1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> 4<title>1.9.3 Manual</title> 5</head> 6<body> 7<h1>1.9.3 Manual</h1> 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">Compiler specifics</a></li> 13<li><a href="#Chapter3">Error management</a></li> 14<li><a href="#Chapter4">Frame compression types</a></li> 15<li><a href="#Chapter5">Simple compression function</a></li> 16<li><a href="#Chapter6">Advanced compression functions</a></li> 17<li><a href="#Chapter7">Resource Management</a></li> 18<li><a href="#Chapter8">Compression</a></li> 19<li><a href="#Chapter9">Decompression functions</a></li> 20<li><a href="#Chapter10">Streaming decompression functions</a></li> 21<li><a href="#Chapter11">Bulk processing dictionary API</a></li> 22</ol> 23<hr> 24<a name="Chapter1"></a><h2>Introduction</h2><pre> 25 lz4frame.h implements LZ4 frame specification (doc/lz4_Frame_format.md). 26 lz4frame.h provides frame compression functions that take care 27 of encoding standard metadata alongside LZ4-compressed blocks. 28<BR></pre> 29 30<a name="Chapter2"></a><h2>Compiler specifics</h2><pre></pre> 31 32<a name="Chapter3"></a><h2>Error management</h2><pre></pre> 33 34<pre><b>unsigned LZ4F_isError(LZ4F_errorCode_t code); </b>/**< tells when a function result is an error code */<b> 35</b></pre><BR> 36<pre><b>const char* LZ4F_getErrorName(LZ4F_errorCode_t code); </b>/**< return error code string; for debugging */<b> 37</b></pre><BR> 38<a name="Chapter4"></a><h2>Frame compression types</h2><pre> 39<BR></pre> 40 41<pre><b>typedef enum { 42 LZ4F_default=0, 43 LZ4F_max64KB=4, 44 LZ4F_max256KB=5, 45 LZ4F_max1MB=6, 46 LZ4F_max4MB=7 47 LZ4F_OBSOLETE_ENUM(max64KB) 48 LZ4F_OBSOLETE_ENUM(max256KB) 49 LZ4F_OBSOLETE_ENUM(max1MB) 50 LZ4F_OBSOLETE_ENUM(max4MB) 51} LZ4F_blockSizeID_t; 52</b></pre><BR> 53<pre><b>typedef enum { 54 LZ4F_blockLinked=0, 55 LZ4F_blockIndependent 56 LZ4F_OBSOLETE_ENUM(blockLinked) 57 LZ4F_OBSOLETE_ENUM(blockIndependent) 58} LZ4F_blockMode_t; 59</b></pre><BR> 60<pre><b>typedef enum { 61 LZ4F_noContentChecksum=0, 62 LZ4F_contentChecksumEnabled 63 LZ4F_OBSOLETE_ENUM(noContentChecksum) 64 LZ4F_OBSOLETE_ENUM(contentChecksumEnabled) 65} LZ4F_contentChecksum_t; 66</b></pre><BR> 67<pre><b>typedef enum { 68 LZ4F_noBlockChecksum=0, 69 LZ4F_blockChecksumEnabled 70} LZ4F_blockChecksum_t; 71</b></pre><BR> 72<pre><b>typedef enum { 73 LZ4F_frame=0, 74 LZ4F_skippableFrame 75 LZ4F_OBSOLETE_ENUM(skippableFrame) 76} LZ4F_frameType_t; 77</b></pre><BR> 78<pre><b>typedef struct { 79 LZ4F_blockSizeID_t blockSizeID; </b>/* max64KB, max256KB, max1MB, max4MB; 0 == default */<b> 80 LZ4F_blockMode_t blockMode; </b>/* LZ4F_blockLinked, LZ4F_blockIndependent; 0 == default */<b> 81 LZ4F_contentChecksum_t contentChecksumFlag; </b>/* 1: frame terminated with 32-bit checksum of decompressed data; 0: disabled (default) */<b> 82 LZ4F_frameType_t frameType; </b>/* read-only field : LZ4F_frame or LZ4F_skippableFrame */<b> 83 unsigned long long contentSize; </b>/* Size of uncompressed content ; 0 == unknown */<b> 84 unsigned dictID; </b>/* Dictionary ID, sent by compressor to help decoder select correct dictionary; 0 == no dictID provided */<b> 85 LZ4F_blockChecksum_t blockChecksumFlag; </b>/* 1: each block followed by a checksum of block's compressed data; 0: disabled (default) */<b> 86} LZ4F_frameInfo_t; 87</b><p> makes it possible to set or read frame parameters. 88 Structure must be first init to 0, using memset() or LZ4F_INIT_FRAMEINFO, 89 setting all parameters to default. 90 It's then possible to update selectively some parameters 91</p></pre><BR> 92 93<pre><b>typedef struct { 94 LZ4F_frameInfo_t frameInfo; 95 int compressionLevel; </b>/* 0: default (fast mode); values > LZ4HC_CLEVEL_MAX count as LZ4HC_CLEVEL_MAX; values < 0 trigger "fast acceleration" */<b> 96 unsigned autoFlush; </b>/* 1: always flush; reduces usage of internal buffers */<b> 97 unsigned favorDecSpeed; </b>/* 1: parser favors decompression speed vs compression ratio. Only works for high compression modes (>= LZ4HC_CLEVEL_OPT_MIN) */ /* v1.8.2+ */<b> 98 unsigned reserved[3]; </b>/* must be zero for forward compatibility */<b> 99} LZ4F_preferences_t; 100</b><p> makes it possible to supply advanced compression instructions to streaming interface. 