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gerrit-public.fairphone.software / platform / external / zstd / 7bd1a2900e8e2713cdc9801a9ff81563f39aec9c / . / doc / zstd_manual.html
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Yann Colletfa8dadb2017-05-08 18:24:16 -0700[diff] [blame]4<title>zstd 1.3.0 Manual</title>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]5</head>
6<body>
Yann Colletfa8dadb2017-05-08 18:24:16 -0700[diff] [blame]7<h1>zstd 1.3.0 Manual</h1>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]8<hr>
9<a name="Contents"></a><h2>Contents</h2>
10<ol>
11<li><a href="#Chapter1">Introduction</a></li>
12<li><a href="#Chapter2">Version</a></li>
13<li><a href="#Chapter3">Simple API</a></li>
14<li><a href="#Chapter4">Explicit memory management</a></li>
15<li><a href="#Chapter5">Simple dictionary API</a></li>
Yann Colletc08e6492017-06-19 18:25:35 -0700[diff] [blame]16<li><a href="#Chapter6">Bulk processing dictionary API</a></li>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]17<li><a href="#Chapter7">Streaming</a></li>
18<li><a href="#Chapter8">Streaming compression - HowTo</a></li>
19<li><a href="#Chapter9">Streaming decompression - HowTo</a></li>
20<li><a href="#Chapter10">START OF ADVANCED AND EXPERIMENTAL FUNCTIONS</a></li>
21<li><a href="#Chapter11">Advanced types</a></li>
Yann Collet5a36c062017-05-09 15:11:30 -0700[diff] [blame]22<li><a href="#Chapter12">Frame size functions</a></li>
23<li><a href="#Chapter13">Context memory usage</a></li>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]24<li><a href="#Chapter14">Advanced compression functions</a></li>
25<li><a href="#Chapter15">Advanced decompression functions</a></li>
26<li><a href="#Chapter16">Advanced streaming functions</a></li>
27<li><a href="#Chapter17">Buffer-less and synchronous inner streaming functions</a></li>
28<li><a href="#Chapter18">Buffer-less streaming compression (synchronous mode)</a></li>
29<li><a href="#Chapter19">Buffer-less streaming decompression (synchronous mode)</a></li>
30<li><a href="#Chapter20">Block functions</a></li>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]31</ol>
32<hr>
33<a name="Chapter1"></a><h2>Introduction</h2><pre>
Yann Colleta5ffe3d2017-05-12 16:29:19 -0700[diff] [blame]34 zstd, short for Zstandard, is a fast lossless compression algorithm,
35 targeting real-time compression scenarios at zlib-level and better compression ratios.
36 The zstd compression library provides in-memory compression and decompression functions.
37 The library supports compression levels from 1 up to ZSTD_maxCLevel() which is currently 22.
Yann Collet831b4892017-02-23 23:09:10 -0800[diff] [blame]38 Levels >= 20, labeled `--ultra`, should be used with caution, as they require more memory.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]39 Compression can be done in:
40 - a single step (described as Simple API)
41 - a single step, reusing a context (described as Explicit memory management)
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]42 - unbounded multiple steps (described as Streaming compression)
Yann Colletc08e6492017-06-19 18:25:35 -0700[diff] [blame]43 The compression ratio achievable on small data can be highly improved using a dictionary in:
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]44 - a single step (described as Simple dictionary API)
45 - a single step, reusing a dictionary (described as Fast dictionary API)
46
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]47 Advanced experimental functions can be accessed using #define ZSTD_STATIC_LINKING_ONLY before including zstd.h.
Yann Colletc08e6492017-06-19 18:25:35 -0700[diff] [blame]48 Advanced experimental APIs shall never be used with a dynamic library.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]49 They are not "stable", their definition may change in the future. Only static linking is allowed.
50<BR></pre>
51
52<a name="Chapter2"></a><h2>Version</h2><pre></pre>
53
Yann Colletc08e6492017-06-19 18:25:35 -0700[diff] [blame]54<pre><b>unsigned ZSTD_versionNumber(void); </b>/**< useful to check dll version */<b>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]55</b></pre><BR>
56<a name="Chapter3"></a><h2>Simple API</h2><pre></pre>
57
58<pre><b>size_t ZSTD_compress( void* dst, size_t dstCapacity,
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]59 const void* src, size_t srcSize,
60 int compressionLevel);
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]61</b><p> Compresses `src` content as a single zstd compressed frame into already allocated `dst`.
62 Hint : compression runs faster if `dstCapacity` >= `ZSTD_compressBound(srcSize)`.
63 @return : compressed size written into `dst` (<= `dstCapacity),
64 or an error code if it fails (which can be tested using ZSTD_isError()).
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]65</p></pre><BR>
66
67<pre><b>size_t ZSTD_decompress( void* dst, size_t dstCapacity,
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]68 const void* src, size_t compressedSize);
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]69</b><p> `compressedSize` : must be the _exact_ size of some number of compressed and/or skippable frames.
Yann Colletc08e6492017-06-19 18:25:35 -0700[diff] [blame]70 `dstCapacity` is an upper bound of originalSize to regenerate.
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]71 If user cannot imply a maximum upper bound, it's better to use streaming mode to decompress data.
72 @return : the number of bytes decompressed into `dst` (<= `dstCapacity`),
73 or an errorCode if it fails (which can be tested using ZSTD_isError()).
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]74</p></pre><BR>
75
76<pre><b>unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize);
Yann Colleta5ffe3d2017-05-12 16:29:19 -0700[diff] [blame]77</b><p> NOTE: This function is planned to be obsolete, in favor of ZSTD_getFrameContentSize().
78 ZSTD_getFrameContentSize() works the same way,
79 returning the decompressed size of a single frame,
80 but distinguishes empty frames from frames with an unknown size, or errors.
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]81
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]82 'src' is the start of a zstd compressed frame.
83 @return : content size to be decompressed, as a 64-bits value _if known_, 0 otherwise.
Yann Colleta5ffe3d2017-05-12 16:29:19 -0700[diff] [blame]84 note 1 : decompressed size is an optional field, it may not be present, typically in streaming mode.
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]85 When `return==0`, data to decompress could be any size.
86 In which case, it's necessary to use streaming mode to decompress data.
Yann Colleta5ffe3d2017-05-12 16:29:19 -0700[diff] [blame]87 Optionally, application can use ZSTD_decompress() while relying on implied limits.
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]88 (For example, data may be necessarily cut into blocks <= 16 KB).
89 note 2 : decompressed size is always present when compression is done with ZSTD_compress()
90 note 3 : decompressed size can be very large (64-bits value),
91 potentially larger than what local system can handle as a single memory segment.
92 In which case, it's necessary to use streaming mode to decompress data.
93 note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified.
94 Always ensure result fits within application's authorized limits.
95 Each application can set its own limits.
Yann Collet7028cbd2017-05-25 18:29:08 -0700[diff] [blame]96 note 5 : when `return==0`, if precise failure cause is needed, use ZSTD_getFrameHeader() to know more.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]97</p></pre><BR>
98
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]99<h3>Helper functions</h3><pre></pre><b><pre>int ZSTD_maxCLevel(void); </b>/*!< maximum compression level available */<b>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]100size_t ZSTD_compressBound(size_t srcSize); </b>/*!< maximum compressed size in worst case scenario */<b>
101unsigned ZSTD_isError(size_t code); </b>/*!< tells if a `size_t` function result is an error code */<b>
102const char* ZSTD_getErrorName(size_t code); </b>/*!< provides readable string from an error code */<b>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]103</pre></b><BR>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]104<a name="Chapter4"></a><h2>Explicit memory management</h2><pre></pre>
105
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]106<h3>Compression context</h3><pre> When compressing many times,
107 it is recommended to allocate a context just once, and re-use it for each successive compression operation.
