 0, 0
+		return
+	}
+	// Renormalize to a 55-bit mantissa.
+	e2 := exp
+	if b := bits.Len64(mant); b < 55 {
+		mant = mant << uint(55-b)
+		e2 += b - 55
+	}
+	// Choose an exponent such that rounded mant*(2^e2)*(10^q) has
+	// at least prec decimal digits, i.e
+	//     mant*(2^e2)*(10^q) >= 10^(prec-1)
+	// Because mant >= 2^54, it is enough to choose:
+	//     2^(e2+54) >= 10^(-q+prec-1)
+	// or q = -mulByLog2Log10(e2+54) + prec - 1
+	//
+	// The minimal required exponent is -mulByLog2Log10(1025)+18 = -291
+	// The maximal required exponent is mulByLog2Log10(1074)+18 = 342
+	q := -mulByLog2Log10(e2+54) + prec - 1
+
+	// Now compute mant*(2^e2)*(10^q).
+	// Is it an exact computation?
+	// Only small positive powers of 10 are exact (5^55 has 128 bits).
+	exact := q <= 55 && q >= 0
+
+	di, dexp2, d0 := mult128bitPow10(mant, e2, q)
+	if dexp2 >= 0 {
+		panic("not enough significant bits after mult128bitPow10")
+	}
+	// As a special case, computation might still be exact, if exponent
+	// was negative and if it amounts to computing an exact division.
+	// In that case, we ignore all lower bits.
+	// Note that division by 10^23 cannot be exact as 5^23 has 54 bits.
+	if q < 0 && q >= -22 && divisibleByPower5(mant, -q) {
+		exact = true
+		d0 = true
+	}
+	// Remove extra lower bits and keep rounding info.
+	extra := uint(-dexp2)
+	extraMask := uint64(1<<extra - 1)
+
+	di, dfrac := di>>extra, di&extraMask
+	roundUp := false
+	if exact {
+		// If we computed an exact product, d + 1/2
+		// should round to d+1 if 'd' is odd.
+		roundUp = dfrac > 1<<(extra-1) ||
+			(dfrac == 1<<(extra-1) && !d0) ||
+			(dfrac == 1<<(extra-1) && d0 && di&1 == 1)
+	} else {
+		// otherwise, d+1/2 always rounds up because
+		// we truncated below.
+		roundUp = dfrac>>(extra-1) == 1
+	}
+	if dfrac != 0 {
+		d0 = false
+	}
+	// Proceed to the requested number of digits
+	formatDecimal(d, di, !d0, roundUp, prec)
+	// Adjust exponent
+	d.dp -= q
+}
+
+var uint64pow10 = [...]uint64{
+	1, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9,
+	1e10, 1e11, 1e12, 1e13, 1e14, 1e15, 1e16, 1e17, 1e18, 1e19,
+}
+
+// formatDecimal fills d with at most prec decimal digits
+// of mantissa m. The boolean trunc indicates whether m
+// is truncated compared to the original number being formatted.
+func formatDecimal(d *decimalSlice, m uint64, trunc bool, roundUp bool, prec int) {
+	max := uint64pow10[prec]
+	trimmed := 0
+	for m >= max {
+		a, b := m/10, m%10
+		m = a
+		trimmed++
+		if b > 5 {
+			roundUp = true
+		} else if b < 5 {
+			roundUp = false
+		} else { // b == 5
+			// round up if there are trailing digits,
+			// or if the new value of m is odd (round-to-even convention)
+			roundUp = trunc || m&1 == 1
+		}
+		if b != 0 {
+			trunc = true
+		}
+	}
+	if roundUp {
+		m++
+	}
+	if m >= max {
+		// Happens if di was originally 99999....xx
+		m /= 10
+		trimmed++
+	}
+	// render digits (similar to formatBits)
+	n := uint(prec)
+	d.nd = prec
+	v := m
+	for v >= 100 {
+		var v1, v2 uint64
+		if v>>32 == 0 {
+			v1, v2 = uint64(uint32(v)/100), uint64(uint32(v)%100)
+		} else {
+			v1, v2 = v/100, v%100
+		}
+		n -= 2
+		d.d[n+1] = smallsString[2*v2+1]
+		d.d[n+0] = smallsString[2*v2+0]
+		v = v1
+	}
+	if v > 0 {
+		n--
+		d.d[n] = smallsString[2*v+1]
+	}
+	if v >= 10 {
+		n--
+		d.d[n] = smallsString[2*v]
+	}
+	for d.d[d.nd-1] == '0' {
+		d.nd--
+		trimmed++
+	}
+	d.dp = d.nd + trimmed
+}
+
+// ryuFtoaShortest formats mant*2^exp with prec decimal digits.
+func ryuFtoaShortest(d *decimalSlice, mant uint64, exp int, flt *floatInfo) {
+	if mant == 0 {
+		d.nd, d.dp = 0, 0
+		return
+	}
+	// If input is an exact integer with fewer bits than the mantissa,
+	// the previous and next integer are not admissible representations.
+	if exp <= 0 && bits.TrailingZeros64(mant) >= -exp {
+		mant >>= uint(-exp)
+		ryuDigits(d, mant, mant, mant, true, false)
+		return
+	}
+	ml, mc, mu, e2 := computeBounds(mant, exp, flt)
+	if e2 == 0 {
+		ryuDigits(d, ml, mc, mu, true, false)
+		return
+	}
+	// Find 10^q *larger* than 2^-e2
+	q := mulByLog2Log10(-e2) + 1
+
+	// We are going to multiply by 10^q using 128-bit arithmetic.
+	// The exponent is the same for all 3 numbers.
+	var dl, dc, du uint64
+	var dl0, dc0, du0 bool
+	if flt == &float32info {
+		var dl32, dc32, du32 uint32
+		dl32, _, dl0 = mult64bitPow10(uint32(ml), e2, q)
+		dc32, _, dc0 = mult64bitPow10(uint32(mc), e2, q)
+		du32, e2, du0 = mult64bitPow10(uint32(mu), e2, q)
+		dl, dc, du = uint64(dl32), uint64(dc32), uint64(du32)
+	} else {
+		dl, _, dl0 = mult128bitPow10(ml, e2, q)
+		dc, _, dc0 = mult128bitPow10(mc, e2, q)
+		du, e2, du0 = mult128bitPow10(mu, e2, q)
+	}
+	if e2 >= 0 {
+		panic("not enough significant bits after mult128bitPow10")
+	}
+	// Is it an exact computation?
+	if q > 55 {
+		// Large positive powers of ten are not exact
+		dl0, dc0, du0 = false, false, false
+	}
+	if q < 0 && q >= -24 {
+		// Division by a power of ten may be exact.
+		// (note that 5^25 is a 59-bit number so division by 5^25 is never exact).
+		if divisibleByPower5(ml, -q) {
+			dl0 = true
+		}
+		if divisibleByPower5(mc, -q) {
+			dc0 = true
+		}
+		if divisibleByPower5(mu, -q) {
+			du0 = true
+		}
+	}
+	// Express the results (dl, dc, du)*2^e2 as integers.
+	// Extra bits must be removed and rounding hints computed.
+	extra := uint(-e2)
+	extraMask := uint64(1<<extra - 1)
+	// Now compute the floored, integral base 10 mantissas.
+	dl, fracl := dl>>extra, dl&extraMask
+	dc, fracc := dc>>extra, dc&extraMask
+	du, fracu := du>>extra, du&extraMask
+	// Is it allowed to use 'du' as a result?
+	// It is always allowed when it is truncated, but also
+	// if it is exact and the original binary mantissa is even
+	// When disallowed, we can subtract 1.
+	uok := !du0 || fracu > 0
+	if du0 && fracu == 0 {
+		uok = mant&1 == 0
+	}
+	if !uok {
+		du--
+	}
+	// Is 'dc' the correctly rounded base 10 mantissa?
+	// The correct rounding might be dc+1
+	cup := false // don't round up.
+	if dc0 {
+		// If we computed an exact product, the half integer
+		// should round to next (even) integer if 'dc' is odd.
+		cup = fracc > 1<<(extra-1) ||
+			(fracc == 1<<(extra-1) && dc&1 == 1)
+	} else {
+		// otherwise, the result is a lower truncation of the ideal
+		// result.
+		cup = fracc>>(extra-1) == 1
+	}
+	// Is 'dl' an allowed representation?
+	// Only if it is an exact value, and if the original binary mantissa
+	// was even.
+	lok := dl0 && fracl == 0 && (mant&1 == 0)
+	if !lok {
+		dl++
+	}
+	// We need to remember whether the trimmed digits of 'dc' are zero.
+	c0 := dc0 && fracc == 0
+	// render digits
+	ryuDigits(d, dl, dc, du, c0, cup)
+	d.dp -= q
+}
+
+// mulByLog2Log10 returns math.Floor(x * log(2)/log(10)) for an integer x in
+// the range -1600 <= x && x <= +1600.
+//
+// The range restriction lets us work in faster integer arithmetic instead of
+// slower floating point arithmetic. Correctness is verified by unit tests.
+func mulByLog2Log10(x int) int {
+	// log(2)/log(10) ≈ 0.30102999566 ≈ 78913 / 2^18
+	return (x * 78913) >> 18
+}
+
+// mulByLog10Log2 returns math.Floor(x * log(10)/log(2)) for an integer x in
+// the range -500 <= x && x <= +500.
+//
+// The range restriction lets us work in faster integer arithmetic instead of
+// slower floating point arithmetic. Correctness is verified by unit tests.
+func mulByLog10Log2(x int) int {
+	// log(10)/log(2) ≈ 3.32192809489 ≈ 108853 / 2^15
+	return (x * 108853) >> 15
+}
+
+// computeBounds returns a floating-point vector (l, c, u)×2^e2
+// where the mantissas are 55-bit (or 26-bit) integers, describing the interval
+// represented by the input float64 or float32.
+func computeBounds(mant uint64, exp int, flt *floatInfo) (lower, central, upper uint64, e2 int) {
+	if mant != 1<<flt.mantbits || exp == flt.bias+1-int(flt.mantbits) {
+		// regular case (or denormals)
+		lower, central, upper = 2*mant-1, 2*mant, 2*mant+1
+		e2 = exp - 1
+		return
+	} else {
+		// border of an exponent
+		lower, central, upper = 4*mant-1, 4*mant, 4*mant+2
+		e2 = exp - 2
+		return
+	}
+}
+
+func ryuDigits(d *decimalSlice, lower, central, upper uint64,
+	c0, cup bool) {
+	lhi, llo := divmod1e9(lower)
+	chi, clo := divmod1e9(central)
+	uhi, ulo := divmod1e9(upper)
+	if uhi == 0 {
+		// only low digits (for denormals)
+		ryuDigits32(d, llo, clo, ulo, c0, cup, 8)
+	} else if lhi < uhi {
+		// truncate 9 digits at once.
+		if llo != 0 {
+			lhi++
+		}
+		c0 = c0 && clo == 0
+		cup = (clo > 5e8) || (clo == 5e8 && cup)
+		ryuDigits32(d, lhi, chi, uhi, c0, cup, 8)
+		d.dp += 9
+	} else {
+		d.nd = 0
+		// emit high part
+		n := uint(9)
+		for v := chi; v > 0; {
+			v1, v2 := v/10, v%10
+			v = v1
+			n--
+			d.d[n] = byte(v2 + '0')
+		}
+		d.d = d.d[n:]
+		d.nd = int(9 - n)
+		// emit low part
+		ryuDigits32(d, llo, clo, ulo,
+			c0, cup, d.nd+8)
+	}
+	// trim trailing zeros
+	for d.nd > 0 && d.d[d.nd-1] == '0' {
+		d.nd--
+	}
+	// trim initial zeros
+	for d.nd > 0 && d.d[0] == '0' {
+		d.nd--
+		d.dp--
+		d.d = d.d[1:]
+	}
+}
+
+// ryuDigits32 emits decimal digits for a number less than 1e9.
+func ryuDigits32(d *decimalSlice, lower, central, upper uint32,
+	c0, cup bool, endindex int) {
+	if upper == 0 {
+		d.dp = endindex + 1
+		return
+	}
+	trimmed := 0
+	// Remember last trimmed digit to check for round-up.
+	// c0 will be used to remember zeroness of following digits.
+	cNextDigit := 0
+	for upper > 0 {
+		// Repeatedly compute:
+		// l = Ceil(lower / 10^k)
+		// c = Round(central / 10^k)
+		// u = Floor(upper / 10^k)
+		// and stop when c goes out of the (l, u) interval.
+		l := (lower + 9) / 10
+		c, cdigit := central/10, central%10
+		u := upper / 10
+		if l > u {
+			// don't trim the last digit as it is forbidden to go below l
+			// other, trim and exit now.
+			break
+		}
+		// Check that we didn't cross the lower boundary.
+		// The case where l < u but c == l-1 is essentially impossible,
+		// but may happen if:
+		//    lower   = ..11
+		//    central = ..19
+		//    upper   = ..31
+		// and means that 'central' is very close but less than
+		// an integer ending with many zeros, and usually
+		// the "round-up" logic hides the problem.
+		if l == c+1 && c < u {
+			c++
+			cdigit = 0
+			cup = false
+		}
+		trimmed++
+		// Remember trimmed digits of c
+		c0 = c0 && cNextDigit == 0
+		cNextDigit = int(cdigit)
+		lower, central, upper = l, c, u
+	}
+	// should we round up?
+	if trimmed > 0 {
+		cup = cNextDigit > 5 ||
+			(cNextDigit == 5 && !c0) ||
+			(cNextDigit == 5 && c0 && central&1 == 1)
+	}
+	if central < upper && cup {
+		central++
+	}
+	// We know where the number ends, fill directly
+	endindex -= trimmed
+	v := central
+	n := endindex
+	for n > d.nd {
+		v1, v2 := v/100, v%100
+		d.d[n] = smallsString[2*v2+1]
+		d.d[n-1] = smallsString[2*v2+0]
+		n -= 2
+		v = v1
+	}
+	if n == d.nd {
+		d.d[n] = byte(v + '0')
+	}
+	d.nd = endindex + 1
+	d.dp = d.nd + trimmed
+}
+
+// mult64bitPow10 takes a floating-point input with a 25-bit
+// mantissa and multiplies it with 10^q. The resulting mantissa
+// is m*P >> 57 where P is a 64-bit element of the detailedPowersOfTen tables.
+// It is typically 31 or 32-bit wide.
+// The returned boolean is true if all trimmed bits were zero.
+//
+// That is:
+//
+//	m*2^e2 * round(10^q) = resM * 2^resE + ε
+//	exact = ε == 0
+func mult64bitPow10(m uint32, e2, q int) (resM uint32, resE int, exact bool) {
+	if q == 0 {
+		// P == 1<<63
+		return m << 6, e2 - 6, true
+	}
+	if q < detailedPowersOfTenMinExp10 || detailedPowersOfTenMaxExp10 < q {
+		// This never happens due to the range of float32/float64 exponent
+		panic("mult64bitPow10: power of 10 is out of range")
+	}
+	pow := detailedPowersOfTen[q-detailedPowersOfTenMinExp10][1]
+	if q < 0 {
+		// Inverse powers of ten must be rounded up.
