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gerrit-public.fairphone.software / platform / external / zstd / 0be6fd342984d375965255bff77f8936bcd85f8a / . / doc / zstd_manual.html
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Yann Collet8b669532017-04-27 12:50:20 -0700[diff] [blame]4<title>zstd 1.2.0 Manual</title>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]5</head>
6<body>
Yann Collet8b669532017-04-27 12:50:20 -0700[diff] [blame]7<h1>zstd 1.2.0 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>
16<li><a href="#Chapter6">Fast dictionary API</a></li>
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 Collet77575772017-02-22 01:10:43 -0800[diff] [blame]22<li><a href="#Chapter12">Compressed size functions</a></li>
23<li><a href="#Chapter13">Decompressed size functions</a></li>
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>
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]34 zstd, short for Zstandard, is a fast lossless compression algorithm, targeting real-time compression scenarios
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]35 at zlib-level and better compression ratios. The zstd compression library provides in-memory compression and
36 decompression functions. The library supports compression levels from 1 up to ZSTD_maxCLevel() which is 22.
Yann Collet831b4892017-02-23 23:09:10 -0800[diff] [blame]37 Levels >= 20, labeled `--ultra`, should be used with caution, as they require more memory.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]38 Compression can be done in:
39 - a single step (described as Simple API)
40 - a single step, reusing a context (described as Explicit memory management)
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]41 - unbounded multiple steps (described as Streaming compression)
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]42 The compression ratio achievable on small data can be highly improved using compression with a dictionary in:
43 - a single step (described as Simple dictionary API)
44 - a single step, reusing a dictionary (described as Fast dictionary API)
45
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]46 Advanced experimental functions can be accessed using #define ZSTD_STATIC_LINKING_ONLY before including zstd.h.
47 These APIs shall never be used with a dynamic library.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]48 They are not "stable", their definition may change in the future. Only static linking is allowed.
49<BR></pre>
50
51<a name="Chapter2"></a><h2>Version</h2><pre></pre>
52
Przemyslaw Skibinski4da53212016-12-07 11:18:40 +0100[diff] [blame]53<pre><b>unsigned ZSTD_versionNumber(void); </b>/**< library version number; to be used when checking dll version */<b>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]54</b></pre><BR>
55<a name="Chapter3"></a><h2>Simple API</h2><pre></pre>
56
57<pre><b>size_t ZSTD_compress( void* dst, size_t dstCapacity,
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]58 const void* src, size_t srcSize,
59 int compressionLevel);
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]60</b><p> Compresses `src` content as a single zstd compressed frame into already allocated `dst`.
61 Hint : compression runs faster if `dstCapacity` >= `ZSTD_compressBound(srcSize)`.
62 @return : compressed size written into `dst` (<= `dstCapacity),
63 or an error code if it fails (which can be tested using ZSTD_isError()).
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]64</p></pre><BR>
65
66<pre><b>size_t ZSTD_decompress( void* dst, size_t dstCapacity,
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]67 const void* src, size_t compressedSize);
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]68</b><p> `compressedSize` : must be the _exact_ size of some number of compressed and/or skippable frames.
69 `dstCapacity` is an upper bound of originalSize.
70 If user cannot imply a maximum upper bound, it's better to use streaming mode to decompress data.
71 @return : the number of bytes decompressed into `dst` (<= `dstCapacity`),
72 or an errorCode if it fails (which can be tested using ZSTD_isError()).
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]73</p></pre><BR>
74
75<pre><b>unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize);
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]76</b><p> NOTE: This function is planned to be obsolete, in favour of ZSTD_getFrameContentSize.
77 ZSTD_getFrameContentSize functions the same way, returning the decompressed size of a single
78 frame, but distinguishes empty frames from frames with an unknown size, or errors.
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]79
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]80 Additionally, ZSTD_findDecompressedSize can be used instead. It can handle multiple
81 concatenated frames in one buffer, and so is more general.
82 As a result however, it requires more computation and entire frames to be passed to it,
83 as opposed to ZSTD_getFrameContentSize which requires only a single frame's header.
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]84
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]85 'src' is the start of a zstd compressed frame.
86 @return : content size to be decompressed, as a 64-bits value _if known_, 0 otherwise.
87 note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode.
88 When `return==0`, data to decompress could be any size.
89 In which case, it's necessary to use streaming mode to decompress data.
90 Optionally, application can still use ZSTD_decompress() while relying on implied limits.
91 (For example, data may be necessarily cut into blocks <= 16 KB).
92 note 2 : decompressed size is always present when compression is done with ZSTD_compress()
93 note 3 : decompressed size can be very large (64-bits value),
94 potentially larger than what local system can handle as a single memory segment.
95 In which case, it's necessary to use streaming mode to decompress data.
96 note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified.