101 Structure must be first init to 0, using memset() or LZ4F_INIT_PREFERENCES, 102 setting all parameters to default. 103 All reserved fields must be set to zero. 104</p></pre><BR> 105 106<a name="Chapter5"></a><h2>Simple compression function</h2><pre></pre> 107 108<pre><b>size_t LZ4F_compressFrameBound(size_t srcSize, const LZ4F_preferences_t* preferencesPtr); 109</b><p> Returns the maximum possible compressed size with LZ4F_compressFrame() given srcSize and preferences. 110 `preferencesPtr` is optional. It can be replaced by NULL, in which case, the function will assume default preferences. 111 Note : this result is only usable with LZ4F_compressFrame(). 112 It may also be used with LZ4F_compressUpdate() _if no flush() operation_ is performed. 113 114</p></pre><BR> 115 116<pre><b>size_t LZ4F_compressFrame(void* dstBuffer, size_t dstCapacity, 117 const void* srcBuffer, size_t srcSize, 118 const LZ4F_preferences_t* preferencesPtr); 119</b><p> Compress an entire srcBuffer into a valid LZ4 frame. 120 dstCapacity MUST be >= LZ4F_compressFrameBound(srcSize, preferencesPtr). 121 The LZ4F_preferences_t structure is optional : you can provide NULL as argument. All preferences will be set to default. 122 @return : number of bytes written into dstBuffer. 123 or an error code if it fails (can be tested using LZ4F_isError()) 124 125</p></pre><BR> 126 127<a name="Chapter6"></a><h2>Advanced compression functions</h2><pre></pre> 128 129<pre><b>typedef struct { 130 unsigned stableSrc; </b>/* 1 == src content will remain present on future calls to LZ4F_compress(); skip copying src content within tmp buffer */<b> 131 unsigned reserved[3]; 132} LZ4F_compressOptions_t; 133</b></pre><BR> 134<a name="Chapter7"></a><h2>Resource Management</h2><pre></pre> 135 136<pre><b>LZ4F_errorCode_t LZ4F_createCompressionContext(LZ4F_cctx** cctxPtr, unsigned version); 137LZ4F_errorCode_t LZ4F_freeCompressionContext(LZ4F_cctx* cctx); 138</b><p> The first thing to do is to create a compressionContext object, which will be used in all compression operations. 139 This is achieved using LZ4F_createCompressionContext(), which takes as argument a version. 140 The version provided MUST be LZ4F_VERSION. It is intended to track potential version mismatch, notably when using DLL. 141 The function will provide a pointer to a fully allocated LZ4F_cctx object. 142 If @return != zero, there was an error during context creation. 143 Object can release its memory using LZ4F_freeCompressionContext(); 144 145</p></pre><BR> 146 147<a name="Chapter8"></a><h2>Compression</h2><pre></pre> 148 149<pre><b>size_t LZ4F_compressBegin(LZ4F_cctx* cctx, 150 void* dstBuffer, size_t dstCapacity, 151 const LZ4F_preferences_t* prefsPtr); 152</b><p> will write the frame header into dstBuffer. 153 dstCapacity must be >= LZ4F_HEADER_SIZE_MAX bytes. 154 `prefsPtr` is optional : you can provide NULL as argument, all preferences will then be set to default. 155 @return : number of bytes written into dstBuffer for the header 156 or an error code (which can be tested using LZ4F_isError()) 157 158</p></pre><BR> 159 160<pre><b>size_t LZ4F_compressBound(size_t srcSize, const LZ4F_preferences_t* prefsPtr); 161</b><p> Provides minimum dstCapacity required to guarantee success of 162 LZ4F_compressUpdate(), given a srcSize and preferences, for a worst case scenario. 163 When srcSize==0, LZ4F_compressBound() provides an upper bound for LZ4F_flush() and LZ4F_compressEnd() instead. 164 Note that the result is only valid for a single invocation of LZ4F_compressUpdate(). 165 When invoking LZ4F_compressUpdate() multiple times, 166 if the output buffer is gradually filled up instead of emptied and re-used from its start, 167 one must check if there is enough remaining capacity before each invocation, using LZ4F_compressBound(). 168 @return is always the same for a srcSize and prefsPtr. 169 prefsPtr is optional : when NULL is provided, preferences will be set to cover worst case scenario. 170 tech details : 171 @return if automatic flushing is not enabled, includes the possibility that internal buffer might already be filled by up to (blockSize-1) bytes. 172 It also includes frame footer (ending + checksum), since it might be generated by LZ4F_compressEnd(). 