Structs
Streaming
Enums
Advanced compression API
Constants
Statics
Functions
ZDICT_trainFromBuffer():
Train a dictionary from an array of samples.
Redirect towards ZDICT_optimizeTrainFromBuffer_fastCover() single-threaded, with d=8, steps=4,
f=20, and accel=1.
Samples must be stored concatenated in a single flat buffer
samplesBuffer,
supplied with an array of sizes samplesSizes, providing the size of each sample, in order.
The resulting dictionary will be saved into dictBuffer.
@return: size of dictionary stored into dictBuffer (<= dictBufferCapacity)
or an error code, which can be tested with ZDICT_isError().
Note: ZDICT_trainFromBuffer() requires about 9 bytes of memory for each input byte.
Tips: In general, a reasonable dictionary has a size of ~ 100 KB.
It’s possible to select smaller or larger size, just by specifying dictBufferCapacity.
In general, it’s recommended to provide a few thousands samples, though this can vary a lot.
It’s recommended that total size of all samples be about ~x100 times the target size of dictionary.ZSTDMT_CCtxParam_setMTCtxParameter()
like ZSTDMT_setMTCtxParameter(), but into a ZSTD_CCtx_Params
ZSTDMT_CCtxParam_setNbWorkers()
Set nbWorkers, and clamp it.
Also reset jobSize and overlapLog
ZSTDMT_compressStream_generic() :
Combines ZSTDMT_compressStream() with optional ZSTDMT_flushStream() or ZSTDMT_endStream()
depending on flush directive.
@return : minimum amount of data still to be flushed
0 if fully flushed
or an error code
note : needs to be init using any ZSTD_initCStream*() variant
ZSTDMT_getFrameProgression():
tells how much data has been consumed (input) and produced (output) for current frame.
able to count progression inside worker threads.
ZSTDMT_initCStream_internal() :
Private use only. Init streaming operation.
expects params to be valid.
must receive dict, or cdict, or none, but not both.
@return : 0, or an error code
ZSTDMT_toFlushNow()
Tell how many bytes are ready to be flushed immediately.
Probe the oldest active job (not yet entirely flushed) and check its output buffer.
If return 0, it means there is no active job,
or, it means oldest job is still active, but everything produced has been flushed so far,
therefore flushing is limited by speed of oldest job.
ZSTDMT_updateCParams_whileCompressing() :
Updates only a selected set of compression parameters, to remain compatible with current frame.
New parameters will be applied to next compression job.
ZSTD_CCtxParam_getParameter() :
Similar to ZSTD_CCtx_getParameter.
Get the requested value of one compression parameter, selected by enum ZSTD_cParameter.
@result : 0, or an error code (which can be tested with ZSTD_isError()).
ZSTD_CCtxParam_setParameter() :
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().
@result : 0, or an error code (which can be tested with ZSTD_isError()).
ZSTD_CCtxParams_init() :
Initializes the compression parameters of cctxParams according to
compression level. All other parameters are reset to their default values.
ZSTD_CCtxParams_init_advanced() :
Initializes the compression and frame parameters of cctxParams according to
params. All other parameters are reset to their default values.
ZSTD_CCtxParams_reset() :
Reset params to default values.
ZSTD_CCtx_getParameter() :
Get the requested compression parameter value, selected by enum ZSTD_cParameter,
and store it into int* value.
@return : 0, or an error code (which can be tested with ZSTD_isError()).
ZSTD_CCtx_loadDictionary() :
Create an internal CDict from
dict buffer.
Decompression will have to use same dictionary.
@result : 0, or an error code (which can be tested with ZSTD_isError()).
Special: Loading a NULL (or 0-size) dictionary invalidates previous dictionary,
meaning “return to no-dictionary mode”.
Note 1 : Dictionary is sticky, it will be used for all future compressed frames.
To return to “no-dictionary” situation, load a NULL dictionary (or reset parameters).
Note 2 : Loading a dictionary involves building tables.
It’s also a CPU consuming operation, with non-negligible impact on latency.
Tables are dependent on compression parameters, and for this reason,
compression parameters can no longer be changed after loading a dictionary.
Note 3 :dict content will be copied internally.
Use experimental ZSTD_CCtx_loadDictionary_byReference() to reference content instead.
