1 /*- 2 * Copyright (c) 1996 Peter Wemm <peter@freebsd.org> 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 14 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 17 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23 * SUCH DAMAGE. 24 */ 25 26 #if defined(LIBC_RCS) && !defined(lint) 27 static char rcsid[] = "$Id: vasprintf.c,v 1.7 1997/07/06 08:42:37 peter Exp $"; 28 #endif /* LIBC_RCS and not lint */ 29 30 #include <stdio.h> 31 #include <stdlib.h> 32 #include <string.h> 33 34 #if __STDC__ 35 #include <stdarg.h> 36 #else 37 #include <varargs.h> 38 #endif 39 40 #define CHUNK_SPARE 128 /* how much spare to allocate to avoid realloc calls */ 41 42 struct bufcookie { 43 char *base; /* start of buffer */ 44 size_t size; 45 size_t left; 46 }; 47 48 static int writehook __P((void *cookie, const char *, int)); 49 50 static int 51 writehook(cookie, buf, len) 52 void *cookie; 53 const char *buf; 54 int len; 55 { 56 struct bufcookie *h = (struct bufcookie *)cookie; 57 char *newbuf; 58 59 if (len == 0) 60 return 0; 61 62 if (len > h->left) { 63 /* grow malloc region */ 64 /* 65 * XXX this is linearly expanded, which is slow for obscenely 66 * large strings. 67 */ 68 h->left = h->left + len + CHUNK_SPARE; 69 h->size = h->size + len + CHUNK_SPARE; 70 newbuf = realloc(h->base, h->size); 71 if (newbuf == NULL) { 72 free(h->base); 73 h->base = NULL; 74 return (-1); 75 } else 76 h->base = newbuf; 77 } 78 /* "write" it */ 79 (void)memcpy(h->base + h->size - h->left, buf, (size_t)len); 80 h->left -= len; 81 return (len); 82 } 83 84 85 int 86 vasprintf(str, fmt, ap) 87 char **str; 88 const char *fmt; 89 va_list ap; 90 { 91 int ret; 92 FILE *f; 93 struct bufcookie h; 94 95 h.base = malloc(CHUNK_SPARE); 96 if (h.base == NULL) 97 return (-1); 98 h.size = CHUNK_SPARE; 99 h.left = CHUNK_SPARE; 100 101 f = funopen(&h, NULL, writehook, NULL, NULL); 102 if (f == NULL) { 103 free(h.base); 104 return (-1); 105 } 106 ret = vfprintf(f, fmt, ap); 107 fclose(f); 108 109 /* 110 * clean up the wreckage. Did writehook fail or did something else 111 * in stdio explode perhaps? 112 */ 113 if (h.base == NULL) /* realloc failed in writehook */ 114 return (-1); 115 if (ret < 0) { /* something else? */ 116 free(h.base); 117 return (-1); 118 } 119 120 /* 121 * At this point, we have a non-null terminated string in a 122 * buffer. There may not be enough room to null-terminate it 123 * (h.left == 0) - if realloc failes to expand it, it's fatal. 124 * If we were merely trying to shrink the buffer, a realloc failure 125 * is not [yet] fatal. Note that when realloc returns NULL, 126 * the original buffer is left allocated and valid. 127 */ 128 if (h.left == 1) /* exact fit, do not realloc */ 129 *str = h.base; 130 else { 131 *str = realloc(h.base, (size_t)(h.size - h.left + 1)); 132 if (*str == NULL) { 133 /* failed to expand? - fatal */ 134 if (h.left == 0) { 135 free(h.base); 136 return (-1); 137 } 138 *str = h.base; /* use oversize original buffer */ 139 } 140 } 141 (*str)[h.size - h.left] = '\0'; 142 return (ret); 143 } 144