Version 5.0 The LEDA User Manual

9.6 Static Huffman Coder ( HuffmanCoder )
1. Definition
The class HuffmanCoder provides a static coder based on the algorithm by Huffman [48].
The term static means that a fixed model is used for encoding. The input is scanned
twice. In the first scan the frequencies of the characters are counted. This information is
used to precompute the Huffman-trees. The actual coding takes place in a second scan.
#include < LEDA/coding/huffman.h >
2. Creation
HuffmanCoder 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.
HuffmanCoder
C(const char ∗ src file name, const char ∗ tgt file name);
creates an instance C which uses file-streams for input and output.
3. Operations
Standard Operations
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.