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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 18:24:20 +0000 |
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| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 18:24:20 +0000 |
| commit | 483eb2f56657e8e7f419ab1a4fab8dce9ade8609 (patch) | |
| tree | e5d88d25d870d5dedacb6bbdbe2a966086a0a5cf /src/zstd/doc/zstd_manual.html | |
| parent | Initial commit. (diff) | |
| download | ceph-483eb2f56657e8e7f419ab1a4fab8dce9ade8609.tar.xz ceph-483eb2f56657e8e7f419ab1a4fab8dce9ade8609.zip | |
Adding upstream version 14.2.21.upstream/14.2.21upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/zstd/doc/zstd_manual.html')
| -rw-r--r-- | src/zstd/doc/zstd_manual.html | 1200 |
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diff --git a/src/zstd/doc/zstd_manual.html b/src/zstd/doc/zstd_manual.html new file mode 100644 index 00000000..b4720ada --- /dev/null +++ b/src/zstd/doc/zstd_manual.html @@ -0,0 +1,1200 @@ +<html> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> +<title>zstd 1.3.2 Manual</title> +</head> +<body> +<h1>zstd 1.3.2 Manual</h1> +<hr> +<a name="Contents"></a><h2>Contents</h2> +<ol> +<li><a href="#Chapter1">Introduction</a></li> +<li><a href="#Chapter2">Version</a></li> +<li><a href="#Chapter3">Simple API</a></li> +<li><a href="#Chapter4">Explicit memory management</a></li> +<li><a href="#Chapter5">Simple dictionary API</a></li> +<li><a href="#Chapter6">Bulk processing dictionary API</a></li> +<li><a href="#Chapter7">Streaming</a></li> +<li><a href="#Chapter8">Streaming compression - HowTo</a></li> +<li><a href="#Chapter9">Streaming decompression - HowTo</a></li> +<li><a href="#Chapter10">START OF ADVANCED AND EXPERIMENTAL FUNCTIONS</a></li> +<li><a href="#Chapter11">Advanced types</a></li> +<li><a href="#Chapter12">Frame size functions</a></li> +<li><a href="#Chapter13">Context memory usage</a></li> +<li><a href="#Chapter14">Advanced compression functions</a></li> +<li><a href="#Chapter15">Advanced decompression functions</a></li> +<li><a href="#Chapter16">Advanced streaming functions</a></li> +<li><a href="#Chapter17">Buffer-less and synchronous inner streaming functions</a></li> +<li><a href="#Chapter18">Buffer-less streaming compression (synchronous mode)</a></li> +<li><a href="#Chapter19">Buffer-less streaming decompression (synchronous mode)</a></li> +<li><a href="#Chapter20">New advanced API (experimental)</a></li> +<li><a href="#Chapter21">Block level API</a></li> +</ol> +<hr> +<a name="Chapter1"></a><h2>Introduction</h2><pre> + zstd, short for Zstandard, is a fast lossless compression algorithm, + targeting real-time compression scenarios at zlib-level and better compression ratios. + The zstd compression library provides in-memory compression and decompression functions. + The library supports compression levels from 1 up to ZSTD_maxCLevel() which is currently 22. + Levels >= 20, labeled `--ultra`, should be used with caution, as they require more memory. + Compression can be done in: + - a single step (described as Simple API) + - a single step, reusing a context (described as Explicit memory management) + - unbounded multiple steps (described as Streaming compression) + The compression ratio achievable on small data can be highly improved using a dictionary in: + - a single step (described as Simple dictionary API) + - a single step, reusing a dictionary (described as Fast dictionary API) + + Advanced experimental functions can be accessed using #define ZSTD_STATIC_LINKING_ONLY before including zstd.h. + Advanced experimental APIs shall never be used with a dynamic library. + They are not "stable", their definition may change in the future. Only static linking is allowed. +<BR></pre> + +<a name="Chapter2"></a><h2>Version</h2><pre></pre> + +<pre><b>unsigned ZSTD_versionNumber(void); </b>/**< useful to check dll version */<b> +</b></pre><BR> +<a name="Chapter3"></a><h2>Simple API</h2><pre></pre> + +<pre><b>size_t ZSTD_compress( void* dst, size_t dstCapacity, + const void* src, size_t srcSize, + int compressionLevel); +</b><p> Compresses `src` content as a single zstd compressed frame into already allocated `dst`. + Hint : compression runs faster if `dstCapacity` >= `ZSTD_compressBound(srcSize)`. + @return : compressed size written into `dst` (<= `dstCapacity), + or an error code if it fails (which can be tested using ZSTD_isError()). +</p></pre><BR> + +<pre><b>size_t ZSTD_decompress( void* dst, size_t dstCapacity, + const void* src, size_t compressedSize); +</b><p> `compressedSize` : must be the _exact_ size of some number of compressed and/or skippable frames. + `dstCapacity` is an upper bound of originalSize to regenerate. + If user cannot imply a maximum upper bound, it's better to use streaming mode to decompress data. + @return : the number of bytes decompressed into `dst` (<= `dstCapacity`), + or an errorCode if it fails (which can be tested using ZSTD_isError()). +</p></pre><BR> + +<pre><b>#define ZSTD_CONTENTSIZE_UNKNOWN (0ULL - 1) +#define ZSTD_CONTENTSIZE_ERROR (0ULL - 2) +unsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize); +</b><p> `src` should point to the start of a ZSTD encoded frame. + `srcSize` must be at least as large as the frame header. + hint : any size >= `ZSTD_frameHeaderSize_max` is large enough. + @return : - decompressed size of the frame in `src`, if known + - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined + - ZSTD_CONTENTSIZE_ERROR if an error occurred (e.g. invalid magic number, srcSize too small) + note 1 : a 0 return value means the frame is valid but "empty". + note 2 : decompressed size is an optional field, it may not be present, typically in streaming mode. + When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size. + In which case, it's necessary to use streaming mode to decompress data. + Optionally, application can rely on some implicit limit, + as ZSTD_decompress() only needs an upper bound of decompressed size. + (For example, data could be necessarily cut into blocks <= 16 KB). + note 3 : decompressed size is always present when compression is done with ZSTD_compress() + note 4 : decompressed size can be very large (64-bits value), + potentially larger than what local system can handle as a single memory segment. + In which case, it's necessary to use streaming mode to decompress data. + note 5 : If source is untrusted, decompressed size could be wrong or intentionally modified. + Always ensure return value fits within application's authorized limits. + Each application can set its own limits. + note 6 : This function replaces ZSTD_getDecompressedSize() +</p></pre><BR> + +<pre><b>unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize); +</b><p> NOTE: This function is now obsolete, in favor of ZSTD_getFrameContentSize(). + Both functions work the same way, + but ZSTD_getDecompressedSize() blends + "empty", "unknown" and "error" results in the same return value (0), + while ZSTD_getFrameContentSize() distinguishes them. + + 'src' is the start of a zstd compressed frame. + @return : content size to be decompressed, as a 64-bits value _if known and not empty_, 0 otherwise. +</p></pre><BR> + +<h3>Helper functions</h3><pre></pre><b><pre>#define ZSTD_COMPRESSBOUND(srcSize) ((srcSize) + ((srcSize)>>8) + (((srcSize) < 128 KB) ? ((128 KB - (srcSize)) >> 11) </b>/* margin, from 64 to 0 */ : 0)) /* this formula ensures that bound(A) + bound(B) <= bound(A+B) as long as A and B >= 128 KB */<b> +size_t ZSTD_compressBound(size_t srcSize); </b>/*!< maximum compressed size in worst case scenario */<b> +unsigned ZSTD_isError(size_t code); </b>/*!< tells if a `size_t` function result is an error code */<b> +const char* ZSTD_getErrorName(size_t code); </b>/*!< provides readable string from an error code */<b> +int ZSTD_maxCLevel(void); </b>/*!