* lisp.h (make_gap_1): New prototype.

* buffer.h (GAP_BYTES_DFL, GAP_BYTES_MIN): New macros for the special
gap size values.
* editfns.c (Fbuffer_size): Rename from Fbufsize to fit the common
naming convention.
(syms_of_editfns): Adjust defsubr.  Drop commented-out obsolete code.
* insdel.c (make_gap_larger): Use GAP_BYTES_DFL.
(make_gap_smaller): Use GAP_BYTES_MIN.  Adjust comment.
(make_gap_1): New function to adjust the gap of any buffer.
* coding.c (coding_alloc_by_making_gap): Use it.
* buffer.c (compact_buffer): Likewise.  Use BUF_Z_BYTE, BUF_GAP_SIZE,
GAP_BYTES_DFL and GAP_BYTES_MIN.  Adjust comment.

src/ChangeLog

@@ -1,3 +1,18 @@
+2013-01-09  Dmitry Antipov  <dmantipov@yandex.ru>
+
+	* lisp.h (make_gap_1): New prototype.
+	* buffer.h (GAP_BYTES_DFL, GAP_BYTES_MIN): New macros for the special
+	gap size values.
+	* editfns.c (Fbuffer_size): Rename from Fbufsize to fit the common
+	naming convention.
+	(syms_of_editfns): Adjust defsubr.  Drop commented-out obsolete code.
+	* insdel.c (make_gap_larger): Use GAP_BYTES_DFL.
+	(make_gap_smaller): Use GAP_BYTES_MIN.  Adjust comment.
+	(make_gap_1): New function to adjust the gap of any buffer.
+	* coding.c (coding_alloc_by_making_gap): Use it.
+	* buffer.c (compact_buffer): Likewise.  Use BUF_Z_BYTE, BUF_GAP_SIZE,
+	GAP_BYTES_DFL and GAP_BYTES_MIN.  Adjust comment.
+
 2013-01-08  Juri Linkov  <juri@jurta.org>
 
 	* xfaces.c (tty_supports_face_attributes_p): Return 0 for the case

src/buffer.c

@@ -1682,17 +1682,13 @@ compact_buffer (struct buffer *buffer)
       if (!buffer->text->inhibit_shrinking)
 	{
 	  /* If a buffer's gap size is more than 10% of the buffer
-	     size, or larger than 2000 bytes, then shrink it
-	     accordingly.  Keep a minimum size of 20 bytes.  */
-	  int size = min (2000, max (20, (buffer->text->z_byte / 10)));
-
-	  if (buffer->text->gap_size > size)
-	    {
-	      struct buffer *save_current = current_buffer;
-	      current_buffer = buffer;
-	      make_gap (-(buffer->text->gap_size - size));
-	      current_buffer = save_current;
-	    }
+	     size, or larger than GAP_BYTES_DFL bytes, then shrink it
+	     accordingly.  Keep a minimum size of GAP_BYTES_MIN bytes.  */
+	  ptrdiff_t size = clip_to_bounds (GAP_BYTES_MIN,
+					   BUF_Z_BYTE (buffer) / 10,
+					   GAP_BYTES_DFL);
+	  if (BUF_GAP_SIZE (buffer) > size)
+	    make_gap_1 (buffer, -(BUF_GAP_SIZE (buffer) - size));
 	}
       BUF_COMPACT (buffer) = BUF_MODIFF (buffer);
     }

src/buffer.h

@@ -320,6 +320,16 @@ while (0)
 #define BUF_BYTES_MAX \
   (ptrdiff_t) min (MOST_POSITIVE_FIXNUM - 1, min (SIZE_MAX, PTRDIFF_MAX))
 
+/* Maximum gap size after compact_buffer, in bytes.  Also
+   used in make_gap_larger to get some extra reserved space.  */
+
+#define GAP_BYTES_DFL 2000
+
+/* Minimum gap size after compact_buffer, in bytes.  Also
+   used in make_gap_smaller to avoid too small gap size.  */
+
+#define GAP_BYTES_MIN 20
+
 /* Return the address of byte position N in current buffer.  */
 
