1/* __gmp_snprintf_funs -- support for gmp_snprintf and gmp_vsnprintf.
2
3   THE FUNCTIONS IN THIS FILE ARE FOR INTERNAL USE ONLY.  THEY'RE ALMOST
4   CERTAIN TO BE SUBJECT TO INCOMPATIBLE CHANGES OR DISAPPEAR COMPLETELY IN
5   FUTURE GNU MP RELEASES.
6
7Copyright 2001, 2002, 2018 Free Software Foundation, Inc.
8
9This file is part of the GNU MP Library.
10
11The GNU MP Library is free software; you can redistribute it and/or modify
12it under the terms of either:
13
14  * the GNU Lesser General Public License as published by the Free
15    Software Foundation; either version 3 of the License, or (at your
16    option) any later version.
17
18or
19
20  * the GNU General Public License as published by the Free Software
21    Foundation; either version 2 of the License, or (at your option) any
22    later version.
23
24or both in parallel, as here.
25
26The GNU MP Library is distributed in the hope that it will be useful, but
27WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
28or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
29for more details.
30
31You should have received copies of the GNU General Public License and the
32GNU Lesser General Public License along with the GNU MP Library.  If not,
33see https://www.gnu.org/licenses/.  */
34
35#include <stdarg.h>
36#include <stdio.h>
37#include <string.h>
38
39#include "gmp-impl.h"
40
41
42#if ! HAVE_VSNPRINTF
43#define vsnprintf  __gmp_replacement_vsnprintf
44#endif
45
46
47/* glibc 2.0.x vsnprintf returns either -1 or size-1 for an overflow, with
48   no indication how big the output would have been.  It's necessary to
49   re-run to determine that size.
50
51   "size-1" would mean success from a C99 vsnprintf, and the re-run is
52   unnecessary in this case, but we don't bother to try to detect what sort
53   of vsnprintf we've got.  size-1 should occur rarely in normal
54   circumstances.
55
56   vsnprintf might trash it's given ap (it does for instance in glibc 2.1.3
57   on powerpc), so copy it in case we need to use it to probe for the size
58   output that would have been produced.  Note there's no need to preserve
59   it for our callers, just for ourselves.  */
60
61static int
62gmp_snprintf_format (struct gmp_snprintf_t *d, const char *fmt,
63                     va_list orig_ap)
64{
65  int      ret;
66  size_t   step, alloc, avail;
67  va_list  ap;
68  char     *p;
69
70  ASSERT (d->size >= 0);
71
72  avail = d->size;
73  if (avail > 1)
74    {
75      va_copy (ap, orig_ap);
76      ret = vsnprintf (d->buf, avail, fmt, ap);
77      if (ret == -1)
78        return ret;
79
80      step = MIN (ret, avail-1);
81      d->size -= step;
82      d->buf += step;
83
84      if (ret != avail-1)
85        return ret;
86
87      /* probably glibc 2.0.x truncated output, probe for actual size */
88      alloc = MAX (128, ret);
89    }
90  else
91    {
92      /* no space to write anything, just probe for size */
93      alloc = 128;
94    }
95
96  do
97    {
98      alloc *= 2;
99      p = __GMP_ALLOCATE_FUNC_TYPE (alloc, char);
100      va_copy (ap, orig_ap);
101      ret = vsnprintf (p, alloc, fmt, ap);
102      __GMP_FREE_FUNC_TYPE (p, alloc, char);
103    }
104  while (ret == alloc-1);
105
106  return ret;
107}
108
109static int
110gmp_snprintf_memory (struct gmp_snprintf_t *d, const char *str, size_t len)
111{
112  size_t n;
113
114  ASSERT (d->size >= 0);
115
116  if (d->size > 1)
117    {
118      n = MIN (d->size-1, len);
119      memcpy (d->buf, str, n);
120      d->buf += n;
121      d->size -= n;
122    }
123  return len;
124}
125
126static int
127gmp_snprintf_reps (struct gmp_snprintf_t *d, int c, int reps)
128{
129  size_t n;
130
131  ASSERT (reps >= 0);
132  ASSERT (d->size >= 0);
133
134  if (d->size > 1)
135    {
136      n = MIN (d->size-1, reps);
137      memset (d->buf, c, n);
138      d->buf += n;
139      d->size -= n;
140    }
141  return reps;
142}
143
144static int
145gmp_snprintf_final (struct gmp_snprintf_t *d)
146{
147  if (d->size >= 1)
148    d->buf[0] = '\0';
149  return 0;
150}
151
152const struct doprnt_funs_t  __gmp_snprintf_funs = {
153  (doprnt_format_t) gmp_snprintf_format,
154  (doprnt_memory_t) gmp_snprintf_memory,
155  (doprnt_reps_t)   gmp_snprintf_reps,
156  (doprnt_final_t)  gmp_snprintf_final
157};
158