- /* 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 = readlinkat (fd, 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)
- /* errno is 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)
- /* errno is ENOMEM. */
- return NULL;
- }