97 Always ensure result fits within application's authorized limits.
98 Each application can set its own limits.
99 note 5 : when `return==0`, if precise failure cause is needed, use ZSTD_getFrameParams() to know more.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]100</p></pre><BR>
101
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]102<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]103size_t ZSTD_compressBound(size_t srcSize); </b>/*!< maximum compressed size in worst case scenario */<b>
104unsigned ZSTD_isError(size_t code); </b>/*!< tells if a `size_t` function result is an error code */<b>
105const 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]106</pre></b><BR>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]107<a name="Chapter4"></a><h2>Explicit memory management</h2><pre></pre>
108
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]109<h3>Compression context</h3><pre> When compressing many times,
110 it is recommended to allocate a context just once, and re-use it for each successive compression operation.
111 This will make workload friendlier for system's memory.
112 Use one context per thread for parallel execution in multi-threaded environments.
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]113</pre><b><pre>typedef struct ZSTD_CCtx_s ZSTD_CCtx;
114ZSTD_CCtx* ZSTD_createCCtx(void);
115size_t ZSTD_freeCCtx(ZSTD_CCtx* cctx);
116</pre></b><BR>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]117<pre><b>size_t ZSTD_compressCCtx(ZSTD_CCtx* ctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize, 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,
122 it is recommended to allocate a context just once, and re-use it for each successive compression operation.
123 This will make workload friendlier for system's memory.
124 Use one context per thread for parallel execution in multi-threaded environments.
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]125</pre><b><pre>typedef struct ZSTD_DCtx_s ZSTD_DCtx;
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]126ZSTD_DCtx* ZSTD_createDCtx(void);
127size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx);
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]128</pre></b><BR>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]129<pre><b>size_t ZSTD_decompressDCtx(ZSTD_DCtx* ctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]130</b><p> Same as ZSTD_decompress(), requires an allocated ZSTD_DCtx (see ZSTD_createDCtx()).
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]131</p></pre><BR>
132
133<a name="Chapter5"></a><h2>Simple dictionary API</h2><pre></pre>
134
135<pre><b>size_t ZSTD_compress_usingDict(ZSTD_CCtx* ctx,
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]136 void* dst, size_t dstCapacity,
137 const void* src, size_t srcSize,
138 const void* dict,size_t dictSize,
139 int compressionLevel);
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]140</b><p> Compression using a predefined Dictionary (see dictBuilder/zdict.h).
Nick Terrelld82efd82016-11-02 16:47:53 -0700[diff] [blame]141 Note : This function loads the dictionary, resulting in significant startup delay.
142 Note : When `dict == NULL || dictSize < 8` no dictionary is used.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]143</p></pre><BR>
144
145<pre><b>size_t ZSTD_decompress_usingDict(ZSTD_DCtx* dctx,
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]146 void* dst, size_t dstCapacity,
147 const void* src, size_t srcSize,
148 const void* dict,size_t dictSize);
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]149</b><p> Decompression using a predefined Dictionary (see dictBuilder/zdict.h).
150 Dictionary must be identical to the one used during compression.
Nick Terrelld82efd82016-11-02 16:47:53 -0700[diff] [blame]151 Note : This function loads the dictionary, resulting in significant startup delay.
152 Note : When `dict == NULL || dictSize < 8` no dictionary is used.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]153</p></pre><BR>
154
155<a name="Chapter6"></a><h2>Fast dictionary API</h2><pre></pre>
156
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]157<pre><b>ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize, int compressionLevel);
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]158</b><p> When compressing multiple messages / blocks with the same dictionary, it's recommended to load it just once.
159 ZSTD_createCDict() will create a digested dictionary, ready to start future compression operations without startup delay.
160 ZSTD_CDict can be created once and used by multiple threads concurrently, as its usage is read-only.
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]161 `dictBuffer` can be released after ZSTD_CDict creation, as its content is copied within CDict
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]162</p></pre><BR>
163
164<pre><b>size_t ZSTD_freeCDict(ZSTD_CDict* CDict);
Nick Terrelld82efd82016-11-02 16:47:53 -0700[diff] [blame]165</b><p> Function frees memory allocated by ZSTD_createCDict().
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]166</p></pre><BR>
167
168<pre><b>size_t ZSTD_compress_usingCDict(ZSTD_CCtx* cctx,
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]169 void* dst, size_t dstCapacity,
170 const void* src, size_t srcSize,
171 const ZSTD_CDict* cdict);
Yann Collet715b9aa2017-04-18 13:55:53 -0700[diff] [blame]172</b><p> Compression using a digested Dictionary.
173 Faster startup than ZSTD_compress_usingDict(), recommended when same dictionary is used multiple times.
174 Note that compression level is decided during dictionary creation.
175 Frame parameters are hardcoded (dictID=yes, contentSize=yes, checksum=no)
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]176</p></pre><BR>
177
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]178<pre><b>ZSTD_DDict* ZSTD_createDDict(const void* dictBuffer, size_t dictSize);
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]179</b><p> Create a digested dictionary, ready to start decompression operation without startup delay.
