From bd3e61a3d71a527b7b87197c2f52c5cf342aba81 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sat, 25 Aug 2012 00:50:00 +0300
Subject: [PATCH] Add a class to negotiate the storage of multiple objects in a
 buffer

---
 source/bufferable.cpp | 89 +++++++++++++++++++++++++++++++++++++++++++
 source/bufferable.h   | 37 ++++++++++++++++++
 2 files changed, 126 insertions(+)
 create mode 100644 source/bufferable.cpp
 create mode 100644 source/bufferable.h

diff --git a/source/bufferable.cpp b/source/bufferable.cpp
new file mode 100644
index 00000000..5c7cb9e0
--- /dev/null
+++ b/source/bufferable.cpp
@@ -0,0 +1,89 @@
+#include <stdexcept>
+#include "buffer.h"
+#include "bufferable.h"
+
+using namespace std;
+
+namespace Msp {
+namespace GL {
+
+Bufferable::Bufferable():
+	buffer(0),
+	buffer_offset(0),
+	next_in_buffer(0),
+	prev_in_buffer(0),
+	dirty(false)
+{ }
+
+Bufferable::~Bufferable()
+{
+	unlink_from_buffer();
+}
+
+void Bufferable::use_buffer(Buffer *buf, Bufferable *prev)
+{
+	if(prev && buf!=prev->buffer)
+		throw invalid_argument("Bufferable::use_buffer");
+
+	if(buffer)
+		unlink_from_buffer();
+
+	buffer = buf;
+	if(buffer)
+	{
+		prev_in_buffer = prev;
+		if(prev_in_buffer)
+			prev_in_buffer->next_in_buffer = this;
+	}
+
+	update_buffer_offsets();
+}
+
+void Bufferable::unlink_from_buffer()
+{
+	if(prev_in_buffer)
+		prev_in_buffer->next_in_buffer = next_in_buffer;
+	if(next_in_buffer)
+	{
+		next_in_buffer->prev_in_buffer = prev_in_buffer;
+		next_in_buffer->update_buffer_offsets();
+	}
+	prev_in_buffer = 0;
+	next_in_buffer = 0;
+}
+
+void Bufferable::update_buffer_offsets()
+{
+	unsigned offset = 0;
+	if(prev_in_buffer)
+		offset = prev_in_buffer->buffer_offset+prev_in_buffer->get_data_size();
+
+	if(offset!=buffer_offset)
+	{
+		buffer_offset = offset;
+		dirty = true;
+	}
+
+	if(next_in_buffer)
+		next_in_buffer->update_buffer_offsets();
+}
+
+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();
+
+	buffer->data(total_size, 0);
+	for(const Bufferable *b=first; b; b=b->next_in_buffer)
+	{
+		buffer->sub_data(b->buffer_offset, b->get_data_size(), b->get_data());
+		b->dirty = false;
+	}
+}
+
+} // namespace GL
+} // namespace Msp
diff --git a/source/bufferable.h b/source/bufferable.h
new file mode 100644
index 00000000..dd7cff8e
--- /dev/null
+++ b/source/bufferable.h
@@ -0,0 +1,37 @@
+#ifndef MSP_GL_BUFFERABLE_H_
+#define MSP_GL_BUFFERABLE_H_
+
+namespace Msp {
+namespace GL {
+
+class Buffer;
+
+class Bufferable
+{
+protected:
+	Buffer *buffer;
+	unsigned buffer_offset;
+	Bufferable *next_in_buffer;
+	Bufferable *prev_in_buffer;
+	mutable bool dirty;
+
+	Bufferable();
+public:
+	virtual ~Bufferable();
+
+	void use_buffer(Buffer *, Bufferable * = 0);
+private:
+	void unlink_from_buffer();
+
+protected:
+	virtual unsigned get_data_size() const = 0;
+	virtual const void *get_data() const = 0;
+
+	void update_buffer_offsets();
+	void update_buffer_data() const;
+};
+
+} // namespace GL
+} // namespace Msp
+
+#endif
-- 
2.43.0