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Work on low-level version of compression.

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This commit is contained in:
Daviw Williams 2013-02-22 17:03:47 +01:00
parent eb8ace0c54
commit 81eab0ebfb
2 changed files with 38 additions and 16 deletions
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10
library/PolyVoxCore/include/PolyVoxCore/MinizCompressor.h
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@ -8,12 +8,20 @@ namespace PolyVox
class MinizCompressor : public Compressor
{
public:
MinizCompressor();
MinizCompressor(int iCompressionLevel = 6); // Miniz defines MZ_DEFAULT_LEVEL = 6 so we use the same here
~MinizCompressor();
uint32_t getMaxCompressedSize(uint32_t uUncompressedInputSize);
uint32_t compress(void* pSrcData, uint32_t uSrcLength, void* pDstData, uint32_t uDstLength);
uint32_t decompress(void* pSrcData, uint32_t uSrcLength, void* pDstData, uint32_t uDstLength);
private:
int m_iCompressionLevel;
// tdefl_compressor contains all the state needed by the low-level compressor so it's a pretty big struct (~300k).
// We're storing it by void* because miniz does not supply a header and we don't want to include the .c file from
// here as it will cause linker problems.
void* g_deflator;
};
}

44
library/PolyVoxCore/source/MinizCompressor.cpp
View File

@ -5,9 +5,9 @@
#define MINIZ_NO_STDIO
#define MINIZ_NO_ARCHIVE_APIS
#define MINIZ_NO_TIME
//#define MINIZ_NO_ZLIB_APIS
#define MINIZ_NO_ZLIB_APIS
#define MINIZ_NO_ZLIB_COMPATIBLE_NAMES
//#define MINIZ_NO_MALLOC
#define MINIZ_NO_MALLOC
#include "PolyVoxCore/Impl/ErrorHandling.h"
// For some unknown reason the miniz library is supplied only as a
@ -21,19 +21,32 @@ using namespace std;
namespace PolyVox
{
MinizCompressor::MinizCompressor()
// Compression levels: 0-9 are the standard zlib-style levels, 10 is best possible compression (not zlib compatible, and may be very slow)
MinizCompressor::MinizCompressor(int iCompressionLevel)
:m_iCompressionLevel(iCompressionLevel)
,g_deflator(0)
{
tdefl_compressor* pDeflator = new tdefl_compressor;
g_deflator = reinterpret_cast<void*>(pDeflator);
}
MinizCompressor::~MinizCompressor()
{
tdefl_compressor* pDeflator = reinterpret_cast<tdefl_compressor*>(g_deflator);
delete pDeflator;
}
uint32_t MinizCompressor::getMaxCompressedSize(uint32_t uUncompressedInputSize)
{
return static_cast<uint32_t>(mz_compressBound(static_cast<mz_ulong>(uUncompressedInputSize)));
// The contents of this function are copied from miniz's 'mz_deflateBound()'
// (which we can't use because it is part of the zlib-style higher level API).
unsigned long source_len = uUncompressedInputSize;
// This is really over conservative. (And lame, but it's actually pretty tricky to compute a true upper bound given the way tdefl's blocking works.)
return MZ_MAX(128 + (source_len * 110) / 100, 128 + source_len + ((source_len / (31 * 1024)) + 1) * 5);
}
// The commented out function is left here for reference and debugging purposes.
/*uint32_t MinizCompressor::compress(void* pSrcData, uint32_t uSrcLength, void* pDstData, uint32_t uDstLength)
{
mz_ulong ulDstLength = uDstLength;
@ -51,24 +64,23 @@ namespace PolyVox
return ulDstLength;
}*/
// The behaviour of this function should be the same as the commented out version above (except that it requires the destination to be a power of two),
// but it's implemented using the lower level API which does not conflict with zlib or perform any memory allocations.
uint32_t MinizCompressor::compress(void* pSrcData, uint32_t uSrcLength, void* pDstData, uint32_t uDstLength)
{
int level = 9;
// tdefl_compressor contains all the state needed by the low-level compressor so it's a pretty big struct (~300k).
// This example makes it a global vs. putting it on the stack, of course in real-world usage you'll probably malloc() or new it.
tdefl_compressor g_deflator;
tdefl_compressor* pDeflator = reinterpret_cast<tdefl_compressor*>(g_deflator);
// The number of dictionary probes to use at each compression level (0-10). 0=implies fastest/minimal possible probing.
static const mz_uint s_tdefl_num_probes[11] = { 0, 1, 6, 32, 16, 32, 128, 256, 512, 768, 1500 };
// create tdefl() compatible flags (we have to compose the low-level flags ourselves, or use tdefl_create_comp_flags_from_zip_params() but that means MINIZ_NO_ZLIB_APIS can't be defined).
mz_uint comp_flags = TDEFL_WRITE_ZLIB_HEADER | s_tdefl_num_probes[MZ_MIN(10, level)] | ((level <= 3) ? TDEFL_GREEDY_PARSING_FLAG : 0);
if (!level)
mz_uint comp_flags = TDEFL_WRITE_ZLIB_HEADER | s_tdefl_num_probes[MZ_MIN(10, m_iCompressionLevel)] | ((m_iCompressionLevel <= 3) ? TDEFL_GREEDY_PARSING_FLAG : 0);
if (!m_iCompressionLevel)
{
comp_flags |= TDEFL_FORCE_ALL_RAW_BLOCKS;
}
tdefl_status status = tdefl_init(&g_deflator, NULL, NULL, comp_flags);
assert(status == TDEFL_STATUS_OKAY);
tdefl_status status = tdefl_init(pDeflator, NULL, NULL, comp_flags);
if (status != TDEFL_STATUS_OKAY)
{
stringstream ss;
@ -78,9 +90,8 @@ namespace PolyVox
size_t ulDstLength = uDstLength;
// Compress as much of the input as possible (or all of it) to the output buffer.
status = tdefl_compress(&g_deflator, pSrcData, &uSrcLength, pDstData, &ulDstLength, TDEFL_FINISH);
status = tdefl_compress(pDeflator, pSrcData, &uSrcLength, pDstData, &ulDstLength, TDEFL_FINISH);
assert(status == TDEFL_STATUS_DONE);
if (status != TDEFL_STATUS_DONE)
{
stringstream ss;
@ -91,6 +102,7 @@ namespace PolyVox
return ulDstLength;
}
// The commented out function is left here for reference and debugging purposes.
/*uint32_t MinizCompressor::decompress(void* pSrcData, uint32_t uSrcLength, void* pDstData, uint32_t uDstLength)
{
mz_ulong ulDstLength = uDstLength;
@ -106,6 +118,8 @@ namespace PolyVox
return ulDstLength;
}*/
// The behaviour of this function should be the same as the commented out version above (except that it requires the destination to be a power of two),
// but it's implemented using the lower level API which does not conflict with zlib or perform any memory allocations.
uint32_t MinizCompressor::decompress(void* pSrcData, uint32_t uSrcLength, void* pDstData, uint32_t uDstLength)
{
size_t ulDstLength = uDstLength;