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v/vlib/strconv/atof.c.v

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module strconv
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// Copyright (c) 2019-2023 Dario Deledda. All rights reserved.
// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.
//
// This file contains utilities for converting a string to a f64 variable.
// IEEE 754 standard is used.
// Know limitation: limited to 18 significant digits
//
// The code is inspired by:
// Grzegorz Kraszewski krashan@teleinfo.pb.edu.pl
// URL: http://krashan.ppa.pl/articles/stringtofloat/
// Original license: MIT
// 96 bit operation utilities
//
// Note: when u128 will be available, these function can be refactored.
// f32 constants
pub const (
single_plus_zero = u32(0x0000_0000)
single_minus_zero = u32(0x8000_0000)
single_plus_infinity = u32(0x7F80_0000)
single_minus_infinity = u32(0xFF80_0000)
)
// f64 constants
pub const (
digits = 18
double_plus_zero = u64(0x0000000000000000)
double_minus_zero = u64(0x8000000000000000)
double_plus_infinity = u64(0x7FF0000000000000)
double_minus_infinity = u64(0xFFF0000000000000)
)
// char constants
pub const (
c_dpoint = `.`
c_plus = `+`
c_minus = `-`
c_zero = `0`
c_nine = `9`
c_ten = u32(10)
)
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// right logical shift 96 bit
fn lsr96(s2 u32, s1 u32, s0 u32) (u32, u32, u32) {
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mut r0 := u32(0)
mut r1 := u32(0)
mut r2 := u32(0)
r0 = (s0 >> 1) | ((s1 & u32(1)) << 31)
r1 = (s1 >> 1) | ((s2 & u32(1)) << 31)
r2 = s2 >> 1
return r2, r1, r0
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}
// left logical shift 96 bit
fn lsl96(s2 u32, s1 u32, s0 u32) (u32, u32, u32) {
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mut r0 := u32(0)
mut r1 := u32(0)
mut r2 := u32(0)
r2 = (s2 << 1) | ((s1 & (u32(1) << 31)) >> 31)
r1 = (s1 << 1) | ((s0 & (u32(1) << 31)) >> 31)
r0 = s0 << 1
return r2, r1, r0
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}
// sum on 96 bit
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)
mut r1 := u32(0)
mut r2 := u32(0)
w = u64(s0) + u64(d0)
r0 = u32(w)
w >>= 32
w += u64(s1) + u64(d1)
r1 = u32(w)
w >>= 32
w += u64(s2) + u64(d2)
r2 = u32(w)
return r2, r1, r0
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}
// subtraction on 96 bit
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)
mut r1 := u32(0)
mut r2 := u32(0)
w = u64(s0) - u64(d0)
r0 = u32(w)
w >>= 32
w += u64(s1) - u64(d1)
r1 = u32(w)
w >>= 32
w += u64(s2) - u64(d2)
r2 = u32(w)
return r2, r1, r0
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}
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// Utility functions
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fn is_digit(x u8) bool {
return x >= strconv.c_zero && x <= strconv.c_nine
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}
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fn is_space(x u8) bool {
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 {
return x == `E` || x == `e`
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}
// Possible parser return values.