173 @return doesn't include frame header, as it was already generated by LZ4F_compressBegin(). 174 175</p></pre><BR> 176 177<pre><b>size_t LZ4F_compressUpdate(LZ4F_cctx* cctx, 178 void* dstBuffer, size_t dstCapacity, 179 const void* srcBuffer, size_t srcSize, 180 const LZ4F_compressOptions_t* cOptPtr); 181</b><p> LZ4F_compressUpdate() can be called repetitively to compress as much data as necessary. 182 Important rule: dstCapacity MUST be large enough to ensure operation success even in worst case situations. 183 This value is provided by LZ4F_compressBound(). 184 If this condition is not respected, LZ4F_compress() will fail (result is an errorCode). 185 LZ4F_compressUpdate() doesn't guarantee error recovery. 186 When an error occurs, compression context must be freed or resized. 187 `cOptPtr` is optional : NULL can be provided, in which case all options are set to default. 188 @return : number of bytes written into `dstBuffer` (it can be zero, meaning input data was just buffered). 189 or an error code if it fails (which can be tested using LZ4F_isError()) 190 191</p></pre><BR> 192 193<pre><b>size_t LZ4F_flush(LZ4F_cctx* cctx, 194 void* dstBuffer, size_t dstCapacity, 195 const LZ4F_compressOptions_t* cOptPtr); 196</b><p> When data must be generated and sent immediately, without waiting for a block to be completely filled, 197 it's possible to call LZ4_flush(). It will immediately compress any data buffered within cctx. 198 `dstCapacity` must be large enough to ensure the operation will be successful. 199 `cOptPtr` is optional : it's possible to provide NULL, all options will be set to default. 200 @return : nb of bytes written into dstBuffer (can be zero, when there is no data stored within cctx) 201 or an error code if it fails (which can be tested using LZ4F_isError()) 202 Note : LZ4F_flush() is guaranteed to be successful when dstCapacity >= LZ4F_compressBound(0, prefsPtr). 203 204</p></pre><BR> 205 206<pre><b>size_t LZ4F_compressEnd(LZ4F_cctx* cctx, 207 void* dstBuffer, size_t dstCapacity, 208 const LZ4F_compressOptions_t* cOptPtr); 209</b><p> To properly finish an LZ4 frame, invoke LZ4F_compressEnd(). 210 It will flush whatever data remained within `cctx` (like LZ4_flush()) 211 and properly finalize the frame, with an endMark and a checksum. 212 `cOptPtr` is optional : NULL can be provided, in which case all options will be set to default. 213 @return : nb of bytes written into dstBuffer, necessarily >= 4 (endMark), 214 or an error code if it fails (which can be tested using LZ4F_isError()) 215 Note : LZ4F_compressEnd() is guaranteed to be successful when dstCapacity >= LZ4F_compressBound(0, prefsPtr). 216 A successful call to LZ4F_compressEnd() makes `cctx` available again for another compression task. 217 218</p></pre><BR> 219 220<a name="Chapter9"></a><h2>Decompression functions</h2><pre></pre> 221 222<pre><b>typedef struct { 223 unsigned stableDst; </b>/* pledges that last 64KB decompressed data will remain available unmodified. This optimization skips storage operations in tmp buffers. */<b> 224 unsigned reserved[3]; </b>/* must be set to zero for forward compatibility */<b> 225} LZ4F_decompressOptions_t; 226</b></pre><BR> 227<pre><b>LZ4F_errorCode_t LZ4F_createDecompressionContext(LZ4F_dctx** dctxPtr, unsigned version); 228LZ4F_errorCode_t LZ4F_freeDecompressionContext(LZ4F_dctx* dctx); 229</b><p> Create an LZ4F_dctx object, to track all decompression operations. 230 The version provided MUST be LZ4F_VERSION. 231 The function provides a pointer to an allocated and initialized LZ4F_dctx object. 232 The result is an errorCode, which can be tested using LZ4F_isError(). 233 dctx memory can be released using LZ4F_freeDecompressionContext(); 234 Result of LZ4F_freeDecompressionContext() indicates current state of decompressionContext when being released. 235 That is, it should be == 0 if decompression has been completed fully and correctly. 236 237</p></pre><BR> 238 239<a name="Chapter10"></a><h2>Streaming decompression functions</h2><pre></pre> 240 241<pre><b>size_t LZ4F_headerSize(const void* src, size_t srcSize); 242</b><p> Provide the header size of a frame starting at `src`. 