108 This will make workload friendlier for system's memory.
109 Use one context per thread for parallel execution in multi-threaded environments.
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]110</pre><b><pre>typedef struct ZSTD_CCtx_s ZSTD_CCtx;
111ZSTD_CCtx* ZSTD_createCCtx(void);
112size_t ZSTD_freeCCtx(ZSTD_CCtx* cctx);
113</pre></b><BR>
Yann Colleta5ffe3d2017-05-12 16:29:19 -0700[diff] [blame]114<pre><b>size_t ZSTD_compressCCtx(ZSTD_CCtx* ctx,
115 void* dst, size_t dstCapacity,
116 const void* src, size_t srcSize,
117 int compressionLevel);
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]118</b><p> Same as ZSTD_compress(), requires an allocated ZSTD_CCtx (see ZSTD_createCCtx()).
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]119</p></pre><BR>
120
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]121<h3>Decompression context</h3><pre> When decompressing many times,
Yann Colleta5ffe3d2017-05-12 16:29:19 -0700[diff] [blame]122 it is recommended to allocate a context only once,
123 and re-use it for each successive compression operation.
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]124 This will make workload friendlier for system's memory.
Yann Colleta5ffe3d2017-05-12 16:29:19 -0700[diff] [blame]125 Use one context per thread for parallel execution.
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]126</pre><b><pre>typedef struct ZSTD_DCtx_s ZSTD_DCtx;
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]127ZSTD_DCtx* ZSTD_createDCtx(void);
128size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx);
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]129</pre></b><BR>
Yann Colleta5ffe3d2017-05-12 16:29:19 -0700[diff] [blame]130<pre><b>size_t ZSTD_decompressDCtx(ZSTD_DCtx* ctx,
131 void* dst, size_t dstCapacity,
132 const void* src, size_t srcSize);
133</b><p> Same as ZSTD_decompress(), requires an allocated ZSTD_DCtx (see ZSTD_createDCtx())
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]134</p></pre><BR>
135
136<a name="Chapter5"></a><h2>Simple dictionary API</h2><pre></pre>
137
138<pre><b>size_t ZSTD_compress_usingDict(ZSTD_CCtx* ctx,
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]139 void* dst, size_t dstCapacity,
140 const void* src, size_t srcSize,
141 const void* dict,size_t dictSize,
142 int compressionLevel);
Yann Colletc08e6492017-06-19 18:25:35 -0700[diff] [blame]143</b><p> Compression using a predefined Dictionary (see dictBuilder/zdict.h).
144 Note : This function loads the dictionary, resulting in significant startup delay.
145 Note : When `dict == NULL || dictSize < 8` no dictionary is used.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]146</p></pre><BR>
147
148<pre><b>size_t ZSTD_decompress_usingDict(ZSTD_DCtx* dctx,
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]149 void* dst, size_t dstCapacity,
150 const void* src, size_t srcSize,
151 const void* dict,size_t dictSize);
Yann Colletc08e6492017-06-19 18:25:35 -0700[diff] [blame]152</b><p> Decompression using a predefined Dictionary (see dictBuilder/zdict.h).
153 Dictionary must be identical to the one used during compression.
154 Note : This function loads the dictionary, resulting in significant startup delay.
155 Note : When `dict == NULL || dictSize < 8` no dictionary is used.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]156</p></pre><BR>
157
Yann Colletc08e6492017-06-19 18:25:35 -0700[diff] [blame]158<a name="Chapter6"></a><h2>Bulk processing dictionary API</h2><pre></pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]159
Yann Colleta5ffe3d2017-05-12 16:29:19 -0700[diff] [blame]160<pre><b>ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize,
161 int compressionLevel);
Yann Colletc08e6492017-06-19 18:25:35 -0700[diff] [blame]162</b><p> When compressing multiple messages / blocks with the same dictionary, it's recommended to load it just once.
163 ZSTD_createCDict() will create a digested dictionary, ready to start future compression operations without startup delay.
164 ZSTD_CDict can be created once and shared by multiple threads concurrently, since its usage is read-only.
165 `dictBuffer` can be released after ZSTD_CDict creation, since its content is copied within CDict
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]166</p></pre><BR>
167
168<pre><b>size_t ZSTD_freeCDict(ZSTD_CDict* CDict);
Yann Colletc08e6492017-06-19 18:25:35 -0700[diff] [blame]169</b><p> Function frees memory allocated by ZSTD_createCDict().
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]170</p></pre><BR>
171
172<pre><b>size_t ZSTD_compress_usingCDict(ZSTD_CCtx* cctx,
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]173 void* dst, size_t dstCapacity,
174 const void* src, size_t srcSize,
175 const ZSTD_CDict* cdict);
Yann Collet715b9aa2017-04-18 13:55:53 -0700[diff] [blame]176</b><p> Compression using a digested Dictionary.
177 Faster startup than ZSTD_compress_usingDict(), recommended when same dictionary is used multiple times.
178 Note that compression level is decided during dictionary creation.
179 Frame parameters are hardcoded (dictID=yes, contentSize=yes, checksum=no)
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]180</p></pre><BR>
181
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]182<pre><b>ZSTD_DDict* ZSTD_createDDict(const void* dictBuffer, size_t dictSize);
Yann Colletc08e6492017-06-19 18:25:35 -0700[diff] [blame]183</b><p> Create a digested dictionary, ready to start decompression operation without startup delay.
184 dictBuffer can be released after DDict creation, as its content is copied inside DDict
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]185</p></pre><BR>
186
187<pre><b>size_t ZSTD_freeDDict(ZSTD_DDict* ddict);
Yann Colletc08e6492017-06-19 18:25:35 -0700[diff] [blame]188</b><p> Function frees memory allocated with ZSTD_createDDict()
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]189</p></pre><BR>
190
191<pre><b>size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx,
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]192 void* dst, size_t dstCapacity,
193 const void* src, size_t srcSize,
194 const ZSTD_DDict* ddict);
Yann Colletc08e6492017-06-19 18:25:35 -0700[diff] [blame]195</b><p> Decompression using a digested Dictionary.
196 Faster startup than ZSTD_decompress_usingDict(), recommended when same dictionary is used multiple times.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]197</p></pre><BR>
198
199<a name="Chapter7"></a><h2>Streaming</h2><pre></pre>
200
201<pre><b>typedef struct ZSTD_inBuffer_s {
202 const void* src; </b>/**< start of input buffer */<b>
203 size_t size; </b>/**< size of input buffer */<b>
204 size_t pos; </b>/**< position where reading stopped. Will be updated. Necessarily 0 <= pos <= size */<b>
205} ZSTD_inBuffer;
206</b></pre><BR>
207<pre><b>typedef struct ZSTD_outBuffer_s {
208 void* dst; </b>/**< start of output buffer */<b>
209 size_t size; </b>/**< size of output buffer */<b>
210 size_t pos; </b>/**< position where writing stopped. Will be updated. Necessarily 0 <= pos <= size */<b>
211} ZSTD_outBuffer;
212</b></pre><BR>
213<a name="Chapter8"></a><h2>Streaming compression - HowTo</h2><pre>
214 A ZSTD_CStream object is required to track streaming operation.
215 Use ZSTD_createCStream() and ZSTD_freeCStream() to create/release resources.
216 ZSTD_CStream objects can be reused multiple times on consecutive compression operations.
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]217 It is recommended to re-use ZSTD_CStream in situations where many streaming operations will be achieved consecutively,
218 since it will play nicer with system's memory, by re-using already allocated memory.
219 Use one separate ZSTD_CStream per thread for parallel execution.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]220
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]221 Start a new compression by initializing ZSTD_CStream.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]222 Use ZSTD_initCStream() to start a new compression operation.
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]223 Use ZSTD_initCStream_usingDict() or ZSTD_initCStream_usingCDict() for a compression which requires a dictionary (experimental section)
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]224
225 Use ZSTD_compressStream() repetitively to consume input stream.
226 The function will automatically update both `pos` fields.
227 Note that it may not consume the entire input, in which case `pos < size`,
228 and it's up to the caller to present again remaining data.
229 @return : a size hint, preferred nb of bytes to use as input for next function call
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]230 or an error code, which can be tested using ZSTD_isError().
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]231 Note 1 : it's just a hint, to help latency a little, any other value will work fine.
232 Note 2 : size hint is guaranteed to be <= ZSTD_CStreamInSize()
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]233
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]234 At any moment, it's possible to flush whatever data remains within internal buffer, using ZSTD_flushStream().
