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diff --git a/doc/zstd_manual.html b/doc/zstd_manual.html new file mode 100644 index 000000000000..204f56ea5f21 --- /dev/null +++ b/doc/zstd_manual.html @@ -0,0 +1,664 @@ +<html> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> +<title>zstd 1.1.4 Manual</title> +</head> +<body> +<h1>zstd 1.1.4 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">Fast 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">Compressed size functions</a></li> +<li><a href="#Chapter13">Decompressed size functions</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">Block functions</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 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 compression with 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. + These 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>/**< library version number; to be used when checking 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. + 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>unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize); +</b><p> NOTE: This function is planned to be obsolete, in favour of ZSTD_getFrameContentSize. + ZSTD_getFrameContentSize functions the same way, returning the decompressed size of a single + frame, but distinguishes empty frames from frames with an unknown size, or errors. + + Additionally, ZSTD_findDecompressedSize can be used instead. It can handle multiple + concatenated frames in one buffer, and so is more general. + As a result however, it requires more computation and entire frames to be passed to it, + as opposed to ZSTD_getFrameContentSize which requires only a single frame's header. + + 'src' is the start of a zstd compressed frame. + @return : content size to be decompressed, as a 64-bits value _if known_, 0 otherwise. + note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode. + When `return==0`, data to decompress could be any size. + In which case, it's necessary to use streaming mode to decompress data. + Optionally, application can still use ZSTD_decompress() while relying on implied limits. + (For example, data may be necessarily cut into blocks <= 16 KB). + 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 : when `return==0`, if precise failure cause is needed, use ZSTD_getFrameParams() to know more. +</p></pre><BR> + +<h3>Helper functions</h3><pre></pre><b><pre>int ZSTD_maxCLevel(void); </b>/*!< maximum compression level available */<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> +</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 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_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>Fast 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 used by multiple threads concurrently, as its usage is read-only. + `dictBuffer` can be released after ZSTD_CDict creation, as 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. +</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. + Similar to ZSTD_flushStream(), it may not be able to flush the full content if `output->size` is too small. + In which case, call again ZSTD_endStream() to complete the flush. + @return : nb of bytes still present within internal buffer (0 if it's empty, hence compression completed) + or an error code, which can be tested using ZSTD_isError(). + + +<BR></pre> + +<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> + +<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 they may change in the future. + They are provided for advanced usages. + 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, ZSTD_dfast, ZSTD_greedy, ZSTD_lazy, ZSTD_lazy2, ZSTD_btlazy2, ZSTD_btopt, ZSTD_btopt2 } 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; +</pre></b><BR> +<a name="Chapter12"></a><h2>Compressed 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 frame pointed to by `src`, suitable to pass to + `ZSTD_decompress` or similar, or an error code if given invalid input. +</p></pre><BR> + +<a name="Chapter13"></a><h2>Decompressed size functions</h2><pre></pre> + +<pre><b>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. A value greater than or equal + to `ZSTD_frameHeaderSize_max` is guaranteed to be large enough in all cases. + @return : decompressed size of the frame pointed to be `src` if known, otherwise + - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined + - ZSTD_CONTENTSIZE_ERROR if an error occurred (e.g. invalid magic number, srcSize too small) +</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 `srcSize` bytes after `src`) + @return : the decompressed size of all data in the contained frames, as a 64-bit value _if known_ + - 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. + Optionally, application can still use ZSTD_decompress() while relying on implied limits. + (For example, data may be necessarily cut into blocks <= 16 KB). + 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 efficient as most of the data is skipped, + however it does mean that all frame data must be present and valid. +</p></pre><BR> + +<a name="Chapter14"></a><h2>Advanced compression functions</h2><pre></pre> + +<pre><b>size_t ZSTD_estimateCCtxSize(ZSTD_compressionParameters cParams); +</b><p> Gives the amount of memory allocated for a ZSTD_CCtx given a set of compression parameters. + `frameContentSize` is an optional parameter, provide `0` if unknown +</p></pre><BR> + +<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>size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx); +</b><p> Gives the amount of memory used by a given ZSTD_CCtx +</p></pre><BR> + +<pre><b>typedef enum { + ZSTD_p_forceWindow, </b>/* Force back-references to remain < windowSize, even when referencing Dictionary content (default:0) */<b> + ZSTD_p_forceRawDict </b>/* Force loading dictionary in "content-only" mode (no header analysis) */<b> +} ZSTD_CCtxParameter; +</b></pre><BR> +<pre><b>size_t ZSTD_setCCtxParameter(ZSTD_CCtx* cctx, ZSTD_CCtxParameter param, unsigned value); +</b><p> Set advanced parameters, selected through enum ZSTD_CCtxParameter + @result : 0, or an error code (which can be tested with ZSTD_isError()) +</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>ZSTD_CDict* ZSTD_createCDict_advanced(const void* dict, size_t dictSize, unsigned byReference, + ZSTD_parameters params, ZSTD_customMem customMem); +</b><p> Create a ZSTD_CDict using external alloc and free, and customized compression parameters +</p></pre><BR> + +<pre><b>size_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict); +</b><p> Gives the amount of memory used by a given ZSTD_sizeof_CDict +</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* ctx, + 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 of each compression parameter +</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>size_t ZSTD_estimateDCtxSize(void); +</b><p> Gives the potential amount of memory allocated to create a ZSTD_DCtx +</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>size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx); +</b><p> Gives the amount of memory used by a given ZSTD_DCtx +</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 simply 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, + unsigned byReference, ZSTD_customMem customMem); +</b><p> Create a ZSTD_DDict using external alloc and free, optionally by reference +</p></pre><BR> + +<pre><b>size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict); +</b><p> Gives the amount of memory used by a given ZSTD_DDict +</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 used ZSTD_getFrameParams(), 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); +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>/**< note: a dict will not be used if dict == NULL or dictSize < 8 */<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 */<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_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize); </b>/**< re-use compression parameters from previous init; skip dictionary loading stage; zcs must be init at least once before. note: pledgedSrcSize must be correct, a size of 0 means unknown. for a frame size of 0 use initCStream_advanced */<b> +size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs); +</pre></b><BR> +<h3>Advanced Streaming decompression functions</h3><pre></pre><b><pre>typedef enum { DStream_p_maxWindowSize } ZSTD_DStreamParameter_e; +ZSTD_DStream* ZSTD_createDStream_advanced(ZSTD_customMem customMem); +size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize); </b>/**< note: a dict will not be used if dict == NULL or dictSize < 8 */<b> +size_t ZSTD_setDStreamParameter(ZSTD_DStream* zds, ZSTD_DStreamParameter_e paramType, unsigned paramValue); +size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict); </b>/**< note : ddict will just be referenced, and must outlive decompression session */<b> +size_t ZSTD_resetDStream(ZSTD_DStream* zds); </b>/**< re-use decompression parameters from previous init; saves dictionary loading */<b> +size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds); +</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 many restrictions (documented below). + Prefer using 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 buffer only. + - Interface is synchronous : input is consumed entirely and produce 1+ (or more) 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 will be considered unfinished (corrupted) by decoders. + + `ZSTD_CCtx` object can be re-used (ZSTD_compressBegin()) to compress some new frame. +<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_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> +size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict, 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> +size_t ZSTD_compressContinue(ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize); +size_t ZSTD_compressEnd(ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize); +</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_getFrameParams(). + It fills a ZSTD_frameParams structure which provide important information to correctly decode the frame, + such as the minimum rolling buffer size to allocate to decompress data (`windowSize`), + and the dictionary ID used. + (Note : content size is optional, it may not be present. 0 means : content size unknown). + Note that these values could be wrong, either because of data malformation, or because an attacker is spoofing deliberate false information. + As a consequence, check that values remain within valid application range, especially `windowSize`, before allocation. + Each application can set its own limit, depending on local restrictions. For extended interoperability, it is recommended to support at least 8 MB. + Frame parameters are extracted from the beginning of the compressed frame. + Data fragment must be large enough to ensure successful decoding, typically `ZSTD_frameHeaderSize_max` bytes. + @result : 0 : successful decoding, the `ZSTD_frameParams` 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(). + + Start decompression, with ZSTD_decompressBegin() or ZSTD_decompressBegin_usingDict(). + Alternatively, you can copy a prepared context, using ZSTD_copyDCtx(). + + 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, which is not an error; it just means ZSTD_decompressContinue() has decoded some metadata item. + It can also be an error code, which can be tested with ZSTD_isError(). + + ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize`. + They should preferably be located contiguously, prior to current block. + Alternatively, a round buffer of sufficient size is also possible. Sufficient size is determined by frame parameters. + 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. + + 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 a 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_decompressContinue() always returns 0. + For skippable frames ZSTD_getFrameParams() returns fparamsPtr->windowLog==0 what means that a frame is skippable. + Note : If fparamsPtr->frameContentSize==0, it is ambiguous: the frame might actually be a Zstd encoded frame with no content. + For purposes of decompression, it is valid in both cases to skip the frame using + ZSTD_findFrameCompressedSize to find its size in bytes. + It also returns Frame Size as fparamsPtr->frameContentSize. +<BR></pre> + +<pre><b>typedef struct { + unsigned long long frameContentSize; + unsigned windowSize; + unsigned dictID; + unsigned checksumFlag; +} ZSTD_frameParams; +</b></pre><BR> +<h3>Buffer-less streaming decompression functions</h3><pre></pre><b><pre>size_t ZSTD_getFrameParams(ZSTD_frameParams* fparamsPtr, const void* src, size_t srcSize); </b>/**< doesn't consume input, see details below */<b> +size_t ZSTD_decompressBegin(ZSTD_DCtx* dctx); +size_t ZSTD_decompressBegin_usingDict(ZSTD_DCtx* dctx, const void* dict, size_t dictSize); +void ZSTD_copyDCtx(ZSTD_DCtx* dctx, const ZSTD_DCtx* preparedDCtx); +size_t ZSTD_nextSrcSizeToDecompress(ZSTD_DCtx* dctx); +size_t ZSTD_decompressContinue(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize); +typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e; +ZSTD_nextInputType_e ZSTD_nextInputType(ZSTD_DCtx* dctx); +</pre></b><BR> +<a name="Chapter20"></a><h2>Block functions</h2><pre> + Block functions produce and decode raw zstd blocks, without frame metadata. + 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 : ZSTD_compressBegin() + + decompression : ZSTD_decompressBegin() + + variants _usingDict() are also allowed + + copyCCtx() and copyDCtx() work too + - Block size is limited, it must be <= ZSTD_getBlockSizeMax() + + If you need to compress more, cut data into multiple blocks + + Consider using the regular ZSTD_compress() instead, as frame metadata costs become negligible when source size is large. + - 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, decoder must be informed of uncompressed block existence to follow proper history. + Use ZSTD_insertBlock() in such a case. +<BR></pre> + +<h3>Raw zstd block functions</h3><pre></pre><b><pre>size_t ZSTD_getBlockSizeMax(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 block into `dctx` history. Useful for uncompressed blocks */<b> +</pre></b><BR> +</html> +</body> |