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]180 dictBuffer can be released after DDict creation, as its content is copied inside DDict
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]181</p></pre><BR>
182
183<pre><b>size_t ZSTD_freeDDict(ZSTD_DDict* ddict);
184</b><p> Function frees memory allocated with ZSTD_createDDict()
185</p></pre><BR>
186
187<pre><b>size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx,
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]188 void* dst, size_t dstCapacity,
189 const void* src, size_t srcSize,
190 const ZSTD_DDict* ddict);
Nick Terrelld82efd82016-11-02 16:47:53 -0700[diff] [blame]191</b><p> Decompression using a digested Dictionary.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]192 Faster startup than ZSTD_decompress_usingDict(), recommended when same dictionary is used multiple times.
193</p></pre><BR>
194
195<a name="Chapter7"></a><h2>Streaming</h2><pre></pre>
196
197<pre><b>typedef struct ZSTD_inBuffer_s {
198 const void* src; </b>/**< start of input buffer */<b>
199 size_t size; </b>/**< size of input buffer */<b>
200 size_t pos; </b>/**< position where reading stopped. Will be updated. Necessarily 0 <= pos <= size */<b>
201} ZSTD_inBuffer;
202</b></pre><BR>
203<pre><b>typedef struct ZSTD_outBuffer_s {
204 void* dst; </b>/**< start of output buffer */<b>
205 size_t size; </b>/**< size of output buffer */<b>
206 size_t pos; </b>/**< position where writing stopped. Will be updated. Necessarily 0 <= pos <= size */<b>
207} ZSTD_outBuffer;
208</b></pre><BR>
209<a name="Chapter8"></a><h2>Streaming compression - HowTo</h2><pre>
210 A ZSTD_CStream object is required to track streaming operation.
211 Use ZSTD_createCStream() and ZSTD_freeCStream() to create/release resources.
212 ZSTD_CStream objects can be reused multiple times on consecutive compression operations.
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]213 It is recommended to re-use ZSTD_CStream in situations where many streaming operations will be achieved consecutively,
214 since it will play nicer with system's memory, by re-using already allocated memory.
215 Use one separate ZSTD_CStream per thread for parallel execution.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]216
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]217 Start a new compression by initializing ZSTD_CStream.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]218 Use ZSTD_initCStream() to start a new compression operation.
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]219 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]220
221 Use ZSTD_compressStream() repetitively to consume input stream.
222 The function will automatically update both `pos` fields.
223 Note that it may not consume the entire input, in which case `pos < size`,
224 and it's up to the caller to present again remaining data.
225 @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]226 or an error code, which can be tested using ZSTD_isError().
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]227 Note 1 : it's just a hint, to help latency a little, any other value will work fine.
228 Note 2 : size hint is guaranteed to be <= ZSTD_CStreamInSize()
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]229
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]230 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]231 `output->pos` will be updated.
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]232 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]233 @return : nb of bytes still present within internal buffer (0 if it's empty)
234 or an error code, which can be tested using ZSTD_isError().
235
236 ZSTD_endStream() instructs to finish a frame.
237 It will perform a flush and write frame epilogue.
238 The epilogue is required for decoders to consider a frame completed.
239 Similar to ZSTD_flushStream(), it may not be able to flush the full content if `output->size` is too small.
240 In which case, call again ZSTD_endStream() to complete the flush.
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]241 @return : nb of bytes still present within internal buffer (0 if it's empty, hence compression completed)
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]242 or an error code, which can be tested using ZSTD_isError().
243
244
245<BR></pre>
246
Yann Collet0be6fd32017-05-08 16:08:01 -0700[diff] [blame^]247<pre><b>typedef ZSTD_CCtx ZSTD_CStream; </b>/**< CCtx and CStream are effectively same object */<b>
248</b></pre><BR>
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]249<h3>ZSTD_CStream management functions</h3><pre></pre><b><pre>ZSTD_CStream* ZSTD_createCStream(void);
250size_t ZSTD_freeCStream(ZSTD_CStream* zcs);
251</pre></b><BR>
252<h3>Streaming compression functions</h3><pre></pre><b><pre>size_t ZSTD_initCStream(ZSTD_CStream* zcs, int compressionLevel);
253size_t ZSTD_compressStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
254size_t ZSTD_flushStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
255size_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
256</pre></b><BR>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]257<pre><b>size_t ZSTD_CStreamInSize(void); </b>/**< recommended size for input buffer */<b>
258</b></pre><BR>
259<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>
260</b></pre><BR>
261<a name="Chapter9"></a><h2>Streaming decompression - HowTo</h2><pre>
262 A ZSTD_DStream object is required to track streaming operations.
263 Use ZSTD_createDStream() and ZSTD_freeDStream() to create/release resources.
264 ZSTD_DStream objects can be re-used multiple times.
265
266 Use ZSTD_initDStream() to start a new decompression operation,
267 or ZSTD_initDStream_usingDict() if decompression requires a dictionary.