< maximum compression level available */<b> +</pre></b><BR> +<a name="Chapter4"></a><h2>Explicit memory management</h2><pre></pre> + +<h3>Compression context</h3><pre> When compressing many times, + it is recommended to allocate a context just once, and re-use it for each successive compression operation. + This will make workload friendlier for system's memory. + Use one context per thread for parallel execution in multi-threaded environments. +</pre><b><pre>typedef struct ZSTD_CCtx_s ZSTD_CCtx; +ZSTD_CCtx* ZSTD_createCCtx(void); +size_t ZSTD_freeCCtx(ZSTD_CCtx* cctx); +</pre></b><BR> +<pre><b>size_t ZSTD_compressCCtx(ZSTD_CCtx* ctx, + void* dst, size_t dstCapacity, + const void* src, size_t srcSize, + int compressionLevel); +</b><p> Same as ZSTD_compress(), requires an allocated ZSTD_CCtx (see ZSTD_createCCtx()). +</p></pre><BR> + +<h3>Decompression context</h3><pre> When decompressing many times, + it is recommended to allocate a context only once, + and re-use it for each successive compression operation. + This will make workload friendlier for system's memory. + Use one context per thread for parallel execution. +</pre><b><pre>typedef struct ZSTD_DCtx_s ZSTD_DCtx; +ZSTD_DCtx* ZSTD_createDCtx(void); +size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx); +</pre></b><BR> +<pre><b>size_t ZSTD_decompressDCtx(ZSTD_DCtx* ctx, + void* dst, size_t dstCapacity, + const void* src, size_t srcSize); +</b><p> Same as ZSTD_decompress(), requires an allocated ZSTD_DCtx (see ZSTD_createDCtx()) +</p></pre><BR> + +<a name="Chapter5"></a><h2>Simple dictionary API</h2><pre></pre> + +<pre><b>size_t ZSTD_compress_usingDict(ZSTD_CCtx* ctx, + void* dst, size_t dstCapacity, + const void* src, size_t srcSize, + const void* dict,size_t dictSize, + int compressionLevel); +</b><p> Compression using a predefined Dictionary (see dictBuilder/zdict.h). + Note : This function loads the dictionary, resulting in significant startup delay. + Note : When `dict == NULL || dictSize < 8` no dictionary is used. +</p></pre><BR> + +<pre><b>size_t ZSTD_decompress_usingDict(ZSTD_DCtx* dctx, + void* dst, size_t dstCapacity, + const void* src, size_t srcSize, + const void* dict,size_t dictSize); +</b><p> Decompression using a predefined Dictionary (see dictBuilder/zdict.h). + Dictionary must be identical to the one used during compression. + Note : This function loads the dictionary, resulting in significant startup delay. + Note : When `dict == NULL || dictSize < 8` no dictionary is used. +</p></pre><BR> + +<a name="Chapter6"></a><h2>Bulk processing dictionary API</h2><pre></pre> + +<pre><b>ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize, + int compressionLevel); +</b><p> When compressing multiple messages / blocks with the same dictionary, it's recommended to load it just once. + ZSTD_createCDict() will create a digested dictionary, ready to start future compression operations without startup delay. + ZSTD_CDict can be created once and shared by multiple threads concurrently, since its usage is read-only. + `dictBuffer` can be released after ZSTD_CDict creation, since its content is copied within CDict +</p></pre><BR> + +<pre><b>size_t ZSTD_freeCDict(ZSTD_CDict* CDict); +</b><p> Function frees memory allocated by ZSTD_createCDict(). +</p></pre><BR> + +<pre><b>size_t ZSTD_compress_usingCDict(ZSTD_CCtx* cctx, + void* dst, size_t dstCapacity, + const void* src, size_t srcSize, + const ZSTD_CDict* cdict); +</b><p> Compression using a digested Dictionary. + Faster startup than ZSTD_compress_usingDict(), recommended when same dictionary is used multiple times. + Note that compression level is decided during dictionary creation. + Frame parameters are hardcoded (dictID=yes, contentSize=yes, checksum=no) +</p></pre><BR> + +<pre><b>ZSTD_DDict* ZSTD_createDDict(const void* dictBuffer, size_t dictSize); +</b><p> Create a digested dictionary, ready to start decompression operation without startup delay. + dictBuffer can be released after DDict creation, as its content is copied inside DDict +</p></pre><BR> + +<pre><b>size_t ZSTD_freeDDict(ZSTD_DDict* ddict); +</b><p> Function frees memory allocated with ZSTD_createDDict() +</p></pre><BR> + +<pre><b>size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx, + void* dst, size_t dstCapacity, + const void* src, size_t srcSize, + const ZSTD_DDict* ddict); +</b><p> Decompression using a digested Dictionary. + Faster startup than ZSTD_decompress_usingDict(), recommended when same dictionary is used multiple times. +</p></pre><BR> + +<a name="Chapter7"></a><h2>Streaming</h2><pre></pre> + +<pre><b>typedef struct ZSTD_inBuffer_s { + const void* src; </b>/**< start of input buffer */<b> + size_t size; </b>/**< size of input buffer */<b> + size_t pos; </b>/**< position where reading stopped. Will be updated. Necessarily 0 <= pos <= size */<b> +} ZSTD_inBuffer; +</b></pre><BR> +<pre><b>typedef struct ZSTD_outBuffer_s { + void* dst; </b>/**< start of output buffer */<b> + size_t size; </b>/**< size of output buffer */<b> + size_t pos; </b>/**< position where writing stopped. Will be updated. Necessarily 0 <= pos <= size */<b> +} ZSTD_outBuffer; +</b></pre><BR> +<a name="Chapter8"></a><h2>Streaming compression - HowTo</h2><pre> + A ZSTD_CStream object is required to track streaming operation. + Use ZSTD_createCStream() and ZSTD_freeCStream() to create/release resources. + ZSTD_CStream objects can be reused multiple times on consecutive compression operations. + It is recommended to re-use ZSTD_CStream in situations where many streaming operations will be achieved consecutively, + since it will play nicer with system's memory, by re-using already allocated memory. + Use one separate ZSTD_CStream per thread for parallel execution. + + Start a new compression by initializing ZSTD_CStream. + Use ZSTD_initCStream() to start a new compression operation. + Use ZSTD_initCStream_usingDict() or ZSTD_initCStream_usingCDict() for a compression which requires a dictionary (experimental section) + + Use ZSTD_compressStream() repetitively to consume input stream. + The function will automatically update both `pos` fields. + Note that it may not consume the entire input, in which case `pos < size`, + and it's up to the caller to present again remaining data. + @return : a size hint, preferred nb of bytes to use as input for next function call + or an error code, which can be tested using ZSTD_isError(). + Note 1 : it's just a hint, to help latency a little, any other value will work fine. + Note 2 : size hint is guaranteed to be <= ZSTD_CStreamInSize() + + At any moment, it's possible to flush whatever data remains within internal buffer, using ZSTD_flushStream(). + `output->pos` will be updated. + Note that some content might still be left within internal buffer if `output->size` is too small. + @return : nb of bytes still present within internal buffer (0 if it's empty) + or an error code, which can be tested using ZSTD_isError(). + + ZSTD_endStream() instructs to finish a frame. + It will perform a flush and write frame epilogue. + The epilogue is required for decoders to consider a frame completed. + ZSTD_endStream() may not be able to flush full data if `output->size` is too small. + In which case, call again ZSTD_endStream() to complete the flush. + @return : 0 if frame fully completed and fully flushed, + or >0 if some data is still present within internal buffer + (value is minimum size estimation for remaining data to flush, but it could be more) + or an error code, which can be tested using ZSTD_isError(). + + +<BR></pre> + +<pre><b>typedef ZSTD_CCtx ZSTD_CStream; </b>/**< CCtx and CStream are now effectively same object (>= v1.3.0) */<b> +</b></pre><BR> +<h3>ZSTD_CStream management functions</h3><pre></pre><b><pre>ZSTD_CStream* ZSTD_createCStream(void); +size_t ZSTD_freeCStream(ZSTD_CStream* zcs); +</pre></b><BR> +<h3>Streaming compression functions</h3><pre></pre><b><pre>size_t ZSTD_initCStream(ZSTD_CStream* zcs, int compressionLevel); +size_t ZSTD_compressStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input); +size_t ZSTD_flushStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output); +size_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output); +</pre></b><BR> +<pre><b>size_t ZSTD_CStreamInSize(void); </b>/**< recommended size for input buffer */<b> +</b></pre><BR> +<pre><b>size_t ZSTD_CStreamOutSize(void); </b>/**< recommended size for output buffer. Guarantee to successfully flush at least one complete compressed block in all circumstances. */<b> +</b></pre><BR> +<a name="Chapter9"></a><h2>Streaming decompression - HowTo</h2><pre> + A ZSTD_DStream object is required to track streaming operations. + Use ZSTD_createDStream() and ZSTD_freeDStream() to create/release resources. + ZSTD_DStream objects can be re-used multiple times. + + Use ZSTD_initDStream() to start a new decompression operation, + or ZSTD_initDStream_usingDict() if decompression requires a dictionary. + @return : recommended first input size + + Use ZSTD_decompressStream() repetitively to consume your input. + The function will update both `pos` fields. + If `input.pos < input.size`, some input has not been consumed. + It's up to the caller to present again remaining data. + If `output.pos < output.size`, decoder has flushed everything it could. + @return : 0 when a frame is completely decoded and fully flushed, + an error code, which can be tested using ZSTD_isError(), + any other value > 0, which means there is still some decoding to do to complete current frame. + The return value is a suggested next input size (a hint to improve latency) that will never load more than the current frame. + +<BR></pre> + +<pre><b>typedef ZSTD_DCtx ZSTD_DStream; </b>/**< DCtx and DStream are now effectively same object (>= v1.3.0) */<b> +</b></pre><BR> +<h3>ZSTD_DStream management functions</h3><pre></pre><b><pre>ZSTD_DStream* ZSTD_createDStream(void); +size_t ZSTD_freeDStream(ZSTD_DStream* zds); +</pre></b><BR> +<h3>Streaming decompression functions</h3><pre></pre><b><pre>size_t ZSTD_initDStream(ZSTD_DStream* zds); +size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input); +</pre></b><BR> +<pre><b>size_t ZSTD_DStreamInSize(void); </b>/*!