423 lines
9.4 KiB
V
423 lines
9.4 KiB
V
module strconv
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// Copyright (c) 2019-2022 Dario Deledda. All rights reserved.
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// Use of this source code is governed by an MIT license
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// that can be found in the LICENSE file.
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//
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// This file contains utilities for converting a string to a f64 variable.
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// IEEE 754 standard is used.
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// Know limitation: limited to 18 significant digits
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//
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// The code is inspired by:
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// Grzegorz Kraszewski krashan@teleinfo.pb.edu.pl
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// URL: http://krashan.ppa.pl/articles/stringtofloat/
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// Original license: MIT
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// 96 bit operation utilities
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//
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// Note: when u128 will be available, these function can be refactored.
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// f32 constants
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pub const (
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single_plus_zero = u32(0x0000_0000)
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single_minus_zero = u32(0x8000_0000)
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single_plus_infinity = u32(0x7F80_0000)
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single_minus_infinity = u32(0xFF80_0000)
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)
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// f64 constants
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pub const (
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digits = 18
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double_plus_zero = u64(0x0000000000000000)
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double_minus_zero = u64(0x8000000000000000)
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double_plus_infinity = u64(0x7FF0000000000000)
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double_minus_infinity = u64(0xFFF0000000000000)
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)
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// char constants
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pub const (
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c_dpoint = `.`
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c_plus = `+`
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c_minus = `-`
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c_zero = `0`
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c_nine = `9`
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c_ten = u32(10)
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)
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// right logical shift 96 bit
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fn lsr96(s2 u32, s1 u32, s0 u32) (u32, u32, u32) {
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mut r0 := u32(0)
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mut r1 := u32(0)
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mut r2 := u32(0)
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r0 = (s0 >> 1) | ((s1 & u32(1)) << 31)
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r1 = (s1 >> 1) | ((s2 & u32(1)) << 31)
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r2 = s2 >> 1
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return r2, r1, r0
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}
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// left logical shift 96 bit
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fn lsl96(s2 u32, s1 u32, s0 u32) (u32, u32, u32) {
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mut r0 := u32(0)
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mut r1 := u32(0)
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mut r2 := u32(0)
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r2 = (s2 << 1) | ((s1 & (u32(1) << 31)) >> 31)
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r1 = (s1 << 1) | ((s0 & (u32(1) << 31)) >> 31)
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r0 = s0 << 1
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return r2, r1, r0
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}
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// sum on 96 bit
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fn add96(s2 u32, s1 u32, s0 u32, d2 u32, d1 u32, d0 u32) (u32, u32, u32) {
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mut w := u64(0)
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mut r0 := u32(0)
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mut r1 := u32(0)
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mut r2 := u32(0)
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w = u64(s0) + u64(d0)
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r0 = u32(w)
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w >>= 32
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w += u64(s1) + u64(d1)
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r1 = u32(w)
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w >>= 32
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w += u64(s2) + u64(d2)
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r2 = u32(w)
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return r2, r1, r0
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}
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// subtraction on 96 bit
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fn sub96(s2 u32, s1 u32, s0 u32, d2 u32, d1 u32, d0 u32) (u32, u32, u32) {
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mut w := u64(0)
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mut r0 := u32(0)
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mut r1 := u32(0)
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mut r2 := u32(0)
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w = u64(s0) - u64(d0)
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r0 = u32(w)
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w >>= 32
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w += u64(s1) - u64(d1)
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r1 = u32(w)
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w >>= 32
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w += u64(s2) - u64(d2)
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r2 = u32(w)
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return r2, r1, r0
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}
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// Utility functions
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fn is_digit(x u8) bool {
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return (x >= strconv.c_zero && x <= strconv.c_nine) == true
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}
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fn is_space(x u8) bool {
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return x == `\t` || x == `\n` || x == `\v` || x == `\f` || x == `\r` || x == ` `
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}
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fn is_exp(x u8) bool {
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return (x == `E` || x == `e`) == true
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}
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// Possible parser return values.
