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gerrit-public.fairphone.software / platform / external / zstd / dec2b96536893f16923f149d3eab9c8474e8dd4b / . / doc / zstd_manual.html
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Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]4<title>zstd 1.1.4 Manual</title>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]5</head>
6<body>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]7<h1>zstd 1.1.4 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);
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[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.
Nick Terrelld82efd82016-11-02 16:47:53 -0700[diff] [blame]174 Note that compression level is decided during dictionary creation.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]175</p></pre><BR>
176
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]177<pre><b>ZSTD_DDict* ZSTD_createDDict(const void* dictBuffer, size_t dictSize);
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]178</b><p> Create a digested dictionary, ready to start decompression operation without startup delay.
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]179 dictBuffer can be released after DDict creation, as its content is copied inside DDict
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]180</p></pre><BR>
181
182<pre><b>size_t ZSTD_freeDDict(ZSTD_DDict* ddict);
183</b><p> Function frees memory allocated with ZSTD_createDDict()
184</p></pre><BR>
185
186<pre><b>size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx,
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame^]187 void* dst, size_t dstCapacity,
188 const void* src, size_t srcSize,
189 const ZSTD_DDict* ddict);
Nick Terrelld82efd82016-11-02 16:47:53 -0700[diff] [blame]190</b><p> Decompression using a digested Dictionary.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]191 Faster startup than ZSTD_decompress_usingDict(), recommended when same dictionary is used multiple times.
192</p></pre><BR>
193
194<a name="Chapter7"></a><h2>Streaming</h2><pre></pre>
195
196<pre><b>typedef struct ZSTD_inBuffer_s {
197 const void* src; </b>/**< start of input buffer */<b>
198 size_t size; </b>/**< size of input buffer */<b>
199 size_t pos; </b>/**< position where reading stopped. Will be updated. Necessarily 0 <= pos <= size */<b>
200} ZSTD_inBuffer;
201</b></pre><BR>
202<pre><b>typedef struct ZSTD_outBuffer_s {
203 void* dst; </b>/**< start of output buffer */<b>
204 size_t size; </b>/**< size of output buffer */<b>
205 size_t pos; </b>/**< position where writing stopped. Will be updated. Necessarily 0 <= pos <= size */<b>
206} ZSTD_outBuffer;
207</b></pre><BR>
208<a name="Chapter8"></a><h2>Streaming compression - HowTo</h2><pre>
209 A ZSTD_CStream object is required to track streaming operation.
210 Use ZSTD_createCStream() and ZSTD_freeCStream() to create/release resources.
211 ZSTD_CStream objects can be reused multiple times on consecutive compression operations.
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]212 It is recommended to re-use ZSTD_CStream in situations where many streaming operations will be achieved consecutively,
213 since it will play nicer with system's memory, by re-using already allocated memory.
214 Use one separate ZSTD_CStream per thread for parallel execution.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]215
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]216 Start a new compression by initializing ZSTD_CStream.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]217 Use ZSTD_initCStream() to start a new compression operation.
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]218 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]219
220 Use ZSTD_compressStream() repetitively to consume input stream.
221 The function will automatically update both `pos` fields.
222 Note that it may not consume the entire input, in which case `pos < size`,
223 and it's up to the caller to present again remaining data.
224 @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]225 or an error code, which can be tested using ZSTD_isError().
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]226 Note 1 : it's just a hint, to help latency a little, any other value will work fine.
227 Note 2 : size hint is guaranteed to be <= ZSTD_CStreamInSize()
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]228
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]229 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]230 `output->pos` will be updated.
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]231 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]232 @return : nb of bytes still present within internal buffer (0 if it's empty)
233 or an error code, which can be tested using ZSTD_isError().
234
235 ZSTD_endStream() instructs to finish a frame.
236 It will perform a flush and write frame epilogue.
237 The epilogue is required for decoders to consider a frame completed.
238 Similar to ZSTD_flushStream(), it may not be able to flush the full content if `output->size` is too small.
239 In which case, call again ZSTD_endStream() to complete the flush.
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]240 @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]241 or an error code, which can be tested using ZSTD_isError().
