# HG changeset patch
# User Matthew Wild <mwild1@gmail.com>
# Date 1665484675 -3600
# Node ID d26eefe98d09088823a53441bdf7311536acbc28
# Parent  79b89f3822909a0effea050b02d72a8e5d8f3116
util.dbuffer: Add efficient shortcuts for discard() in certain cases

If the buffer is already empty, nothing to do. If we're throwing away the
whole buffer, we can just empty it and avoid read_chunk() (which in turn
may collapse()). These shortcuts are much more efficient.

diff -r 79b89f382290 -r d26eefe98d09 util/dbuffer.lua
--- a/util/dbuffer.lua	Tue Oct 11 11:34:47 2022 +0100
+++ b/util/dbuffer.lua	Tue Oct 11 11:37:55 2022 +0100
@@ -91,8 +91,12 @@
 end
 
 function dbuffer_methods:discard(requested_bytes)
-	if requested_bytes > self._length then
-		return nil;
+	if self._length == 0 then return true; end
+	if not requested_bytes or requested_bytes >= self._length then
+		self.front_consumed = 0;
+		self._length = 0;
+		for _ in self.items:consume() do end
+		return true;
 	end
 
 	local chunk, read_bytes = self:read_chunk(requested_bytes);