+		pow += 1
+	}
+	hi, lo := bits.Mul64(uint64(m), pow)
+	e2 += mulByLog10Log2(q) - 63 + 57
+	return uint32(hi<<7 | lo>>57), e2, lo<<7 == 0
+}
+
+// mult128bitPow10 takes a floating-point input with a 55-bit
+// mantissa and multiplies it with 10^q. The resulting mantissa
+// is m*P >> 119 where P is a 128-bit element of the detailedPowersOfTen tables.
+// It is typically 63 or 64-bit wide.
+// The returned boolean is true is all trimmed bits were zero.
+//
+// That is:
+//
+//	m*2^e2 * round(10^q) = resM * 2^resE + ε
+//	exact = ε == 0
+func mult128bitPow10(m uint64, e2, q int) (resM uint64, resE int, exact bool) {
+	if q == 0 {
+		// P == 1<<127
+		return m << 8, e2 - 8, true
+	}
+	if q < detailedPowersOfTenMinExp10 || detailedPowersOfTenMaxExp10 < q {
+		// This never happens due to the range of float32/float64 exponent
+		panic("mult128bitPow10: power of 10 is out of range")
+	}
+	pow := detailedPowersOfTen[q-detailedPowersOfTenMinExp10]
+	if q < 0 {
+		// Inverse powers of ten must be rounded up.
+		pow[0] += 1
+	}
+	e2 += mulByLog10Log2(q) - 127 + 119
+
+	// long multiplication
+	l1, l0 := bits.Mul64(m, pow[0])
+	h1, h0 := bits.Mul64(m, pow[1])
+	mid, carry := bits.Add64(l1, h0, 0)
+	h1 += carry
+	return h1<<9 | mid>>55, e2, mid<<9 == 0 && l0 == 0
+}
+
+func divisibleByPower5(m uint64, k int) bool {
+	if m == 0 {
+		return true
+	}
+	for i := 0; i < k; i++ {
+		if m%5 != 0 {
+			return false
+		}
+		m /= 5
+	}
+	return true
+}
+
+// divmod1e9 computes quotient and remainder of division by 1e9,
+// avoiding runtime uint64 division on 32-bit platforms.
+func divmod1e9(x uint64) (uint32, uint32) {
+	if !host32bit {
+		return uint32(x / 1e9), uint32(x % 1e9)
+	}
+	// Use the same sequence of operations as the amd64 compiler.
+	hi, _ := bits.Mul64(x>>1, 0x89705f4136b4a598) // binary digits of 1e-9
+	q := hi >> 28
+	return uint32(q), uint32(x - q*1e9)
+}
diff --git a/src/strconv/ftoaryu_test.go b/src/strconv/ftoaryu_test.go
new file mode 100644
index 0000000..9758619
--- /dev/null
+++ b/src/strconv/ftoaryu_test.go
@@ -0,0 +1,31 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv_test
+
+import (
+	"math"
+	. "strconv"
+	"testing"
+)
+
+func TestMulByLog2Log10(t *testing.T) {
+	for x := -1600; x <= +1600; x++ {
+		iMath := MulByLog2Log10(x)
+		fMath := int(math.Floor(float64(x) * math.Ln2 / math.Ln10))
+		if iMath != fMath {
+			t.Errorf("mulByLog2Log10(%d) failed: %d vs %d\n", x, iMath, fMath)
+		}
+	}
+}
+
+func TestMulByLog10Log2(t *testing.T) {
+	for x := -500; x <= +500; x++ {
+		iMath := MulByLog10Log2(x)
+		fMath := int(math.Floor(float64(x) * math.Ln10 / math.Ln2))
+		if iMath != fMath {
+			t.Errorf("mulByLog10Log2(%d) failed: %d vs %d\n", x, iMath, fMath)
+		}
+	}
+}
diff --git a/src/strconv/internal_test.go b/src/strconv/internal_test.go
new file mode 100644
index 0000000..f2cceff
--- /dev/null
+++ b/src/strconv/internal_test.go
@@ -0,0 +1,31 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// export access to strconv internals for tests
+
+package strconv
+
+func NewDecimal(i uint64) *decimal {
+	d := new(decimal)
+	d.Assign(i)
+	return d
+}
+
+func SetOptimize(b bool) bool {
+	old := optimize
+	optimize = b
+	return old
+}
+
+func ParseFloatPrefix(s string, bitSize int) (float64, int, error) {
+	return parseFloatPrefix(s, bitSize)
+}
+
+func MulByLog2Log10(x int) int {
+	return mulByLog2Log10(x)
+}
+
+func MulByLog10Log2(x int) int {
+	return mulByLog10Log2(x)
+}
diff --git a/src/strconv/isprint.go b/src/strconv/isprint.go
new file mode 100644
index 0000000..baa14a6
--- /dev/null
+++ b/src/strconv/isprint.go
@@ -0,0 +1,752 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Code generated by go run makeisprint.go -output isprint.go; DO NOT EDIT.
+
+package strconv
+
+// (424+133+112)*2 + (508)*4 = 3370 bytes
+
+var isPrint16 = []uint16{
+	0x0020, 0x007e,
+	0x00a1, 0x0377,
+	0x037a, 0x037f,
+	0x0384, 0x0556,
+	0x0559, 0x058a,
+	0x058d, 0x05c7,
+	0x05d0, 0x05ea,
+	0x05ef, 0x05f4,
+	0x0606, 0x070d,
+	0x0710, 0x074a,
+	0x074d, 0x07b1,
+	0x07c0, 0x07fa,
+	0x07fd, 0x082d,
+	0x0830, 0x085b,
+	0x085e, 0x086a,
+	0x0870, 0x088e,
+	0x0898, 0x098c,
+	0x098f, 0x0990,
+	0x0993, 0x09b2,
+	0x09b6, 0x09b9,
+	0x09bc, 0x09c4,
+	0x09c7, 0x09c8,
+	0x09cb, 0x09ce,
+	0x09d7, 0x09d7,
+	0x09dc, 0x09e3,
+	0x09e6, 0x09fe,
+	0x0a01, 0x0a0a,
+	0x0a0f, 0x0a10,
+	0x0a13, 0x0a39,
+	0x0a3c, 0x0a42,
+	0x0a47, 0x0a48,
+	0x0a4b, 0x0a4d,
+	0x0a51, 0x0a51,
+	0x0a59, 0x0a5e,
+	0x0a66, 0x0a76,
+	0x0a81, 0x0ab9,
+	0x0abc, 0x0acd,
+	0x0ad0, 0x0ad0,
+	0x0ae0, 0x0ae3,
+	0x0ae6, 0x0af1,
+	0x0af9, 0x0b0c,
+	0x0b0f, 0x0b10,
+	0x0b13, 0x0b39,
+	0x0b3c, 0x0b44,
+	0x0b47, 0x0b48,
+	0x0b4b, 0x0b4d,
+	0x0b55, 0x0b57,
+	0x0b5c, 0x0b63,
+	0x0b66, 0x0b77,
+	0x0b82, 0x0b8a,
+	0x0b8e, 0x0b95,
+	0x0b99, 0x0b9f,
+	0x0ba3, 0x0ba4,
+	0x0ba8, 0x0baa,
+	0x0bae, 0x0bb9,
+	0x0bbe, 0x0bc2,
+	0x0bc6, 0x0bcd,
+	0x0bd0, 0x0bd0,
+	0x0bd7, 0x0bd7,
+	0x0be6, 0x0bfa,
+	0x0c00, 0x0c39,
+	0x0c3c, 0x0c4d,
+	0x0c55, 0x0c5a,
+	0x0c5d, 0x0c5d,
+	0x0c60, 0x0c63,
+	0x0c66, 0x0c6f,
+	0x0c77, 0x0cb9,
+	0x0cbc, 0x0ccd,
+	0x0cd5, 0x0cd6,
+	0x0cdd, 0x0ce3,
+	0x0ce6, 0x0cf3,
+	0x0d00, 0x0d4f,
+	0x0d54, 0x0d63,
+	0x0d66, 0x0d96,
+	0x0d9a, 0x0dbd,
+	0x0dc0, 0x0dc6,
+	0x0dca, 0x0dca,
+	0x0dcf, 0x0ddf,
+	0x0de6, 0x0def,
+	0x0df2, 0x0df4,
+	0x0e01, 0x0e3a,
+	0x0e3f, 0x0e5b,
+	0x0e81, 0x0ebd,
+	0x0ec0, 0x0ed9,
+	0x0edc, 0x0edf,
+	0x0f00, 0x0f6c,
+	0x0f71, 0x0fda,
+	0x1000, 0x10c7,
+	0x10cd, 0x10cd,
+	0x10d0, 0x124d,
+	0x1250, 0x125d,
+	0x1260, 0x128d,
+	0x1290, 0x12b5,
+	0x12b8, 0x12c5,
+	0x12c8, 0x1315,
+	0x1318, 0x135a,
+	0x135d, 0x137c,
+	0x1380, 0x1399,
+	0x13a0, 0x13f5,
+	0x13f8, 0x13fd,
+	0x1400, 0x169c,
+	0x16a0, 0x16f8,
+	0x1700, 0x1715,
+	0x171f, 0x1736,
+	0x1740, 0x1753,
+	0x1760, 0x1773,
+	0x1780, 0x17dd,
+	0x17e0, 0x17e9,
+	0x17f0, 0x17f9,
+	0x1800, 0x1819,
+	0x1820, 0x1878,
+	0x1880, 0x18aa,
+	0x18b0, 0x18f5,
+	0x1900, 0x192b,
+	0x1930, 0x193b,
+	0x1940, 0x1940,
+	0x1944, 0x196d,
+	0x1970, 0x1974,
+	0x1980, 0x19ab,
+	0x19b0, 0x19c9,
+	0x19d0, 0x19da,
+	0x19de, 0x1a1b,
+	0x1a1e, 0x1a7c,
+	0x1a7f, 0x1a89,
+	0x1a90, 0x1a99,
+	0x1aa0, 0x1aad,
+	0x1ab0, 0x1ace,
+	0x1b00, 0x1b4c,
+	0x1b50, 0x1bf3,
+	0x1bfc, 0x1c37,
+	0x1c3b, 0x1c49,
+	0x1c4d, 0x1c88,
+	0x1c90, 0x1cba,
+	0x1cbd, 0x1cc7,
+	0x1cd0, 0x1cfa,
+	0x1d00, 0x1f15,
+	0x1f18, 0x1f1d,
+	0x1f20, 0x1f45,
+	0x1f48, 0x1f4d,
+	0x1f50, 0x1f7d,
+	0x1f80, 0x1fd3,
+	0x1fd6, 0x1fef,
+	0x1ff2, 0x1ffe,
+	0x2010, 0x2027,
+	0x2030, 0x205e,
+	0x2070, 0x2071,
+	0x2074, 0x209c,
+	0x20a0, 0x20c0,
+	0x20d0, 0x20f0,
+	0x2100, 0x218b,
+	0x2190, 0x2426,
+	0x2440, 0x244a,
+	0x2460, 0x2b73,
+	0x2b76, 0x2cf3,
+	0x2cf9, 0x2d27,
+	0x2d2d, 0x2d2d,
+	0x2d30, 0x2d67,
+	0x2d6f, 0x2d70,
+	0x2d7f, 0x2d96,
+	0x2da0, 0x2e5d,
+	0x2e80, 0x2ef3,
+	0x2f00, 0x2fd5,
+	0x2ff0, 0x2ffb,
+	0x3001, 0x3096,
+	0x3099, 0x30ff,
+	0x3105, 0x31e3,
+	0x31f0, 0xa48c,
+	0xa490, 0xa4c6,
+	0xa4d0, 0xa62b,
+	0xa640, 0xa6f7,
+	0xa700, 0xa7ca,
+	0xa7d0, 0xa7d9,
+	0xa7f2, 0xa82c,
+	0xa830, 0xa839,
+	0xa840, 0xa877,
+	0xa880, 0xa8c5,
+	0xa8ce, 0xa8d9,
+	0xa8e0, 0xa953,
+	0xa95f, 0xa97c,
+	0xa980, 0xa9d9,
+	0xa9de, 0xaa36,
+	0xaa40, 0xaa4d,
+	0xaa50, 0xaa59,
+	0xaa5c, 0xaac2,
+	0xaadb, 0xaaf6,
+	0xab01, 0xab06,
+	0xab09, 0xab0e,
+	0xab11, 0xab16,
+	0xab20, 0xab6b,
+	0xab70, 0xabed,
+	0xabf0, 0xabf9,
+	0xac00, 0xd7a3,
+	0xd7b0, 0xd7c6,
+	0xd7cb, 0xd7fb,
+	0xf900, 0xfa6d,
+	0xfa70, 0xfad9,
+	0xfb00, 0xfb06,
+	0xfb13, 0xfb17,
+	0xfb1d, 0xfbc2,
+	0xfbd3, 0xfd8f,
+	0xfd92, 0xfdc7,
+	0xfdcf, 0xfdcf,
+	0xfdf0, 0xfe19,
+	0xfe20, 0xfe6b,
+	0xfe70, 0xfefc,
+	0xff01, 0xffbe,
+	0xffc2, 0xffc7,
+	0xffca, 0xffcf,
+	0xffd2, 0xffd7,
+	0xffda, 0xffdc,
+	0xffe0, 0xffee,
+	0xfffc, 0xfffd,
+}
+
+var isNotPrint16 = []uint16{
+	0x00ad,
+	0x038b,
+	0x038d,
+	0x03a2,
+	0x0530,
+	0x0590,
+	0x061c,
+	0x06dd,
+	0x083f,
+	0x085f,
+	0x08e2,
+	0x0984,
+	0x09a9,
+	0x09b1,
+	0x09de,
+	0x0a04,
+	0x0a29,
+	0x0a31,
+	0x0a34,
+	0x0a37,
+	0x0a3d,
+	0x0a5d,
+	0x0a84,
+	0x0a8e,
+	0x0a92,
+	0x0aa9,