242
243
244<BR></pre>
245
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame^]246<h3>ZSTD_CStream management functions</h3><pre></pre><b><pre>ZSTD_CStream* ZSTD_createCStream(void);
247size_t ZSTD_freeCStream(ZSTD_CStream* zcs);
248</pre></b><BR>
249<h3>Streaming compression functions</h3><pre></pre><b><pre>size_t ZSTD_initCStream(ZSTD_CStream* zcs, int compressionLevel);
250size_t ZSTD_compressStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
251size_t ZSTD_flushStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
252size_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
253</pre></b><BR>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]254<pre><b>size_t ZSTD_CStreamInSize(void); </b>/**< recommended size for input buffer */<b>
255</b></pre><BR>
256<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>
257</b></pre><BR>
258<a name="Chapter9"></a><h2>Streaming decompression - HowTo</h2><pre>
259 A ZSTD_DStream object is required to track streaming operations.
260 Use ZSTD_createDStream() and ZSTD_freeDStream() to create/release resources.
261 ZSTD_DStream objects can be re-used multiple times.
262
263 Use ZSTD_initDStream() to start a new decompression operation,
264 or ZSTD_initDStream_usingDict() if decompression requires a dictionary.
265 @return : recommended first input size
266
267 Use ZSTD_decompressStream() repetitively to consume your input.
268 The function will update both `pos` fields.
269 If `input.pos < input.size`, some input has not been consumed.
270 It's up to the caller to present again remaining data.
271 If `output.pos < output.size`, decoder has flushed everything it could.
272 @return : 0 when a frame is completely decoded and fully flushed,
273 an error code, which can be tested using ZSTD_isError(),
Przemyslaw Skibinski4da53212016-12-07 11:18:40 +0100[diff] [blame]274 any other value > 0, which means there is still some decoding to do to complete current frame.
275 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]276
277<BR></pre>
278
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame^]279<h3>ZSTD_DStream management functions</h3><pre></pre><b><pre>ZSTD_DStream* ZSTD_createDStream(void);
280size_t ZSTD_freeDStream(ZSTD_DStream* zds);
281</pre></b><BR>
282<h3>Streaming decompression functions</h3><pre></pre><b><pre>size_t ZSTD_initDStream(ZSTD_DStream* zds);
283size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
284</pre></b><BR>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]285<pre><b>size_t ZSTD_DStreamInSize(void); </b>/*!< recommended size for input buffer */<b>
286</b></pre><BR>
287<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>
288</b></pre><BR>
289<a name="Chapter10"></a><h2>START OF ADVANCED AND EXPERIMENTAL FUNCTIONS</h2><pre> The definitions in this section are considered experimental.
290 They should never be used with a dynamic library, as they may change in the future.
291 They are provided for advanced usages.
292 Use them only in association with static linking.
293
294<BR></pre>
295
296<a name="Chapter11"></a><h2>Advanced types</h2><pre></pre>
297
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]298<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]299</b></pre><BR>
300<pre><b>typedef struct {
301 unsigned windowLog; </b>/**< largest match distance : larger == more compression, more memory needed during decompression */<b>
302 unsigned chainLog; </b>/**< fully searched segment : larger == more compression, slower, more memory (useless for fast) */<b>
303 unsigned hashLog; </b>/**< dispatch table : larger == faster, more memory */<b>
304 unsigned searchLog; </b>/**< nb of searches : larger == more compression, slower */<b>
305 unsigned searchLength; </b>/**< match length searched : larger == faster decompression, sometimes less compression */<b>
306 unsigned targetLength; </b>/**< acceptable match size for optimal parser (only) : larger == more compression, slower */<b>
307 ZSTD_strategy strategy;
308} ZSTD_compressionParameters;
309</b></pre><BR>
310<pre><b>typedef struct {
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]311 unsigned contentSizeFlag; </b>/**< 1: content size will be in frame header (when known) */<b>
312 unsigned checksumFlag; </b>/**< 1: generate a 32-bits checksum at end of frame, for error detection */<b>
313 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]314} ZSTD_frameParameters;
315</b></pre><BR>
316<pre><b>typedef struct {
317 ZSTD_compressionParameters cParams;
318 ZSTD_frameParameters fParams;
319} ZSTD_parameters;
320</b></pre><BR>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]321<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]322typedef void (*ZSTD_freeFunction) (void* opaque, void* address);
323typedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; void* opaque; } ZSTD_customMem;
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]324</pre></b><BR>
325<a name="Chapter12"></a><h2>Compressed size functions</h2><pre></pre>
326
Yann Collet831b4892017-02-23 23:09:10 -0800[diff] [blame]327<pre><b>size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize);
328</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]329 `srcSize` must be at least as large as the frame
330 @return : the compressed size of the frame pointed to by `src`, suitable to pass to
331 `ZSTD_decompress` or similar, or an error code if given invalid input.
