340 lines
7.5 KiB
V
340 lines
7.5 KiB
V
/**********************************************************************
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*
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* f32/f64 to string utilities
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*
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* Copyright (c) 2019-2020 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 the f32/f64 to string utilities functions
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*
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* These functions are based on the work of:
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* Publication:PLDI 2018: Proceedings of the 39th ACM SIGPLAN
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* Conference on Programming Language Design and ImplementationJune 2018
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* Pages 270–282 https://doi.org/10.1145/3192366.3192369
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*
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* inspired by the Go version here:
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* https://github.com/cespare/ryu/tree/ba56a33f39e3bbbfa409095d0f9ae168a595feea
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*
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**********************************************************************/
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module ftoa
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import math.bits
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//import math
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/******************************************************************************
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*
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* General Utilities
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*
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******************************************************************************/
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fn assert1(t bool, msg string) {
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if !t {
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panic(msg)
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}
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}
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[inline]
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fn bool_to_int(b bool) int {
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if b {
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return 1
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}
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return 0
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}
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[inline]
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fn bool_to_u32(b bool) u32 {
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if b {
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return u32(1)
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}
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return u32(0)
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}
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[inline]
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fn bool_to_u64(b bool) u64 {
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if b {
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return u64(1)
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}
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return u64(0)
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}
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fn get_string_special(neg bool, expZero bool, mantZero bool) string {
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if !mantZero {
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return "nan"
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}
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if !expZero {
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if neg {
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return "-inf"
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} else {
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return "+inf"
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}
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}
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if neg {
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return "-0e+00"
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}
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return "0e+00"
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}
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/******************************************************************************
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*
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* 32 bit functions
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*
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******************************************************************************/
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fn decimal_len_32(u u32) int {
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// Function precondition: u is not a 10-digit number.
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// (9 digits are sufficient for round-tripping.)
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// This benchmarked faster than the log2 approach used for u64.
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assert1(u < 1000000000, "too big")
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if u >= 100000000 { return 9 }
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else if u >= 10000000 { return 8 }
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else if u >= 1000000 { return 7 }
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else if u >= 100000 { return 6 }
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else if u >= 10000 { return 5 }
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else if u >= 1000 { return 4 }
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else if u >= 100 { return 3 }
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else if u >= 10 { return 2 }
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return 1
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}
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fn mul_shift_32(m u32, mul u64, ishift int) u32 {
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// QTODO
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//assert ishift > 32
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hi, lo := bits.mul_64(u64(m), mul)
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shifted_sum := (lo >> u64(ishift)) + (hi << u64(64-ishift))
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assert1(shifted_sum <= 2147483647, "shiftedSum <= math.max_u32")
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return u32(shifted_sum)
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}
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fn mul_pow5_invdiv_pow2(m u32, q u32, j int) u32 {
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return mul_shift_32(m, pow5_inv_split_32[q], j)
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}
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fn mul_pow5_div_pow2(m u32, i u32, j int) u32 {
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return mul_shift_32(m, pow5_split_32[i], j)
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}
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fn pow5_factor_32(i_v u32) u32 {
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mut v := i_v
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for n := u32(0); ; n++ {
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q := v/5
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r := v%5
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if r != 0 {
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return n
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}
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v = q
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}
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return v
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}
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// multiple_of_power_of_five_32 reports whether v is divisible by 5^p.
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fn multiple_of_power_of_five_32(v u32, p u32) bool {
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return pow5_factor_32(v) >= p
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}
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// multiple_of_power_of_two_32 reports whether v is divisible by 2^p.
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fn multiple_of_power_of_two_32(v u32, p u32) bool {
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return u32(bits.trailing_zeros_32(v)) >= p
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}
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// log10_pow2 returns floor(log_10(2^e)).
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fn log10_pow2(e int) u32 {
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// The first value this approximation fails for is 2^1651
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// which is just greater than 10^297.
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assert1(e >= 0, "e >= 0")
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assert1(e <= 1650, "e <= 1650")
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return (u32(e) * 78913) >> 18
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}
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// log10_pow5 returns floor(log_10(5^e)).
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fn log10_pow5(e int) u32 {
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// The first value this approximation fails for is 5^2621
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// which is just greater than 10^1832.
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assert1(e >= 0, "e >= 0")
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assert1(e <= 2620, "e <= 2620")
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return (u32(e) * 732923) >> 20
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}
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// pow5_bits returns ceil(log_2(5^e)), or else 1 if e==0.
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fn pow5_bits(e int) int {
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// This approximation works up to the point that the multiplication
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// overflows at e = 3529. If the multiplication were done in 64 bits,
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// it would fail at 5^4004 which is just greater than 2^9297.
