keynote-parser2/lib/parse/parse-iwa-snappy-frame.js

A library for parsing Apple Keynote file

"use strict";
var __importDefault = (this && this.__importDefault) || function (mod) {
    return (mod && mod.__esModule) ? mod : { "default": mod };
};
Object.defineProperty(exports, "__esModule", { value: true });
exports.parseIwaSnappyFrame = void 0;
const snappyjs_1 = __importDefault(require("snappyjs"));
/**
 * Unpack IWA file chunk data from snappy frame
 *
 * - 0: 0x00
 * - 1 ~ 3: length of the chunk data (little-endian)
 * - 4 ~ 4 + chunk data length: snappy compressed chunk data
 *
 * @see https://github.com/obriensp/iWorkFileFormat/blob/master/Docs/index.md#snappy-compression
 */
const parseIwaSnappyFrame = (data, cursor) => {
    // the first byte of the frame is always 0x00
    if (data[cursor] !== 0x00) {
        throw new Error('Invalid IWA snappy frame');
    }
    // the 1-3 bytes of the frame are the data length of the chunk
    const chunkBufferLength = data.readUintLE(cursor + 1, 3);
    // get the snappy compressed chunk data
    const chunkBufferStart = cursor + 4;
    const chunkBufferEnd = chunkBufferStart + chunkBufferLength;
    const chunkBuffer = data.subarray(chunkBufferStart, chunkBufferEnd);
    // uncompress the chunk data
    const chunk = snappyjs_1.default.uncompress(chunkBuffer);
    return {
        chunk,
        nextCursor: chunkBufferEnd,
    };
};
exports.parseIwaSnappyFrame = parseIwaSnappyFrame;