From 3b159edbe4e80a2bc19c4c2fcd42cb996b9fbfe0 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sat, 3 Dec 2016 17:53:19 +0200
Subject: [PATCH] Remove dynamic allocation from VertexFormat

On 64-bit systems the pointer takes eight bytes, and a typical malloc
implementation will have two pointers worth of overhead.  Vertex formats
hardly ever reach even eight components, so it's cheaper to just store
a fixed-size array in the class itself.
---
 source/vertexformat.cpp | 59 +++++++----------------------------------
 source/vertexformat.h   | 14 +++++-----
 2 files changed, 17 insertions(+), 56 deletions(-)

diff --git a/source/vertexformat.cpp b/source/vertexformat.cpp
index 8cc0cec9..037305f8 100644
--- a/source/vertexformat.cpp
+++ b/source/vertexformat.cpp
@@ -11,72 +11,33 @@ namespace Msp {
 namespace GL {
 
 VertexFormat::VertexFormat():
-	data(0)
+	count(0)
 { }
 
 VertexFormat::VertexFormat(VertexComponent c):
-	data(new unsigned char[8])
+	count(1)
 {
-	data[0] = 1;
-	data[1] = c;
-}
-
-VertexFormat::VertexFormat(const VertexFormat &f):
-	data(0)
-{
-	*this = f;
-}
-
-VertexFormat &VertexFormat::operator=(const VertexFormat &f)
-{
-	delete[] data;
-	if(f.data)
-	{
-		data = new unsigned char[(f.data[0]&~7)+8];
-		copy(f.data, f.data+f.data[0]+1, data);
-	}
-	else
-		data = 0;
-
-	return *this;
-}
-
-VertexFormat::~VertexFormat()
-{
-	delete[] data;
+	components[0] = c;
 }
 
 VertexFormat VertexFormat::operator,(VertexComponent c) const
 {
+	if(count>=MAX_COMPONENTS)
+		throw invalid_operation("VertexFormat::operator,");
+
 	VertexFormat r = *this;
-	if(r.data)
-	{
-		const unsigned char n = ++r.data[0];
-		if((n&7)==0)
-		{
-			unsigned char *newdt = new unsigned char[n+8];
-			copy(r.data, r.data+n, newdt);
-			delete r.data;
-			r.data = newdt;
-		}
-		r.data[n] = c;
-	}
-	else
-	{
-		r.data = new unsigned char[8];
-		r.data[0] = 1;
-		r.data[1] = c;
-	}
+	r.components[r.count++] = c;
 
 	return r;
 }
 
 VertexFormat VertexFormat::operator,(unsigned i) const
 {
-	if(!data)
+	if(!count)
 		throw invalid_operation("VertexFormat::operator,");
+
 	VertexFormat r = *this;
-	unsigned char *c = r.data+r.data[0];
+	unsigned char *c = &r.components[r.count-1];
 	*c = make_indexed_component(static_cast<VertexComponent>(*c), i);
 
 	return r;
diff --git a/source/vertexformat.h b/source/vertexformat.h
index 4c343c99..7edca1f3 100644
--- a/source/vertexformat.h
+++ b/source/vertexformat.h
@@ -33,21 +33,21 @@ enum VertexComponent
 class VertexFormat
 {
 private:
-	unsigned char *data;
+	enum { MAX_COMPONENTS = 15 };
+
+	unsigned char count;
+	unsigned char components[MAX_COMPONENTS];
 
 public:
 	VertexFormat();
 	VertexFormat(VertexComponent);
-	VertexFormat(const VertexFormat &);
-	VertexFormat &operator=(const VertexFormat &);
-	~VertexFormat();
 
 	VertexFormat operator,(VertexComponent c) const;
 	VertexFormat operator,(unsigned i) const;
 
-	bool empty() const { return !data || !data[0]; }
-	const unsigned char *begin() const { return data ? data+1 : 0; }
-	const unsigned char *end() const { return data ? data+1+data[0] : 0; }
+	bool empty() const { return !count; }
+	const unsigned char *begin() const { return components; }
+	const unsigned char *end() const { return components+count; }
 	unsigned stride() const;
 	int offset(VertexComponent) const;
 };
-- 
2.43.0