268 @return : recommended first input size
269
270 Use ZSTD_decompressStream() repetitively to consume your input.
271 The function will update both `pos` fields.
272 If `input.pos < input.size`, some input has not been consumed.
273 It's up to the caller to present again remaining data.
274 If `output.pos < output.size`, decoder has flushed everything it could.
275 @return : 0 when a frame is completely decoded and fully flushed,
276 an error code, which can be tested using ZSTD_isError(),
Przemyslaw Skibinski4da53212016-12-07 11:18:40 +0100[diff] [blame]277 any other value > 0, which means there is still some decoding to do to complete current frame.
278 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]279
280<BR></pre>
281
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]282<h3>ZSTD_DStream management functions</h3><pre></pre><b><pre>ZSTD_DStream* ZSTD_createDStream(void);
283size_t ZSTD_freeDStream(ZSTD_DStream* zds);
284</pre></b><BR>
285<h3>Streaming decompression functions</h3><pre></pre><b><pre>size_t ZSTD_initDStream(ZSTD_DStream* zds);
286size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
287</pre></b><BR>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]288<pre><b>size_t ZSTD_DStreamInSize(void); </b>/*!< recommended size for input buffer */<b>
289</b></pre><BR>
290<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>
291</b></pre><BR>
292<a name="Chapter10"></a><h2>START OF ADVANCED AND EXPERIMENTAL FUNCTIONS</h2><pre> The definitions in this section are considered experimental.
293 They should never be used with a dynamic library, as they may change in the future.
294 They are provided for advanced usages.
295 Use them only in association with static linking.
296
297<BR></pre>
298
299<a name="Chapter11"></a><h2>Advanced types</h2><pre></pre>
300
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]301<pre><b>typedef enum { ZSTD_fast, ZSTD_dfast, ZSTD_greedy, ZSTD_lazy, ZSTD_lazy2, ZSTD_btlazy2, ZSTD_btopt, ZSTD_btopt2 } ZSTD_strategy; </b>/* from faster to stronger */<b>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]302</b></pre><BR>
303<pre><b>typedef struct {
304 unsigned windowLog; </b>/**< largest match distance : larger == more compression, more memory needed during decompression */<b>
305 unsigned chainLog; </b>/**< fully searched segment : larger == more compression, slower, more memory (useless for fast) */<b>
306 unsigned hashLog; </b>/**< dispatch table : larger == faster, more memory */<b>
307 unsigned searchLog; </b>/**< nb of searches : larger == more compression, slower */<b>
308 unsigned searchLength; </b>/**< match length searched : larger == faster decompression, sometimes less compression */<b>
309 unsigned targetLength; </b>/**< acceptable match size for optimal parser (only) : larger == more compression, slower */<b>
310 ZSTD_strategy strategy;
311} ZSTD_compressionParameters;
312</b></pre><BR>
313<pre><b>typedef struct {
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]314 unsigned contentSizeFlag; </b>/**< 1: content size will be in frame header (when known) */<b>
315 unsigned checksumFlag; </b>/**< 1: generate a 32-bits checksum at end of frame, for error detection */<b>
316 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]317} ZSTD_frameParameters;
318</b></pre><BR>
319<pre><b>typedef struct {
320 ZSTD_compressionParameters cParams;
321 ZSTD_frameParameters fParams;
322} ZSTD_parameters;
323</b></pre><BR>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]324<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]325typedef void (*ZSTD_freeFunction) (void* opaque, void* address);
326typedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; void* opaque; } ZSTD_customMem;
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]327</pre></b><BR>
328<a name="Chapter12"></a><h2>Compressed size functions</h2><pre></pre>
329
Yann Collet831b4892017-02-23 23:09:10 -0800[diff] [blame]330<pre><b>size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize);
331</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]332 `srcSize` must be at least as large as the frame
333 @return : the compressed size of the frame pointed to by `src`, suitable to pass to
334 `ZSTD_decompress` or similar, or an error code if given invalid input.
335</p></pre><BR>
336
337<a name="Chapter13"></a><h2>Decompressed size functions</h2><pre></pre>
338
339<pre><b>unsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize);
340</b><p> `src` should point to the start of a ZSTD encoded frame
341 `srcSize` must be at least as large as the frame header. A value greater than or equal
342 to `ZSTD_frameHeaderSize_max` is guaranteed to be large enough in all cases.
343 @return : decompressed size of the frame pointed to be `src` if known, otherwise
344 - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined
Yann Collet831b4892017-02-23 23:09:10 -0800[diff] [blame]345 - 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]346</p></pre><BR>
347
348<pre><b>unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize);
349</b><p> `src` should point the start of a series of ZSTD encoded and/or skippable frames
350 `srcSize` must be the _exact_ size of this series
351 (i.e. there should be a frame boundary exactly `srcSize` bytes after `src`)
352 @return : the decompressed size of all data in the contained frames, as a 64-bit value _if known_
353 - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN
354 - if an error occurred: ZSTD_CONTENTSIZE_ERROR
355
356 note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode.
