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Diffstat (limited to 'v_windows/v/vlib/strconv/f32_str.v')
| -rw-r--r-- | v_windows/v/vlib/strconv/f32_str.v | 377 |
1 files changed, 377 insertions, 0 deletions
diff --git a/v_windows/v/vlib/strconv/f32_str.v b/v_windows/v/vlib/strconv/f32_str.v new file mode 100644 index 0000000..8e17c89 --- /dev/null +++ b/v_windows/v/vlib/strconv/f32_str.v @@ -0,0 +1,377 @@ +module strconv + +/*============================================================================= + +f32 to string + +Copyright (c) 2019-2021 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 the f32 to string functions + +These functions are based on the work of: +Publication:PLDI 2018: Proceedings of the 39th ACM SIGPLAN +Conference on Programming Language Design and ImplementationJune 2018 +Pages 270–282 https://doi.org/10.1145/3192366.3192369 + +inspired by the Go version here: +https://github.com/cespare/ryu/tree/ba56a33f39e3bbbfa409095d0f9ae168a595feea + +=============================================================================*/ + +// pow of ten table used by n_digit reduction +const ( + ten_pow_table_32 = [ + u32(1), + u32(10), + u32(100), + u32(1000), + u32(10000), + u32(100000), + u32(1000000), + u32(10000000), + u32(100000000), + u32(1000000000), + u32(10000000000), + u32(100000000000), + ] +) + +//============================================================================= +// Conversion Functions +//============================================================================= +const ( + mantbits32 = u32(23) + expbits32 = u32(8) + bias32 = 127 // f32 exponent bias + maxexp32 = 255 +) + +// max 46 char +// -3.40282346638528859811704183484516925440e+38 +[direct_array_access] +pub fn (d Dec32) get_string_32(neg bool, i_n_digit int, i_pad_digit int) string { + n_digit := i_n_digit + 1 + pad_digit := i_pad_digit + 1 + mut out := d.m + // mut out_len := decimal_len_32(out) + mut out_len := dec_digits(out) + out_len_original := out_len + + mut fw_zeros := 0 + if pad_digit > out_len { + fw_zeros = pad_digit - out_len + } + + mut buf := []byte{len: int(out_len + 5 + 1 + 1)} // sign + mant_len + . + e + e_sign + exp_len(2) + \0} + mut i := 0 + + if neg { + if buf.data != 0 { + // The buf.data != 0 check here, is needed for clean compilation + // with `-cc gcc -cstrict -prod`. Without it, gcc produces: + // error: potential null pointer dereference + buf[i] = `-` + } + i++ + } + + mut disp := 0 + if out_len <= 1 { + disp = 1 + } + + if n_digit < out_len { + // println("orig: ${out_len_original}") + out += strconv.ten_pow_table_32[out_len - n_digit - 1] * 5 // round to up + out /= strconv.ten_pow_table_32[out_len - n_digit] + out_len = n_digit + } + + y := i + out_len + mut x := 0 + for x < (out_len - disp - 1) { + buf[y - x] = `0` + byte(out % 10) + out /= 10 + i++ + x++ + } + + // no decimal digits needed, end here + if i_n_digit == 0 { + unsafe { + buf[i] = 0 + return tos(&byte(&buf[0]), i) + } + } + + if out_len >= 1 { + buf[y - x] = `.