gecko-dev/xpcom/tests/SizeTest01.cpp

// Test01.cpp

#include "nsIDOMNode.h"
#include "nsCOMPtr.h"
#include "nsIPtr.h"



NS_DEF_PTR(nsIDOMNode);

	/*
		This test file compares the generated code size of similar functions between raw
		COM interface pointers (|AddRef|ing and |Release|ing by hand), |nsCOMPtr|s, and
		the smart-pointer macro defined in "nsIPtr.h".

		Function size results were determined by examining dissassembly of the generated code.
		mXXX is the size of the generated code on the Macintosh.  wXXX is the size on Windows.
		For these tests, all reasonable optimizations were enabled and exceptions were
		disabled (just as we build for release).

		The tests in this file explore only the simplest functionality: assigning a pointer
		to be reference counted into a [raw, nsCOMPtr, nsIPtr] object; ensuring that it is
		|AddRef|ed and |Release|d appropriately; calling through the pointer to a function
		supplied by the underlying COM interface.

		Windows:
			raw_optimized														 31 bytes
			raw, nsCOMPtr*													 34
			nsCOMPtr_optimized*											 38
			nsCOMPtr_optimized											 42
			nsCOMPtr																 46
			nsIPtr, nsIPtr_optimized								 34 + 196


		Macintosh:
			raw_optimized, nsCOMPtr_optimized				112 bytes 	(1.0000)
			nsCOMPtr																120					(1.0714)	i.e., 7.14% bigger than raw_optimized et al
			nsIPtr_optimized												124 				(1.1071)
			nsIPtr																	136 				(1.2143)
			raw																			140 				(1.2500)

		The overall difference in size between Windows and Macintosh is caused by the
		the PowerPC RISC architecture where every instruction is 4 bytes.

		Also note that on Windows, nsIPtr generates a out-of-line destructors
		which _are_ used, totalling an additional 196 bytes of code space per class used,
		per file it is used in.

		On Macintosh, both nsCOMPtr and nsIPtr generate out-of-line destructors which are
		not referenced, and which can be stripped by the linker.

		Also note that on all platforms, each use of the |NS_DEFINE_IID| macro adds 16 bytes of static
		data per file, while GetIID() has the same code profile and adds only 16 bytes of data to the entire
		program, reguardless of the number of uses (greater than one).
	*/

void
Test01_raw( nsIDOMNode* aDOMNode, nsString* aResult )
		// m140, w34
	{
			/*
				This test is designed to be more like a typical large function where,
				because you are working with several resources, you don't just return when
				one of them is |NULL|.  Similarly: |Test01_nsCOMPtr00|, and |Test01_nsIPtr00|.
			*/

		nsIDOMNode* node = aDOMNode;
		NS_IF_ADDREF(node);

		if ( node )
			node->GetNodeName(*aResult);

		NS_IF_RELEASE(node);
	}

void
Test01_raw_optimized( nsIDOMNode* aDOMNode, nsString* aResult )
		// m112, w31
	{
			/*
				This test simulates smaller functions where you _do_ just return
				|NULL| at the first sign of trouble.  Similarly: |Test01_nsCOMPtr01|,
				and |Test01_nsIPtr01|.
			*/

			/*
				This test produces smaller code that |Test01_raw| because it avoids
				the three tests: |NS_IF_...|, and |if ( node )|.
			*/

// -- the following code is assumed, but is commented out so we compare only
//		 the relevent generated code

//		if ( !aDOMNode )
//			return;

		nsIDOMNode* node = aDOMNode;
		NS_ADDREF(node);
		node->GetNodeName(*aResult);
		NS_RELEASE(node);
	}

void
Test01_nsCOMPtr( nsIDOMNode* aDOMNode, nsString* aResult )
		// m120, w46/34
	{
		nsCOMPtr<nsIDOMNode> node = aDOMNode;

		if ( node )
			node->GetNodeName(*aResult);
	}

void
Test01_nsCOMPtr_optimized( nsIDOMNode* aDOMNode, nsString* aResult )
		// m112, w42/38
	{
//		if ( !aDOMNode )
//			return;

		nsCOMPtr<nsIDOMNode> node = aDOMNode;
		node->GetNodeName(*aResult);
	}

void
Test01_nsIPtr( nsIDOMNode* aDOMNode, nsString* aResult )
		// m136, w34
	{
		nsIDOMNodePtr node = aDOMNode;
		node.AddRef();

		if ( node.IsNotNull() )
			node->GetNodeName(*aResult);
	}

void
Test01_nsIPtr_optimized( nsIDOMNode* aDOMNode, nsString* aResult )
		// m124, w34
	{
//		if ( !aDOMNode )
//			return;

		nsIDOMNodePtr node = aDOMNode;
		node.AddRef();
		node->GetNodeName(*aResult);
	}