Speed up generate-new-buffer-name for invisible buffers (bug#1229)

* src/buffer.c (Fgenerate_new_buffer_name):
Speed up finding a new buffer for invisible buffers.

* src/lisp.h (Frandom): Make it visible to C.

3 files changed, 26 insertions, 3 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index e3993981317..805b189ae83 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,9 @@
+2012-07-03  Glenn Morris  <rgm@gnu.org>
+
+        * lisp.h (Frandom): Make it visible to C.
+        * buffer.c (Fgenerate_new_buffer_name): Speed up finding a new
+        buffer for invisible buffers.  (Bug#1229)
+
 2012-07-03  Dmitry Antipov  <dmantipov@yandex.ru>
 
         Fix block vector allocation code to allow VECTOR_BLOCK_SIZE
diff --git a/src/buffer.c b/src/buffer.c
index 08118baa3d7..83f0eb153c5 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -838,10 +838,14 @@ If there is no live buffer named NAME, then return NAME.
 Otherwise modify name by appending `<NUMBER>', incrementing NUMBER
 \(starting at 2) until an unused name is found, and then return that name.
 Optional second argument IGNORE specifies a name that is okay to use (if
-it is in the sequence to be tried) even if a buffer with that name exists.  */)
+it is in the sequence to be tried) even if a buffer with that name exists.
+
+If NAME begins with a space (i.e., a buffer that is not normally
+visible to users), then if buffer NAME already exists a random number
+is first appended to NAME, to speed up finding a non-existent buffer.  */)
   (register Lisp_Object name, Lisp_Object ignore)
 {
-  register Lisp_Object gentemp, tem;
+  register Lisp_Object gentemp, tem, tem2;
   ptrdiff_t count;
   char number[INT_BUFSIZE_BOUND (ptrdiff_t) + sizeof "<>"];
 
@@ -854,11 +858,23 @@ it is in the sequence to be tried) even if a buffer with that name exists.  */)
   if (NILP (tem))
     return name;
 
+  if (!strncmp (SSDATA (name), " ", 1)) /* see bug#1229 */
+    {
+      /* Note fileio.c:make_temp_name does random differently.  */
+      sprintf (number, "-%"pD"d", Frandom (make_number (999999)));
+      tem2 = concat2 (name, build_string (number));
+      tem = Fget_buffer (tem2);
+      if (NILP (tem))
+        return tem2;
+    }
+  else
+    tem2 = name;
+
   count = 1;
   while (1)
     {
       sprintf (number, "<%"pD"d>", ++count);
-      gentemp = concat2 (name, build_string (number));
+      gentemp = concat2 (tem2, build_string (number));
       tem = Fstring_equal (gentemp, ignore);
       if (!NILP (tem))
         return gentemp;
diff --git a/src/lisp.h b/src/lisp.h
index 8cec1600692..2059e2a3fbd 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -2473,6 +2473,7 @@ EXFUN (Fputhash, 3);
 EXFUN (Fremhash, 2);
 
 EXFUN (Fidentity, 1);
+EXFUN (Frandom, 1);
 EXFUN (Flength, 1);
 EXFUN (Fappend, MANY);
 EXFUN (Fconcat, MANY);