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exposed ZSTD_MAGIC_DICTIONARY in zstd.h

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makes it easier to explain ZSTD_dictMode
This commit is contained in:
Yann Collet 2017-06-27 13:50:34 -07:00
parent fecc721fd9
commit 7d3816183f
6 changed files with 20 additions and 14 deletions
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9
doc/zstd_manual.html
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@ -348,7 +348,7 @@ static const ZSTD_customMem ZSTD_defaultCMem = { NULL, NULL, NULL };
<pre><b>size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize);
</b><p> `src` should point to the start of a ZSTD encoded frame or skippable frame
`srcSize` must be at least as large as the frame
@return : the compressed size of the frame pointed to by `src`,
@return : the compressed size of the frame pointed to by `src`,FUZ_rand(&lseed) & 1)
suitable to pass to `ZSTD_decompress` or similar,
or an error code if given invalid input.
</p></pre><BR>
@ -482,7 +482,10 @@ size_t ZSTD_estimateDDictSize(size_t dictSize, unsigned byReference);
It is important that dictBuffer outlives CDict, it must remain read accessible throughout the lifetime of CDict
</p></pre><BR>
<pre><b>typedef enum { ZSTD_dm_auto=0, ZSTD_dm_rawContent, ZSTD_dm_fullDict } ZSTD_dictMode_e;
<pre><b>typedef enum { ZSTD_dm_auto=0, </b>/* dictionary is "full" if it starts with ZSTD_MAGIC_DICTIONARY, rawContent otherwize */<b>
ZSTD_dm_rawContent, </b>/* ensures dictionary is always loaded as rawContent, even if it starts with ZSTD_MAGIC_DICTIONARY */<b>
ZSTD_dm_fullDict </b>/* refuses to load a dictionary if it does not respect Zstandard's specification */<b>
} ZSTD_dictMode_e;
</b></pre><BR>
<pre><b>ZSTD_CDict* ZSTD_createCDict_advanced(const void* dict, size_t dictSize,
unsigned byReference, ZSTD_dictMode_e dictMode,
@ -886,7 +889,7 @@ void ZSTD_copyDCtx(ZSTD_DCtx* dctx, const ZSTD_DCtx* preparedDCtx);
</p></pre><BR>
<pre><b>size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize); </b>/* Not ready yet ! <===================================== */<b>
</b><p> Reference a prefix (content-only dictionary) to bootstrap next compression job.
</b><p> Reference a prefix (raw-content dictionary) for next compression job.
Decompression will have to use same prefix.
Prefix is only used once. Tables are discarded at end of compression job.
If there is a need to use same prefix multiple times, consider embedding it into a ZSTD_CDict.

1
lib/common/zstd_internal.h
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@ -98,7 +98,6 @@
* Common constants
***************************************/
#define ZSTD_OPT_NUM (1<<12)
#define ZSTD_DICT_MAGIC 0xEC30A437 /* v0.7+ */
#define ZSTD_REP_NUM 3 /* number of repcodes */
#define ZSTD_REP_CHECK (ZSTD_REP_NUM) /* number of repcodes to check by the optimal parser */

2
lib/compress/zstd_compress.c
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@ -3181,7 +3181,7 @@ static size_t ZSTD_compress_insertDictionary(ZSTD_CCtx* cctx,
if (dictMode==ZSTD_dm_rawContent)
return ZSTD_loadDictionaryContent(cctx, dict, dictSize);
if (MEM_readLE32(dict) != ZSTD_DICT_MAGIC) {
if (MEM_readLE32(dict) != ZSTD_MAGIC_DICTIONARY) {
if (dictMode == ZSTD_dm_auto) {
DEBUGLOG(5, "raw content dictionary detected");
return ZSTD_loadDictionaryContent(cctx, dict, dictSize);

6
lib/decompress/zstd_decompress.c
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@ -1884,7 +1884,7 @@ static size_t ZSTD_decompress_insertDictionary(ZSTD_DCtx* dctx, const void* dict
{
if (dictSize < 8) return ZSTD_refDictContent(dctx, dict, dictSize);
{ U32 const magic = MEM_readLE32(dict);
if (magic != ZSTD_DICT_MAGIC) {
if (magic != ZSTD_MAGIC_DICTIONARY) {
return ZSTD_refDictContent(dctx, dict, dictSize); /* pure content mode */
} }
dctx->dictID = MEM_readLE32((const char*)dict + 4);
@ -1964,7 +1964,7 @@ static size_t ZSTD_loadEntropy_inDDict(ZSTD_DDict* ddict)
ddict->entropyPresent = 0;
if (ddict->dictSize < 8) return 0;
{ U32 const magic = MEM_readLE32(ddict->dictContent);
if (magic != ZSTD_DICT_MAGIC) return 0; /* pure content mode */
if (magic != ZSTD_MAGIC_DICTIONARY) return 0; /* pure content mode */
}
ddict->dictID = MEM_readLE32((const char*)ddict->dictContent + 4);
@ -2083,7 +2083,7 @@ size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict)
unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize)
{
if (dictSize < 8) return 0;
if (MEM_readLE32(dict) != ZSTD_DICT_MAGIC) return 0;
if (MEM_readLE32(dict) != ZSTD_MAGIC_DICTIONARY) return 0;
return MEM_readLE32((const char*)dict + 4);
}

