use grisu2 for formatting (#347)

port grisu2 formatter from redis src

cmd_sorted_set_test.go

@@ -213,7 +213,7 @@ func TestSortedSetAdd(t *testing.T) {
 
 		mustDo(t, c,
 			"ZADD", "z", "INCR", "XX", "1.2", "one",
-			proto.String("3.6"),
+			proto.String("3.5999999999999996"),
 		)
 
 		mustNil(t, c,

fpconv/LICENSE.txt

@@ -0,0 +1,26 @@
+This code is derived from the C code in redis-7.2.0/deps/fpconv/*, which has
+this license:
+
+Boost Software License - Version 1.0 - August 17th, 2003
+
+Permission is hereby granted, free of charge, to any person or organization
+obtaining a copy of the software and accompanying documentation covered by
+this license (the "Software") to use, reproduce, display, distribute,
+execute, and transmit the Software, and to prepare derivative works of the
+Software, and to permit third-parties to whom the Software is furnished to
+do so, all subject to the following:
+
+The copyright notices in the Software and this entire statement, including
+the above license grant, this restriction and the following disclaimer,
+must be included in all copies of the Software, in whole or in part, and
+all derivative works of the Software, unless such copies or derivative
+works are solely in the form of machine-executable object code generated by
+a source language processor.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.

fpconv/Makefile

@@ -0,0 +1,6 @@
+.PHONY: test fuzz
+test:
+	go test
+
+fuzz:
+	go test -fuzz=Fuzz

fpconv/README.md

@@ -0,0 +1,3 @@
+This is a translation of the actual C code in Redis (7.2) which does the float
+-> string conversion.
+Strconv does a close enough job, but we can use the exact same logic, so why not.