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enum ParserState {
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ok // parser finished OK
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pzero // no digits or number is smaller than +-2^-1022
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mzero // number is negative, module smaller
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pinf // number is higher than +HUGE_VAL
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minf // number is lower than -HUGE_VAL
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invalid_number // invalid number, used for '#@%^' for example
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}
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// parser tries to parse the given string into a number
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// NOTE: #TOFIX need one char after the last char of the number
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fn parser(s string) (ParserState, PrepNumber) {
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mut digx := 0
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mut result := ParserState.ok
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mut expneg := false
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mut expexp := 0
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mut i := 0
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mut pn := PrepNumber{}
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// skip spaces
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for i < s.len && s[i].is_space() {
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i++
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}
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// check negatives
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if s[i] == `-` {
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pn.negative = true
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i++
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}
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// positive sign ignore it
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if s[i] == `+` {
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i++
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}
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// read mantissa
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for i < s.len && s[i].is_digit() {
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// println("$i => ${s[i]}")
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if digx < strconv.digits {
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pn.mantissa *= 10
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pn.mantissa += u64(s[i] - strconv.c_zero)
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digx++
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} else if pn.exponent < 2147483647 {
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pn.exponent++
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}
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i++
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}
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// read mantissa decimals
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if (i < s.len) && (s[i] == `.`) {
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i++
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for i < s.len && s[i].is_digit() {
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if digx < strconv.digits {
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pn.mantissa *= 10
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pn.mantissa += u64(s[i] - strconv.c_zero)
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pn.exponent--
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digx++
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}
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i++
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}
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}
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// read exponent
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if (i < s.len) && ((s[i] == `e`) || (s[i] == `E`)) {
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i++
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if i < s.len {
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// esponent sign
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if s[i] == strconv.c_plus {
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i++
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} else if s[i] == strconv.c_minus {
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expneg = true
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i++
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}
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for i < s.len && s[i].is_digit() {
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if expexp < 214748364 {
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expexp *= 10
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expexp += int(s[i] - strconv.c_zero)
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}
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i++
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}
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}
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}
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if expneg {
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expexp = -expexp
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}
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pn.exponent += expexp
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if pn.mantissa == 0 {
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if pn.negative {
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result = .mzero
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} else {
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result = .pzero
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}
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} else if pn.exponent > 309 {
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if pn.negative {
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result = .minf
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} else {
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result = .pinf
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}
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} else if pn.exponent < -328 {
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if pn.negative {
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result = .mzero
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} else {
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result = .pzero
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}
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}
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if i == 0 && s.len > 0 {
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return ParserState.invalid_number, pn
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}
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return result, pn
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}
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// converter returns a u64 with the bit image of the f64 number
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fn converter(mut pn PrepNumber) u64 {
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mut binexp := 92
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// s0,s1,s2 are the parts of a 96-bit precision integer
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mut s2 := u32(0)
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mut s1 := u32(0)
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mut s0 := u32(0)
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// q0,q1,q2 are the parts of a 96-bit precision integer
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mut q2 := u32(0)
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mut q1 := u32(0)
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mut q0 := u32(0)
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// r0,r1,r2 are the parts of a 96-bit precision integer
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mut r2 := u32(0)
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mut r1 := u32(0)
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mut r0 := u32(0)
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//
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mask28 := u32(u64(0xF) << 28)
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mut result := u64(0)
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// working on 3 u32 to have 96 bit precision
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s0 = u32(pn.mantissa & u64(0x00000000FFFFFFFF))
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s1 = u32(pn.mantissa >> 32)
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s2 = u32(0)
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// so we take the decimal exponent off
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for pn.exponent > 0 {
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q2, q1, q0 = lsl96(s2, s1, s0) // q = s * 2
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r2, r1, r0 = lsl96(q2, q1, q0) // r = s * 4 <=> q * 2
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s2, s1, s0 = lsl96(r2, r1, r0) // s = s * 8 <=> r * 2
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s2, s1, s0 = add96(s2, s1, s0, q2, q1, q0) // s = (s * 8) + (s * 2) <=> s*10
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pn.exponent--
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for (s2 & mask28) != 0 {
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q2, q1, q0 = lsr96(s2, s1, s0)
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binexp++
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s2 = q2
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s1 = q1
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s0 = q0
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}
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}
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for pn.exponent < 0 {
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for !((s2 & (u32(1) << 31)) != 0) {
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q2, q1, q0 = lsl96(s2, s1, s0)
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binexp--
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s2 = q2
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s1 = q1
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s0 = q0
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}
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q2 = s2 / strconv.c_ten