332</p></pre><BR>
333
334<a name="Chapter13"></a><h2>Decompressed size functions</h2><pre></pre>
335
336<pre><b>unsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize);
337</b><p> `src` should point to the start of a ZSTD encoded frame
338 `srcSize` must be at least as large as the frame header. A value greater than or equal
339 to `ZSTD_frameHeaderSize_max` is guaranteed to be large enough in all cases.
340 @return : decompressed size of the frame pointed to be `src` if known, otherwise
341 - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined
Yann Collet831b4892017-02-23 23:09:10 -0800[diff] [blame]342 - 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]343</p></pre><BR>
344
345<pre><b>unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize);
346</b><p> `src` should point the start of a series of ZSTD encoded and/or skippable frames
347 `srcSize` must be the _exact_ size of this series
348 (i.e. there should be a frame boundary exactly `srcSize` bytes after `src`)
349 @return : the decompressed size of all data in the contained frames, as a 64-bit value _if known_
350 - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN
351 - if an error occurred: ZSTD_CONTENTSIZE_ERROR
352
353 note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode.
354 When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
355 In which case, it's necessary to use streaming mode to decompress data.
356 Optionally, application can still use ZSTD_decompress() while relying on implied limits.
357 (For example, data may be necessarily cut into blocks <= 16 KB).
358 note 2 : decompressed size is always present when compression is done with ZSTD_compress()
359 note 3 : decompressed size can be very large (64-bits value),
360 potentially larger than what local system can handle as a single memory segment.
361 In which case, it's necessary to use streaming mode to decompress data.
362 note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified.
363 Always ensure result fits within application's authorized limits.
364 Each application can set its own limits.
365 note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to
366 read each contained frame header. This is efficient as most of the data is skipped,
367 however it does mean that all frame data must be present and valid.
368</p></pre><BR>
369
370<a name="Chapter14"></a><h2>Advanced compression functions</h2><pre></pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]371
372<pre><b>size_t ZSTD_estimateCCtxSize(ZSTD_compressionParameters cParams);
373</b><p> Gives the amount of memory allocated for a ZSTD_CCtx given a set of compression parameters.
374 `frameContentSize` is an optional parameter, provide `0` if unknown
375</p></pre><BR>
376
377<pre><b>ZSTD_CCtx* ZSTD_createCCtx_advanced(ZSTD_customMem customMem);
378</b><p> Create a ZSTD compression context using external alloc and free functions
379</p></pre><BR>
380
381<pre><b>size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx);
382</b><p> Gives the amount of memory used by a given ZSTD_CCtx
383</p></pre><BR>
384
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]385<pre><b>typedef enum {
Yann Collet14312d82017-02-23 23:42:12 -0800[diff] [blame]386 ZSTD_p_forceWindow, </b>/* Force back-references to remain < windowSize, even when referencing Dictionary content (default:0) */<b>
387 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]388} ZSTD_CCtxParameter;
389</b></pre><BR>
390<pre><b>size_t ZSTD_setCCtxParameter(ZSTD_CCtx* cctx, ZSTD_CCtxParameter param, unsigned value);
391</b><p> Set advanced parameters, selected through enum ZSTD_CCtxParameter
392 @result : 0, or an error code (which can be tested with ZSTD_isError())
393</p></pre><BR>
394
395<pre><b>ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel);
396</b><p> Create a digested dictionary for compression
397 Dictionary content is simply referenced, and therefore stays in dictBuffer.
398 It is important that dictBuffer outlives CDict, it must remain read accessible throughout the lifetime of CDict
399</p></pre><BR>
400
401<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^]402 ZSTD_parameters params, ZSTD_customMem customMem);
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]403</b><p> Create a ZSTD_CDict using external alloc and free, and customized compression parameters
404</p></pre><BR>
405
406<pre><b>size_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict);
407</b><p> Gives the amount of memory used by a given ZSTD_sizeof_CDict
408</p></pre><BR>
409
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]410<pre><b>ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
411</b><p> @return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize.
412 `estimatedSrcSize` value is optional, select 0 if not known
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]413</p></pre><BR>
414
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]415<pre><b>ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
416</b><p> same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of sub-component `ZSTD_compressionParameters`.
