readVariableLengthInteger

from:
https://code.google.com/p/blockchain/source/browse/trunk/BlockChain.cpp

inline uint32_t readVariableLengthInteger(void)
	{
		uint32_t ret = 0;

		uint8_t v = readU8();
		if ( v < 0xFD ) // If it's less than 0xFD use this value as the unsigned integer
		{
			ret = (uint32_t)v;
		}
		else
		{
			uint16_t v = readU16();
			if ( v < 0xFFFF )
			{
				ret = (uint32_t)v;
			}
			else
			{
				uint32_t v = readU32();
				if ( v < 0xFFFFFFFF )
				{
					ret = (uint32_t)v;
				}
				else
				{
					assert(0); // never expect to actually encounter a 64bit integer in the block-chain stream; it's outside of any reasonable expected value
					uint64_t v = readU64();
					ret = (uint32_t)v;
				}
			}
		}
		return ret;
	}