mildsunrise · April 28, 2025 07:49 · pasthev · Feb 26, 2025 · pasthev · Mar 3, 2025
diff --git a/README.md b/README.md
diff --git a/tuya.py b/tuya.py
 import io
 import base64
 from bisect import bisect
 from struct import pack, unpack


 # MAIN API

 def decode_ir(code: str) -> list[int]:
 	'''
 	Decodes an IR code string from a Tuya blaster.
 	Returns the IR signal as a list of µs durations,
 	with the first duration belonging to a high state.
 	'''
 	payload = base64.decodebytes(code.encode('ascii'))
 	payload = decompress(io.BytesIO(payload))

 	signal = []
 	while payload:
 		assert len(payload) >= 2, \
 			f'garbage in decompressed payload: {payload.hex()}'
 		signal.append(unpack('<H', payload[:2])[0])
 		payload = payload[2:]
 	return signal

 def encode_ir(signal: list[int], compression_level=2) -> str:
 	'''
 	Encodes an IR signal (see `decode_tuya_ir`)
 	into an IR code string for a Tuya blaster.
 	'''
 	payload = b''.join(pack('<H', t) for t in signal)
 	compress(out := io.BytesIO(), payload, compression_level)
 	payload = out.getvalue()
 	return base64.encodebytes(payload).decode('ascii').replace('\n', '')


 # DECOMPRESSION

 def decompress(inf: io.FileIO) -> bytes:
 	'''
 	Reads a "Tuya stream" from a binary file,
 	and returns the decompressed byte string.
 	'''
 	out = bytearray()

 	while (header := inf.read(1)):
 		L, D = header[0] >> 5, header[0] & 0b11111
 		if not L:
 			# literal block
 			L = D + 1
 			data = inf.read(L)
 			assert len(data) == L
 		else:
 			# length-distance pair block
 			if L == 7:
 				L += inf.read(1)[0]
 			L += 2
 			D = (D << 8 | inf.read(1)[0]) + 1
                        assert len(out) >= D
 			data = bytearray()
 			while len(data) < L:
 				data.extend(out[-D:][:L-len(data)])
 		out.extend(data)

 	return bytes(out)


 # COMPRESSION

 def emit_literal_blocks(out: io.FileIO, data: bytes):
 	for i in range(0, len(data), 32):
 		emit_literal_block(out, data[i:i+32])

 def emit_literal_block(out: io.FileIO, data: bytes):
 	length = len(data) - 1
 	assert 0 <= length < (1 << 5)
 	out.write(bytes([length]))
 	out.write(data)

 def emit_distance_block(out: io.FileIO, length: int, distance: int):
 	distance -= 1
 	assert 0 <= distance < (1 << 13)
 	length -= 2
 	assert length > 0
 	block = bytearray()
 	if length >= 7:
 		assert length - 7 < (1 << 8)
 		block.append(length - 7)
 		length = 7
 	block.insert(0, length << 5 | distance >> 8)
 	block.append(distance & 0xFF)
 	out.write(block)

 def compress(out: io.FileIO, data: bytes, level=2):
 	'''
 	Takes a byte string and outputs a compressed "Tuya stream".

 	Implemented compression levels:
 	0 - copy over (no compression, 3.1% overhead)
 	1 - eagerly use first length-distance pair found (linear)
 	2 - eagerly use best length-distance pair found
 	3 - optimal compression (n^3)
 	'''
 	if level == 0:
 		return emit_literal_blocks(out, data)

