source/libs/gmp/gmp-src/printf/vasprintf.c

   1 /* gmp_vasprintf -- formatted output to an allocated space.
   2
   3 Copyright 2001 Free Software Foundation, Inc.
   4
   5 This file is part of the GNU MP Library.
   6
   7 The GNU MP Library is free software; you can redistribute it and/or modify
   8 it under the terms of either:
   9
  10   * the GNU Lesser General Public License as published by the Free
  11     Software Foundation; either version 3 of the License, or (at your
  12     option) any later version.
  13
  14 or
  15
  16   * the GNU General Public License as published by the Free Software
  17     Foundation; either version 2 of the License, or (at your option) any
  18     later version.
  19
  20 or both in parallel, as here.
  21
  22 The GNU MP Library is distributed in the hope that it will be useful, but
  23 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  24 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  25 for more details.
  26
  27 You should have received copies of the GNU General Public License and the
  28 GNU Lesser General Public License along with the GNU MP Library.  If not,
  29 see https://www.gnu.org/licenses/.  */
  30
  31 #include <stdarg.h>
  32 #include <stdio.h>
  33 #include <stdlib.h>
  34 #include <string.h>
  35
  36 #include "gmp.h"
  37 #include "gmp-impl.h"
  38
  39 #if ! HAVE_VSNPRINTF
  40 #define vsnprintf  __gmp_replacement_vsnprintf
  41 #endif
  42
  43
  44 /* vasprintf isn't used since we prefer all GMP allocs to go through
  45    __gmp_allocate_func, and in particular we don't want the -1 return from
  46    vasprintf for out-of-memory, instead __gmp_allocate_func should handle
  47    that.  Using vsnprintf unfortunately means we might have to re-run it if
  48    our current space is insufficient.
  49
  50    The initial guess for the needed space is an arbitrary 256 bytes.  If
  51    that (and any extra GMP_ASPRINTF_T_NEED might give) isn't enough then an
  52    ISO C99 standard vsnprintf will tell us what we really need.
  53
  54    GLIBC 2.0.x vsnprintf returns either -1 or space-1 to indicate overflow,
  55    without giving any indication how much is really needed.  In this case
  56    keep trying with double the space each time.
  57
  58    A return of space-1 is success on a C99 vsnprintf, but we're not
  59    bothering to identify which style vsnprintf we've got, so just take the
  60    pessimistic option and assume it's glibc 2.0.x.
  61
  62    Notice the use of ret+2 for the new space in the C99 case.  This ensures
  63    the next vsnprintf return value will be space-2, which is unambiguously
  64    successful.  But actually GMP_ASPRINTF_T_NEED() will realloc to even
  65    bigger than that ret+2.
  66
  67    vsnprintf might trash it's given ap, so copy it in case we need to use it
  68    more than once.  See comments with gmp_snprintf_format.  */
  69
  70 static int
  71 gmp_asprintf_format (struct gmp_asprintf_t *d, const char *fmt,
  72                      va_list orig_ap)
  73 {
  74   int      ret;
  75   va_list  ap;
  76   size_t   space = 256;
  77
  78   for (;;)
  79     {
  80       GMP_ASPRINTF_T_NEED (d, space);
  81       space = d->alloc - d->size;
  82       va_copy (ap, orig_ap);
  83       ret = vsnprintf (d->buf + d->size, space, fmt, ap);
  84       if (ret == -1)
  85         {
  86           ASSERT (strlen (d->buf + d->size) == space-1);
  87           ret = space-1;
  88         }
  89
  90       /* done if output fits in our space */
  91       if (ret < space-1)
  92         break;
  93
  94       if (ret == space-1)
  95         space *= 2;     /* possible glibc 2.0.x, so double */
  96       else
  97         space = ret+2;  /* C99, so now know space required */
  98     }
  99
 100   d->size += ret;
 101   return ret;
 102 }
 103
 104 const struct doprnt_funs_t  __gmp_asprintf_funs = {
 105   (doprnt_format_t) gmp_asprintf_format,
 106   (doprnt_memory_t) __gmp_asprintf_memory,
 107   (doprnt_reps_t)   __gmp_asprintf_reps,
 108   (doprnt_final_t)  __gmp_asprintf_final
 109 };
 110
 111 int
 112 gmp_vasprintf (char **result, const char *fmt, va_list ap)
 113 {
 114   struct gmp_asprintf_t  d;
 115   GMP_ASPRINTF_T_INIT (d, result);
 116   return __gmp_doprnt (&__gmp_asprintf_funs, &d, fmt, ap);
 117 }