357 When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
358 In which case, it's necessary to use streaming mode to decompress data.
359 Optionally, application can still use ZSTD_decompress() while relying on implied limits.
360 (For example, data may be necessarily cut into blocks <= 16 KB).
361 note 2 : decompressed size is always present when compression is done with ZSTD_compress()
362 note 3 : decompressed size can be very large (64-bits value),
363 potentially larger than what local system can handle as a single memory segment.
364 In which case, it's necessary to use streaming mode to decompress data.
365 note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified.
366 Always ensure result fits within application's authorized limits.
367 Each application can set its own limits.
368 note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to
369 read each contained frame header. This is efficient as most of the data is skipped,
370 however it does mean that all frame data must be present and valid.
371</p></pre><BR>
372
373<a name="Chapter14"></a><h2>Advanced compression functions</h2><pre></pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]374
375<pre><b>size_t ZSTD_estimateCCtxSize(ZSTD_compressionParameters cParams);
376</b><p> Gives the amount of memory allocated for a ZSTD_CCtx given a set of compression parameters.
377 `frameContentSize` is an optional parameter, provide `0` if unknown
378</p></pre><BR>
379
380<pre><b>ZSTD_CCtx* ZSTD_createCCtx_advanced(ZSTD_customMem customMem);
381</b><p> Create a ZSTD compression context using external alloc and free functions
382</p></pre><BR>
383
384<pre><b>size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx);
385</b><p> Gives the amount of memory used by a given ZSTD_CCtx
386</p></pre><BR>
387
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]388<pre><b>typedef enum {
Yann Collet14312d82017-02-23 23:42:12 -0800[diff] [blame]389 ZSTD_p_forceWindow, </b>/* Force back-references to remain < windowSize, even when referencing Dictionary content (default:0) */<b>
390 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]391} ZSTD_CCtxParameter;
392</b></pre><BR>
393<pre><b>size_t ZSTD_setCCtxParameter(ZSTD_CCtx* cctx, ZSTD_CCtxParameter param, unsigned value);
394</b><p> Set advanced parameters, selected through enum ZSTD_CCtxParameter
395 @result : 0, or an error code (which can be tested with ZSTD_isError())
396</p></pre><BR>
397
398<pre><b>ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel);
399</b><p> Create a digested dictionary for compression
400 Dictionary content is simply referenced, and therefore stays in dictBuffer.
401 It is important that dictBuffer outlives CDict, it must remain read accessible throughout the lifetime of CDict
402</p></pre><BR>
403
404<pre><b>ZSTD_CDict* ZSTD_createCDict_advanced(const void* dict, size_t dictSize, unsigned byReference,
Yann Collet31533ba2017-04-27 00:29:04 -0700[diff] [blame]405 ZSTD_compressionParameters cParams, ZSTD_customMem customMem);
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]406</b><p> Create a ZSTD_CDict using external alloc and free, and customized compression parameters
407</p></pre><BR>
408
409<pre><b>size_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict);
410</b><p> Gives the amount of memory used by a given ZSTD_sizeof_CDict
411</p></pre><BR>
412
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]413<pre><b>ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
414</b><p> @return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize.
415 `estimatedSrcSize` value is optional, select 0 if not known
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]416</p></pre><BR>
417
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]418<pre><b>ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
419</b><p> same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of sub-component `ZSTD_compressionParameters`.
420 All fields of `ZSTD_frameParameters` are set to default (0)
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]421</p></pre><BR>
422
423<pre><b>size_t ZSTD_checkCParams(ZSTD_compressionParameters params);
424</b><p> Ensure param values remain within authorized range
425</p></pre><BR>
426
427<pre><b>ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize);
428</b><p> optimize params for a given `srcSize` and `dictSize`.
429 both values are optional, select `0` if unknown.
430</p></pre><BR>
431
Yann Colletf4bd8572017-04-27 11:31:55 -0700[diff] [blame]432<pre><b>size_t ZSTD_compress_advanced (ZSTD_CCtx* cctx,
433 void* dst, size_t dstCapacity,
434 const void* src, size_t srcSize,
435 const void* dict,size_t dictSize,
436 ZSTD_parameters params);
437</b><p> Same as ZSTD_compress_usingDict(), with fine-tune control over each compression parameter
438</p></pre><BR>
439
440<pre><b>size_t ZSTD_compress_usingCDict_advanced(ZSTD_CCtx* cctx,
441 void* dst, size_t dstCapacity,
442 const void* src, size_t srcSize,
443 const ZSTD_CDict* cdict, ZSTD_frameParameters fParams);
Yann Collet77bf59e2017-04-27 11:43:04 -0700[diff] [blame]444</b><p> Same as ZSTD_compress_usingCDict(), with fine-tune control over frame parameters
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]445</p></pre><BR>
446
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]447<a name="Chapter15"></a><h2>Advanced decompression functions</h2><pre></pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]448
Przemyslaw Skibinski4da53212016-12-07 11:18:40 +0100[diff] [blame]449<pre><b>unsigned ZSTD_isFrame(const void* buffer, size_t size);
450</b><p> Tells if the content of `buffer` starts with a valid Frame Identifier.
