e48f3cfbfc
and forgot what I was trying to do originally and accidently zapped a feature. :-] The problem is that we are converting a counted buffer in a malloc pool into a null terminated C-style string. I was calling realloc originally to shrink the buffer to the desired size. If realloc failed, we still returned the valid buffer - the only thing wrong was it was a tad too large. The previous commit disabled this. This commit now handles the three cases.. 1: the buffer is exactly right for the null byte to terminate the string (we don't call realloc). 2: it's got h.left = 0, so we must expand it to make room. If realloc fails here, it's fatal. 3: if there's too much room, we realloc to shrink it - a failed realloc is not fatal, we use the original buffer which is still valid.
143 lines
3.8 KiB
C
143 lines
3.8 KiB
C
/*-
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* Copyright (c) 1996 Peter Wemm <peter@freebsd.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#if defined(LIBC_RCS) && !defined(lint)
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static char rcsid[] = "$Id: vasprintf.c,v 1.6 1997/07/06 07:54:56 peter Exp $";
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#endif /* LIBC_RCS and not lint */
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#include <stdio.h>
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#include <stdlib.h>
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#if __STDC__
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#include <stdarg.h>
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#else
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#include <varargs.h>
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#endif
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#define CHUNK_SPARE 128 /* how much spare to allocate to avoid realloc calls */
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struct bufcookie {
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char *base; /* start of buffer */
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size_t size;
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size_t left;
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};
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static int writehook __P((void *cookie, const char *, int));
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static int
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writehook(cookie, buf, len)
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void *cookie;
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const char *buf;
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int len;
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{
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struct bufcookie *h = (struct bufcookie *)cookie;
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char *newbuf;
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if (len == 0)
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return 0;
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if (len > h->left) {
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/* grow malloc region */
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/*
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* XXX this is linearly expanded, which is slow for obscenely
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* large strings.
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*/
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h->left = h->left + len + CHUNK_SPARE;
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h->size = h->size + len + CHUNK_SPARE;
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newbuf = realloc(h->base, h->size);
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if (newbuf == NULL) {
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free(h->base);
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h->base = NULL;
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return (-1);
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} else
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h->base = newbuf;
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}
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/* "write" it */
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(void)memcpy(h->base + h->size - h->left, buf, (size_t)len);
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h->left -= len;
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return (len);
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}
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int
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vasprintf(str, fmt, ap)
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char **str;
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const char *fmt;
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va_list ap;
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{
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int ret;
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FILE *f;
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struct bufcookie h;
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h.base = malloc(CHUNK_SPARE);
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if (h.base == NULL)
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return (-1);
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h.size = CHUNK_SPARE;
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h.left = CHUNK_SPARE;
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f = funopen(&h, NULL, writehook, NULL, NULL);
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if (f == NULL) {
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free(h.base);
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return (-1);
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}
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ret = vfprintf(f, fmt, ap);
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fclose(f);
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/*
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* clean up the wreckage. Did writehook fail or did something else
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* in stdio explode perhaps?
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*/
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if (h.base == NULL) /* realloc failed in writehook */
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return (-1);
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if (ret < 0) { /* something else? */
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free(h.base);
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return (-1);
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}
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/*
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* At this point, we have a non-null terminated string in a
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* buffer. There may not be enough room to null-terminate it
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* (h.left == 0) - if realloc failes to expand it, it's fatal.
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* If we were merely trying to shrink the buffer, a realloc failure
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* is not [yet] fatal. Note that when realloc returns NULL,
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* the original buffer is left allocated and valid.
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*/
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if (h.left == 1) /* exact fit, do not realloc */
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*str = h.base;
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else {
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*str = realloc(h.base, (size_t)(h.size - h.left + 1));
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if (*str == NULL) {
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/* failed to expand? - fatal */
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if (h.left == 0) {
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free(h.base);
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return (-1);
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}
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*str = h.base; /* use oversize original buffer */
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}
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}
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(*str)[h.size - h.left] = '\0';
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return (ret);
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}
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