417 All fields of `ZSTD_frameParameters` are set to default (0)
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]418</p></pre><BR>
419
420<pre><b>size_t ZSTD_checkCParams(ZSTD_compressionParameters params);
421</b><p> Ensure param values remain within authorized range
422</p></pre><BR>
423
424<pre><b>ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize);
425</b><p> optimize params for a given `srcSize` and `dictSize`.
426 both values are optional, select `0` if unknown.
427</p></pre><BR>
428
429<pre><b>size_t ZSTD_compress_advanced (ZSTD_CCtx* ctx,
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame^]430 void* dst, size_t dstCapacity,
431 const void* src, size_t srcSize,
432 const void* dict,size_t dictSize,
433 ZSTD_parameters params);
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]434</b><p> Same as ZSTD_compress_usingDict(), with fine-tune control of each compression parameter
435</p></pre><BR>
436
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]437<a name="Chapter15"></a><h2>Advanced decompression functions</h2><pre></pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]438
Przemyslaw Skibinski4da53212016-12-07 11:18:40 +0100[diff] [blame]439<pre><b>unsigned ZSTD_isFrame(const void* buffer, size_t size);
440</b><p> Tells if the content of `buffer` starts with a valid Frame Identifier.
441 Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0.
442 Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled.
443 Note 3 : Skippable Frame Identifiers are considered valid.
444</p></pre><BR>
445
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]446<pre><b>size_t ZSTD_estimateDCtxSize(void);
447</b><p> Gives the potential amount of memory allocated to create a ZSTD_DCtx
448</p></pre><BR>
449
450<pre><b>ZSTD_DCtx* ZSTD_createDCtx_advanced(ZSTD_customMem customMem);
451</b><p> Create a ZSTD decompression context using external alloc and free functions
452</p></pre><BR>
453
454<pre><b>size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx);
455</b><p> Gives the amount of memory used by a given ZSTD_DCtx
456</p></pre><BR>
457
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]458<pre><b>ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize);
459</b><p> Create a digested dictionary, ready to start decompression operation without startup delay.
460 Dictionary content is simply referenced, and therefore stays in dictBuffer.
461 It is important that dictBuffer outlives DDict, it must remain read accessible throughout the lifetime of DDict
462</p></pre><BR>
463
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame^]464<pre><b>ZSTD_DDict* ZSTD_createDDict_advanced(const void* dict, size_t dictSize,
465 unsigned byReference, ZSTD_customMem customMem);
466</b><p> Create a ZSTD_DDict using external alloc and free, optionally by reference
467</p></pre><BR>
468
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]469<pre><b>size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict);
470</b><p> Gives the amount of memory used by a given ZSTD_DDict
471</p></pre><BR>
472
Przemyslaw Skibinski4da53212016-12-07 11:18:40 +0100[diff] [blame]473<pre><b>unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize);
474</b><p> Provides the dictID stored within dictionary.
475 if @return == 0, the dictionary is not conformant with Zstandard specification.
476 It can still be loaded, but as a content-only dictionary.
477</p></pre><BR>
478
479<pre><b>unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict);
480</b><p> Provides the dictID of the dictionary loaded into `ddict`.
481 If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
482 Non-conformant dictionaries can still be loaded, but as content-only dictionaries.
483</p></pre><BR>
484
485<pre><b>unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize);
486</b><p> Provides the dictID required to decompressed the frame stored within `src`.
487 If @return == 0, the dictID could not be decoded.
488 This could for one of the following reasons :
489 - The frame does not require a dictionary to be decoded (most common case).
490 - The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden information.
491 Note : this use case also happens when using a non-conformant dictionary.
492 - `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`).
493 - This is not a Zstandard frame.
494 When identifying the exact failure cause, it's possible to used ZSTD_getFrameParams(), which will provide a more precise error code.
