module strconv /* atof util Copyright (c) 2019 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 convert a string in 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 */ // right logical shift 96 bit fn lsr96(s2 u32, s1 u32, s0 u32) (u32,u32,u32) { 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 } // left logical shift 96 bit fn lsl96(s2 u32, s1 u32, s0 u32) (u32,u32,u32) { 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 } // sum on 96 bit fn add96(s2 u32, s1 u32, s0 u32, d2 u32, d1 u32, d0 u32) (u32,u32,u32) { mut w := u64(0) 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 } // subtraction on 96 bit fn sub96(s2 u32, s1 u32, s0 u32, d2 u32, d1 u32, d0 u32) (u32,u32,u32) { mut w := u64(0) 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 } /* Constants */ const ( // // f64 constants // digits = 18 double_plus_zero = u64(0x0000000000000000) double_minus_zero = u64(0x8000000000000000) double_plus_infinity = u64(0x7FF0000000000000) double_minus_infinity = u64(0xFFF0000000000000) // // parser state machine states // fsm_a = 0 fsm_b = 1 fsm_c = 2 fsm_d = 3 fsm_e = 4 fsm_f = 5 fsm_g = 6 fsm_h = 7 fsm_i = 8 fsm_stop = 9 // // Possible parser return values. // parser_ok = 0 // parser finished OK parser_pzero = 1 // no digits or number is smaller than +-2^-1022 parser_mzero = 2 // number is negative, module smaller parser_pinf = 3 // number is higher than +HUGE_VAL parser_minf = 4 // number is lower than -HUGE_VAL // // char constants // Note: Modify these if working with non-ASCII encoding // c_dpoint = `.` c_plus = `+` c_minus = `-` c_zero = `0` c_nine = `9` c_ten = u32(10) ) /* Utility */ // NOTE: Modify these if working with non-ASCII encoding fn is_digit(x byte) bool { return (x >= c_zero && x <= c_nine) == true } fn is_space(x byte) bool { return (x == `\t` || x == `\n` || x == `\v` || x == `\f` || x == `\r` || x == ` `) } fn is_exp(x byte) bool { return (x == `E` || x == `e`) == true } /* Support struct */ /* String parser NOTE: #TOFIX need one char after the last char of the number */ // parser return a support struct with all the parsing information for the converter fn parser(s string) (int,PrepNumber) { mut state := fsm_a mut digx := 0 mut c := byte(` `) // initial value for kicking off the state machine mut result := parser_ok mut expneg := false mut expexp := 0 mut i := 0 mut pn := PrepNumber{ } for state != fsm_stop { match state { // skip starting spaces fsm_a { if is_space(c) == true { c = s[i] i++ } else { state = fsm_b } } // check for the sign or point fsm_b { state = fsm_c if c == c_plus { c = s[i] i++ } else if c == c_minus { pn.negative = true c = s[i] i++ } else if is_digit(c) { } else if c == c_dpoint { } else { state = fsm_stop } } // skip the inital zeros fsm_c { if c == c_zero { c = s[i++] } else if c == c_dpoint { c = s[i++] state = fsm_d } else { state = fsm_e } } // reading leading zeros in the fractional part of mantissa fsm_d { if c == c_zero { c = s[i++] if pn.exponent > -2147483647 { pn.exponent-- } } else { state = fsm_f } } // reading integer part of mantissa fsm_e { if is_digit(c) { if digx < digits { pn.mantissa *= 10 pn.mantissa += u64(c - c_zero) digx++ } else if pn.exponent < 2147483647 { pn.exponent++ } c = s[i++] } else if c == c_dpoint { c = s[i++] state = fsm_f } else { state = fsm_f } } // reading fractional part of mantissa fsm_f { if is_digit(c) { if digx < digits { pn.mantissa *= 10 pn.mantissa += u64(c - c_zero) pn.exponent-- digx++ } c = s[i++] } else if is_exp(c) { c = s[i++] state = fsm_g } else { state = fsm_g } } // reading sign of exponent fsm_g { if c == c_plus { c = s[i++] } else if c == c_minus { expneg = true c = s[i++] } state = fsm_h } // skipping leading zeros of exponent fsm_h { if c == c_zero { c = s[i++] } else { state = fsm_i } } // reading exponent digits fsm_i { if is_digit(c) { if expexp < 214748364 { expexp *= 10 expexp += int(c - c_zero) } c = s[i++] } else { state = fsm_stop } } else { }} // C.printf("len: %d i: %d str: %s \n",s.len,i,s[..i]) if i >= s.len { state = fsm_stop } } if expneg { expexp = -expexp } pn.exponent += expexp if pn.mantissa == 0 { if pn.negative { result = parser_mzero } else { result = parser_pzero } } else if pn.exponent > 309 { if pn.negative { result = parser_minf } else { result = parser_pinf } } else if pn.exponent < -328 { if pn.negative { result = parser_mzero } else { result = parser_pzero } } return result,pn } /* Converter to the bit form of the f64 number */ // converter return a u64 with the bit image of the f64 number fn converter(mut pn PrepNumber) u64 { mut binexp := 92 mut s2 := u32(0) // 96-bit precision integer mut s1 := u32(0) mut s0 := u32(0) mut q2 := u32(0) // 96-bit precision integer mut q1 := u32(0) mut q0 := u32(0) mut r2 := u32(0) // 96-bit precision integer mut r1 := u32(0) mut r0 := u32(0) mask28 := u32(0xF<<28) mut result := u64(0) // working on 3 u32 to have 96 bit precision s0 = u32(pn.mantissa & u64(0x00000000FFFFFFFF)) s1 = u32(pn.mantissa>>32) 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 pn.exponent-- for (s2 & mask28) != 0 { q2,q1,q0 = lsr96(s2, s1, s0) binexp++ s2 = q2 s1 = q1 s0 = q0 } } for pn.exponent < 0 { for !((s2 & (u32(1)<<31)) != 0) { q2,q1,q0 = lsl96(s2, s1, s0) binexp-- s2 = q2 s1 = q1 s0 = q0 } q2 = s2 / c_ten r1 = s2 % c_ten r2 = (s1>>8) | (r1<<24) q1 = r2 / c_ten r1 = r2 % c_ten r2 = ((s1 & u32(0xFF))<<16) | (s0>>16) | (r1<<24) r0 = r2 / c_ten r1 = r2 % c_ten q1 = (q1<<8) | ((r0 & u32(0x00FF0000))>>16) q0 = r0<<16 r2 = (s0 & u32(0xFFFF)) | (r1<<16) q0 |= r2 / c_ten s2 = q2 s1 = q1 s0 = q0 pn.exponent++ } // C.printf("mantissa before normalization: %08x%08x%08x binexp: %d \n", s2,s1,s0,binexp) // normalization, the 28 bit in s2 must the leftest one in the variable if s2 != 0 || s1 != 0 || s0 != 0 { for (s2 & mask28) == 0 { q2,q1,q0 = lsl96(s2, s1, s0) 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 s2=0x1FFFFFFF s1=0xFFFFFF80 s0=0x0 */ /* test case 1 check_round_bit s2=0x18888888 s1=0x88888880 s0=0x0 */ /* test case check_round_bit + normalization s2=0x18888888 s1=0x88888F80 s0=0x0 */ // C.printf("mantissa before rounding: %08x%08x%08x binexp: %d \n", s2,s1,s0,binexp) // s1 => 0xFFFFFFxx only F are rapresented nbit := 7 check_round_bit := u32(1)<> 8) // C.printf("mantissa after rounding : %08x%08x%08x binexp: %d \n", s2,s1,s0,binexp) // C.printf("Tmp result: %016x\n",tmp) // end rounding // offset the binary exponent IEEE 754 binexp += 1023 if binexp > 2046 { if pn.negative { result = double_minus_infinity } else { result = double_plus_infinity } } else if binexp < 1 { if pn.negative { result = double_minus_zero } else { result = double_plus_zero } } else if s2 != 0 { mut q := u64(0) binexs2 := u64(binexp)<<52 q = (u64(s2 & ~mask28)<<24) | ((u64(s1) + u64(128))>>8) | binexs2 if pn.negative { q |= (u64(1)<<63) } result = q } return result } /* Public functions */ // atof64 return a f64 from a string doing a parsing operation pub fn atof64(s string) f64 { mut pn := PrepNumber{ } mut res_parsing := 0 mut res := Float64u{} res_parsing,pn = parser(s + ' ') // TODO: need an extra char for now // println(pn) match res_parsing { parser_ok { res.u = converter(mut pn) } parser_pzero { res.u = double_plus_zero } parser_mzero { res.u = double_minus_zero } parser_pinf { res.u = double_plus_infinity } parser_minf { res.u = double_minus_infinity } else { }} return res.f }