Minor tweaks to openp

* src/lread.c (openp): Move invariant code out of the loop
and thus avoid redundant calls to memcpy.  Adjust comments.

1 files changed, 14 insertions, 10 deletions

diff --git a/src/lread.c b/src/lread.c
index 5c47f78f8e4..ecd482793a9 100644
--- a/src/lread.c
+++ b/src/lread.c
@@ -1464,6 +1464,8 @@ openp (Lisp_Object path, Lisp_Object str, Lisp_Object suffixes,
 
   for (; CONSP (path); path = XCDR (path))
     {
+      ptrdiff_t baselen, prefixlen;
+
       filename = Fexpand_file_name (str, XCAR (path));
       if (!complete_filename_p (filename))
         /* If there are non-absolute elts in PATH (eg ".").  */
@@ -1485,6 +1487,14 @@ openp (Lisp_Object path, Lisp_Object str, Lisp_Object suffixes,
           fn = SAFE_ALLOCA (fn_size);
         }
 
+      /* Copy FILENAME's data to FN but remove starting /: if any.  */
+      prefixlen = ((SCHARS (filename) > 2
+                    && SREF (filename, 0) == '/'
+                    && SREF (filename, 1) == ':')
+                   ? 2 : 0);
+      baselen = SBYTES (filename) - prefixlen;
+      memcpy (fn, SDATA (filename) + prefixlen, baselen);
+
       /* Loop over suffixes.  */
       for (tail = NILP (suffixes) ? list1 (empty_unibyte_string) : suffixes;
            CONSP (tail); tail = XCDR (tail))
@@ -1493,16 +1503,10 @@ openp (Lisp_Object path, Lisp_Object str, Lisp_Object suffixes,
           ptrdiff_t fnlen, lsuffix = SBYTES (suffix);
           Lisp_Object handler;
 
-          /* Concatenate path element/specified name with the suffix.
-             If the directory starts with /:, remove that.  */
-          int prefixlen = ((SCHARS (filename) > 2
-                            && SREF (filename, 0) == '/'
-                            && SREF (filename, 1) == ':')
-                           ? 2 : 0);
-          fnlen = SBYTES (filename) - prefixlen;
-          memcpy (fn, SDATA (filename) + prefixlen, fnlen);
-          memcpy (fn + fnlen, SDATA (suffix), lsuffix + 1);
-          fnlen += lsuffix;
+          /* Make complete filename by appending SUFFIX.  */
+          memcpy (fn + baselen, SDATA (suffix), lsuffix + 1);
+          fnlen = baselen + lsuffix;
+
           /* Check that the file exists and is not a directory.  */
           /* We used to only check for handlers on non-absolute file names:
                 if (absolute)