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]235 `output->pos` will be updated.
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]236 Note that some content might still be left within internal buffer if `output->size` is too small.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]237 @return : nb of bytes still present within internal buffer (0 if it's empty)
238 or an error code, which can be tested using ZSTD_isError().
239
240 ZSTD_endStream() instructs to finish a frame.
241 It will perform a flush and write frame epilogue.
242 The epilogue is required for decoders to consider a frame completed.
Yann Colletfa3671e2017-05-19 10:51:30 -0700[diff] [blame]243 ZSTD_endStream() may not be able to flush full data if `output->size` is too small.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]244 In which case, call again ZSTD_endStream() to complete the flush.
Yann Colletfa3671e2017-05-19 10:51:30 -0700[diff] [blame]245 @return : 0 if frame fully completed and fully flushed,
246 or >0 if some data is still present within internal buffer
247 (value is minimum size estimation for remaining data to flush, but it could be more)
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]248 or an error code, which can be tested using ZSTD_isError().
249
250
251<BR></pre>
252
Yann Colletc08e6492017-06-19 18:25:35 -0700[diff] [blame]253<pre><b>typedef ZSTD_CCtx ZSTD_CStream; </b>/**< CCtx and CStream are now effectively same object (>= v1.3.0) */<b>
Yann Collet0be6fd32017-05-08 16:08:01 -0700[diff] [blame]254</b></pre><BR>
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]255<h3>ZSTD_CStream management functions</h3><pre></pre><b><pre>ZSTD_CStream* ZSTD_createCStream(void);
256size_t ZSTD_freeCStream(ZSTD_CStream* zcs);
257</pre></b><BR>
258<h3>Streaming compression functions</h3><pre></pre><b><pre>size_t ZSTD_initCStream(ZSTD_CStream* zcs, int compressionLevel);
259size_t ZSTD_compressStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
260size_t ZSTD_flushStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
261size_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
262</pre></b><BR>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]263<pre><b>size_t ZSTD_CStreamInSize(void); </b>/**< recommended size for input buffer */<b>
264</b></pre><BR>
265<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>
266</b></pre><BR>
267<a name="Chapter9"></a><h2>Streaming decompression - HowTo</h2><pre>
268 A ZSTD_DStream object is required to track streaming operations.
269 Use ZSTD_createDStream() and ZSTD_freeDStream() to create/release resources.
270 ZSTD_DStream objects can be re-used multiple times.
271
272 Use ZSTD_initDStream() to start a new decompression operation,
273 or ZSTD_initDStream_usingDict() if decompression requires a dictionary.
274 @return : recommended first input size
275
276 Use ZSTD_decompressStream() repetitively to consume your input.
277 The function will update both `pos` fields.
278 If `input.pos < input.size`, some input has not been consumed.
279 It's up to the caller to present again remaining data.
280 If `output.pos < output.size`, decoder has flushed everything it could.
281 @return : 0 when a frame is completely decoded and fully flushed,
282 an error code, which can be tested using ZSTD_isError(),
Przemyslaw Skibinski4da53212016-12-07 11:18:40 +0100[diff] [blame]283 any other value > 0, which means there is still some decoding to do to complete current frame.
284 The return value is a suggested next input size (a hint to improve latency) that will never load more than the current frame.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]285
286<BR></pre>
287
Yann Colletc08e6492017-06-19 18:25:35 -0700[diff] [blame]288<pre><b>typedef ZSTD_DCtx ZSTD_DStream; </b>/**< DCtx and DStream are now effectively same object (>= v1.3.0) */<b>
289</b></pre><BR>
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]290<h3>ZSTD_DStream management functions</h3><pre></pre><b><pre>ZSTD_DStream* ZSTD_createDStream(void);
291size_t ZSTD_freeDStream(ZSTD_DStream* zds);
292</pre></b><BR>
293<h3>Streaming decompression functions</h3><pre></pre><b><pre>size_t ZSTD_initDStream(ZSTD_DStream* zds);
294size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
295</pre></b><BR>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]296<pre><b>size_t ZSTD_DStreamInSize(void); </b>/*!< recommended size for input buffer */<b>
297</b></pre><BR>
298<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>
299</b></pre><BR>
300<a name="Chapter10"></a><h2>START OF ADVANCED AND EXPERIMENTAL FUNCTIONS</h2><pre> The definitions in this section are considered experimental.
301 They should never be used with a dynamic library, as they may change in the future.
302 They are provided for advanced usages.
303 Use them only in association with static linking.
304
305<BR></pre>
306
307<a name="Chapter11"></a><h2>Advanced types</h2><pre></pre>
308
Yann Colleta5ffe3d2017-05-12 16:29:19 -0700[diff] [blame]309<pre><b>typedef enum { ZSTD_fast=1, ZSTD_dfast, ZSTD_greedy, ZSTD_lazy, ZSTD_lazy2,
310 ZSTD_btlazy2, ZSTD_btopt, ZSTD_btultra } ZSTD_strategy; </b>/* from faster to stronger */<b>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]311</b></pre><BR>
312<pre><b>typedef struct {
313 unsigned windowLog; </b>/**< largest match distance : larger == more compression, more memory needed during decompression */<b>
314 unsigned chainLog; </b>/**< fully searched segment : larger == more compression, slower, more memory (useless for fast) */<b>
315 unsigned hashLog; </b>/**< dispatch table : larger == faster, more memory */<b>
316 unsigned searchLog; </b>/**< nb of searches : larger == more compression, slower */<b>
317 unsigned searchLength; </b>/**< match length searched : larger == faster decompression, sometimes less compression */<b>
318 unsigned targetLength; </b>/**< acceptable match size for optimal parser (only) : larger == more compression, slower */<b>
319 ZSTD_strategy strategy;
320} ZSTD_compressionParameters;
321</b></pre><BR>
322<pre><b>typedef struct {
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]323 unsigned contentSizeFlag; </b>/**< 1: content size will be in frame header (when known) */<b>
324 unsigned checksumFlag; </b>/**< 1: generate a 32-bits checksum at end of frame, for error detection */<b>
325 unsigned noDictIDFlag; </b>/**< 1: no dictID will be saved into frame header (if dictionary compression) */<b>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]326} ZSTD_frameParameters;
327</b></pre><BR>
328<pre><b>typedef struct {
329 ZSTD_compressionParameters cParams;
330 ZSTD_frameParameters fParams;
331} ZSTD_parameters;
332</b></pre><BR>
Yann Colletf16f4492017-05-09 16:18:17 -0700[diff] [blame]333<pre><b>typedef struct {
334 unsigned long long frameContentSize;
335 unsigned windowSize;
336 unsigned dictID;
337 unsigned checksumFlag;
338} ZSTD_frameHeader;
339</b></pre><BR>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]340<h3>Custom memory allocation functions</h3><pre></pre><b><pre>typedef void* (*ZSTD_allocFunction) (void* opaque, size_t size);
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]341typedef void (*ZSTD_freeFunction) (void* opaque, void* address);
342typedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; void* opaque; } ZSTD_customMem;
Yann Collet44e45e82017-05-30 16:12:06 -0700[diff] [blame]343</b>/* use this constant to defer to stdlib's functions */<b>
Yann Collet7bd1a292017-06-21 11:50:33 -0700[diff] [blame^]344static const ZSTD_customMem ZSTD_defaultCMem = { NULL, NULL, NULL };
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]345</pre></b><BR>
Yann Collet5a36c062017-05-09 15:11:30 -0700[diff] [blame]346<a name="Chapter12"></a><h2>Frame size functions</h2><pre></pre>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]347
Yann Collet831b4892017-02-23 23:09:10 -0800[diff] [blame]348<pre><b>size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize);
349</b><p> `src` should point to the start of a ZSTD encoded frame or skippable frame
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]350 `srcSize` must be at least as large as the frame
Yann Collet5a36c062017-05-09 15:11:30 -0700[diff] [blame]351 @return : the compressed size of the frame pointed to by `src`,
352 suitable to pass to `ZSTD_decompress` or similar,
353 or an error code if given invalid input.
