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/*
* Run-length encoding (RLE) is a very simple form of data compression
* in which runs of data (that is, sequences in which the same data value
* occurs in many consecutive data elements) are stored as a single data
* value and count, rather than as the original run. This is most useful
* on data that contains many such runs: for example, simple graphic
* images such as icons, line drawings, and animations. It is not useful
* with files that don't have many runs as it could slightly increase the
* output size.
* ALGORITHM: This algorithm is an optimized version of the traditional
* RLE algorithm in that it behaves better with very few runs.
*
* With a run of a character where that run is >= 3 this is
* replaced with the repeat indicator 0X80 and then the repeat count OR'd
* over this ident. This repeat count therefore has a maximum value
* of 127 (0x7F) which is to be interpreted as the next character repeated
* another 'repeat count' times (i.e. a maximum of 128 characters can be
* represented in any single dupal). if the repeat ident is not present
* then the count is to be interpreted as a copy of the next repeat count
* characters + 1.
*
* EXAMPLE: the following arbitary string of 67 bytes:-
* WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW
* will produce (as a HEXDUMP) of 14 bytes
* 8B 57 00 42 8B 57 82 42 97 57 00 42 8D 57 .W.B.W.B.W.B.W
*/
#include "RLECompressor.h"
#include "ace/Compression/rle/RLECompressor.h"
TAO_BEGIN_VERSIONED_NAMESPACE_DECL
namespace TAO
{
RLECompressor::RLECompressor(::Compression::CompressorFactory_ptr compressor_factory)
: BaseCompressor (compressor_factory, 0)
{
}
void
RLECompressor::compress(const ::Compression::Buffer &source, ::Compression::Buffer &target)
{
// Ensure maximum is at least X 1.1 input length.
target.length(static_cast<CORBA::ULong>((source.length() * 1.1) + 32U));
ACE_UINT64 out_len = ACE_RLECompression::instance()->compress( source.get_buffer(),
source.length(),
target.get_buffer(),
target.maximum() );
if (ACE_UINT64(-1) == out_len) { // Overrun
throw ::Compression::CompressionException();
}
target.length(static_cast< CORBA::ULong>(out_len)); // Set Output Buffer to the right size now.
// Update statistics for this compressor
this->update_stats(source.length(), target.length());
}
void
RLECompressor::decompress(const ::Compression::Buffer &source, ::Compression::Buffer &target)
{
ACE_UINT64 out_len = ACE_RLECompression::instance()->decompress(source.get_buffer(),
source.length(),
target.get_buffer(),
target.maximum() );
if (ACE_UINT64(-1) == out_len) { // Overrun
throw ::Compression::CompressionException();
}
target.length(static_cast<CORBA::ULong>(out_len));
}
}
TAO_END_VERSIONED_NAMESPACE_DECL
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