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assert1(e >= 0, "e >= 0")
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assert1(e <= 3528, "e <= 3528")
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return int( ((u32(e)*1217359)>>19) + 1)
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}
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/******************************************************************************
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*
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* 64 bit functions
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*
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******************************************************************************/
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fn decimal_len_64(u u64) int {
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// http://graphics.stanford.edu/~seander/bithacks.html#IntegerLog10
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log2 := 64 - bits.leading_zeros_64(u) - 1
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t := (log2 + 1) * 1233 >> 12
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return t - bool_to_int(u < powers_of_10[t]) + 1
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}
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fn shift_right_128(v Uint128, shift int) u64 {
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// The shift value is always modulo 64.
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// In the current implementation of the 64-bit version
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// of Ryu, the shift value is always < 64.
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// (It is in the range [2, 59].)
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// Check this here in case a future change requires larger shift
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// values. In this case this function needs to be adjusted.
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assert1(shift < 64, "shift < 64")
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return (v.hi << u64(64 - shift)) | (v.lo >> u32(shift))
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}
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fn mul_shift_64(m u64, mul Uint128, shift int) u64 {
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hihi, hilo := bits.mul_64(m, mul.hi)
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lohi, _ := bits.mul_64(m, mul.lo)
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mut sum := Uint128{lo: lohi + hilo,hi: hihi}
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if sum.lo < lohi {
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sum.hi++ // overflow
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}
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return shift_right_128(sum, shift-64)
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}
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fn pow5_factor_64(v_i u64) u32 {
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mut v := v_i
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for n := u32(0); ; n++ {
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q := v/5
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r := v%5
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if r != 0 {
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return n
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}
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v = q
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}
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return u32(0)
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}
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fn multiple_of_power_of_five_64(v u64, p u32) bool {
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return pow5_factor_64(v) >= p
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}
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fn multiple_of_power_of_two_64(v u64, p u32) bool {
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return u32(bits.trailing_zeros_64(v)) >= p
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}
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/******************************************************************************
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*
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* f64 to string with string format
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*
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******************************************************************************/
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// f32_to_str_l return a string with the f32 converted in a strign in decimal notation
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pub fn f32_to_str_l(f f64) string {
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return f64_to_str_l(f32(f))
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}
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// f64_to_str_l return a string with the f64 converted in a strign in decimal notation
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pub fn f64_to_str_l(f f64) string {
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s := f64_to_str(f,18)
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// check for +inf -inf Nan
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if s.len > 2 && (s[0] == `n` || s[1] == `i`) {
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return s
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}
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m_sgn_flag := false
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mut sgn := 1
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mut b := [26]byte
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mut d_pos := 1
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mut i := 0
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mut i1 := 0
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mut exp := 0
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mut exp_sgn := 1
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// get sign and deciaml parts
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for c in s {
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if c == `-` {
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sgn = -1
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i++
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} else if c == `+` {
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sgn = 1
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i++
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}
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else if c >= `0` && c <= `9` {
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b[i1++] = c
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i++
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} else if c == `.` {
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if sgn > 0 {
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d_pos = i
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} else {
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d_pos = i-1
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}
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i++
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} else if c == `e` {
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i++
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break
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} else {
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return "Float conversion error!!"
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}
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}
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b[i1] = 0
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// get exponent
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if s[i] == `-` {
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exp_sgn = -1
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i++
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} else if s[i] == `+` {
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exp_sgn = 1
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i++
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}
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for c in s[i..] {
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exp = exp * 10 + int(c-`0`)
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}
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// allocate exp+32 chars for the return string
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mut res := [`0`].repeat(exp+32) // TODO: Slow!! is there other possibilities to allocate this?
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mut r_i := 0 // result string buffer index
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//println("s:${sgn} b:${b[0]} es:${exp_sgn} exp:${exp}")
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if sgn == 1 {
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if m_sgn_flag {
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res[r_i++] = `+`
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}
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} else {
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res[r_i++] = `-`
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}
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i = 0
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if exp_sgn >= 0 {
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for b[i] != 0 {
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res[r_i++] = b[i]
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i++
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if i >= d_pos && exp >= 0 {
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if exp == 0 {
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res[r_i++] = `.`
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}
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exp--
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}
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}
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for exp >= 0 {
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res[r_i++] = `0`
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exp--
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}
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} else {
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mut dot_p := true
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for exp > 0 {
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res[r_i++] = `0`
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exp--
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if dot_p {
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res[r_i++] = `.`
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dot_p = false
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}
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}
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for b[i] != 0 {
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res[r_i++] = b[i]
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i++
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}
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}
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res[r_i] = 0
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return tos(&res[0],r_i)
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}
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