< recommended size for input buffer */<b> +</b></pre><BR> +<pre><b>size_t ZSTD_DStreamOutSize(void); </b>/*!< recommended size for output buffer. Guarantee to successfully flush at least one complete block in all circumstances. */<b> +</b></pre><BR> +<a name="Chapter10"></a><h2>START OF ADVANCED AND EXPERIMENTAL FUNCTIONS</h2><pre> The definitions in this section are considered experimental. + They should never be used with a dynamic library, as prototypes may change in the future. + They are provided for advanced scenarios. + Use them only in association with static linking. + +<BR></pre> + +<a name="Chapter11"></a><h2>Advanced types</h2><pre></pre> + +<pre><b>typedef enum { ZSTD_fast=1, ZSTD_dfast, ZSTD_greedy, ZSTD_lazy, ZSTD_lazy2, + ZSTD_btlazy2, ZSTD_btopt, ZSTD_btultra } ZSTD_strategy; </b>/* from faster to stronger */<b> +</b></pre><BR> +<pre><b>typedef struct { + unsigned windowLog; </b>/**< largest match distance : larger == more compression, more memory needed during decompression */<b> + unsigned chainLog; </b>/**< fully searched segment : larger == more compression, slower, more memory (useless for fast) */<b> + unsigned hashLog; </b>/**< dispatch table : larger == faster, more memory */<b> + unsigned searchLog; </b>/**< nb of searches : larger == more compression, slower */<b> + unsigned searchLength; </b>/**< match length searched : larger == faster decompression, sometimes less compression */<b> + unsigned targetLength; </b>/**< acceptable match size for optimal parser (only) : larger == more compression, slower */<b> + ZSTD_strategy strategy; +} ZSTD_compressionParameters; +</b></pre><BR> +<pre><b>typedef struct { + unsigned contentSizeFlag; </b>/**< 1: content size will be in frame header (when known) */<b> + unsigned checksumFlag; </b>/**< 1: generate a 32-bits checksum at end of frame, for error detection */<b> + unsigned noDictIDFlag; </b>/**< 1: no dictID will be saved into frame header (if dictionary compression) */<b> +} ZSTD_frameParameters; +</b></pre><BR> +<pre><b>typedef struct { + ZSTD_compressionParameters cParams; + ZSTD_frameParameters fParams; +} ZSTD_parameters; +</b></pre><BR> +<h3>Custom memory allocation functions</h3><pre></pre><b><pre>typedef void* (*ZSTD_allocFunction) (void* opaque, size_t size); +typedef void (*ZSTD_freeFunction) (void* opaque, void* address); +typedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; void* opaque; } ZSTD_customMem; +</b>/* use this constant to defer to stdlib's functions */<b> +static const ZSTD_customMem ZSTD_defaultCMem = { NULL, NULL, NULL }; +</pre></b><BR> +<a name="Chapter12"></a><h2>Frame size functions</h2><pre></pre> + +<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 first frame starting at `src`, + suitable to pass to `ZSTD_decompress` or similar, + or an error code if input is invalid +</p></pre><BR> + +<pre><b>unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize); +</b><p> `src` should point the start of a series of ZSTD encoded and/or skippable frames + `srcSize` must be the _exact_ size of this series + (i.e. there should be a frame boundary exactly at `srcSize` bytes after `src`) + @return : - decompressed size of all data in all successive frames + - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN + - if an error occurred: ZSTD_CONTENTSIZE_ERROR + + note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode. + When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size. + In which case, it's necessary to use streaming mode to decompress data. + note 2 : decompressed size is always present when compression is done with ZSTD_compress() + note 3 : decompressed size can be very large (64-bits value), + potentially larger than what local system can handle as a single memory segment. + In which case, it's necessary to use streaming mode to decompress data. + note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified. + Always ensure result fits within application's authorized limits. + Each application can set its own limits. + note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to + read each contained frame header. This is fast as most of the data is skipped, + however it does mean that all frame data must be present and valid. +</p></pre><BR> + +<pre><b>size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize); +</b><p> `src` should point to the start of a ZSTD frame + `srcSize` must be >= ZSTD_frameHeaderSize_prefix. + @return : size of the Frame Header +</p></pre><BR> + +<a name="Chapter13"></a><h2>Context memory usage</h2><pre></pre> + +<pre><b>size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx); +size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx); +size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs); +size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds); +size_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict); +size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict); +</b><p> These functions give the current memory usage of selected object. + Object memory usage can evolve when re-used multiple times. +</p></pre><BR> + +<pre><b>size_t ZSTD_estimateCCtxSize(int compressionLevel); +size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams); +size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params); +size_t ZSTD_estimateDCtxSize(void); +</b><p> These functions make it possible to estimate memory usage + of a future {D,C}Ctx, before its creation. + ZSTD_estimateCCtxSize() will provide a budget large enough for any compression level up to selected one. + It will also consider src size to be arbitrarily "large", which is worst case. + If srcSize is known to always be small, ZSTD_estimateCCtxSize_usingCParams() can provide a tighter estimation. + ZSTD_estimateCCtxSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel. + ZSTD_estimateCCtxSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParam_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_p_nbThreads is > 1. + Note : CCtx estimation is only correct for single-threaded compression +</p></pre><BR> + +<pre><b>size_t ZSTD_estimateCStreamSize(int compressionLevel); +size_t ZSTD_estimateCStreamSize_usingCParams(ZSTD_compressionParameters cParams); +size_t ZSTD_estimateCStreamSize_usingCCtxParams(const ZSTD_CCtx_params* params); +size_t ZSTD_estimateDStreamSize(size_t windowSize); +size_t ZSTD_estimateDStreamSize_fromFrame(const void* src, size_t srcSize); +</b><p> ZSTD_estimateCStreamSize() will provide a budget large enough for any compression level up to selected one. + It will also consider src size to be arbitrarily "large", which is worst case. + If srcSize is known to always be small, ZSTD_estimateCStreamSize_usingCParams() can provide a tighter estimation. + ZSTD_estimateCStreamSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel. + ZSTD_estimateCStreamSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParam_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_p_nbThreads is set to a value > 1. + Note : CStream estimation is only correct for single-threaded compression. + ZSTD_DStream memory budget depends on window Size. + This information can be passed manually, using ZSTD_estimateDStreamSize, + or deducted from a valid frame Header, using ZSTD_estimateDStreamSize_fromFrame(); + Note : if streaming is init with function ZSTD_init?Stream_usingDict(), + an internal ?Dict will be created, which additional size is not estimated here. + In this case, get total size by adding ZSTD_estimate?DictSize +</p></pre><BR> + +<pre><b>typedef enum { + ZSTD_dlm_byCopy = 0, </b>/**< Copy dictionary content internally */<b> + ZSTD_dlm_byRef, </b>/**< Reference dictionary content -- the dictionary buffer must outlive its users. */<b> +} ZSTD_dictLoadMethod_e; +</b></pre><BR> +<pre><b>size_t ZSTD_estimateCDictSize(size_t dictSize, int compressionLevel); +size_t ZSTD_estimateCDictSize_advanced(size_t dictSize, ZSTD_compressionParameters cParams, ZSTD_dictLoadMethod_e dictLoadMethod); +size_t ZSTD_estimateDDictSize(size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod); +</b><p> ZSTD_estimateCDictSize() will bet that src size is relatively "small", and content is copied, like ZSTD_createCDict(). + ZSTD_estimateCStreamSize_advanced_usingCParams() makes it possible to control precisely compression parameters, like ZSTD_createCDict_advanced(). + Note : dictionary created by reference using ZSTD_dlm_byRef are smaller + +</p></pre><BR> + +<a name="Chapter14"></a><h2>Advanced compression functions</h2><pre></pre> + +<pre><b>ZSTD_CCtx* ZSTD_createCCtx_advanced(ZSTD_customMem