filenamecat: split into filenamecat-lgpl

The concept of filenamecat is simple enough to use in an LGPL
manner, even though current clients are GPL for other reasons.
At any rate, it is nice to separate mfile_name_concat into its
own file so that the linker does not fail without xalloc_die.

* modules/filenamecat-lgpl: New module.
* modules/filenamecat (Files): Move library-safe files into
filenamecat-lgpl.
(Depends-on): Add filenamecat-lgpl.
(configure.ac): Declare witness.
* lib/filenamecat.h (file_name_concat): Only declare when using
GPL module.
* lib/filenamecat.c (longest_relative_suffix, mfile_name_concat):
Move...
* lib/filenamecat-lgpl.c: ...into new file.
* m4/filenamecat.m4 (gl_FILE_NAME_CONCAT_LGPL): New macro.
(gl_FILE_NAME_CONCAT): Use it.
* MODULES.html.sh (File system functions): Mention new module.

Signed-off-by: Eric Blake <ebb9@byu.net>

1 files changed, 88 insertions, 0 deletions

diff --git a/lib/filenamecat-lgpl.c b/lib/filenamecat-lgpl.c
new file mode 100644
index 0000000000..b22f0f7845
--- /dev/null
+++ b/lib/filenamecat-lgpl.c
@@ -0,0 +1,88 @@
+/* Concatenate two arbitrary file names.
+
+   Copyright (C) 1996-2007, 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.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include "filenamecat.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+#include "dirname.h"
+
+#if ! HAVE_MEMPCPY && ! defined mempcpy
+# define mempcpy(D, S, N) ((void *) ((char *) memcpy (D, S, N) + (N)))
+#endif
+
+/* Return the longest suffix of F that is a relative file name.
+   If it has no such suffix, return the empty string.  */
+
+static char const *
+longest_relative_suffix (char const *f)
+{
+  for (f += FILE_SYSTEM_PREFIX_LEN (f); ISSLASH (*f); f++)
+    continue;
+  return f;
+}
+
+/* Concatenate two file name components, DIR and ABASE, in
+   newly-allocated storage and return the result.
+   The resulting file name F is such that the commands "ls F" and "(cd
+   DIR; ls BASE)" refer to the same file, where BASE is ABASE with any
+   file system prefixes and leading separators removed.
+   Arrange for a directory separator if necessary between DIR and BASE
+   in the result, removing any redundant separators.
+   In any case, if BASE_IN_RESULT is non-NULL, set
+   *BASE_IN_RESULT to point to the copy of ABASE in the returned
+   concatenation.  However, if ABASE begins with more than one slash,
+   set *BASE_IN_RESULT to point to the sole corresponding slash that
+   is copied into the result buffer.
+
+   Return NULL if malloc fails.  */
+
+char *
+mfile_name_concat (char const *dir, char const *abase, char **base_in_result)
+{
+  char const *dirbase = last_component (dir);
+  size_t dirbaselen = base_len (dirbase);
+  size_t dirlen = dirbase - dir + dirbaselen;
+  size_t needs_separator = (dirbaselen && ! ISSLASH (dirbase[dirbaselen - 1]));
+
+  char const *base = longest_relative_suffix (abase);
+  size_t baselen = strlen (base);
+
+  char *p_concat = malloc (dirlen + needs_separator + baselen + 1);
+  char *p;
+
+  if (p_concat == NULL)
+    return NULL;
+
+  p = mempcpy (p_concat, dir, dirlen);
+  *p = DIRECTORY_SEPARATOR;
+  p += needs_separator;
+
+  if (base_in_result)
+    *base_in_result = p - IS_ABSOLUTE_FILE_NAME (abase);
+
+  p = mempcpy (p, base, baselen);
+  *p = '\0';
+
+  return p_concat;
+}