8 files changed, 180 insertions, 114 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 5c13e35306d..2156d7f19c9 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,34 @@
+2013-02-01  Paul Eggert  <eggert@cs.ucla.edu>
+
+        Use fdopendir, fstatat and readlinkat, for efficiency (Bug#13539).
+        * conf_post.h (GNULIB_SUPPORT_ONLY_AT_FDCWD): Remove.
+        * dired.c: Include <fcntl.h>.
+        (open_directory): New function, which uses open and fdopendir
+        rather than opendir.  DOS_NT platforms still use opendir, though.
+        (directory_files_internal, file_name_completion): Use it.
+        (file_attributes): New function, with most of the old Ffile_attributes.
+        (directory_files_internal, Ffile_attributes): Use it.
+        (file_attributes, file_name_completion_stat): First arg is now fd,
+        not dir name.  All uses changed.  Use fstatat rather than lstat +
+        stat.
+        (file_attributes): Use emacs_readlinkat rather than Ffile_symlink_p.
+        * fileio.c: Include <allocator.h>, <careadlinkat.h>.
+        (emacs_readlinkat): New function, with much of the old
+        Ffile_symlink_p, but with an fd argument for speed.
+        It uses readlinkat rather than careadlinkatcwd, so that it
+        need not assume the working directory.
+        (Ffile_symlink_p): Use it.
+        * filelock.c (current_lock_owner): Use emacs_readlinkat
+        rather than emacs_readlink.
+        * lisp.h (emacs_readlinkat): New decl.
+        (READLINK_BUFSIZE, emacs_readlink): Remove.
+        * sysdep.c: Do not include <allocator.h>, <careadlinkat.h>.
+        (emacs_norealloc_allocator, emacs_readlink): Remove.
+        This stuff is moved to fileio.c.
+        * w32.c (fstatat, readlinkat): New functions.
+        (careadlinkat): Don't check that fd == AT_FDCWD.
+        (careadlinkatcwd): Remove; no longer needed.
+
 2013-01-31  Glenn Morris  <rgm@gnu.org>
 
         * fileio.c (choose_write_coding_system): Make it callable from Lisp.
diff --git a/src/conf_post.h b/src/conf_post.h
index cd1e35bea7a..6c9747a436c 100644
--- a/src/conf_post.h
+++ b/src/conf_post.h
@@ -182,10 +182,6 @@ extern void _DebPrint (const char *fmt, ...);
 #endif
 #endif
 
-/* Tell gnulib to omit support for openat-related functions having a
-   first argument other than AT_FDCWD.  */
-#define GNULIB_SUPPORT_ONLY_AT_FDCWD
-
 #include <string.h>
 #include <stdlib.h>
 
diff --git a/src/dired.c b/src/dired.c
index a4c8621e9c0..ed0571fe9fe 100644
--- a/src/dired.c
+++ b/src/dired.c
@@ -30,6 +30,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <grp.h>
 
 #include <errno.h>
+#include <fcntl.h>
 #include <unistd.h>
 
 #include <dirent.h>
@@ -54,6 +55,7 @@ static Lisp_Object Qfile_attributes;
 static Lisp_Object Qfile_attributes_lessp;
 
 static ptrdiff_t scmp (const char *, const char *, ptrdiff_t);
+static Lisp_Object file_attributes (int, char const *, Lisp_Object);
 
 /* Return the number of bytes in DP's name.  */
 static ptrdiff_t
@@ -66,6 +68,44 @@ dirent_namelen (struct dirent *dp)
 #endif
 }
 
+static DIR *
+open_directory (char const *name, int *fdp)
+{
+  DIR *d;
+  int fd, opendir_errno;
+
+  block_input ();
+
+#ifdef DOS_NT
+  /* Directories cannot be opened.  The emulation assumes that any
+     file descriptor other than AT_FDCWD corresponds to the most
+     recently opened directory.  This hack is good enough for Emacs.  */
+  fd = 0;
+  d = opendir (name);
+  opendir_errno = errno;
+#else
+  fd = emacs_open (name, O_RDONLY | O_DIRECTORY, 0);
+  if (fd < 0)
+    {
+      opendir_errno = errno;
+      d = 0;
+    }
+  else
+    {
+      d = fdopendir (fd);
+      opendir_errno = errno;
+      if (! d)
+        close (fd);
+    }
+#endif
+
+  unblock_input ();
+
+  *fdp = fd;
+  errno = opendir_errno;
+  return d;
+}
+
 #ifdef WINDOWSNT
 Lisp_Object
 directory_files_internal_w32_unwind (Lisp_Object arg)
@@ -96,6 +136,7 @@ directory_files_internal (Lisp_Object directory, Lisp_Object full,
                           Lisp_Object id_format)
 {
   DIR *d;
+  int fd;
   ptrdiff_t directory_nbytes;
   Lisp_Object list, dirfilename, encoded_directory;
   struct re_pattern_buffer *bufp = NULL;
@@ -142,9 +183,7 @@ directory_files_internal (Lisp_Object directory, Lisp_Object full,
   /* Now *bufp is the compiled form of MATCH; don't call anything
      which might compile a new regexp until we're done with the loop!  */
 