 #define BYTE_POS_ADDR(n) \

src/coding.c

@@ -1049,14 +1049,7 @@ coding_alloc_by_making_gap (struct coding_system *coding,
       GPT -= gap_head_used, GPT_BYTE -= gap_head_used;
     }
   else
-    {
-      Lisp_Object this_buffer;
-
-      this_buffer = Fcurrent_buffer ();
-      set_buffer_internal (XBUFFER (coding->dst_object));
-      make_gap (bytes);
-      set_buffer_internal (XBUFFER (this_buffer));
-    }
+    make_gap_1 (XBUFFER (coding->dst_object), bytes);
 }
 
 

src/editfns.c

@@ -968,7 +968,7 @@ usage: (save-current-buffer &rest BODY)  */)
   return unbind_to (count, Fprogn (args));
 }
 
-DEFUN ("buffer-size", Fbufsize, Sbufsize, 0, 1, 0,
+DEFUN ("buffer-size", Fbuffer_size, Sbuffer_size, 0, 1, 0,
        doc: /* Return the number of characters in the current buffer.
 If BUFFER, return the number of characters in that buffer instead.  */)
   (Lisp_Object buffer)
@@ -4883,12 +4883,10 @@ functions if all the text being accessed has this property.  */);
   defsubr (&Sline_beginning_position);
   defsubr (&Sline_end_position);
 
-/*  defsubr (&Smark); */
-/*  defsubr (&Sset_mark); */
   defsubr (&Ssave_excursion);
   defsubr (&Ssave_current_buffer);
 
-  defsubr (&Sbufsize);
+  defsubr (&Sbuffer_size);
   defsubr (&Spoint_max);
   defsubr (&Spoint_min);
   defsubr (&Spoint_min_marker);

src/insdel.c

@@ -388,14 +388,13 @@ make_gap_larger (ptrdiff_t nbytes_added)
   ptrdiff_t real_gap_loc_byte;
   ptrdiff_t old_gap_size;
   ptrdiff_t current_size = Z_BYTE - BEG_BYTE + GAP_SIZE;
-  enum { enough_for_a_while = 2000 };
 
   if (BUF_BYTES_MAX - current_size < nbytes_added)
     buffer_overflow ();
 
   /* If we have to get more space, get enough to last a while;
      but do not exceed the maximum buffer size.  */
-  nbytes_added = min (nbytes_added + enough_for_a_while,
+  nbytes_added = min (nbytes_added + GAP_BYTES_DFL,
 		      BUF_BYTES_MAX - current_size);
 
   enlarge_buffer_text (current_buffer, nbytes_added);
@@ -443,9 +442,9 @@ make_gap_smaller (ptrdiff_t nbytes_removed)
   ptrdiff_t real_beg_unchanged;
   ptrdiff_t new_gap_size;
 
-  /* Make sure the gap is at least 20 bytes.  */
-  if (GAP_SIZE - nbytes_removed < 20)
-    nbytes_removed = GAP_SIZE - 20;
+  /* Make sure the gap is at least GAP_BYTES_MIN bytes.  */
+  if (GAP_SIZE - nbytes_removed < GAP_BYTES_MIN)
+    nbytes_removed = GAP_SIZE - GAP_BYTES_MIN;
 
   /* Prevent quitting in move_gap.  */
   tem = Vinhibit_quit;
@@ -500,7 +499,20 @@ make_gap (ptrdiff_t nbytes_added)
     make_gap_smaller (-nbytes_added);
 #endif
 }
-
+
+/* Add NBYTES to B's gap.  It's enough to temporarily
+   fake current_buffer and avoid real switch to B.  */
+
+void
+make_gap_1 (struct buffer *b, ptrdiff_t nbytes)
+{
+  struct buffer *oldb = current_buffer;
+
+  current_buffer = b;
+  make_gap (nbytes);
+  current_buffer = oldb;
+}
+
 /* Copy NBYTES bytes of text from FROM_ADDR to TO_ADDR.
    FROM_MULTIBYTE says whether the incoming text is multibyte.
    TO_MULTIBYTE says whether to store the text as multibyte.

src/lisp.h

@@ -2778,6 +2778,7 @@ extern void move_gap (ptrdiff_t);
 extern void move_gap_both (ptrdiff_t, ptrdiff_t);
 extern _Noreturn void buffer_overflow (void);
 extern void make_gap (ptrdiff_t);
+extern void make_gap_1 (struct buffer *, ptrdiff_t);
 extern ptrdiff_t copy_text (const unsigned char *, unsigned char *,
 			    ptrdiff_t, bool, bool);
 extern int count_combining_before (const unsigned char *,