+	0x0ab1,
+	0x0ab4,
+	0x0ac6,
+	0x0aca,
+	0x0b00,
+	0x0b04,
+	0x0b29,
+	0x0b31,
+	0x0b34,
+	0x0b5e,
+	0x0b84,
+	0x0b91,
+	0x0b9b,
+	0x0b9d,
+	0x0bc9,
+	0x0c0d,
+	0x0c11,
+	0x0c29,
+	0x0c45,
+	0x0c49,
+	0x0c57,
+	0x0c8d,
+	0x0c91,
+	0x0ca9,
+	0x0cb4,
+	0x0cc5,
+	0x0cc9,
+	0x0cdf,
+	0x0cf0,
+	0x0d0d,
+	0x0d11,
+	0x0d45,
+	0x0d49,
+	0x0d80,
+	0x0d84,
+	0x0db2,
+	0x0dbc,
+	0x0dd5,
+	0x0dd7,
+	0x0e83,
+	0x0e85,
+	0x0e8b,
+	0x0ea4,
+	0x0ea6,
+	0x0ec5,
+	0x0ec7,
+	0x0ecf,
+	0x0f48,
+	0x0f98,
+	0x0fbd,
+	0x0fcd,
+	0x10c6,
+	0x1249,
+	0x1257,
+	0x1259,
+	0x1289,
+	0x12b1,
+	0x12bf,
+	0x12c1,
+	0x12d7,
+	0x1311,
+	0x1680,
+	0x176d,
+	0x1771,
+	0x180e,
+	0x191f,
+	0x1a5f,
+	0x1b7f,
+	0x1f58,
+	0x1f5a,
+	0x1f5c,
+	0x1f5e,
+	0x1fb5,
+	0x1fc5,
+	0x1fdc,
+	0x1ff5,
+	0x208f,
+	0x2b96,
+	0x2d26,
+	0x2da7,
+	0x2daf,
+	0x2db7,
+	0x2dbf,
+	0x2dc7,
+	0x2dcf,
+	0x2dd7,
+	0x2ddf,
+	0x2e9a,
+	0x3040,
+	0x3130,
+	0x318f,
+	0x321f,
+	0xa7d2,
+	0xa7d4,
+	0xa9ce,
+	0xa9ff,
+	0xab27,
+	0xab2f,
+	0xfb37,
+	0xfb3d,
+	0xfb3f,
+	0xfb42,
+	0xfb45,
+	0xfe53,
+	0xfe67,
+	0xfe75,
+	0xffe7,
+}
+
+var isPrint32 = []uint32{
+	0x010000, 0x01004d,
+	0x010050, 0x01005d,
+	0x010080, 0x0100fa,
+	0x010100, 0x010102,
+	0x010107, 0x010133,
+	0x010137, 0x01019c,
+	0x0101a0, 0x0101a0,
+	0x0101d0, 0x0101fd,
+	0x010280, 0x01029c,
+	0x0102a0, 0x0102d0,
+	0x0102e0, 0x0102fb,
+	0x010300, 0x010323,
+	0x01032d, 0x01034a,
+	0x010350, 0x01037a,
+	0x010380, 0x0103c3,
+	0x0103c8, 0x0103d5,
+	0x010400, 0x01049d,
+	0x0104a0, 0x0104a9,
+	0x0104b0, 0x0104d3,
+	0x0104d8, 0x0104fb,
+	0x010500, 0x010527,
+	0x010530, 0x010563,
+	0x01056f, 0x0105bc,
+	0x010600, 0x010736,
+	0x010740, 0x010755,
+	0x010760, 0x010767,
+	0x010780, 0x0107ba,
+	0x010800, 0x010805,
+	0x010808, 0x010838,
+	0x01083c, 0x01083c,
+	0x01083f, 0x01089e,
+	0x0108a7, 0x0108af,
+	0x0108e0, 0x0108f5,
+	0x0108fb, 0x01091b,
+	0x01091f, 0x010939,
+	0x01093f, 0x01093f,
+	0x010980, 0x0109b7,
+	0x0109bc, 0x0109cf,
+	0x0109d2, 0x010a06,
+	0x010a0c, 0x010a35,
+	0x010a38, 0x010a3a,
+	0x010a3f, 0x010a48,
+	0x010a50, 0x010a58,
+	0x010a60, 0x010a9f,
+	0x010ac0, 0x010ae6,
+	0x010aeb, 0x010af6,
+	0x010b00, 0x010b35,
+	0x010b39, 0x010b55,
+	0x010b58, 0x010b72,
+	0x010b78, 0x010b91,
+	0x010b99, 0x010b9c,
+	0x010ba9, 0x010baf,
+	0x010c00, 0x010c48,
+	0x010c80, 0x010cb2,
+	0x010cc0, 0x010cf2,
+	0x010cfa, 0x010d27,
+	0x010d30, 0x010d39,
+	0x010e60, 0x010ead,
+	0x010eb0, 0x010eb1,
+	0x010efd, 0x010f27,
+	0x010f30, 0x010f59,
+	0x010f70, 0x010f89,
+	0x010fb0, 0x010fcb,
+	0x010fe0, 0x010ff6,
+	0x011000, 0x01104d,
+	0x011052, 0x011075,
+	0x01107f, 0x0110c2,
+	0x0110d0, 0x0110e8,
+	0x0110f0, 0x0110f9,
+	0x011100, 0x011147,
+	0x011150, 0x011176,
+	0x011180, 0x0111f4,
+	0x011200, 0x011241,
+	0x011280, 0x0112a9,
+	0x0112b0, 0x0112ea,
+	0x0112f0, 0x0112f9,
+	0x011300, 0x01130c,
+	0x01130f, 0x011310,
+	0x011313, 0x011344,
+	0x011347, 0x011348,
+	0x01134b, 0x01134d,
+	0x011350, 0x011350,
+	0x011357, 0x011357,
+	0x01135d, 0x011363,
+	0x011366, 0x01136c,
+	0x011370, 0x011374,
+	0x011400, 0x011461,
+	0x011480, 0x0114c7,
+	0x0114d0, 0x0114d9,
+	0x011580, 0x0115b5,
+	0x0115b8, 0x0115dd,
+	0x011600, 0x011644,
+	0x011650, 0x011659,
+	0x011660, 0x01166c,
+	0x011680, 0x0116b9,
+	0x0116c0, 0x0116c9,
+	0x011700, 0x01171a,
+	0x01171d, 0x01172b,
+	0x011730, 0x011746,
+	0x011800, 0x01183b,
+	0x0118a0, 0x0118f2,
+	0x0118ff, 0x011906,
+	0x011909, 0x011909,
+	0x01190c, 0x011938,
+	0x01193b, 0x011946,
+	0x011950, 0x011959,
+	0x0119a0, 0x0119a7,
+	0x0119aa, 0x0119d7,
+	0x0119da, 0x0119e4,
+	0x011a00, 0x011a47,
+	0x011a50, 0x011aa2,
+	0x011ab0, 0x011af8,
+	0x011b00, 0x011b09,
+	0x011c00, 0x011c45,
+	0x011c50, 0x011c6c,
+	0x011c70, 0x011c8f,
+	0x011c92, 0x011cb6,
+	0x011d00, 0x011d36,
+	0x011d3a, 0x011d47,
+	0x011d50, 0x011d59,
+	0x011d60, 0x011d98,
+	0x011da0, 0x011da9,
+	0x011ee0, 0x011ef8,
+	0x011f00, 0x011f3a,
+	0x011f3e, 0x011f59,
+	0x011fb0, 0x011fb0,
+	0x011fc0, 0x011ff1,
+	0x011fff, 0x012399,
+	0x012400, 0x012474,
+	0x012480, 0x012543,
+	0x012f90, 0x012ff2,
+	0x013000, 0x01342f,
+	0x013440, 0x013455,
+	0x014400, 0x014646,
+	0x016800, 0x016a38,
+	0x016a40, 0x016a69,
+	0x016a6e, 0x016ac9,
+	0x016ad0, 0x016aed,
+	0x016af0, 0x016af5,
+	0x016b00, 0x016b45,
+	0x016b50, 0x016b77,
+	0x016b7d, 0x016b8f,
+	0x016e40, 0x016e9a,
+	0x016f00, 0x016f4a,
+	0x016f4f, 0x016f87,
+	0x016f8f, 0x016f9f,
+	0x016fe0, 0x016fe4,
+	0x016ff0, 0x016ff1,
+	0x017000, 0x0187f7,
+	0x018800, 0x018cd5,
+	0x018d00, 0x018d08,
+	0x01aff0, 0x01b122,
+	0x01b132, 0x01b132,
+	0x01b150, 0x01b152,
+	0x01b155, 0x01b155,
+	0x01b164, 0x01b167,
+	0x01b170, 0x01b2fb,
+	0x01bc00, 0x01bc6a,
+	0x01bc70, 0x01bc7c,
+	0x01bc80, 0x01bc88,
+	0x01bc90, 0x01bc99,
+	0x01bc9c, 0x01bc9f,
+	0x01cf00, 0x01cf2d,
+	0x01cf30, 0x01cf46,
+	0x01cf50, 0x01cfc3,
+	0x01d000, 0x01d0f5,
+	0x01d100, 0x01d126,
+	0x01d129, 0x01d172,
+	0x01d17b, 0x01d1ea,
+	0x01d200, 0x01d245,
+	0x01d2c0, 0x01d2d3,
+	0x01d2e0, 0x01d2f3,
+	0x01d300, 0x01d356,
+	0x01d360, 0x01d378,
+	0x01d400, 0x01d49f,
+	0x01d4a2, 0x01d4a2,
+	0x01d4a5, 0x01d4a6,
+	0x01d4a9, 0x01d50a,
+	0x01d50d, 0x01d546,
+	0x01d54a, 0x01d6a5,
+	0x01d6a8, 0x01d7cb,
+	0x01d7ce, 0x01da8b,
+	0x01da9b, 0x01daaf,
+	0x01df00, 0x01df1e,
+	0x01df25, 0x01df2a,
+	0x01e000, 0x01e018,
+	0x01e01b, 0x01e02a,
+	0x01e030, 0x01e06d,
+	0x01e08f, 0x01e08f,
+	0x01e100, 0x01e12c,
+	0x01e130, 0x01e13d,
+	0x01e140, 0x01e149,
+	0x01e14e, 0x01e14f,
+	0x01e290, 0x01e2ae,
+	0x01e2c0, 0x01e2f9,
+	0x01e2ff, 0x01e2ff,
+	0x01e4d0, 0x01e4f9,
+	0x01e7e0, 0x01e8c4,
+	0x01e8c7, 0x01e8d6,
+	0x01e900, 0x01e94b,
+	0x01e950, 0x01e959,
+	0x01e95e, 0x01e95f,
+	0x01ec71, 0x01ecb4,
+	0x01ed01, 0x01ed3d,
+	0x01ee00, 0x01ee24,
+	0x01ee27, 0x01ee3b,
+	0x01ee42, 0x01ee42,
+	0x01ee47, 0x01ee54,
+	0x01ee57, 0x01ee64,
+	0x01ee67, 0x01ee9b,
+	0x01eea1, 0x01eebb,
+	0x01eef0, 0x01eef1,
+	0x01f000, 0x01f02b,
+	0x01f030, 0x01f093,
+	0x01f0a0, 0x01f0ae,
+	0x01f0b1, 0x01f0f5,
+	0x01f100, 0x01f1ad,
+	0x01f1e6, 0x01f202,
+	0x01f210, 0x01f23b,
+	0x01f240, 0x01f248,
+	0x01f250, 0x01f251,
+	0x01f260, 0x01f265,
+	0x01f300, 0x01f6d7,
+	0x01f6dc, 0x01f6ec,
+	0x01f6f0, 0x01f6fc,
+	0x01f700, 0x01f776,
+	0x01f77b, 0x01f7d9,
+	0x01f7e0, 0x01f7eb,
+	0x01f7f0, 0x01f7f0,
+	0x01f800, 0x01f80b,
+	0x01f810, 0x01f847,
+	0x01f850, 0x01f859,
+	0x01f860, 0x01f887,
+	0x01f890, 0x01f8ad,
+	0x01f8b0, 0x01f8b1,
+	0x01f900, 0x01fa53,
+	0x01fa60, 0x01fa6d,
+	0x01fa70, 0x01fa7c,
+	0x01fa80, 0x01fa88,
+	0x01fa90, 0x01fac5,
+	0x01face, 0x01fadb,
+	0x01fae0, 0x01fae8,
+	0x01faf0, 0x01faf8,
+	0x01fb00, 0x01fbca,
+	0x01fbf0, 0x01fbf9,
+	0x020000, 0x02a6df,
+	0x02a700, 0x02b739,
+	0x02b740, 0x02b81d,
+	0x02b820, 0x02cea1,
+	0x02ceb0, 0x02ebe0,
+	0x02f800, 0x02fa1d,
+	0x030000, 0x03134a,
+	0x031350, 0x0323af,
+	0x0e0100, 0x0e01ef,
+}
+
+var isNotPrint32 = []uint16{ // add 0x10000 to each entry
+	0x000c,
+	0x0027,
+	0x003b,
+	0x003e,
+	0x018f,
+	0x039e,
+	0x057b,
+	0x058b,
+	0x0593,
+	0x0596,
+	0x05a2,
+	0x05b2,
+	0x05ba,
+	0x0786,
+	0x07b1,
+	0x0809,
+	0x0836,
+	0x0856,
+	0x08f3,
+	0x0a04,
+	0x0a14,
+	0x0a18,
+	0x0e7f,
+	0x0eaa,
+	0x10bd,
+	0x1135,
+	0x11e0,
+	0x1212,
+	0x1287,
+	0x1289,
+	0x128e,
+	0x129e,
+	0x1304,
+	0x1329,
+	0x1331,
+	0x1334,
+	0x133a,
+	0x145c,
+	0x1914,
+	0x1917,
+	0x1936,
+	0x1c09,
+	0x1c37,
+	0x1ca8,
+	0x1d07,
+	0x1d0a,
+	0x1d3b,
+	0x1d3e,
+	0x1d66,
+	0x1d69,
+	0x1d8f,
+	0x1d92,
+	0x1f11,
+	0x246f,
+	0x6a5f,
+	0x6abf,
+	0x6b5a,
+	0x6b62,
+	0xaff4,
+	0xaffc,
+	0xafff,
+	0xd455,
+	0xd49d,
+	0xd4ad,
+	0xd4ba,
+	0xd4bc,
+	0xd4c4,
+	0xd506,
+	0xd515,
+	0xd51d,
+	0xd53a,
+	0xd53f,
+	0xd545,
+	0xd551,
+	0xdaa0,
+	0xe007,
+	0xe022,
+	0xe025,
+	0xe7e7,
+	0xe7ec,
+	0xe7ef,
+	0xe7ff,
+	0xee04,
+	0xee20,
+	0xee23,
+	0xee28,
+	0xee33,
+	0xee38,
+	0xee3a,
+	0xee48,
+	0xee4a,
+	0xee4c,
+	0xee50,
+	0xee53,
+	0xee58,
+	0xee5a,
+	0xee5c,
+	0xee5e,
+	0xee60,
+	0xee63,
+	0xee6b,
+	0xee73,
+	0xee78,
+	0xee7d,
+	0xee7f,
+	0xee8a,
+	0xeea4,
+	0xeeaa,
+	0xf0c0,
+	0xf0d0,
+	0xfabe,
+	0xfb93,
+}
+
+// isGraphic lists the graphic runes not matched by IsPrint.