In such a case, dictionary buffer must outlive its users.
Note 4 : Use ZSTD_CCtx_loadDictionary_advanced()
to precisely select how dictionary content must be interpreted.ZSTD_CCtx_loadDictionary_advanced() :
Same as ZSTD_CCtx_loadDictionary(), but gives finer control over
how to load the dictionary (by copy ? by reference ?)
and how to interpret it (automatic ? force raw mode ? full mode only ?)
ZSTD_CCtx_loadDictionary_byReference() :
Same as ZSTD_CCtx_loadDictionary(), but dictionary content is referenced, instead of being copied into CCtx.
It saves some memory, but also requires that
dict outlives its usage within cctxZSTD_CCtx_refCDict() :
Reference a prepared dictionary, to be used for all next compressed frames.
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 compressed frames using same CCtx.
@result : 0, or an error code (which can be tested with ZSTD_isError()).
Special : Referencing a NULL CDict means “return to no-dictionary mode”.
Note 1 : Currently, only one dictionary can be managed.
Referencing a new dictionary effectively “discards” any previous one.
Note 2 : CDict is just referenced, its lifetime must outlive its usage within CCtx.
ZSTD_CCtx_refPrefix() :
Reference a prefix (single-usage dictionary) for next compressed frame.
A prefix is only used once. Tables are discarded at end of frame (ZSTD_e_end).
Decompression will need same prefix to properly regenerate data.
Compressing with a prefix is similar in outcome as performing a diff and compressing it,
but performs much faster, especially during decompression (compression speed is tunable with compression level).
@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.
Its content must remain unmodified during compression.
Note 2 : If the intention is to diff some large src data blob with some prior version of itself,
ensure that the window size is large enough to contain the entire source.
See ZSTD_c_windowLog.
Note 3 : Referencing a prefix involves building tables, which are dependent on compression parameters.
It’s a CPU consuming operation, with non-negligible impact on latency.
If there is a need to use the same prefix multiple times, consider loadDictionary instead.
Note 4 : By default, the prefix is interpreted as raw content (ZSTD_dm_rawContent).
Use experimental ZSTD_CCtx_refPrefix_advanced() to alter dictionary interpretation.
ZSTD_CCtx_refPrefix_advanced() :
Same as ZSTD_CCtx_refPrefix(), but gives finer control over
how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?)
ZSTD_CCtx_reset() :
There are 2 different things that can be reset, independently or jointly :
ZSTD_CCtx_setParameter() :
Set one compression parameter, selected by enum ZSTD_cParameter.
All parameters have valid bounds. Bounds can be queried using ZSTD_cParam_getBounds().
Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter).
Setting a parameter is generally only possible during frame initialization (before starting compression).
Exception : when using multi-threading mode (nbWorkers >= 1),
the following parameters can be updated during compression (within same frame):
=> compressionLevel, hashLog, chainLog, searchLog, minMatch, targetLength and strategy.
new parameters will be active for next job only (after a flush()).
@return : an error code (which can be tested using ZSTD_isError()).
ZSTD_CCtx_setParametersUsingCCtxParams() :
Apply a set of ZSTD_CCtx_params to the compression context.
This can be done even after compression is started,
if nbWorkers==0, this will have no impact until a new compression is started.
if nbWorkers>=1, new parameters will be picked up at next job,
with a few restrictions (windowLog, pledgedSrcSize, nbWorkers, jobSize, and overlapLog are not updated).
ZSTD_CCtx_setPledgedSrcSize() :
Total input data size to be compressed as a single frame.
Value will be written in frame header, unless if explicitly forbidden using ZSTD_c_contentSizeFlag.
This value will also be controlled at end of frame, and trigger an error if not respected.
@result : 0, or an error code (which can be tested with ZSTD_isError()).
Note 1 : pledgedSrcSize==0 actually means zero, aka an empty frame.
In order to mean “unknown content size”, pass constant ZSTD_CONTENTSIZE_UNKNOWN.
ZSTD_CONTENTSIZE_UNKNOWN is default value for any new frame.
Note 2 : pledgedSrcSize is only valid once, for the next frame.
It’s discarded at the end of the frame, and replaced by ZSTD_CONTENTSIZE_UNKNOWN.