-  block_input ();
-  d = opendir (SSDATA (dirfilename));
-  unblock_input ();
+  d = open_directory (SSDATA (dirfilename), &fd);
   if (d == NULL)
     report_file_error ("Opening directory", Fcons (directory, Qnil));
 
@@ -259,20 +298,9 @@ directory_files_internal (Lisp_Object directory, Lisp_Object full,
 
           if (attrs)
             {
-              /* Construct an expanded filename for the directory entry.
-                 Use the decoded names for input to Ffile_attributes.  */
-              Lisp_Object decoded_fullname, fileattrs;
-              struct gcpro gcpro1, gcpro2;
-
-              decoded_fullname = fileattrs = Qnil;
-              GCPRO2 (decoded_fullname, fileattrs);
-
-              /* Both Fexpand_file_name and Ffile_attributes can GC.  */
-              decoded_fullname = Fexpand_file_name (name, directory);
-              fileattrs = Ffile_attributes (decoded_fullname, id_format);
-
+              Lisp_Object fileattrs
+                = file_attributes (fd, dp->d_name, id_format);
               list = Fcons (Fcons (finalname, fileattrs), list);
-              UNGCPRO;
             }
           else
             list = Fcons (finalname, list);
@@ -413,8 +441,7 @@ These are all file names in directory DIRECTORY which begin with FILE.  */)
   return file_name_completion (file, directory, 1, Qnil);
 }
 
-static int file_name_completion_stat (Lisp_Object dirname, struct dirent *dp,
-                                      struct stat *st_addr);
+static int file_name_completion_stat (int, struct dirent *, struct stat *);
 static Lisp_Object Qdefault_directory;
 
 static Lisp_Object
@@ -422,6 +449,7 @@ file_name_completion (Lisp_Object file, Lisp_Object dirname, bool all_flag,
                       Lisp_Object predicate)
 {
   DIR *d;
+  int fd;
   ptrdiff_t bestmatchsize = 0;
   int matchcount = 0;
   /* If ALL_FLAG is 1, BESTMATCH is the list of all matches, decoded.
@@ -458,9 +486,7 @@ file_name_completion (Lisp_Object file, Lisp_Object dirname, bool all_flag,
 
   encoded_dir = ENCODE_FILE (dirname);
 
-  block_input ();
-  d = opendir (SSDATA (Fdirectory_file_name (encoded_dir)));
-  unblock_input ();
+  d = open_directory (SSDATA (Fdirectory_file_name (encoded_dir)), &fd);
   if (!d)
     report_file_error ("Opening directory", Fcons (dirname, Qnil));
 
@@ -495,7 +521,7 @@ file_name_completion (Lisp_Object file, Lisp_Object dirname, bool all_flag,
                         SCHARS (encoded_file)))
         continue;
 
-      if (file_name_completion_stat (encoded_dir, dp, &st) < 0)
+      if (file_name_completion_stat (fd, dp, &st) < 0)
         continue;
 
       directoryp = S_ISDIR (st.st_mode) != 0;
@@ -772,14 +798,9 @@ scmp (const char *s1, const char *s2, ptrdiff_t len)
 }
 
 static int
-file_name_completion_stat (Lisp_Object dirname, struct dirent *dp,
-                           struct stat *st_addr)
+file_name_completion_stat (int fd, struct dirent *dp, struct stat *st_addr)
 {
-  ptrdiff_t len = dirent_namelen (dp);
-  ptrdiff_t pos = SCHARS (dirname);
   int value;
-  USE_SAFE_ALLOCA;
-  char *fullname = SAFE_ALLOCA (len + pos + 2);
 
 #ifdef MSDOS
   /* Some fields of struct stat are *very* expensive to compute on MS-DOS,
@@ -792,23 +813,15 @@ file_name_completion_stat (Lisp_Object dirname, struct dirent *dp,
   _djstat_flags = _STAT_INODE | _STAT_EXEC_MAGIC | _STAT_DIRSIZE;
 #endif /* MSDOS */
 