+var isGraphic = []uint16{
+	0x00a0,
+	0x1680,
+	0x2000,
+	0x2001,
+	0x2002,
+	0x2003,
+	0x2004,
+	0x2005,
+	0x2006,
+	0x2007,
+	0x2008,
+	0x2009,
+	0x200a,
+	0x202f,
+	0x205f,
+	0x3000,
+}
diff --git a/src/strconv/itoa.go b/src/strconv/itoa.go
new file mode 100644
index 0000000..b0c2666
--- /dev/null
+++ b/src/strconv/itoa.go
@@ -0,0 +1,205 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv
+
+import "math/bits"
+
+const fastSmalls = true // enable fast path for small integers
+
+// FormatUint returns the string representation of i in the given base,
+// for 2 <= base <= 36. The result uses the lower-case letters 'a' to 'z'
+// for digit values >= 10.
+func FormatUint(i uint64, base int) string {
+	if fastSmalls && i < nSmalls && base == 10 {
+		return small(int(i))
+	}
+	_, s := formatBits(nil, i, base, false, false)
+	return s
+}
+
+// FormatInt returns the string representation of i in the given base,
+// for 2 <= base <= 36. The result uses the lower-case letters 'a' to 'z'
+// for digit values >= 10.
+func FormatInt(i int64, base int) string {
+	if fastSmalls && 0 <= i && i < nSmalls && base == 10 {
+		return small(int(i))
+	}
+	_, s := formatBits(nil, uint64(i), base, i < 0, false)
+	return s
+}
+
+// Itoa is equivalent to FormatInt(int64(i), 10).
+func Itoa(i int) string {
+	return FormatInt(int64(i), 10)
+}
+
+// AppendInt appends the string form of the integer i,
+// as generated by FormatInt, to dst and returns the extended buffer.
+func AppendInt(dst []byte, i int64, base int) []byte {
+	if fastSmalls && 0 <= i && i < nSmalls && base == 10 {
+		return append(dst, small(int(i))...)
+	}
+	dst, _ = formatBits(dst, uint64(i), base, i < 0, true)
+	return dst
+}
+
+// AppendUint appends the string form of the unsigned integer i,
+// as generated by FormatUint, to dst and returns the extended buffer.
+func AppendUint(dst []byte, i uint64, base int) []byte {
+	if fastSmalls && i < nSmalls && base == 10 {
+		return append(dst, small(int(i))...)
+	}
+	dst, _ = formatBits(dst, i, base, false, true)
+	return dst
+}
+
+// small returns the string for an i with 0 <= i < nSmalls.
+func small(i int) string {
+	if i < 10 {
+		return digits[i : i+1]
+	}
+	return smallsString[i*2 : i*2+2]
+}
+
+const nSmalls = 100
+
+const smallsString = "00010203040506070809" +
+	"10111213141516171819" +
+	"20212223242526272829" +
+	"30313233343536373839" +
+	"40414243444546474849" +
+	"50515253545556575859" +
+	"60616263646566676869" +
+	"70717273747576777879" +
+	"80818283848586878889" +
+	"90919293949596979899"
+
+const host32bit = ^uint(0)>>32 == 0
+
+const digits = "0123456789abcdefghijklmnopqrstuvwxyz"
+
+// formatBits computes the string representation of u in the given base.
+// If neg is set, u is treated as negative int64 value. If append_ is
+// set, the string is appended to dst and the resulting byte slice is
+// returned as the first result value; otherwise the string is returned
+// as the second result value.
+func formatBits(dst []byte, u uint64, base int, neg, append_ bool) (d []byte, s string) {
+	if base < 2 || base > len(digits) {
+		panic("strconv: illegal AppendInt/FormatInt base")
+	}
+	// 2 <= base && base <= len(digits)
+
+	var a [64 + 1]byte // +1 for sign of 64bit value in base 2
+	i := len(a)
+
+	if neg {
+		u = -u
+	}
+
+	// convert bits
+	// We use uint values where we can because those will
+	// fit into a single register even on a 32bit machine.
+	if base == 10 {
+		// common case: use constants for / because
+		// the compiler can optimize it into a multiply+shift
+
+		if host32bit {
+			// convert the lower digits using 32bit operations
+			for u >= 1e9 {
+				// Avoid using r = a%b in addition to q = a/b
+				// since 64bit division and modulo operations
+				// are calculated by runtime functions on 32bit machines.
+				q := u / 1e9
+				us := uint(u - q*1e9) // u % 1e9 fits into a uint
+				for j := 4; j > 0; j-- {
+					is := us % 100 * 2
+					us /= 100
+					i -= 2
+					a[i+1] = smallsString[is+1]
+					a[i+0] = smallsString[is+0]
+				}
+
+				// us < 10, since it contains the last digit
+				// from the initial 9-digit us.
+				i--
+				a[i] = smallsString[us*2+1]
+
+				u = q
+			}
+			// u < 1e9
+		}
+
+		// u guaranteed to fit into a uint
+		us := uint(u)
+		for us >= 100 {
+			is := us % 100 * 2
+			us /= 100
+			i -= 2
+			a[i+1] = smallsString[is+1]
+			a[i+0] = smallsString[is+0]
+		}
+
+		// us < 100
+		is := us * 2
+		i--
+		a[i] = smallsString[is+1]
+		if us >= 10 {
+			i--
+			a[i] = smallsString[is]
+		}
+
+	} else if isPowerOfTwo(base) {
+		// Use shifts and masks instead of / and %.
+		// Base is a power of 2 and 2 <= base <= len(digits) where len(digits) is 36.
+		// The largest power of 2 below or equal to 36 is 32, which is 1 << 5;
+		// i.e., the largest possible shift count is 5. By &-ind that value with
+		// the constant 7 we tell the compiler that the shift count is always
+		// less than 8 which is smaller than any register width. This allows
+		// the compiler to generate better code for the shift operation.
+		shift := uint(bits.TrailingZeros(uint(base))) & 7
+		b := uint64(base)
+		m := uint(base) - 1 // == 1<<shift - 1
+		for u >= b {
+			i--
+			a[i] = digits[uint(u)&m]
+			u >>= shift
+		}
+		// u < base
+		i--
+		a[i] = digits[uint(u)]
+	} else {
+		// general case
+		b := uint64(base)
+		for u >= b {
+			i--
+			// Avoid using r = a%b in addition to q = a/b
+			// since 64bit division and modulo operations
+			// are calculated by runtime functions on 32bit machines.
+			q := u / b
+			a[i] = digits[uint(u-q*b)]
+			u = q
+		}
+		// u < base
+		i--
+		a[i] = digits[uint(u)]
+	}
+
+	// add sign, if any
+	if neg {
+		i--
+		a[i] = '-'
+	}
+
+	if append_ {
+		d = append(dst, a[i:]...)
+		return
+	}
+	s = string(a[i:])
+	return
+}
+
+func isPowerOfTwo(x int) bool {
+	return x&(x-1) == 0
+}
diff --git a/src/strconv/itoa_test.go b/src/strconv/itoa_test.go
new file mode 100644
index 0000000..b8bc524
--- /dev/null
+++ b/src/strconv/itoa_test.go
@@ -0,0 +1,243 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv_test
+
+import (
+	. "strconv"
+	"testing"
+)
+
+type itob64Test struct {
+	in   int64
+	base int
+	out  string
+}
+
+var itob64tests = []itob64Test{
+	{0, 10, "0"},
+	{1, 10, "1"},
+	{-1, 10, "-1"},
+	{12345678, 10, "12345678"},
+	{-987654321, 10, "-987654321"},
+	{1<<31 - 1, 10, "2147483647"},
+	{-1<<31 + 1, 10, "-2147483647"},
+	{1 << 31, 10, "2147483648"},
+	{-1 << 31, 10, "-2147483648"},
+	{1<<31 + 1, 10, "2147483649"},
+	{-1<<31 - 1, 10, "-2147483649"},
+	{1<<32 - 1, 10, "4294967295"},
+	{-1<<32 + 1, 10, "-4294967295"},
+	{1 << 32, 10, "4294967296"},
+	{-1 << 32, 10, "-4294967296"},
+	{1<<32 + 1, 10, "4294967297"},
+	{-1<<32 - 1, 10, "-4294967297"},
+	{1 << 50, 10, "1125899906842624"},
+	{1<<63 - 1, 10, "9223372036854775807"},
+	{-1<<63 + 1, 10, "-9223372036854775807"},
+	{-1 << 63, 10, "-9223372036854775808"},
+
+	{0, 2, "0"},
+	{10, 2, "1010"},
+	{-1, 2, "-1"},
+	{1 << 15, 2, "1000000000000000"},
+
+	{-8, 8, "-10"},
+	{057635436545, 8, "57635436545"},
+	{1 << 24, 8, "100000000"},
+
+	{16, 16, "10"},
+	{-0x123456789abcdef, 16, "-123456789abcdef"},
+	{1<<63 - 1, 16, "7fffffffffffffff"},
+	{1<<63 - 1, 2, "111111111111111111111111111111111111111111111111111111111111111"},
+	{-1 << 63, 2, "-1000000000000000000000000000000000000000000000000000000000000000"},
+
+	{16, 17, "g"},
+	{25, 25, "10"},
+	{(((((17*35+24)*35+21)*35+34)*35+12)*35+24)*35 + 32, 35, "holycow"},
+	{(((((17*36+24)*36+21)*36+34)*36+12)*36+24)*36 + 32, 36, "holycow"},
+}
+
+func TestItoa(t *testing.T) {
+	for _, test := range itob64tests {
+		s := FormatInt(test.in, test.base)
+		if s != test.out {
+			t.Errorf("FormatInt(%v, %v) = %v want %v",
+				test.in, test.base, s, test.out)
+		}
+		x := AppendInt([]byte("abc"), test.in, test.base)
+		if string(x) != "abc"+test.out {
+			t.Errorf("AppendInt(%q, %v, %v) = %q want %v",
+				"abc", test.in, test.base, x, test.out)
+		}
+
+		if test.in >= 0 {
+			s := FormatUint(uint64(test.in), test.base)
+			if s != test.out {
+				t.Errorf("FormatUint(%v, %v) = %v want %v",
+					test.in, test.base, s, test.out)
+			}
+			x := AppendUint(nil, uint64(test.in), test.base)
+			if string(x) != test.out {
+				t.Errorf("AppendUint(%q, %v, %v) = %q want %v",
+					"abc", uint64(test.in), test.base, x, test.out)
+			}
+		}
+
+		if test.base == 10 && int64(int(test.in)) == test.in {
+			s := Itoa(int(test.in))
+			if s != test.out {
+				t.Errorf("Itoa(%v) = %v want %v",
+					test.in, s, test.out)
+			}
+		}
+	}
+
+	// Override when base is illegal
+	defer func() {
+		if r := recover(); r == nil {
+			t.Fatalf("expected panic due to illegal base")
+		}
+	}()
+	FormatUint(12345678, 1)
+}
+
+type uitob64Test struct {
+	in   uint64
+	base int
+	out  string
+}
+
+var uitob64tests = []uitob64Test{
+	{1<<63 - 1, 10, "9223372036854775807"},
+	{1 << 63, 10, "9223372036854775808"},
+	{1<<63 + 1, 10, "9223372036854775809"},
+	{1<<64 - 2, 10, "18446744073709551614"},
+	{1<<64 - 1, 10, "18446744073709551615"},
+	{1<<64 - 1, 2, "1111111111111111111111111111111111111111111111111111111111111111"},
+}
+
+func TestUitoa(t *testing.T) {
+	for _, test := range uitob64tests {
+		s := FormatUint(test.in, test.base)
+		if s != test.out {
+			t.Errorf("FormatUint(%v, %v) = %v want %v",
+				test.in, test.base, s, test.out)
+		}
+		x := AppendUint([]byte("abc"), test.in, test.base)
+		if string(x) != "abc"+test.out {
+			t.Errorf("AppendUint(%q, %v, %v) = %q want %v",
+				"abc", test.in, test.base, x, test.out)
+		}
+
+	}
+}
+
+var varlenUints = []struct {
+	in  uint64
+	out string
+}{
+	{1, "1"},
+	{12, "12"},
+	{123, "123"},
+	{1234, "1234"},
+	{12345, "12345"},
+	{123456, "123456"},
+	{1234567, "1234567"},
+	{12345678, "12345678"},
+	{123456789, "123456789"},
+	{1234567890, "1234567890"},
+	{12345678901, "12345678901"},
+	{123456789012, "123456789012"},
+	{1234567890123, "1234567890123"},
+	{12345678901234, "12345678901234"},
+	{123456789012345, "123456789012345"},
+	{1234567890123456, "1234567890123456"},
+	{12345678901234567, "12345678901234567"},
+	{123456789012345678, "123456789012345678"},
+	{1234567890123456789, "1234567890123456789"},
+	{12345678901234567890, "12345678901234567890"},
+}
+
+func TestFormatUintVarlen(t *testing.T) {
+	for _, test := range varlenUints {
+		s := FormatUint(test.in, 10)
+		if s != test.out {
+			t.Errorf("FormatUint(%v, 10) = %v want %v", test.in, s, test.out)
+		}
+	}
+}
+
+func BenchmarkFormatInt(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, test := range itob64tests {
+			s := FormatInt(test.in, test.base)
+			BenchSink += len(s)
+		}
+	}
+}
+
+func BenchmarkAppendInt(b *testing.B) {
+	dst := make([]byte, 0, 30)
+	for i := 0; i < b.N; i++ {
+		for _, test := range itob64tests {
+			dst = AppendInt(dst[:0], test.in, test.base)
+			BenchSink += len(dst)
+		}
+	}
+}
+
+func BenchmarkFormatUint(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, test := range uitob64tests {
+			s := FormatUint(test.in, test.base)
+			BenchSink += len(s)
+		}
+	}
+}
+
+func BenchmarkAppendUint(b *testing.B) {
+	dst := make([]byte, 0, 30)
+	for i := 0; i < b.N; i++ {
+		for _, test := range uitob64tests {
+			dst = AppendUint(dst[:0], test.in, test.base)
+			BenchSink += len(dst)
+		}
+	}
+}
+
+func BenchmarkFormatIntSmall(b *testing.B) {
+	smallInts := []int64{7, 42}
+	for _, smallInt := range smallInts {
+		b.Run(Itoa(int(smallInt)), func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				s := FormatInt(smallInt, 10)
+				BenchSink += len(s)
+			}
+		})
+	}
+}
+
+func BenchmarkAppendIntSmall(b *testing.B) {
+	dst := make([]byte, 0, 30)
+	const smallInt = 42
+	for i := 0; i < b.N; i++ {
+		dst = AppendInt(dst[:0], smallInt, 10)
+		BenchSink += len(dst)
+	}
+}
+
+func BenchmarkAppendUintVarlen(b *testing.B) {
+	for _, test := range varlenUints {
+		b.Run(test.out, func(b *testing.B) {
+			dst := make([]byte, 0, 30)
+			for j := 0; j < b.N; j++ {
+				dst = AppendUint(dst[:0], test.in, 10)
+				BenchSink += len(dst)
+			}
+		})
+	}
+}
+
+var BenchSink int // make sure compiler cannot optimize away benchmarks
diff --git a/src/strconv/makeisprint.go b/src/strconv/makeisprint.go
new file mode 100644
index 0000000..ff361e7
--- /dev/null
+++ b/src/strconv/makeisprint.go
@@ -0,0 +1,203 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build ignore
+
+//
+// usage:
+//
+// go run makeisprint.go -output isprint.go
+//
+
+package main
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"go/format"
+	"log"
+	"os"
+	"unicode"
+)
+
+var filename = flag.String("output", "isprint.go", "output file name")
+
+var (
+	range16  []uint16
+	except16 []uint16
+	range32  []uint32
+	except32 []uint32
+)
+
+// bsearch16 returns the smallest i such that a[i] >= x.
