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gerrit-public.fairphone.software / platform / external / zstd / 715b9aa113e4c9d7953b0cbeb1756d0ea3572f79 / . / doc / zstd_manual.html
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Yann Collet2e2e78d2017-03-29 16:02:47 -0700[diff] [blame]4<title>zstd 1.1.5 Manual</title>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]5</head>
6<body>
Yann Collet2e2e78d2017-03-29 16:02:47 -0700[diff] [blame]7<h1>zstd 1.1.5 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);
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[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),
Nick Terrelld82efd82016-11-02 16:47:53 -0700[diff] [blame]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 Collet77575772017-02-22 01:10:43 -0800[diff] [blame]68</b><p> `compressedSize` : must be the _exact_ size of some number of compressed and/or skippable frames.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]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`),
Nick Terrelld82efd82016-11-02 16:47:53 -0700[diff] [blame]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 Collet77575772017-02-22 01:10:43 -0800[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.
79
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.
84
85 'src' is the start of a zstd compressed frame.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]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.
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 Collet77575772017-02-22 01:10:43 -0800[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.
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);
Nick Terrelld82efd82016-11-02 16:47:53 -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
Sean Purcelldec2b962017-03-14 11:24:09 -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.
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);
Nick Terrelld82efd82016-11-02 16:47:53 -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
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]247<h3>ZSTD_CStream management functions</h3><pre></pre><b><pre>ZSTD_CStream* ZSTD_createCStream(void);
248size_t ZSTD_freeCStream(ZSTD_CStream* zcs);
249</pre></b><BR>
250<h3>Streaming compression functions</h3><pre></pre><b><pre>size_t ZSTD_initCStream(ZSTD_CStream* zcs, int compressionLevel);
251size_t ZSTD_compressStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
252size_t ZSTD_flushStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
253size_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
254</pre></b><BR>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]255<pre><b>size_t ZSTD_CStreamInSize(void); </b>/**< recommended size for input buffer */<b>
256</b></pre><BR>
257<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>
258</b></pre><BR>
259<a name="Chapter9"></a><h2>Streaming decompression - HowTo</h2><pre>
260 A ZSTD_DStream object is required to track streaming operations.
261 Use ZSTD_createDStream() and ZSTD_freeDStream() to create/release resources.
262 ZSTD_DStream objects can be re-used multiple times.
263
264 Use ZSTD_initDStream() to start a new decompression operation,
265 or ZSTD_initDStream_usingDict() if decompression requires a dictionary.
266 @return : recommended first input size
267
268 Use ZSTD_decompressStream() repetitively to consume your input.
269 The function will update both `pos` fields.
270 If `input.pos < input.size`, some input has not been consumed.
271 It's up to the caller to present again remaining data.
272 If `output.pos < output.size`, decoder has flushed everything it could.
273 @return : 0 when a frame is completely decoded and fully flushed,
274 an error code, which can be tested using ZSTD_isError(),
Przemyslaw Skibinski4da53212016-12-07 11:18:40 +0100[diff] [blame]275 any other value > 0, which means there is still some decoding to do to complete current frame.
276 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]277
278<BR></pre>
279
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]280<h3>ZSTD_DStream management functions</h3><pre></pre><b><pre>ZSTD_DStream* ZSTD_createDStream(void);
281size_t ZSTD_freeDStream(ZSTD_DStream* zds);
282</pre></b><BR>
283<h3>Streaming decompression functions</h3><pre></pre><b><pre>size_t ZSTD_initDStream(ZSTD_DStream* zds);
284size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
285</pre></b><BR>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]286<pre><b>size_t ZSTD_DStreamInSize(void); </b>/*!< recommended size for input buffer */<b>
287</b></pre><BR>
288<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>
289</b></pre><BR>
290<a name="Chapter10"></a><h2>START OF ADVANCED AND EXPERIMENTAL FUNCTIONS</h2><pre> The definitions in this section are considered experimental.
