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