@woosh/meep-engine/src/engine/asset/loaders/image/jpeg/buildHuffmanTable.js

Pure JavaScript game engine. Fully featured and production ready.

/**
 *
 * @param {Uint8Array} codeLengths
 * @param {Uint8Array} values
 * @return {[]}
 */
export function buildHuffmanTable(codeLengths, values) {
    let k = 0;
    const code = [];
    let i, j, length = 16;

    while (length > 0 && !codeLengths[length - 1]) {
        length--;
    }

    code.push({ children: [], index: 0 });
    let p = code[0], q;
    for (i = 0; i < length; i++) {

        for (j = 0; j < codeLengths[i]; j++) {
            p = code.pop();
            p.children[p.index] = values[k];
            while (p.index > 0) {
                if (code.length === 0)
                    throw new Error('Could not recreate Huffman Table');
                p = code.pop();
            }
            p.index++;
            code.push(p);
            while (code.length <= i) {
                code.push(q = { children: [], index: 0 });
                p.children[p.index] = q.children;
                p = q;
            }
            k++;
        }

        if (i + 1 < length) {
            // p here points to last code
            code.push(q = { children: [], index: 0 });
            p.children[p.index] = q.children;
            p = q;
        }
    }
    return code[0].children;
}