291 They should never be used with a dynamic library, as they may change in the future.
292 They are provided for advanced usages.
293 Use them only in association with static linking.
294
295<BR></pre>
296
297<a name="Chapter11"></a><h2>Advanced types</h2><pre></pre>
298
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]299<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]300</b></pre><BR>
301<pre><b>typedef struct {
302 unsigned windowLog; </b>/**< largest match distance : larger == more compression, more memory needed during decompression */<b>
303 unsigned chainLog; </b>/**< fully searched segment : larger == more compression, slower, more memory (useless for fast) */<b>
304 unsigned hashLog; </b>/**< dispatch table : larger == faster, more memory */<b>
305 unsigned searchLog; </b>/**< nb of searches : larger == more compression, slower */<b>
306 unsigned searchLength; </b>/**< match length searched : larger == faster decompression, sometimes less compression */<b>
307 unsigned targetLength; </b>/**< acceptable match size for optimal parser (only) : larger == more compression, slower */<b>
308 ZSTD_strategy strategy;
309} ZSTD_compressionParameters;
310</b></pre><BR>
311<pre><b>typedef struct {
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]312 unsigned contentSizeFlag; </b>/**< 1: content size will be in frame header (when known) */<b>
313 unsigned checksumFlag; </b>/**< 1: generate a 32-bits checksum at end of frame, for error detection */<b>
314 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]315} ZSTD_frameParameters;
316</b></pre><BR>
317<pre><b>typedef struct {
318 ZSTD_compressionParameters cParams;
319 ZSTD_frameParameters fParams;
320} ZSTD_parameters;
321</b></pre><BR>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]322<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]323typedef void (*ZSTD_freeFunction) (void* opaque, void* address);
324typedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; void* opaque; } ZSTD_customMem;
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]325</pre></b><BR>
326<a name="Chapter12"></a><h2>Compressed size functions</h2><pre></pre>
327
Yann Collet831b4892017-02-23 23:09:10 -0800[diff] [blame]328<pre><b>size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize);
329</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]330 `srcSize` must be at least as large as the frame
331 @return : the compressed size of the frame pointed to by `src`, suitable to pass to
332 `ZSTD_decompress` or similar, or an error code if given invalid input.
333</p></pre><BR>
334
335<a name="Chapter13"></a><h2>Decompressed size functions</h2><pre></pre>
336
337<pre><b>unsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize);
338</b><p> `src` should point to the start of a ZSTD encoded frame
339 `srcSize` must be at least as large as the frame header. A value greater than or equal
340 to `ZSTD_frameHeaderSize_max` is guaranteed to be large enough in all cases.
341 @return : decompressed size of the frame pointed to be `src` if known, otherwise
342 - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined
Yann Collet831b4892017-02-23 23:09:10 -0800[diff] [blame]343 - 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]344</p></pre><BR>
345
346<pre><b>unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize);
347</b><p> `src` should point the start of a series of ZSTD encoded and/or skippable frames
348 `srcSize` must be the _exact_ size of this series
349 (i.e. there should be a frame boundary exactly `srcSize` bytes after `src`)
350 @return : the decompressed size of all data in the contained frames, as a 64-bit value _if known_
351 - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN
352 - if an error occurred: ZSTD_CONTENTSIZE_ERROR
353
354 note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode.
355 When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
356 In which case, it's necessary to use streaming mode to decompress data.
357 Optionally, application can still use ZSTD_decompress() while relying on implied limits.
358 (For example, data may be necessarily cut into blocks <= 16 KB).
359 note 2 : decompressed size is always present when compression is done with ZSTD_compress()
360 note 3 : decompressed size can be very large (64-bits value),
361 potentially larger than what local system can handle as a single memory segment.
362 In which case, it's necessary to use streaming mode to decompress data.
363 note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified.
364 Always ensure result fits within application's authorized limits.
365 Each application can set its own limits.
366 note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to
367 read each contained frame header. This is efficient as most of the data is skipped,
368 however it does mean that all frame data must be present and valid.
369</p></pre><BR>
370
371<a name="Chapter14"></a><h2>Advanced compression functions</h2><pre></pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]372
373<pre><b>size_t ZSTD_estimateCCtxSize(ZSTD_compressionParameters cParams);
374</b><p> Gives the amount of memory allocated for a ZSTD_CCtx given a set of compression parameters.
