varint.py

# Varint decoding: https://developers.google.com/protocol-buffers/docs/encoding
import struct

def readVarint(f):
	multiplier = 1
	value = 0
	b = 0xff
	while b & 128:
		b = struct.unpack('B', f.read(1))[0]
		value += multiplier * (b & 127)
		multiplier *= 128
	return value

def readSignedVarintArray(f, n):
	buf = bytearray(n * 4)
	for i in range(n):
		value = readVarint(f)
		value = value >> 1 ^ - (1 & value)  # varint special sign managment
		struct.pack_into("i", buf, i * 4, value)
	return bytes(buf)

def readUnsignedVarintArray(f, n):
	buf = bytearray(n * 4)
	for i in range(n):
		value = readVarint(f)
		struct.pack_into("I", buf, i * 4, value)
	return bytes(buf)