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///////////////////////////////////////////////////////////////////////////////
//
/// \file chunk_size.c
/// \brief Finds out the minimal reasonable chunk size for a filter chain
//
// Author: Lasse Collin
//
// This file has been put into the public domain.
// You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////
#include "common.h"
/**
* \brief Finds out the minimal reasonable chunk size for a filter chain
*
* This function helps determining the Uncompressed Sizes of the Blocks when
* doing multi-threaded encoding.
*
* When compressing a large file on a system having multiple CPUs or CPU
* cores, the file can be split into smaller chunks, that are compressed
* independently into separate Blocks in the same .lzma Stream.
*
* \return Minimum reasonable Uncompressed Size of a Block. The
* recommended minimum Uncompressed Size is between this value
* and the value times two.
Zero if the Uncompressed Sizes of Blocks don't matter
*/
extern LZMA_API(size_t)
lzma_chunk_size(const lzma_options_filter *filters)
{
while (filters->id != LZMA_VLI_UNKNOWN) {
switch (filters->id) {
// TODO LZMA_FILTER_SPARSE
case LZMA_FILTER_COPY:
case LZMA_FILTER_SUBBLOCK:
case LZMA_FILTER_X86:
case LZMA_FILTER_POWERPC:
case LZMA_FILTER_IA64:
case LZMA_FILTER_ARM:
case LZMA_FILTER_ARMTHUMB:
case LZMA_FILTER_SPARC:
// These are very fast, thus there is no point in
// splitting the data into smaller blocks.
break;
case LZMA_FILTER_LZMA1:
// The block sizes of the possible next filters in
// the chain are irrelevant after the LZMA filter.
return ((lzma_options_lzma *)(filters->options))
->dictionary_size;
default:
// Unknown filters
return 0;
}
++filters;
}
// Indicate that splitting would be useless.
return SIZE_MAX;
}
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