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/* fpconv - Floating point conversion routines
*
* Copyright (c) 2011-2012 Mark Pulford <mark@kyne.com.au>
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
/* JSON uses a '.' decimal separator. strtod() / sprintf() under C libraries
* with locale support will break when the decimal separator is a comma.
*
* fpconv_* will around these issues with a translation buffer if required.
*/
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <string.h>
#include "fpconv.h"
/* Lua CJSON assumes the locale is the same for all threads within a
* process and doesn't change after initialisation.
*
* This avoids the need for per thread storage or expensive checks
* for call. */
static char locale_decimal_point = '.';
/* In theory multibyte decimal_points are possible, but
* Lua CJSON only supports UTF-8 and known locales only have
* single byte decimal points ([.,]).
*
* localconv() may not be thread safe (=>crash), and nl_langinfo() is
* not supported on some platforms. Use sprintf() instead - if the
* locale does change, at least Lua CJSON won't crash. */
static void fpconv_update_locale()
{
char buf[8];
snprintf(buf, sizeof(buf), "%g", 0.5);
/* Failing this test might imply the platform has a buggy dtoa
* implementation or wide characters */
if (buf[0] != '0' || buf[2] != '5' || buf[3] != 0) {
fprintf(stderr, "Error: wide characters found or printf() bug.");
abort();
}
locale_decimal_point = buf[1];
}
/* Check for a valid number character: [-+0-9a-yA-Y.]
* Eg: -0.6e+5, infinity, 0xF0.F0pF0
*
* Used to find the probable end of a number. It doesn't matter if
* invalid characters are counted - strtod() will find the valid
* number if it exists. The risk is that slightly more memory might
* be allocated before a parse error occurs. */
static inline int valid_number_character(char ch)
{
char lower_ch;
if ('0' <= ch && ch <= '9')
return 1;
if (ch == '-' || ch == '+' || ch == '.')
return 1;
/* Hex digits, exponent (e), base (p), "infinity",.. */
lower_ch = ch | 0x20;
if ('a' <= lower_ch && lower_ch <= 'y')
return 1;
return 0;
}
/* Calculate the size of the buffer required for a strtod locale
* conversion. */
static int strtod_buffer_size(const char *s)
{
const char *p = s;
while (valid_number_character(*p))
p++;
return p - s;
}
/* Similar to strtod(), but must be passed the current locale's decimal point
* character. Guaranteed to be called at the start of any valid number in a string */
double fpconv_strtod(const char *nptr, char **endptr)
{
char localbuf[FPCONV_G_FMT_BUFSIZE];
char *buf, *endbuf, *dp;
int buflen;
double value;
/* System strtod() is fine when decimal point is '.' */
if (locale_decimal_point == '.')
return strtod(nptr, endptr);
buflen = strtod_buffer_size(nptr);
if (!buflen) {
/* No valid characters found, standard strtod() return */
*endptr = (char *)nptr;
return 0;
}
/* Duplicate number into buffer */
if (buflen >= FPCONV_G_FMT_BUFSIZE) {
/* Handle unusually large numbers */
buf = (char *)malloc(buflen + 1);
if (!buf) {
fprintf(stderr, "Out of memory");
abort();
}
} else {
/* This is the common case.. */
buf = localbuf;
}
memcpy(buf, nptr, buflen);
buf[buflen] = 0;
/* Update decimal point character if found */
dp = strchr(buf, '.');
if (dp)
*dp = locale_decimal_point;
value = strtod(buf, &endbuf);
*endptr = (char *)&nptr[endbuf - buf];
if (buflen >= FPCONV_G_FMT_BUFSIZE)
free(buf);
return value;
}
/* "fmt" must point to a buffer of at least 6 characters */
static void set_number_format(char *fmt, int precision)
{
int d1, d2, i;
assert(1 <= precision && precision <= 14);
/* Create printf format (%.14g) from precision */
d1 = precision / 10;
d2 = precision % 10;
fmt[0] = '%';
fmt[1] = '.';
i = 2;
if (d1) {
fmt[i++] = '0' + d1;
}
fmt[i++] = '0' + d2;
fmt[i++] = 'g';
fmt[i] = 0;
}
/* Assumes there is always at least 32 characters available in the target buffer */
int fpconv_g_fmt(char *str, double num, int precision)
{
char buf[FPCONV_G_FMT_BUFSIZE];
char fmt[6];
int len;
char *b;
set_number_format(fmt, precision);
/* Pass through when decimal point character is dot. */
if (locale_decimal_point == '.')
return snprintf(str, FPCONV_G_FMT_BUFSIZE, fmt, num);
/* snprintf() to a buffer then translate for other decimal point characters */
len = snprintf(buf, FPCONV_G_FMT_BUFSIZE, fmt, num);
/* Copy into target location. Translate decimal point if required */
b = buf;
do {
*str++ = (*b == locale_decimal_point ? '.' : *b);
} while(*b++);
return len;
}
void fpconv_init()
{
fpconv_update_locale();
}
/* vi:ai et sw=4 ts=4:
*/
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