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gerrit-public.fairphone.software / platform / external / zstd / b0739bcf8f90ce2fbb8944293997f338d5f1db89 / . / doc / zstd_manual.html
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Yann Colletfa8dadb2017-05-08 18:24:16 -0700[diff] [blame]4<title>zstd 1.3.0 Manual</title>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]5</head>
6<body>
Yann Colletfa8dadb2017-05-08 18:24:16 -0700[diff] [blame]7<h1>zstd 1.3.0 Manual</h1>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]8<hr>
9<a name="Contents"></a><h2>Contents</h2>
10<ol>
11<li><a href="#Chapter1">Introduction</a></li>
12<li><a href="#Chapter2">Version</a></li>
13<li><a href="#Chapter3">Simple API</a></li>
14<li><a href="#Chapter4">Explicit memory management</a></li>
15<li><a href="#Chapter5">Simple dictionary API</a></li>
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 Collet5a36c062017-05-09 15:11:30 -0700[diff] [blame]22<li><a href="#Chapter12">Frame size functions</a></li>
23<li><a href="#Chapter13">Context memory usage</a></li>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]24<li><a href="#Chapter14">Advanced compression functions</a></li>
25<li><a href="#Chapter15">Advanced decompression functions</a></li>
26<li><a href="#Chapter16">Advanced streaming functions</a></li>
27<li><a href="#Chapter17">Buffer-less and synchronous inner streaming functions</a></li>
28<li><a href="#Chapter18">Buffer-less streaming compression (synchronous mode)</a></li>
29<li><a href="#Chapter19">Buffer-less streaming decompression (synchronous mode)</a></li>
30<li><a href="#Chapter20">Block functions</a></li>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]31</ol>
32<hr>
33<a name="Chapter1"></a><h2>Introduction</h2><pre>
Yann Colleta5ffe3d2017-05-12 16:29:19 -0700[diff] [blame]34 zstd, short for Zstandard, is a fast lossless compression algorithm,
35 targeting real-time compression scenarios at zlib-level and better compression ratios.
36 The zstd compression library provides in-memory compression and decompression functions.
37 The library supports compression levels from 1 up to ZSTD_maxCLevel() which is currently 22.
Yann Collet831b4892017-02-23 23:09:10 -0800[diff] [blame]38 Levels >= 20, labeled `--ultra`, should be used with caution, as they require more memory.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]39 Compression can be done in:
40 - a single step (described as Simple API)
41 - a single step, reusing a context (described as Explicit memory management)
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]42 - unbounded multiple steps (described as Streaming compression)
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]43 The compression ratio achievable on small data can be highly improved using compression with a dictionary in:
44 - a single step (described as Simple dictionary API)
45 - a single step, reusing a dictionary (described as Fast dictionary API)
46
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]47 Advanced experimental functions can be accessed using #define ZSTD_STATIC_LINKING_ONLY before including zstd.h.
48 These APIs shall never be used with a dynamic library.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]49 They are not "stable", their definition may change in the future. Only static linking is allowed.
50<BR></pre>
51
52<a name="Chapter2"></a><h2>Version</h2><pre></pre>
53
Yann Collet6d4fef32017-05-17 18:36:15 -0700[diff] [blame]54<pre><b>unsigned ZSTD_versionNumber(void); </b>/**< to be used when checking dll version */<b>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]55</b></pre><BR>
56<a name="Chapter3"></a><h2>Simple API</h2><pre></pre>
57
58<pre><b>size_t ZSTD_compress( void* dst, size_t dstCapacity,
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]59 const void* src, size_t srcSize,
60 int compressionLevel);
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]61</b><p> Compresses `src` content as a single zstd compressed frame into already allocated `dst`.
62 Hint : compression runs faster if `dstCapacity` >= `ZSTD_compressBound(srcSize)`.
63 @return : compressed size written into `dst` (<= `dstCapacity),
64 or an error code if it fails (which can be tested using ZSTD_isError()).
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]65</p></pre><BR>
66
67<pre><b>size_t ZSTD_decompress( void* dst, size_t dstCapacity,
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]68 const void* src, size_t compressedSize);
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]69</b><p> `compressedSize` : must be the _exact_ size of some number of compressed and/or skippable frames.
70 `dstCapacity` is an upper bound of originalSize.
71 If user cannot imply a maximum upper bound, it's better to use streaming mode to decompress data.
72 @return : the number of bytes decompressed into `dst` (<= `dstCapacity`),
73 or an errorCode if it fails (which can be tested using ZSTD_isError()).
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]74</p></pre><BR>
75
76<pre><b>unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize);
Yann Colleta5ffe3d2017-05-12 16:29:19 -0700[diff] [blame]77</b><p> NOTE: This function is planned to be obsolete, in favor of ZSTD_getFrameContentSize().
78 ZSTD_getFrameContentSize() works the same way,
79 returning the decompressed size of a single frame,
80 but distinguishes empty frames from frames with an unknown size, or errors.
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]81
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]82 'src' is the start of a zstd compressed frame.
83 @return : content size to be decompressed, as a 64-bits value _if known_, 0 otherwise.
Yann Colleta5ffe3d2017-05-12 16:29:19 -0700[diff] [blame]84 note 1 : decompressed size is an optional field, it may not be present, typically in streaming mode.
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]85 When `return==0`, data to decompress could be any size.
86 In which case, it's necessary to use streaming mode to decompress data.
Yann Colleta5ffe3d2017-05-12 16:29:19 -0700[diff] [blame]87 Optionally, application can use ZSTD_decompress() while relying on implied limits.
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]88 (For example, data may be necessarily cut into blocks <= 16 KB).
89 note 2 : decompressed size is always present when compression is done with ZSTD_compress()
90 note 3 : decompressed size can be very large (64-bits value),
91 potentially larger than what local system can handle as a single memory segment.
92 In which case, it's necessary to use streaming mode to decompress data.
93 note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified.
94 Always ensure result fits within application's authorized limits.
95 Each application can set its own limits.
96 note 5 : when `return==0`, if precise failure cause is needed, use ZSTD_getFrameParams() to know more.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]97</p></pre><BR>
98
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]99<h3>Helper functions</h3><pre></pre><b><pre>int ZSTD_maxCLevel(void); </b>/*!< maximum compression level available */<b>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]100size_t ZSTD_compressBound(size_t srcSize); </b>/*!< maximum compressed size in worst case scenario */<b>
101unsigned ZSTD_isError(size_t code); </b>/*!< tells if a `size_t` function result is an error code */<b>
102const char* ZSTD_getErrorName(size_t code); </b>/*!< provides readable string from an error code */<b>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]103</pre></b><BR>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]104<a name="Chapter4"></a><h2>Explicit memory management</h2><pre></pre>
105
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]106<h3>Compression context</h3><pre> When compressing many times,
107 it is recommended to allocate a context just once, and re-use it for each successive compression operation.
108 This will make workload friendlier for system's memory.
109 Use one context per thread for parallel execution in multi-threaded environments.
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]110</pre><b><pre>typedef struct ZSTD_CCtx_s ZSTD_CCtx;
111ZSTD_CCtx* ZSTD_createCCtx(void);
112size_t ZSTD_freeCCtx(ZSTD_CCtx* cctx);
113</pre></b><BR>
Yann Colleta5ffe3d2017-05-12 16:29:19 -0700[diff] [blame]114<pre><b>size_t ZSTD_compressCCtx(ZSTD_CCtx* ctx,
115 void* dst, size_t dstCapacity,
116 const void* src, size_t srcSize,
117 int compressionLevel);
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]118</b><p> Same as ZSTD_compress(), requires an allocated ZSTD_CCtx (see ZSTD_createCCtx()).
