bitmap

Bits ↔ bytes conversion. LSB-first per byte (bit 0 = least significant bit).

Module bitmap | Source packages/front/fw/src/io/utils/bitmap.js | Deps none | Worker-safe yes

Resolve

const bitmap = runtime.resolve('bitmap');
// Returns: { bytesToBits, bitsToBytes, padBitsToByte }

API

bitmap.bytesToBits(ui8a)

LSB-first: byte 0b00000011 = [1,1,0,0,0,0,0,0]

bitmap.bytesToBits(new Uint8Array([3]));    // [1,1,0,0,0,0,0,0]
bitmap.bytesToBits(new Uint8Array([255]));  // [1,1,1,1,1,1,1,1]
bitmap.bytesToBits(new Uint8Array([1,2]));  // [1,0,0,0,0,0,0,0, 0,1,0,0,0,0,0,0]

bitmap.bitsToBytes(ba, ret?, validate?)

bitmap.bitsToBytes([1,1,0,0,0,0,0,0]);         // Uint8Array [3]
bitmap.bitsToBytes([0,1,0,0,0,0,0,0]);         // Uint8Array [2]

// Strict length validation
bitmap.bitsToBytes([1,0,0,0,0,0,0], null, true); // throws — length 7

bitmap.padBitsToByte(arr)

Modifies arr in place and returns it:

const bits = [1, 0, 1]; // length 3
bitmap.padBitsToByte(bits); // → [1, 0, 1, 0, 0, 0, 0, 0] (5 zeros added)

Examples

const bitmap = runtime.resolve('bitmap');

// Round-trip
const bytes = new Uint8Array([42, 255, 0]);
const bits  = bitmap.bytesToBits(bytes);
bitmap.padBitsToByte(bits); // ensure multiple of 8
const back  = bitmap.bitsToBytes(bits);
// back ≡ bytes

Worker Usage

const worker = fw.createWorker(
    function ({ libs, args }) {
        const bits = libs.bitmap.bytesToBits(args.bytes);
        libs.bitmap.padBitsToByte(bits);
        const back = libs.bitmap.bitsToBytes(bits);
        self.postMessage(back);
    },
    { dependencies: ['bitmap'], args: { bytes: new Uint8Array([42, 255]) } }
);

Notes

• LSB-first order: bit 0 (least significant) is the first element of the array.
• padBitsToByte: no-op if length is already a multiple of 8.
• bitsToBytes with validate=true: throws if length is not a multiple of 8.
• Pre-computed lookup table (256 entries) for conversions.

See also

• ui8 — general Uint8Array utilities