+// If there is no such i, bsearch16 returns len(a).
+func bsearch16(a []uint16, x uint16) int {
+	i, j := 0, len(a)
+	for i < j {
+		h := i + (j-i)>>1
+		if a[h] < x {
+			i = h + 1
+		} else {
+			j = h
+		}
+	}
+	return i
+}
+
+// bsearch32 returns the smallest i such that a[i] >= x.
+// If there is no such i, bsearch32 returns len(a).
+func bsearch32(a []uint32, x uint32) int {
+	i, j := 0, len(a)
+	for i < j {
+		h := i + (j-i)>>1
+		if a[h] < x {
+			i = h + 1
+		} else {
+			j = h
+		}
+	}
+	return i
+}
+
+func isPrint(r rune) bool {
+	// Same algorithm, either on uint16 or uint32 value.
+	// First, find first i such that rang[i] >= x.
+	// This is the index of either the start or end of a pair that might span x.
+	// The start is even (rang[i&^1]) and the end is odd (rang[i|1]).
+	// If we find x in a range, make sure x is not in exception list.
+
+	if 0 <= r && r < 1<<16 {
+		rr, rang, except := uint16(r), range16, except16
+		i := bsearch16(rang, rr)
+		if i >= len(rang) || rr < rang[i&^1] || rang[i|1] < rr {
+			return false
+		}
+		j := bsearch16(except, rr)
+		return j >= len(except) || except[j] != rr
+	}
+
+	rr, rang, except := uint32(r), range32, except32
+	i := bsearch32(rang, rr)
+	if i >= len(rang) || rr < rang[i&^1] || rang[i|1] < rr {
+		return false
+	}
+	j := bsearch32(except, rr)
+	return j >= len(except) || except[j] != rr
+}
+
+func scan(min, max rune) (rang, except []uint32) {
+	lo := rune(-1)
+	for i := min; ; i++ {
+		if (i > max || !unicode.IsPrint(i)) && lo >= 0 {
+			// End range, but avoid flip flop.
+			if i+1 <= max && unicode.IsPrint(i+1) {
+				except = append(except, uint32(i))
+				continue
+			}
+			rang = append(rang, uint32(lo), uint32(i-1))
+			lo = -1
+		}
+		if i > max {
+			break
+		}
+		if lo < 0 && unicode.IsPrint(i) {
+			lo = i
+		}
+	}
+	return
+}
+
+func to16(x []uint32) []uint16 {
+	var y []uint16
+	for _, v := range x {
+		if uint32(uint16(v)) != v {
+			panic("bad 32->16 conversion")
+		}
+		y = append(y, uint16(v))
+	}
+	return y
+}
+
+func main() {
+	flag.Parse()
+
+	rang, except := scan(0, 0xFFFF)
+	range16 = to16(rang)
+	except16 = to16(except)
+	range32, except32 = scan(0x10000, unicode.MaxRune)
+
+	for i := rune(0); i <= unicode.MaxRune; i++ {
+		if isPrint(i) != unicode.IsPrint(i) {
+			log.Fatalf("%U: isPrint=%v, want %v\n", i, isPrint(i), unicode.IsPrint(i))
+		}
+	}
+
+	var buf bytes.Buffer
+
+	fmt.Fprintf(&buf, `// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.`+"\n\n")
+	fmt.Fprintf(&buf, "// Code generated by go run makeisprint.go -output isprint.go; DO NOT EDIT.\n\n")
+	fmt.Fprintf(&buf, "package strconv\n\n")
+
+	fmt.Fprintf(&buf, "// (%d+%d+%d)*2 + (%d)*4 = %d bytes\n\n",
+		len(range16), len(except16), len(except32),
+		len(range32),
+		(len(range16)+len(except16)+len(except32))*2+
+			(len(range32))*4)
+
+	fmt.Fprintf(&buf, "var isPrint16 = []uint16{\n")
+	for i := 0; i < len(range16); i += 2 {
+		fmt.Fprintf(&buf, "\t%#04x, %#04x,\n", range16[i], range16[i+1])
+	}
+	fmt.Fprintf(&buf, "}\n\n")
+
+	fmt.Fprintf(&buf, "var isNotPrint16 = []uint16{\n")
+	for _, r := range except16 {
+		fmt.Fprintf(&buf, "\t%#04x,\n", r)
+	}
+	fmt.Fprintf(&buf, "}\n\n")
+
+	fmt.Fprintf(&buf, "var isPrint32 = []uint32{\n")
+	for i := 0; i < len(range32); i += 2 {
+		fmt.Fprintf(&buf, "\t%#06x, %#06x,\n", range32[i], range32[i+1])
+	}
+	fmt.Fprintf(&buf, "}\n\n")
+
+	fmt.Fprintf(&buf, "var isNotPrint32 = []uint16{ // add 0x10000 to each entry\n")
+	for _, r := range except32 {
+		if r >= 0x20000 {
+			log.Fatalf("%U too big for isNotPrint32\n", r)
+		}
+		fmt.Fprintf(&buf, "\t%#04x,\n", r-0x10000)
+	}
+	fmt.Fprintf(&buf, "}\n\n")
+
+	// The list of graphic but not "printable" runes is short. Just make one easy table.
+	fmt.Fprintf(&buf, "// isGraphic lists the graphic runes not matched by IsPrint.\n")
+	fmt.Fprintf(&buf, "var isGraphic = []uint16{\n")
+	for r := rune(0); r <= unicode.MaxRune; r++ {
+		if unicode.IsPrint(r) != unicode.IsGraphic(r) {
+			// Sanity check.
+			if !unicode.IsGraphic(r) {
+				log.Fatalf("%U is printable but not graphic\n", r)
+			}
+			if r > 0xFFFF { // We expect only 16-bit values.
+				log.Fatalf("%U too big for isGraphic\n", r)
+			}
+			fmt.Fprintf(&buf, "\t%#04x,\n", r)
+		}
+	}
+	fmt.Fprintf(&buf, "}\n")
+
+	data, err := format.Source(buf.Bytes())
+	if err != nil {
+		log.Fatal(err)
+	}
+	err = os.WriteFile(*filename, data, 0644)
+	if err != nil {
+		log.Fatal(err)
+	}
+}
diff --git a/src/strconv/quote.go b/src/strconv/quote.go
new file mode 100644
index 0000000..7c38433
--- /dev/null
+++ b/src/strconv/quote.go
@@ -0,0 +1,599 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:generate go run makeisprint.go -output isprint.go
+
+package strconv
+
+import (
+	"unicode/utf8"
+)
+
+const (
+	lowerhex = "0123456789abcdef"
+	upperhex = "0123456789ABCDEF"
+)
+
+// contains reports whether the string contains the byte c.
+func contains(s string, c byte) bool {
+	return index(s, c) != -1
+}
+
+func quoteWith(s string, quote byte, ASCIIonly, graphicOnly bool) string {
+	return string(appendQuotedWith(make([]byte, 0, 3*len(s)/2), s, quote, ASCIIonly, graphicOnly))
+}
+
+func quoteRuneWith(r rune, quote byte, ASCIIonly, graphicOnly bool) string {
+	return string(appendQuotedRuneWith(nil, r, quote, ASCIIonly, graphicOnly))
+}
+
+func appendQuotedWith(buf []byte, s string, quote byte, ASCIIonly, graphicOnly bool) []byte {
+	// Often called with big strings, so preallocate. If there's quoting,
+	// this is conservative but still helps a lot.
+	if cap(buf)-len(buf) < len(s) {
+		nBuf := make([]byte, len(buf), len(buf)+1+len(s)+1)
+		copy(nBuf, buf)
+		buf = nBuf
+	}
+	buf = append(buf, quote)
+	for width := 0; len(s) > 0; s = s[width:] {
+		r := rune(s[0])
+		width = 1
+		if r >= utf8.RuneSelf {
+			r, width = utf8.DecodeRuneInString(s)
+		}
+		if width == 1 && r == utf8.RuneError {
+			buf = append(buf, `\x`...)
+			buf = append(buf, lowerhex[s[0]>>4])
+			buf = append(buf, lowerhex[s[0]&0xF])
+			continue
+		}
+		buf = appendEscapedRune(buf, r, quote, ASCIIonly, graphicOnly)
+	}
+	buf = append(buf, quote)
+	return buf
+}
+
+func appendQuotedRuneWith(buf []byte, r rune, quote byte, ASCIIonly, graphicOnly bool) []byte {
+	buf = append(buf, quote)
+	if !utf8.ValidRune(r) {
+		r = utf8.RuneError
+	}
+	buf = appendEscapedRune(buf, r, quote, ASCIIonly, graphicOnly)
+	buf = append(buf, quote)
+	return buf
+}
+
+func appendEscapedRune(buf []byte, r rune, quote byte, ASCIIonly, graphicOnly bool) []byte {
+	if r == rune(quote) || r == '\\' { // always backslashed
+		buf = append(buf, '\\')
+		buf = append(buf, byte(r))
+		return buf
+	}
+	if ASCIIonly {
+		if r < utf8.RuneSelf && IsPrint(r) {
+			buf = append(buf, byte(r))
+			return buf
+		}
+	} else if IsPrint(r) || graphicOnly && isInGraphicList(r) {
+		return utf8.AppendRune(buf, r)
+	}
+	switch r {
+	case '\a':
+		buf = append(buf, `\a`...)
+	case '\b':
+		buf = append(buf, `\b`...)
+	case '\f':
+		buf = append(buf, `\f`...)
+	case '\n':
+		buf = append(buf, `\n`...)
+	case '\r':
+		buf = append(buf, `\r`...)
+	case '\t':
+		buf = append(buf, `\t`...)
+	case '\v':
+		buf = append(buf, `\v`...)
+	default:
+		switch {
+		case r < ' ' || r == 0x7f:
+			buf = append(buf, `\x`...)
+			buf = append(buf, lowerhex[byte(r)>>4])
+			buf = append(buf, lowerhex[byte(r)&0xF])
+		case !utf8.ValidRune(r):
+			r = 0xFFFD
+			fallthrough
+		case r < 0x10000:
+			buf = append(buf, `\u`...)
+			for s := 12; s >= 0; s -= 4 {
+				buf = append(buf, lowerhex[r>>uint(s)&0xF])
+			}
+		default:
+			buf = append(buf, `\U`...)
+			for s := 28; s >= 0; s -= 4 {
+				buf = append(buf, lowerhex[r>>uint(s)&0xF])
+			}
+		}
+	}
+	return buf
+}
+
+// Quote returns a double-quoted Go string literal representing s. The
+// returned string uses Go escape sequences (\t, \n, \xFF, \u0100) for
+// control characters and non-printable characters as defined by
+// IsPrint.
+func Quote(s string) string {
+	return quoteWith(s, '"', false, false)
+}
+
+// AppendQuote appends a double-quoted Go string literal representing s,
+// as generated by Quote, to dst and returns the extended buffer.
+func AppendQuote(dst []byte, s string) []byte {
+	return appendQuotedWith(dst, s, '"', false, false)
+}
+
+// QuoteToASCII returns a double-quoted Go string literal representing s.
+// The returned string uses Go escape sequences (\t, \n, \xFF, \u0100) for
+// non-ASCII characters and non-printable characters as defined by IsPrint.
+func QuoteToASCII(s string) string {
+	return quoteWith(s, '"', true, false)
+}
+
+// AppendQuoteToASCII appends a double-quoted Go string literal representing s,
+// as generated by QuoteToASCII, to dst and returns the extended buffer.
+func AppendQuoteToASCII(dst []byte, s string) []byte {
+	return appendQuotedWith(dst, s, '"', true, false)
+}
+
+// QuoteToGraphic returns a double-quoted Go string literal representing s.
+// The returned string leaves Unicode graphic characters, as defined by
+// IsGraphic, unchanged and uses Go escape sequences (\t, \n, \xFF, \u0100)
+// for non-graphic characters.
+func QuoteToGraphic(s string) string {
+	return quoteWith(s, '"', false, true)
+}
+
+// AppendQuoteToGraphic appends a double-quoted Go string literal representing s,
+// as generated by QuoteToGraphic, to dst and returns the extended buffer.
+func AppendQuoteToGraphic(dst []byte, s string) []byte {
+	return appendQuotedWith(dst, s, '"', false, true)
+}
+
+// QuoteRune returns a single-quoted Go character literal representing the
+// rune. The returned string uses Go escape sequences (\t, \n, \xFF, \u0100)
+// for control characters and non-printable characters as defined by IsPrint.
+// If r is not a valid Unicode code point, it is interpreted as the Unicode
+// replacement character U+FFFD.
+func QuoteRune(r rune) string {
+	return quoteRuneWith(r, '\'', false, false)
+}
+
+// AppendQuoteRune appends a single-quoted Go character literal representing the rune,
+// as generated by QuoteRune, to dst and returns the extended buffer.
+func AppendQuoteRune(dst []byte, r rune) []byte {
+	return appendQuotedRuneWith(dst, r, '\'', false, false)
+}
+
+// QuoteRuneToASCII returns a single-quoted Go character literal representing
+// the rune. The returned string uses Go escape sequences (\t, \n, \xFF,
+// \u0100) for non-ASCII characters and non-printable characters as defined
+// by IsPrint.
+// If r is not a valid Unicode code point, it is interpreted as the Unicode
+// replacement character U+FFFD.
+func QuoteRuneToASCII(r rune) string {
+	return quoteRuneWith(r, '\'', true, false)
+}
+
+// AppendQuoteRuneToASCII appends a single-quoted Go character literal representing the rune,
+// as generated by QuoteRuneToASCII, to dst and returns the extended buffer.
+func AppendQuoteRuneToASCII(dst []byte, r rune) []byte {
+	return appendQuotedRuneWith(dst, r, '\'', true, false)
+}
+
+// QuoteRuneToGraphic returns a single-quoted Go character literal representing
+// the rune. If the rune is not a Unicode graphic character,
+// as defined by IsGraphic, the returned string will use a Go escape sequence
+// (\t, \n, \xFF, \u0100).
+// If r is not a valid Unicode code point, it is interpreted as the Unicode
+// replacement character U+FFFD.
+func QuoteRuneToGraphic(r rune) string {
+	return quoteRuneWith(r, '\'', false, true)
+}
+
+// AppendQuoteRuneToGraphic appends a single-quoted Go character literal representing the rune,
+// as generated by QuoteRuneToGraphic, to dst and returns the extended buffer.
