gcc/gmp/printf/vasprintf.c

/* 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);
}