Method to decode variable length codes with regular bit pattern prefixes

Abstract

Decoding variable length codes having regular bit pattern prefixes enables faster decoding of variable length codes, especially in systems that provide bit or bit mask search capabilities. An embodiment of the present invention determines a code prefix type, and calculates a length of the code prefix. A first data structure may be provided to associate the maximal number of bits in a variable length code with the length of the code prefix, and to locate further decoding data in accordance with the prefix length and type. A bit stream may be read according to the maximal length obtained. An additional data structure may be provided to retrieve a decoded value and the actual length of a variable length code being decoded. This data structure may be indexed with the value of the bit combination read from the bit stream. In case the actual length of the variable length code is less than the maximal length, the excess bits may be returned to the bit stream.