Fast save_excursion_save and save_excursion_restore.

* lisp.h (struct Lisp_Excursion): New data type.
(PVEC_EXCURSION): New pseudovector type.
(XEXCURSION, XSETEXCURSION, EXCURSIONP): Convenient macros
to deal with it.  Adjust comments.
(init_marker, attach_marker): New prototype.
(unchain_marker): Adjust prototype.
* marker.c (attach_marker): Change to global.
(init_marker): New function.
* alloc.c (Fmake_marker, build_marker): Use it.
(build_marker): More easserts.
(mark_object): Handle struct Lisp_Excursion.
* editfns.c (save_excursion_save, save_excursion_restore):
Reimplement to use struct Lisp_Excursion.  Add comments.

1 files changed, 29 insertions, 24 deletions

diff --git a/src/alloc.c b/src/alloc.c
index ac6cb861c4d..5377b27e329 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -3653,17 +3653,10 @@ DEFUN ("make-marker", Fmake_marker, Smake_marker, 0, 0, 0,
        doc: /* Return a newly allocated marker which does not point at any place.  */)
   (void)
 {
-  register Lisp_Object val;
-  register struct Lisp_Marker *p;
+  register Lisp_Object marker = allocate_misc (Lisp_Misc_Marker);
 
-  val = allocate_misc (Lisp_Misc_Marker);
-  p = XMARKER (val);
-  p->buffer = 0;
-  p->bytepos = 0;
-  p->charpos = 0;
-  p->next = NULL;
-  p->insertion_type = 0;
-  return val;
+  init_marker (XMARKER (marker), NULL, 0, 0, 0);
+  return marker;
 }
 
 /* Return a newly allocated marker which points into BUF
@@ -3672,24 +3665,23 @@ DEFUN ("make-marker", Fmake_marker, Smake_marker, 0, 0, 0,
 Lisp_Object
 build_marker (struct buffer *buf, ptrdiff_t charpos, ptrdiff_t bytepos)
 {
-  Lisp_Object obj;
-  struct Lisp_Marker *m;
+  register Lisp_Object marker = allocate_misc (Lisp_Misc_Marker);
+
+  /* Use Fmake_marker to create marker points to nowhere.  */
+  eassert (buf != NULL);
 
   /* No dead buffers here.  */
   eassert (!NILP (BVAR (buf, name)));
 
-  /* Every character is at least one byte.  */
-  eassert (charpos <= bytepos);
-
-  obj = allocate_misc (Lisp_Misc_Marker);
-  m = XMARKER (obj);
-  m->buffer = buf;
-  m->charpos = charpos;
-  m->bytepos = bytepos;
-  m->insertion_type = 0;
-  m->next = BUF_MARKERS (buf);
-  BUF_MARKERS (buf) = m;
-  return obj;
+  /* In a single-byte buffer, two positions must be equal.
+     Otherwise, every character is at least one byte.  */
+  if (BUF_Z (buf) == BUF_Z_BYTE (buf))
+    eassert (charpos == bytepos);
+  else
+    eassert (charpos <= bytepos);
+
+  init_marker (XMARKER (marker), buf, charpos, bytepos, 0);
+  return marker;
 }
 
 /* Put MARKER back on the free list after using it temporarily.  */
@@ -6057,6 +6049,19 @@ mark_object (Lisp_Object arg)
           case PVEC_SUBR:
             break;
 
+          case PVEC_EXCURSION:
+            {
+              struct Lisp_Excursion *e = (struct Lisp_Excursion *) ptr;
+              /* No Lisp_Objects but two special pointers to mark here.  */
+              eassert (e->buffer != NULL);
+              eassert (e->window != NULL);
+              if (!VECTOR_MARKED_P (e->buffer))
+                mark_buffer (e->buffer);
+              if (!VECTOR_MARKED_P (e->window))
+                mark_vectorlike ((struct Lisp_Vector *) e->window);
+            }
+            break;
+
           case PVEC_FREE:
             abort ();