Version 5.0 The LEDA User Manual

9.8 Run-Length Coder ( RLECoder )
1. Definition
A Run-Length coder is used for compressing inputs which contain many long sequences
of repeating characters. The basic idea is as follows: A sequence aaaaaaa of 7 consecutive
a’s is replaced by something like a#7.
We provide two schemes for the actual encoding of the compressed sequence, which allows
the user to select between fast or high compression.
#include < LEDA/coding/RLE.h >
2. Creation
RLECoder C(streambuf ∗ src stream = 0, streambuf ∗ tgt stream = 0,
bool own streams = false, bool fast mode = true);
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. The parameter fast mode
allows to select fast or high compression mode.
RLECoder
C(const char ∗ src file name, const char ∗ tgt file name,
bool fast mode = true);
creates an instance C which uses file-streams for input and output.
The parameter fast mode allows to select fast or high compression
mode.
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).