Adding upstream version 1.17.13.upstream/1.17.13upstream

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

1 files changed, 415 insertions, 0 deletions

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
+}