From: Mikko Rasa <tdb@tdb.fi>
Date: Sun, 26 Aug 2012 12:03:21 +0000 (+0300)
Subject: Improve performance of Bufferable::update_buffer_data
X-Git-Url: http://git.tdb.fi/?p=libs%2Fgl.git;a=commitdiff_plain;h=719578516a4d44a6f39eac3b074ce9f6180b5d53

Improve performance of Bufferable::update_buffer_data

... by avoiding the walk through the entire chain every time it is
called.  It's not necessary to add up all the sizes either, since we can
just get the end of the last Bufferable.
---

diff --git a/source/bufferable.cpp b/source/bufferable.cpp
index 4660e9c3..12e0aef7 100644
--- a/source/bufferable.cpp
+++ b/source/bufferable.cpp
@@ -74,19 +74,22 @@ void Bufferable::update_buffer_offset()
 
 void Bufferable::update_buffer_data() const
 {
-	const Bufferable *first = this;
-	for(; first->prev_in_buffer; first=first->prev_in_buffer) ;
-
-	unsigned total_size = 0;
-	for(const Bufferable *b=first; b; b=b->next_in_buffer)
-		total_size += b->get_data_size();
-
-	if(total_size!=buffer->get_size())
+	if(buffer_offset+get_data_size()>=buffer->get_size())
 	{
-		buffer->data(total_size, 0);
-		// Resizing the buffer invalidates its contents.
-		for(const Bufferable *b=first; b; b=b->next_in_buffer)
-			b->dirty = true;
+		const Bufferable *last = this;
+		for(; last->next_in_buffer; last=last->next_in_buffer) ;
+
+		unsigned total_size = last->buffer_offset+last->get_data_size();
+
+		if(total_size>buffer->get_size())
+		{
+			buffer->data(total_size, 0);
+			/* Resizing the buffer invalidates its contents.  Non-dirty data may
+			be in use, so reupload it. */
+			for(const Bufferable *b=last; b; b=b->prev_in_buffer)
+				if(!b->dirty)
+					b->upload_data();
+		}
 	}
 
 	upload_data();