-  memcpy (fullname, SDATA (dirname), pos);
-  if (!IS_DIRECTORY_SEP (fullname[pos - 1]))
-    fullname[pos++] = DIRECTORY_SEP;
-
-  memcpy (fullname + pos, dp->d_name, len);
-  fullname[pos + len] = 0;
-
   /* We want to return success if a link points to a nonexistent file,
      but we want to return the status for what the link points to,
      in case it is a directory.  */
-  value = lstat (fullname, st_addr);
+  value = fstatat (fd, dp->d_name, st_addr, AT_SYMLINK_NOFOLLOW);
   if (value == 0 && S_ISLNK (st_addr->st_mode))
-    stat (fullname, st_addr);
+    fstatat (fd, dp->d_name, st_addr, 0);
 #ifdef MSDOS
   _djstat_flags = save_djstat_flags;
 #endif /* MSDOS */
-  SAFE_FREE ();
   return value;
 }
 
@@ -886,18 +899,8 @@ On some FAT-based filesystems, only the date of last access is recorded,
 so last access time will always be midnight of that day.  */)
   (Lisp_Object filename, Lisp_Object id_format)
 {
-  Lisp_Object values[12];
   Lisp_Object encoded;
-  struct stat s;
-  int lstat_result;
-
-  /* An array to hold the mode string generated by filemodestring,
-     including its terminating space and null byte.  */
-  char modes[sizeof "-rwxr-xr-x "];
-
   Lisp_Object handler;
-  struct gcpro gcpro1;
-  char *uname = NULL, *gname = NULL;
 
   filename = Fexpand_file_name (filename, Qnil);
 
@@ -913,9 +916,22 @@ so last access time will always be midnight of that day.  */)
         return call3 (handler, Qfile_attributes, filename, id_format);
     }
 
-  GCPRO1 (filename);
   encoded = ENCODE_FILE (filename);
-  UNGCPRO;
+  return file_attributes (AT_FDCWD, SSDATA (encoded), id_format);
+}
+
+static Lisp_Object
+file_attributes (int fd, char const *name, Lisp_Object id_format)
+{
+  Lisp_Object values[12];
+  struct stat s;
+  int lstat_result;
+
+  /* An array to hold the mode string generated by filemodestring,
+     including its terminating space and null byte.  */
+  char modes[sizeof "-rwxr-xr-x "];
+
+  char *uname = NULL, *gname = NULL;
 
 #ifdef WINDOWSNT
   /* We usually don't request accurate owner and group info, because
@@ -925,7 +941,7 @@ so last access time will always be midnight of that day.  */)
   w32_stat_get_owner_group = 1;
 #endif
 
-  lstat_result = lstat (SSDATA (encoded), &s);
+  lstat_result = fstatat (fd, name, &s, AT_SYMLINK_NOFOLLOW);
 
 #ifdef WINDOWSNT
   w32_stat_get_owner_group = 0;
@@ -934,7 +950,7 @@ so last access time will always be midnight of that day.  */)
   if (lstat_result < 0)
     return Qnil;
 
-  values[0] = (S_ISLNK (s.st_mode) ? Ffile_symlink_p (filename)
+  values[0] = (S_ISLNK (s.st_mode) ? emacs_readlinkat (fd, name)
                : S_ISDIR (s.st_mode) ? Qt : Qnil);
   values[1] = make_number (s.st_nlink);
 
diff --git a/src/fileio.c b/src/fileio.c
index cd4bd4fa86e..a8218fcd797 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -82,6 +82,8 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #endif
 
 #include "systime.h"
+#include <allocator.h>
+#include <careadlinkat.h>
 #include <stat-time.h>
 
 #ifdef HPUX
@@ -2759,6 +2761,29 @@ If there is no error, returns nil.  */)
   return Qnil;
 }
 
