Low-Overhead COBS Encoder

low-overhead-cobs.py

#COBS encoder using minimal buffer instead of encoding entire buffer at once
#Passes unit tests from Wikipedia page
class cobsEncoder:
	def __init__(self):
		self.cobsBuffer = b''
		self.postZero = False

	def encode(self,data):
		for d in data:
			if d == b'\x00':
				yield len(self.cobsBuffer)+1
				
				for c in self.cobsBuffer:
					yield ord(c)
				self.cobsBuffer = b''
				self.postZero = True

			else:
				self.cobsBuffer = self.cobsBuffer + d
				self.postZero = False
				if len(self.cobsBuffer) == 0xFE:
					yield 0xFF
					for c in self.cobsBuffer:
						yield ord(c)
					self.cobsBuffer = b''


	def flush(self):
		if len(self.cobsBuffer) > 0:
			yield len(self.cobsBuffer) + 1
			for c in self.cobsBuffer:
				yield ord(c)
		
		if self.postZero:
			yield 1

		self.cobsBuffer = b''
	
	def encodeAndFlush(self, data):
		for c in self.encode(data):
			yield c
		for c in self.flush():
			yield c

def encodeAndPrint(data):
	c = cobsEncoder()
	for x in c.encodeAndFlush(data):
		print hex(x),
	print ''

def encodeAndPrintRange(start,stop):
	c = cobsEncoder()
	for b in range(start,stop+1):
		for x in c.encode(b''+chr(b)):
			print hex(x),
	for x in c.flush():
		print hex(x),
	print ''
	print ''
	
def encodeAndPrintList(l):
	c = cobsEncoder()
	for b in l:
		for x in c.encode(b''+chr(b)):
			print hex(x),
	for x in c.flush():
		print hex(x),
	print ''
	print ''

encodeAndPrint(b'\x00')
encodeAndPrint(b'\x00\x00')
encodeAndPrint(b'\x11\x22\x00\x33')
encodeAndPrint(b'\x11\x22\x33\x44')
encodeAndPrint(b'\x11\x00\x00\x00')
encodeAndPrintRange(0x01, 0xFE )
encodeAndPrintRange(0x00, 0xFE )
encodeAndPrintRange(0x01, 0xFF )
encodeAndPrintList( range(0x02,0x100) + range(1) )
encodeAndPrintList( range(0x03,0x100) + range(2) )