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]354</p></pre><BR>
355
Yann Collet5a36c062017-05-09 15:11:30 -0700[diff] [blame]356<pre><b>#define ZSTD_CONTENTSIZE_UNKNOWN (0ULL - 1)
357#define ZSTD_CONTENTSIZE_ERROR (0ULL - 2)
358unsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize);
359</b><p> `src` should point to the start of a ZSTD encoded frame.
360 `srcSize` must be at least as large as the frame header.
361 A value >= `ZSTD_frameHeaderSize_max` is guaranteed to be large enough.
362 @return : - decompressed size of the frame pointed to be `src` if known
363 - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined
364 - ZSTD_CONTENTSIZE_ERROR if an error occurred (e.g. invalid magic number, srcSize too small)
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]365</p></pre><BR>
366
367<pre><b>unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize);
Yann Collet5a36c062017-05-09 15:11:30 -0700[diff] [blame]368</b><p> `src` should point the start of a series of ZSTD encoded and/or skippable frames
369 `srcSize` must be the _exact_ size of this series
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]370 (i.e. there should be a frame boundary exactly `srcSize` bytes after `src`)
Yann Collet5a36c062017-05-09 15:11:30 -0700[diff] [blame]371 @return : - decompressed size of all data in all successive frames
372 - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN
373 - if an error occurred: ZSTD_CONTENTSIZE_ERROR
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]374
Yann Collet5a36c062017-05-09 15:11:30 -0700[diff] [blame]375 note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode.
376 When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
377 In which case, it's necessary to use streaming mode to decompress data.
378 Optionally, application can still use ZSTD_decompress() while relying on implied limits.
379 (For example, data may be necessarily cut into blocks <= 16 KB).
380 note 2 : decompressed size is always present when compression is done with ZSTD_compress()
381 note 3 : decompressed size can be very large (64-bits value),
382 potentially larger than what local system can handle as a single memory segment.
383 In which case, it's necessary to use streaming mode to decompress data.
384 note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified.
385 Always ensure result fits within application's authorized limits.
386 Each application can set its own limits.
387 note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to
388 read each contained frame header. This is efficient as most of the data is skipped,
389 however it does mean that all frame data must be present and valid.
390</p></pre><BR>
391
392<a name="Chapter13"></a><h2>Context memory usage</h2><pre></pre>
393
394<pre><b>size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx);
395size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx);
396size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs);
397size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds);
398size_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict);
399size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict);
400</b><p> These functions give the current memory usage of selected object.
401 Object memory usage can evolve if it's re-used multiple times.
402</p></pre><BR>
403
404<pre><b>size_t ZSTD_estimateCCtxSize(ZSTD_compressionParameters cParams);
405size_t ZSTD_estimateDCtxSize(void);
406</b><p> These functions make it possible to estimate memory usage
407 of a future target object, before its allocation,
408 given a set of parameters, which vary depending on target object.
Yann Collet58e8d792017-06-02 18:20:48 -0700[diff] [blame]409 The objective is to guide decision before allocation.
410 Note : CCtx estimation is only correct for single-threaded compression
Yann Collet5a36c062017-05-09 15:11:30 -0700[diff] [blame]411</p></pre><BR>
412
413<pre><b>size_t ZSTD_estimateCStreamSize(ZSTD_compressionParameters cParams);
Yann Colletf16f4492017-05-09 16:18:17 -0700[diff] [blame]414size_t ZSTD_estimateDStreamSize(ZSTD_frameHeader fHeader);
Yann Collet5a36c062017-05-09 15:11:30 -0700[diff] [blame]415</b><p> Note : if streaming is init with function ZSTD_init?Stream_usingDict(),
Yann Colletcdf7e822017-05-25 18:05:49 -0700[diff] [blame]416 an internal ?Dict will be created, which size is not estimated here.
417 In this case, get total size by adding ZSTD_estimate?DictSize
Yann Collet5a36c062017-05-09 15:11:30 -0700[diff] [blame]418</p></pre><BR>
419
Yann Collet25989e32017-05-25 15:07:37 -0700[diff] [blame]420<pre><b>size_t ZSTD_estimateCDictSize(ZSTD_compressionParameters cParams, size_t dictSize, unsigned byReference);
421size_t ZSTD_estimateDDictSize(size_t dictSize, unsigned byReference);
422</b><p> Note : dictionary created "byReference" are smaller
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]423</p></pre><BR>
424
425<a name="Chapter14"></a><h2>Advanced compression functions</h2><pre></pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]426
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]427<pre><b>ZSTD_CCtx* ZSTD_createCCtx_advanced(ZSTD_customMem customMem);
428</b><p> Create a ZSTD compression context using external alloc and free functions
429</p></pre><BR>
430
Yann Colletc7fe2622017-05-23 13:16:00 -0700[diff] [blame]431<pre><b>ZSTD_CCtx* ZSTD_initStaticCCtx(void* workspace, size_t workspaceSize);
432</b><p> workspace: The memory area to emplace the context into.
433 Provided pointer must 8-bytes aligned.
434 It must outlive context usage.
435 workspaceSize: Use ZSTD_estimateCCtxSize() or ZSTD_estimateCStreamSize()
436 to determine how large workspace must be to support scenario.
437 @return : pointer to ZSTD_CCtx*, or NULL if error (size too small)
438 Note : zstd will never resize nor malloc() when using a static cctx.
439 If it needs more memory than available, it will simply error out.
440 Note 2 : there is no corresponding "free" function.
441 Since workspace was allocated externally, it must be freed externally too.
Yann Colletc7dcf0f2017-06-19 12:03:25 -0700[diff] [blame]442 Limitation 1 : currently not compatible with internal CDict creation, such as
443 ZSTD_CCtx_loadDictionary() or ZSTD_initCStream_usingDict().
444 Limitation 2 : currently not compatible with multi-threading
Yann Colletc7fe2622017-05-23 13:16:00 -0700[diff] [blame]445
446</p></pre><BR>
447
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]448<pre><b>typedef enum {
Yann Collet14312d82017-02-23 23:42:12 -0800[diff] [blame]449 ZSTD_p_forceWindow, </b>/* Force back-references to remain < windowSize, even when referencing Dictionary content (default:0) */<b>
450 ZSTD_p_forceRawDict </b>/* Force loading dictionary in "content-only" mode (no header analysis) */<b>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]451} ZSTD_CCtxParameter;
452</b></pre><BR>
453<pre><b>size_t ZSTD_setCCtxParameter(ZSTD_CCtx* cctx, ZSTD_CCtxParameter param, unsigned value);
454</b><p> Set advanced parameters, selected through enum ZSTD_CCtxParameter
455 @result : 0, or an error code (which can be tested with ZSTD_isError())
456</p></pre><BR>
457
458<pre><b>ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel);
459</b><p> Create a digested dictionary for compression
460 Dictionary content is simply referenced, and therefore stays in dictBuffer.
461 It is important that dictBuffer outlives CDict, it must remain read accessible throughout the lifetime of CDict
462</p></pre><BR>
463
Yann Collet7bd1a292017-06-21 11:50:33 -0700[diff] [blame^]464<pre><b>typedef enum { ZSTD_dm_auto=0, ZSTD_dm_rawContent, ZSTD_dm_fullDict } ZSTD_dictMode_e;
465</b></pre><BR>
466<pre><b>ZSTD_CDict* ZSTD_createCDict_advanced(const void* dict, size_t dictSize,
467 unsigned byReference, ZSTD_dictMode_e dictMode,
Yann Collet31533ba2017-04-27 00:29:04 -0700[diff] [blame]468 ZSTD_compressionParameters cParams, ZSTD_customMem customMem);
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]469</b><p> Create a ZSTD_CDict using external alloc and free, and customized compression parameters
470</p></pre><BR>
471
Yann Colletcdf7e822017-05-25 18:05:49 -0700[diff] [blame]472<pre><b>ZSTD_CDict* ZSTD_initStaticCDict(
473 void* workspace, size_t workspaceSize,
Yann Collet7bd1a292017-06-21 11:50:33 -0700[diff] [blame^]474 const void* dict, size_t dictSize,
475 unsigned byReference, ZSTD_dictMode_e dictMode,
Yann Colletcdf7e822017-05-25 18:05:49 -0700[diff] [blame]476 ZSTD_compressionParameters cParams);
477</b><p> Generate a digested dictionary in provided memory area.