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r1 = s2 % strconv.c_ten
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r2 = (s1 >> 8) | (r1 << 24)
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q1 = r2 / strconv.c_ten
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r1 = r2 % strconv.c_ten
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r2 = ((s1 & u32(0xFF)) << 16) | (s0 >> 16) | (r1 << 24)
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r0 = r2 / strconv.c_ten
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r1 = r2 % strconv.c_ten
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q1 = (q1 << 8) | ((r0 & u32(0x00FF0000)) >> 16)
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q0 = r0 << 16
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r2 = (s0 & u32(0xFFFF)) | (r1 << 16)
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q0 |= r2 / strconv.c_ten
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s2 = q2
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s1 = q1
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s0 = q0
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pn.exponent++
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}
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// C.printf("mantissa before normalization: %08x%08x%08x binexp: %d \n", s2,s1,s0,binexp)
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// normalization, the 28 bit in s2 must the leftest one in the variable
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if s2 != 0 || s1 != 0 || s0 != 0 {
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for (s2 & mask28) == 0 {
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q2, q1, q0 = lsl96(s2, s1, s0)
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binexp--
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s2 = q2
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s1 = q1
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s0 = q0
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}
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}
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// rounding if needed
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/*
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* "round half to even" algorithm
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* Example for f32, just a reminder
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*
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* If bit 54 is 0, round down
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* If bit 54 is 1
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* If any bit beyond bit 54 is 1, round up
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* If all bits beyond bit 54 are 0 (meaning the number is halfway between two floating-point numbers)
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* If bit 53 is 0, round down
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* If bit 53 is 1, round up
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*/
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/*
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test case 1 complete
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s2=0x1FFFFFFF
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s1=0xFFFFFF80
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s0=0x0
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*/
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/*
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test case 1 check_round_bit
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s2=0x18888888
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s1=0x88888880
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s0=0x0
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*/
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/*
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test case check_round_bit + normalization
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s2=0x18888888
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s1=0x88888F80
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s0=0x0
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*/
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// C.printf("mantissa before rounding: %08x%08x%08x binexp: %d \n", s2,s1,s0,binexp)
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// s1 => 0xFFFFFFxx only F are rapresented
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nbit := 7
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check_round_bit := u32(1) << u32(nbit)
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check_round_mask := u32(0xFFFFFFFF) << u32(nbit)
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if (s1 & check_round_bit) != 0 {
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// C.printf("need round!! cehck mask: %08x\n", s1 & ~check_round_mask )
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if (s1 & ~check_round_mask) != 0 {
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// C.printf("Add 1!\n")
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s2, s1, s0 = add96(s2, s1, s0, 0, check_round_bit, 0)
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} else {
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// C.printf("All 0!\n")
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if (s1 & (check_round_bit << u32(1))) != 0 {
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// C.printf("Add 1 form -1 bit control!\n")
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s2, s1, s0 = add96(s2, s1, s0, 0, check_round_bit, 0)
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}
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}
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s1 = s1 & check_round_mask
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s0 = u32(0)
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// recheck normalization
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if s2 & (mask28 << u32(1)) != 0 {
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// C.printf("Renormalize!!")
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q2, q1, q0 = lsr96(s2, s1, s0)
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binexp--
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s2 = q2
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s1 = q1
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s0 = q0
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}
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}
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// tmp := ( u64(s2 & ~mask28) << 24) | ((u64(s1) + u64(128)) >> 8)
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// C.printf("mantissa after rounding : %08x%08x%08x binexp: %d \n", s2,s1,s0,binexp)
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// C.printf("Tmp result: %016x\n",tmp)
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// end rounding
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// offset the binary exponent IEEE 754
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binexp += 1023
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if binexp > 2046 {
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if pn.negative {
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result = strconv.double_minus_infinity
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} else {
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result = strconv.double_plus_infinity
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}
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} else if binexp < 1 {
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if pn.negative {
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result = strconv.double_minus_zero
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} else {
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result = strconv.double_plus_zero
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}
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} else if s2 != 0 {
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mut q := u64(0)
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binexs2 := u64(binexp) << 52
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q = (u64(s2 & ~mask28) << 24) | ((u64(s1) + u64(128)) >> 8) | binexs2
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if pn.negative {
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q |= (u64(1) << 63)
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}
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result = q
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}
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return result
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}
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// atof64 parses the string `s`, and if possible, converts it into a f64 number
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pub fn atof64(s string) ?f64 {
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if s.len == 0 {
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return error('expected a number found an empty string')
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}
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mut res := Float64u{}
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mut res_parsing, mut pn := parser(s)
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match res_parsing {
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.ok {
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res.u = converter(mut pn)
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}
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.pzero {
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res.u = strconv.double_plus_zero
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}
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.mzero {
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res.u = strconv.double_minus_zero
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}
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.pinf {
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res.u = strconv.double_plus_infinity
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}
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.minf {
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res.u = strconv.double_minus_infinity
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}
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.invalid_number {
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return error('not a number')
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}
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}
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return unsafe { res.f }
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}
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