Note 3 : Whenever all input data is provided and consumed in a single round,
for example with ZSTD_compress2(),
or invoking immediately ZSTD_compressStream2(,,,ZSTD_e_end),
this value is automatically overriden by srcSize instead.
ZSTD_DCtx_loadDictionary() :
Create an internal DDict from dict buffer,
to be used to decompress next frames.
The dictionary remains valid for all future frames, until explicitly invalidated.
@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 : Loading a dictionary involves building tables,
which has a non-negligible impact on CPU usage and latency.
It’s recommended to “load once, use many times”, to amortize the cost
Note 2 :
dict content will be copied internally, so dict can be released after loading.
Use ZSTD_DCtx_loadDictionary_byReference() to reference dictionary content instead.
Note 3 : Use ZSTD_DCtx_loadDictionary_advanced() to take control of
how dictionary content is loaded and interpreted.ZSTD_DCtx_loadDictionary_advanced() :
Same as ZSTD_DCtx_loadDictionary(),
but gives direct control over
how to load the dictionary (by copy ? by reference ?)
and how to interpret it (automatic ? force raw mode ? full mode only ?).
ZSTD_DCtx_loadDictionary_byReference() :
Same as ZSTD_DCtx_loadDictionary(),
but references
dict content instead of copying it into dctx.
This saves memory if dict remains around.,
However, it’s imperative that dict remains accessible (and unmodified) while being used, so it must outlive decompression.ZSTD_DCtx_refDDict() :
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: referencing a NULL DDict means “return to no-dictionary mode”.
Note 2 : DDict is just referenced, its lifetime must outlive its usage from DCtx.
ZSTD_DCtx_refPrefix() :
Reference a prefix (single-usage dictionary) to decompress next frame.
This is the reverse operation of ZSTD_CCtx_refPrefix(),
and must use the same prefix as the one used during compression.
Prefix is only used once. Reference is discarded at end of frame.
End of frame is reached when ZSTD_decompressStream() returns 0.
@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 decompression.
Prefix buffer must remain unmodified up to the end of frame,
reached when ZSTD_decompressStream() returns 0.
Note 3 : By default, the prefix is treated as raw content (ZSTD_dm_rawContent).
Use ZSTD_CCtx_refPrefix_advanced() to alter dictMode (Experimental section)
Note 4 : Referencing a raw content prefix has almost no cpu nor memory cost.
A full dictionary is more costly, as it requires building tables.
ZSTD_DCtx_refPrefix_advanced() :
Same as ZSTD_DCtx_refPrefix(), but gives finer control over
how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?)
ZSTD_DCtx_reset() :
Return a DCtx to clean state.
Session and parameters can be reset jointly or separately.
Parameters can only be reset when no active frame is being decompressed.
@return : 0, or an error code, which can be tested with ZSTD_isError()
ZSTD_DCtx_setFormat() :
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()).
ZSTD_DCtx_setMaxWindowSize() :
Refuses allocating internal buffers for frames requiring a window size larger than provided limit.
This protects 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 single-pass mode.
By default, a decompression context accepts all window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT)
@return : 0, or an error code (which can be tested using ZSTD_isError()).
ZSTD_DCtx_setParameter() :
Set one compression parameter, selected by enum ZSTD_dParameter.
All parameters have valid bounds. Bounds can be queried using ZSTD_dParam_getBounds().
Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter).
Setting a parameter is only possible during frame initialization (before starting decompression).
@return : 0, or an error code (which can be tested using ZSTD_isError()).
ZSTD_adjustCParams() :
optimize params for a given
srcSize and dictSize.
both values are optional, select 0 if unknown.ZSTD_cParam_getBounds() :
All parameters must belong to an interval with lower and upper bounds,
otherwise they will either trigger an error or be automatically clamped.
@return : a structure, ZSTD_bounds, which contains
- an error status field, which must be tested using ZSTD_isError()
- lower and upper bounds, both inclusive
ZSTD_checkCParams() :
Ensure param values remain within authorized range
Simple API
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()).ZSTD_compress2() :
Behave the same as ZSTD_compressCCtx(), but compression parameters are set using the advanced API.
ZSTD_compress2() always starts a new frame.
Should cctx hold data from a previously unfinished frame, everything about it is forgotten.
