Function writeFrame

packages/melonjs/tests/aseprite-parser.spec.js:191–228

(w, { duration }, bodyFn)

// write a frame header with the given chunk-emitting body fn
// bodyFn may be async (e.g. when emitting compressed cels via zlib)
async function writeFrame(w, { duration }, bodyFn) {
	const frameStart = w.length;
	w.u32(0); // frame size — patched
	w.u16(0xf1fa); // frame magic
	w.u16(0xffff); // old chunks count: 0xFFFF means "use the 32-bit field below"
	w.u16(duration);
	w.zeros(2);
	const chunkCountOffset = w.length;
	w.u32(0); // new chunks count — patched

	let chunkCount = 0;
	await bodyFn({
		layer: (name) => {
			writeLayerChunk(w, name);
			chunkCount++;
		},
		rawCel: (opts) => {
			writeRawCelChunk(w, opts);
			chunkCount++;
		},
		linkedCel: (opts) => {
			writeLinkedCelChunk(w, opts);
			chunkCount++;
		},
		compressedCel: async (opts) => {
			await writeCompressedCelChunk(w, opts);
			chunkCount++;
		},
		tags: (tags) => {
			writeTagsChunk(w, tags);
			chunkCount++;
		},
	});

	const end = w.length;
	patchU32WriterPart(w, frameStart, end - frameStart);
	patchU32WriterPart(w, chunkCountOffset, chunkCount);
}

// the writer holds Uint8Array parts before we concat to a buffer, so an
// in-place patch must walk the parts list and mutate the right one. We could