enum ParserState {
ok // parser finished OK
pzero // no digits or number is smaller than +-2^-1022
mzero // number is negative, module smaller
pinf // number is higher than +HUGE_VAL
minf // number is lower than -HUGE_VAL
invalid_number // invalid number, used for '#@%^' for example
}
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// parser tries to parse the given string into a number
// NOTE: #TOFIX need one char after the last char of the number
[direct_array_access]
fn parser(s string) (ParserState, PrepNumber) {
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mut digx := 0
mut result := ParserState.ok
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mut expneg := false
mut expexp := 0
mut i := 0
mut pn := PrepNumber{}
// skip spaces
for i < s.len && s[i].is_space() {
i++
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}
// check negatives
if s[i] == `-` {
pn.negative = true
i++
}
// positive sign ignore it
if s[i] == `+` {
i++
}
// read mantissa
for i < s.len && s[i].is_digit() {
// println("$i => ${s[i]}")
if digx < strconv.digits {
pn.mantissa *= 10
pn.mantissa += u64(s[i] - strconv.c_zero)
digx++
} else if pn.exponent < 2147483647 {
pn.exponent++
}
i++
}
// read mantissa decimals
if i < s.len && s[i] == `.` {
i++
for i < s.len && s[i].is_digit() {
if digx < strconv.digits {
pn.mantissa *= 10
pn.mantissa += u64(s[i] - strconv.c_zero)
pn.exponent--
digx++
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}
i++
}
}
// read exponent
if i < s.len && (s[i] == `e` || s[i] == `E`) {
i++
if i < s.len {
// esponent sign
if s[i] == strconv.c_plus {
i++
} else if s[i] == strconv.c_minus {
expneg = true
i++
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}
for i < s.len && s[i].is_digit() {
if expexp < 214748364 {
expexp *= 10
expexp += int(s[i] - strconv.c_zero)
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}
i++
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}
}
}
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if expneg {
expexp = -expexp
}
pn.exponent += expexp
if pn.mantissa == 0 {
if pn.negative {
result = .mzero
} else {
result = .pzero
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}
} else if pn.exponent > 309 {
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if pn.negative {
result = .minf
} else {
result = .pinf
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}
} else if pn.exponent < -328 {
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if pn.negative {
result = .mzero
} else {
result = .pzero
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}
}
if i == 0 && s.len > 0 {
return ParserState.invalid_number, pn
}
return result, pn
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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
// s0,s1,s2 are the parts of a 96-bit precision integer
mut s2 := u32(0)
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mut s1 := u32(0)
mut s0 := u32(0)
// q0,q1,q2 are the parts of a 96-bit precision integer
mut q2 := u32(0)
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mut q1 := u32(0)
mut q0 := u32(0)
// r0,r1,r2 are the parts of a 96-bit precision integer
mut r2 := u32(0)
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mut r1 := u32(0)
mut r0 := u32(0)
//
mask28 := u32(u64(0xF) << 28)
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mut result := u64(0)
// working on 3 u32 to have 96 bit precision
s0 = u32(pn.mantissa & u64(0x00000000FFFFFFFF))
s1 = u32(pn.mantissa >> 32)
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s2 = u32(0)
// so we take the decimal exponent off
for pn.exponent > 0 {
q2, q1, q0 = lsl96(s2, s1, s0) // q = s * 2
r2, r1, r0 = lsl96(q2, q1, q0) // r = s * 4 <=> q * 2
s2, s1, s0 = lsl96(r2, r1, r0) // s = s * 8 <=> r * 2
s2, s1, s0 = add96(s2, s1, s0, q2, q1, q0) // s = (s * 8) + (s * 2) <=> s*10
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pn.exponent--
for (s2 & mask28) != 0 {
q2, q1, q0 = lsr96(s2, s1, s0)
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binexp++
s2 = q2
s1 = q1
s0 = q0
}
}
for pn.exponent < 0 {
for !((s2 & (u32(1) << 31)) != 0) {
q2, q1, q0 = lsl96(s2, s1, s0)
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binexp--
s2 = q2
s1 = q1
s0 = q0
}
q2 = s2 / strconv.c_ten
r1 = s2 % strconv.c_ten
r2 = (s1 >> 8) | (r1 << 24)
q1 = r2 / strconv.c_ten
r1 = r2 % strconv.c_ten
r2 = ((s1 & u32(0xFF)) << 16) | (s0 >> 16) | (r1 << 24)
r0 = r2 / strconv.c_ten
r1 = r2 % strconv.c_ten
q1 = (q1 << 8) | ((r0 & u32(0x00FF0000)) >> 16)
q0 = r0 << 16