Buffer-less streaming compression (synchronous mode)
ZSTD_compressCCtx() :
Same as ZSTD_compress(), using an explicit ZSTD_CCtx
The function will compress at requested compression level,
ignoring any other parameter
ZSTD_compressStream2() :
Behaves about the same as ZSTD_compressStream, with additional control on end directive.
ZSTD_compressStream2_simpleArgs() :
Same as ZSTD_compressStream2(),
but using only integral types as arguments.
This variant might be helpful for binders from dynamic languages
which have troubles handling structures containing memory pointers.
ZSTD_compress_advanced() :
Same as ZSTD_compress_usingDict(), with fine-tune control over compression parameters (by structure)
ZSTD_compress_usingCDict() :
Compression using a digested Dictionary.
Recommended when same dictionary is used multiple times.
Note : compression level is decided at dictionary creation time,
and frame parameters are hardcoded (dictID=yes, contentSize=yes, checksum=no)
ZSTD_compress_usingCDict_advanced() :
Same as ZSTD_compress_usingCDict(), with fine-tune control over frame parameters
Simple dictionary API
Compression at an explicit compression level using a Dictionary.
A dictionary can be any arbitrary data segment (also called a prefix),
or a buffer with specified information (see dictBuilder/zdict.h).
Note : This function loads the dictionary, resulting in significant startup delay.
It’s intended for a dictionary used only once.
Note 2 : When
dict == NULL || dictSize < 8 no dictionary is used.ZSTD_CCtx_params :
Quick howto :
ZSTD_createCDict() :
When compressing multiple messages / blocks using the same dictionary, it’s recommended to load it only once.
ZSTD_createCDict() will create a digested dictionary, ready to start future compression operations without startup cost.
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, because its content is copied within CDict.
Consider experimental function ZSTD_createCDict_byReference() if you prefer to not duplicate dictBuffer content.
Note : A ZSTD_CDict can be created from an empty dictBuffer, but it is inefficient when used to compress small data.ZSTD_createCDict_byReference() :
Create a digested dictionary for compression
Dictionary content is just referenced, not duplicated.
As a consequence,
dictBuffer must outlive CDict,
and its content must remain unmodified throughout the lifetime of CDict.ZSTD_createDDict() :
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.
ZSTD_createDDict_byReference() :
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
ZSTD_dParam_getBounds() :
All parameters must belong to an interval with lower and upper bounds,
otherwise they will either trigger an error or be automatically clamped.
@return : a structure, ZSTD_bounds, which contains
- an error status field, which must be tested using ZSTD_isError()
- both lower and upper bounds, inclusive
ZSTD_decompress() :
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()).ZSTD_decompressDCtx() :
Same as ZSTD_decompress(),
requires an allocated ZSTD_DCtx.
Compatible with sticky parameters.
ZSTD_decompressStream_simpleArgs() :
Same as ZSTD_decompressStream(),
but using only integral types as arguments.
This can be helpful for binders from dynamic languages
which have troubles handling structures containing memory pointers.
ZSTD_decompress_usingDDict() :
Decompression using a digested Dictionary.
Recommended when same dictionary is used multiple times.
ZSTD_decompress_usingDict() :
Decompression using a known Dictionary.
Dictionary must be identical to the one used during compression.
Note : This function loads the dictionary, resulting in significant startup delay.
It’s intended for a dictionary used only once.
Note : When
dict == NULL || dictSize < 8 no dictionary is used.ZSTD_estimate*() :
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_c_nbWorkers is >= 1.
Note : CCtx size estimation is only correct for single-threaded compression.
ZSTD_estimate?DictSize() :
ZSTD_estimateCDictSize() will bet that src size is relatively “small”, and content is copied, like ZSTD_createCDict().
ZSTD_estimateCDictSize_advanced() makes it possible to control compression parameters precisely, like ZSTD_createCDict_advanced().
Note : dictionaries created by reference (
ZSTD_dlm_byRef) are logically smaller.ZSTD_estimateCStreamSize() :
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_c_nbWorkers is >= 1.
