Avoid extra calls to strlen in filesystem I/O routines.

* fileio.c (Fexpand_file_name): Avoid calls to strlen if
the length of 'newdir' is known or may be precalculated.
(file_accessible_directory_p): Prefer to pass Lisp_Object,
not 'char *', and so use precalculated length.
(Ffile_accessible_directory_p):
* callproc.c (encode_current_directory, init_callproc):
* charset.c (init_charset):
* lread.c (load_path_check, load_path_default): Adjust users.
* lisp.h (file_accessible_directory_p): Tweak prototype.

1 files changed, 32 insertions, 16 deletions

diff --git a/src/fileio.c b/src/fileio.c
index d9c7397c2de..d4929184cee 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -889,7 +889,7 @@ filesystem tree, not (expand-file-name ".."  dirname).  */)
   bool collapse_newdir = 1;
   bool is_escaped = 0;
 #endif /* DOS_NT */
-  ptrdiff_t length;
+  ptrdiff_t length, newdirlen;
   Lisp_Object handler, result, handled_name;
   bool multibyte;
   Lisp_Object hdir;
@@ -1147,6 +1147,7 @@ filesystem tree, not (expand-file-name ".."  dirname).  */)
      append it to the current working directory.  */
 
   newdir = 0;
+  newdirlen = -1;
 
   if (nm[0] == '~')             /* prefix ~ */
     {
@@ -1171,10 +1172,12 @@ filesystem tree, not (expand-file-name ".."  dirname).  */)
           else
 #endif
             tem = build_string (newdir);
+          newdirlen = SBYTES (tem);
           if (multibyte && !STRING_MULTIBYTE (tem))
             {
               hdir = DECODE_FILE (tem);
               newdir = SSDATA (hdir);
+              newdirlen = SBYTES (hdir);
             }
 #ifdef DOS_NT
           collapse_newdir = 0;
@@ -1201,10 +1204,12 @@ filesystem tree, not (expand-file-name ".."  dirname).  */)
                  bite us since we expect the directory to be
                  multibyte.  */
               tem = build_string (newdir);
+              newdirlen = SBYTES (tem);
               if (multibyte && !STRING_MULTIBYTE (tem))
                 {
                   hdir = DECODE_FILE (tem);
                   newdir = SSDATA (hdir);
+                  newdirlen = SBYTES (hdir);
                 }
               nm = p;
 #ifdef DOS_NT
@@ -1234,7 +1239,8 @@ filesystem tree, not (expand-file-name ".."  dirname).  */)
               Lisp_Object tem = build_string (adir);
 
               tem = DECODE_FILE (tem);
-              memcpy (adir, SSDATA (tem), SBYTES (tem) + 1);
+              newdirlen = SBYTES (tem);
+              memcpy (adir, SSDATA (tem), newdirlen + 1);
             }
         }
       if (!adir)
@@ -1245,6 +1251,7 @@ filesystem tree, not (expand-file-name ".."  dirname).  */)
           adir[1] = ':';
           adir[2] = '/';
           adir[3] = 0;
+          newdirlen = 3;
         }
       newdir = adir;
     }
@@ -1265,11 +1272,13 @@ filesystem tree, not (expand-file-name ".."  dirname).  */)
       && !newdir)
     {
       newdir = SSDATA (default_directory);
+      newdirlen = SBYTES (default_directory);
 #ifdef DOS_NT
       /* Note if special escape prefix is present, but remove for now.  */
       if (newdir[0] == '/' && newdir[1] == ':')
         {
           is_escaped = 1;
+          newdirlen -= 2;
           newdir += 2;
         }
 #endif
@@ -1305,14 +1314,14 @@ filesystem tree, not (expand-file-name ".."  dirname).  */)
           if (IS_DRIVE (newdir[0]) && IS_DEVICE_SEP (newdir[1]))
             {
               drive = (unsigned char) newdir[0];
+              newdirlen -= 2;
               newdir += 2;
             }
           if (!IS_DIRECTORY_SEP (nm[0]))
             {
-              ptrdiff_t newlen = strlen (newdir);
-              char *tmp = alloca (newlen + file_name_as_directory_slop
+              char *tmp = alloca (newdirlen + file_name_as_directory_slop
                                   + strlen (nm) + 1);
-              file_name_as_directory (tmp, newdir, newlen, multibyte);
+              file_name_as_directory (tmp, newdir, newdirlen, multibyte);
               strcat (tmp, nm);
               nm = tmp;
             }
@@ -1329,8 +1338,11 @@ filesystem tree, not (expand-file-name ".."  dirname).  */)
               Lisp_Object tem = build_string (adir);
 