375 `frameContentSize` is an optional parameter, provide `0` if unknown
376</p></pre><BR>
377
378<pre><b>ZSTD_CCtx* ZSTD_createCCtx_advanced(ZSTD_customMem customMem);
379</b><p> Create a ZSTD compression context using external alloc and free functions
380</p></pre><BR>
381
382<pre><b>size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx);
383</b><p> Gives the amount of memory used by a given ZSTD_CCtx
384</p></pre><BR>
385
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]386<pre><b>typedef enum {
Yann Collet14312d82017-02-23 23:42:12 -0800[diff] [blame]387 ZSTD_p_forceWindow, </b>/* Force back-references to remain < windowSize, even when referencing Dictionary content (default:0) */<b>
388 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]389} ZSTD_CCtxParameter;
390</b></pre><BR>
391<pre><b>size_t ZSTD_setCCtxParameter(ZSTD_CCtx* cctx, ZSTD_CCtxParameter param, unsigned value);
392</b><p> Set advanced parameters, selected through enum ZSTD_CCtxParameter
393 @result : 0, or an error code (which can be tested with ZSTD_isError())
394</p></pre><BR>
395
396<pre><b>ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel);
397</b><p> Create a digested dictionary for compression
398 Dictionary content is simply referenced, and therefore stays in dictBuffer.
399 It is important that dictBuffer outlives CDict, it must remain read accessible throughout the lifetime of CDict
400</p></pre><BR>
401
402<pre><b>ZSTD_CDict* ZSTD_createCDict_advanced(const void* dict, size_t dictSize, unsigned byReference,
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]403 ZSTD_parameters params, ZSTD_customMem customMem);
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]404</b><p> Create a ZSTD_CDict using external alloc and free, and customized compression parameters
405</p></pre><BR>
406
407<pre><b>size_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict);
408</b><p> Gives the amount of memory used by a given ZSTD_sizeof_CDict
409</p></pre><BR>
410
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]411<pre><b>ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
412</b><p> @return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize.
413 `estimatedSrcSize` value is optional, select 0 if not known
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]414</p></pre><BR>
415
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]416<pre><b>ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
417</b><p> same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of sub-component `ZSTD_compressionParameters`.
418 All fields of `ZSTD_frameParameters` are set to default (0)
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]419</p></pre><BR>
420
421<pre><b>size_t ZSTD_checkCParams(ZSTD_compressionParameters params);
422</b><p> Ensure param values remain within authorized range
423</p></pre><BR>
424
425<pre><b>ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize);
426</b><p> optimize params for a given `srcSize` and `dictSize`.
427 both values are optional, select `0` if unknown.
428</p></pre><BR>
429
430<pre><b>size_t ZSTD_compress_advanced (ZSTD_CCtx* ctx,
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]431 void* dst, size_t dstCapacity,
432 const void* src, size_t srcSize,
433 const void* dict,size_t dictSize,
434 ZSTD_parameters params);
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]435</b><p> Same as ZSTD_compress_usingDict(), with fine-tune control of each compression parameter
436</p></pre><BR>
437
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]438<a name="Chapter15"></a><h2>Advanced decompression functions</h2><pre></pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]439
Przemyslaw Skibinski4da53212016-12-07 11:18:40 +0100[diff] [blame]440<pre><b>unsigned ZSTD_isFrame(const void* buffer, size_t size);
441</b><p> Tells if the content of `buffer` starts with a valid Frame Identifier.
442 Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0.
443 Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled.
444 Note 3 : Skippable Frame Identifiers are considered valid.
445</p></pre><BR>
446
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]447<pre><b>size_t ZSTD_estimateDCtxSize(void);
448</b><p> Gives the potential amount of memory allocated to create a ZSTD_DCtx
449</p></pre><BR>
450
451<pre><b>ZSTD_DCtx* ZSTD_createDCtx_advanced(ZSTD_customMem customMem);
452</b><p> Create a ZSTD decompression context using external alloc and free functions
453</p></pre><BR>
454
455<pre><b>size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx);
456</b><p> Gives the amount of memory used by a given ZSTD_DCtx
457</p></pre><BR>
458
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]459<pre><b>ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize);
460</b><p> Create a digested dictionary, ready to start decompression operation without startup delay.