Note : CStream size 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
ZSTD_findDecompressedSize() :
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_ERRORZSTD_findFrameCompressedSize() :
src should point to the start of a ZSTD frame or skippable frame.
srcSize must be >= first frame size
@return : the compressed size of the first frame starting at src,
suitable to pass as srcSize to ZSTD_decompress or similar,
or an error code if input is invalidZSTD_frameHeaderSize() :
srcSize must be >= ZSTD_FRAMEHEADERSIZE_PREFIX.
@return : size of the Frame Header,
or an error code (if srcSize is too small)
ZSTD_freeCDict() :
Function frees memory allocated by ZSTD_createCDict().
ZSTD_freeDDict() :
Function frees memory allocated with ZSTD_createDDict()
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.
ZSTD_getCParams() :
@return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize.
estimatedSrcSize value is optional, select 0 if not knownZSTD_getDecompressedSize() :
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 to the same return value (0),
while ZSTD_getFrameContentSize() gives them separate return values.
@return : decompressed size of
src frame content if known and not empty, 0 otherwise.ZSTD_getDictID_fromDDict() :
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.ZSTD_getDictID_fromDict() :
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.
ZSTD_getDictID_fromFrame() :
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 :ZSTD_getFrameHeader() :
decode Frame Header, or requires larger
srcSize.
@return : 0, zfhPtr is correctly filled,
>0, srcSize is too small, value is wanted srcSize amount,
or an error code, which can be tested using ZSTD_isError()ZSTD_getFrameHeader_advanced() :
same as ZSTD_getFrameHeader(),
with added capability to select a format (like ZSTD_f_zstd1_magicless)
ZSTD_getParams() :
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 : contentSize=1, checksum=0, noDictID=0Advanced streaming functions
Warning : most of these functions are now redundant with the Advanced API.
Once Advanced API reaches “stable” status,
redundant functions will be deprecated, and then at some point removed.
ZSTD_initStatic*() :
Initialize an object using a pre-allocated fixed-size buffer.
workspace: The memory area to emplace the object into.
Provided pointer must be 8-bytes aligned.
Buffer must outlive object.
workspaceSize: Use ZSTD_estimate*Size() to determine
how large workspace must be to support target scenario.
@return : pointer to object (same address as workspace, just different type),
or NULL if error (size too small, incorrect alignment, etc.)
Note : zstd will never resize nor malloc() when using a static buffer.
If the object requires more memory than available,
zstd will just error out (typically ZSTD_error_memory_allocation).
Note 2 : there is no corresponding “free” function.
Since workspace is allocated externally, it must be freed externally too.
Note 3 : cParams : use ZSTD_getCParams() to convert a compression level
into its associated cParams.
Limitation 1 : currently not compatible with internal dictionary creation, triggered by
ZSTD_CCtx_loadDictionary(), ZSTD_initCStream_usingDict() or ZSTD_initDStream_usingDict().
Limitation 2 : static cctx currently not compatible with multi-threading.
Limitation 3 : static dctx is incompatible with legacy support.
ZSTD_isFrame() :
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.ZSTD_resetCStream() :
start a new frame, using same parameters from previous frame.
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().
If pledgedSrcSize is not known at reset time, use macro ZSTD_CONTENTSIZE_UNKNOWN.
If pledgedSrcSize > 0, its value must be correct, as it will be written in header, and controlled at the end.
For the time being, pledgedSrcSize==0 is interpreted as “srcSize unknown” for compatibility with older programs,
but it will change to mean “empty” in future version, so use macro ZSTD_CONTENTSIZE_UNKNOWN instead.
@return : 0, or an error code (which can be tested using ZSTD_isError())
ZSTD_sizeof_*() :
These functions give the current memory usage of selected object.
Note that object memory usage can evolve (increase or decrease) over time.
ZSTD_toFlushNow() :
Tell how many bytes are ready to be flushed immediately.
Useful for multithreading scenarios (nbWorkers >= 1).
Probe the oldest active job, defined as oldest job not yet entirely flushed,
and check its output buffer.
@return : amount of data stored in oldest job and ready to be flushed immediately.
if @return == 0, it means either :
Type Definitions
Explicit context
Bulk processing dictionary API
Custom memory allocation :
These prototypes make it possible to pass your own allocation/free functions.
ZSTD_customMem is provided at creation time, using ZSTD_create*_advanced() variants listed below.
All allocation/free operations will be completed using these custom variants instead of regular <stdlib.h> ones.