customMem); +</b><p> Create a ZSTD compression context using external alloc and free functions +</p></pre><BR> + +<pre><b>ZSTD_CCtx* ZSTD_initStaticCCtx(void* workspace, size_t workspaceSize); +</b><p> workspace: The memory area to emplace the context into. + Provided pointer must 8-bytes aligned. + It must outlive context usage. + workspaceSize: Use ZSTD_estimateCCtxSize() or ZSTD_estimateCStreamSize() + to determine how large workspace must be to support scenario. + @return : pointer to ZSTD_CCtx*, or NULL if error (size too small) + Note : zstd will never resize nor malloc() when using a static cctx. + If it needs more memory than available, it will simply error out. + Note 2 : there is no corresponding "free" function. + Since workspace was allocated externally, it must be freed externally too. + Limitation 1 : currently not compatible with internal CDict creation, such as + ZSTD_CCtx_loadDictionary() or ZSTD_initCStream_usingDict(). + Limitation 2 : currently not compatible with multi-threading + +</p></pre><BR> + +<pre><b>ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel); +</b><p> Create a digested dictionary for compression + Dictionary content is simply referenced, and therefore stays in dictBuffer. + 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, </b>/* dictionary is "full" if it starts with ZSTD_MAGIC_DICTIONARY, otherwise it is "rawContent" */<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, + ZSTD_dictLoadMethod_e dictLoadMethod, + ZSTD_dictMode_e dictMode, + ZSTD_compressionParameters cParams, + ZSTD_customMem customMem); +</b><p> Create a ZSTD_CDict using external alloc and free, and customized compression parameters +</p></pre><BR> + +<pre><b>ZSTD_CDict* ZSTD_initStaticCDict( + void* workspace, size_t workspaceSize, + const void* dict, size_t dictSize, + ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictMode_e dictMode, + ZSTD_compressionParameters cParams); +</b><p> Generate a digested dictionary in provided memory area. + workspace: The memory area to emplace the dictionary into. + Provided pointer must 8-bytes aligned. + It must outlive dictionary usage. + workspaceSize: Use ZSTD_estimateCDictSize() + to determine how large workspace must be. + cParams : use ZSTD_getCParams() to transform a compression level + into its relevants cParams. + @return : pointer to ZSTD_CDict*, or NULL if error (size too small) + Note : there is no corresponding "free" function. + Since workspace was allocated externally, it must be freed externally. + +</p></pre><BR> + +<pre><b>ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize); +</b><p> @return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize. + `estimatedSrcSize` value is optional, select 0 if not known +</p></pre><BR> + +<pre><b>ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize); +</b><p> same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of sub-component `ZSTD_compressionParameters`. + All fields of `ZSTD_frameParameters` are set to default (0) +</p></pre><BR> + +<pre><b>size_t ZSTD_checkCParams(ZSTD_compressionParameters params); +</b><p> Ensure param values remain within authorized range +</p></pre><BR> + +<pre><b>ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize); +</b><p> optimize params for a given `srcSize` and `dictSize`. + both values are optional, select `0` if unknown. +</p></pre><BR> + +<pre><b>size_t ZSTD_compress_advanced (ZSTD_CCtx* cctx, + void* dst, size_t dstCapacity, + const void* src, size_t srcSize, + const void* dict,size_t dictSize, + ZSTD_parameters params); +</b><p> Same as ZSTD_compress_usingDict(), with fine-tune control over each compression parameter +</p></pre><BR> + +<pre><b>size_t ZSTD_compress_usingCDict_advanced(ZSTD_CCtx* cctx, + void* dst, size_t dstCapacity, + const void* src, size_t srcSize, + const ZSTD_CDict* cdict, ZSTD_frameParameters fParams); +</b><p> Same as ZSTD_compress_usingCDict(), with fine-tune control over frame parameters +</p></pre><BR> + +<a name="Chapter15"></a><h2>Advanced decompression functions</h2><pre></pre> + +<pre><b>unsigned ZSTD_isFrame(const void* buffer, size_t size); +</b><p> Tells if the content of `buffer` starts with a valid Frame Identifier. + Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0. + Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled. + Note 3 : Skippable Frame Identifiers are considered valid. +</p></pre><BR> + +<pre><b>ZSTD_DCtx* ZSTD_createDCtx_advanced(ZSTD_customMem customMem); +</b><p> Create a ZSTD decompression context using external alloc and free functions +</p></pre><BR> + +<pre><b>ZSTD_DCtx* ZSTD_initStaticDCtx(void* workspace, size_t workspaceSize); +</b><p> workspace: The memory area to emplace the context into. + Provided pointer must 8-bytes aligned. + It must outlive context usage. + workspaceSize: Use ZSTD_estimateDCtxSize() or ZSTD_estimateDStreamSize() + to determine how large workspace must be to support scenario. + @return : pointer to ZSTD_DCtx*, or NULL if error (size too small) + Note : zstd will never resize nor malloc() when using a static dctx. + If it needs more memory than available, it will simply error out. + Note 2 : static dctx is incompatible with legacy support + Note 3 : there is no corresponding "free" function. + Since workspace was allocated externally, it must be freed externally. + Limitation : currently not compatible with internal DDict creation, + such as ZSTD_initDStream_usingDict(). + +</p></pre><BR> + +<pre><b>ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize); +</b><p> Create a digested dictionary, ready to start decompression operation without startup delay. + Dictionary content is referenced, and therefore stays in dictBuffer. + It is important that dictBuffer outlives DDict, + it must remain read accessible throughout the lifetime of DDict +</p></pre><BR> + +<pre><b>ZSTD_DDict* ZSTD_createDDict_advanced(const void* dict, size_t dictSize, + ZSTD_dictLoadMethod_e dictLoadMethod, + ZSTD_customMem customMem); +</b><p> Create a ZSTD_DDict using external alloc and free, optionally by reference +</p></pre><BR> + +<pre><b>ZSTD_DDict* ZSTD_initStaticDDict(void* workspace, size_t workspaceSize, + const void* dict, size_t dictSize, + ZSTD_dictLoadMethod_e dictLoadMethod); +</b><p> Generate a digested dictionary in provided memory area. + workspace: The memory area to emplace the dictionary into. + Provided pointer must 8-bytes aligned. + It must outlive dictionary usage. + workspaceSize: Use ZSTD_estimateDDictSize() + to determine how large workspace must be. + @return : pointer to ZSTD_DDict*, or NULL if error (size too small) + Note : there is no corresponding "free" function. + Since workspace was allocated externally, it must be freed externally. + +</p></pre><BR> + +<pre><b>unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize); +</b><p> Provides the dictID stored within dictionary. + if @return == 0, the dictionary is not conformant with Zstandard specification. + It can still be loaded, but as a content-only dictionary. +</p></pre><BR> + +<pre><b>unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict); +</b><p> Provides the dictID of the dictionary loaded into `ddict`. + If @return == 0, the dictionary is not conformant to Zstandard specification, or empty. + Non-conformant dictionaries can still be loaded, but as content-only dictionaries. +</p></pre><BR> + +<pre><b>unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize); +</b><p> Provides the dictID required to decompressed the frame stored within `src`. + If @return == 0, the dictID could not be decoded. + This could for one of the following reasons : + - The frame does not require a dictionary to be decoded (most common case). + - The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden information. + Note : this use case also happens when using a non-conformant dictionary. + - `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`). + - This is not a Zstandard frame. + When identifying the exact failure cause, it's possible to use ZSTD_getFrameHeader(), which will provide a more precise error code. +</p></pre><BR> + +<a name="Chapter16"></a><h2>Advanced streaming functions</h2><pre></pre> + +<h3>Advanced Streaming compression functions</h3><pre></pre><b><pre>ZSTD_CStream* ZSTD_createCStream_advanced(ZSTD_customMem customMem); +ZSTD_CStream* ZSTD_initStaticCStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticCCtx() */<b> +size_t ZSTD_initCStream_srcSize(ZSTD_CStream* zcs, int compressionLevel, unsigned long long pledgedSrcSize); </b>/**< pledgedSrcSize must be correct, a size of 0 means unknown. for a frame size of 0 use initCStream_advanced */<b> +size_t ZSTD_initCStream_usingDict(ZSTD_CStream* zcs, const void* dict, size_t dictSize, int compressionLevel); </b>/**< creates of an internal CDict (incompatible with static CCtx), except if dict == NULL or dictSize < 8, in which case no dict is used. Note: dict is loaded with ZSTD_dm_auto (treated as a full zstd dictionary if it begins with ZSTD_MAGIC_DICTIONARY, else as raw content) and ZSTD_dlm_byCopy.