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]119</p></pre><BR>
120
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]121<h3>Decompression context</h3><pre> When decompressing many times,
Yann Colleta5ffe3d2017-05-12 16:29:19 -0700[diff] [blame]122 it is recommended to allocate a context only once,
123 and re-use it for each successive compression operation.
Yann Collete42afbc2017-04-26 11:39:35 -0700[diff] [blame]124 This will make workload friendlier for system's memory.
Yann Colleta5ffe3d2017-05-12 16:29:19 -0700[diff] [blame]125 Use one context per thread for parallel execution.
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]126</pre><b><pre>typedef struct ZSTD_DCtx_s ZSTD_DCtx;
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]127ZSTD_DCtx* ZSTD_createDCtx(void);
128size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx);
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]129</pre></b><BR>
Yann Colleta5ffe3d2017-05-12 16:29:19 -0700[diff] [blame]130<pre><b>size_t ZSTD_decompressDCtx(ZSTD_DCtx* ctx,
131 void* dst, size_t dstCapacity,
132 const void* src, size_t srcSize);
133</b><p> Same as ZSTD_decompress(), requires an allocated ZSTD_DCtx (see ZSTD_createDCtx())
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]134</p></pre><BR>
135
136<a name="Chapter5"></a><h2>Simple dictionary API</h2><pre></pre>
137
138<pre><b>size_t ZSTD_compress_usingDict(ZSTD_CCtx* ctx,
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]139 void* dst, size_t dstCapacity,
140 const void* src, size_t srcSize,
141 const void* dict,size_t dictSize,
142 int compressionLevel);
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]143</b><p> Compression using a predefined Dictionary (see dictBuilder/zdict.h).
Nick Terrelld82efd82016-11-02 16:47:53 -0700[diff] [blame]144 Note : This function loads the dictionary, resulting in significant startup delay.
145 Note : When `dict == NULL || dictSize < 8` no dictionary is used.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]146</p></pre><BR>
147
148<pre><b>size_t ZSTD_decompress_usingDict(ZSTD_DCtx* dctx,
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]149 void* dst, size_t dstCapacity,
150 const void* src, size_t srcSize,
151 const void* dict,size_t dictSize);
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]152</b><p> Decompression using a predefined Dictionary (see dictBuilder/zdict.h).
153 Dictionary must be identical to the one used during compression.
Nick Terrelld82efd82016-11-02 16:47:53 -0700[diff] [blame]154 Note : This function loads the dictionary, resulting in significant startup delay.
155 Note : When `dict == NULL || dictSize < 8` no dictionary is used.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]156</p></pre><BR>
157
158<a name="Chapter6"></a><h2>Fast dictionary API</h2><pre></pre>
159
Yann Colleta5ffe3d2017-05-12 16:29:19 -0700[diff] [blame]160<pre><b>ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize,
161 int compressionLevel);
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]162</b><p> When compressing multiple messages / blocks with the same dictionary, it's recommended to load it just once.
163 ZSTD_createCDict() will create a digested dictionary, ready to start future compression operations without startup delay.
164 ZSTD_CDict can be created once and used by multiple threads concurrently, as its usage is read-only.
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]165 `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]166</p></pre><BR>
167
168<pre><b>size_t ZSTD_freeCDict(ZSTD_CDict* CDict);
Nick Terrelld82efd82016-11-02 16:47:53 -0700[diff] [blame]169</b><p> Function frees memory allocated by ZSTD_createCDict().
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]170</p></pre><BR>
171
172<pre><b>size_t ZSTD_compress_usingCDict(ZSTD_CCtx* cctx,
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]173 void* dst, size_t dstCapacity,
174 const void* src, size_t srcSize,
175 const ZSTD_CDict* cdict);
Yann Collet715b9aa2017-04-18 13:55:53 -0700[diff] [blame]176</b><p> Compression using a digested Dictionary.
177 Faster startup than ZSTD_compress_usingDict(), recommended when same dictionary is used multiple times.
178 Note that compression level is decided during dictionary creation.
179 Frame parameters are hardcoded (dictID=yes, contentSize=yes, checksum=no)
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]180</p></pre><BR>
181
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]182<pre><b>ZSTD_DDict* ZSTD_createDDict(const void* dictBuffer, size_t dictSize);
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]183</b><p> Create a digested dictionary, ready to start decompression operation without startup delay.
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]184 dictBuffer can be released after DDict creation, as its content is copied inside DDict
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]185</p></pre><BR>
186
187<pre><b>size_t ZSTD_freeDDict(ZSTD_DDict* ddict);
188</b><p> Function frees memory allocated with ZSTD_createDDict()
189</p></pre><BR>
190
191<pre><b>size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx,
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]192 void* dst, size_t dstCapacity,
193 const void* src, size_t srcSize,
194 const ZSTD_DDict* ddict);
Nick Terrelld82efd82016-11-02 16:47:53 -0700[diff] [blame]195</b><p> Decompression using a digested Dictionary.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]196 Faster startup than ZSTD_decompress_usingDict(), recommended when same dictionary is used multiple times.
197</p></pre><BR>
198
199<a name="Chapter7"></a><h2>Streaming</h2><pre></pre>
200
201<pre><b>typedef struct ZSTD_inBuffer_s {
202 const void* src; </b>/**< start of input buffer */<b>
203 size_t size; </b>/**< size of input buffer */<b>
204 size_t pos; </b>/**< position where reading stopped. Will be updated. Necessarily 0 <= pos <= size */<b>
205} ZSTD_inBuffer;
206</b></pre><BR>
207<pre><b>typedef struct ZSTD_outBuffer_s {
208 void* dst; </b>/**< start of output buffer */<b>
209 size_t size; </b>/**< size of output buffer */<b>
210 size_t pos; </b>/**< position where writing stopped. Will be updated. Necessarily 0 <= pos <= size */<b>
211} ZSTD_outBuffer;
212</b></pre><BR>
213<a name="Chapter8"></a><h2>Streaming compression - HowTo</h2><pre>
214 A ZSTD_CStream object is required to track streaming operation.
215 Use ZSTD_createCStream() and ZSTD_freeCStream() to create/release resources.
216 ZSTD_CStream objects can be reused multiple times on consecutive compression operations.
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]217 It is recommended to re-use ZSTD_CStream in situations where many streaming operations will be achieved consecutively,
218 since it will play nicer with system's memory, by re-using already allocated memory.
219 Use one separate ZSTD_CStream per thread for parallel execution.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]220
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]221 Start a new compression by initializing ZSTD_CStream.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]222 Use ZSTD_initCStream() to start a new compression operation.
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]223 Use ZSTD_initCStream_usingDict() or ZSTD_initCStream_usingCDict() for a compression which requires a dictionary (experimental section)
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]224
225 Use ZSTD_compressStream() repetitively to consume input stream.
226 The function will automatically update both `pos` fields.
227 Note that it may not consume the entire input, in which case `pos < size`,
228 and it's up to the caller to present again remaining data.
229 @return : a size hint, preferred nb of bytes to use as input for next function call
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]230 or an error code, which can be tested using ZSTD_isError().
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]231 Note 1 : it's just a hint, to help latency a little, any other value will work fine.