6
lib/dictBuilder/zdict.c
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@ -94,7 +94,7 @@ const char* ZDICT_getErrorName(size_t errorCode) { return ERR_getErrorName(error
unsigned ZDICT_getDictID(const void* dictBuffer, size_t dictSize)
{
if (dictSize < 8) return 0;
if (MEM_readLE32(dictBuffer) != ZSTD_DICT_MAGIC) return 0;
if (MEM_readLE32(dictBuffer) != ZSTD_MAGIC_DICTIONARY) return 0;
return MEM_readLE32((const char*)dictBuffer + 4);
}
@ -865,7 +865,7 @@ size_t ZDICT_finalizeDictionary(void* dictBuffer, size_t dictBufferCapacity,
if (dictBufferCapacity < ZDICT_DICTSIZE_MIN) return ERROR(dstSize_tooSmall);
/* dictionary header */
MEM_writeLE32(header, ZSTD_DICT_MAGIC);
MEM_writeLE32(header, ZSTD_MAGIC_DICTIONARY);
{ U64 const randomID = XXH64(customDictContent, dictContentSize, 0);
U32 const compliantID = (randomID % ((1U<<31)-32768)) + 32768;
U32 const dictID = params.dictID ? params.dictID : compliantID;
@ -917,7 +917,7 @@ size_t ZDICT_addEntropyTablesFromBuffer_advanced(void* dictBuffer, size_t dictCo
}
/* add dictionary header (after entropy tables) */
MEM_writeLE32(dictBuffer, ZSTD_DICT_MAGIC);
MEM_writeLE32(dictBuffer, ZSTD_MAGIC_DICTIONARY);
{ U64 const randomID = XXH64((char*)dictBuffer + dictBufferCapacity - dictContentSize, dictContentSize, 0);
U32 const compliantID = (randomID % ((1U<<31)-32768)) + 32768;
U32 const dictID = params.dictID ? params.dictID : compliantID;

10
lib/zstd.h
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@ -360,6 +360,7 @@ ZSTDLIB_API size_t ZSTD_DStreamOutSize(void); /*!< recommended size for output
/* --- Constants ---*/
#define ZSTD_MAGICNUMBER 0xFD2FB528 /* >= v0.8.0 */
#define ZSTD_MAGIC_SKIPPABLE_START 0x184D2A50U
#define ZSTD_MAGIC_DICTIONARY 0xEC30A437 /* v0.7+ */
#define ZSTD_WINDOWLOG_MAX_32 27
#define ZSTD_WINDOWLOG_MAX_64 27
@ -379,7 +380,7 @@ ZSTDLIB_API size_t ZSTD_DStreamOutSize(void); /*!< recommended size for output
#define ZSTD_FRAMEHEADERSIZE_MAX 18 /* for static allocation */
#define ZSTD_FRAMEHEADERSIZE_MIN 6
static const size_t ZSTD_frameHeaderSize_prefix = 5;
static const size_t ZSTD_frameHeaderSize_prefix = 5; /* minimum input size to know frame header size */
static const size_t ZSTD_frameHeaderSize_min = ZSTD_FRAMEHEADERSIZE_MIN;
static const size_t ZSTD_frameHeaderSize_max = ZSTD_FRAMEHEADERSIZE_MAX;
static const size_t ZSTD_skippableHeaderSize = 8; /* magic number + skippable frame length */
@ -573,7 +574,10 @@ ZSTDLIB_API size_t ZSTD_setCCtxParameter(ZSTD_CCtx* cctx, ZSTD_CCtxParameter par
ZSTDLIB_API ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel);
typedef enum { ZSTD_dm_auto=0, ZSTD_dm_rawContent, ZSTD_dm_fullDict } ZSTD_dictMode_e;
typedef enum { ZSTD_dm_auto=0, /* dictionary is "full" if it starts with ZSTD_MAGIC_DICTIONARY, rawContent otherwize */
ZSTD_dm_rawContent, /* ensures dictionary is always loaded as rawContent, even if it starts with ZSTD_MAGIC_DICTIONARY */
ZSTD_dm_fullDict /* refuses to load a dictionary if it does not respect Zstandard's specification */
} ZSTD_dictMode_e;
/*! ZSTD_createCDict_advanced() :
* Create a ZSTD_CDict using external alloc and free, and customized compression parameters */
ZSTDLIB_API ZSTD_CDict* ZSTD_createCDict_advanced(const void* dict, size_t dictSize,
@ -1027,7 +1031,7 @@ ZSTDLIB_API size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, s
ZSTDLIB_API size_t ZSTD_CCtx_refCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict);
/*! ZSTD_CCtx_refPrefix() :
* Reference a prefix (content-only dictionary) to bootstrap next compression job.
* Reference a prefix (raw-content dictionary) for next compression job.
* Decompression will have to use same prefix.
* Prefix is only used once. Tables are discarded at end of compression job.
* If there is a need to use same prefix multiple times, consider embedding it into a ZSTD_CDict.