*/<b> +size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs, const void* dict, size_t dictSize, + ZSTD_parameters params, unsigned long long pledgedSrcSize); </b>/**< pledgedSrcSize is optional and can be 0 (meaning unknown). note: if the contentSizeFlag is set, pledgedSrcSize == 0 means the source size is actually 0. dict is loaded with ZSTD_dm_auto and ZSTD_dlm_byCopy. */<b> +size_t ZSTD_initCStream_usingCDict(ZSTD_CStream* zcs, const ZSTD_CDict* cdict); </b>/**< note : cdict will just be referenced, and must outlive compression session */<b> +size_t ZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs, const ZSTD_CDict* cdict, ZSTD_frameParameters fParams, unsigned long long pledgedSrcSize); </b>/**< same as ZSTD_initCStream_usingCDict(), with control over frame parameters */<b> +</pre></b><BR> +<pre><b>size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize); +</b><p> start a new compression job, using same parameters from previous job. + This is typically useful to skip dictionary loading stage, since it will re-use it in-place.. + Note that zcs must be init at least once before using ZSTD_resetCStream(). + pledgedSrcSize==0 means "srcSize unknown". + If pledgedSrcSize > 0, its value must be correct, as it will be written in header, and controlled at the end. + @return : 0, or an error code (which can be tested using ZSTD_isError()) +</p></pre><BR> + +<h3>Advanced Streaming decompression functions</h3><pre></pre><b><pre>ZSTD_DStream* ZSTD_createDStream_advanced(ZSTD_customMem customMem); +ZSTD_DStream* ZSTD_initStaticDStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticDCtx() */<b> +typedef enum { DStream_p_maxWindowSize } ZSTD_DStreamParameter_e; +size_t ZSTD_setDStreamParameter(ZSTD_DStream* zds, ZSTD_DStreamParameter_e paramType, unsigned paramValue); </b>/* obsolete : this API will be removed in a future version */<b> +size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize); </b>/**< note: no dictionary will be used if dict == NULL or dictSize < 8 */<b> +size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict); </b>/**< note : ddict is referenced, it must outlive decompression session */<b> +size_t ZSTD_resetDStream(ZSTD_DStream* zds); </b>/**< re-use decompression parameters from previous init; saves dictionary loading */<b> +</pre></b><BR> +<a name="Chapter17"></a><h2>Buffer-less and synchronous inner streaming functions</h2><pre> + This is an advanced API, giving full control over buffer management, for users which need direct control over memory. + But it's also a complex one, with several restrictions, documented below. + Prefer normal streaming API for an easier experience. + +<BR></pre> + +<a name="Chapter18"></a><h2>Buffer-less streaming compression (synchronous mode)</h2><pre> + A ZSTD_CCtx object is required to track streaming operations. + Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource. + ZSTD_CCtx object can be re-used multiple times within successive compression operations. + + Start by initializing a context. + Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary compression, + or ZSTD_compressBegin_advanced(), for finer parameter control. + It's also possible to duplicate a reference context which has already been initialized, using ZSTD_copyCCtx() + + Then, consume your input using ZSTD_compressContinue(). + There are some important considerations to keep in mind when using this advanced function : + - ZSTD_compressContinue() has no internal buffer. It uses externally provided buffers only. + - Interface is synchronous : input is consumed entirely and produces 1+ compressed blocks. + - Caller must ensure there is enough space in `dst` to store compressed data under worst case scenario. + Worst case evaluation is provided by ZSTD_compressBound(). + ZSTD_compressContinue() doesn't guarantee recover after a failed compression. + - ZSTD_compressContinue() presumes prior input ***is still accessible and unmodified*** (up to maximum distance size, see WindowLog). + It remembers all previous contiguous blocks, plus one separated memory segment (which can itself consists of multiple contiguous blocks) + - ZSTD_compressContinue() detects that prior input has been overwritten when `src` buffer overlaps. + In which case, it will "discard" the relevant memory section from its history. + + Finish a frame with ZSTD_compressEnd(), which will write the last block(s) and optional checksum. + It's possible to use srcSize==0, in which case, it will write a final empty block to end the frame. + Without last block mark, frames are considered unfinished (hence corrupted) by compliant decoders. + + `ZSTD_CCtx` object can be re-used (ZSTD_compressBegin()) to compress again. +<BR></pre> + +<h3>Buffer-less streaming compression functions</h3><pre></pre><b><pre>size_t ZSTD_compressBegin(ZSTD_CCtx* cctx, int compressionLevel); +size_t ZSTD_compressBegin_usingDict(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, int compressionLevel); +size_t ZSTD_compressBegin_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_parameters params, unsigned long long pledgedSrcSize); </b>/**< pledgedSrcSize is optional and can be 0 (meaning unknown). note: if the contentSizeFlag is set, pledgedSrcSize == 0 means the source size is actually 0 */<b> +size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); </b>/**< note: fails if cdict==NULL */<b> +size_t ZSTD_compressBegin_usingCDict_advanced(ZSTD_CCtx* const cctx, const ZSTD_CDict* const cdict, ZSTD_frameParameters const fParams, unsigned long long const pledgedSrcSize); </b>/* compression parameters are already set within cdict. pledgedSrcSize=0 means null-size */<b> +size_t ZSTD_copyCCtx(ZSTD_CCtx* cctx, const ZSTD_CCtx* preparedCCtx, unsigned long long pledgedSrcSize); </b>/**< note: if pledgedSrcSize can be 0, indicating unknown size. if it is non-zero, it must be accurate. for 0 size frames, use compressBegin_advanced */<b> +</pre></b><BR> +<a name="Chapter19"></a><h2>Buffer-less streaming decompression (synchronous mode)</h2><pre> + A ZSTD_DCtx object is required to track streaming operations. + Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it. + A ZSTD_DCtx object can be re-used multiple times. + + First typical operation is to retrieve frame parameters, using ZSTD_getFrameHeader(). + Frame header is extracted from the beginning of compressed frame, so providing only the frame's beginning is enough. + Data fragment must be large enough to ensure successful decoding. + `ZSTD_frameHeaderSize_max` bytes is guaranteed to always be large enough. + @result : 0 : successful decoding, the `ZSTD_frameHeader` structure is correctly filled. + >0 : `srcSize` is too small, please provide at least @result bytes on next attempt. + errorCode, which can be tested using ZSTD_isError(). + + It fills a ZSTD_frameHeader structure with important information to correctly decode the frame, + such as the dictionary ID, content size, or maximum back-reference distance (`windowSize`). + Note that these values could be wrong, either because of data corruption, or because a 3rd party deliberately spoofs false information. + As a consequence, check that values remain within valid application range. + For example, do not allocate memory blindly, check that `windowSize` is within expectation. + Each application can set its own limits, depending on local restrictions. + For extended interoperability, it is recommended to support `windowSize` of at least 8 MB. + + ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize` bytes. + ZSTD_decompressContinue() is very sensitive to contiguity, + if 2 blocks don't follow each other, make sure that either the compressor breaks contiguity at the same place, + or that previous contiguous segment is large enough to properly handle maximum back-reference distance. + There are multiple ways to guarantee this condition. + + The most memory efficient way is to use a round buffer of sufficient size. + Sufficient size is determined by invoking ZSTD_decodingBufferSize_min(), + which can @return an error code if required value is too large for current system (in 32-bits mode). + In a round buffer methodology, ZSTD_decompressContinue() decompresses each block next to previous one, + up to the moment there is not enough room left in the buffer to guarantee decoding another full block, + which maximum size is provided in `ZSTD_frameHeader` structure, field `blockSizeMax`. + At which point, decoding can resume from the beginning of the buffer. + Note that already decoded data stored in the buffer should be flushed before being overwritten. + + There are alternatives possible, for example using two or more