cdio_follow_symlink -> cdio_realpath which is really POSIX realpath. (Suggestion via Thomas Schmitt.) gnu_linux.c: report errors when they occur.

2010-01-16 16:44:12 -05:00
parent 2103e77696
commit 7d8b6d0a4d
9 changed files with 51 additions and 40 deletions
--- a/lib/driver/realpath.c
+++ b/lib/driver/realpath.c
@@ -0,0 +1,140 @@
+/*
+  Copyright (C) 2010
+  Rocky Bernstein <rocky@gnu.org>
+  Diego 'Flameeyes' Pettenò 
+  Thomas Schmitt
+
+  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/>.
+*/
+/*
+  POSIX realpath if that's around, and something like it if not.
+
+  To compile as a standalone program:
+  gcc -Wall -g -I../.. -DHAVE_CONFIG_H -DSTANDALONE -o realpath realpath.c
+*/
+/*
+  Make sure we handle:
+  - resolve relative links like  /dev/cdrom -> sr2
+  - abort on cyclic linking like /dev/cdrom -> /dev/cdrom
+*/
+
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include <ctype.h>
+
+#ifdef HAVE_STDLIB_H
+# include <stdlib.h>
+#endif
+
+#include <stdio.h>
+
+#ifdef HAVE_STRING_H
+# include <string.h>
+#endif
+
+#ifdef HAVE_UNISTD_H // readlink
+# include <unistd.h>
+#endif
+
+
+#ifdef HAVE_INTTYPES_H
+# include "inttypes.h"
+#endif
+
+#ifdef HAVE_LIMITS_H
+# include <limits.h>
+#endif
+
+#ifndef PATH_MAX
+#define PATH_MAX 4096
+#endif
+
+#include <cdio/util.h>
+
+/*!  cdio_realpath() same as POSIX.1-2001 realpath if that's
+around. If not we do poor-man's simulation of that behavior.  */
+char *cdio_realpath (const char *psz_src_path, char *psz_resolved_path) {
+
+#ifdef HAVE_REALPATH
+  psz_resolved_path = realpath(psz_src_path, psz_resolved_path);
+
+#elif defined(HAVE_READLINK)
+  char tmp_src[PATH_MAX+1];
+  char tmp_dst[PATH_MAX+1];
+  char *p_adr;
+  int i, len;
+  const int loop_limit = 100;
+
+  strcpy(tmp_src, psz_src_path);
+
+  /* FIXME: 
+     remove loop and change with stat before and after readlink 
+     which looks direct symlink. Rely on errno to figure out other
+     non-existent or looped symlinks. 
+  */
+  for(i = 0; i < loop_limit; i++) {
+    len = readlink(tmp_src, tmp_dst, PATH_MAX);
+    if (-1 == len) {
+	/* Right now we expect a "not symlink" error. However after
+	   we put in the stat() suggested above, there won't be a symlink
+	   error and we should start reporting what the failure is.
+	*/
+	break;
+    } else {
+	tmp_dst[len] = '\0';
+	if (tmp_dst[0] != '/') {
+	    /* Take care of relative link like  /dev/cdrom -> sr2 */
+	    p_adr = strrchr(tmp_src, '/');
+	    if (p_adr != NULL) {
+		strncpy(p_adr + 1, tmp_dst, PATH_MAX - (p_adr + 1 - tmp_src));
+	    } else {
+		strncpy(tmp_src, tmp_dst, PATH_MAX);
+	    }
+	} else {
+	    strncpy(tmp_src, tmp_dst, PATH_MAX);
+	}
+	tmp_src[PATH_MAX - 1] = 0; /* strncpy() does not always set a 0 */
+    }
+  }
+  strncpy(psz_resolved_path, tmp_src, PATH_MAX);
+#else
+  strncpy(psz_resolved_path, psz_src_path, PATH_MAX);
+#endif
+
+  return psz_resolved_path;
+  
+}
+
+#ifdef STANDALONE
+int main(int argc, char **argv)
+{
+  int i;
+  char dest[PATH_MAX];
+
+  if (argc < 2) {
+    fprintf(stderr, "Usage: %s  path [path ...]\n", argv[0]);
+    fprintf(stderr,
+     "       Resolve symbolic links\n");
+    exit(1);
+  }
+  for (i= 1; i < argc; i++) {
+    dest[0] = 0;
+    cdio_realpath (argv[i], dest);
+    printf("%s -> %s\n", argv[i], dest);
+  }
+  exit(0);
+}
+#endif