461 Dictionary content is simply referenced, and therefore stays in dictBuffer.
462 It is important that dictBuffer outlives DDict, it must remain read accessible throughout the lifetime of DDict
463</p></pre><BR>
464
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]465<pre><b>ZSTD_DDict* ZSTD_createDDict_advanced(const void* dict, size_t dictSize,
466 unsigned byReference, ZSTD_customMem customMem);
467</b><p> Create a ZSTD_DDict using external alloc and free, optionally by reference
468</p></pre><BR>
469
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]470<pre><b>size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict);
471</b><p> Gives the amount of memory used by a given ZSTD_DDict
472</p></pre><BR>
473
Przemyslaw Skibinski4da53212016-12-07 11:18:40 +0100[diff] [blame]474<pre><b>unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize);
475</b><p> Provides the dictID stored within dictionary.
476 if @return == 0, the dictionary is not conformant with Zstandard specification.
477 It can still be loaded, but as a content-only dictionary.
478</p></pre><BR>
479
480<pre><b>unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict);
481</b><p> Provides the dictID of the dictionary loaded into `ddict`.
482 If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
483 Non-conformant dictionaries can still be loaded, but as content-only dictionaries.
484</p></pre><BR>
485
486<pre><b>unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize);
487</b><p> Provides the dictID required to decompressed the frame stored within `src`.
488 If @return == 0, the dictID could not be decoded.
489 This could for one of the following reasons :
490 - The frame does not require a dictionary to be decoded (most common case).
491 - The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden information.
492 Note : this use case also happens when using a non-conformant dictionary.
493 - `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`).
494 - This is not a Zstandard frame.
495 When identifying the exact failure cause, it's possible to used ZSTD_getFrameParams(), which will provide a more precise error code.
496</p></pre><BR>
497
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]498<a name="Chapter16"></a><h2>Advanced streaming functions</h2><pre></pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]499
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]500<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]501size_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]502size_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>
503size_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]504size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs, const void* dict, size_t dictSize,
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]505 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]506size_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 Collet77575772017-02-22 01:10:43 -0800[diff] [blame]507</pre></b><BR>
Yann Collet4b987ad2017-04-10 17:50:44 -0700[diff] [blame]508<pre><b>size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize);
509</b><p> start a new compression job, using same parameters from previous job.
510 This is typically useful to skip dictionary loading stage, since it will re-use it in-place..
511 Note that zcs must be init at least once before using ZSTD_resetCStream().
512 pledgedSrcSize==0 means "srcSize unknown".
513 If pledgedSrcSize > 0, its value must be correct, as it will be written in header, and controlled at the end.
514 @return : 0, or an error code (which can be tested using ZSTD_isError())
515</p></pre><BR>
516
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]517<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]518ZSTD_DStream* ZSTD_createDStream_advanced(ZSTD_customMem customMem);
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]519size_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]520size_t ZSTD_setDStreamParameter(ZSTD_DStream* zds, ZSTD_DStreamParameter_e paramType, unsigned paramValue);
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]521size_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]522size_t ZSTD_resetDStream(ZSTD_DStream* zds); </b>/**< re-use decompression parameters from previous init; saves dictionary loading */<b>
523size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds);
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]524</pre></b><BR>
525<a name="Chapter17"></a><h2>Buffer-less and synchronous inner streaming functions</h2><pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]526 This is an advanced API, giving full control over buffer management, for users which need direct control over memory.
527 But it's also a complex one, with many restrictions (documented below).
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]528 Prefer using normal streaming API for an easier experience
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]529
530<BR></pre>
531
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]532<a name="Chapter18"></a><h2>Buffer-less streaming compression (synchronous mode)</h2><pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]533 A ZSTD_CCtx object is required to track streaming operations.
534 Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource.
