summaryrefslogtreecommitdiff
path: root/gnulib/lib/careadlinkat.c
diff options
context:
space:
mode:
Diffstat (limited to 'gnulib/lib/careadlinkat.c')
m---------gnulib0
-rw-r--r--gnulib/lib/careadlinkat.c175
2 files changed, 175 insertions, 0 deletions
diff --git a/gnulib b/gnulib
deleted file mode 160000
-Subproject 443bc5ffcf7429e557f4a371b0661abe98ddbc1
diff --git a/gnulib/lib/careadlinkat.c b/gnulib/lib/careadlinkat.c
new file mode 100644
index 0000000..751578b
--- /dev/null
+++ b/gnulib/lib/careadlinkat.c
@@ -0,0 +1,175 @@
+/* Read symbolic links into a buffer without size limitation, relative to fd.
+
+ Copyright (C) 2001, 2003-2004, 2007, 2009-2011 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
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+/* Written by Paul Eggert, Bruno Haible, and Jim Meyering. */
+
+#include <config.h>
+
+#include "careadlinkat.h"
+
+#include <errno.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+/* Define this independently so that stdint.h is not a prerequisite. */
+#ifndef SIZE_MAX
+# define SIZE_MAX ((size_t) -1)
+#endif
+
+#ifndef SSIZE_MAX
+# define SSIZE_MAX ((ssize_t) (SIZE_MAX / 2))
+#endif
+
+#include "allocator.h"
+
+/* 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. */
+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 for which it was not meant for. */
+ if (fd != AT_FDCWD)
+ abort ();
+ return readlink (filename, buffer, buffer_size);
+}
+
+/* Assuming the current directory is FD, get the symbolic link value
+ of FILENAME as a null-terminated string and put it into a buffer.
+ If FD is AT_FDCWD, FILENAME is interpreted relative to the current
+ working directory, as in openat.
+
+ If the link is small enough to fit into BUFFER put it there.
+ BUFFER's size is BUFFER_SIZE, and BUFFER can be null
+ if BUFFER_SIZE is zero.
+
+ If the link is not small, put it into a dynamically allocated
+ buffer managed by ALLOC. It is the caller's responsibility to free
+ the returned value if it is nonnull and is not BUFFER. A null
+ ALLOC stands for the standard allocator.
+
+ The PREADLINKAT function specifies how to read links. It operates
+ like POSIX readlinkat()
+ <http://pubs.opengroup.org/onlinepubs/9699919799/functions/readlink.html>
+ but can assume that its first argument is the same as FD.
+
+ If successful, return the buffer address; otherwise return NULL and
+ set errno. */
+
+char *
+careadlinkat (int fd, char const *filename,
+ char *buffer, size_t buffer_size,
+ struct allocator const *alloc,
+ ssize_t (*preadlinkat) (int, char const *, char *, size_t))
+{
+ char *buf;
+ size_t buf_size;
+ size_t buf_size_max =
+ SSIZE_MAX < SIZE_MAX ? (size_t) SSIZE_MAX + 1 : SIZE_MAX;
+ char stack_buf[1024];
+
+ if (! alloc)
+ alloc = &stdlib_allocator;
+
+ if (! buffer_size)
+ {
+ /* 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(). */
+ buffer = stack_buf;
+ buffer_size = sizeof stack_buf;
+ }
+
+ buf = buffer;
+ buf_size = buffer_size;
+
+ do
+ {
+ /* Attempt to read the link into the current buffer. */
+ ssize_t link_length = preadlinkat (fd, filename, buf, buf_size);
+ size_t link_size;
+ if (link_length < 0)
+ {
+ /* On AIX 5L v5.3 and HP-UX 11i v2 04/09, readlink returns -1
+ with errno == ERANGE if the buffer is too small. */
+ int readlinkat_errno = errno;
+ if (readlinkat_errno != ERANGE)
+ {
+ if (buf != buffer)
+ {
+ alloc->free (buf);
+ errno = readlinkat_errno;
+ }
+ return NULL;
+ }
+ }
+
+ link_size = link_length;
+
+ if (link_size < buf_size)
+ {
+ buf[link_size++] = '\0';
+
+ if (buf == stack_buf)
+ {
+ char *b = (char *) alloc->allocate (link_size);
+ buf_size = link_size;
+ if (! b)
+ break;
+ memcpy (b, buf, link_size);
+ buf = b;
+ }
+ else if (link_size < buf_size && buf != buffer && alloc->reallocate)
+ {
+ /* Shrink BUF before returning it. */
+ char *b = (char *) alloc->reallocate (buf, link_size);
+ if (b)
+ buf = b;
+ }
+
+ return buf;
+ }
+
+ if (buf != buffer)
+ alloc->free (buf);
+
+ if (buf_size <= buf_size_max / 2)
+ buf_size *= 2;
+ else if (buf_size < buf_size_max)
+ buf_size = buf_size_max;
+ else if (buf_size_max < SIZE_MAX)
+ {
+ errno = ENAMETOOLONG;
+ return NULL;
+ }
+ else
+ break;
+ buf = (char *) alloc->allocate (buf_size);
+ }
+ while (buf);
+
+ if (alloc->die)
+ alloc->die (buf_size);
+ errno = ENOMEM;
+ return NULL;
+}