@ankhzet/goo/dist/cjs/rle/rleDecode.js

Elegoo .goo file format reader/writer

export const rleDecode = (buffer) => {
    const slice = 5 * 1024 * 1024;
    let pos = 0;
    let offset = 0;
    let total = buffer.length;
    const arrays = [];
    let arr = new Uint8Array(slice);
    const flush = (init) => {
        arrays.push(arr.slice(0, pos));
        if (init) {
            pos = 0;
            arr = new Uint8Array(slice);
        }
    };
    const consume = (pixel, count) => {
        if (pixel) {
            while (count-- > 0) {
                if (pos + 1 > slice) {
                    flush(true);
                }
                arr[pos++] = pixel;
            }
        }
        else {
            while (count > slice - pos) {
                const delta = slice - pos;
                pos += delta;
                count -= delta;
                flush(true);
            }
            pos += count;
        }
    };
    let prev = 0;
    while (offset < total) {
        const byte0 = buffer.readUint8(offset++);
        const type = (byte0 >> 6) & 0b11;
        const isPlain = (!type) || type === 0b11;
        const isLen = type === 0b01;
        let len = (byte0 >> 4) & 0b11;
        let count = byte0 & 0b1111;
        let pixel = 0;
        if (isPlain) {
            if (type) {
                pixel = 0xFF;
            }
        }
        else if (isLen) {
            pixel = buffer.readUint8(offset++);
        }
        else {
            pixel = prev + ((len > 1) ? -count : count);
            count = (len % 1) ? buffer.readUint8(offset++) : 0;
            len = 0;
        }
        if (len) {
            let added = 0;
            while (len-- > 0) {
                added = (added << 8) | buffer.readUint8(offset++);
            }
            count |= added << 4;
        }
        consume(pixel, count);
    }
    flush(false);
    return Buffer.concat(arrays);
};