 	W = 2**13 # window size
 	L = 255+9 # maximum length
 	distance_candidates = lambda: range(1, min(pos, W) + 1)

 	def find_length_for_distance(start: int) -> int:
 		length = 0
 		limit = min(L, len(data) - pos)
 		while length < limit and data[pos + length] == data[start + length]:
 			length += 1
 		return length
 	find_length_candidates = lambda: \
 		( (find_length_for_distance(pos - d), d) for d in distance_candidates() )
 	find_length_cheap = lambda: \
 		next((c for c in find_length_candidates() if c[0] >= 3), None)
 	find_length_max = lambda: \
 		max(find_length_candidates(), key=lambda c: (c[0], -c[1]), default=None)

 	if level >= 2:
 		suffixes = []; next_pos = 0
 		key = lambda n: data[n:]
 		find_idx = lambda n: bisect(suffixes, key(n), key=key)
 		def distance_candidates():
 			nonlocal next_pos
 			while next_pos <= pos:
 				if len(suffixes) == W:
 					suffixes.pop(find_idx(next_pos - W))
 				suffixes.insert(idx := find_idx(next_pos), next_pos)
 				next_pos += 1
 			idxs = (idx+i for i in (+1,-1)) # try +1 first
 			return (pos - suffixes[i] for i in idxs if 0 <= i < len(suffixes))

 	if level <= 2:
 		find_length = { 1: find_length_cheap, 2: find_length_max }[level]
 		block_start = pos = 0
 		while pos < len(data):
 			if (c := find_length()) and c[0] >= 3:
 				emit_literal_blocks(out, data[block_start:pos])
 				emit_distance_block(out, c[0], c[1])
 				pos += c[0]
 				block_start = pos
 			else:
 				pos += 1
 		emit_literal_blocks(out, data[block_start:pos])
 		return

 	# use topological sort to find shortest path
 	predecessors = [(0, None, None)] + [None] * len(data)
 	def put_edge(cost, length, distance):
 		npos = pos + length
 		cost += predecessors[pos][0]
 		current = predecessors[npos]
 		if not current or cost < current[0]:
 			predecessors[npos] = cost, length, distance
 	for pos in range(len(data)):
 		if c := find_length_max():
 			for l in range(3, c[0] + 1):
 				put_edge(2 if l < 9 else 3, l, c[1])
 		for l in range(1, min(32, len(data) - pos) + 1):
 			put_edge(1 + l, l, 0)

 	# reconstruct path, emit blocks
 	blocks = []; pos = len(data)
 	while pos > 0:
 		_, length, distance = predecessors[pos]
 		pos -= length
 		blocks.append((pos, length, distance))
 	for pos, length, distance in reversed(blocks):
 		if not distance:
 			emit_literal_block(out, data[pos:pos + length])
 		else:
 			emit_distance_block(out, length, distance)
	import io
	import base64
	from bisect import bisect
	from struct import pack, unpack


	# MAIN API

	def decode_ir(code: str) -> list[int]:
	'''
	Decodes an IR code string from a Tuya blaster.
	Returns the IR signal as a list of µs durations,
	with the first duration belonging to a high state.
	'''
	payload = base64.decodebytes(code.encode('ascii'))
	payload = decompress(io.BytesIO(payload))

	signal = []
	while payload:
	assert len(payload) >= 2, \
	f'garbage in decompressed payload: {payload.hex()}'
	signal.append(unpack('<H', payload[:2])[0])
	payload = payload[2:]
	return signal

	def encode_ir(signal: list[int], compression_level=2) -> str:
	'''
	Encodes an IR signal (see `decode_tuya_ir`)
	into an IR code string for a Tuya blaster.
	'''
	payload = b''.join(pack('<H', t) for t in signal)
	compress(out := io.BytesIO(), payload, compression_level)
	payload = out.getvalue()
	return base64.encodebytes(payload).decode('ascii').replace('\n', '')


	# DECOMPRESSION

	def decompress(inf: io.FileIO) -> bytes:
	'''
	Reads a "Tuya stream" from a binary file,
	and returns the decompressed byte string.
	'''
	out = bytearray()

	while (header := inf.read(1)):
	L, D = header[0] >> 5, header[0] & 0b11111
	if not L:
	# literal block
	L = D + 1
	data = inf.read(L)
	assert len(data) == L
	else:
	# length-distance pair block
	if L == 7:
	L += inf.read(1)[0]
	L += 2
	D = (D << 8 \| inf.read(1)[0]) + 1
	assert len(out) >= D
	data = bytearray()
	while len(data) < L:
	data.extend(out[-D:][:L-len(data)])
	out.extend(data)

	return bytes(out)


