Plugin System – an alternative to GetProcAddress and interfaces

// BMPParser.cpp - a very simple BMP file parser
//
// Part of the Plugin System tutorial
//
///////////////////////////////////////////////////////////////////////////////

#include <windows.h>
#include <stdio.h>
#include "..\Host\Host.h"
#include "..\Host\ImageParser.h"

// CBMPParser inherits from CImageParser
class CBMPParser: public CImageParser
{
public:
	virtual HBITMAP ParseFile( const char *fname );
	virtual bool SupportsType( const char *type ) const;
};

// Parses a BMP file
HBITMAP CBMPParser::ParseFile( const char *fname )
{
	FILE *f=fopen(fname,"rb");
	if (!f) return NULL;

	BITMAPFILEHEADER bmfh;
	memset(&bmfh,0,sizeof(bmfh));
	fread(&bmfh,sizeof(bmfh),1,f);
	BITMAPINFOHEADER bmih;
	memset(&bmih,0,sizeof(bmih));
	fread(&bmih,sizeof(bmih),1,f);
	int width=bmih.biWidth;
	int height=bmih.biHeight;

	if (bmih.biBitCount!=24) {
		// only 24 bit images are supported
		fclose(f);
		return NULL;
	}

	// create the HBITMAP
	void *data;
	HBITMAP bitmap=CreateBitmap(width,height,&data);
	if (!bitmap) {
		fclose(f);
		return NULL;
	}

	// read the pixels
	int pitch=(width*3+3)&~3;
	fread(data,pitch,height,f);

	fclose(f);
	return bitmap;
}

// Notifies the host that the plugin supports the BMP type
bool CBMPParser::SupportsType( const char *type ) const
{
	return stricmp(type,".bmp")==0;
}

static CBMPParser g_BMPParser;