` + x++ + i++ + } + + if y - x >= 0 { + buf[y - x] = `0` + byte(out % 10) + i++ + } + + for fw_zeros > 0 { + buf[i] = `0` + i++ + fw_zeros-- + } + + buf[i] = `e` + i++ + + mut exp := d.e + out_len_original - 1 + if exp < 0 { + buf[i] = `-` + i++ + exp = -exp + } else { + buf[i] = `+` + i++ + } + + // Always print two digits to match strconv's formatting. + d1 := exp % 10 + d0 := exp / 10 + buf[i] = `0` + byte(d0) + i++ + buf[i] = `0` + byte(d1) + i++ + buf[i] = 0 + + return unsafe { + tos(&byte(&buf[0]), i) + } +} + +fn f32_to_decimal_exact_int(i_mant u32, exp u32) (Dec32, bool) { + mut d := Dec32{} + e := exp - strconv.bias32 + if e > strconv.mantbits32 { + return d, false + } + shift := strconv.mantbits32 - e + mant := i_mant | 0x0080_0000 // implicit 1 + // mant := i_mant | (1 << mantbits32) // implicit 1 + d.m = mant >> shift + if (d.m << shift) != mant { + return d, false + } + for (d.m % 10) == 0 { + d.m /= 10 + d.e++ + } + return d, true +} + +fn f32_to_decimal(mant u32, exp u32) Dec32 { + mut e2 := 0 + mut m2 := u32(0) + if exp == 0 { + // We subtract 2 so that the bounds computation has + // 2 additional bits. + e2 = 1 - strconv.bias32 - int(strconv.mantbits32) - 2 + m2 = mant + } else { + e2 = int(exp) - strconv.bias32 - int(strconv.mantbits32) - 2 + m2 = (u32(1) << strconv.mantbits32) | mant + } + even := (m2 & 1) == 0 + accept_bounds := even + + // Step 2: Determine the interval of valid decimal representations. + mv := u32(4 * m2) + mp := u32(4 * m2 + 2) + mm_shift := bool_to_u32(mant != 0 || exp <= 1) + mm := u32(4 * m2 - 1 - mm_shift) + + mut vr := u32(0) + mut vp := u32(0) + mut vm := u32(0) + mut e10 := 0 + mut vm_is_trailing_zeros := false + mut vr_is_trailing_zeros := false + mut last_removed_digit := byte(0) + + if e2 >= 0 { + q := log10_pow2(e2) + e10 = int(q) + k := pow5_inv_num_bits_32 + pow5_bits(int(q)) - 1 + i := -e2 + int(q) + k + + vr = mul_pow5_invdiv_pow2(mv, q, i) + vp = mul_pow5_invdiv_pow2(mp, q, i) + vm = mul_pow5_invdiv_pow2(mm, q, i) + if q != 0 && (vp - 1) / 10 <= vm / 10 { + // We need to know one removed digit even if we are not + // going to loop below. We could use q = X - 1 above, + // except that would require 33 bits for the result, and + // we've found that 32-bit arithmetic is faster even on + // 64-bit machines. + l := pow5_inv_num_bits_32 + pow5_bits(int(q - 1)) - 1 + last_removed_digit = byte(mul_pow5_invdiv_pow2(mv, q - 1, -e2 + int(q - 1) + l) % 10) + } + if q <= 9 { + // The largest power of 5 that fits in 24 bits is 5^10, + // but q <= 9 seems to be safe as well. Only one of mp, + // mv, and mm can be a multiple of 5, if any. + if mv % 5 == 0 { + vr_is_trailing_zeros = multiple_of_power_of_five_32(mv, q) + } else if accept_bounds { + vm_is_trailing_zeros = multiple_of_power_of_five_32(mm, q) + } else if multiple_of_power_of_five_32(mp, q) { + vp-- + } + } + } else { + q := log10_pow5(-e2) + e10 = int(q) + e2 + i := -e2 - int(q) + k := pow5_bits(i) - pow5_num_bits_32 + mut j := int(q) - k + vr = mul_pow5_div_pow2(mv, u32(i), j) + vp = mul_pow5_div_pow2(mp, u32(i), j) + vm = mul_pow5_div_pow2(mm, u32(i), j) + if q != 0 && ((vp - 1) / 10) <= vm / 10 { + j = int(q) - 1 - (pow5_bits(i + 1) - pow5_num_bits_32) + last_removed_digit = byte(mul_pow5_div_pow2(mv, u32(i + 1), j) % 10) + } + if q <= 1 { + // {vr,vp,vm} is trailing zeros if {mv,mp,mm} has at + // least q trailing 0 bits. mv = 4 * m2, so it always + // has at least two trailing 0 bits. + vr_is_trailing_zeros = true + if accept_bounds { + // mm = mv - 1 - mm_shift, so it has 1 trailing 0 bit + // if mm_shift == 1. + vm_is_trailing_zeros = mm_shift == 1 + } else { + // mp = mv + 2, so it always has at least one + // trailing 0 bit. + vp-- + } + } else if q < 31 { + vr_is_trailing_zeros = multiple_of_power_of_two_32(mv, q - 1) + } + } + + // Step 4: Find the shortest decimal representation + // in the interval of valid representations. + mut removed := 0 + mut out := u32(0) + if vm_is_trailing_zeros || vr_is_trailing_zeros { + // General case, which happens rarely (~4.0%). + for vp / 10 > vm / 10 { + vm_is_trailing_zeros = vm_is_trailing_zeros && (vm % 10) == 0 + vr_is_trailing_zeros = vr_is_trailing_zeros && (last_removed_digit == 0) + last_removed_digit = byte(vr % 10) + vr /= 10 + vp /= 10 + vm /= 10 + removed++ + } + if vm_is_trailing_zeros { + for vm % 10 == 0 { + vr_is_trailing_zeros = vr_is_trailing_zeros && (last_removed_digit == 0) + last_removed_digit = byte(vr % 10) + vr /= 10 + vp /= 10 + vm /= 10 + removed++ + } + } + if vr_is_trailing_zeros && (last_removed_digit == 5) && (vr % 2) == 0 { + // Round even if the exact number is .....50..0. + last_removed_digit = 4 + } + out = vr + // We need to take vr + 1 if vr is outside bounds + // or we need to round up. + if (vr == vm && (!accept_bounds || !vm_is_trailing_zeros)) || last_removed_digit >= 5 { + out++ + } + } else { + // Specialized for the common case (~96.0%). Percentages below + // are relative to this. Loop iterations below (approximately): + // 0: 13.6%, 1: 70.7%, 2: 14.1%, 3: 1.39%, 4: 0.14%, 5+: 0.01% + for vp / 10 > vm / 10 { + last_removed_digit = byte(vr % 10) + vr /= 10 + vp /= 10 + vm /= 10 + removed++ + } + // We need to take vr + 1 if vr is outside bounds + // or we need to round up. + out = vr + bool_to_u32(vr == vm || last_removed_digit >= 5) + } + + return Dec32{ + m: out + e: e10 + removed + } +} + +//============================================================================= +// String Functions +//============================================================================= + +// f32_to_str return a string in scientific notation with max n_digit after the dot +pub fn f32_to_str(f f32, n_digit int) string { + mut u1 := Uf32{} + u1.f = f + u := unsafe { u1.u } + + neg := (u >> (strconv.mantbits32 + strconv.expbits32)) != 0 + mant := u & ((u32(1) << strconv.mantbits32) - u32(1)) + exp := (u >> strconv.mantbits32) & ((u32(1) << strconv.expbits32) - u32(1)) + + // println("${neg} ${mant} e ${exp-bias32}") + + // Exit early for easy cases. + if (exp == strconv.maxexp32) || (exp == 0 && mant == 0) { + return get_string_special(neg, exp == 0, mant == 0) + } + + mut d, ok := f32_to_decimal_exact_int(mant, exp) + if !ok { + // println("with exp form") + d = f32_to_decimal(mant, exp) + } + + // println("${d.m} ${d.e}") + return d.get_string_32(neg, n_digit, 0) +} + +// f32_to_str return a string in scientific notation with max n_digit after the dot +pub fn f32_to_str_pad(f f32, n_digit int) string { + mut u1 := Uf32{} + u1.f = f + u := unsafe { u1.u } + + neg := (u >> (strconv.mantbits32 + strconv.expbits32)) != 0 + mant := u & ((u32(1) << strconv.mantbits32) - u32(1)) + exp := (u >> strconv.mantbits32) & ((u32(1) << strconv.expbits32) - u32(1)) + + // println("${neg} ${mant} e ${exp-bias32}") + + // Exit early for easy cases. + if (exp == strconv.maxexp32) || (exp == 0 && mant == 0) { + return get_string_special(neg, exp == 0, mant == 0) + } + + mut d, ok := f32_to_decimal_exact_int(mant, exp) + if !ok { + // println("with exp form") + d = f32_to_decimal(mant, exp) + } + + // println("${d.m} ${d.e}") + return d.get_string_32(neg, n_digit, n_digit) +} |