diff options
| -rw-r--r-- | lib/system/sysstr.nim | 141 |
1 files changed, 104 insertions, 37 deletions
diff --git a/lib/system/sysstr.nim b/lib/system/sysstr.nim index f8b93a2c3..b1a3bee55 100644 --- a/lib/system/sysstr.nim +++ b/lib/system/sysstr.nim @@ -304,43 +304,37 @@ proc nimFloatToStr(f: float): string {.compilerproc.} = proc strtod(buf: cstring, endptr: ptr cstring): float64 {.importc, header: "<stdlib.h>", noSideEffect.} -var decimalPoint: char - -proc getDecimalPoint(): char = - result = decimalPoint - if result == '\0': - if strtod("0,5", nil) == 0.5: result = ',' - else: result = '.' - # yes this is threadsafe in practice, spare me: - decimalPoint = result - const IdentChars = {'a'..'z', 'A'..'Z', '0'..'9', '_'} + powtens = [ 1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9, + 1e10, 1e11, 1e12, 1e13, 1e14, 1e15, 1e16, 1e17, 1e18, 1e19, + 1e20, 1e21, 1e22] proc nimParseBiggestFloat(s: string, number: var BiggestFloat, start = 0): int {.compilerProc.} = - # This routine leverages `strtod()` for the non-trivial task of - # parsing floating point numbers correctly. Because `strtod()` is - # locale-dependent with respect to the radix character, we create - # a copy where the decimal point is replaced with the locale's - # radix character. + # This routine attempt to parse float that can parsed quickly. + # ie whose integer part can fit inside a 53bits integer. + # their real exponent must also be <= 22. If the float doesn't follow + # these restrictions, transform the float into this form: + # INTEGER * 10 ^ exponent and leave the work to standard `strtod()`. + # This avoid the problems of decimal character portability. + # see: http://www.exploringbinary.com/fast-path-decimal-to-floating-point-conversion/ var i = start sign = 1.0 - t: array[500, char] # flaviu says: 325 is the longest reasonable literal - ti = 0 - hasdigits = false - - template addToBuf(c) = - if ti < t.high: - t[ti] = c; inc(ti) + kdigits, fdigits = 0 + exponent: int + integer: uint64 + fraction: uint64 + frac_exponent= 0 + exp_sign = 1 + first_digit = 0 # Sign? if s[i] == '+' or s[i] == '-': if s[i] == '-': sign = -1.0 - t[ti] = s[i] - inc(i); inc(ti) + inc(i) # NaN? if s[i] == 'N' or s[i] == 'n': @@ -360,40 +354,113 @@ proc nimParseBiggestFloat(s: string, number: var BiggestFloat, return i+3 - start return 0 + # Skip leading zero + while s[i] == '0': + inc(i) + + if s[i] in {'0'..'9'}: + first_digit = (s[i].ord - '0'.ord) # Integer part? while s[i] in {'0'..'9'}: - hasdigits = true - addToBuf(s[i]) + inc(kdigits) + integer = integer * 10'u64 + (s[i].ord - '0'.ord).uint64 inc(i); while s[i] == '_': inc(i) # Fractional part? if s[i] == '.': - addToBuf(getDecimalPoint()) inc(i) + # if no integer part, Skip leading zeros + if kdigits <= 0: + while s[i] in {'_','0'}: + inc(i) + inc(frac_exponent) + + if s[i] in {'0'..'9'}: + first_digit = (s[i].ord - '0'.ord) + # get fractional part while s[i] in {'0'..'9'}: - hasdigits = true - addToBuf(s[i]) + inc(fdigits) + inc(frac_exponent) + integer = integer * 10'u64 + (s[i].ord - '0'.ord).uint64 inc(i) while s[i] == '_': inc(i) - if not hasdigits: + + # if has no digits: return error + # test for special case 0.0'f + if kdigits + fdigits <= 0 and i == start: return 0 - # Exponent? if s[i] in {'e', 'E'}: - addToBuf(s[i]) inc(i) - if s[i] in {'+', '-'}: - addToBuf(s[i]) + if s[i] == '+' or s[i] == '-': + if s[i] == '-': + exp_sign = -1 + inc(i) if s[i] notin {'0'..'9'}: return 0 while s[i] in {'0'..'9'}: - addToBuf(s[i]) + exponent = exponent * 10 + (ord(s[i]) - ord('0')) inc(i) - while s[i] == '_': inc(i) - number = strtod(t, nil) + while s[i] == '_': inc(i) # underscores are allowed and ignored + + var real_exponent = exp_sign*exponent - frac_exponent + let exp_negative = real_exponent < 0 + var abs_exponent = abs(real_exponent) + + # if exponent greater than can be represented: +/- zero or infinity + if abs_exponent > 999: + if exp_negative: + number = 0.0*sign + else: + number = Inf*sign + return i - start + + # if integer is representable in 53 bits: fast path + # max fast path integer is 1<<53 - 1 or 8999999999999999 (16 digits) + if kdigits + fdigits <= 16 and first_digit <= 8: + # max float power of ten with set bits above the 53th bit is 10^22 + if abs_exponent <= 22: + if exp_negative: + number = sign * integer.float / powtens[abs_exponent] + else: + number = sign * integer.float * powtens[abs_exponent] + return i - start + + # if exponent is greater try to fit extra exponent above 22 by multiplying + # integer part is there is space left. + let slop = 15 - kdigits - fdigits + if abs_exponent <= 22 + slop and not exp_negative: + number = sign * integer.float * powtens[slop] * powtens[abs_exponent-slop] + return i - start + + # if failed: slow path with strtod. + var t: array[500, char] # flaviu says: 325 is the longest reasonable literal + var ti = 0 + let maxlen = t.high - "e+000".len # reserve enough space for exponent + result = i - start + i = start + # re-parse without error checking, any error should be handled by the code above. + while s[i] in {'0'..'9','+','-'}: + if ti < maxlen: + t[ti] = s[i]; inc(ti) + inc(i) + while s[i] in {'.', '_'}: # skip underscore and decimal point + inc(i) + + # insert exponent + t[ti] = 'E'; inc(ti) + t[ti] = if exp_negative: '-' else: '+'; inc(ti) + inc(ti, 3) + + # insert adjusted exponent + t[ti-1] = ('0'.ord + abs_exponent mod 10).char; abs_exponent = abs_exponent div 10 + t[ti-2] = ('0'.ord + abs_exponent mod 10).char; abs_exponent = abs_exponent div 10 + t[ti-3] = ('0'.ord + abs_exponent mod 10).char + + number = strtod(t, nil) proc nimInt64ToStr(x: int64): string {.compilerRtl.} = result = newString(sizeof(x)*4) |