* modules/areadlinkat-with-size: New module.
* lib/areadlinkat-with-size.c (areadlinkat_with_size): New file.
* lib/areadlink.h (areadlinkat): Declare it.
* MODULES.html.sh (File system functions): Mention it.
* modules/areadlinkat-with-size-tests: New test.
* tests/test-areadlinkat-with-size.c: New file.
Signed-off-by: Eric Blake <ebb9@byu.net>
2009-10-07 Eric Blake <ebb9@byu.net>
+ areadlinkat-with-size: new module
+ * modules/areadlinkat-with-size: New module.
+ * lib/areadlinkat-with-size.c (areadlinkat_with_size): New file.
+ * lib/areadlink.h (areadlinkat): Declare it.
+ * MODULES.html.sh (File system functions): Mention it.
+ * modules/areadlinkat-with-size-tests: New test.
+ * tests/test-areadlinkat-with-size.c: New file.
+
xreadlinkat: new module
* modules/xreadlinkat: New module.
* lib/xreadlinkat.c (xreadlinkat): New file.
func_module areadlink
func_module areadlink-with-size
func_module areadlinkat
+ func_module areadlinkat-with-size
func_module backupfile
func_module canonicalize
func_module canonicalize-lgpl
#if GNULIB_AREADLINKAT
extern char *areadlinkat (int fd, char const *filename);
#endif
+
+#if GNULIB_AREADLINKAT_WITH_SIZE
+extern char *areadlinkat_with_size (int fd, char const *filename,
+ size_t size_hint);
+#endif
--- /dev/null
+/* readlinkat wrapper to return the link name in malloc'd storage.
+ Unlike xreadlinkat, only call exit on failure to change directory.
+
+ Copyright (C) 2001, 2003-2007, 2009 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 Jim Meyering <jim@meyering.net>
+ and Eric Blake <ebb9@byu.net>. */
+
+#include <config.h>
+
+#include "areadlink.h"
+
+#include <stdio.h>
+#include <errno.h>
+#include <limits.h>
+#include <sys/types.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#if HAVE_READLINKAT
+
+# ifndef SSIZE_MAX
+# define SSIZE_MAX ((ssize_t) (SIZE_MAX / 2))
+# endif
+
+/* SYMLINK_MAX is used only for an initial memory-allocation sanity
+ check, so it's OK to guess too small on hosts where there is no
+ arbitrary limit to symbolic link length. */
+# ifndef SYMLINK_MAX
+# define SYMLINK_MAX 1024
+# endif
+
+# define MAXSIZE (SIZE_MAX < SSIZE_MAX ? SIZE_MAX : SSIZE_MAX)
+
+/* Call readlinkat to get the symbolic link value of FILE, relative to FD.
+ SIZE is a hint as to how long the link is expected to be;
+ typically it is taken from st_size. It need not be correct.
+ Return a pointer to that NUL-terminated string in malloc'd storage.
+ If readlinkat fails, malloc fails, or if the link value is longer
+ than SSIZE_MAX, return NULL (caller may use errno to diagnose).
+ However, failure to change directory during readlinkat will issue
+ a diagnostic and exit. */
+
+char *
+areadlinkat_with_size (int fd, char const *file, size_t size)
+{
+ /* Some buggy file systems report garbage in st_size. Defend
+ against them by ignoring outlandish st_size values in the initial
+ memory allocation. */
+ size_t symlink_max = SYMLINK_MAX;
+ size_t INITIAL_LIMIT_BOUND = 8 * 1024;
+ size_t initial_limit = (symlink_max < INITIAL_LIMIT_BOUND
+ ? symlink_max + 1
+ : INITIAL_LIMIT_BOUND);
+
+ /* The initial buffer size for the link value. */
+ size_t buf_size = size < initial_limit ? size + 1 : initial_limit;
+
+ while (1)
+ {
+ ssize_t r;
+ size_t link_length;
+ char *buffer = malloc (buf_size);
+
+ if (buffer == NULL)
+ return NULL;
+ r = readlinkat (fd, file, buffer, buf_size);
+ link_length = r;
+
+ /* 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 (r < 0 && errno != ERANGE)
+ {
+ int saved_errno = errno;
+ free (buffer);
+ errno = saved_errno;
+ return NULL;
+ }
+
+ if (link_length < buf_size)
+ {
+ buffer[link_length] = 0;
+ return buffer;
+ }
+
+ free (buffer);
+ if (buf_size <= MAXSIZE / 2)
+ buf_size *= 2;
+ else if (buf_size < MAXSIZE)
+ buf_size = MAXSIZE;
+ else
+ {
+ errno = ENOMEM;
+ return NULL;
+ }
+ }
+}
+
+#else /* !HAVE_READLINKAT */
+
+
+/* It is more efficient to change directories only once and call
+ areadlink_with_size, rather than repeatedly call the replacement
+ readlinkat. */
+
+# define AT_FUNC_NAME areadlinkat_with_size
+# define AT_FUNC_F1 areadlink_with_size
+# define AT_FUNC_POST_FILE_PARAM_DECLS , size_t size
+# define AT_FUNC_POST_FILE_ARGS , size
+# define AT_FUNC_RESULT char *
+# define AT_FUNC_FAIL NULL
+# include "at-func.c"
+# undef AT_FUNC_NAME
+# undef AT_FUNC_F1
+# undef AT_FUNC_POST_FILE_PARAM_DECLS
+# undef AT_FUNC_POST_FILE_ARGS
+# undef AT_FUNC_RESULT
+# undef AT_FUNC_FAIL
+
+#endif /* !HAVE_READLINKAT */
--- /dev/null
+Description:
+Read a symbolic link, without size limitations, relative to fd.