535 ZSTD_CCtx object can be re-used multiple times within successive compression operations.
536
537 Start by initializing a context.
538 Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary compression,
539 or ZSTD_compressBegin_advanced(), for finer parameter control.
540 It's also possible to duplicate a reference context which has already been initialized, using ZSTD_copyCCtx()
541
542 Then, consume your input using ZSTD_compressContinue().
543 There are some important considerations to keep in mind when using this advanced function :
544 - ZSTD_compressContinue() has no internal buffer. It uses externally provided buffer only.
545 - Interface is synchronous : input is consumed entirely and produce 1+ (or more) compressed blocks.
546 - Caller must ensure there is enough space in `dst` to store compressed data under worst case scenario.
547 Worst case evaluation is provided by ZSTD_compressBound().
548 ZSTD_compressContinue() doesn't guarantee recover after a failed compression.
549 - ZSTD_compressContinue() presumes prior input ***is still accessible and unmodified*** (up to maximum distance size, see WindowLog).
550 It remembers all previous contiguous blocks, plus one separated memory segment (which can itself consists of multiple contiguous blocks)
551 - ZSTD_compressContinue() detects that prior input has been overwritten when `src` buffer overlaps.
552 In which case, it will "discard" the relevant memory section from its history.
553
554 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]555 It's possible to use srcSize==0, in which case, it will write a final empty block to end the frame.
556 Without last block mark, frames will be considered unfinished (corrupted) by decoders.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]557
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]558 `ZSTD_CCtx` object can be re-used (ZSTD_compressBegin()) to compress some new frame.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]559<BR></pre>
560
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]561<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]562size_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]563size_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 Collet4b987ad2017-04-10 17:50:44 -0700[diff] [blame]564size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict, unsigned long long pledgedSrcSize); </b>/**< note: fail if cdict==NULL. pledgedSrcSize can be 0, indicating unknown size. For 0 size frames, use compressBegin_advanced */<b>
Yann Collet715b9aa2017-04-18 13:55:53 -0700[diff] [blame^]565size_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>
566size_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]567</pre></b><BR>
568<a name="Chapter19"></a><h2>Buffer-less streaming decompression (synchronous mode)</h2><pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]569 A ZSTD_DCtx object is required to track streaming operations.
570 Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it.
571 A ZSTD_DCtx object can be re-used multiple times.
572
573 First typical operation is to retrieve frame parameters, using ZSTD_getFrameParams().
574 It fills a ZSTD_frameParams structure which provide important information to correctly decode the frame,
575 such as the minimum rolling buffer size to allocate to decompress data (`windowSize`),
576 and the dictionary ID used.
577 (Note : content size is optional, it may not be present. 0 means : content size unknown).
578 Note that these values could be wrong, either because of data malformation, or because an attacker is spoofing deliberate false information.
579 As a consequence, check that values remain within valid application range, especially `windowSize`, before allocation.
580 Each application can set its own limit, depending on local restrictions. For extended interoperability, it is recommended to support at least 8 MB.
581 Frame parameters are extracted from the beginning of the compressed frame.
582 Data fragment must be large enough to ensure successful decoding, typically `ZSTD_frameHeaderSize_max` bytes.
583 @result : 0 : successful decoding, the `ZSTD_frameParams` structure is correctly filled.
584 >0 : `srcSize` is too small, please provide at least @result bytes on next attempt.
585 errorCode, which can be tested using ZSTD_isError().
586
587 Start decompression, with ZSTD_decompressBegin() or ZSTD_decompressBegin_usingDict().
588 Alternatively, you can copy a prepared context, using ZSTD_copyDCtx().
589
590 Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively.
591 ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize' to ZSTD_decompressContinue().
592 ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will fail.
593
594 @result of ZSTD_decompressContinue() is the number of bytes regenerated within 'dst' (necessarily <= dstCapacity).
595 It can be zero, which is not an error; it just means ZSTD_decompressContinue() has decoded some metadata item.
596 It can also be an error code, which can be tested with ZSTD_isError().
597
598 ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize`.
599 They should preferably be located contiguously, prior to current block.
600 Alternatively, a round buffer of sufficient size is also possible. Sufficient size is determined by frame parameters.
