Improve performance of `find-buffer-visiting' (bug#66117)

* src/buffer.c (Fget_truename_buffer): Expose `get_truename_buffer' to
Elisp.
(Ffind_buffer): New subr searching for a live buffer with a given
value of buffer-local variable.
(syms_of_buffer): Register the new added subroutines.
* src/filelock.c (lock_file): Use the new `Fget_truename_buffer' name.
* src/lisp.h:
* test/manual/etags/c-src/emacs/src/lisp.h: Remove no-longer-necessary
extern declarations for `get_truename_buffer'.
* lisp/files.el (find-buffer-visiting): Refactor, using subroutines to
search for buffers instead of slow manual Elisp iterations.

1 files changed, 23 insertions, 2 deletions

diff --git a/src/buffer.c b/src/buffer.c
index ea0c23192b7..73e9839f883 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -519,8 +519,11 @@ See also `find-buffer-visiting'.  */)
   return Qnil;
 }
 
-Lisp_Object
-get_truename_buffer (register Lisp_Object filename)
+DEFUN ("get-truename-buffer", Fget_truename_buffer, Sget_truename_buffer, 1, 1, 0,
+       doc: /* Return the buffer with `file-truename' equal to FILENAME (a string).
+If there is no such live buffer, return nil.
+See also `find-buffer-visiting'.  */)
+  (register Lisp_Object filename)
 {
   register Lisp_Object tail, buf;
 
@@ -533,6 +536,22 @@ get_truename_buffer (register Lisp_Object filename)
   return Qnil;
 }
 
+DEFUN ("find-buffer", Ffind_buffer, Sfind_buffer, 2, 2, 0,
+       doc: /* Return the buffer with buffer-local VARIABLE equal to VALUE.
+	       If there is no such live buffer, return nil.
+See also `find-buffer-visiting'.  */)
+  (Lisp_Object variable, Lisp_Object value)
+{
+  register Lisp_Object tail, buf;
+
+  FOR_EACH_LIVE_BUFFER (tail, buf)
+    {
+      if (!NILP (Fequal (value, Fbuffer_local_value(variable, buf))))
+	return buf;
+    }
+  return Qnil;
+}
+
 /* Run buffer-list-update-hook if Vrun_hooks is non-nil and BUF does
    not have buffer hooks inhibited.  */
 
@@ -6010,6 +6029,8 @@ There is no reason to change that value except for debugging purposes.  */);
   defsubr (&Sbuffer_list);
   defsubr (&Sget_buffer);
   defsubr (&Sget_file_buffer);
+  defsubr (&Sget_truename_buffer);
+  defsubr (&Sfind_buffer);
   defsubr (&Sget_buffer_create);
   defsubr (&Smake_indirect_buffer);
   defsubr (&Sgenerate_new_buffer_name);