232 Note 2 : size hint is guaranteed to be <= ZSTD_CStreamInSize()
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]233
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]234 At any moment, it's possible to flush whatever data remains within internal buffer, using ZSTD_flushStream().
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]235 `output->pos` will be updated.
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]236 Note that some content might still be left within internal buffer if `output->size` is too small.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]237 @return : nb of bytes still present within internal buffer (0 if it's empty)
238 or an error code, which can be tested using ZSTD_isError().
239
240 ZSTD_endStream() instructs to finish a frame.
241 It will perform a flush and write frame epilogue.
242 The epilogue is required for decoders to consider a frame completed.
Yann Colletfa3671e2017-05-19 10:51:30 -0700[diff] [blame]243 ZSTD_endStream() may not be able to flush full data if `output->size` is too small.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]244 In which case, call again ZSTD_endStream() to complete the flush.
Yann Colletfa3671e2017-05-19 10:51:30 -0700[diff] [blame]245 @return : 0 if frame fully completed and fully flushed,
246 or >0 if some data is still present within internal buffer
247 (value is minimum size estimation for remaining data to flush, but it could be more)
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]248 or an error code, which can be tested using ZSTD_isError().
249
250
251<BR></pre>
252
Yann Collet0be6fd32017-05-08 16:08:01 -0700[diff] [blame]253<pre><b>typedef ZSTD_CCtx ZSTD_CStream; </b>/**< CCtx and CStream are effectively same object */<b>
254</b></pre><BR>
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]255<h3>ZSTD_CStream management functions</h3><pre></pre><b><pre>ZSTD_CStream* ZSTD_createCStream(void);
256size_t ZSTD_freeCStream(ZSTD_CStream* zcs);
257</pre></b><BR>
258<h3>Streaming compression functions</h3><pre></pre><b><pre>size_t ZSTD_initCStream(ZSTD_CStream* zcs, int compressionLevel);
259size_t ZSTD_compressStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
260size_t ZSTD_flushStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
261size_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
262</pre></b><BR>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]263<pre><b>size_t ZSTD_CStreamInSize(void); </b>/**< recommended size for input buffer */<b>
264</b></pre><BR>
265<pre><b>size_t ZSTD_CStreamOutSize(void); </b>/**< recommended size for output buffer. Guarantee to successfully flush at least one complete compressed block in all circumstances. */<b>
266</b></pre><BR>
267<a name="Chapter9"></a><h2>Streaming decompression - HowTo</h2><pre>
268 A ZSTD_DStream object is required to track streaming operations.
269 Use ZSTD_createDStream() and ZSTD_freeDStream() to create/release resources.
270 ZSTD_DStream objects can be re-used multiple times.
271
272 Use ZSTD_initDStream() to start a new decompression operation,
273 or ZSTD_initDStream_usingDict() if decompression requires a dictionary.
274 @return : recommended first input size
275
276 Use ZSTD_decompressStream() repetitively to consume your input.
277 The function will update both `pos` fields.
278 If `input.pos < input.size`, some input has not been consumed.
279 It's up to the caller to present again remaining data.
280 If `output.pos < output.size`, decoder has flushed everything it could.
281 @return : 0 when a frame is completely decoded and fully flushed,
282 an error code, which can be tested using ZSTD_isError(),
Przemyslaw Skibinski4da53212016-12-07 11:18:40 +0100[diff] [blame]283 any other value > 0, which means there is still some decoding to do to complete current frame.
284 The return value is a suggested next input size (a hint to improve latency) that will never load more than the current frame.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]285
286<BR></pre>
287
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]288<h3>ZSTD_DStream management functions</h3><pre></pre><b><pre>ZSTD_DStream* ZSTD_createDStream(void);
289size_t ZSTD_freeDStream(ZSTD_DStream* zds);
290</pre></b><BR>
291<h3>Streaming decompression functions</h3><pre></pre><b><pre>size_t ZSTD_initDStream(ZSTD_DStream* zds);
292size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
293</pre></b><BR>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]294<pre><b>size_t ZSTD_DStreamInSize(void); </b>/*!< recommended size for input buffer */<b>
295</b></pre><BR>
296<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>
297</b></pre><BR>
298<a name="Chapter10"></a><h2>START OF ADVANCED AND EXPERIMENTAL FUNCTIONS</h2><pre> The definitions in this section are considered experimental.
299 They should never be used with a dynamic library, as they may change in the future.
300 They are provided for advanced usages.
301 Use them only in association with static linking.
302
303<BR></pre>
304
305<a name="Chapter11"></a><h2>Advanced types</h2><pre></pre>
306
Yann Colleta5ffe3d2017-05-12 16:29:19 -0700[diff] [blame]307<pre><b>typedef enum { ZSTD_fast=1, ZSTD_dfast, ZSTD_greedy, ZSTD_lazy, ZSTD_lazy2,
308 ZSTD_btlazy2, ZSTD_btopt, ZSTD_btultra } ZSTD_strategy; </b>/* from faster to stronger */<b>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]309</b></pre><BR>
310<pre><b>typedef struct {
311 unsigned windowLog; </b>/**< largest match distance : larger == more compression, more memory needed during decompression */<b>
312 unsigned chainLog; </b>/**< fully searched segment : larger == more compression, slower, more memory (useless for fast) */<b>
313 unsigned hashLog; </b>/**< dispatch table : larger == faster, more memory */<b>
314 unsigned searchLog; </b>/**< nb of searches : larger == more compression, slower */<b>
315 unsigned searchLength; </b>/**< match length searched : larger == faster decompression, sometimes less compression */<b>
316 unsigned targetLength; </b>/**< acceptable match size for optimal parser (only) : larger == more compression, slower */<b>
317 ZSTD_strategy strategy;
318} ZSTD_compressionParameters;
319</b></pre><BR>
320<pre><b>typedef struct {
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]321 unsigned contentSizeFlag; </b>/**< 1: content size will be in frame header (when known) */<b>
322 unsigned checksumFlag; </b>/**< 1: generate a 32-bits checksum at end of frame, for error detection */<b>
323 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]324} ZSTD_frameParameters;
325</b></pre><BR>
326<pre><b>typedef struct {
327 ZSTD_compressionParameters cParams;
328 ZSTD_frameParameters fParams;
329} ZSTD_parameters;
330</b></pre><BR>
Yann Colletf16f4492017-05-09 16:18:17 -0700[diff] [blame]331<pre><b>typedef struct {
332 unsigned long long frameContentSize;
333 unsigned windowSize;
334 unsigned dictID;
335 unsigned checksumFlag;
336} ZSTD_frameHeader;
337</b></pre><BR>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]338<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]339typedef void (*ZSTD_freeFunction) (void* opaque, void* address);
340typedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; void* opaque; } ZSTD_customMem;
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]341</pre></b><BR>
Yann Collet5a36c062017-05-09 15:11:30 -0700[diff] [blame]342<a name="Chapter12"></a><h2>Frame size functions</h2><pre></pre>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]343
Yann Collet831b4892017-02-23 23:09:10 -0800[diff] [blame]344<pre><b>size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize);
345</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]346 `srcSize` must be at least as large as the frame
Yann Collet5a36c062017-05-09 15:11:30 -0700[diff] [blame]347 @return : the compressed size of the frame pointed to by `src`,
348 suitable to pass to `ZSTD_decompress` or similar,
349 or an error code if given invalid input.