478 workspace: The memory area to emplace the dictionary into.
479 Provided pointer must 8-bytes aligned.
480 It must outlive dictionary usage.
481 workspaceSize: Use ZSTD_estimateCDictSize()
482 to determine how large workspace must be.
483 cParams : use ZSTD_getCParams() to transform a compression level
484 into its relevants cParams.
485 @return : pointer to ZSTD_CDict*, or NULL if error (size too small)
486 Note : there is no corresponding "free" function.
487 Since workspace was allocated externally, it must be freed externally.
488
489</p></pre><BR>
490
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]491<pre><b>ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
492</b><p> @return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize.
493 `estimatedSrcSize` value is optional, select 0 if not known
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]494</p></pre><BR>
495
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]496<pre><b>ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
497</b><p> same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of sub-component `ZSTD_compressionParameters`.
498 All fields of `ZSTD_frameParameters` are set to default (0)
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]499</p></pre><BR>
500
501<pre><b>size_t ZSTD_checkCParams(ZSTD_compressionParameters params);
502</b><p> Ensure param values remain within authorized range
503</p></pre><BR>
504
505<pre><b>ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize);
Yann Colletc7dcf0f2017-06-19 12:03:25 -0700[diff] [blame]506</b><p> optimize params for a given `srcSize` and `dictSize`.
507 both values are optional, select `0` if unknown.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]508</p></pre><BR>
509
Yann Colletf4bd8572017-04-27 11:31:55 -0700[diff] [blame]510<pre><b>size_t ZSTD_compress_advanced (ZSTD_CCtx* cctx,
511 void* dst, size_t dstCapacity,
512 const void* src, size_t srcSize,
513 const void* dict,size_t dictSize,
514 ZSTD_parameters params);
515</b><p> Same as ZSTD_compress_usingDict(), with fine-tune control over each compression parameter
516</p></pre><BR>
517
518<pre><b>size_t ZSTD_compress_usingCDict_advanced(ZSTD_CCtx* cctx,
519 void* dst, size_t dstCapacity,
520 const void* src, size_t srcSize,
521 const ZSTD_CDict* cdict, ZSTD_frameParameters fParams);
Yann Collet77bf59e2017-04-27 11:43:04 -0700[diff] [blame]522</b><p> Same as ZSTD_compress_usingCDict(), with fine-tune control over frame parameters
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]523</p></pre><BR>
524
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]525<a name="Chapter15"></a><h2>Advanced decompression functions</h2><pre></pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]526
Przemyslaw Skibinski4da53212016-12-07 11:18:40 +0100[diff] [blame]527<pre><b>unsigned ZSTD_isFrame(const void* buffer, size_t size);
528</b><p> Tells if the content of `buffer` starts with a valid Frame Identifier.
529 Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0.
530 Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled.
531 Note 3 : Skippable Frame Identifiers are considered valid.
532</p></pre><BR>
533
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]534<pre><b>ZSTD_DCtx* ZSTD_createDCtx_advanced(ZSTD_customMem customMem);
535</b><p> Create a ZSTD decompression context using external alloc and free functions
536</p></pre><BR>
537
Yann Collet0fdc71c2017-05-24 17:41:41 -0700[diff] [blame]538<pre><b>ZSTD_DCtx* ZSTD_initStaticDCtx(void* workspace, size_t workspaceSize);
539</b><p> workspace: The memory area to emplace the context into.
540 Provided pointer must 8-bytes aligned.
541 It must outlive context usage.
542 workspaceSize: Use ZSTD_estimateDCtxSize() or ZSTD_estimateDStreamSize()
543 to determine how large workspace must be to support scenario.
544 @return : pointer to ZSTD_DCtx*, or NULL if error (size too small)
545 Note : zstd will never resize nor malloc() when using a static dctx.
546 If it needs more memory than available, it will simply error out.
Yann Colletb8136f02017-05-27 00:03:08 -0700[diff] [blame]547 Note 2 : static dctx is incompatible with legacy support
548 Note 3 : there is no corresponding "free" function.
Yann Collet0fdc71c2017-05-24 17:41:41 -0700[diff] [blame]549 Since workspace was allocated externally, it must be freed externally.
550 Limitation : currently not compatible with internal DDict creation,
551 such as ZSTD_initDStream_usingDict().
552
553</p></pre><BR>
554
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]555<pre><b>ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize);
556</b><p> Create a digested dictionary, ready to start decompression operation without startup delay.
Yann Collet57827f92017-05-25 15:44:06 -0700[diff] [blame]557 Dictionary content is referenced, and therefore stays in dictBuffer.
558 It is important that dictBuffer outlives DDict,
559 it must remain read accessible throughout the lifetime of DDict
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]560</p></pre><BR>
561
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]562<pre><b>ZSTD_DDict* ZSTD_createDDict_advanced(const void* dict, size_t dictSize,
563 unsigned byReference, ZSTD_customMem customMem);
564</b><p> Create a ZSTD_DDict using external alloc and free, optionally by reference
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]565</p></pre><BR>
566
Yann Collet25989e32017-05-25 15:07:37 -0700[diff] [blame]567<pre><b>ZSTD_DDict* ZSTD_initStaticDDict(void* workspace, size_t workspaceSize,
568 const void* dict, size_t dictSize,
569 unsigned byReference);
570</b><p> Generate a digested dictionary in provided memory area.
571 workspace: The memory area to emplace the dictionary into.
572 Provided pointer must 8-bytes aligned.
573 It must outlive dictionary usage.
574 workspaceSize: Use ZSTD_estimateDDictSize()
575 to determine how large workspace must be.
576 @return : pointer to ZSTD_DDict*, or NULL if error (size too small)
577 Note : there is no corresponding "free" function.
578 Since workspace was allocated externally, it must be freed externally.
579
580</p></pre><BR>
581
Przemyslaw Skibinski4da53212016-12-07 11:18:40 +0100[diff] [blame]582<pre><b>unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize);
583</b><p> Provides the dictID stored within dictionary.
584 if @return == 0, the dictionary is not conformant with Zstandard specification.
585 It can still be loaded, but as a content-only dictionary.
586</p></pre><BR>
587
588<pre><b>unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict);
589</b><p> Provides the dictID of the dictionary loaded into `ddict`.
590 If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
591 Non-conformant dictionaries can still be loaded, but as content-only dictionaries.
592</p></pre><BR>
593
594<pre><b>unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize);
595</b><p> Provides the dictID required to decompressed the frame stored within `src`.
596 If @return == 0, the dictID could not be decoded.
597 This could for one of the following reasons :
598 - The frame does not require a dictionary to be decoded (most common case).
599 - The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden information.
600 Note : this use case also happens when using a non-conformant dictionary.
601 - `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`).
602 - This is not a Zstandard frame.
Yann Collet7028cbd2017-05-25 18:29:08 -0700[diff] [blame]603 When identifying the exact failure cause, it's possible to use ZSTD_getFrameHeader(), which will provide a more precise error code.
Przemyslaw Skibinski4da53212016-12-07 11:18:40 +0100[diff] [blame]604</p></pre><BR>
605
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]606<a name="Chapter16"></a><h2>Advanced streaming functions</h2><pre></pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]607
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]608<h3>Advanced Streaming compression functions</h3><pre></pre><b><pre>ZSTD_CStream* ZSTD_createCStream_advanced(ZSTD_customMem customMem);
609size_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>
Yann Colletc7fe2622017-05-23 13:16:00 -0700[diff] [blame]610size_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. */<b>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]611size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs, const void* dict, size_t dictSize,
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]612 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>
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]613size_t ZSTD_initCStream_usingCDict(ZSTD_CStream* zcs, const ZSTD_CDict* cdict); </b>/**< note : cdict will just be referenced, and must outlive compression session */<b>
Yann Collet8c910d22017-06-03 01:15:02 -0700[diff] [blame]614size_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>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]615</pre></b><BR>
Yann Collet4b987ad2017-04-10 17:50:44 -0700[diff] [blame]616<pre><b>size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize);
617</b><p> start a new compression job, using same parameters from previous job.