451 Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0.
452 Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled.
453 Note 3 : Skippable Frame Identifiers are considered valid.
454</p></pre><BR>
455
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]456<pre><b>size_t ZSTD_estimateDCtxSize(void);
457</b><p> Gives the potential amount of memory allocated to create a ZSTD_DCtx
458</p></pre><BR>
459
460<pre><b>ZSTD_DCtx* ZSTD_createDCtx_advanced(ZSTD_customMem customMem);
461</b><p> Create a ZSTD decompression context using external alloc and free functions
462</p></pre><BR>
463
464<pre><b>size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx);
465</b><p> Gives the amount of memory used by a given ZSTD_DCtx
466</p></pre><BR>
467
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]468<pre><b>ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize);
469</b><p> Create a digested dictionary, ready to start decompression operation without startup delay.
470 Dictionary content is simply referenced, and therefore stays in dictBuffer.
471 It is important that dictBuffer outlives DDict, it must remain read accessible throughout the lifetime of DDict
472</p></pre><BR>
473
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]474<pre><b>ZSTD_DDict* ZSTD_createDDict_advanced(const void* dict, size_t dictSize,
475 unsigned byReference, ZSTD_customMem customMem);
476</b><p> Create a ZSTD_DDict using external alloc and free, optionally by reference
477</p></pre><BR>
478
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]479<pre><b>size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict);
480</b><p> Gives the amount of memory used by a given ZSTD_DDict
481</p></pre><BR>
482
Przemyslaw Skibinski4da53212016-12-07 11:18:40 +0100[diff] [blame]483<pre><b>unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize);
484</b><p> Provides the dictID stored within dictionary.
485 if @return == 0, the dictionary is not conformant with Zstandard specification.
486 It can still be loaded, but as a content-only dictionary.
487</p></pre><BR>
488
489<pre><b>unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict);
490</b><p> Provides the dictID of the dictionary loaded into `ddict`.
491 If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
492 Non-conformant dictionaries can still be loaded, but as content-only dictionaries.
493</p></pre><BR>
494
495<pre><b>unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize);
496</b><p> Provides the dictID required to decompressed the frame stored within `src`.
497 If @return == 0, the dictID could not be decoded.
498 This could for one of the following reasons :
499 - The frame does not require a dictionary to be decoded (most common case).
500 - The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden information.
501 Note : this use case also happens when using a non-conformant dictionary.
502 - `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`).
503 - This is not a Zstandard frame.
Yann Collet202082f2017-04-28 16:56:39 -0700[diff] [blame]504 When identifying the exact failure cause, it's possible to use ZSTD_getFrameParams(), which will provide a more precise error code.
Przemyslaw Skibinski4da53212016-12-07 11:18:40 +0100[diff] [blame]505</p></pre><BR>
506
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]507<a name="Chapter16"></a><h2>Advanced streaming functions</h2><pre></pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]508
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]509<h3>Advanced Streaming compression functions</h3><pre></pre><b><pre>ZSTD_CStream* ZSTD_createCStream_advanced(ZSTD_customMem customMem);
Yann Collet4b987ad2017-04-10 17:50:44 -0700[diff] [blame]510size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs); </b>/**< size of CStream is variable, depending primarily on compression level */<b>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]511size_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>
512size_t ZSTD_initCStream_usingDict(ZSTD_CStream* zcs, const void* dict, size_t dictSize, int compressionLevel); </b>/**< note: a dict will not be used if dict == NULL or dictSize < 8 */<b>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]513size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs, const void* dict, size_t dictSize,
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]514 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]515size_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 Collet77bf59e2017-04-27 11:43:04 -0700[diff] [blame]516size_t ZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs, const ZSTD_CDict* cdict, unsigned long long pledgedSrcSize, ZSTD_frameParameters fParams); </b>/**< same as ZSTD_initCStream_usingCDict(), with control over frame parameters */<b>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]517</pre></b><BR>
Yann Collet4b987ad2017-04-10 17:50:44 -0700[diff] [blame]518<pre><b>size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize);
519</b><p> start a new compression job, using same parameters from previous job.
520 This is typically useful to skip dictionary loading stage, since it will re-use it in-place..
521 Note that zcs must be init at least once before using ZSTD_resetCStream().
522 pledgedSrcSize==0 means "srcSize unknown".