+func AppendQuoteRuneToGraphic(dst []byte, r rune) []byte {
+	return appendQuotedRuneWith(dst, r, '\'', false, true)
+}
+
+// CanBackquote reports whether the string s can be represented
+// unchanged as a single-line backquoted string without control
+// characters other than tab.
+func CanBackquote(s string) bool {
+	for len(s) > 0 {
+		r, wid := utf8.DecodeRuneInString(s)
+		s = s[wid:]
+		if wid > 1 {
+			if r == '\ufeff' {
+				return false // BOMs are invisible and should not be quoted.
+			}
+			continue // All other multibyte runes are correctly encoded and assumed printable.
+		}
+		if r == utf8.RuneError {
+			return false
+		}
+		if (r < ' ' && r != '\t') || r == '`' || r == '\u007F' {
+			return false
+		}
+	}
+	return true
+}
+
+func unhex(b byte) (v rune, ok bool) {
+	c := rune(b)
+	switch {
+	case '0' <= c && c <= '9':
+		return c - '0', true
+	case 'a' <= c && c <= 'f':
+		return c - 'a' + 10, true
+	case 'A' <= c && c <= 'F':
+		return c - 'A' + 10, true
+	}
+	return
+}
+
+// UnquoteChar decodes the first character or byte in the escaped string
+// or character literal represented by the string s.
+// It returns four values:
+//
+//  1. value, the decoded Unicode code point or byte value;
+//  2. multibyte, a boolean indicating whether the decoded character requires a multibyte UTF-8 representation;
+//  3. tail, the remainder of the string after the character; and
+//  4. an error that will be nil if the character is syntactically valid.
+//
+// The second argument, quote, specifies the type of literal being parsed
+// and therefore which escaped quote character is permitted.
+// If set to a single quote, it permits the sequence \' and disallows unescaped '.
+// If set to a double quote, it permits \" and disallows unescaped ".
+// If set to zero, it does not permit either escape and allows both quote characters to appear unescaped.
+func UnquoteChar(s string, quote byte) (value rune, multibyte bool, tail string, err error) {
+	// easy cases
+	if len(s) == 0 {
+		err = ErrSyntax
+		return
+	}
+	switch c := s[0]; {
+	case c == quote && (quote == '\'' || quote == '"'):
+		err = ErrSyntax
+		return
+	case c >= utf8.RuneSelf:
+		r, size := utf8.DecodeRuneInString(s)
+		return r, true, s[size:], nil
+	case c != '\\':
+		return rune(s[0]), false, s[1:], nil
+	}
+
+	// hard case: c is backslash
+	if len(s) <= 1 {
+		err = ErrSyntax
+		return
+	}
+	c := s[1]
+	s = s[2:]
+
+	switch c {
+	case 'a':
+		value = '\a'
+	case 'b':
+		value = '\b'
+	case 'f':
+		value = '\f'
+	case 'n':
+		value = '\n'
+	case 'r':
+		value = '\r'
+	case 't':
+		value = '\t'
+	case 'v':
+		value = '\v'
+	case 'x', 'u', 'U':
+		n := 0
+		switch c {
+		case 'x':
+			n = 2
+		case 'u':
+			n = 4
+		case 'U':
+			n = 8
+		}
+		var v rune
+		if len(s) < n {
+			err = ErrSyntax
+			return
+		}
+		for j := 0; j < n; j++ {
+			x, ok := unhex(s[j])
+			if !ok {
+				err = ErrSyntax
+				return
+			}
+			v = v<<4 | x
+		}
+		s = s[n:]
+		if c == 'x' {
+			// single-byte string, possibly not UTF-8
+			value = v
+			break
+		}
+		if !utf8.ValidRune(v) {
+			err = ErrSyntax
+			return
+		}
+		value = v
+		multibyte = true
+	case '0', '1', '2', '3', '4', '5', '6', '7':
+		v := rune(c) - '0'
+		if len(s) < 2 {
+			err = ErrSyntax
+			return
+		}
+		for j := 0; j < 2; j++ { // one digit already; two more
+			x := rune(s[j]) - '0'
+			if x < 0 || x > 7 {
+				err = ErrSyntax
+				return
+			}
+			v = (v << 3) | x
+		}
+		s = s[2:]
+		if v > 255 {
+			err = ErrSyntax
+			return
+		}
+		value = v
+	case '\\':
+		value = '\\'
+	case '\'', '"':
+		if c != quote {
+			err = ErrSyntax
+			return
+		}
+		value = rune(c)
+	default:
+		err = ErrSyntax
+		return
+	}
+	tail = s
+	return
+}
+
+// QuotedPrefix returns the quoted string (as understood by Unquote) at the prefix of s.
+// If s does not start with a valid quoted string, QuotedPrefix returns an error.
+func QuotedPrefix(s string) (string, error) {
+	out, _, err := unquote(s, false)
+	return out, err
+}
+
+// Unquote interprets s as a single-quoted, double-quoted,
+// or backquoted Go string literal, returning the string value
+// that s quotes.  (If s is single-quoted, it would be a Go
+// character literal; Unquote returns the corresponding
+// one-character string.)
+func Unquote(s string) (string, error) {
+	out, rem, err := unquote(s, true)
+	if len(rem) > 0 {
+		return "", ErrSyntax
+	}
+	return out, err
+}
+
+// unquote parses a quoted string at the start of the input,
+// returning the parsed prefix, the remaining suffix, and any parse errors.
+// If unescape is true, the parsed prefix is unescaped,
+// otherwise the input prefix is provided verbatim.
+func unquote(in string, unescape bool) (out, rem string, err error) {
+	// Determine the quote form and optimistically find the terminating quote.
+	if len(in) < 2 {
+		return "", in, ErrSyntax
+	}
+	quote := in[0]
+	end := index(in[1:], quote)
+	if end < 0 {
+		return "", in, ErrSyntax
+	}
+	end += 2 // position after terminating quote; may be wrong if escape sequences are present
+
+	switch quote {
+	case '`':
+		switch {
+		case !unescape:
+			out = in[:end] // include quotes
+		case !contains(in[:end], '\r'):
+			out = in[len("`") : end-len("`")] // exclude quotes
+		default:
+			// Carriage return characters ('\r') inside raw string literals
+			// are discarded from the raw string value.
+			buf := make([]byte, 0, end-len("`")-len("\r")-len("`"))
+			for i := len("`"); i < end-len("`"); i++ {
+				if in[i] != '\r' {
+					buf = append(buf, in[i])
+				}
+			}
+			out = string(buf)
+		}
+		// NOTE: Prior implementations did not verify that raw strings consist
+		// of valid UTF-8 characters and we continue to not verify it as such.
+		// The Go specification does not explicitly require valid UTF-8,
+		// but only mention that it is implicitly valid for Go source code
+		// (which must be valid UTF-8).
+		return out, in[end:], nil
+	case '"', '\'':
+		// Handle quoted strings without any escape sequences.
+		if !contains(in[:end], '\\') && !contains(in[:end], '\n') {
+			var valid bool
+			switch quote {
+			case '"':
+				valid = utf8.ValidString(in[len(`"`) : end-len(`"`)])
+			case '\'':
+				r, n := utf8.DecodeRuneInString(in[len("'") : end-len("'")])
+				valid = len("'")+n+len("'") == end && (r != utf8.RuneError || n != 1)
+			}
+			if valid {
+				out = in[:end]
+				if unescape {
+					out = out[1 : end-1] // exclude quotes
+				}
+				return out, in[end:], nil
+			}
+		}
+
+		// Handle quoted strings with escape sequences.
+		var buf []byte
+		in0 := in
+		in = in[1:] // skip starting quote
+		if unescape {
+			buf = make([]byte, 0, 3*end/2) // try to avoid more allocations
+		}
+		for len(in) > 0 && in[0] != quote {
+			// Process the next character,
+			// rejecting any unescaped newline characters which are invalid.
+			r, multibyte, rem, err := UnquoteChar(in, quote)
+			if in[0] == '\n' || err != nil {
+				return "", in0, ErrSyntax
+			}
+			in = rem
+
+			// Append the character if unescaping the input.
+			if unescape {
+				if r < utf8.RuneSelf || !multibyte {
+					buf = append(buf, byte(r))
+				} else {
+					buf = utf8.AppendRune(buf, r)
+				}
+			}
+
+			// Single quoted strings must be a single character.
+			if quote == '\'' {
+				break
+			}
+		}
+
+		// Verify that the string ends with a terminating quote.
+		if !(len(in) > 0 && in[0] == quote) {
+			return "", in0, ErrSyntax
+		}
+		in = in[1:] // skip terminating quote
+
+		if unescape {
+			return string(buf), in, nil
+		}
+		return in0[:len(in0)-len(in)], in, nil
+	default:
+		return "", in, ErrSyntax
+	}
+}
+
+// bsearch16 returns the smallest i such that a[i] >= x.
+// If there is no such i, bsearch16 returns len(a).
+func bsearch16(a []uint16, x uint16) int {
+	i, j := 0, len(a)
+	for i < j {
+		h := i + (j-i)>>1
+		if a[h] < x {
+			i = h + 1
+		} else {
+			j = h
+		}
+	}
+	return i
+}
+
+// bsearch32 returns the smallest i such that a[i] >= x.
+// If there is no such i, bsearch32 returns len(a).
+func bsearch32(a []uint32, x uint32) int {
+	i, j := 0, len(a)
+	for i < j {
+		h := i + (j-i)>>1
+		if a[h] < x {
+			i = h + 1
+		} else {
+			j = h
+		}
+	}
+	return i
+}
+
+// TODO: IsPrint is a local implementation of unicode.IsPrint, verified by the tests
+// to give the same answer. It allows this package not to depend on unicode,
+// and therefore not pull in all the Unicode tables. If the linker were better
+// at tossing unused tables, we could get rid of this implementation.
+// That would be nice.
+
+// IsPrint reports whether the rune is defined as printable by Go, with
+// the same definition as unicode.IsPrint: letters, numbers, punctuation,
+// symbols and ASCII space.
+func IsPrint(r rune) bool {
+	// Fast check for Latin-1
+	if r <= 0xFF {
+		if 0x20 <= r && r <= 0x7E {
+			// All the ASCII is printable from space through DEL-1.
+			return true
+		}
+		if 0xA1 <= r && r <= 0xFF {
+			// Similarly for ¡ through ÿ...
+			return r != 0xAD // ...except for the bizarre soft hyphen.
+		}
+		return false
+	}
+
+	// Same algorithm, either on uint16 or uint32 value.
+	// First, find first i such that isPrint[i] >= x.
+	// This is the index of either the start or end of a pair that might span x.
+	// The start is even (isPrint[i&^1]) and the end is odd (isPrint[i|1]).
+	// If we find x in a range, make sure x is not in isNotPrint list.
+
+	if 0 <= r && r < 1<<16 {
+		rr, isPrint, isNotPrint := uint16(r), isPrint16, isNotPrint16
+		i := bsearch16(isPrint, rr)
+		if i >= len(isPrint) || rr < isPrint[i&^1] || isPrint[i|1] < rr {
+			return false
+		}
+		j := bsearch16(isNotPrint, rr)
+		return j >= len(isNotPrint) || isNotPrint[j] != rr
+	}
+
+	rr, isPrint, isNotPrint := uint32(r), isPrint32, isNotPrint32
+	i := bsearch32(isPrint, rr)
+	if i >= len(isPrint) || rr < isPrint[i&^1] || isPrint[i|1] < rr {
+		return false
+	}
+	if r >= 0x20000 {
+		return true
+	}
+	r -= 0x10000
+	j := bsearch16(isNotPrint, uint16(r))
+	return j >= len(isNotPrint) || isNotPrint[j] != uint16(r)
+}
+
+// IsGraphic reports whether the rune is defined as a Graphic by Unicode. Such
+// characters include letters, marks, numbers, punctuation, symbols, and
+// spaces, from categories L, M, N, P, S, and Zs.
+func IsGraphic(r rune) bool {
+	if IsPrint(r) {
+		return true
+	}
+	return isInGraphicList(r)
+}
+
+// isInGraphicList reports whether the rune is in the isGraphic list. This separation
+// from IsGraphic allows quoteWith to avoid two calls to IsPrint.
+// Should be called only if IsPrint fails.
+func isInGraphicList(r rune) bool {
+	// We know r must fit in 16 bits - see makeisprint.go.
+	if r > 0xFFFF {
+		return false
+	}
+	rr := uint16(r)
+	i := bsearch16(isGraphic, rr)
+	return i < len(isGraphic) && rr == isGraphic[i]
+}
diff --git a/src/strconv/quote_test.go b/src/strconv/quote_test.go
new file mode 100644
index 0000000..fc000de
--- /dev/null
+++ b/src/strconv/quote_test.go
@@ -0,0 +1,384 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv_test
+
+import (
+	. "strconv"
+	"strings"
+	"testing"
+	"unicode"
+)
+
+// Verify that our IsPrint agrees with unicode.IsPrint.
+func TestIsPrint(t *testing.T) {
+	n := 0
+	for r := rune(0); r <= unicode.MaxRune; r++ {
+		if IsPrint(r) != unicode.IsPrint(r) {
+			t.Errorf("IsPrint(%U)=%t incorrect", r, IsPrint(r))
+			n++
+			if n > 10 {
+				return
+			}
+		}
+	}
+}
+
+// Verify that our IsGraphic agrees with unicode.IsGraphic.
+func TestIsGraphic(t *testing.T) {
+	n := 0
+	for r := rune(0); r <= unicode.MaxRune; r++ {
+		if IsGraphic(r) != unicode.IsGraphic(r) {
+			t.Errorf("IsGraphic(%U)=%t incorrect", r, IsGraphic(r))
+			n++
+			if n > 10 {
+				return
+			}
+		}
+	}
+}
+
+type quoteTest struct {
+	in      string
+	out     string
+	ascii   string
+	graphic string
+}
+
+var quotetests = []quoteTest{
+	{"\a\b\f\r\n\t\v", `"\a\b\f\r\n\t\v"`, `"\a\b\f\r\n\t\v"`, `"\a\b\f\r\n\t\v"`},
+	{"\\", `"\\"`, `"\\"`, `"\\"`},
+	{"abc\xffdef", `"abc\xffdef"`, `"abc\xffdef"`, `"abc\xffdef"`},
+	{"\u263a", `"☺"`, `"\u263a"`, `"☺"`},
+	{"\U0010ffff", `"\U0010ffff"`, `"\U0010ffff"`, `"\U0010ffff"`},
+	{"\x04", `"\x04"`, `"\x04"`, `"\x04"`},
+	// Some non-printable but graphic runes. Final column is double-quoted.