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]350</p></pre><BR>
351
Yann Collet5a36c062017-05-09 15:11:30 -0700[diff] [blame]352<pre><b>#define ZSTD_CONTENTSIZE_UNKNOWN (0ULL - 1)
353#define ZSTD_CONTENTSIZE_ERROR (0ULL - 2)
354unsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize);
355</b><p> `src` should point to the start of a ZSTD encoded frame.
356 `srcSize` must be at least as large as the frame header.
357 A value >= `ZSTD_frameHeaderSize_max` is guaranteed to be large enough.
358 @return : - decompressed size of the frame pointed to be `src` if known
359 - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined
360 - 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]361</p></pre><BR>
362
363<pre><b>unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize);
Yann Collet5a36c062017-05-09 15:11:30 -0700[diff] [blame]364</b><p> `src` should point the start of a series of ZSTD encoded and/or skippable frames
365 `srcSize` must be the _exact_ size of this series
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]366 (i.e. there should be a frame boundary exactly `srcSize` bytes after `src`)
Yann Collet5a36c062017-05-09 15:11:30 -0700[diff] [blame]367 @return : - decompressed size of all data in all successive frames
368 - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN
369 - if an error occurred: ZSTD_CONTENTSIZE_ERROR
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]370
Yann Collet5a36c062017-05-09 15:11:30 -0700[diff] [blame]371 note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode.
372 When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
373 In which case, it's necessary to use streaming mode to decompress data.
374 Optionally, application can still use ZSTD_decompress() while relying on implied limits.
375 (For example, data may be necessarily cut into blocks <= 16 KB).
376 note 2 : decompressed size is always present when compression is done with ZSTD_compress()
377 note 3 : decompressed size can be very large (64-bits value),
378 potentially larger than what local system can handle as a single memory segment.
379 In which case, it's necessary to use streaming mode to decompress data.
380 note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified.
381 Always ensure result fits within application's authorized limits.
382 Each application can set its own limits.
383 note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to
384 read each contained frame header. This is efficient as most of the data is skipped,
385 however it does mean that all frame data must be present and valid.
386</p></pre><BR>
387
388<a name="Chapter13"></a><h2>Context memory usage</h2><pre></pre>
389
390<pre><b>size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx);
391size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx);
392size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs);
393size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds);
394size_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict);
395size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict);
396</b><p> These functions give the current memory usage of selected object.
397 Object memory usage can evolve if it's re-used multiple times.
398</p></pre><BR>
399
400<pre><b>size_t ZSTD_estimateCCtxSize(ZSTD_compressionParameters cParams);
401size_t ZSTD_estimateDCtxSize(void);
402</b><p> These functions make it possible to estimate memory usage
403 of a future target object, before its allocation,
404 given a set of parameters, which vary depending on target object.
405 The objective is to guide decision before allocation.
406</p></pre><BR>
407
408<pre><b>size_t ZSTD_estimateCStreamSize(ZSTD_compressionParameters cParams);
Yann Colletf16f4492017-05-09 16:18:17 -0700[diff] [blame]409size_t ZSTD_estimateDStreamSize(ZSTD_frameHeader fHeader);
Yann Collet5a36c062017-05-09 15:11:30 -0700[diff] [blame]410</b><p> Note : if streaming is init with function ZSTD_init?Stream_usingDict(),
411 an internal ?Dict will be created, which size is not estimated.
412 In this case, get additional size by using ZSTD_estimate?DictSize
413</p></pre><BR>
414
415<pre><b>size_t ZSTD_estimateCDictSize(ZSTD_compressionParameters cParams, size_t dictSize);
416size_t ZSTD_estimateDDictSize(size_t dictSize);
417</b><p> Note : if dictionary is created "byReference", reduce estimation by dictSize
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]418</p></pre><BR>
419
420<a name="Chapter14"></a><h2>Advanced compression functions</h2><pre></pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]421
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]422<pre><b>ZSTD_CCtx* ZSTD_createCCtx_advanced(ZSTD_customMem customMem);
423</b><p> Create a ZSTD compression context using external alloc and free functions
424</p></pre><BR>
425
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]426<pre><b>typedef enum {
Yann Collet14312d82017-02-23 23:42:12 -0800[diff] [blame]427 ZSTD_p_forceWindow, </b>/* Force back-references to remain < windowSize, even when referencing Dictionary content (default:0) */<b>
428 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]429} ZSTD_CCtxParameter;
430</b></pre><BR>
431<pre><b>size_t ZSTD_setCCtxParameter(ZSTD_CCtx* cctx, ZSTD_CCtxParameter param, unsigned value);
432</b><p> Set advanced parameters, selected through enum ZSTD_CCtxParameter
433 @result : 0, or an error code (which can be tested with ZSTD_isError())
434</p></pre><BR>
435
436<pre><b>ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel);
437</b><p> Create a digested dictionary for compression
438 Dictionary content is simply referenced, and therefore stays in dictBuffer.
439 It is important that dictBuffer outlives CDict, it must remain read accessible throughout the lifetime of CDict
440</p></pre><BR>
441
442<pre><b>ZSTD_CDict* ZSTD_createCDict_advanced(const void* dict, size_t dictSize, unsigned byReference,
Yann Collet31533ba2017-04-27 00:29:04 -0700[diff] [blame]443 ZSTD_compressionParameters cParams, ZSTD_customMem customMem);
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]444</b><p> Create a ZSTD_CDict using external alloc and free, and customized compression parameters
445</p></pre><BR>
446
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]447<pre><b>ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
448</b><p> @return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize.
449 `estimatedSrcSize` value is optional, select 0 if not known
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]450</p></pre><BR>
451
Yann Colletdc993122016-12-14 14:53:47 +0100[diff] [blame]452<pre><b>ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
453</b><p> same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of sub-component `ZSTD_compressionParameters`.
454 All fields of `ZSTD_frameParameters` are set to default (0)
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]455</p></pre><BR>
456
457<pre><b>size_t ZSTD_checkCParams(ZSTD_compressionParameters params);
458</b><p> Ensure param values remain within authorized range
459</p></pre><BR>
460
461<pre><b>ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize);
462</b><p> optimize params for a given `srcSize` and `dictSize`.
463 both values are optional, select `0` if unknown.
464</p></pre><BR>
465
Yann Colletf4bd8572017-04-27 11:31:55 -0700[diff] [blame]466<pre><b>size_t ZSTD_compress_advanced (ZSTD_CCtx* cctx,
467 void* dst, size_t dstCapacity,
468 const void* src, size_t srcSize,
469 const void* dict,size_t dictSize,
470 ZSTD_parameters params);
471</b><p> Same as ZSTD_compress_usingDict(), with fine-tune control over each compression parameter
472</p></pre><BR>
473
474<pre><b>size_t ZSTD_compress_usingCDict_advanced(ZSTD_CCtx* cctx,
475 void* dst, size_t dstCapacity,
476 const void* src, size_t srcSize,
477 const ZSTD_CDict* cdict, ZSTD_frameParameters fParams);
Yann Collet77bf59e2017-04-27 11:43:04 -0700[diff] [blame]478</b><p> Same as ZSTD_compress_usingCDict(), with fine-tune control over frame parameters
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]479</p></pre><BR>
480
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]481<h3>New experimental advanced parameters API</h3><pre></pre><b><pre></pre></b><BR>
482<pre><b>typedef enum {
483 </b>/* compression parameters */<b>
Yann Colletb0edb7f2017-05-12 15:31:53 -0700[diff] [blame]484 ZSTD_p_compressionLevel=100, </b>/* Update all compression parameters according to pre-defined cLevel table<b>
485 * Default level is 3.