               tem = DECODE_FILE (tem);
-              memcpy (adir, SSDATA (tem), SBYTES (tem) + 1);
+              newdirlen = SBYTES (tem);
+              memcpy (adir, SSDATA (tem), newdirlen + 1);
             }
+          else
+            newdirlen = strlen (aidr);
           newdir = adir;
         }
 
@@ -1338,6 +1350,7 @@ filesystem tree, not (expand-file-name ".."  dirname).  */)
       if (IS_DRIVE (newdir[0]) && IS_DEVICE_SEP (newdir[1]))
         {
           drive = newdir[0];
+          newdirlen -= 2;
           newdir += 2;
         }
 
@@ -1349,17 +1362,18 @@ filesystem tree, not (expand-file-name ".."  dirname).  */)
           if (IS_DIRECTORY_SEP (newdir[0]) && IS_DIRECTORY_SEP (newdir[1])
               && !IS_DIRECTORY_SEP (newdir[2]))
             {
-              char *adir = strcpy (alloca (strlen (newdir) + 1), newdir);
+              char *adir = strcpy (alloca (newdirlen + 1), newdir);
               char *p = adir + 2;
               while (*p && !IS_DIRECTORY_SEP (*p)) p++;
               p++;
               while (*p && !IS_DIRECTORY_SEP (*p)) p++;
               *p = 0;
               newdir = adir;
+              newdirlen = strlen (adir);
             }
           else
 #endif
-            newdir = "";
+            newdirlen = 0, newdir = "";
         }
     }
 #endif /* DOS_NT */
@@ -1368,7 +1382,8 @@ filesystem tree, not (expand-file-name ".."  dirname).  */)
     {
       /* Ignore any slash at the end of newdir, unless newdir is
          just "/" or "//".  */
-      length = strlen (newdir);
+      length = newdirlen;
+      eassert (length == strlen (newdir));
       while (length > 1 && IS_DIRECTORY_SEP (newdir[length - 1])
              && ! (length == 2 && IS_DIRECTORY_SEP (newdir[0])))
         length--;
@@ -2765,23 +2780,24 @@ searchable directory.  */)
     }
 
   absname = ENCODE_FILE (absname);
-  return file_accessible_directory_p (SSDATA (absname)) ? Qt : Qnil;
+  return file_accessible_directory_p (absname) ? Qt : Qnil;
 }
 
 /* If FILE is a searchable directory or a symlink to a
    searchable directory, return true.  Otherwise return
    false and set errno to an error number.  */
 bool
-file_accessible_directory_p (char const *file)
+file_accessible_directory_p (Lisp_Object file)
 {
 #ifdef DOS_NT
   /* There's no need to test whether FILE is searchable, as the
      searchable/executable bit is invented on DOS_NT platforms.  */
-  return file_directory_p (file);
+  return file_directory_p (SSDATA (file));
 #else
   /* On POSIXish platforms, use just one system call; this avoids a
      race and is typically faster.  */
-  ptrdiff_t len = strlen (file);
+  const char *data = SSDATA (file);
+  ptrdiff_t len = SBYTES (file);
   char const *dir;
   bool ok;
   int saved_errno;
@@ -2793,15 +2809,15 @@ file_accessible_directory_p (char const *file)
      "/" and "//" are distinct on some platforms, whereas "/", "///",
      "////", etc. are all equivalent.  */
   if (! len)
-    dir = file;
+    dir = data;
   else
     {
       /* Just check for trailing '/' when deciding whether to append '/'.
          That's simpler than testing the two special cases "/" and "//",
          and it's a safe optimization here.  */
       char *buf = SAFE_ALLOCA (len + 3);
-      memcpy (buf, file, len);
-      strcpy (buf + len, &"/."[file[len - 1] == '/']);
+      memcpy (buf, data, len);
+      strcpy (buf + len, &"/."[data[len - 1] == '/']);
       dir = buf;
     }