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/*
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright © 2022 Keith Packard
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials provided
* with the distribution.
*
* 3. Neither the name of the copyright holder nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#define _GNU_SOURCE
#include "ftoa_engine.h"
#include <_ansi.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
int
fcvtf_r (float invalue,
int ndecimal,
int *decpt,
int *sign,
char *buf,
size_t len)
{
struct ftoa ftoa;
int ntrailing; /* number of zeros to add after the value */
int ndigit; /* numer of generated digits */
int ftoa_decimal = ndecimal;
char *digits = ftoa.digits;
if (!__finitef(invalue)) {
ndigit = 3;
ntrailing = 0;
*sign = invalue < 0;
*decpt = 0;
if (isnan(invalue))
digits = "nan";
else
digits = "inf";
} else {
/* ndecimal = digits after decimal point desired
* ndigit = digits actually generated
* ftoa.exp = exponent (position of decimal relative to first digit generated)
*/
if (ndecimal < 0)
ftoa_decimal = 0;
ndigit = __ftoa_engine(invalue, &ftoa, FTOA_MAX_DIG, true, ndecimal);
*sign = !!(ftoa.flags & FTOA_MINUS);
/*
* To compute the number of zeros added after the value, there are
* three cases:
*
* 1. all of the generated digits are left of the decimal
* point (ftoa.exp >= ndigit). We need (ftoa.exp - ndigit)
* digits left of the decimal and ndecimal right of the
* decimal: (ftoa.exp - ndigit) + ndecimal
*
* 2. some of the generated digits are right
* of the decimal point (ftoa.exp < ndigit). We need
* ndecimal digits total, but we have (ndigit - ftoa.exp)
* already, so: ndecimal - (ndigit - ftoa.exp).
*
* 3. all of the generated digits are right of the decimal point
* We need fewer than ndecimal digits by the magnitude of
* the exponent (which is negative in this case, so:
* ndecimal - (-ftoa.exp - 1) - ndigit
*
* These all turn out to be the same computation. Kinda cool.
*/
ntrailing = (ftoa.exp + 1 - ndigit) + ftoa_decimal;
/*
* If this value is negative, then we actually have *no* digits to
* generate. In this case, we return the empty string and set the
* exponent to the number of digits requested (as they're all
* zero)
*/
if (ntrailing < 0) {
ntrailing = 0;
ndigit = 0;
/*
* Adjust exponent to reflect the desired output of ndecimal
* zeros
*/
ftoa.exp = -(ftoa_decimal + 1);
}
*decpt = ftoa.exp + 1;
}
/* If we can't fit the whole value in the provided space,
* return an error
*/
if ((size_t) (ndigit + ntrailing) >= len)
return -1;
/* Value */
memcpy(buf, digits, ndigit);
len -= ndigit;
buf += ndigit;
/* Trailing zeros */
memset(buf, '0', ntrailing);
buf += ntrailing;
/* Null terminate */
buf[0] = '\0';
return 0;
}
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