buffers of size `windowSize` each, though they consume more memory. + + Finally, if you control the compression process, you can also ignore all buffer size rules, + as long as the encoder and decoder progress in "lock-step", + aka use exactly the same buffer sizes, break contiguity at the same place, etc. + + Once buffers are setup, start decompression, with ZSTD_decompressBegin(). + If decompression requires a dictionary, use ZSTD_decompressBegin_usingDict() or ZSTD_decompressBegin_usingDDict(). + + Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively. + ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize' to ZSTD_decompressContinue(). + ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will fail. + + @result of ZSTD_decompressContinue() is the number of bytes regenerated within 'dst' (necessarily <= dstCapacity). + It can be zero : it just means ZSTD_decompressContinue() has decoded some metadata item. + It can also be an error code, which can be tested with ZSTD_isError(). + + A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero. + Context can then be reset to start a new decompression. + + Note : it's possible to know if next input to present is a header or a block, using ZSTD_nextInputType(). + This information is not required to properly decode a frame. + + == Special case : skippable frames + + Skippable frames allow integration of user-defined data into a flow of concatenated frames. + Skippable frames will be ignored (skipped) by decompressor. + The format of skippable frames is as follows : + a) Skippable frame ID - 4 Bytes, Little endian format, any value from 0x184D2A50 to 0x184D2A5F + b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits + c) Frame Content - any content (User Data) of length equal to Frame Size + For skippable frames ZSTD_getFrameHeader() returns zfhPtr->frameType==ZSTD_skippableFrame. + For skippable frames ZSTD_decompressContinue() always returns 0 : it only skips the content. +<BR></pre> + +<h3>Buffer-less streaming decompression functions</h3><pre></pre><b><pre>typedef enum { ZSTD_frame, ZSTD_skippableFrame } ZSTD_frameType_e; +typedef struct { + unsigned long long frameContentSize; </b>/* if == ZSTD_CONTENTSIZE_UNKNOWN, it means this field is not available. 0 means "empty" */<b> + unsigned long long windowSize; </b>/* can be very large, up to <= frameContentSize */<b> + unsigned blockSizeMax; + ZSTD_frameType_e frameType; </b>/* if == ZSTD_skippableFrame, frameContentSize is the size of skippable content */<b> + unsigned headerSize; + unsigned dictID; + unsigned checksumFlag; +} ZSTD_frameHeader; +size_t ZSTD_getFrameHeader(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize); </b>/**< doesn't consume input */<b> +size_t ZSTD_decodingBufferSize_min(unsigned long long windowSize, unsigned long long frameContentSize); </b>/**< when frame content size is not known, pass in frameContentSize == ZSTD_CONTENTSIZE_UNKNOWN */<b> +</pre></b><BR> +<pre><b>typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e; +</b></pre><BR> +<a name="Chapter20"></a><h2>New advanced API (experimental)</h2><pre></pre> + +<pre><b>typedef enum { + </b>/* Question : should we have a format ZSTD_f_auto ?<b> + * For the time being, it would mean exactly the same as ZSTD_f_zstd1. + * But, in the future, should several formats be supported, + * on the compression side, it would mean "default format". + * On the decompression side, it would mean "multi format", + * and ZSTD_f_zstd1 could be reserved to mean "accept *only* zstd frames". + * Since meaning is a little different, another option could be to define different enums for compression and decompression. + * This question could be kept for later, when there are actually multiple formats to support, + * but there is also the question of pinning enum values, and pinning value `0` is especially important */ + ZSTD_f_zstd1 = 0, </b>/* zstd frame format, specified in zstd_compression_format.md (default) */<b> + ZSTD_f_zstd1_magicless, </b>/* Variant of zstd frame format, without initial 4-bytes magic number.<b> + * Useful to save 4 bytes per generated frame. + * Decoder cannot recognise automatically this format, requiring instructions. */ +} ZSTD_format_e; +</b></pre><BR> +<pre><b>typedef enum { + </b>/* compression format */<b> + ZSTD_p_format = 10, </b>/* See ZSTD_format_e enum definition.<b> + * Cast selected format as unsigned for ZSTD_CCtx_setParameter() compatibility. */ + + </b>/* compression parameters */<b> + ZSTD_p_compressionLevel=100, </b>/* Update all compression parameters according to pre-defined cLevel table<b> + * Default level is ZSTD_CLEVEL_DEFAULT==3. + * Special: value 0 means "do not change cLevel". */ + ZSTD_p_windowLog, </b>/* Maximum allowed back-reference distance, expressed as power of 2.<b> + * Must be clamped between ZSTD_WINDOWLOG_MIN and ZSTD_WINDOWLOG_MAX. + * Special: value 0 means "do not change windowLog". + * Note: Using a window size greater than ZSTD_MAXWINDOWSIZE_DEFAULT (default: 2^27) + * requires setting the maximum window size at least as large during decompression. */ + ZSTD_p_hashLog, </b>/* Size of the probe table, as a power of 2.<b> + * Resulting table size is (1 << (hashLog+2)). + * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX. + * Larger tables improve compression ratio of strategies <= dFast, + * and improve speed of strategies > dFast. + * Special: value 0 means "do not change hashLog". */ + ZSTD_p_chainLog, </b>/* Size of the full-search table, as a power of 2.<b> + * Resulting table size is (1 << (chainLog+2)). + * Larger tables result in better and slower compression. + * This parameter is useless when using "fast" strategy. + * Special: value 0 means "do not change chainLog". */ + ZSTD_p_searchLog, </b>/* Number of search attempts, as a power of 2.<b> + * More attempts result in better and slower compression. + * This parameter is useless when using "fast" and "dFast" strategies. + * Special: value 0 means "do not change searchLog". */ + ZSTD_p_minMatch, </b>/* Minimum size of searched matches (note : repCode matches can be smaller).<b> + * Larger values make faster compression and decompression, but decrease ratio. + * Must be clamped between ZSTD_SEARCHLENGTH_MIN and ZSTD_SEARCHLENGTH_MAX. + * Note that currently, for all strategies < btopt, effective minimum is 4. + * Note that currently, for all strategies > fast, effective maximum is 6. + * Special: value 0 means "do not change minMatchLength". */ + ZSTD_p_targetLength, </b>/* Only useful for strategies >= btopt.<b> + * Length of Match considered "good enough" to stop search. + * Larger values make compression stronger and slower. + * Special: value 0 means "do not change targetLength". */ + ZSTD_p_compressionStrategy, </b>/* See ZSTD_strategy enum definition.<b> + * Cast selected strategy as unsigned for ZSTD_CCtx_setParameter() compatibility. + * The higher the value of selected strategy, the more complex it is, + * resulting in stronger and slower compression. + * Special: value 0 means "do not change strategy". */ + + </b>/* frame parameters */<b> + ZSTD_p_contentSizeFlag=200, </b>/* Content size is written into frame header _whenever known_ (default:1)<b> + * note that content size must be known at the beginning, + * it is sent using ZSTD_CCtx_setPledgedSrcSize() */ + ZSTD_p_checksumFlag, </b>/* A 32-bits checksum of content is written at end of frame (default:0) */<b> + ZSTD_p_dictIDFlag, </b>/* When applicable, dictID of dictionary is provided in frame header (default:1) */<b> + + </b>/* multi-threading parameters */<b> + ZSTD_p_nbThreads=400, </b>/* Select how many threads a compression job can spawn (default:1)<b> + * More threads improve speed, but also increase memory usage. + * Can only receive a value > 1 if ZSTD_MULTITHREAD is enabled. + * Special: value 0 means "do not change nbThreads" */ + ZSTD_p_jobSize, </b>/* Size of a compression job. Each compression job is completed in parallel.<b> + * 0 means default, which is dynamically determined based on compression parameters. + * Job size must be a minimum of overlapSize, or 1 KB, whichever is largest + * The minimum size is automatically and transparently enforced */ + ZSTD_p_overlapSizeLog, </b>/* Size of previous input reloaded at the beginning of each job.<b> + * 0 => no overlap, 6(default) => use 1/8th of windowSize, >=9 => use full windowSize */ + + </b>/* advanced parameters - may not remain available after API update */<b> + ZSTD_p_forceMaxWindow=1100, </b>/* Force back-reference distances to remain < windowSize,<b> + * even when referencing into Dictionary content (default:0) */ + ZSTD_p_enableLongDistanceMatching=1200, </b>/* Enable long distance matching.