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-<title>zstd 1.4.3 Manual</title>
+<title>zstd 1.4.4 Manual</title>
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<body>
-<h1>zstd 1.4.3 Manual</h1>
+<h1>zstd 1.4.4 Manual</h1>
<hr>
<a name="Contents"></a><h2>Contents</h2>
<ol>
* ZSTD_c_forceAttachDict
* ZSTD_c_literalCompressionMode
* ZSTD_c_targetCBlockSize
+ * ZSTD_c_srcSizeHint
* Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them.
* note : never ever use experimentalParam? names directly;
* also, the enums values themselves are unstable and can still change.
ZSTD_c_experimentalParam4=1001,
ZSTD_c_experimentalParam5=1002,
ZSTD_c_experimentalParam6=1003,
+ ZSTD_c_experimentalParam7=1004,
} ZSTD_cParameter;
</b></pre><BR>
<pre><b>typedef struct {
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_CCtxParams_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.
+</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. Unlike ZSTD_estimateCStreamSize*(),
+ this estimate does not include space for a window buffer, so this estimate
+ is guaranteed to be enough for single-shot compressions, but not streaming
+ compressions. It will however assume the input may be arbitrarily large,
+ which is the 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_CCtxParams_setParameter().
+
+ Note: only single-threaded compression is supported. This function will
+ return an error code if ZSTD_c_nbWorkers is >= 1.
</p></pre><BR>
<pre><b>size_t ZSTD_estimateCStreamSize(int compressionLevel);
</b>/**! ZSTD_initCStream_advanced() :<b>
* This function is deprecated, and is approximately equivalent to:
* ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
- * ZSTD_CCtx_setZstdParams(zcs, params); // Set the zstd params and leave the rest as-is
+ * // Pseudocode: Set each zstd parameter and leave the rest as-is.
+ * for ((param, value) : params) {
+ * ZSTD_CCtx_setParameter(zcs, param, value);
+ * }
* ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
* ZSTD_CCtx_loadDictionary(zcs, dict, dictSize);
*
</b>/**! ZSTD_initCStream_usingCDict_advanced() :<b>
* This function is deprecated, and is approximately equivalent to:
* ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
- * ZSTD_CCtx_setZstdFrameParams(zcs, fParams); // Set the zstd frame params and leave the rest as-is
+ * // Pseudocode: Set each zstd frame parameter and leave the rest as-is.
+ * for ((fParam, value) : fParams) {
+ * ZSTD_CCtx_setParameter(zcs, fParam, value);
+ * }
* ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
* ZSTD_CCtx_refCDict(zcs, cdict);
*
.
-.TH "ZSTD" "1" "August 2019" "zstd 1.4.3" "User Commands"
+.TH "ZSTD" "1" "September 2019" "zstd 1.4.4" "User Commands"
.
.SH "NAME"
\fBzstd\fR \- zstd, zstdmt, unzstd, zstdcat \- Compress or decompress \.zst files
\fBzstd\fR will dynamically adapt compression level to perceived I/O conditions\. Compression level adaptation can be observed live by using command \fB\-v\fR\. Adaptation can be constrained between supplied \fBmin\fR and \fBmax\fR levels\. The feature works when combined with multi\-threading and \fB\-\-long\fR mode\. It does not work with \fB\-\-single\-thread\fR\. It sets window size to 8 MB by default (can be changed manually, see \fBwlog\fR)\. Due to the chaotic nature of dynamic adaptation, compressed result is not reproducible\. \fInote\fR : at the time of this writing, \fB\-\-adapt\fR can remain stuck at low speed when combined with multiple worker threads (>=2)\.
.
.TP
+\fB\-\-stream\-size=#\fR
+Sets the pledged source size of input coming from a stream\. This value must be exact, as it will be included in the produced frame header\. Incorrect stream sizes will cause an error\. This information will be used to better optimize compression parameters, resulting in better and potentially faster compression, especially for smaller source sizes\.
+.
+.TP
+\fB\-\-size\-hint=#\fR
+When handling input from a stream, \fBzstd\fR must guess how large the source size will be when optimizing compression parameters\. If the stream size is relatively small, this guess may be a poor one, resulting in a higher compression ratio than expected\. This feature allows for controlling the guess when needed\. Exact guesses result in better compression ratios\. Overestimates result in slightly degraded compression ratios, while underestimates may result in significant degradation\.
+.
+.TP
\fB\-\-rsyncable\fR
\fBzstd\fR will periodically synchronize the compression state to make the compressed file more rsync\-friendly\. There is a negligible impact to compression ratio, and the faster compression levels will see a small compression speed hit\. This feature does not work with \fB\-\-single\-thread\fR\. You probably don\'t want to use it with long range mode, since it will decrease the effectiveness of the synchronization points, but your milage may vary\.
.
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