523 If pledgedSrcSize > 0, its value must be correct, as it will be written in header, and controlled at the end.
524 @return : 0, or an error code (which can be tested using ZSTD_isError())
525</p></pre><BR>
526
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]527<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]528ZSTD_DStream* ZSTD_createDStream_advanced(ZSTD_customMem customMem);
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]529size_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 Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]530size_t ZSTD_setDStreamParameter(ZSTD_DStream* zds, ZSTD_DStreamParameter_e paramType, unsigned paramValue);
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]531size_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]532size_t ZSTD_resetDStream(ZSTD_DStream* zds); </b>/**< re-use decompression parameters from previous init; saves dictionary loading */<b>
533size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds);
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]534</pre></b><BR>
535<a name="Chapter17"></a><h2>Buffer-less and synchronous inner streaming functions</h2><pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]536 This is an advanced API, giving full control over buffer management, for users which need direct control over memory.
537 But it's also a complex one, with many restrictions (documented below).
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]538 Prefer using normal streaming API for an easier experience
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]539
540<BR></pre>
541
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]542<a name="Chapter18"></a><h2>Buffer-less streaming compression (synchronous mode)</h2><pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]543 A ZSTD_CCtx object is required to track streaming operations.
544 Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource.
545 ZSTD_CCtx object can be re-used multiple times within successive compression operations.
546
547 Start by initializing a context.
548 Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary compression,
549 or ZSTD_compressBegin_advanced(), for finer parameter control.
550 It's also possible to duplicate a reference context which has already been initialized, using ZSTD_copyCCtx()
551
552 Then, consume your input using ZSTD_compressContinue().
553 There are some important considerations to keep in mind when using this advanced function :
554 - ZSTD_compressContinue() has no internal buffer. It uses externally provided buffer only.
555 - Interface is synchronous : input is consumed entirely and produce 1+ (or more) compressed blocks.
556 - Caller must ensure there is enough space in `dst` to store compressed data under worst case scenario.
557 Worst case evaluation is provided by ZSTD_compressBound().
558 ZSTD_compressContinue() doesn't guarantee recover after a failed compression.
559 - ZSTD_compressContinue() presumes prior input ***is still accessible and unmodified*** (up to maximum distance size, see WindowLog).
560 It remembers all previous contiguous blocks, plus one separated memory segment (which can itself consists of multiple contiguous blocks)
561 - ZSTD_compressContinue() detects that prior input has been overwritten when `src` buffer overlaps.
562 In which case, it will "discard" the relevant memory section from its history.
563
564 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]565 It's possible to use srcSize==0, in which case, it will write a final empty block to end the frame.
566 Without last block mark, frames will be considered unfinished (corrupted) by decoders.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]567
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]568 `ZSTD_CCtx` object can be re-used (ZSTD_compressBegin()) to compress some new frame.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]569<BR></pre>
570
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]571<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]572size_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]573size_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]574size_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]575size_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>
576size_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]577</pre></b><BR>
578<a name="Chapter19"></a><h2>Buffer-less streaming decompression (synchronous mode)</h2><pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]579 A ZSTD_DCtx object is required to track streaming operations.
580 Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it.
581 A ZSTD_DCtx object can be re-used multiple times.
582
583 First typical operation is to retrieve frame parameters, using ZSTD_getFrameParams().
584 It fills a ZSTD_frameParams structure which provide important information to correctly decode the frame,
585 such as the minimum rolling buffer size to allocate to decompress data (`windowSize`),
586 and the dictionary ID used.
587 (Note : content size is optional, it may not be present. 0 means : content size unknown).
588 Note that these values could be wrong, either because of data malformation, or because an attacker is spoofing deliberate false information.
589 As a consequence, check that values remain within valid application range, especially `windowSize`, before allocation.
590 Each application can set its own limit, depending on local restrictions. For extended interoperability, it is recommended to support at least 8 MB.
591 Frame parameters are extracted from the beginning of the compressed frame.
592 Data fragment must be large enough to ensure successful decoding, typically `ZSTD_frameHeaderSize_max` bytes.
593 @result : 0 : successful decoding, the `ZSTD_frameParams` structure is correctly filled.
594 >0 : `srcSize` is too small, please provide at least @result bytes on next attempt.
595 errorCode, which can be tested using ZSTD_isError().
596
597 Start decompression, with ZSTD_decompressBegin() or ZSTD_decompressBegin_usingDict().
598 Alternatively, you can copy a prepared context, using ZSTD_copyDCtx().
599
600 Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively.
601 ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize' to ZSTD_decompressContinue().
602 ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will fail.
603
604 @result of ZSTD_decompressContinue() is the number of bytes regenerated within 'dst' (necessarily <= dstCapacity).
605 It can be zero, which is not an error; it just means ZSTD_decompressContinue() has decoded some metadata item.
606 It can also be an error code, which can be tested with ZSTD_isError().
607
608 ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize`.