<b> + * This parameter is designed to improve the compression + * ratio for large inputs with long distance matches. + * This increases the memory usage as well as window size. + * Note: setting this parameter sets all the LDM parameters + * as well as ZSTD_p_windowLog. It should be set after + * ZSTD_p_compressionLevel and before ZSTD_p_windowLog and + * other LDM parameters. Setting the compression level + * after this parameter overrides the window log, though LDM + * will remain enabled until explicitly disabled. */ + ZSTD_p_ldmHashLog, </b>/* Size of the table for long distance matching, as a power of 2.<b> + * Larger values increase memory usage and compression ratio, but decrease + * compression speed. + * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX + * (default: windowlog - 7). */ + ZSTD_p_ldmMinMatch, </b>/* Minimum size of searched matches for long distance matcher.<b> + * Larger/too small values usually decrease compression ratio. + * Must be clamped between ZSTD_LDM_MINMATCH_MIN + * and ZSTD_LDM_MINMATCH_MAX (default: 64). */ + ZSTD_p_ldmBucketSizeLog, </b>/* Log size of each bucket in the LDM hash table for collision resolution.<b> + * Larger values usually improve collision resolution but may decrease + * compression speed. + * The maximum value is ZSTD_LDM_BUCKETSIZELOG_MAX (default: 3). */ + ZSTD_p_ldmHashEveryLog, </b>/* Frequency of inserting/looking up entries in the LDM hash table.<b> + * The default is MAX(0, (windowLog - ldmHashLog)) to + * optimize hash table usage. + * Larger values improve compression speed. Deviating far from the + * default value will likely result in a decrease in compression ratio. + * Must be clamped between 0 and ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN. */ + +} ZSTD_cParameter; +</b></pre><BR> +<pre><b>size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, unsigned value); +</b><p> Set one compression parameter, selected by enum ZSTD_cParameter. + Note : when `value` is an enum, cast it to unsigned for proper type checking. + @result : 0, or an error code (which can be tested with ZSTD_isError()). +</p></pre><BR> + +<pre><b>size_t ZSTD_CCtx_setPledgedSrcSize(ZSTD_CCtx* cctx, unsigned long long pledgedSrcSize); +</b><p> Total input data size to be compressed as a single frame. + This value will be controlled at the end, and result in error if not respected. + @result : 0, or an error code (which can be tested with ZSTD_isError()). + Note 1 : 0 means zero, empty. + In order to mean "unknown content size", pass constant ZSTD_CONTENTSIZE_UNKNOWN. + Note that ZSTD_CONTENTSIZE_UNKNOWN is default value for new compression jobs. + Note 2 : If all data is provided and consumed in a single round, + this value is overriden by srcSize instead. +</p></pre><BR> + +<pre><b>size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, size_t dictSize); +size_t ZSTD_CCtx_loadDictionary_byReference(ZSTD_CCtx* cctx, const void* dict, size_t dictSize); +size_t ZSTD_CCtx_loadDictionary_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictMode_e dictMode); +</b><p> Create an internal CDict from dict buffer. + Decompression will have to use same buffer. + @result : 0, or an error code (which can be tested with ZSTD_isError()). + Special : Adding a NULL (or 0-size) dictionary invalidates any previous dictionary, + meaning "return to no-dictionary mode". + Note 1 : `dict` content will be copied internally. Use + ZSTD_CCtx_loadDictionary_byReference() to reference dictionary + content instead. The dictionary buffer must then outlive its + users. + Note 2 : Loading a dictionary involves building tables, which are dependent on compression parameters. + For this reason, compression parameters cannot be changed anymore after loading a dictionary. + It's also a CPU-heavy operation, with non-negligible impact on latency. + Note 3 : Dictionary will be used for all future compression jobs. + To return to "no-dictionary" situation, load a NULL dictionary + Note 5 : Use ZSTD_CCtx_loadDictionary_advanced() to select how dictionary + content will be interpreted. + +</p></pre><BR> + +<pre><b>size_t ZSTD_CCtx_refCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); +</b><p> Reference a prepared dictionary, to be used for all next compression jobs. + Note that compression parameters are enforced from within CDict, + and supercede any compression parameter previously set within CCtx. + The dictionary will remain valid for future compression jobs using same CCtx. + @result : 0, or an error code (which can be tested with ZSTD_isError()). + Special : adding a NULL CDict means "return to no-dictionary mode". + Note 1 : Currently, only one dictionary can be managed. + Adding a new dictionary effectively "discards" any previous one. + Note 2 : CDict is just referenced, its lifetime must outlive CCtx. + +</p></pre><BR> + +<pre><b>size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize); +size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize, ZSTD_dictMode_e dictMode); +</b><p> Reference a prefix (single-usage dictionary) for next compression job. + Decompression need same prefix to properly regenerate data. + Prefix is **only used once**. Tables are discarded at end of compression job. + Subsequent compression jobs will be done without prefix (if none is explicitly referenced). + If there is a need to use same prefix multiple times, consider embedding it into a ZSTD_CDict instead. + @result : 0, or an error code (which can be tested with ZSTD_isError()). + Special : Adding any prefix (including NULL) invalidates any previous prefix or dictionary + Note 1 : Prefix buffer is referenced. It must outlive compression job. + Note 2 : Referencing a prefix involves building tables, which are dependent on compression parameters. + It's a CPU-heavy operation, with non-negligible impact on latency. + Note 3 : By default, the prefix is treated as raw content + (ZSTD_dm_rawContent). Use ZSTD_CCtx_refPrefix_advanced() to alter + dictMode. +</p></pre><BR> + +<pre><b>typedef enum { + ZSTD_e_continue=0, </b>/* collect more data, encoder transparently decides when to output result, for optimal conditions */<b> + ZSTD_e_flush, </b>/* flush any data provided so far - frame will continue, future data can still reference previous data for better compression */<b> + ZSTD_e_end </b>/* flush any remaining data and close current frame. Any additional data starts a new frame. */<b> +} ZSTD_EndDirective; +</b></pre><BR> +<pre><b>size_t ZSTD_compress_generic (ZSTD_CCtx* cctx, + ZSTD_outBuffer* output, + ZSTD_inBuffer* input, + ZSTD_EndDirective endOp); +</b><p> Behave about the same as ZSTD_compressStream. To note : + - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_setParameter() + - Compression parameters cannot be changed once compression is started. + - outpot->pos must be <= dstCapacity, input->pos must be <= srcSize + - outpot->pos and input->pos will be updated. They are guaranteed to remain below their respective limit. + - @return provides the minimum amount of data still to flush from internal buffers + or an error code, which can be tested using ZSTD_isError(). + if @return != 0, flush is not fully completed, there is some data left within internal buffers. + - after a ZSTD_e_end directive, if internal buffer is not fully flushed, + only ZSTD_e_end or ZSTD_e_flush operations are allowed. + It is necessary to fully flush internal buffers + before starting a new compression job, or changing compression parameters. + +</p></pre><BR> + +<pre><b>void ZSTD_CCtx_reset(ZSTD_CCtx* cctx); </b>/* Not ready yet ! */<b> +</b><p> Return a CCtx to clean state. + Useful after an error, or to interrupt an ongoing compression job and start a new one. + Any internal data not yet flushed is cancelled. + Dictionary (if any) is dropped. + All parameters are back to default values. + It's possible to modify compression parameters after a reset. + +</p></pre><BR> + +<pre><b>size_t ZSTD_compress_generic_simpleArgs ( + ZSTD_CCtx* cctx, + void* dst, size_t dstCapacity, size_t* dstPos, + const void* src, size_t srcSize, size_t* srcPos, + ZSTD_EndDirective endOp); +</b><p> Same as ZSTD_compress_generic(), + but using only integral types as arguments. + Argument list is larger than ZSTD_{in,out}Buffer, + but can be helpful for binders from dynamic languages + which have troubles handling structures containing memory pointers. + +</p></pre><BR> + +<pre><b>ZSTD_CCtx_params* ZSTD_createCCtxParams(void); +</b><p> Quick howto : + - ZSTD_createCCtxParams() : Create a ZSTD_CCtx_params structure + - ZSTD_CCtxParam_setParameter() : Push parameters one by one into + an existing ZSTD_CCtx_params structure. + This is similar to + ZSTD_CCtx_setParameter(). + - ZSTD_CCtx_setParametersUsingCCtxParams() : Apply parameters to + an existing CCtx. + These parameters will be applied to + all subsequent compression jobs. + - ZSTD_compress_generic() : Do compression using the CCtx. + - ZSTD_freeCCtxParams() : Free the memory. + + This can be used with ZSTD_estimateCCtxSize_advanced_usingCCtxParams() + for