+/* Relative to directory FD, return the symbolic link value of FILENAME.
+   On failure, return nil.  */
+Lisp_Object
+emacs_readlinkat (int fd, char const *filename)
+{
+  static struct allocator const emacs_norealloc_allocator =
+    { xmalloc, NULL, xfree, memory_full };
+  Lisp_Object val;
+  char readlink_buf[1024];
+  char *buf = careadlinkat (fd, filename, readlink_buf, sizeof readlink_buf,
+                            &emacs_norealloc_allocator, readlinkat);
+  if (!buf)
+    return Qnil;
+
+  val = build_string (buf);
+  if (buf[0] == '/' && strchr (buf, ':'))
+    val = concat2 (build_string ("/:"), val);
+  if (buf != readlink_buf)
+    xfree (buf);
+  val = DECODE_FILE (val);
+  return val;
+}
+
 DEFUN ("file-symlink-p", Ffile_symlink_p, Sfile_symlink_p, 1, 1, 0,
        doc: /* Return non-nil if file FILENAME is the name of a symbolic link.
 The value is the link target, as a string.
@@ -2769,9 +2794,6 @@ points to a nonexistent file.  */)
   (Lisp_Object filename)
 {
   Lisp_Object handler;
-  char *buf;
-  Lisp_Object val;
-  char readlink_buf[READLINK_BUFSIZE];
 
   CHECK_STRING (filename);
   filename = Fexpand_file_name (filename, Qnil);
@@ -2784,17 +2806,7 @@ points to a nonexistent file.  */)
 
   filename = ENCODE_FILE (filename);
 
-  buf = emacs_readlink (SSDATA (filename), readlink_buf);
-  if (! buf)
-    return Qnil;
-
-  val = build_string (buf);
-  if (buf[0] == '/' && strchr (buf, ':'))
-    val = concat2 (build_string ("/:"), val);
-  if (buf != readlink_buf)
-    xfree (buf);
-  val = DECODE_FILE (val);
-  return val;
+  return emacs_readlinkat (AT_FDCWD, SSDATA (filename));
 }
 
 DEFUN ("file-directory-p", Ffile_directory_p, Sfile_directory_p, 1, 1, 0,
diff --git a/src/filelock.c b/src/filelock.c
index f21240f8340..228fe98e8c7 100644
--- a/src/filelock.c
+++ b/src/filelock.c
@@ -390,12 +390,14 @@ current_lock_owner (lock_info_type *owner, char *lfname)
   lock_info_type local_owner;
   intmax_t n;
   char *at, *dot, *colon;
-  char readlink_buf[READLINK_BUFSIZE];
-  char *lfinfo = emacs_readlink (lfname, readlink_buf);
+  Lisp_Object lfinfo_object = emacs_readlinkat (AT_FDCWD, lfname);
+  char *lfinfo;
+  struct gcpro gcpro1;
 
   /* If nonexistent lock file, all is well; otherwise, got strange error. */
-  if (!lfinfo)
+  if (NILP (lfinfo_object))
     return errno == ENOENT ? 0 : -1;
+  lfinfo = SSDATA (lfinfo_object);
 
   /* Even if the caller doesn't want the owner info, we still have to
      read it to determine return value.  */
@@ -407,12 +409,9 @@ current_lock_owner (lock_info_type *owner, char *lfname)
   at = strrchr (lfinfo, '@');
   dot = strrchr (lfinfo, '.');
   if (!at || !dot)
-    {
-      if (lfinfo != readlink_buf)
-        xfree (lfinfo);
-      return -1;
-    }
+    return -1;
   len = at - lfinfo;
+  GCPRO1 (lfinfo_object);
   owner->user = xmalloc (len + 1);
   memcpy (owner->user, lfinfo, len);
   owner->user[len] = 0;
@@ -445,8 +444,7 @@ current_lock_owner (lock_info_type *owner, char *lfname)
   owner->host[len] = 0;
 
   /* We're done looking at the link info.  */
-  if (lfinfo != readlink_buf)
-    xfree (lfinfo);
+  UNGCPRO;
 
   /* On current host?  */
   if (STRINGP (Fsystem_name ())
diff --git a/src/lisp.h b/src/lisp.h
index 2e9088f1834..251b5e069ec 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -3294,6 +3294,7 @@ extern Lisp_Object close_file_unwind (Lisp_Object);
 extern Lisp_Object restore_point_unwind (Lisp_Object);
 extern _Noreturn void report_file_error (const char *, Lisp_Object);
 extern bool internal_delete_file (Lisp_Object);
+extern Lisp_Object emacs_readlinkat (int, const char *);
 extern bool file_directory_p (const char *);
 extern bool file_accessible_directory_p (const char *);
 extern void init_fileio (void);
@@ -3566,8 +3567,6 @@ extern int emacs_open (const char *, int, int);
 extern int emacs_close (int);
 extern ptrdiff_t emacs_read (int, char *, ptrdiff_t);
 extern ptrdiff_t emacs_write (int, const char *, ptrdiff_t);
-enum { READLINK_BUFSIZE = 1024 };
-extern char *emacs_readlink (const char *, char [READLINK_BUFSIZE]);
 
 extern void unlock_all_files (void);
 extern void lock_file (Lisp_Object);
diff --git a/src/sysdep.c b/src/sysdep.c
index 0e9a6826005..57ca8265a65 100644
--- a/src/sysdep.c
+++ b/src/sysdep.c
@@ -30,9 +30,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <limits.h>
 #include <unistd.h>
 