	# COMPRESSION

	def emit_literal_blocks(out: io.FileIO, data: bytes):
	for i in range(0, len(data), 32):
	emit_literal_block(out, data[i:i+32])

	def emit_literal_block(out: io.FileIO, data: bytes):
	length = len(data) - 1
	assert 0 <= length < (1 << 5)
	out.write(bytes([length]))
	out.write(data)

	def emit_distance_block(out: io.FileIO, length: int, distance: int):
	distance -= 1
	assert 0 <= distance < (1 << 13)
	length -= 2
	assert length > 0
	block = bytearray()
	if length >= 7:
	assert length - 7 < (1 << 8)
	block.append(length - 7)
	length = 7
	block.insert(0, length << 5 \| distance >> 8)
	block.append(distance & 0xFF)
	out.write(block)

	def compress(out: io.FileIO, data: bytes, level=2):
	'''
	Takes a byte string and outputs a compressed "Tuya stream".

	Implemented compression levels:
	0 - copy over (no compression, 3.1% overhead)
	1 - eagerly use first length-distance pair found (linear)
	2 - eagerly use best length-distance pair found
	3 - optimal compression (n^3)
	'''
	if level == 0:
	return emit_literal_blocks(out, data)

	W = 2**13 # window size
	L = 255+9 # maximum length
	distance_candidates = lambda: range(1, min(pos, W) + 1)

	def find_length_for_distance(start: int) -> int:
	length = 0
	limit = min(L, len(data) - pos)
	while length < limit and data[pos + length] == data[start + length]:
	length += 1
	return length
	find_length_candidates = lambda: \
	( (find_length_for_distance(pos - d), d) for d in distance_candidates() )
	find_length_cheap = lambda: \
	next((c for c in find_length_candidates() if c[0] >= 3), None)
	find_length_max = lambda: \
	max(find_length_candidates(), key=lambda c: (c[0], -c[1]), default=None)

	if level >= 2:
	suffixes = []; next_pos = 0
	key = lambda n: data[n:]
	find_idx = lambda n: bisect(suffixes, key(n), key=key)
	def distance_candidates():
	nonlocal next_pos
	while next_pos <= pos:
	if len(suffixes) == W:
	suffixes.pop(find_idx(next_pos - W))
	suffixes.insert(idx := find_idx(next_pos), next_pos)
	next_pos += 1
	idxs = (idx+i for i in (+1,-1)) # try +1 first
	return (pos - suffixes[i] for i in idxs if 0 <= i < len(suffixes))

	if level <= 2:
	find_length = { 1: find_length_cheap, 2: find_length_max }[level]
	block_start = pos = 0
	while pos < len(data):
	if (c := find_length()) and c[0] >= 3:
	emit_literal_blocks(out, data[block_start:pos])
	emit_distance_block(out, c[0], c[1])
	pos += c[0]
	block_start = pos
	else:
	pos += 1
	emit_literal_blocks(out, data[block_start:pos])
	return

	# use topological sort to find shortest path
	predecessors = [(0, None, None)] + [None] * len(data)
	def put_edge(cost, length, distance):
	npos = pos + length
	cost += predecessors[pos][0]
	current = predecessors[npos]
	if not current or cost < current[0]:
	predecessors[npos] = cost, length, distance
	for pos in range(len(data)):
	if c := find_length_max():
	for l in range(3, c[0] + 1):
	put_edge(2 if l < 9 else 3, l, c[1])
	for l in range(1, min(32, len(data) - pos) + 1):
	put_edge(1 + l, l, 0)

	# reconstruct path, emit blocks
	blocks = []; pos = len(data)
	while pos > 0:
	_, length, distance = predecessors[pos]
	pos -= length
	blocks.append((pos, length, distance))
	for pos, length, distance in reversed(blocks):
	if not distance:
	emit_literal_block(out, data[pos:pos + length])
	else:
	emit_distance_block(out, length, distance)