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