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/* $Id: symlinks.c,v 1.5 2019/05/08 21:30:11 benno Exp $ */
/*
* Copyright (c) 2019 Kristaps Dzonsons <kristaps@bsd.lv>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/param.h>
#include <assert.h>
#include <stdint.h>
#include <stdlib.h>
#include <unistd.h>
#include "extern.h"
/*
* Allocate space for a readlink(2) invocation.
* Returns NULL on failure or a buffer otherwise.
* The buffer must be passed to free() by the caller.
*/
char *
symlink_read(const char *path)
{
char *buf = NULL;
size_t sz;
ssize_t nsz = 0;
void *pp;
for (sz = MAXPATHLEN; ; sz *= 2) {
if ((pp = realloc(buf, sz + 1)) == NULL) {
ERR("realloc");
free(buf);
return NULL;
}
buf = pp;
if ((nsz = readlink(path, buf, sz)) == -1) {
ERR("%s: readlink", path);
free(buf);
return NULL;
} else if (nsz == 0) {
ERRX("%s: empty link", path);
free(buf);
return NULL;
} else if ((size_t)nsz < sz)
break;
}
assert(buf != NULL);
assert(nsz > 0);
buf[nsz] = '\0';
return buf;
}
/*
* Allocate space for a readlinkat(2) invocation.
* Returns NULL on failure or a buffer otherwise.
* The buffer must be passed to free() by the caller.
*/
char *
symlinkat_read(int fd, const char *path)
{
char *buf = NULL;
size_t sz;
ssize_t nsz = 0;
void *pp;
for (sz = MAXPATHLEN; ; sz *= 2) {
if ((pp = realloc(buf, sz + 1)) == NULL) {
ERR("realloc");
free(buf);
return NULL;
}
buf = pp;
if ((nsz = readlinkat(fd, path, buf, sz)) == -1) {
ERR("%s: readlinkat", path);
free(buf);
return NULL;
} else if (nsz == 0) {
ERRX("%s: empty link", path);
free(buf);
return NULL;
} else if ((size_t)nsz < sz)
break;
}
assert(buf != NULL);
assert(nsz > 0);
buf[nsz] = '\0';
return buf;
}
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