486 * Special: value 0 means "do not change cLevel". */
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]487 ZSTD_p_windowLog, </b>/* Maximum allowed back-reference distance, expressed as power of 2.<b>
488 * Must be clamped between ZSTD_WINDOWLOG_MIN and ZSTD_WINDOWLOG_MAX.
Yann Colletadd66f82017-05-12 15:59:48 -0700[diff] [blame]489 * default value : set through compressionLevel.
490 * Special: value 0 means "do not change windowLog". */
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]491 ZSTD_p_hashLog, </b>/* Size of the probe table, as a power of 2.<b>
492 * Resulting table size is (1 << (hashLog+2)).
493 * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX.
494 * Larger tables improve compression ratio of strategies <= dFast,
Yann Colletadd66f82017-05-12 15:59:48 -0700[diff] [blame]495 * and improve speed of strategies > dFast.
496 * Special: value 0 means "do not change hashLog". */
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]497 ZSTD_p_chainLog, </b>/* Size of the full-search table, as a power of 2.<b>
498 * Resulting table size is (1 << (chainLog+2)).
499 * Larger tables result in better and slower compression.
Yann Colletadd66f82017-05-12 15:59:48 -0700[diff] [blame]500 * This parameter is useless when using "fast" strategy.
501 * Special: value 0 means "do not change chainLog". */
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]502 ZSTD_p_searchLog, </b>/* Number of search attempts, as a power of 2.<b>
503 * More attempts result in better and slower compression.
Yann Colletadd66f82017-05-12 15:59:48 -0700[diff] [blame]504 * This parameter is useless when using "fast" and "dFast" strategies.
505 * Special: value 0 means "do not change searchLog". */
Yann Collet6d4fef32017-05-17 18:36:15 -0700[diff] [blame]506 ZSTD_p_minMatch, </b>/* Minimum size of searched matches (note : repCode matches can be smaller).<b>
Yann Colletb0edb7f2017-05-12 15:31:53 -0700[diff] [blame]507 * Larger values make faster compression and decompression, but decrease ratio.
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]508 * Must be clamped between ZSTD_SEARCHLENGTH_MIN and ZSTD_SEARCHLENGTH_MAX.
509 * Note that currently, for all strategies < btopt, effective minimum is 4.
Yann Colletadd66f82017-05-12 15:59:48 -0700[diff] [blame]510 * Note that currently, for all strategies > fast, effective maximum is 6.
511 * Special: value 0 means "do not change minMatchLength". */
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]512 ZSTD_p_targetLength, </b>/* Only useful for strategies >= btopt.<b>
513 * Length of Match considered "good enough" to stop search.
Yann Colletadd66f82017-05-12 15:59:48 -0700[diff] [blame]514 * Larger values make compression stronger and slower.
515 * Special: value 0 means "do not change targetLength". */
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]516 ZSTD_p_compressionStrategy, </b>/* See ZSTD_strategy enum definition.<b>
Yann Colletb0edb7f2017-05-12 15:31:53 -0700[diff] [blame]517 * Cast selected strategy as unsigned for ZSTD_CCtx_setParameter() compatibility.
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]518 * The higher the value of selected strategy, the more complex it is,
Yann Colleta5ffe3d2017-05-12 16:29:19 -0700[diff] [blame]519 * resulting in stronger and slower compression.
520 * Special: value 0 means "do not change strategy". */
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]521#if 0
522 ZSTD_p_windowSize, </b>/* Maximum allowed back-reference distance.<b>
523 * Can be set to a more precise value than windowLog.
524 * Will be transparently reduced to closest possible inferior value
525 * (see Zstandard compression format) */
526 </b>/* Not ready yet ! */<b>
527#endif
528
529 </b>/* frame parameters */<b>
530 ZSTD_p_contentSizeFlag=200, </b>/* Content size is written into frame header _whenever known_ (default:1) */<b>
Yann Collet6d4fef32017-05-17 18:36:15 -0700[diff] [blame]531 ZSTD_p_checksumFlag, </b>/* A 32-bits checksum of content is written at end of frame (default:0) */<b>
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]532 ZSTD_p_dictIDFlag, </b>/* When applicable, dictID of dictionary is provided in frame header (default:1) */<b>
533
534 </b>/* dictionary parameters */<b>
535 ZSTD_p_refDictContent=300, </b>/* Content of dictionary content will be referenced, instead of copied (default:0).<b>
536 * This avoids duplicating dictionary content.
Yann Collet6d4fef32017-05-17 18:36:15 -0700[diff] [blame]537 * But it also requires that dictionary buffer outlives its user (CDict) */
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]538 </b>/* Not ready yet ! */<b>
539 ZSTD_p_rawContentDict, </b>/* load dictionary in "content-only" mode (no header analysis) (default:0) */<b>
540 </b>/* question : should there be an option to load dictionary only in zstd format, rejecting others with an error code ? */<b>
541
542#if 0
543 </b>/* multi-threading parameters (not ready yet !) */<b>
544 ZSTD_p_nbThreads=400, </b>/* Select how many threads a compression job can spawn (default:1)<b>
545 * More threads improve speed, but increases also memory usage */
546 ZSTDMT_p_jobSize, </b>/* Size of a compression job. Each job is compressed in parallel.<b>
547 * 0 means default, which is dynamically determined based on compression parameters.
548 * Job size must be a minimum of overlapSize, or 1 KB, whichever is largest
549 * The minimum size is automatically and transparently enforced */
550 ZSTDMT_p_overlapSizeLog, </b>/* Size of previous input reloaded at the beginning of each job.<b>
551 * 0 => no overlap, 6(default) => use 1/8th of windowSize, >=9 => use full windowSize */
552#endif
553
554 </b>/* advanced parameters - may not remain available after API update */<b>
555 ZSTD_p_forceMaxWindow=1100, </b>/* Force back-references to remain < windowSize,<b>
556 * even when referencing into Dictionary content
557 * default : 0 when using a CDict, 1 when using a Prefix */
558} ZSTD_cParameter;
559</b></pre><BR>
560<pre><b>size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, unsigned value);
561</b><p> Set one compression parameter, selected by enum ZSTD_cParameter.
Yann Collet6d4fef32017-05-17 18:36:15 -0700[diff] [blame]562 Note : when `value` is an enum, cast it to unsigned for proper type checking.
563 @result : 0, or an error code (which can be tested with ZSTD_isError()).
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]564</p></pre><BR>
565
566<pre><b>size_t ZSTD_CCtx_setPledgedSrcSize(ZSTD_CCtx* cctx, unsigned long long pledgedSrcSize);
567</b><p> Total input data size to be compressed into a single frame.
568 This value will be controlled at the end, and result in error if not respected.
569 @result : 0, or an error code (which can be tested with ZSTD_isError()).
570 Note 1 : 0 means zero, empty.
571 In order to mean "unknown content size", pass constant ZSTD_CONTENTSIZE_UNKNOWN.
572 Note that ZSTD_CONTENTSIZE_UNKNOWN is default value for all new compression jobs.
573 Note 2 : If all data is provided and consumed in a single round,
574 this value is overriden by srcSize instead.