618 This is typically useful to skip dictionary loading stage, since it will re-use it in-place..
619 Note that zcs must be init at least once before using ZSTD_resetCStream().
620 pledgedSrcSize==0 means "srcSize unknown".
621 If pledgedSrcSize > 0, its value must be correct, as it will be written in header, and controlled at the end.
622 @return : 0, or an error code (which can be tested using ZSTD_isError())
623</p></pre><BR>
624
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]625<h3>Advanced Streaming decompression functions</h3><pre></pre><b><pre>typedef enum { DStream_p_maxWindowSize } ZSTD_DStreamParameter_e;
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]626ZSTD_DStream* ZSTD_createDStream_advanced(ZSTD_customMem customMem);
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]627size_t ZSTD_setDStreamParameter(ZSTD_DStream* zds, ZSTD_DStreamParameter_e paramType, unsigned paramValue);
Yann Collet5a36c062017-05-09 15:11:30 -0700[diff] [blame]628size_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>
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]629size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict); </b>/**< note : ddict will just be referenced, and must outlive decompression session */<b>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]630size_t ZSTD_resetDStream(ZSTD_DStream* zds); </b>/**< re-use decompression parameters from previous init; saves dictionary loading */<b>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]631</pre></b><BR>
632<a name="Chapter17"></a><h2>Buffer-less and synchronous inner streaming functions</h2><pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]633 This is an advanced API, giving full control over buffer management, for users which need direct control over memory.
634 But it's also a complex one, with many restrictions (documented below).
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]635 Prefer using normal streaming API for an easier experience
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]636
637<BR></pre>
638
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]639<a name="Chapter18"></a><h2>Buffer-less streaming compression (synchronous mode)</h2><pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]640 A ZSTD_CCtx object is required to track streaming operations.
641 Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource.
642 ZSTD_CCtx object can be re-used multiple times within successive compression operations.
643
644 Start by initializing a context.
645 Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary compression,
646 or ZSTD_compressBegin_advanced(), for finer parameter control.
647 It's also possible to duplicate a reference context which has already been initialized, using ZSTD_copyCCtx()
648
649 Then, consume your input using ZSTD_compressContinue().
650 There are some important considerations to keep in mind when using this advanced function :
651 - ZSTD_compressContinue() has no internal buffer. It uses externally provided buffer only.
652 - Interface is synchronous : input is consumed entirely and produce 1+ (or more) compressed blocks.
653 - Caller must ensure there is enough space in `dst` to store compressed data under worst case scenario.
654 Worst case evaluation is provided by ZSTD_compressBound().
655 ZSTD_compressContinue() doesn't guarantee recover after a failed compression.
656 - ZSTD_compressContinue() presumes prior input ***is still accessible and unmodified*** (up to maximum distance size, see WindowLog).
657 It remembers all previous contiguous blocks, plus one separated memory segment (which can itself consists of multiple contiguous blocks)
658 - ZSTD_compressContinue() detects that prior input has been overwritten when `src` buffer overlaps.
659 In which case, it will "discard" the relevant memory section from its history.
660
661 Finish a frame with ZSTD_compressEnd(), which will write the last block(s) and optional checksum.
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]662 It's possible to use srcSize==0, in which case, it will write a final empty block to end the frame.
663 Without last block mark, frames will be considered unfinished (corrupted) by decoders.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]664
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]665 `ZSTD_CCtx` object can be re-used (ZSTD_compressBegin()) to compress some new frame.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]666<BR></pre>
667
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]668<h3>Buffer-less streaming compression functions</h3><pre></pre><b><pre>size_t ZSTD_compressBegin(ZSTD_CCtx* cctx, int compressionLevel);
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]669size_t ZSTD_compressBegin_usingDict(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, int compressionLevel);
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]670size_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>
Yann Collet768df122017-04-26 15:42:10 -0700[diff] [blame]671size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); </b>/**< note: fails if cdict==NULL */<b>
Yann Collet715b9aa2017-04-18 13:55:53 -0700[diff] [blame]672size_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>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]673size_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>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]674</pre></b><BR>
675<a name="Chapter19"></a><h2>Buffer-less streaming decompression (synchronous mode)</h2><pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]676 A ZSTD_DCtx object is required to track streaming operations.
677 Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it.
678 A ZSTD_DCtx object can be re-used multiple times.
679
Yann Collet7028cbd2017-05-25 18:29:08 -0700[diff] [blame]680 First typical operation is to retrieve frame parameters, using ZSTD_getFrameHeader().
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]681 It fills a ZSTD_frameParams structure which provide important information to correctly decode the frame,
682 such as the minimum rolling buffer size to allocate to decompress data (`windowSize`),
683 and the dictionary ID used.
684 (Note : content size is optional, it may not be present. 0 means : content size unknown).
685 Note that these values could be wrong, either because of data malformation, or because an attacker is spoofing deliberate false information.
686 As a consequence, check that values remain within valid application range, especially `windowSize`, before allocation.
687 Each application can set its own limit, depending on local restrictions. For extended interoperability, it is recommended to support at least 8 MB.
688 Frame parameters are extracted from the beginning of the compressed frame.
689 Data fragment must be large enough to ensure successful decoding, typically `ZSTD_frameHeaderSize_max` bytes.
690 @result : 0 : successful decoding, the `ZSTD_frameParams` structure is correctly filled.
691 >0 : `srcSize` is too small, please provide at least @result bytes on next attempt.
692 errorCode, which can be tested using ZSTD_isError().
693
Yann Collet6d4fef32017-05-17 18:36:15 -0700[diff] [blame]694 Start decompression, with ZSTD_decompressBegin().
695 If decompression requires a dictionary, use ZSTD_decompressBegin_usingDict() or ZSTD_decompressBegin_usingDDict().
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]696 Alternatively, you can copy a prepared context, using ZSTD_copyDCtx().
697
698 Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively.
699 ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize' to ZSTD_decompressContinue().
700 ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will fail.
701
702 @result of ZSTD_decompressContinue() is the number of bytes regenerated within 'dst' (necessarily <= dstCapacity).
703 It can be zero, which is not an error; it just means ZSTD_decompressContinue() has decoded some metadata item.
704 It can also be an error code, which can be tested with ZSTD_isError().
705
706 ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize`.
707 They should preferably be located contiguously, prior to current block.
708 Alternatively, a round buffer of sufficient size is also possible. Sufficient size is determined by frame parameters.
709 ZSTD_decompressContinue() is very sensitive to contiguity,
710 if 2 blocks don't follow each other, make sure that either the compressor breaks contiguity at the same place,
711 or that previous contiguous segment is large enough to properly handle maximum back-reference.
712
713 A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero.
714 Context can then be reset to start a new decompression.
715
716 Note : it's possible to know if next input to present is a header or a block, using ZSTD_nextInputType().
717 This information is not required to properly decode a frame.
718
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]719 == Special case : skippable frames
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]720
721 Skippable frames allow integration of user-defined data into a flow of concatenated frames.
722 Skippable frames will be ignored (skipped) by a decompressor. The format of skippable frames is as follows :
723 a) Skippable frame ID - 4 Bytes, Little endian format, any value from 0x184D2A50 to 0x184D2A5F
724 b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits
725 c) Frame Content - any content (User Data) of length equal to Frame Size
726 For skippable frames ZSTD_decompressContinue() always returns 0.
Yann Collet7028cbd2017-05-25 18:29:08 -0700[diff] [blame]727 For skippable frames ZSTD_getFrameHeader() returns fparamsPtr->windowLog==0 what means that a frame is skippable.
Yann Collet831b4892017-02-23 23:09:10 -0800[diff] [blame]728 Note : If fparamsPtr->frameContentSize==0, it is ambiguous: the frame might actually be a Zstd encoded frame with no content.
729 For purposes of decompression, it is valid in both cases to skip the frame using
730 ZSTD_findFrameCompressedSize to find its size in bytes.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]731 It also returns Frame Size as fparamsPtr->frameContentSize.
