/* areadlink.c -- readlink wrapper to return the link name in malloc'd storage
Unlike xreadlink and xreadlink_with_size, don't ever call exit.
- Copyright (C) 2001, 2003-2007, 2009-2011 Free Software Foundation, Inc.
+ Copyright (C) 2001, 2003-2007, 2009-2013 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
/* Specification. */
#include "areadlink.h"
-#include <errno.h>
-#include <limits.h>
-#include <stdint.h>
+#include "careadlinkat.h"
+
#include <stdlib.h>
-#include <string.h>
#include <unistd.h>
-#ifndef SSIZE_MAX
-# define SSIZE_MAX ((ssize_t) (SIZE_MAX / 2))
-#endif
-
-/* Use the system functions, not the gnulib overrides in this file. */
-#undef malloc
-#undef realloc
-
-/* The initial buffer size for the link value. A power of 2
- detects arithmetic overflow earlier, but is not required. */
-enum {
- INITIAL_BUF_SIZE = 1024
-};
+/* Get the symbolic link value of FILENAME and put it into BUFFER, with
+ size BUFFER_SIZE. This function acts like readlink but has
+ readlinkat's signature. */
+static ssize_t
+careadlinkatcwd (int fd, char const *filename, char *buffer,
+ size_t buffer_size)
+{
+ /* FD must be AT_FDCWD here, otherwise the caller is using this
+ function in contexts it was not meant for. */
+ if (fd != AT_FDCWD)
+ abort ();
+ return readlink (filename, buffer, buffer_size);
+}
/* Call readlink to get the symbolic link value of FILENAME.
Return a pointer to that NUL-terminated string in malloc'd storage.
If readlink fails, return NULL and set errno.
- If realloc fails, or if the link value is longer than SIZE_MAX :-),
+ If allocation fails, or if the link value is longer than SIZE_MAX :-),
return NULL and set errno to ENOMEM. */
char *
areadlink (char const *filename)
{
- /* Allocate the initial buffer on the stack. This way, in the common
- case of a symlink of small size, we get away with a single small malloc()
- instead of a big malloc() followed by a shrinking realloc(). */
- char initial_buf[INITIAL_BUF_SIZE];
-
- char *buffer = initial_buf;
- size_t buf_size = sizeof initial_buf;
-
- while (1)
- {
- /* Attempt to read the link into the current buffer. */
- ssize_t link_length = readlink (filename, buffer, buf_size);
-
- /* On AIX 5L v5.3 and HP-UX 11i v2 04/09, readlink returns -1
- with errno == ERANGE if the buffer is too small. */
- if (link_length < 0 && errno != ERANGE)
- {
- if (buffer != initial_buf)
- {
- int saved_errno = errno;
- free (buffer);
- errno = saved_errno;
- }
- return NULL;
- }
-
- if ((size_t) link_length < buf_size)
- {
- buffer[link_length++] = '\0';
-
- /* Return it in a chunk of memory as small as possible. */
- if (buffer == initial_buf)
- {
- buffer = (char *) malloc (link_length);
- if (buffer == NULL)
- {
- /* It's easier to set errno to ENOMEM than to rely on the
- 'malloc-posix' gnulib module. */
- errno = ENOMEM;
- return NULL;
- }
- memcpy (buffer, initial_buf, link_length);
- }
- else
- {
- /* Shrink buffer before returning it. */
- if ((size_t) link_length < buf_size)
- {
- char *smaller_buffer = (char *) realloc (buffer, link_length);
-
- if (smaller_buffer != NULL)
- buffer = smaller_buffer;
- }
- }
- return buffer;
- }
-
- if (buffer != initial_buf)
- free (buffer);
- buf_size *= 2;
- if (SSIZE_MAX < buf_size || (SIZE_MAX / 2 < SSIZE_MAX && buf_size == 0))
- {
- errno = ENOMEM;
- return NULL;
- }
- buffer = (char *) malloc (buf_size);
- if (buffer == NULL)
- {
- /* It's easier to set errno to ENOMEM than to rely on the
- 'malloc-posix' gnulib module. */
- errno = ENOMEM;
- return NULL;
- }
- }
+ return careadlinkat (AT_FDCWD, filename, NULL, 0, NULL, careadlinkatcwd);
}
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