575</p></pre><BR>
576
Yann Collet6d4fef32017-05-17 18:36:15 -0700[diff] [blame]577<pre><b>size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, size_t dictSize); </b>/* Not ready yet ! */<b>
578</b><p> Create an internal CDict from dict buffer.
579 Decompression will have to use same buffer.
580 @result : 0, or an error code (which can be tested with ZSTD_isError()).
581 Special : Adding a NULL (or 0-size) dictionary invalidates any previous prefix,
582 meaning "return to no-dictionary mode".
583 Note 1 : Dictionary content will be copied internally,
584 except if ZSTD_p_refDictContent is set.
585 Note 2 : Loading a dictionary involves building tables, which are dependent on compression parameters.
586 For this reason, compression parameters cannot be changed anymore after loading a prefix.
587 It's also a CPU-heavy operation, with non-negligible impact on latency.
588 Note 3 : Dictionary will be used for all future compression jobs.
589 To return to "no-dictionary" situation, load a NULL dictionary
590</p></pre><BR>
591
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]592<pre><b>size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize); </b>/* Not ready yet ! */<b>
593</b><p> Reference a prefix (content-only dictionary) to bootstrap next compression job.
594 Decompression will have to use same prefix.
595 @result : 0, or an error code (which can be tested with ZSTD_isError()).
596 Special : Adding a NULL (or 0-size) dictionary invalidates any previous prefix, meaning "return to no-dictionary mode".
Yann Collet6d4fef32017-05-17 18:36:15 -0700[diff] [blame]597 Note 1 : Prefix buffer is referenced. It must outlive compression job.
598 Note 3 : Prefix is only used once. Tables are discarded at end of compression job.
599 If there is a need to use same prefix multiple times, consider embedding it into a ZSTD_CDict.
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]600 Note 2 : Referencing a prefix involves building tables, which are dependent on compression parameters.
601 For this reason, compression parameters cannot be changed anymore after loading a prefix.
Yann Collet6d4fef32017-05-17 18:36:15 -0700[diff] [blame]602 It's also a CPU-heavy operation, with non-negligible impact on latency.
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]603</p></pre><BR>
604
605<pre><b>ZSTD_CDict* ZSTD_CDict_createEmpty(void); </b>/* Not ready yet ! */<b>
606size_t ZSTD_CDict_setParameter(ZSTD_CDict* cdict, ZSTD_cParameter param, unsigned value); </b>/* Not ready yet ! */<b>
607size_t ZSTD_CDict_loadDictionary(ZSTD_CDict* cdict, const void* dict, size_t dictSize); </b>/* Not ready yet ! */<b>
608</b><p> Create a CDict object which is still mutable after creation.
Yann Colletdb8e21d2017-05-12 13:46:49 -0700[diff] [blame]609 It's the only one case allowing usage of ZSTD_CDict_setParameter().
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]610 Once all compression parameters are selected,
611 it's possible to load the target dictionary, using ZSTD_CDict_loadDictionary().
Yann Colletdb8e21d2017-05-12 13:46:49 -0700[diff] [blame]612 Dictionary content will be copied internally (except if ZSTD_p_refDictContent is set).
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]613 After loading the dictionary, no more change is possible.
614 The only remaining operation is to free CDict object.
Yann Colletdb8e21d2017-05-12 13:46:49 -0700[diff] [blame]615 Note : An unfinished CDict behaves the same as a NULL CDict if referenced into a CCtx.
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]616
617</p></pre><BR>
618
Yann Colletb0739bc2017-05-22 17:45:15 -0700[diff] [blame^]619<pre><b>size_t ZSTD_CCtx_refCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict);
Yann Collet6d4fef32017-05-17 18:36:15 -0700[diff] [blame]620</b><p> Add a prepared dictionary to cctx, to be used for next compression jobs.
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]621 Note that compression parameters will be enforced from within CDict.
622 Currently, they supercede any compression parameter previously set within CCtx.
Yann Collet6d4fef32017-05-17 18:36:15 -0700[diff] [blame]623 The dictionary will remain valid for future compression jobs using same cctx.
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]624 @result : 0, or an error code (which can be tested with ZSTD_isError()).
625 Special : adding a NULL CDict means "return to no-dictionary mode".
626 Note 1 : Currently, only one dictionary can be managed.
627 Adding a new dictionary effectively "discards" any previous one.
628 Note 2 : CDict is just referenced, its lifetime must outlive CCtx.
629
630</p></pre><BR>
631
632<pre><b>typedef enum {
Yann Collet6d4fef32017-05-17 18:36:15 -0700[diff] [blame]633 ZSTD_e_continue=0, </b>/* collect more data, encoder transparently decides when to output result, for optimal conditions */<b>
634 ZSTD_e_flush, </b>/* flush any data provided so far - frame will continue, future data can still reference previous data for better compression */<b>
635 ZSTD_e_end </b>/* flush any remaining data and ends current frame. Any future compression starts a new frame. */<b>
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]636} ZSTD_EndDirective;
637</b></pre><BR>
638<pre><b>size_t ZSTD_compress_generic (ZSTD_CCtx* cctx,
Yann Collet6d4fef32017-05-17 18:36:15 -0700[diff] [blame]639 ZSTD_outBuffer* output,
640 ZSTD_inBuffer* input,
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]641 ZSTD_EndDirective endOp);
642</b><p> Behave about the same as ZSTD_compressStream. To note :
643 - Compression parameters are pushed into CCtx before starting compression, using ZSTD_setCCtxParameter()
644 - Compression parameters cannot be changed once compression is started.
645 - *dstPos must be <= dstCapacity, *srcPos must be <= srcSize
646 - *dspPos and *srcPos will be updated. They are guaranteed to remain below their respective limit.
Yann Collet6d4fef32017-05-17 18:36:15 -0700[diff] [blame]647 - @return provides the amount of data ready to flush within internal buffers
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]648 or an error code, which can be tested using ZSTD_isError().
Yann Collet6d4fef32017-05-17 18:36:15 -0700[diff] [blame]649 if @return != 0, flush is not fully completed, and must be called again to empty internal buffers.
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]650 - after a ZSTD_e_end directive, if internal buffer is not fully flushed,
651 only ZSTD_e_end and ZSTD_e_flush operations are allowed.
652 It is necessary to fully flush internal buffers
653 before changing compression parameters or start a new compression job.
654
655</p></pre><BR>
656
Yann Collet6d4fef32017-05-17 18:36:15 -0700[diff] [blame]657<pre><b>size_t ZSTD_CCtx_reset(ZSTD_CCtx* cctx); </b>/* Not ready yet ! */<b>
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]658</b><p> Return a CCtx to clean state.
659 Useful after an error, or to interrupt an ongoing compression job and start a new one.
Yann Collet6d4fef32017-05-17 18:36:15 -0700[diff] [blame]660 It's possible to modify compression parameters after a reset.
Yann Collet33eb7ac2017-05-12 12:36:11 -0700[diff] [blame]661 Any internal data not yet flushed is cancelled.
662
663</p></pre><BR>
664
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]665<a name="Chapter15"></a><h2>Advanced decompression functions</h2><pre></pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]666
Przemyslaw Skibinski4da53212016-12-07 11:18:40 +0100[diff] [blame]667<pre><b>unsigned ZSTD_isFrame(const void* buffer, size_t size);
668</b><p> Tells if the content of `buffer` starts with a valid Frame Identifier.
669 Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0.
670 Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled.