+
+Files:
+lib/areadlink.h
+lib/areadlinkat-with-size.c
+
+Depends-on:
+areadlink-with-size
+stdint
+symlinkat
+
+configure.ac:
+gl_MODULE_INDICATOR([areadlinkat-with-size])
+
+Makefile.am:
+lib_SOURCES += areadlinkat-with-size.c
+
+Include:
+"areadlink.h"
+
+License:
+GPL
+
+Maintainer:
+Jim Meyering, Eric Blake
--- /dev/null
+Files:
+tests/test-areadlink.h
+tests/test-areadlinkat-with-size.c
+
+Depends-on:
+stdbool
+
+configure.ac:
+
+Makefile.am:
+TESTS += test-areadlinkat-with-size
+check_PROGRAMS += test-areadlinkat-with-size
+test_areadlinkat_with_size_LDADD = $(LDADD) @LIBINTL@
--- /dev/null
+/* Tests of areadlinkat_with_size.
+ Copyright (C) 2009 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 Eric Blake <ebb9@byu.net>, 2009. */
+
+#include <config.h>
+
+#include "areadlink.h"
+
+#include <fcntl.h>
+#include <errno.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#define ASSERT(expr) \
+ do \
+ { \
+ if (!(expr)) \
+ { \
+ fprintf (stderr, "%s:%d: assertion failed\n", __FILE__, __LINE__); \
+ fflush (stderr); \
+ abort (); \
+ } \
+ } \
+ while (0)
+
+#define BASE "test-areadlinkat-with-size.t"
+
+#include "test-areadlink.h"
+
+static int dfd = AT_FDCWD;
+
+/* Wrapper for testing areadlinkat_with_size. */
+static char *
+do_areadlinkat_with_size (char const *name, size_t size)
+{
+ return areadlinkat_with_size (dfd, name, size);
+}
+
+int
+main ()
+{
+ int result;
+
+ /* Remove any leftovers from a previous partial run. */
+ ASSERT (system ("rm -rf " BASE "*") == 0);
+
+ /* Basic tests. */
+ result = test_areadlink (do_areadlinkat_with_size, false);
+ dfd = open (".", O_RDONLY);
+ ASSERT (0 <= dfd);
+ ASSERT (test_areadlink (do_areadlinkat_with_size, false) == result);
+
+ /* Relative tests. */
+ if (result == 77)
+ fputs ("skipping test: symlinks not supported on this filesystem\n",
+ stderr);
+ else
+ {
+ char *buf;
+ ASSERT (symlink ("nowhere", BASE "link") == 0);
+ ASSERT (mkdir (BASE "dir", 0700) == 0);
+ ASSERT (chdir (BASE "dir") == 0);
+ buf = areadlinkat_with_size (dfd, BASE "link", strlen (BASE "link"));
+ ASSERT (buf);
+ ASSERT (strcmp (buf, "nowhere") == 0);
+ free (buf);
+ errno = 0;
+ ASSERT (areadlinkat_with_size (-1, BASE "link", 1) == NULL);
+ ASSERT (errno == EBADF);
+ errno = 0;
+ ASSERT (areadlinkat_with_size (AT_FDCWD, BASE "link", 1) == NULL);
+ ASSERT (errno == ENOENT);
+ ASSERT (chdir ("..") == 0);
+ ASSERT (rmdir (BASE "dir") == 0);
+ ASSERT (unlink (BASE "link") == 0);
+ }
+
+ ASSERT (close (dfd) == 0);
+ return result;
+}
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