@soapbox.pub/wasmboy/lib/wasmboy/fetchrom.js

Soapbox fork of Wasmboy.

// Modules
import uzip from '../3p/UZIP';

// Collection of functions to parse roms
// Private function to fetch a game
export const fetchROMAsByteArray = (ROM, loadOptions) => {
  const fetchROMAsByteArrayTask = async () => {
    // Check if we were passed straight bytes
    if (ArrayBuffer.isView(ROM) && ROM.constructor === Uint8Array) {
      return {
        ROM: ROM
      };
    } else if (typeof ROM === 'object' && ROM.size) {
      // We were passed a file from HTML file input

      // Read the file as a Uint8Array
      let byteArray = await getROMFromFileReaderAsByteArray(ROM);

      if (ROM.name.toLowerCase().endsWith('.zip')) {
        byteArray = await parseByteArrayAsZip(byteArray);
      }

      return {
        ROM: byteArray,
        name: ROM.name
      };
    } else {
      // We were passed a URL

      // Fetch the file
      // First check if we have headers
      const fetchHeaders = {};
      if (loadOptions && loadOptions.headers) {
        fetchHeaders.headers = loadOptions.headers;
      }

      let bytes = await fetch(ROM, fetchHeaders).then(blob => {
        if (!blob.ok) {
          return Promise.reject(blob);
        }
        return blob.arrayBuffer();
      });

      let fileName = ROM;
      if (loadOptions && loadOptions.fileName) {
        fileName = loadOptions.fileName;
      }

      // Get our byteArray
      let byteArray = new Uint8Array(bytes);

      if (fileName.toLowerCase().endsWith('.zip')) {
        byteArray = await parseByteArrayAsZip(byteArray);
      }

      return {
        ROM: byteArray,
        name: fileName
      };
    }
  };

  return fetchROMAsByteArrayTask();
};

const getROMFromFileReaderAsByteArray = async ROM => {
  const fileReaderByteArray = await new Promise((resolve, reject) => {
    // Read the file object
    // https://www.javascripture.com/FileReader#readAsArrayBuffer_Blob
    const fileReader = new FileReader();
    fileReader.onload = () => {
      const byteArray = new Uint8Array(fileReader.result);
      resolve(byteArray);
    };
    fileReader.readAsArrayBuffer(ROM);
  });
  return fileReaderByteArray;
};

// Function to parse and find the gb files within an archive
const parseByteArrayAsZip = async byteArray => {
  // Parse the zip using UZIP
  const unzipObject = await uzip.parse(byteArray);

  // Find the ROM in the output
  let foundROM = false;
  const unzipObjectKeys = Object.keys(unzipObject);
  unzipObjectKeys.some(key => {
    const lowercaseKey = key.toLowerCase();
    if (lowercaseKey.includes('.gb') || lowercaseKey.includes('.gbc') || lowercaseKey.includes('.bin')) {
      foundROM = unzipObject[key];
      return true;
    }
    return false;
  });

  if (!foundROM) {
    throw new Error('Could not find a ROM in zip...');
  }

  return foundROM;
};