formats.exposed/public/index/constants.js

// @ts-check

/**
 * @typedef {object} MimeSniffPattern
 * @prop {ArrayLike<number>} bytes The byte pattern to use for MIME sniffing, lifted from the "MIME Sniffing" spec.
 * @prop {ArrayLike<number>} mask The pattern mask to use for MIME sniffing, lifted from the "MIME Sniffing" spec.
 */

/**
 * @typedef {object} SupportedFileType
 * @prop {string} name The English name of a file type.
 * @prop {string[]} extensions File extension for this type, with the leading dot.
 * @prop {string} mimeType MIME type for this file type.
 * @prop {string} route The route to the file type's page.
 * @prop {MimeSniffPattern[]} mimeSniffPatterns MIME sniffing patterns.
 */

/** @type {SupportedFileType[]} */
export const SUPPORTED_FILE_TYPES = [
  {
    name: "GIF",
    extensions: [".gif", "image/gif"],
    mimeType: "image/gif",
    route: "gif/",
    mimeSniffPatterns: [
      {
        bytes: [0x47, 0x49, 0x46, 0x38, 0x37, 0x61],
        mask: [0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF],
      },
      {
        bytes: [0x47, 0x49, 0x46, 0x38, 0x39, 0x61],
        mask: [0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF],
      },
    ],
  },
  {
    name: "PNG",
    extensions: [".png", ".apng"],
    mimeType: "image/png",
    route: "png/",
    mimeSniffPatterns: [{
      bytes: [0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A],
      mask: [0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF],
    }],
  },
];