601 ZSTD_decompressContinue() is very sensitive to contiguity,
602 if 2 blocks don't follow each other, make sure that either the compressor breaks contiguity at the same place,
603 or that previous contiguous segment is large enough to properly handle maximum back-reference.
604
605 A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero.
606 Context can then be reset to start a new decompression.
607
608 Note : it's possible to know if next input to present is a header or a block, using ZSTD_nextInputType().
609 This information is not required to properly decode a frame.
610
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]611 == Special case : skippable frames
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]612
613 Skippable frames allow integration of user-defined data into a flow of concatenated frames.
614 Skippable frames will be ignored (skipped) by a decompressor. The format of skippable frames is as follows :
615 a) Skippable frame ID - 4 Bytes, Little endian format, any value from 0x184D2A50 to 0x184D2A5F
616 b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits
617 c) Frame Content - any content (User Data) of length equal to Frame Size
618 For skippable frames ZSTD_decompressContinue() always returns 0.
619 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]620 Note : If fparamsPtr->frameContentSize==0, it is ambiguous: the frame might actually be a Zstd encoded frame with no content.
621 For purposes of decompression, it is valid in both cases to skip the frame using
622 ZSTD_findFrameCompressedSize to find its size in bytes.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]623 It also returns Frame Size as fparamsPtr->frameContentSize.
624<BR></pre>
625
626<pre><b>typedef struct {
627 unsigned long long frameContentSize;
628 unsigned windowSize;
629 unsigned dictID;
630 unsigned checksumFlag;
631} ZSTD_frameParams;
632</b></pre><BR>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]633<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]634size_t ZSTD_decompressBegin(ZSTD_DCtx* dctx);
635size_t ZSTD_decompressBegin_usingDict(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
636void ZSTD_copyDCtx(ZSTD_DCtx* dctx, const ZSTD_DCtx* preparedDCtx);
637size_t ZSTD_nextSrcSizeToDecompress(ZSTD_DCtx* dctx);
638size_t ZSTD_decompressContinue(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
639typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e;
640ZSTD_nextInputType_e ZSTD_nextInputType(ZSTD_DCtx* dctx);
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]641</pre></b><BR>
642<a name="Chapter20"></a><h2>Block functions</h2><pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]643 Block functions produce and decode raw zstd blocks, without frame metadata.
644 Frame metadata cost is typically ~18 bytes, which can be non-negligible for very small blocks (< 100 bytes).
645 User will have to take in charge required information to regenerate data, such as compressed and content sizes.
646
647 A few rules to respect :
648 - Compressing and decompressing require a context structure
649 + Use ZSTD_createCCtx() and ZSTD_createDCtx()
650 - It is necessary to init context before starting
Yann Collet715b9aa2017-04-18 13:55:53 -0700[diff] [blame^]651 + compression : any ZSTD_compressBegin*() variant, including with dictionary
652 + decompression : any ZSTD_decompressBegin*() variant, including with dictionary
653 + copyCCtx() and copyDCtx() can be used too
654 - Block size is limited, it must be <= ZSTD_getBlockSizeMax() <= ZSTD_BLOCKSIZE_ABSOLUTEMAX
655 + If input is larger than a block size, it's necessary to split input data into multiple blocks
656 + For inputs larger than a single block size, consider using the regular ZSTD_compress() instead.
657 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]658 - When a block is considered not compressible enough, ZSTD_compressBlock() result will be zero.
659 In which case, nothing is produced into `dst`.
660 + User must test for such outcome and deal directly with uncompressed data
661 + ZSTD_decompressBlock() doesn't accept uncompressed data as input !!!
Yann Collet715b9aa2017-04-18 13:55:53 -0700[diff] [blame^]662 + In case of multiple successive blocks, should some of them be uncompressed,
663 decoder must be informed of their existence in order to follow proper history.
664 Use ZSTD_insertBlock() for such a case.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]665<BR></pre>
666
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]667<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]668size_t ZSTD_compressBlock (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
669size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
670size_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]671</pre></b><BR>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]672</html>
673</body>