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