732<BR></pre>
733
Yann Colletcef02d92017-05-10 11:14:08 -0700[diff] [blame]734<h3>Buffer-less streaming decompression functions</h3><pre></pre><b><pre>size_t ZSTD_getFrameHeader(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize); </b>/**< doesn't consume input, see details below */<b>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]735size_t ZSTD_decompressBegin(ZSTD_DCtx* dctx);
736size_t ZSTD_decompressBegin_usingDict(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
Yann Collet6d4fef32017-05-17 18:36:15 -0700[diff] [blame]737size_t ZSTD_decompressBegin_usingDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict);
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]738void ZSTD_copyDCtx(ZSTD_DCtx* dctx, const ZSTD_DCtx* preparedDCtx);
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]739</pre></b><BR>
Yann Collet6d4fef32017-05-17 18:36:15 -0700[diff] [blame]740<pre><b>typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e;
741</b></pre><BR>
Yann Colletbf991502017-06-19 12:56:25 -0700[diff] [blame]742<h3>New advanced API (experimental, and compression only)</h3><pre></pre><b><pre></pre></b><BR>
743<pre><b>typedef enum {
744 </b>/* compression parameters */<b>
745 ZSTD_p_compressionLevel=100, </b>/* Update all compression parameters according to pre-defined cLevel table<b>
746 * Default level is ZSTD_CLEVEL_DEFAULT==3.
747 * Special: value 0 means "do not change cLevel". */
748 ZSTD_p_windowLog, </b>/* Maximum allowed back-reference distance, expressed as power of 2.<b>
749 * Must be clamped between ZSTD_WINDOWLOG_MIN and ZSTD_WINDOWLOG_MAX.
Yann Colletbf991502017-06-19 12:56:25 -0700[diff] [blame]750 * Special: value 0 means "do not change windowLog". */
751 ZSTD_p_hashLog, </b>/* Size of the probe table, as a power of 2.<b>
752 * Resulting table size is (1 << (hashLog+2)).
753 * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX.
754 * Larger tables improve compression ratio of strategies <= dFast,
755 * and improve speed of strategies > dFast.
756 * Special: value 0 means "do not change hashLog". */
757 ZSTD_p_chainLog, </b>/* Size of the full-search table, as a power of 2.<b>
758 * Resulting table size is (1 << (chainLog+2)).
759 * Larger tables result in better and slower compression.
760 * This parameter is useless when using "fast" strategy.
761 * Special: value 0 means "do not change chainLog". */
762 ZSTD_p_searchLog, </b>/* Number of search attempts, as a power of 2.<b>
763 * More attempts result in better and slower compression.
764 * This parameter is useless when using "fast" and "dFast" strategies.
765 * Special: value 0 means "do not change searchLog". */
766 ZSTD_p_minMatch, </b>/* Minimum size of searched matches (note : repCode matches can be smaller).<b>
767 * Larger values make faster compression and decompression, but decrease ratio.
768 * Must be clamped between ZSTD_SEARCHLENGTH_MIN and ZSTD_SEARCHLENGTH_MAX.
769 * Note that currently, for all strategies < btopt, effective minimum is 4.
770 * Note that currently, for all strategies > fast, effective maximum is 6.
771 * Special: value 0 means "do not change minMatchLength". */
772 ZSTD_p_targetLength, </b>/* Only useful for strategies >= btopt.<b>
773 * Length of Match considered "good enough" to stop search.
774 * Larger values make compression stronger and slower.
775 * Special: value 0 means "do not change targetLength". */
776 ZSTD_p_compressionStrategy, </b>/* See ZSTD_strategy enum definition.<b>
777 * Cast selected strategy as unsigned for ZSTD_CCtx_setParameter() compatibility.
778 * The higher the value of selected strategy, the more complex it is,
779 * resulting in stronger and slower compression.
780 * Special: value 0 means "do not change strategy". */
781#if 0
782 ZSTD_p_windowSize, </b>/* Maximum allowed back-reference distance.<b>
783 * Can be set to a more precise value than windowLog.
784 * Will be transparently reduced to closest possible inferior value
785 * (see Zstandard compression format) */
786 </b>/* Not ready yet ! */<b>
787#endif
788
789 </b>/* frame parameters */<b>
790 ZSTD_p_contentSizeFlag=200, </b>/* Content size is written into frame header _whenever known_ (default:1) */<b>
791 ZSTD_p_checksumFlag, </b>/* A 32-bits checksum of content is written at end of frame (default:0) */<b>
792 ZSTD_p_dictIDFlag, </b>/* When applicable, dictID of dictionary is provided in frame header (default:1) */<b>
793
794 </b>/* dictionary parameters */<b>
795 ZSTD_p_refDictContent=300, </b>/* Content of dictionary content will be referenced, instead of copied (default:0).<b>
796 * This avoids duplicating dictionary content.
Yann Collet7bd1a292017-06-21 11:50:33 -0700[diff] [blame^]797 * But it also requires that dictionary buffer outlives its users */
798 </b>/* Not ready yet ! <=================================== */<b>
799 ZSTD_p_dictMode, </b>/* Select how dictionary must be interpreted. Value must be from type ZSTD_dictMode_e.<b>
800 * default : 0==auto : dictionary will be "full" if it respects specification, otherwise it will be "rawContent" */
Yann Colletbf991502017-06-19 12:56:25 -0700[diff] [blame]801
802 </b>/* multi-threading parameters */<b>
803 ZSTD_p_nbThreads=400, </b>/* Select how many threads a compression job can spawn (default:1)<b>
804 * More threads improve speed, but also increase memory usage.
805 * Can only receive a value > 1 if ZSTD_MULTITHREAD is enabled.
806 * Special: value 0 means "do not change nbThreads" */
807 ZSTD_p_jobSize, </b>/* Size of a compression job. Each compression job is completed in parallel.<b>
808 * 0 means default, which is dynamically determined based on compression parameters.
809 * Job size must be a minimum of overlapSize, or 1 KB, whichever is largest
810 * The minimum size is automatically and transparently enforced */
811 ZSTD_p_overlapSizeLog, </b>/* Size of previous input reloaded at the beginning of each job.<b>
812 * 0 => no overlap, 6(default) => use 1/8th of windowSize, >=9 => use full windowSize */
813
814 </b>/* advanced parameters - may not remain available after API update */<b>
815 ZSTD_p_forceMaxWindow=1100, </b>/* Force back-references to remain < windowSize,<b>
Yann Collet7bd1a292017-06-21 11:50:33 -0700[diff] [blame^]816 * even when referencing into Dictionary content.
Yann Colletbf991502017-06-19 12:56:25 -0700[diff] [blame]817 * default : 0 when using a CDict, 1 when using a Prefix */
818} ZSTD_cParameter;
819</b></pre><BR>
820<pre><b>size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, unsigned value);
821</b><p> Set one compression parameter, selected by enum ZSTD_cParameter.
822 Note : when `value` is an enum, cast it to unsigned for proper type checking.
823 @result : 0, or an error code (which can be tested with ZSTD_isError()).
824</p></pre><BR>
825
826<pre><b>size_t ZSTD_CCtx_setPledgedSrcSize(ZSTD_CCtx* cctx, unsigned long long pledgedSrcSize);
827</b><p> Total input data size to be compressed as a single frame.
828 This value will be controlled at the end, and result in error if not respected.
829 @result : 0, or an error code (which can be tested with ZSTD_isError()).
830 Note 1 : 0 means zero, empty.
831 In order to mean "unknown content size", pass constant ZSTD_CONTENTSIZE_UNKNOWN.
832 Note that ZSTD_CONTENTSIZE_UNKNOWN is default value for new compression jobs.
833 Note 2 : If all data is provided and consumed in a single round,
834 this value is overriden by srcSize instead.
835</p></pre><BR>
836
837<pre><b>size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
838</b><p> Create an internal CDict from dict buffer.
839 Decompression will have to use same buffer.
840 @result : 0, or an error code (which can be tested with ZSTD_isError()).
