vasprintf.c
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上传日期:2022-08-06
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- /* gmp_vasprintf -- formatted output to an allocated space.
- Copyright 2001 Free Software Foundation, Inc.
- This file is part of the GNU MP Library.
- The GNU MP Library is free software; you can redistribute it and/or modify
- it under the terms of the GNU Lesser General Public License as published by
- the Free Software Foundation; either version 3 of the License, or (at your
- option) any later version.
- The GNU MP Library 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 Lesser General Public
- License for more details.
- You should have received a copy of the GNU Lesser General Public License
- along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */
- #include "config.h"
- #if HAVE_STDARG
- #include <stdarg.h>
- #else
- #include <varargs.h>
- #endif
- #include <stdio.h>
- #include <stdlib.h>
- #include <string.h>
- #include "gmp.h"
- #include "gmp-impl.h"
- #if ! HAVE_VSNPRINTF
- #define vsnprintf __gmp_replacement_vsnprintf
- #endif
- /* vasprintf isn't used since we prefer all GMP allocs to go through
- __gmp_allocate_func, and in particular we don't want the -1 return from
- vasprintf for out-of-memory, instead __gmp_allocate_func should handle
- that. Using vsnprintf unfortunately means we might have to re-run it if
- our current space is insufficient.
- The initial guess for the needed space is an arbitrary 256 bytes. If
- that (and any extra GMP_ASPRINTF_T_NEED might give) isn't enough then an
- ISO C99 standard vsnprintf will tell us what we really need.
- GLIBC 2.0.x vsnprintf returns either -1 or space-1 to indicate overflow,
- without giving any indication how much is really needed. In this case
- keep trying with double the space each time.
- A return of space-1 is success on a C99 vsnprintf, but we're not
- bothering to identify which style vsnprintf we've got, so just take the
- pessimistic option and assume it's glibc 2.0.x.
- Notice the use of ret+2 for the new space in the C99 case. This ensures
- the next vsnprintf return value will be space-2, which is unambiguously
- successful. But actually GMP_ASPRINTF_T_NEED() will realloc to even
- bigger than that ret+2.
- vsnprintf might trash it's given ap, so copy it in case we need to use it
- more than once. See comments with gmp_snprintf_format. */
- static int
- gmp_asprintf_format (struct gmp_asprintf_t *d, const char *fmt,
- va_list orig_ap)
- {
- int ret;
- va_list ap;
- size_t space = 256;
- for (;;)
- {
- GMP_ASPRINTF_T_NEED (d, space);
- space = d->alloc - d->size;
- va_copy (ap, orig_ap);
- ret = vsnprintf (d->buf + d->size, space, fmt, ap);
- if (ret == -1)
- {
- ASSERT (strlen (d->buf + d->size) == space-1);
- ret = space-1;
- }
- /* done if output fits in our space */
- if (ret < space-1)
- break;
- if (ret == space-1)
- space *= 2; /* possible glibc 2.0.x, so double */
- else
- space = ret+2; /* C99, so now know space required */
- }
- d->size += ret;
- return ret;
- }
- const struct doprnt_funs_t __gmp_asprintf_funs = {
- (doprnt_format_t) gmp_asprintf_format,
- (doprnt_memory_t) __gmp_asprintf_memory,
- (doprnt_reps_t) __gmp_asprintf_reps,
- (doprnt_final_t) __gmp_asprintf_final
- };
- int
- gmp_vasprintf (char **result, const char *fmt, va_list ap)
- {
- struct gmp_asprintf_t d;
- GMP_ASPRINTF_T_INIT (d, result);
- return __gmp_doprnt (&__gmp_asprintf_funs, &d, fmt, ap);
- }