671 Note 3 : Skippable Frame Identifiers are considered valid.
672</p></pre><BR>
673
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]674<pre><b>ZSTD_DCtx* ZSTD_createDCtx_advanced(ZSTD_customMem customMem);
675</b><p> Create a ZSTD decompression context using external alloc and free functions
676</p></pre><BR>
677
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]678<pre><b>ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize);
679</b><p> Create a digested dictionary, ready to start decompression operation without startup delay.
680 Dictionary content is simply referenced, and therefore stays in dictBuffer.
681 It is important that dictBuffer outlives DDict, it must remain read accessible throughout the lifetime of DDict
682</p></pre><BR>
683
Sean Purcelldec2b962017-03-14 11:24:09 -0700[diff] [blame]684<pre><b>ZSTD_DDict* ZSTD_createDDict_advanced(const void* dict, size_t dictSize,
685 unsigned byReference, ZSTD_customMem customMem);
686</b><p> Create a ZSTD_DDict using external alloc and free, optionally by reference
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]687</p></pre><BR>
688
Przemyslaw Skibinski4da53212016-12-07 11:18:40 +0100[diff] [blame]689<pre><b>unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize);
690</b><p> Provides the dictID stored within dictionary.
691 if @return == 0, the dictionary is not conformant with Zstandard specification.
692 It can still be loaded, but as a content-only dictionary.
693</p></pre><BR>
694
695<pre><b>unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict);
696</b><p> Provides the dictID of the dictionary loaded into `ddict`.
697 If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
698 Non-conformant dictionaries can still be loaded, but as content-only dictionaries.
699</p></pre><BR>
700
701<pre><b>unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize);
702</b><p> Provides the dictID required to decompressed the frame stored within `src`.
703 If @return == 0, the dictID could not be decoded.
704 This could for one of the following reasons :
705 - The frame does not require a dictionary to be decoded (most common case).
706 - The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden information.
707 Note : this use case also happens when using a non-conformant dictionary.
708 - `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`).
709 - This is not a Zstandard frame.
Yann Collet202082f2017-04-28 16:56:39 -0700[diff] [blame]710 When identifying the exact failure cause, it's possible to use ZSTD_getFrameParams(), which will provide a more precise error code.
Przemyslaw Skibinski4da53212016-12-07 11:18:40 +0100[diff] [blame]711</p></pre><BR>
712
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]713<a name="Chapter16"></a><h2>Advanced streaming functions</h2><pre></pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]714
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]715<h3>Advanced Streaming compression functions</h3><pre></pre><b><pre>ZSTD_CStream* ZSTD_createCStream_advanced(ZSTD_customMem customMem);
716size_t ZSTD_initCStream_srcSize(ZSTD_CStream* zcs, int compressionLevel, unsigned long long pledgedSrcSize); </b>/**< pledgedSrcSize must be correct, a size of 0 means unknown. for a frame size of 0 use initCStream_advanced */<b>
Yann Colleta1d67042017-05-08 17:51:49 -0700[diff] [blame]717size_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. This result in the creation of an internal CDict */<b>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]718size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs, const void* dict, size_t dictSize,
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]719 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]720size_t ZSTD_initCStream_usingCDict(ZSTD_CStream* zcs, const ZSTD_CDict* cdict); </b>/**< note : cdict will just be referenced, and must outlive compression session */<b>
Yann Collet77bf59e2017-04-27 11:43:04 -0700[diff] [blame]721size_t ZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs, const ZSTD_CDict* cdict, unsigned long long pledgedSrcSize, ZSTD_frameParameters fParams); </b>/**< same as ZSTD_initCStream_usingCDict(), with control over frame parameters */<b>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]722</pre></b><BR>
Yann Collet4b987ad2017-04-10 17:50:44 -0700[diff] [blame]723<pre><b>size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize);
724</b><p> start a new compression job, using same parameters from previous job.
725 This is typically useful to skip dictionary loading stage, since it will re-use it in-place..
726 Note that zcs must be init at least once before using ZSTD_resetCStream().
727 pledgedSrcSize==0 means "srcSize unknown".
728 If pledgedSrcSize > 0, its value must be correct, as it will be written in header, and controlled at the end.
729 @return : 0, or an error code (which can be tested using ZSTD_isError())
730</p></pre><BR>
731
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]732<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]733ZSTD_DStream* ZSTD_createDStream_advanced(ZSTD_customMem customMem);
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]734size_t ZSTD_setDStreamParameter(ZSTD_DStream* zds, ZSTD_DStreamParameter_e paramType, unsigned paramValue);
Yann Collet5a36c062017-05-09 15:11:30 -0700[diff] [blame]735size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize); </b>/**< note: a dict will not be used if dict == NULL or dictSize < 8 */<b>
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]736size_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]737size_t ZSTD_resetDStream(ZSTD_DStream* zds); </b>/**< re-use decompression parameters from previous init; saves dictionary loading */<b>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]738</pre></b><BR>
739<a name="Chapter17"></a><h2>Buffer-less and synchronous inner streaming functions</h2><pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]740 This is an advanced API, giving full control over buffer management, for users which need direct control over memory.
741 But it's also a complex one, with many restrictions (documented below).
Przemyslaw Skibinski1fd5b452016-10-31 10:44:44 +0100[diff] [blame]742 Prefer using normal streaming API for an easier experience
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]743
744<BR></pre>
745
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]746<a name="Chapter18"></a><h2>Buffer-less streaming compression (synchronous mode)</h2><pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]747 A ZSTD_CCtx object is required to track streaming operations.
748 Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource.
749 ZSTD_CCtx object can be re-used multiple times within successive compression operations.
750
751 Start by initializing a context.
752 Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary compression,
753 or ZSTD_compressBegin_advanced(), for finer parameter control.
754 It's also possible to duplicate a reference context which has already been initialized, using ZSTD_copyCCtx()
755
756 Then, consume your input using ZSTD_compressContinue().
757 There are some important considerations to keep in mind when using this advanced function :
758 - ZSTD_compressContinue() has no internal buffer. It uses externally provided buffer only.
759 - Interface is synchronous : input is consumed entirely and produce 1+ (or more) compressed blocks.
760 - Caller must ensure there is enough space in `dst` to store compressed data under worst case scenario.
761 Worst case evaluation is provided by ZSTD_compressBound().
762 ZSTD_compressContinue() doesn't guarantee recover after a failed compression.
763 - ZSTD_compressContinue() presumes prior input ***is still accessible and unmodified*** (up to maximum distance size, see WindowLog).
764 It remembers all previous contiguous blocks, plus one separated memory segment (which can itself consists of multiple contiguous blocks)
765 - ZSTD_compressContinue() detects that prior input has been overwritten when `src` buffer overlaps.
766 In which case, it will "discard" the relevant memory section from its history.
767
768 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]769 It's possible to use srcSize==0, in which case, it will write a final empty block to end the frame.