+	{"!\u00a0!\u2000!\u3000!", `"!\u00a0!\u2000!\u3000!"`, `"!\u00a0!\u2000!\u3000!"`, "\"!\u00a0!\u2000!\u3000!\""},
+	{"\x7f", `"\x7f"`, `"\x7f"`, `"\x7f"`},
+}
+
+func TestQuote(t *testing.T) {
+	for _, tt := range quotetests {
+		if out := Quote(tt.in); out != tt.out {
+			t.Errorf("Quote(%s) = %s, want %s", tt.in, out, tt.out)
+		}
+		if out := AppendQuote([]byte("abc"), tt.in); string(out) != "abc"+tt.out {
+			t.Errorf("AppendQuote(%q, %s) = %s, want %s", "abc", tt.in, out, "abc"+tt.out)
+		}
+	}
+}
+
+func TestQuoteToASCII(t *testing.T) {
+	for _, tt := range quotetests {
+		if out := QuoteToASCII(tt.in); out != tt.ascii {
+			t.Errorf("QuoteToASCII(%s) = %s, want %s", tt.in, out, tt.ascii)
+		}
+		if out := AppendQuoteToASCII([]byte("abc"), tt.in); string(out) != "abc"+tt.ascii {
+			t.Errorf("AppendQuoteToASCII(%q, %s) = %s, want %s", "abc", tt.in, out, "abc"+tt.ascii)
+		}
+	}
+}
+
+func TestQuoteToGraphic(t *testing.T) {
+	for _, tt := range quotetests {
+		if out := QuoteToGraphic(tt.in); out != tt.graphic {
+			t.Errorf("QuoteToGraphic(%s) = %s, want %s", tt.in, out, tt.graphic)
+		}
+		if out := AppendQuoteToGraphic([]byte("abc"), tt.in); string(out) != "abc"+tt.graphic {
+			t.Errorf("AppendQuoteToGraphic(%q, %s) = %s, want %s", "abc", tt.in, out, "abc"+tt.graphic)
+		}
+	}
+}
+
+func BenchmarkQuote(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		Quote("\a\b\f\r\n\t\v\a\b\f\r\n\t\v\a\b\f\r\n\t\v")
+	}
+}
+
+func BenchmarkQuoteRune(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		QuoteRune('\a')
+	}
+}
+
+var benchQuoteBuf []byte
+
+func BenchmarkAppendQuote(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		benchQuoteBuf = AppendQuote(benchQuoteBuf[:0], "\a\b\f\r\n\t\v\a\b\f\r\n\t\v\a\b\f\r\n\t\v")
+	}
+}
+
+var benchQuoteRuneBuf []byte
+
+func BenchmarkAppendQuoteRune(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		benchQuoteRuneBuf = AppendQuoteRune(benchQuoteRuneBuf[:0], '\a')
+	}
+}
+
+type quoteRuneTest struct {
+	in      rune
+	out     string
+	ascii   string
+	graphic string
+}
+
+var quoterunetests = []quoteRuneTest{
+	{'a', `'a'`, `'a'`, `'a'`},
+	{'\a', `'\a'`, `'\a'`, `'\a'`},
+	{'\\', `'\\'`, `'\\'`, `'\\'`},
+	{0xFF, `'ÿ'`, `'\u00ff'`, `'ÿ'`},
+	{0x263a, `'☺'`, `'\u263a'`, `'☺'`},
+	{0xdead, `'�'`, `'\ufffd'`, `'�'`},
+	{0xfffd, `'�'`, `'\ufffd'`, `'�'`},
+	{0x0010ffff, `'\U0010ffff'`, `'\U0010ffff'`, `'\U0010ffff'`},
+	{0x0010ffff + 1, `'�'`, `'\ufffd'`, `'�'`},
+	{0x04, `'\x04'`, `'\x04'`, `'\x04'`},
+	// Some differences between graphic and printable. Note the last column is double-quoted.
+	{'\u00a0', `'\u00a0'`, `'\u00a0'`, "'\u00a0'"},
+	{'\u2000', `'\u2000'`, `'\u2000'`, "'\u2000'"},
+	{'\u3000', `'\u3000'`, `'\u3000'`, "'\u3000'"},
+}
+
+func TestQuoteRune(t *testing.T) {
+	for _, tt := range quoterunetests {
+		if out := QuoteRune(tt.in); out != tt.out {
+			t.Errorf("QuoteRune(%U) = %s, want %s", tt.in, out, tt.out)
+		}
+		if out := AppendQuoteRune([]byte("abc"), tt.in); string(out) != "abc"+tt.out {
+			t.Errorf("AppendQuoteRune(%q, %U) = %s, want %s", "abc", tt.in, out, "abc"+tt.out)
+		}
+	}
+}
+
+func TestQuoteRuneToASCII(t *testing.T) {
+	for _, tt := range quoterunetests {
+		if out := QuoteRuneToASCII(tt.in); out != tt.ascii {
+			t.Errorf("QuoteRuneToASCII(%U) = %s, want %s", tt.in, out, tt.ascii)
+		}
+		if out := AppendQuoteRuneToASCII([]byte("abc"), tt.in); string(out) != "abc"+tt.ascii {
+			t.Errorf("AppendQuoteRuneToASCII(%q, %U) = %s, want %s", "abc", tt.in, out, "abc"+tt.ascii)
+		}
+	}
+}
+
+func TestQuoteRuneToGraphic(t *testing.T) {
+	for _, tt := range quoterunetests {
+		if out := QuoteRuneToGraphic(tt.in); out != tt.graphic {
+			t.Errorf("QuoteRuneToGraphic(%U) = %s, want %s", tt.in, out, tt.graphic)
+		}
+		if out := AppendQuoteRuneToGraphic([]byte("abc"), tt.in); string(out) != "abc"+tt.graphic {
+			t.Errorf("AppendQuoteRuneToGraphic(%q, %U) = %s, want %s", "abc", tt.in, out, "abc"+tt.graphic)
+		}
+	}
+}
+
+type canBackquoteTest struct {
+	in  string
+	out bool
+}
+
+var canbackquotetests = []canBackquoteTest{
+	{"`", false},
+	{string(rune(0)), false},
+	{string(rune(1)), false},
+	{string(rune(2)), false},
+	{string(rune(3)), false},
+	{string(rune(4)), false},
+	{string(rune(5)), false},
+	{string(rune(6)), false},
+	{string(rune(7)), false},
+	{string(rune(8)), false},
+	{string(rune(9)), true}, // \t
+	{string(rune(10)), false},
+	{string(rune(11)), false},
+	{string(rune(12)), false},
+	{string(rune(13)), false},
+	{string(rune(14)), false},
+	{string(rune(15)), false},
+	{string(rune(16)), false},
+	{string(rune(17)), false},
+	{string(rune(18)), false},
+	{string(rune(19)), false},
+	{string(rune(20)), false},
+	{string(rune(21)), false},
+	{string(rune(22)), false},
+	{string(rune(23)), false},
+	{string(rune(24)), false},
+	{string(rune(25)), false},
+	{string(rune(26)), false},
+	{string(rune(27)), false},
+	{string(rune(28)), false},
+	{string(rune(29)), false},
+	{string(rune(30)), false},
+	{string(rune(31)), false},
+	{string(rune(0x7F)), false},
+	{`' !"#$%&'()*+,-./:;<=>?@[\]^_{|}~`, true},
+	{`0123456789`, true},
+	{`ABCDEFGHIJKLMNOPQRSTUVWXYZ`, true},
+	{`abcdefghijklmnopqrstuvwxyz`, true},
+	{`☺`, true},
+	{"\x80", false},
+	{"a\xe0\xa0z", false},
+	{"\ufeffabc", false},
+	{"a\ufeffz", false},
+}
+
+func TestCanBackquote(t *testing.T) {
+	for _, tt := range canbackquotetests {
+		if out := CanBackquote(tt.in); out != tt.out {
+			t.Errorf("CanBackquote(%q) = %v, want %v", tt.in, out, tt.out)
+		}
+	}
+}
+
+type unQuoteTest struct {
+	in  string
+	out string
+}
+
+var unquotetests = []unQuoteTest{
+	{`""`, ""},
+	{`"a"`, "a"},
+	{`"abc"`, "abc"},
+	{`"☺"`, "☺"},
+	{`"hello world"`, "hello world"},
+	{`"\xFF"`, "\xFF"},
+	{`"\377"`, "\377"},
+	{`"\u1234"`, "\u1234"},
+	{`"\U00010111"`, "\U00010111"},
+	{`"\U0001011111"`, "\U0001011111"},
+	{`"\a\b\f\n\r\t\v\\\""`, "\a\b\f\n\r\t\v\\\""},
+	{`"'"`, "'"},
+
+	{`'a'`, "a"},
+	{`'☹'`, "☹"},
+	{`'\a'`, "\a"},
+	{`'\x10'`, "\x10"},
+	{`'\377'`, "\377"},
+	{`'\u1234'`, "\u1234"},
+	{`'\U00010111'`, "\U00010111"},
+	{`'\t'`, "\t"},
+	{`' '`, " "},
+	{`'\''`, "'"},
+	{`'"'`, "\""},
+
+	{"``", ``},
+	{"`a`", `a`},
+	{"`abc`", `abc`},
+	{"`☺`", `☺`},
+	{"`hello world`", `hello world`},
+	{"`\\xFF`", `\xFF`},
+	{"`\\377`", `\377`},
+	{"`\\`", `\`},
+	{"`\n`", "\n"},
+	{"`	`", `	`},
+	{"` `", ` `},
+	{"`a\rb`", "ab"},
+}
+
+var misquoted = []string{
+	``,
+	`"`,
+	`"a`,
+	`"'`,
+	`b"`,
+	`"\"`,
+	`"\9"`,
+	`"\19"`,
+	`"\129"`,
+	`'\'`,
+	`'\9'`,
+	`'\19'`,
+	`'\129'`,
+	`'ab'`,
+	`"\x1!"`,
+	`"\U12345678"`,
+	`"\z"`,
+	"`",
+	"`xxx",
+	"``x\r",
+	"`\"",
+	`"\'"`,
+	`'\"'`,
+	"\"\n\"",
+	"\"\\n\n\"",
+	"'\n'",
+	`"\udead"`,
+	`"\ud83d\ude4f"`,
+}
+
+func TestUnquote(t *testing.T) {
+	for _, tt := range unquotetests {
+		testUnquote(t, tt.in, tt.out, nil)
+	}
+	for _, tt := range quotetests {
+		testUnquote(t, tt.out, tt.in, nil)
+	}
+	for _, s := range misquoted {
+		testUnquote(t, s, "", ErrSyntax)
+	}
+}
+
+// Issue 23685: invalid UTF-8 should not go through the fast path.
+func TestUnquoteInvalidUTF8(t *testing.T) {
+	tests := []struct {
+		in string
+
+		// one of:
+		want    string
+		wantErr error
+	}{
+		{in: `"foo"`, want: "foo"},
+		{in: `"foo`, wantErr: ErrSyntax},
+		{in: `"` + "\xc0" + `"`, want: "\xef\xbf\xbd"},
+		{in: `"a` + "\xc0" + `"`, want: "a\xef\xbf\xbd"},
+		{in: `"\t` + "\xc0" + `"`, want: "\t\xef\xbf\xbd"},
+	}
+	for _, tt := range tests {
+		testUnquote(t, tt.in, tt.want, tt.wantErr)
+	}
+}
+
+func testUnquote(t *testing.T, in, want string, wantErr error) {
+	// Test Unquote.
+	got, gotErr := Unquote(in)
+	if got != want || gotErr != wantErr {
+		t.Errorf("Unquote(%q) = (%q, %v), want (%q, %v)", in, got, gotErr, want, wantErr)
+	}
+
+	// Test QuotedPrefix.
+	// Adding an arbitrary suffix should not change the result of QuotedPrefix
+	// assume that the suffix doesn't accidentally terminate a truncated input.
+	if gotErr == nil {
+		want = in
+	}
+	suffix := "\n\r\\\"`'" // special characters for quoted strings
+	if len(in) > 0 {
+		suffix = strings.ReplaceAll(suffix, in[:1], "")
+	}
+	in += suffix
+	got, gotErr = QuotedPrefix(in)
+	if gotErr == nil && wantErr != nil {
+		_, wantErr = Unquote(got) // original input had trailing junk, reparse with only valid prefix
+		want = got
+	}
+	if got != want || gotErr != wantErr {
+		t.Errorf("QuotedPrefix(%q) = (%q, %v), want (%q, %v)", in, got, gotErr, want, wantErr)
+	}
+}
+
+func BenchmarkUnquoteEasy(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		Unquote(`"Give me a rock, paper and scissors and I will move the world."`)
+	}
+}
+
+func BenchmarkUnquoteHard(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		Unquote(`"\x47ive me a \x72ock, \x70aper and \x73cissors and \x49 will move the world."`)
+	}
+}
diff --git a/src/strconv/strconv_test.go b/src/strconv/strconv_test.go
new file mode 100644
index 0000000..41b8fa7
--- /dev/null
+++ b/src/strconv/strconv_test.go
@@ -0,0 +1,160 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv_test
+
+import (
+	"runtime"
+	. "strconv"
+	"strings"
+	"testing"
+)
+
+var (
+	globalBuf [64]byte
+	nextToOne = "1.00000000000000011102230246251565404236316680908203125" + strings.Repeat("0", 10000) + "1"
+
+	mallocTest = []struct {
+		count int
+		desc  string
+		fn    func()
+	}{
+		{0, `AppendInt(localBuf[:0], 123, 10)`, func() {
+			var localBuf [64]byte
+			AppendInt(localBuf[:0], 123, 10)
+		}},
+		{0, `AppendInt(globalBuf[:0], 123, 10)`, func() { AppendInt(globalBuf[:0], 123, 10) }},
+		{0, `AppendFloat(localBuf[:0], 1.23, 'g', 5, 64)`, func() {
+			var localBuf [64]byte
+			AppendFloat(localBuf[:0], 1.23, 'g', 5, 64)
+		}},
+		{0, `AppendFloat(globalBuf[:0], 1.23, 'g', 5, 64)`, func() { AppendFloat(globalBuf[:0], 1.23, 'g', 5, 64) }},
+		// In practice we see 7 for the next one, but allow some slop.
+		// Before pre-allocation in appendQuotedWith, we saw 39.
+		{10, `AppendQuoteToASCII(nil, oneMB)`, func() { AppendQuoteToASCII(nil, string(oneMB)) }},
+		{0, `ParseFloat("123.45", 64)`, func() { ParseFloat("123.45", 64) }},
+		{0, `ParseFloat("123.456789123456789", 64)`, func() { ParseFloat("123.456789123456789", 64) }},
+		{0, `ParseFloat("1.000000000000000111022302462515654042363166809082031251", 64)`, func() {
+			ParseFloat("1.000000000000000111022302462515654042363166809082031251", 64)
+		}},
+		{0, `ParseFloat("1.0000000000000001110223024625156540423631668090820312500...001", 64)`, func() {
+			ParseFloat(nextToOne, 64)
+		}},
+	}
+)
+
+var oneMB []byte // Will be allocated to 1MB of random data by TestCountMallocs.