Yann Collet7bd1a292017-06-21 11:50:33 -0700[diff] [blame^]841 Special : Adding a NULL (or 0-size) dictionary invalidates any previous dictionary,
Yann Colletbf991502017-06-19 12:56:25 -0700[diff] [blame]842 meaning "return to no-dictionary mode".
843 Note 1 : Dictionary content will be copied internally,
844 except if ZSTD_p_refDictContent is set.
845 Note 2 : Loading a dictionary involves building tables, which are dependent on compression parameters.
Yann Collet7bd1a292017-06-21 11:50:33 -0700[diff] [blame^]846 For this reason, compression parameters cannot be changed anymore after loading a dictionary.
Yann Colletbf991502017-06-19 12:56:25 -0700[diff] [blame]847 It's also a CPU-heavy operation, with non-negligible impact on latency.
848 Note 3 : Dictionary will be used for all future compression jobs.
849 To return to "no-dictionary" situation, load a NULL dictionary
850</p></pre><BR>
851
852<pre><b>size_t ZSTD_CCtx_refCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict);
853</b><p> Ref a prepared dictionary, to be used for all next compression jobs.
854 Note that compression parameters are enforced from within CDict,
855 and supercede any compression parameter previously set within CCtx.
856 The dictionary will remain valid for future compression jobs using same CCtx.
857 @result : 0, or an error code (which can be tested with ZSTD_isError()).
858 Special : adding a NULL CDict means "return to no-dictionary mode".
859 Note 1 : Currently, only one dictionary can be managed.
860 Adding a new dictionary effectively "discards" any previous one.
861 Note 2 : CDict is just referenced, its lifetime must outlive CCtx.
862
863</p></pre><BR>
864
Yann Collet7bd1a292017-06-21 11:50:33 -0700[diff] [blame^]865<pre><b>size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize); </b>/* Not ready yet ! <===================================== */<b>
Yann Colletbf991502017-06-19 12:56:25 -0700[diff] [blame]866</b><p> Reference a prefix (content-only dictionary) to bootstrap next compression job.
867 Decompression will have to use same prefix.
868 Prefix is only used once. Tables are discarded at end of compression job.
869 If there is a need to use same prefix multiple times, consider embedding it into a ZSTD_CDict.
870 @result : 0, or an error code (which can be tested with ZSTD_isError()).
871 Special : Adding a NULL (or 0-size) dictionary invalidates any previous prefix, meaning "return to no-dictionary mode".
872 Note 1 : Prefix buffer is referenced. It must outlive compression job.
873 Note 2 : Referencing a prefix involves building tables, which are dependent on compression parameters.
874 It's a CPU-heavy operation, with non-negligible impact on latency.
875</p></pre><BR>
876
877<pre><b>typedef enum {
878 ZSTD_e_continue=0, </b>/* collect more data, encoder transparently decides when to output result, for optimal conditions */<b>
879 ZSTD_e_flush, </b>/* flush any data provided so far - frame will continue, future data can still reference previous data for better compression */<b>
880 ZSTD_e_end </b>/* flush any remaining data and ends current frame. Any future compression starts a new frame. */<b>
881} ZSTD_EndDirective;
882</b></pre><BR>
883<pre><b>size_t ZSTD_compress_generic (ZSTD_CCtx* cctx,
884 ZSTD_outBuffer* output,
885 ZSTD_inBuffer* input,
886 ZSTD_EndDirective endOp);
887</b><p> Behave about the same as ZSTD_compressStream. To note :
Yann Collet7bd1a292017-06-21 11:50:33 -0700[diff] [blame^]888 - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_setParameter()
Yann Colletbf991502017-06-19 12:56:25 -0700[diff] [blame]889 - Compression parameters cannot be changed once compression is started.
890 - *dstPos must be <= dstCapacity, *srcPos must be <= srcSize
891 - *dspPos and *srcPos will be updated. They are guaranteed to remain below their respective limit.
892 - @return provides the minimum amount of data still to flush from internal buffers
893 or an error code, which can be tested using ZSTD_isError().
Yann Collet7bd1a292017-06-21 11:50:33 -0700[diff] [blame^]894 if @return != 0, flush is not fully completed, there is some data left within internal buffers.
Yann Colletbf991502017-06-19 12:56:25 -0700[diff] [blame]895 - after a ZSTD_e_end directive, if internal buffer is not fully flushed,
Yann Collet7bd1a292017-06-21 11:50:33 -0700[diff] [blame^]896 only ZSTD_e_end or ZSTD_e_flush operations are allowed.
Yann Colletbf991502017-06-19 12:56:25 -0700[diff] [blame]897 It is necessary to fully flush internal buffers
898 before starting a new compression job, or changing compression parameters.
899
900</p></pre><BR>
901
902<pre><b>void ZSTD_CCtx_reset(ZSTD_CCtx* cctx); </b>/* Not ready yet ! */<b>
903</b><p> Return a CCtx to clean state.
904 Useful after an error, or to interrupt an ongoing compression job and start a new one.
905 Any internal data not yet flushed is cancelled.
906 Dictionary (if any) is dropped.
907 It's possible to modify compression parameters after a reset.
908
909</p></pre><BR>
910
911<pre><b>size_t ZSTD_compress_generic_simpleArgs (
912 ZSTD_CCtx* cctx,
913 void* dst, size_t dstCapacity, size_t* dstPos,
914 const void* src, size_t srcSize, size_t* srcPos,
915 ZSTD_EndDirective endOp);
916</b><p> Same as ZSTD_compress_generic(),
917 but using only integral types as arguments.
918 Argument list is larger and less expressive than ZSTD_{in,out}Buffer,
919 but can be helpful for binders from dynamic languages
920 which have troubles handling structures containing memory pointers.
921
922</p></pre><BR>
923
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]924<a name="Chapter20"></a><h2>Block functions</h2><pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]925 Block functions produce and decode raw zstd blocks, without frame metadata.
926 Frame metadata cost is typically ~18 bytes, which can be non-negligible for very small blocks (< 100 bytes).
927 User will have to take in charge required information to regenerate data, such as compressed and content sizes.
928
929 A few rules to respect :
930 - Compressing and decompressing require a context structure
931 + Use ZSTD_createCCtx() and ZSTD_createDCtx()
932 - It is necessary to init context before starting
Yann Collet715b9aa2017-04-18 13:55:53 -0700[diff] [blame]933 + compression : any ZSTD_compressBegin*() variant, including with dictionary
934 + decompression : any ZSTD_decompressBegin*() variant, including with dictionary
935 + copyCCtx() and copyDCtx() can be used too
Yann Colletfa3671e2017-05-19 10:51:30 -0700[diff] [blame]936 - Block size is limited, it must be <= ZSTD_getBlockSize() <= ZSTD_BLOCKSIZE_MAX
Yann Collet715b9aa2017-04-18 13:55:53 -0700[diff] [blame]937 + If input is larger than a block size, it's necessary to split input data into multiple blocks
938 + For inputs larger than a single block size, consider using the regular ZSTD_compress() instead.
939 Frame metadata is not that costly, and quickly becomes negligible as source size grows larger.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]940 - When a block is considered not compressible enough, ZSTD_compressBlock() result will be zero.
941 In which case, nothing is produced into `dst`.
942 + User must test for such outcome and deal directly with uncompressed data
943 + ZSTD_decompressBlock() doesn't accept uncompressed data as input !!!
Yann Collet715b9aa2017-04-18 13:55:53 -0700[diff] [blame]944 + In case of multiple successive blocks, should some of them be uncompressed,
945 decoder must be informed of their existence in order to follow proper history.
946 Use ZSTD_insertBlock() for such a case.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]947<BR></pre>
948
Yann Colletfa3671e2017-05-19 10:51:30 -0700[diff] [blame]949<h3>Raw zstd block functions</h3><pre></pre><b><pre>size_t ZSTD_getBlockSize (const ZSTD_CCtx* cctx);
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]950size_t ZSTD_compressBlock (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
951size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
952size_t ZSTD_insertBlock(ZSTD_DCtx* dctx, const void* blockStart, size_t blockSize); </b>/**< insert block into `dctx` history. Useful for uncompressed blocks */<b>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]953</pre></b><BR>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]954</html>
955</body>