mirror of https://git.tukaani.org/xz.git
75 lines
2.3 KiB
C
75 lines
2.3 KiB
C
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///////////////////////////////////////////////////////////////////////////////
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//
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/// \file chunk_size.c
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/// \brief Finds out the minimal reasonable chunk size for a filter chain
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//
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// Copyright (C) 2007 Lasse Collin
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//
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// This library is free software; you can redistribute it and/or
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// modify it under the terms of the GNU Lesser General Public
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// License as published by the Free Software Foundation; either
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// version 2.1 of the License, or (at your option) any later version.
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//
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// Lesser General Public License for more details.
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//
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///////////////////////////////////////////////////////////////////////////////
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#include "common.h"
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/**
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* \brief Finds out the minimal reasonable chunk size for a filter chain
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*
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* This function helps determining the Uncompressed Sizes of the Blocks when
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* doing multi-threaded encoding.
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*
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* When compressing a large file on a system having multiple CPUs or CPU
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* cores, the file can be splitted in smaller chunks, that are compressed
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* independently into separate Blocks in the same .lzma Stream.
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*
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* \return Minimum reasonable Uncompressed Size of a Block. The
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* recommended minimum Uncompressed Size is between this value
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* and the value times two.
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Zero if the Uncompressed Sizes of Blocks don't matter
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*/
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extern LZMA_API size_t
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lzma_chunk_size(const lzma_options_filter *filters)
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{
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while (filters->id != LZMA_VLI_VALUE_UNKNOWN) {
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switch (filters->id) {
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// TODO LZMA_FILTER_SPARSE
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case LZMA_FILTER_COPY:
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case LZMA_FILTER_SUBBLOCK:
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case LZMA_FILTER_X86:
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case LZMA_FILTER_POWERPC:
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case LZMA_FILTER_IA64:
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case LZMA_FILTER_ARM:
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case LZMA_FILTER_ARMTHUMB:
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case LZMA_FILTER_SPARC:
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// These are very fast, thus there is no point in
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// splitting the data in smaller blocks.
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break;
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case LZMA_FILTER_LZMA:
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// The block sizes of the possible next filters in
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// the chain are irrelevant after the LZMA filter.
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return ((lzma_options_lzma *)(filters->options))
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->dictionary_size;
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default:
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// Unknown filters
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return 0;
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}
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++filters;
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}
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// Indicate that splitting would be useless.
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return SIZE_MAX;
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}
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