+
+func TestCountMallocs(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping malloc count in short mode")
+	}
+	if runtime.GOMAXPROCS(0) > 1 {
+		t.Skip("skipping; GOMAXPROCS>1")
+	}
+	// Allocate a big messy buffer for AppendQuoteToASCII's test.
+	oneMB = make([]byte, 1e6)
+	for i := range oneMB {
+		oneMB[i] = byte(i)
+	}
+	for _, mt := range mallocTest {
+		allocs := testing.AllocsPerRun(100, mt.fn)
+		if max := float64(mt.count); allocs > max {
+			t.Errorf("%s: %v allocs, want <=%v", mt.desc, allocs, max)
+		}
+	}
+}
+
+// Sink makes sure the compiler cannot optimize away the benchmarks.
+var Sink struct {
+	Bool       bool
+	Int        int
+	Int64      int64
+	Uint64     uint64
+	Float64    float64
+	Complex128 complex128
+	Error      error
+	Bytes      []byte
+}
+
+func TestAllocationsFromBytes(t *testing.T) {
+	const runsPerTest = 100
+	bytes := struct{ Bool, Number, String, Buffer []byte }{
+		Bool:   []byte("false"),
+		Number: []byte("123456789"),
+		String: []byte("hello, world!"),
+		Buffer: make([]byte, 1024),
+	}
+
+	checkNoAllocs := func(f func()) func(t *testing.T) {
+		return func(t *testing.T) {
+			t.Helper()
+			if allocs := testing.AllocsPerRun(runsPerTest, f); allocs != 0 {
+				t.Errorf("got %v allocs, want 0 allocs", allocs)
+			}
+		}
+	}
+
+	t.Run("Atoi", checkNoAllocs(func() {
+		Sink.Int, Sink.Error = Atoi(string(bytes.Number))
+	}))
+	t.Run("ParseBool", checkNoAllocs(func() {
+		Sink.Bool, Sink.Error = ParseBool(string(bytes.Bool))
+	}))
+	t.Run("ParseInt", checkNoAllocs(func() {
+		Sink.Int64, Sink.Error = ParseInt(string(bytes.Number), 10, 64)
+	}))
+	t.Run("ParseUint", checkNoAllocs(func() {
+		Sink.Uint64, Sink.Error = ParseUint(string(bytes.Number), 10, 64)
+	}))
+	t.Run("ParseFloat", checkNoAllocs(func() {
+		Sink.Float64, Sink.Error = ParseFloat(string(bytes.Number), 64)
+	}))
+	t.Run("ParseComplex", checkNoAllocs(func() {
+		Sink.Complex128, Sink.Error = ParseComplex(string(bytes.Number), 128)
+	}))
+	t.Run("CanBackquote", checkNoAllocs(func() {
+		Sink.Bool = CanBackquote(string(bytes.String))
+	}))
+	t.Run("AppendQuote", checkNoAllocs(func() {
+		Sink.Bytes = AppendQuote(bytes.Buffer[:0], string(bytes.String))
+	}))
+	t.Run("AppendQuoteToASCII", checkNoAllocs(func() {
+		Sink.Bytes = AppendQuoteToASCII(bytes.Buffer[:0], string(bytes.String))
+	}))
+	t.Run("AppendQuoteToGraphic", checkNoAllocs(func() {
+		Sink.Bytes = AppendQuoteToGraphic(bytes.Buffer[:0], string(bytes.String))
+	}))
+}
+
+func TestErrorPrefixes(t *testing.T) {
+	_, errInt := Atoi("INVALID")
+	_, errBool := ParseBool("INVALID")
+	_, errFloat := ParseFloat("INVALID", 64)
+	_, errInt64 := ParseInt("INVALID", 10, 64)
+	_, errUint64 := ParseUint("INVALID", 10, 64)
+
+	vectors := []struct {
+		err  error  // Input error
+		want string // Function name wanted
+	}{
+		{errInt, "Atoi"},
+		{errBool, "ParseBool"},
+		{errFloat, "ParseFloat"},
+		{errInt64, "ParseInt"},
+		{errUint64, "ParseUint"},
+	}
+
+	for _, v := range vectors {
+		nerr, ok := v.err.(*NumError)
+		if !ok {
+			t.Errorf("test %s, error was not a *NumError", v.want)
+			continue
+		}
+		if got := nerr.Func; got != v.want {
+			t.Errorf("mismatching Func: got %s, want %s", got, v.want)
+		}
+	}
+
+}
diff --git a/src/strconv/testdata/testfp.txt b/src/strconv/testdata/testfp.txt
new file mode 100644
index 0000000..08d3c4e
--- /dev/null
+++ b/src/strconv/testdata/testfp.txt
@@ -0,0 +1,181 @@
+# Floating-point conversion test cases.
+# Empty lines and lines beginning with # are ignored.
+# The rest have four fields per line: type, format, input, and output.
+# The input is given either in decimal or binary scientific notation.
+# The output is the string that should be produced by formatting the
+# input with the given format.
+#
+# The formats are as in C's printf, except that %b means print
+# binary scientific notation: NpE = N x 2^E.
+
+# TODO:
+#	Powers of 10.
+#	Powers of 2.
+#	%.20g versions.
+#	random sources
+#	random targets
+#	random targets ± half a ULP
+
+# Difficult boundary cases, derived from tables given in
+#	Vern Paxson, A Program for Testing IEEE Decimal-Binary Conversion
+#	ftp://ftp.ee.lbl.gov/testbase-report.ps.Z
+
+# Table 1: Stress Inputs for Conversion to 53-bit Binary, < 1/2 ULP
+float64 %b 5e+125 6653062250012735p+365
+float64 %b 69e+267 4705683757438170p+841
+float64 %b 999e-026 6798841691080350p-129
+float64 %b 7861e-034 8975675289889240p-153
+float64 %b 75569e-254 6091718967192243p-880
+float64 %b 928609e-261 7849264900213743p-900
+float64 %b 9210917e+080 8341110837370930p+236
+float64 %b 84863171e+114 4625202867375927p+353
+float64 %b 653777767e+273 5068902999763073p+884
+float64 %b 5232604057e-298 5741343011915040p-1010
+float64 %b 27235667517e-109 6707124626673586p-380
+float64 %b 653532977297e-123 7078246407265384p-422
+float64 %b 3142213164987e-294 8219991337640559p-988
+float64 %b 46202199371337e-072 5224462102115359p-246
+float64 %b 231010996856685e-073 5224462102115359p-247
+float64 %b 9324754620109615e+212 5539753864394442p+705
+float64 %b 78459735791271921e+049 8388176519442766p+166
+float64 %b 272104041512242479e+200 5554409530847367p+670
+float64 %b 6802601037806061975e+198 5554409530847367p+668
+float64 %b 20505426358836677347e-221 4524032052079546p-722
+float64 %b 836168422905420598437e-234 5070963299887562p-760
+float64 %b 4891559871276714924261e+222 6452687840519111p+757
+
+# Table 2: Stress Inputs for Conversion to 53-bit Binary, > 1/2 ULP
+float64 %b 9e-265 8168427841980010p-930
+float64 %b 85e-037 6360455125664090p-169
+float64 %b 623e+100 6263531988747231p+289
+float64 %b 3571e+263 6234526311072170p+833
+float64 %b 81661e+153 6696636728760206p+472
+float64 %b 920657e-023 5975405561110124p-109
+float64 %b 4603285e-024 5975405561110124p-110
+float64 %b 87575437e-309 8452160731874668p-1053
+float64 %b 245540327e+122 4985336549131723p+381
+float64 %b 6138508175e+120 4985336549131723p+379
+float64 %b 83356057653e+193 5986732817132056p+625
+float64 %b 619534293513e+124 4798406992060657p+399
+float64 %b 2335141086879e+218 5419088166961646p+713
+float64 %b 36167929443327e-159 8135819834632444p-536
+float64 %b 609610927149051e-255 4576664294594737p-850
+float64 %b 3743626360493413e-165 6898586531774201p-549
+float64 %b 94080055902682397e-242 6273271706052298p-800
+float64 %b 899810892172646163e+283 7563892574477827p+947
+float64 %b 7120190517612959703e+120 5385467232557565p+409
+float64 %b 25188282901709339043e-252 5635662608542340p-825
+float64 %b 308984926168550152811e-052 5644774693823803p-157
+float64 %b 6372891218502368041059e+064 4616868614322430p+233
+
+# Table 3: Stress Inputs for Converting 53-bit Binary to Decimal, < 1/2 ULP
+float64 %.0e 8511030020275656p-342 9e-88
+float64 %.1e 5201988407066741p-824 4.6e-233
+float64 %.2e 6406892948269899p+237 1.41e+87
+float64 %.3e 8431154198732492p+72 3.981e+37
+float64 %.4e 6475049196144587p+99 4.1040e+45
+float64 %.5e 8274307542972842p+726 2.92084e+234
+float64 %.6e 5381065484265332p-456 2.891946e-122
+float64 %.7e 6761728585499734p-1057 4.3787718e-303
+float64 %.8e 7976538478610756p+376 1.22770163e+129
+float64 %.9e 5982403858958067p+377 1.841552452e+129
+float64 %.10e 5536995190630837p+93 5.4835744350e+43
+float64 %.11e 7225450889282194p+710 3.89190181146e+229
+float64 %.12e 7225450889282194p+709 1.945950905732e+229
+float64 %.13e 8703372741147379p+117 1.4460958381605e+51
+float64 %.14e 8944262675275217p-1001 4.17367747458531e-286
+float64 %.15e 7459803696087692p-707 1.107950772878888e-197
+float64 %.16e 6080469016670379p-381 1.2345501366327440e-99
+float64 %.17e 8385515147034757p+721 9.25031711960365024e+232
+float64 %.18e 7514216811389786p-828 4.198047150284889840e-234
+float64 %.19e 8397297803260511p-345 1.1716315319786511046e-88
+float64 %.20e 6733459239310543p+202 4.32810072844612493629e+76
+float64 %.21e 8091450587292794p-473 3.317710118160031081518e-127
+
+# Table 4: Stress Inputs for Converting 53-bit Binary to Decimal, > 1/2 ULP
+float64 %.0e 6567258882077402p+952 3e+302
+float64 %.1e 6712731423444934p+535 7.6e+176
+float64 %.2e 6712731423444934p+534 3.78e+176
+float64 %.3e 5298405411573037p-957 4.350e-273
+float64 %.4e 5137311167659507p-144 2.3037e-28
+float64 %.5e 6722280709661868p+363 1.26301e+125
+float64 %.6e 5344436398034927p-169 7.142211e-36
+float64 %.7e 8369123604277281p-853 1.3934574e-241
+float64 %.8e 8995822108487663p-780 1.41463449e-219
+float64 %.9e 8942832835564782p-383 4.539277920e-100
+float64 %.10e 8942832835564782p-384 2.2696389598e-100
+float64 %.11e 8942832835564782p-385 1.13481947988e-100
+float64 %.12e 6965949469487146p-249 7.700366561890e-60
+float64 %.13e 6965949469487146p-250 3.8501832809448e-60
+float64 %.14e 6965949469487146p-251 1.92509164047238e-60
+float64 %.15e 7487252720986826p+548 6.898586531774201e+180
+float64 %.16e 5592117679628511p+164 1.3076622631878654e+65
+float64 %.17e 8887055249355788p+665 1.36052020756121240e+216
+float64 %.18e 6994187472632449p+690 3.592810217475959676e+223
+float64 %.19e 8797576579012143p+588 8.9125197712484551899e+192
+float64 %.20e 7363326733505337p+272 5.58769757362301140950e+97
+float64 %.21e 8549497411294502p-448 1.176257830728540379990e-119
+
+# Table 14: Stress Inputs for Conversion to 24-bit Binary, <1/2 ULP
+# NOTE: The lines with exponent p-149 have been changed from the
+# paper.  Those entries originally read p-150 and had a mantissa
+# twice as large (and even), but IEEE single-precision has no p-150:
+# that's the start of the denormals.
+float32 %b 5e-20 15474250p-88
+float32 %b 67e+14 12479722p+29
+float32 %b 985e+15 14333636p+36
+# float32 %b 7693e-42 10979816p-150
+float32 %b 7693e-42 5489908p-149
+float32 %b 55895e-16 12888509p-61
+# float32 %b 996622e-44 14224264p-150
+float32 %b 996622e-44 7112132p-149
+float32 %b 7038531e-32 11420669p-107
+# float32 %b 60419369e-46 8623340p-150
+float32 %b 60419369e-46 4311670p-149
+float32 %b 702990899e-20 16209866p-61
+# float32 %b 6930161142e-48 9891056p-150
+float32 %b 6930161142e-48 4945528p-149
+float32 %b 25933168707e+13 14395800p+54
+float32 %b 596428896559e+20 12333860p+82
+
+# Table 15: Stress Inputs for Conversion to 24-bit Binary, >1/2 ULP
+float32 %b 3e-23 9507380p-98
+float32 %b 57e+18 12960300p+42
+float32 %b 789e-35 10739312p-130
+float32 %b 2539e-18 11990089p-72
+float32 %b 76173e+28 9845130p+86
+float32 %b 887745e-11 9760860p-40
+float32 %b 5382571e-37 11447463p-124
+float32 %b 82381273e-35 8554961p-113
+float32 %b 750486563e-38 9975678p-120
+float32 %b 3752432815e-39 9975678p-121
+float32 %b 75224575729e-45 13105970p-137
+float32 %b 459926601011e+15 12466336p+65
+
+# Table 16: Stress Inputs for Converting 24-bit Binary to Decimal, < 1/2 ULP
+float32 %.0e 12676506p-102 2e-24
+float32 %.1e 12676506p-103 1.2e-24
+float32 %.2e 15445013p+86 1.19e+33
+float32 %.3e 13734123p-138 3.941e-35
+float32 %.4e 12428269p-130 9.1308e-33
+float32 %.5e 15334037p-146 1.71900e-37
+float32 %.6e 11518287p-41 5.237910e-06
+float32 %.7e 12584953p-145 2.8216440e-37
+float32 %.8e 15961084p-125 3.75243281e-31
+float32 %.9e 14915817p-146 1.672120916e-37
+float32 %.10e 10845484p-102 2.1388945814e-24
+float32 %.11e 16431059p-61 7.12583594561e-12
+
+# Table 17: Stress Inputs for Converting 24-bit Binary to Decimal, > 1/2 ULP
+float32 %.0e 16093626p+69 1e+28
+float32 %.1e 9983778p+25 3.4e+14
+float32 %.2e 12745034p+104 2.59e+38
+float32 %.3e 12706553p+72 6.001e+28
+float32 %.4e 11005028p+45 3.8721e+20
+float32 %.5e 15059547p+71 3.55584e+28
+float32 %.6e 16015691p-99 2.526831e-23
+float32 %.7e 8667859p+56 6.2458507e+23
+float32 %.8e 14855922p-82 3.07213267e-18
+float32 %.9e 14855922p-83 1.536066333e-18
+float32 %.10e 10144164p-110 7.8147796834e-27
+float32 %.11e 13248074p+95 5.24810279937e+35