495</p></pre><BR>
496
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]497<a name="Chapter16"></a><h2>Advanced streaming functions</h2><pre></pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]498
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]499<h3>Advanced Streaming compression functions</h3><pre></pre><b><pre>ZSTD_CStream* ZSTD_createCStream_advanced(ZSTD_customMem customMem);
500size_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>
501size_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]502size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs, const void* dict, size_t dictSize,
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]503 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]504size_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]505size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize); </b>/**< re-use compression parameters from previous init; skip dictionary loading stage; zcs must be init at least once before. note: pledgedSrcSize must be correct, a size of 0 means unknown. for a frame size of 0 use initCStream_advanced */<b>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]506size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs);
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]507</pre></b><BR>
508<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]509ZSTD_DStream* ZSTD_createDStream_advanced(ZSTD_customMem customMem);
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]510size_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]511size_t ZSTD_setDStreamParameter(ZSTD_DStream* zds, ZSTD_DStreamParameter_e paramType, unsigned paramValue);
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]512size_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]513size_t ZSTD_resetDStream(ZSTD_DStream* zds); </b>/**< re-use decompression parameters from previous init; saves dictionary loading */<b>
514size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds);
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]515</pre></b><BR>
516<a name="Chapter17"></a><h2>Buffer-less and synchronous inner streaming functions</h2><pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]517 This is an advanced API, giving full control over buffer management, for users which need direct control over memory.
518 But it's also a complex one, with many restrictions (documented below).
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]519 Prefer using normal streaming API for an easier experience
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]520
521<BR></pre>
522
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]523<a name="Chapter18"></a><h2>Buffer-less streaming compression (synchronous mode)</h2><pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]524 A ZSTD_CCtx object is required to track streaming operations.
525 Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource.
526 ZSTD_CCtx object can be re-used multiple times within successive compression operations.
527
528 Start by initializing a context.
529 Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary compression,
530 or ZSTD_compressBegin_advanced(), for finer parameter control.
531 It's also possible to duplicate a reference context which has already been initialized, using ZSTD_copyCCtx()
532
533 Then, consume your input using ZSTD_compressContinue().
534 There are some important considerations to keep in mind when using this advanced function :
535 - ZSTD_compressContinue() has no internal buffer. It uses externally provided buffer only.
536 - Interface is synchronous : input is consumed entirely and produce 1+ (or more) compressed blocks.
537 - Caller must ensure there is enough space in `dst` to store compressed data under worst case scenario.
538 Worst case evaluation is provided by ZSTD_compressBound().
539 ZSTD_compressContinue() doesn't guarantee recover after a failed compression.
540 - ZSTD_compressContinue() presumes prior input ***is still accessible and unmodified*** (up to maximum distance size, see WindowLog).
541 It remembers all previous contiguous blocks, plus one separated memory segment (which can itself consists of multiple contiguous blocks)
542 - ZSTD_compressContinue() detects that prior input has been overwritten when `src` buffer overlaps.
543 In which case, it will "discard" the relevant memory section from its history.
544
545 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]546 It's possible to use srcSize==0, in which case, it will write a final empty block to end the frame.
547 Without last block mark, frames will be considered unfinished (corrupted) by decoders.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]548
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]549 `ZSTD_CCtx` object can be re-used (ZSTD_compressBegin()) to compress some new frame.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]550<BR></pre>
551
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]552<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]553size_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]554size_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>
555size_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>
556size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict, 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>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]557size_t ZSTD_compressContinue(ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
558size_t ZSTD_compressEnd(ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]559</pre></b><BR>
560<a name="Chapter19"></a><h2>Buffer-less streaming decompression (synchronous mode)</h2><pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]561 A ZSTD_DCtx object is required to track streaming operations.
562 Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it.
563 A ZSTD_DCtx object can be re-used multiple times.
564
565 First typical operation is to retrieve frame parameters, using ZSTD_getFrameParams().
566 It fills a ZSTD_frameParams structure which provide important information to correctly decode the frame,
567 such as the minimum rolling buffer size to allocate to decompress data (`windowSize`),
568 and the dictionary ID used.
569 (Note : content size is optional, it may not be present. 0 means : content size unknown).
570 Note that these values could be wrong, either because of data malformation, or because an attacker is spoofing deliberate false information.
571 As a consequence, check that values remain within valid application range, especially `windowSize`, before allocation.
572 Each application can set its own limit, depending on local restrictions. For extended interoperability, it is recommended to support at least 8 MB.
573 Frame parameters are extracted from the beginning of the compressed frame.
574 Data fragment must be large enough to ensure successful decoding, typically `ZSTD_frameHeaderSize_max` bytes.
575 @result : 0 : successful decoding, the `ZSTD_frameParams` structure is correctly filled.
576 >0 : `srcSize` is too small, please provide at least @result bytes on next attempt.
577 errorCode, which can be tested using ZSTD_isError().
