gzip-compress.js

import * as fs from "fs";
import * as util from "util";
import {zopfliAdapter} from "./zopfli-adapter.js";


const readFile = util.promisify(fs.readFile);
const writeFile = util.promisify(fs.writeFile);


async function zopfliCompressFile(file, options) {
    const stat = fs.statSync(file);
    const content = await readFile(file);

    let compressed1 = null;
    let compressed2 = null;

    if (options.zopfliBlocksplittinglast === 'true') {
        compressed2 = await zopfliPromisify(content, {
            numiterations: options.numiterations,
            blocksplitting: true,
            blocksplittinglast: true,
            blocksplittingmax: 15
        });
    } else if (options.zopfliBlocksplittinglast === 'both') {
        compressed1 = await zopfliPromisify(content, {
            numiterations: options.numiterations,
            blocksplitting: true,
            blocksplittinglast: false,
            blocksplittingmax: 15
        });
        compressed2 = await zopfliPromisify(content, {
            numiterations: options.numiterations,
            blocksplitting: true,
            blocksplittinglast: true,
            blocksplittingmax: 15
        });
    } else {
        compressed1 = await zopfliPromisify(content, {
            numiterations: options.numiterations,
            blocksplitting: true,
            blocksplittinglast: false,
            blocksplittingmax: 15
        });
    }

    if (compressed1 !== null && compressed1.length < stat.size) {
        if (compressed2 !== null && compressed2.length < compressed1.length) {
            await writeFile(file + '.gz', compressed2);
            return compressed2.length;
        } else {
            await writeFile(file + '.gz', compressed1);
            return compressed1.length;
        }
    } else if (compressed2 !== null && compressed2.length < stat.size) {
        await writeFile(file + '.gz', compressed2);
        return compressed2.length;
    }

    return stat.size;
}

async function zopfliPromisify(content, options) {
    const zopfli = await zopfliAdapter();
    return new Promise((resolve, reject) => {
        zopfli.gzip(content, options, (err, compressedContent) => {
            if (!err) {
                resolve(compressedContent);
            } else {
                reject(err);
            }
        });
    });
}

process.on('message', async (message) => {
    const fileSize = await zopfliCompressFile(message.name, message.options);
    process.send(fileSize);
});

process.send({ready: true});