r2 = (s0 & u32(0xFFFF)) | (r1 << 16)
q0 |= r2 / strconv.c_ten
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s2 = q2
s1 = q1
s0 = q0
pn.exponent++
}
// C.printf(c"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 {
q2, q1, q0 = lsl96(s2, s1, s0)
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binexp--
s2 = q2
s1 = q1
s0 = q0
}
}
// rounding if needed
/*
* "round half to even" algorithm
* Example for f32, just a reminder
*
* If bit 54 is 0, round down
* If bit 54 is 1
* If any bit beyond bit 54 is 1, round up
* If all bits beyond bit 54 are 0 (meaning the number is halfway between two floating-point numbers)
* If bit 53 is 0, round down
* If bit 53 is 1, round up
*/
/*
test case 1 complete
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s2=0x1FFFFFFF
s1=0xFFFFFF80
s0=0x0
*/
/*
test case 1 check_round_bit
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s2=0x18888888
s1=0x88888880
s0=0x0
*/
/*
test case check_round_bit + normalization
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s2=0x18888888
s1=0x88888F80
s0=0x0
*/
// C.printf(c"mantissa before rounding: %08x%08x%08x binexp: %d \n", s2,s1,s0,binexp)
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// s1 => 0xFFFFFFxx only F are rapresented
nbit := 7
check_round_bit := u32(1) << u32(nbit)
check_round_mask := u32(0xFFFFFFFF) << u32(nbit)
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if (s1 & check_round_bit) != 0 {
// C.printf(c"need round!! check mask: %08x\n", s1 & ~check_round_mask )
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if (s1 & ~check_round_mask) != 0 {
// C.printf(c"Add 1!\n")
s2, s1, s0 = add96(s2, s1, s0, 0, check_round_bit, 0)
} else {
// C.printf(c"All 0!\n")
if (s1 & (check_round_bit << u32(1))) != 0 {
// C.printf(c"Add 1 form -1 bit control!\n")
s2, s1, s0 = add96(s2, s1, s0, 0, check_round_bit, 0)
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}
}
s1 = s1 & check_round_mask
s0 = u32(0)
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// recheck normalization
if s2 & (mask28 << u32(1)) != 0 {
// C.printf(c"Renormalize!!\n")
q2, q1, q0 = lsr96(s2, s1, s0)
binexp++
// dump(binexp)
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s2 = q2
s1 = q1
s0 = q0
}
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}
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// tmp := ( u64(s2 & ~mask28) << 24) | ((u64(s1) + u64(128)) >> 8)
// C.printf(c"mantissa after rounding : %08x %08x %08x binexp: %d \n", s2,s1,s0,binexp)
// C.printf(c"Tmp result: %016x\n",tmp)
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// end rounding
// offset the binary exponent IEEE 754
binexp += 1023
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if binexp > 2046 {
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if pn.negative {
result = strconv.double_minus_infinity
} else {
result = strconv.double_plus_infinity
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}
} else if binexp < 1 {
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if pn.negative {
result = strconv.double_minus_zero
} else {
result = strconv.double_plus_zero
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}
} else if s2 != 0 {
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mut q := u64(0)
binexs2 := u64(binexp) << 52
q = (u64(s2 & ~mask28) << 24) | ((u64(s1) + u64(128)) >> 8) | binexs2
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if pn.negative {
q |= (u64(1) << 63)
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}
result = q
}
return result
}
// atof64 parses the string `s`, and if possible, converts it into a f64 number
pub fn atof64(s string) !f64 {
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if s.len == 0 {
return error('expected a number found an empty string')
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}
mut res := Float64u{}
mut res_parsing, mut pn := parser(s)
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match res_parsing {
.ok {
res.u = converter(mut pn)
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}
.pzero {
res.u = strconv.double_plus_zero
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}
.mzero {
res.u = strconv.double_minus_zero
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}
.pinf {
res.u = strconv.double_plus_infinity
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}
.minf {
res.u = strconv.double_minus_infinity
}
.invalid_number {
return error('not a number')
}
}
return unsafe { res.f }
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}