a JS unpacker for an odd container format used in google snake & minesweeper

bingle2.mjs

import {readFile, writeFile} from "fs"

function read_bin(index, block_size = 314, file_buffer) {
	const use_u16 = !file_buffer[0]
	const track_buffers = {}, odd_block_idxs = {}, even_block_idxs = {}
	let total_odd_idxs = 0

	// track block indices table
	Object.entries(index).forEach(([key, idx]) => {
		let num_odd_idxs = file_buffer[idx]
		if (use_u16) num_odd_idxs |= file_buffer[++idx] << 8
		total_odd_idxs += num_odd_idxs

		odd_block_idxs[key] = []
		for (var _ = 0; _ < num_odd_idxs; _++) {
			let block_idx = file_buffer[++idx]
			if (use_u16) block_idx |= file_buffer[++idx] << 8
			odd_block_idxs[key].push(block_idx)
		}

		even_block_idxs[key] = []
		for (_ = 0; _ < num_odd_idxs; _++) {
			let block_idx = file_buffer[++idx]
			if (use_u16) block_idx |= file_buffer[++idx] << 8
			even_block_idxs[key].push(block_idx)
		}
	})

	let index_table_end = total_odd_idxs * 2 + Object.keys(index).length
	if (use_u16) index_table_end *= 2, index_table_end += 2
	let last_block_idx = file_buffer[index_table_end++]
	if (use_u16) last_block_idx |= file_buffer[index_table_end++] << 8

	// track data blocks
	Object.keys(index).forEach(key => {
		let buffer_size = 0
		odd_block_idxs[key].forEach(block_idx => {
			const block_align_offset = ~(file_buffer[index_table_end + block_idx * 32 + 2] & 2)
			buffer_size += block_size - block_align_offset
		})

		track_buffers[key] = new ArrayBuffer(buffer_size)
		const track_buffer = new Uint8Array(track_buffers[key])
		let track_buffer_idx = 0

		for (let idx = 0; idx < odd_block_idxs[key].length; idx++) {
		  	const odd_block_idx = index_table_end + odd_block_idxs[key][idx] * 32,
		  	even_block_idx = index_table_end + last_block_idx * 32 + even_block_idxs[key][idx] * (block_size - 32),
			corr_block_size = block_size - !(file_buffer[odd_block_idx + 2] & 2)

			const odd_block = file_buffer.subarray(odd_block_idx, odd_block_idx + 32)
			const even_block = file_buffer.subarray(even_block_idx, even_block_idx + corr_block_size - 32)

		  	track_buffer.set(odd_block, track_buffer_idx)
		  	track_buffer.set(even_block, track_buffer_idx + 32)
			track_buffer_idx += corr_block_size
		}
	})

	return track_buffers
}

readFile("./in/game_audio.bin", (err, file_buffer) => {
	if (err) throw err

	const final_obj = read_bin({
		BIG_DIG: 2,
		DIG_REVEAL_1: 116,
		DIG_REVEAL_2: 170,
		DIG_REVEAL_3: 224,
		DIG_REVEAL_4: 282,
		DIG_REVEAL_5: 352,
		DIG_REVEAL_6: 422,
		DIG_REVEAL_7: 496,
		DIG_REVEAL_8: 574,
		MINE_1: 656,
		MINE_2: 802,
		MINE_3: 940,
		MINE_4: 1074,
		MINE_5: 1200,
		PLANT_FLAG: 1370,
		UNPLANT_FLAG: 1444
	}, 385, file_buffer)

	Object.keys(final_obj).forEach(key => {
		writeFile(`./out/${key}.bin`, new Uint8Array(final_obj[key]), err => {
			if (err) throw err
		})
	})
})