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/* Gdtoa.c provides access to double string conversion.
Copyright (C) 2016-2024 Free Software Foundation, Inc.
Contributed by Gaius Mulley <gaius@glam.ac.uk>.
This file is part of GNU Modula-2.
GNU Modula-2 is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.
GNU Modula-2 is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with GNU Modula-2; see the file COPYING3. If not see
<http://www.gnu.org/licenses/>. */
#define GM2
#include "config.h"
#include "system.h"
#ifdef __cplusplus
extern "C" {
#endif
#define MAX_FP_DIGITS 500
typedef enum Mode { maxsignicant, decimaldigits } Mode;
/* maxsignicant: return a string containing max(1,ndigits)
significant digits. The return string contains the string
produced by ecvt. decimaldigits: return a string produced by
fcvt. The string will contain ndigits past the decimal point
(ndigits may be negative). */
double
dtoa_strtod (const char *s, int *error)
{
char *endp;
double d;
errno = 0;
d = strtod (s, &endp);
if (endp != NULL && (*endp == '\0'))
*error = (errno != 0);
else
*error = TRUE;
return d;
}
/* dtoa_calcmaxsig - calculates the position of the decimal point it
also removes the decimal point and exponent from string, p. */
int
dtoa_calcmaxsig (char *p, int ndigits)
{
char *e;
char *o;
int x;
e = index (p, 'E');
if (e == NULL)
x = 0;
else
{
*e = (char)0;
x = atoi (e + 1);
}
o = index (p, '.');
if (o == NULL)
return strlen (p) + x;
else
{
memmove (o, o + 1, ndigits - (o - p));
return o - p + x;
}
}
/* dtoa_calcdecimal - calculates the position of the decimal point it
also removes the decimal point and exponent from string, p. It
truncates the digits in p accordingly to ndigits. Ie ndigits is
the number of digits after the '.' */
int
dtoa_calcdecimal (char *p, int str_size, int ndigits)
{
char *e;
char *o;
int x;
int l;
e = index (p, 'E');
if (e == NULL)
x = 0;
else
{
*e = (char)0;
x = atoi (e + 1);
}
l = strlen (p);
o = index (p, '.');
if (o == NULL)
x += strlen (p);
else
{
int m = strlen (o);
memmove (o, o + 1, l - (o - p));
if (m > 0)
o[m - 1] = '0';
x += o - p;
}
if ((x + ndigits >= 0) && (x + ndigits < str_size))
p[x + ndigits] = (char)0;
return x;
}
int
dtoa_calcsign (char *p, int str_size)
{
if (p[0] == '-')
{
memmove (p, p + 1, str_size - 1);
return TRUE;
}
else
return FALSE;
}
char *
dtoa_dtoa (double d, int mode, int ndigits, int *decpt, int *sign)
{
char format[50];
char *p;
int r;
switch (mode)
{
case maxsignicant:
ndigits += 20; /* enough for exponent. */
p = (char *) malloc (ndigits);
snprintf (format, 50, "%s%d%s", "%.", ndigits - 20, "E");
snprintf (p, ndigits, format, d);
*sign = dtoa_calcsign (p, ndigits);
*decpt = dtoa_calcmaxsig (p, ndigits);
return p;
case decimaldigits:
p = (char *) malloc (MAX_FP_DIGITS + 20);
snprintf (format, 50, "%s%d%s", "%.", MAX_FP_DIGITS, "E");
snprintf (p, MAX_FP_DIGITS + 20, format, d);
*sign = dtoa_calcsign (p, MAX_FP_DIGITS + 20);
*decpt = dtoa_calcdecimal (p, MAX_FP_DIGITS + 20, ndigits);
return p;
default:
abort ();
}
}
#if defined(GM2)
/* GNU Modula-2 hooks */
void
_M2_dtoa_init (void)
{
}
void
_M2_dtoa_finish (void)
{
}
#endif
#ifdef __cplusplus
}
#endif
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