-#include <allocator.h>
 #include <c-ctype.h>
-#include <careadlinkat.h>
 #include <ignore-value.h>
 #include <utimens.h>
 
@@ -2247,22 +2245,6 @@ emacs_write (int fildes, const char *buf, ptrdiff_t nbyte)
 
   return (bytes_written);
 }
-
-static struct allocator const emacs_norealloc_allocator =
-  { xmalloc, NULL, xfree, memory_full };
-
-/* Get the symbolic link value of FILENAME.  Return a pointer to a
-   NUL-terminated string.  If readlink fails, return NULL and set
-   errno.  If the value fits in INITIAL_BUF, return INITIAL_BUF.
-   Otherwise, allocate memory and return a pointer to that memory.  If
-   memory allocation fails, diagnose and fail without returning.  If
-   successful, store the length of the symbolic link into *LINKLEN.  */
-char *
-emacs_readlink (char const *filename, char initial_buf[READLINK_BUFSIZE])
-{
-  return careadlinkat (AT_FDCWD, filename, initial_buf, READLINK_BUFSIZE,
-                       &emacs_norealloc_allocator, careadlinkatcwd);
-}
 
 /* Return a struct timeval that is roughly equivalent to T.
    Use the least timeval not less than T.
diff --git a/src/w32.c b/src/w32.c
index d0af53889e7..64f8a0335ac 100644
--- a/src/w32.c
+++ b/src/w32.c
@@ -4274,6 +4274,30 @@ lstat (const char * path, struct stat * buf)
   return stat_worker (path, buf, 0);
 }
 
+int
+fstatat (int fd, char const *name, struct stat *st, int flags)
+{
+  /* Rely on a hack: an open directory is modeled as file descriptor 0.
+     This is good enough for the current usage in Emacs, but is fragile.
+
+     FIXME: Add proper support for fdopendir, fstatatat, readlinkat.
+     Gnulib does this and can serve as a model.  */
+  char fullname[MAX_PATH];
+
+  if (fd != AT_FDCWD)
+    {
+      if (_snprintf (fullname, sizeof fullname, "%s/%s", dir_pathname, name)
+          < 0)
+        {
+          errno = ENAMETOOLONG;
+          return -1;
+        }
+      name = fullname;
+    }
+
+  return stat_worker (name, st, ! (flags & AT_SYMLINK_NOFOLLOW));
+}
+
 /* Provide fstat and utime as well as stat for consistent handling of
    file timestamps. */
 int
@@ -4816,6 +4840,28 @@ readlink (const char *name, char *buf, size_t buf_size)
   return retval;
 }
 
+ssize_t
+readlinkat (int fd, char const *name, char *buffer,
+            size_t buffer_size)
+{
+  /* Rely on a hack: an open directory is modeled as file descriptor 0,
+     as in fstatat.  FIXME: Add proper support for readlinkat.  */
+  char fullname[MAX_PATH];
+
+  if (fd != AT_FDCWD)
+    {
+      if (_snprintf (fullname, sizeof fullname, "%s/%s", dir_pathname, name)
+          < 0)
+        {
+          errno = ENAMETOOLONG;
+          return -1;
+        }
+      name = fullname;
+    }
+
+  return readlink (name, buffer, buffer_size);
+}
+
 /* If FILE is a symlink, return its target (stored in a static
    buffer); otherwise return FILE.
 
@@ -5168,12 +5214,6 @@ careadlinkat (int fd, char const *filename,
   char linkname[MAX_PATH];
   ssize_t link_size;
 
-  if (fd != AT_FDCWD)
-    {
-      errno = EINVAL;
-      return NULL;
-    }
-
   link_size = preadlinkat (fd, filename, linkname, sizeof(linkname));
 
   if (link_size > 0)
@@ -5191,14 +5231,6 @@ careadlinkat (int fd, char const *filename,
   return NULL;
 }
 
-ssize_t
-careadlinkatcwd (int fd, char const *filename, char *buffer,
-                 size_t buffer_size)
-{
-  (void) fd;
-  return readlink (filename, buffer, buffer_size);
-}
-
 
 /* Support for browsing other processes and their attributes.  See
    process.c for the Lisp bindings.  */