nes-emulator/Mapper.cpp at master · kingcodefish/nes-emulator · GitHub

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#pragma once
#include "Mapper.h"

Mapper::Mapper(uint8_t* rom) : rom(rom)
{
	// Read infos from header
	prgSize = rom[4] * 0x4000;
	chrSize = rom[5] * 0x2000;
	prgRamSize = rom[8] ? rom[8] * 0x2000 : 0x2000;

	this->prg = &rom[0] + 16;
	this->prgRam = new uint8_t[prgRamSize];

	// CHR ROM:
	if(chrSize)
		this->chr = &rom[0] + 16 + prgSize;
	// CHR RAM:
	else
	{
		chrRam = true;
		chrSize = 0x2000;
		this->chr = new uint8_t[chrSize];
	}
}

Mapper::~Mapper()
{
	delete rom;
	delete prgRam;
	if(chrRam)
		delete chr;
}

/* Access to memory */
uint8_t Mapper::read(uint16_t addr)
{
	if(addr >= 0x8000)
		return prg[prgMap[(addr - 0x8000) / 0x2000] + ((addr - 0x8000) % 0x2000)];
		//return (prgSize);
	else
		return prgRam[addr - 0x6000];
}

uint8_t Mapper::chr_read(uint16_t addr)
{
	return chr[chrMap[addr / 0x400] + (addr % 0x400)];
}

/* PRG mapping functions */
template <int pageKBs> void Mapper::map_prg(int slot, int bank)
{
	if(bank < 0)
		bank = (prgSize / (0x400 * pageKBs)) + bank;

	for(int i = 0; i < (pageKBs / 8); i++)
		prgMap[(pageKBs / 8) * slot + i] = (pageKBs * 0x400 * bank + 0x2000 * i) % prgSize;
}
template void Mapper::map_prg<32>(int, int);
template void Mapper::map_prg<16>(int, int);
template void Mapper::map_prg<8>(int, int);

/* CHR mapping functions */
template <int pageKBs> void Mapper::map_chr(int slot, int bank)
{
	for(int i = 0; i < pageKBs; i++)
		chrMap[pageKBs*slot + i] = (pageKBs * 0x400 * bank + 0x400 * i) % chrSize;
}
template void Mapper::map_chr<8>(int, int);
template void Mapper::map_chr<4>(int, int);
template void Mapper::map_chr<2>(int, int);
template void Mapper::map_chr<1>(int, int);