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#
#
# Nim's Runtime Library
# (c) Copyright 2022 Nim contributors
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
## This module implements formatting floats as strings.
when defined(nimPreviewSlimSystem):
import std/assertions
proc c_memcpy(a, b: pointer, size: csize_t): pointer {.importc: "memcpy", header: "<string.h>", discardable.}
proc addCstringN(result: var string, buf: cstring; buflen: int) =
# no nimvm support needed, so it doesn't need to be fast here either
let oldLen = result.len
let newLen = oldLen + buflen
result.setLen newLen
c_memcpy(result[oldLen].addr, buf, buflen.csize_t)
import std/private/[dragonbox, schubfach]
proc writeFloatToBufferRoundtrip*(buf: var array[65, char]; value: BiggestFloat): int =
## This is the implementation to format floats.
##
## returns the amount of bytes written to `buf` not counting the
## terminating '\0' character.
result = toChars(buf, value, forceTrailingDotZero=true).int
buf[result] = '\0'
proc writeFloatToBufferRoundtrip*(buf: var array[65, char]; value: float32): int =
result = float32ToChars(buf, value, forceTrailingDotZero=true).int
buf[result] = '\0'
proc c_snprintf(buf: cstring, n: csize_t, frmt: cstring): cint {.header: "<stdio.h>",
importc: "snprintf", varargs, noSideEffect.}
proc writeToBuffer(buf: var array[65, char]; value: cstring) =
var i = 0
while value[i] != '\0':
buf[i] = value[i]
inc i
proc writeFloatToBufferSprintf*(buf: var array[65, char]; value: BiggestFloat): int =
## This is the implementation to format floats.
##
## returns the amount of bytes written to `buf` not counting the
## terminating '\0' character.
var n = c_snprintf(cast[cstring](addr buf), 65, "%.16g", value).int
var hasDot = false
for i in 0..n-1:
if buf[i] == ',':
buf[i] = '.'
hasDot = true
elif buf[i] in {'a'..'z', 'A'..'Z', '.'}:
hasDot = true
if not hasDot:
buf[n] = '.'
buf[n+1] = '0'
buf[n+2] = '\0'
result = n + 2
else:
result = n
# On Windows nice numbers like '1.#INF', '-1.#INF' or '1.#NAN' or 'nan(ind)'
# of '-1.#IND' are produced.
# We want to get rid of these here:
if buf[n-1] in {'n', 'N', 'D', 'd', ')'}:
writeToBuffer(buf, "nan")
result = 3
elif buf[n-1] == 'F':
if buf[0] == '-':
writeToBuffer(buf, "-inf")
result = 4
else:
writeToBuffer(buf, "inf")
result = 3
proc writeFloatToBuffer*(buf: var array[65, char]; value: BiggestFloat | float32): int {.inline.} =
when defined(nimPreviewFloatRoundtrip) or defined(nimPreviewSlimSystem):
writeFloatToBufferRoundtrip(buf, value)
else:
writeFloatToBufferSprintf(buf, value)
proc addFloatRoundtrip*(result: var string; x: float | float32) =
when nimvm:
raiseAssert "unreachable"
else:
var buffer {.noinit.}: array[65, char]
let n = writeFloatToBufferRoundtrip(buffer, x)
result.addCstringN(cast[cstring](buffer[0].addr), n)
proc addFloatSprintf*(result: var string; x: float) =
when nimvm:
raiseAssert "unreachable"
else:
var buffer {.noinit.}: array[65, char]
let n = writeFloatToBufferSprintf(buffer, x)
result.addCstringN(cast[cstring](buffer[0].addr), n)
when defined(js):
proc nimFloatToString(a: float): cstring =
## ensures the result doesn't print like an integer, i.e. return 2.0, not 2
# print `-0.0` properly
{.emit: """
function nimOnlyDigitsOrMinus(n) {
return n.toString().match(/^-?\d+$/);
}
if (Number.isSafeInteger(`a`))
`result` = `a` === 0 && 1 / `a` < 0 ? "-0.0" : `a`+".0";
else {
`result` = `a`+"";
if(nimOnlyDigitsOrMinus(`result`)){
`result` = `a`+".0";
}
}
""".}
proc addFloat*(result: var string; x: float | float32) {.inline.} =
## Converts float to its string representation and appends it to `result`.
runnableExamples:
var
s = "foo:"
b = 45.67
s.addFloat(45.67)
assert s == "foo:45.67"
template impl =
when defined(nimPreviewFloatRoundtrip) or defined(nimPreviewSlimSystem):
addFloatRoundtrip(result, x)
else:
addFloatSprintf(result, x)
when defined(js):
when nimvm: impl()
else:
result.add nimFloatToString(x)
else: impl()
when defined(nimPreviewSlimSystem):
func `$`*(x: float | float32): string =
## Outplace version of `addFloat`.
result.addFloat(x)
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