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cart.js
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cart.js
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var fs = require('fs');
var path = require('path');
const { Mapper0 } = require('./mapper0');
module.exports.Cart = class Cart {
constructor(pth) {
const rom = fs.readFileSync(path.join(__dirname, pth || "./rom/mario.nes"));
const nesHeader = (rom[0] << 24 + rom[1] << 16 + rom[2] << 8 + rom[3]) & 0xffffffff;
if (!nesHeader == 0x1a53454e) {
throw Error("unmatched nes header")
}
this.prgCount = rom[4] // PRG-ROM page count
this.chrCount = rom[5] // CHR-ROM page count
this.control1 = rom[6] // mapper mirroring battery trainer
this.control2 = rom[7] // mapper mirroring battery trainer
const mapper1 = this.control1 >> 4
const mapper2 = this.control2 >> 4
this.mapper = mapper1 | mapper2 << 4
const mirror1 = this.control1 & 1
const mirror2 = (this.control1 >> 3) & 1
this.mirror = mirror1 | mirror2 << 1
this.sram = new Array(0x2000).fill(0x00)
this.battery = (this.control1 >> 1) & 1
const Z = 16 + (16384 * this.prgCount)
this.chr = [];
this.prg = [];
for (let i = 16; i < Z; i++) {
this.prg.push(rom[i])
}
for (let i = Z; i < Z + 8192 * this.chrCount; i++) {
this.chr.push(rom[i])
}
if (this.chrCount == 0) {
this.chr = new Array(8129).fill(0x00)
}
}
createMapper() {
switch (this.mapper) {
case 0:
return new Mapper0(this)
default:
throw Error("unsupported Mapper for now!")
}
}
}