Add indirection counting to speed up Fkill_buffer.

* buffer.h (struct buffer): New member.
* buffer.c (Fget_buffer_create): Set indirection counter to 0.
(Fmake_indirect_buffer): Set indirection counter to -1, increment
base buffer indirection counter.
(compact_buffer): If ENABLE_CHECKING, verify indirection counters.
(Fkill_buffer): Adjust indirection counters as needed, don't walk
through buffer list if indirection counter is 0.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/buffer.h b/src/buffer.h
index a97cc13705b..69be4dc7773 100644
--- a/src/buffer.h
+++ b/src/buffer.h
@@ -775,6 +775,11 @@ struct buffer
      In an ordinary buffer, it is 0.  */
   struct buffer *base_buffer;
 
+  /* In an indirect buffer, this is -1. In an ordinary buffer,
+     it's the number of indirect buffers which shares our text;
+     zero means that we're the only owner of this text.  */
+  int indirections;
+
   /* A non-zero value in slot IDX means that per-buffer variable
      with index IDX has a local value in this buffer.  The index IDX
      for a buffer-local variable is stored in that variable's slot