chip8-binary-format v0.1.1

CHIP-8 binary format (.c8b files)

CHIP-8 binary format is a file format for CHIP-8 programs that can hold multiple ROMs, interpreter settings and other meta-data. This library allows you to create and parse CBF files.

The file format specification can be found here.

This project is under development, and the file format will probably undergo changes in the future. This library will then follow those changes. Please be aware that those changes may break API compatibility in the future.

This README is equally under development, I'm sorry for the limited documentation 😉

Installation instructions

Install using NPM:

npm install --save chip8-binary-format

Import the library:

const cbf = require('chip8-binary-format');

Quick'n'Dirty getting started guide

If you're just trying to load your first CHIP-8 program from a CBF file, do something like this:

const cbf = require('chip8-binary-format');

let program;
try {
  program = cbf.unpack(file); // file is an array-like object with the binary contents of a CBF file
} catch(e) {
  throw 'Could not parse the file because:\n  * ' + e.join('\n  * ');
}

const binary = program.bytecode.filter(b =>
  b.platforms.includes(cbf.PLATFORM['CHIP-8'])
)
if ( binary.length == 0 )
  throw 'No bytecode present in the file that supports regular CHIP-8';

console.log(`Running program '${program.properties.name || 'Unknown program'}' by ${(program.properties.authors || ['Unknown author']).join(' & ')}`);
startInterpreter(binary[0].bytecode);

Decoding files

Give the library an array-like object with the binary contents of a CBF file:

cbf.unpack(file);

This will return an object that contains properties (meta-data about the program and the way it likes to be run) and bytecode (the actual CHIP-8 binaries that are found in the file, and which platforms they are intended for).

Note that the unpack function may throw an error if the file can't be decoded.

An example of the returned object:

{
  properties: {
    name: "CHIP-8 Test Suite",
    authors: ["Timendus"],
    urls: ["https://github.com/Timendus/chip8-test-suite"],
    description: "A single ROM image containing six distinct tests that will aid you in developing your own CHIP-8, SCHIP or XO-CHIP interpreter (or \"emulator\")",
    keys: {
      "up": 14,
      "down": 15,
      "a": 10,
      "b": 10
    }
  },
  bytecode: [
    {
      platforms: [1,44,45,52],
      platformNames: ["CHIP-8","SUPER-CHIP 1.0","SUPER-CHIP 1.1","XO-CHIP"],
      bytecode: Uint8Array(...)
    }
  ]
}

Where you see the Uint8Array is where you find the bytecode that a CHIP-8 interpreter actually interprets. Note that CBF files may contain multiple of these bytecodes, each with a list of platforms (CHIP-8 variants or 'dialects') that can run them.

Encoding files

You can give the library a data-structure similar to the above to create a CBF file:

cbf.pack({
  properties: {
    name: "My First CBF File",
    description: "CBF is now my favourite container format for CHIP-8 ROMs!",
    screenOrientation: 'upside down',
    cyclesPerFrame: 100
  },
  bytecode: [
    {
      platforms: [cbf.PLATFORM['CHIP-8']],
      bytecode: Uint8Array(...)
    }
  ]
});

This will return a Uint8Array containing the newly created CBF file's binary contents. Note that the pack function may throw an error if the input isn't formatted correctly.