Version 5.0 The LEDA User Manual

9.12 RLE for Runs of Zero ( RLE0Coder )
1. Definition
The class RLE0Coder is designed for compressing inputs which contain many runs of the
character 0x00 . This coder is useful as a preprocessing stage for a Move-To-Front coder.
(This stage was suggested by D.J. Wheeler and described by P. Fenwick [32].)
The following combinations of coders often yield very good compression results:
• CoderPipe4
• CoderPipe4
#include < LEDA/coding/RLE0.h >
2. Creation
RLE0Coder 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.
RLE0Coder
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).