fpconv/dtoa.go

@@ -0,0 +1,286 @@
+package fpconv
+
+import (
+	"math"
+)
+
+var (
+	fracmask  uint64 = 0x000FFFFFFFFFFFFF
+	expmask   uint64 = 0x7FF0000000000000
+	hiddenbit uint64 = 0x0010000000000000
+	signmask  uint64 = 0x8000000000000000
+	expbias   int64  = 1023 + 52
+	zeros            = []rune("0000000000000000000000")
+
+	tens = []uint64{
+		10000000000000000000,
+		1000000000000000000,
+		100000000000000000,
+		10000000000000000,
+		1000000000000000,
+		100000000000000,
+		10000000000000,
+		1000000000000,
+		100000000000,
+		10000000000,
+		1000000000,
+		100000000,
+		10000000,
+		1000000,
+		100000,
+		10000,
+		1000,
+		100,
+		10,
+		1}
+)
+
+func absv(n int) int {
+	if n < 0 {
+		return -n
+	}
+	return n
+}
+
+func minv(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}
+
+func Dtoa(d float64) string {
+	var (
+		dest   [25]rune // Note C has 24, which is broken
+		digits [18]rune
+
+		str_len int = 0
+		neg         = false
+	)
+
+	if get_dbits(d)&signmask != 0 {
+		dest[0] = '-'
+		str_len++
+		neg = true
+	}
+
+	if spec := filter_special(d, dest[str_len:]); spec != 0 {
+		return string(dest[:str_len+spec])
+	}
+
+	var (
+		k       int = 0
+		ndigits int = grisu2(d, &digits, &k)
+	)
+
+	str_len += emit_digits(&digits, ndigits, dest[str_len:], k, neg)
+	return string(dest[:str_len])
+}
+
+func filter_special(fp float64, dest []rune) int {
+	if fp == 0.0 {
+		dest[0] = '0'
+		return 1
+	}
+
+	if math.IsNaN(fp) {
+		dest[0] = 'n'
+		dest[1] = 'a'
+		dest[2] = 'n'
+		return 3
+	}
+	if math.IsInf(fp, 0) {
+		dest[0] = 'i'
+		dest[1] = 'n'
+		dest[2] = 'f'
+		return 3
+	}
+	return 0
+}
+
+func grisu2(d float64, digits *[18]rune, K *int) int {
+	w := build_fp(d)
+
+	lower, upper := get_normalized_boundaries(w)
+
+	w = normalize(w)
+
+	var k int64
+	cp := find_cachedpow10(upper.exp, &k)
+
+	w = multiply(w, cp)
+	upper = multiply(upper, cp)
+	lower = multiply(lower, cp)
+
+	lower.frac++
+	upper.frac--
+
+	*K = int(-k)
+
+	return generate_digits(w, upper, lower, digits[:], K)
+}
+
+func emit_digits(digits *[18]rune, ndigits int, dest []rune, K int, neg bool) int {
+	exp := int(absv(K + ndigits - 1))
+
+	/* write plain integer */
+	if K >= 0 && (exp < (ndigits + 7)) {
+		copy(dest, digits[:ndigits])
+		copy(dest[ndigits:], zeros[:K])
+
+		return ndigits + K
+	}
+
+	/* write decimal w/o scientific notation */
+	if K < 0 && (K > -7 || exp < 4) {
+		offset := int(ndigits - absv(K))
+		/* fp < 1.0 -> write leading zero */
+		if offset <= 0 {
+			offset = -offset
+			dest[0] = '0'
+			dest[1] = '.'
+			copy(dest[2:], zeros[:offset])
+			copy(dest[offset+2:], digits[:ndigits])
+
+			return ndigits + 2 + offset
+
+			/* fp > 1.0 */
+		} else {
+			copy(dest, digits[:offset])
+			dest[offset] = '.'
+			copy(dest[offset+1:], digits[offset:offset+ndigits-offset])
+
+			return ndigits + 1
+		}
+	}
+	/* write decimal w/ scientific notation */
+	l := 18 // was: 18-neg
+	if neg {
+		l--
+	}
+	ndigits = minv(ndigits, l)
+
+	var idx int = 0
+	dest[idx] = digits[0]
+	idx++
+
+	if ndigits > 1 {
+		dest[idx] = '.'
+		idx++
+		copy(dest[idx:], digits[+1:ndigits-1+1])
+		idx += ndigits - 1
+	}
+
+	dest[idx] = 'e'
+	idx++
+
+	sign := '+'
+	if K+ndigits-1 < 0 {
+		sign = '-'
+	}
+	dest[idx] = sign
+	idx++
+
+	var cent rune = 0
+
+	if exp > 99 {
+		cent = rune(exp / 100)
+		dest[idx] = cent + '0'
+		idx++
+		exp -= int(cent) * 100
+	}
+	if exp > 9 {
+		dec := rune(exp / 10)
+		dest[idx] = dec + '0'
+		idx++
+		exp -= int(dec) * 10
+	} else if cent != 0 {
+		dest[idx] = '0'
+		idx++
+	}
+
+	dest[idx] = rune(exp%10) + '0'
+	idx++
+
+	return idx
+}
+
+func generate_digits(fp, upper, lower Fp, digits []rune, K *int) int {
+	var (
+		wfrac = uint64(upper.frac - fp.frac)
+		delta = uint64(upper.frac - lower.frac)
+	)
+
+	one := Fp{
+		frac: 1 << -upper.exp,
+		exp:  upper.exp,
+	}
+
+	part1 := uint64(upper.frac >> -one.exp)
+	part2 := uint64(upper.frac & (one.frac - 1))
+
+	var (
+		idx   = 0
+		kappa = 10
+		index = 10
+	)
+	/* 1000000000 */
+	for ; kappa > 0; index++ {
+		div := tens[index]
+		digit := part1 / div
+
+		if digit != 0 || idx != 0 {
+			digits[idx] = rune(digit) + '0'
+			idx++
+		}
+
+		part1 -= digit * div
+		kappa--
+
+		tmp := (part1 << -one.exp) + part2
+		if tmp <= delta {
+			*K += kappa
+			round_digit(digits, idx, delta, tmp, div<<-one.exp, wfrac)
+
+			return idx
+		}
+	}
+
+	/* 10 */
+	index = 18
+	for {
+		var unit uint64 = tens[index]
+		part2 *= 10
+		delta *= 10
+		kappa--
+
+		digit := part2 >> -one.exp
+		if digit != 0 || idx != 0 {
+			digits[idx] = rune(digit) + '0'
+			idx++
+		}
+
+		part2 &= uint64(one.frac) - 1
+		if part2 < delta {
+			*K += kappa
+			round_digit(digits, idx, delta, part2, uint64(one.frac), wfrac*unit)
+
+			return idx
+		}
+
+		index--
+	}
+}
+
+func round_digit(digits []rune,
+	ndigits int,
+	delta uint64,
+	rem uint64,
+	kappa uint64,
+	frac uint64) {
+	for rem < frac && delta-rem >= kappa &&
+		(rem+kappa < frac || frac-rem > rem+kappa-frac) {
+		digits[ndigits-1]--
+		rem += kappa
+	}
+}