Version 5.0 The LEDA User Manual

9.7 Adaptive Huffman Coder ( AdaptiveHuffman-
Coder )
1. Definition
The class AdaptiveHuffmanCoder provides an adaptive coder based on the algorithm by
J.S. Vitter [87]. Vitter has proven that his algorithm achieves the best compression among
all one-pass Huffman schemes.
#include < LEDA/coding/huffman.h >
2. Creation
AdaptiveHuffmanCoder C(streambuf ∗ src stream = 0, streambuf ∗ tgt stream = 0,
bool own streams = false);
creates an instance C which uses the given source and target
streams. If own streams is set, then C is responsible for the destruction
of the streams, otherwise the pointers src stream and tgt stream
must be valid during the life-time of C.
AdaptiveHuffmanCoder
3. Operations
Standard Operations
C(const char ∗ src file name, const char ∗ tgt file name);
creates an instance C which uses file-streams for input and output.
void C.encode( ) encodes the source stream and writes the output to
the target stream.
void C.decode( ) decodes the source stream and writes the output to
the target stream.
uint32 C.encode memory chunk(const char ∗ in buf , uint32 in len, char ∗ out buf ,
uint32 out len)
encodes the memory chunk starting at in buf with
size in len into the buffer starting at out buf with size
out len. The function returns actual length of the
encoded chunk which may be smaller than out len. If
the output buffer is too small for the encoded data
the failure flag will be set (see below).
uint32 C.decode memory chunk(const char ∗ in buf , uint32 in len, char ∗ out buf ,
uint32 out len)
decodes a memory chunk. The meaning of the parameters
and the return value is the same as in the
previous function.