static allocation for single-threaded compression. + +</p></pre><BR> + +<pre><b>size_t ZSTD_resetCCtxParams(ZSTD_CCtx_params* params); +</b><p> Reset params to default, with the default compression level. + +</p></pre><BR> + +<pre><b>size_t ZSTD_initCCtxParams(ZSTD_CCtx_params* cctxParams, int compressionLevel); +</b><p> Initializes the compression parameters of cctxParams according to + compression level. All other parameters are reset to their default values. + +</p></pre><BR> + +<pre><b>size_t ZSTD_initCCtxParams_advanced(ZSTD_CCtx_params* cctxParams, ZSTD_parameters params); +</b><p> Initializes the compression and frame parameters of cctxParams according to + params. All other parameters are reset to their default values. + +</p></pre><BR> + +<pre><b>size_t ZSTD_CCtxParam_setParameter(ZSTD_CCtx_params* params, ZSTD_cParameter param, unsigned value); +</b><p> Similar to ZSTD_CCtx_setParameter. + Set one compression parameter, selected by enum ZSTD_cParameter. + Parameters must be applied to a ZSTD_CCtx using ZSTD_CCtx_setParametersUsingCCtxParams(). + Note : when `value` is an enum, cast it to unsigned for proper type checking. + @result : 0, or an error code (which can be tested with ZSTD_isError()). + +</p></pre><BR> + +<pre><b>size_t ZSTD_CCtx_setParametersUsingCCtxParams( + ZSTD_CCtx* cctx, const ZSTD_CCtx_params* params); +</b><p> Apply a set of ZSTD_CCtx_params to the compression context. + This must be done before the dictionary is loaded. + The pledgedSrcSize is treated as unknown. + Multithreading parameters are applied only if nbThreads > 1. + +</p></pre><BR> + +<h3>Advanced parameters for decompression API</h3><pre></pre><b><pre></pre></b><BR> +<pre><b>size_t ZSTD_DCtx_loadDictionary(ZSTD_DCtx* dctx, const void* dict, size_t dictSize); </b>/* not implemented */<b> +size_t ZSTD_DCtx_loadDictionary_byReference(ZSTD_DCtx* dctx, const void* dict, size_t dictSize); </b>/* not implemented */<b> +size_t ZSTD_DCtx_loadDictionary_advanced(ZSTD_DCtx* dctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictMode_e dictMode); </b>/* not implemented */<b> +</b><p> Create an internal DDict from dict buffer, + to be used to decompress next frames. + @result : 0, or an error code (which can be tested with ZSTD_isError()). + Special : Adding a NULL (or 0-size) dictionary invalidates any previous dictionary, + meaning "return to no-dictionary mode". + Note 1 : `dict` content will be copied internally. + Use ZSTD_DCtx_loadDictionary_byReference() + to reference dictionary content instead. + In which case, the dictionary buffer must outlive its users. + Note 2 : Loading a dictionary involves building tables, + which has a non-negligible impact on CPU usage and latency. + Note 3 : Use ZSTD_DCtx_loadDictionary_advanced() to select + how dictionary content will be interpreted and loaded. + +</p></pre><BR> + +<pre><b>size_t ZSTD_DCtx_refDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict); </b>/* not implemented */<b> +</b><p> Reference a prepared dictionary, to be used to decompress next frames. + The dictionary remains active for decompression of future frames using same DCtx. + @result : 0, or an error code (which can be tested with ZSTD_isError()). + Note 1 : Currently, only one dictionary can be managed. + Referencing a new dictionary effectively "discards" any previous one. + Special : adding a NULL DDict means "return to no-dictionary mode". + Note 2 : DDict is just referenced, its lifetime must outlive its usage from DCtx. + +</p></pre><BR> + +<pre><b>size_t ZSTD_DCtx_refPrefix(ZSTD_DCtx* dctx, const void* prefix, size_t prefixSize); </b>/* not implemented */<b> +size_t ZSTD_DCtx_refPrefix_advanced(ZSTD_DCtx* dctx, const void* prefix, size_t prefixSize, ZSTD_dictMode_e dictMode); </b>/* not implemented */<b> +</b><p> Reference a prefix (single-usage dictionary) for next compression job. + Prefix is **only used once**. It must be explicitly referenced before each frame. + If there is a need to use same prefix multiple times, consider embedding it into a ZSTD_DDict instead. + @result : 0, or an error code (which can be tested with ZSTD_isError()). + Note 1 : Adding any prefix (including NULL) invalidates any previously set prefix or dictionary + Note 2 : Prefix buffer is referenced. It must outlive compression job. + Note 3 : By default, the prefix is treated as raw content (ZSTD_dm_rawContent). + Use ZSTD_CCtx_refPrefix_advanced() to alter dictMode. + Note 4 : Referencing a raw content prefix has almost no cpu nor memory cost. + +</p></pre><BR> + +<pre><b>size_t ZSTD_DCtx_setMaxWindowSize(ZSTD_DCtx* dctx, size_t maxWindowSize); +</b><p> Refuses allocating internal buffers for frames requiring a window size larger than provided limit. + This is useful to prevent a decoder context from reserving too much memory for itself (potential attack scenario). + This parameter is only useful in streaming mode, since no internal buffer is allocated in direct mode. + By default, a decompression context accepts all window sizes <= (1 << ZSTD_WINDOWLOG_MAX) + @return : 0, or an error code (which can be tested using ZSTD_isError()). + +</p></pre><BR> + +<pre><b>size_t ZSTD_DCtx_setFormat(ZSTD_DCtx* dctx, ZSTD_format_e format); +</b><p> Instruct the decoder context about what kind of data to decode next. + This instruction is mandatory to decode data without a fully-formed header, + such ZSTD_f_zstd1_magicless for example. + @return : 0, or an error code (which can be tested using ZSTD_isError()). + +</p></pre><BR> + +<pre><b>size_t ZSTD_decompress_generic(ZSTD_DCtx* dctx, + ZSTD_outBuffer* output, + ZSTD_inBuffer* input); +</b><p> Behave the same as ZSTD_decompressStream. + Decompression parameters cannot be changed once decompression is started. + @return : an error code, which can be tested using ZSTD_isError() + if >0, a hint, nb of expected input bytes for next invocation. + `0` means : a frame has just been fully decoded and flushed. + +</p></pre><BR> + +<pre><b>size_t ZSTD_decompress_generic_simpleArgs ( + ZSTD_DCtx* dctx, + void* dst, size_t dstCapacity, size_t* dstPos, + const void* src, size_t srcSize, size_t* srcPos); +</b><p> Same as ZSTD_decompress_generic(), + but using only integral types as arguments. + Argument list is larger than ZSTD_{in,out}Buffer, + but can be helpful for binders from dynamic languages + which have troubles handling structures containing memory pointers. + +</p></pre><BR> + +<pre><b>void ZSTD_DCtx_reset(ZSTD_DCtx* dctx); +</b><p> Return a DCtx to clean state. + If a decompression was ongoing, any internal data not yet flushed is cancelled. + All parameters are back to default values, including sticky ones. + Dictionary (if any) is dropped. + Parameters can be modified again after a reset. + +</p></pre><BR> + +<a name="Chapter21"></a><h2>Block level API</h2><pre></pre> + +<pre><b></b><p> Frame metadata cost is typically ~18 bytes, which can be non-negligible for very small blocks (< 100 bytes). + User will have to take in charge required information to regenerate data, such as compressed and content sizes. + + A few rules to respect : + - Compressing and decompressing require a context structure + + Use ZSTD_createCCtx() and ZSTD_createDCtx() + - It is necessary to init context before starting + + compression : any ZSTD_compressBegin*() variant, including with dictionary + + decompression : any ZSTD_decompressBegin*() variant, including with dictionary + + copyCCtx() and copyDCtx() can be used too + - Block size is limited, it must be <= ZSTD_getBlockSize() <= ZSTD_BLOCKSIZE_MAX == 128 KB + + If input is larger than a block size, it's necessary to split input data into multiple blocks + + For inputs larger than a single block size, consider using the regular ZSTD_compress() instead. + Frame metadata is not that costly, and quickly becomes negligible as source size grows larger. + - When a block is considered not compressible enough, ZSTD_compressBlock() result will be zero. + In which case, nothing is produced into `dst`. + + User must test for such outcome and deal directly with uncompressed data + + ZSTD_decompressBlock() doesn't accept uncompressed data as input !!! + + In case of multiple successive blocks, should some of them be uncompressed, + decoder must be informed of their existence in order to follow proper history. + Use ZSTD_insertBlock() for such a case. +</p></pre><BR> + +<h3>Raw zstd block functions</h3><pre></pre><b><pre>size_t ZSTD_getBlockSize (const ZSTD_CCtx* cctx); +size_t ZSTD_compressBlock (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize); +size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize); +size_t ZSTD_insertBlock(ZSTD_DCtx* dctx, const void* blockStart, size_t blockSize); </b>/**< insert uncompressed block into `dctx` history. Useful for multi-blocks decompression */<b> +</pre></b><BR> +</html> +</body> |