Adding upstream version 1.16.10.upstream/1.16.10upstream

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

1 files changed, 206 insertions, 0 deletions

diff --git a/src/strconv/itoa.go b/src/strconv/itoa.go
new file mode 100644
index 0000000..45e4192
--- /dev/null
+++ b/src/strconv/itoa.go
@@ -0,0 +1,206 @@
+// 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
+}