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