578
579 Start decompression, with ZSTD_decompressBegin() or ZSTD_decompressBegin_usingDict().
580 Alternatively, you can copy a prepared context, using ZSTD_copyDCtx().
581
582 Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively.
583 ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize' to ZSTD_decompressContinue().
584 ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will fail.
585
586 @result of ZSTD_decompressContinue() is the number of bytes regenerated within 'dst' (necessarily <= dstCapacity).
587 It can be zero, which is not an error; it just means ZSTD_decompressContinue() has decoded some metadata item.
588 It can also be an error code, which can be tested with ZSTD_isError().
589
590 ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize`.
591 They should preferably be located contiguously, prior to current block.
592 Alternatively, a round buffer of sufficient size is also possible. Sufficient size is determined by frame parameters.
593 ZSTD_decompressContinue() is very sensitive to contiguity,
594 if 2 blocks don't follow each other, make sure that either the compressor breaks contiguity at the same place,
595 or that previous contiguous segment is large enough to properly handle maximum back-reference.
596
597 A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero.
598 Context can then be reset to start a new decompression.
599
600 Note : it's possible to know if next input to present is a header or a block, using ZSTD_nextInputType().
601 This information is not required to properly decode a frame.
602
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]603 == Special case : skippable frames
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]604
605 Skippable frames allow integration of user-defined data into a flow of concatenated frames.
606 Skippable frames will be ignored (skipped) by a decompressor. The format of skippable frames is as follows :
607 a) Skippable frame ID - 4 Bytes, Little endian format, any value from 0x184D2A50 to 0x184D2A5F
608 b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits
609 c) Frame Content - any content (User Data) of length equal to Frame Size
610 For skippable frames ZSTD_decompressContinue() always returns 0.
611 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]612 Note : If fparamsPtr->frameContentSize==0, it is ambiguous: the frame might actually be a Zstd encoded frame with no content.
613 For purposes of decompression, it is valid in both cases to skip the frame using
614 ZSTD_findFrameCompressedSize to find its size in bytes.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]615 It also returns Frame Size as fparamsPtr->frameContentSize.
616<BR></pre>
617
618<pre><b>typedef struct {
619 unsigned long long frameContentSize;
620 unsigned windowSize;
621 unsigned dictID;
622 unsigned checksumFlag;
623} ZSTD_frameParams;
624</b></pre><BR>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]625<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]626size_t ZSTD_decompressBegin(ZSTD_DCtx* dctx);
627size_t ZSTD_decompressBegin_usingDict(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
628void ZSTD_copyDCtx(ZSTD_DCtx* dctx, const ZSTD_DCtx* preparedDCtx);
629size_t ZSTD_nextSrcSizeToDecompress(ZSTD_DCtx* dctx);
630size_t ZSTD_decompressContinue(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
631typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e;
632ZSTD_nextInputType_e ZSTD_nextInputType(ZSTD_DCtx* dctx);
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]633</pre></b><BR>
634<a name="Chapter20"></a><h2>Block functions</h2><pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]635 Block functions produce and decode raw zstd blocks, without frame metadata.
636 Frame metadata cost is typically ~18 bytes, which can be non-negligible for very small blocks (< 100 bytes).
637 User will have to take in charge required information to regenerate data, such as compressed and content sizes.
638
639 A few rules to respect :
640 - Compressing and decompressing require a context structure
641 + Use ZSTD_createCCtx() and ZSTD_createDCtx()
642 - It is necessary to init context before starting
643 + compression : ZSTD_compressBegin()
644 + decompression : ZSTD_decompressBegin()
645 + variants _usingDict() are also allowed
646 + copyCCtx() and copyDCtx() work too
647 - Block size is limited, it must be <= ZSTD_getBlockSizeMax()
648 + If you need to compress more, cut data into multiple blocks
649 + Consider using the regular ZSTD_compress() instead, as frame metadata costs become negligible when source size is large.
650 - When a block is considered not compressible enough, ZSTD_compressBlock() result will be zero.
651 In which case, nothing is produced into `dst`.
652 + User must test for such outcome and deal directly with uncompressed data
653 + ZSTD_decompressBlock() doesn't accept uncompressed data as input !!!
654 + In case of multiple successive blocks, decoder must be informed of uncompressed block existence to follow proper history.
655 Use ZSTD_insertBlock() in such a case.
656<BR></pre>
657
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]658<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]659size_t ZSTD_compressBlock (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
660size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
661size_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]662</pre></b><BR>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]663</html>
664</body>