770 Without last block mark, frames will be considered unfinished (corrupted) by decoders.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]771
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]772 `ZSTD_CCtx` object can be re-used (ZSTD_compressBegin()) to compress some new frame.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]773<BR></pre>
774
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]775<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]776size_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]777size_t ZSTD_compressBegin_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_parameters params, unsigned long long pledgedSrcSize); </b>/**< pledgedSrcSize is optional and can be 0 (meaning unknown). note: if the contentSizeFlag is set, pledgedSrcSize == 0 means the source size is actually 0 */<b>
Yann Collet768df122017-04-26 15:42:10 -0700[diff] [blame]778size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); </b>/**< note: fails if cdict==NULL */<b>
Yann Collet715b9aa2017-04-18 13:55:53 -0700[diff] [blame]779size_t ZSTD_compressBegin_usingCDict_advanced(ZSTD_CCtx* const cctx, const ZSTD_CDict* const cdict, ZSTD_frameParameters const fParams, unsigned long long const pledgedSrcSize); </b>/* compression parameters are already set within cdict. pledgedSrcSize=0 means null-size */<b>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]780size_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]781</pre></b><BR>
782<a name="Chapter19"></a><h2>Buffer-less streaming decompression (synchronous mode)</h2><pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]783 A ZSTD_DCtx object is required to track streaming operations.
784 Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it.
785 A ZSTD_DCtx object can be re-used multiple times.
786
787 First typical operation is to retrieve frame parameters, using ZSTD_getFrameParams().
788 It fills a ZSTD_frameParams structure which provide important information to correctly decode the frame,
789 such as the minimum rolling buffer size to allocate to decompress data (`windowSize`),
790 and the dictionary ID used.
791 (Note : content size is optional, it may not be present. 0 means : content size unknown).
792 Note that these values could be wrong, either because of data malformation, or because an attacker is spoofing deliberate false information.
793 As a consequence, check that values remain within valid application range, especially `windowSize`, before allocation.
794 Each application can set its own limit, depending on local restrictions. For extended interoperability, it is recommended to support at least 8 MB.
795 Frame parameters are extracted from the beginning of the compressed frame.
796 Data fragment must be large enough to ensure successful decoding, typically `ZSTD_frameHeaderSize_max` bytes.
797 @result : 0 : successful decoding, the `ZSTD_frameParams` structure is correctly filled.
798 >0 : `srcSize` is too small, please provide at least @result bytes on next attempt.
799 errorCode, which can be tested using ZSTD_isError().
800
Yann Collet6d4fef32017-05-17 18:36:15 -0700[diff] [blame]801 Start decompression, with ZSTD_decompressBegin().
802 If decompression requires a dictionary, use ZSTD_decompressBegin_usingDict() or ZSTD_decompressBegin_usingDDict().
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]803 Alternatively, you can copy a prepared context, using ZSTD_copyDCtx().
804
805 Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively.
806 ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize' to ZSTD_decompressContinue().
807 ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will fail.
808
809 @result of ZSTD_decompressContinue() is the number of bytes regenerated within 'dst' (necessarily <= dstCapacity).
810 It can be zero, which is not an error; it just means ZSTD_decompressContinue() has decoded some metadata item.
811 It can also be an error code, which can be tested with ZSTD_isError().
812
813 ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize`.
814 They should preferably be located contiguously, prior to current block.
815 Alternatively, a round buffer of sufficient size is also possible. Sufficient size is determined by frame parameters.
816 ZSTD_decompressContinue() is very sensitive to contiguity,
817 if 2 blocks don't follow each other, make sure that either the compressor breaks contiguity at the same place,
818 or that previous contiguous segment is large enough to properly handle maximum back-reference.
819
820 A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero.
821 Context can then be reset to start a new decompression.
822
823 Note : it's possible to know if next input to present is a header or a block, using ZSTD_nextInputType().
824 This information is not required to properly decode a frame.
825
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]826 == Special case : skippable frames
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]827
828 Skippable frames allow integration of user-defined data into a flow of concatenated frames.
829 Skippable frames will be ignored (skipped) by a decompressor. The format of skippable frames is as follows :
830 a) Skippable frame ID - 4 Bytes, Little endian format, any value from 0x184D2A50 to 0x184D2A5F
831 b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits
832 c) Frame Content - any content (User Data) of length equal to Frame Size
833 For skippable frames ZSTD_decompressContinue() always returns 0.
834 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]835 Note : If fparamsPtr->frameContentSize==0, it is ambiguous: the frame might actually be a Zstd encoded frame with no content.
836 For purposes of decompression, it is valid in both cases to skip the frame using
837 ZSTD_findFrameCompressedSize to find its size in bytes.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]838 It also returns Frame Size as fparamsPtr->frameContentSize.
839<BR></pre>
840
Yann Colletcef02d92017-05-10 11:14:08 -0700[diff] [blame]841<h3>Buffer-less streaming decompression functions</h3><pre></pre><b><pre>size_t ZSTD_getFrameHeader(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize); </b>/**< doesn't consume input, see details below */<b>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]842size_t ZSTD_decompressBegin(ZSTD_DCtx* dctx);
843size_t ZSTD_decompressBegin_usingDict(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
Yann Collet6d4fef32017-05-17 18:36:15 -0700[diff] [blame]844size_t ZSTD_decompressBegin_usingDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict);
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]845void ZSTD_copyDCtx(ZSTD_DCtx* dctx, const ZSTD_DCtx* preparedDCtx);
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]846</pre></b><BR>
Yann Collet6d4fef32017-05-17 18:36:15 -0700[diff] [blame]847<pre><b>typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e;
848</b></pre><BR>
Yann Collet77575772017-02-22 01:10:43 -0800[diff] [blame]849<a name="Chapter20"></a><h2>Block functions</h2><pre>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]850 Block functions produce and decode raw zstd blocks, without frame metadata.
851 Frame metadata cost is typically ~18 bytes, which can be non-negligible for very small blocks (< 100 bytes).
852 User will have to take in charge required information to regenerate data, such as compressed and content sizes.
853
854 A few rules to respect :
855 - Compressing and decompressing require a context structure
856 + Use ZSTD_createCCtx() and ZSTD_createDCtx()
857 - It is necessary to init context before starting
Yann Collet715b9aa2017-04-18 13:55:53 -0700[diff] [blame]858 + compression : any ZSTD_compressBegin*() variant, including with dictionary
859 + decompression : any ZSTD_decompressBegin*() variant, including with dictionary
860 + copyCCtx() and copyDCtx() can be used too
Yann Colletfa3671e2017-05-19 10:51:30 -0700[diff] [blame]861 - Block size is limited, it must be <= ZSTD_getBlockSize() <= ZSTD_BLOCKSIZE_MAX
Yann Collet715b9aa2017-04-18 13:55:53 -0700[diff] [blame]862 + If input is larger than a block size, it's necessary to split input data into multiple blocks
863 + For inputs larger than a single block size, consider using the regular ZSTD_compress() instead.
864 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]865 - When a block is considered not compressible enough, ZSTD_compressBlock() result will be zero.
866 In which case, nothing is produced into `dst`.
867 + User must test for such outcome and deal directly with uncompressed data
868 + ZSTD_decompressBlock() doesn't accept uncompressed data as input !!!
Yann Collet715b9aa2017-04-18 13:55:53 -0700[diff] [blame]869 + In case of multiple successive blocks, should some of them be uncompressed,
870 decoder must be informed of their existence in order to follow proper history.
871 Use ZSTD_insertBlock() for such a case.
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]872<BR></pre>
873
Yann Colletfa3671e2017-05-19 10:51:30 -0700[diff] [blame]874<h3>Raw zstd block functions</h3><pre></pre><b><pre>size_t ZSTD_getBlockSize (const ZSTD_CCtx* cctx);
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]875size_t ZSTD_compressBlock (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
876size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
877size_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]878</pre></b><BR>
Przemyslaw Skibinski86d94242016-10-24 16:07:53 +0200[diff] [blame]879</html>
880</body>