609 They should preferably be located contiguously, prior to current block.
610 Alternatively, a round buffer of sufficient size is also possible. Sufficient size is determined by frame parameters.
611 ZSTD_decompressContinue() is very sensitive to contiguity,
612 if 2 blocks don't follow each other, make sure that either the compressor breaks contiguity at the same place,
613 or that previous contiguous segment is large enough to properly handle maximum back-reference.
614
615 A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero.
616 Context can then be reset to start a new decompression.
617
618 Note : it's possible to know if next input to present is a header or a block, using ZSTD_nextInputType().
619 This information is not required to properly decode a frame.
620
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]621 == Special case : skippable frames
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]622
623 Skippable frames allow integration of user-defined data into a flow of concatenated frames.
624 Skippable frames will be ignored (skipped) by a decompressor. The format of skippable frames is as follows :
625 a) Skippable frame ID - 4 Bytes, Little endian format, any value from 0x184D2A50 to 0x184D2A5F
626 b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits
627 c) Frame Content - any content (User Data) of length equal to Frame Size
628 For skippable frames ZSTD_decompressContinue() always returns 0.
629 For skippable frames ZSTD_getFrameParams() returns fparamsPtr->windowLog==0 what means that a frame is skippable.
Yann Collet831b4892017-02-23 23:09:10 -0800[diff] [blame]630 Note : If fparamsPtr->frameContentSize==0, it is ambiguous: the frame might actually be a Zstd encoded frame with no content.
631 For purposes of decompression, it is valid in both cases to skip the frame using
632 ZSTD_findFrameCompressedSize to find its size in bytes.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]633 It also returns Frame Size as fparamsPtr->frameContentSize.
634<BR></pre>
635
636<pre><b>typedef struct {
637 unsigned long long frameContentSize;
638 unsigned windowSize;
639 unsigned dictID;
640 unsigned checksumFlag;
641} ZSTD_frameParams;
642</b></pre><BR>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]643<h3>Buffer-less streaming decompression functions</h3><pre></pre><b><pre>size_t ZSTD_getFrameParams(ZSTD_frameParams* fparamsPtr, const void* src, size_t srcSize); </b>/**< doesn't consume input, see details below */<b>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]644size_t ZSTD_decompressBegin(ZSTD_DCtx* dctx);
645size_t ZSTD_decompressBegin_usingDict(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
646void ZSTD_copyDCtx(ZSTD_DCtx* dctx, const ZSTD_DCtx* preparedDCtx);
647size_t ZSTD_nextSrcSizeToDecompress(ZSTD_DCtx* dctx);
648size_t ZSTD_decompressContinue(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
649typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e;
650ZSTD_nextInputType_e ZSTD_nextInputType(ZSTD_DCtx* dctx);
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]651</pre></b><BR>
652<a name="Chapter20"></a><h2>Block functions</h2><pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]653 Block functions produce and decode raw zstd blocks, without frame metadata.
654 Frame metadata cost is typically ~18 bytes, which can be non-negligible for very small blocks (< 100 bytes).
655 User will have to take in charge required information to regenerate data, such as compressed and content sizes.
656
657 A few rules to respect :
658 - Compressing and decompressing require a context structure
659 + Use ZSTD_createCCtx() and ZSTD_createDCtx()
660 - It is necessary to init context before starting
Yann Collet715b9aa2017-04-18 13:55:53 -0700[diff] [blame]661 + compression : any ZSTD_compressBegin*() variant, including with dictionary
662 + decompression : any ZSTD_decompressBegin*() variant, including with dictionary
663 + copyCCtx() and copyDCtx() can be used too
664 - Block size is limited, it must be <= ZSTD_getBlockSizeMax() <= ZSTD_BLOCKSIZE_ABSOLUTEMAX
665 + If input is larger than a block size, it's necessary to split input data into multiple blocks
666 + For inputs larger than a single block size, consider using the regular ZSTD_compress() instead.
667 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]668 - When a block is considered not compressible enough, ZSTD_compressBlock() result will be zero.
669 In which case, nothing is produced into `dst`.
670 + User must test for such outcome and deal directly with uncompressed data
671 + ZSTD_decompressBlock() doesn't accept uncompressed data as input !!!
Yann Collet715b9aa2017-04-18 13:55:53 -0700[diff] [blame]672 + In case of multiple successive blocks, should some of them be uncompressed,
673 decoder must be informed of their existence in order to follow proper history.
674 Use ZSTD_insertBlock() for such a case.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]675<BR></pre>
676
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]677<h3>Raw zstd block functions</h3><pre></pre><b><pre>size_t ZSTD_getBlockSizeMax(ZSTD_CCtx* cctx);
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]678size_t ZSTD_compressBlock (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
679size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
680size_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]681</pre></b><BR>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]682</html>
683</body>