243 `srcSize` must be >= LZ4F_MIN_SIZE_TO_KNOW_HEADER_LENGTH, 244 which is enough to decode the header length. 245 @return : size of frame header 246 or an error code, which can be tested using LZ4F_isError() 247 note : Frame header size is variable, but is guaranteed to be 248 >= LZ4F_HEADER_SIZE_MIN bytes, and <= LZ4F_HEADER_SIZE_MAX bytes. 249 250</p></pre><BR> 251 252<pre><b>size_t LZ4F_getFrameInfo(LZ4F_dctx* dctx, 253 LZ4F_frameInfo_t* frameInfoPtr, 254 const void* srcBuffer, size_t* srcSizePtr); 255</b><p> This function extracts frame parameters (max blockSize, dictID, etc.). 256 Its usage is optional: user can call LZ4F_decompress() directly. 257 258 Extracted information will fill an existing LZ4F_frameInfo_t structure. 259 This can be useful for allocation and dictionary identification purposes. 260 261 LZ4F_getFrameInfo() can work in the following situations : 262 263 1) At the beginning of a new frame, before any invocation of LZ4F_decompress(). 264 It will decode header from `srcBuffer`, 265 consuming the header and starting the decoding process. 266 267 Input size must be large enough to contain the full frame header. 268 Frame header size can be known beforehand by LZ4F_headerSize(). 269 Frame header size is variable, but is guaranteed to be >= LZ4F_HEADER_SIZE_MIN bytes, 270 and not more than <= LZ4F_HEADER_SIZE_MAX bytes. 271 Hence, blindly providing LZ4F_HEADER_SIZE_MAX bytes or more will always work. 272 It's allowed to provide more input data than the header size, 273 LZ4F_getFrameInfo() will only consume the header. 274 275 If input size is not large enough, 276 aka if it's smaller than header size, 277 function will fail and return an error code. 278 279 2) After decoding has been started, 280 it's possible to invoke LZ4F_getFrameInfo() anytime 281 to extract already decoded frame parameters stored within dctx. 282 283 Note that, if decoding has barely started, 284 and not yet read enough information to decode the header, 285 LZ4F_getFrameInfo() will fail. 286 287 The number of bytes consumed from srcBuffer will be updated in *srcSizePtr (necessarily <= original value). 288 LZ4F_getFrameInfo() only consumes bytes when decoding has not yet started, 289 and when decoding the header has been successful. 290 Decompression must then resume from (srcBuffer + *srcSizePtr). 291 292 @return : a hint about how many srcSize bytes LZ4F_decompress() expects for next call, 293 or an error code which can be tested using LZ4F_isError(). 294 note 1 : in case of error, dctx is not modified. Decoding operation can resume from beginning safely. 295 note 2 : frame parameters are *copied into* an already allocated LZ4F_frameInfo_t structure. 296 297</p></pre><BR> 298 299<pre><b>size_t LZ4F_decompress(LZ4F_dctx* dctx, 300 void* dstBuffer, size_t* dstSizePtr, 301 const void* srcBuffer, size_t* srcSizePtr, 302 const LZ4F_decompressOptions_t* dOptPtr); 303</b><p> Call this function repetitively to regenerate data compressed in `srcBuffer`. 304 305 The function requires a valid dctx state. 306 It will read up to *srcSizePtr bytes from srcBuffer, 307 and decompress data into dstBuffer, of capacity *dstSizePtr. 308 309 The nb of bytes consumed from srcBuffer will be written into *srcSizePtr (necessarily <= original value). 310 The nb of bytes decompressed into dstBuffer will be written into *dstSizePtr (necessarily <= original value). 311 312 The function does not necessarily read all input bytes, so always check value in *srcSizePtr. 313 Unconsumed source data must be presented again in subsequent invocations. 314 315 `dstBuffer` can freely change between each consecutive function invocation. 316 `dstBuffer` content will be overwritten. 317 318 @return : an hint of how many `srcSize` bytes LZ4F_decompress() expects for next call. 319 Schematically, it's the size of the current (or remaining) compressed block + header of next block. 320 Respecting the hint provides some small speed benefit, because it skips intermediate buffers. 321 This is just a hint though, it's always possible to provide any srcSize. 322 323 When a frame is fully decoded, @return will be 0 (no more data expected). 324 When provided with more bytes than necessary to decode a frame, 325 LZ4F_decompress() will stop reading exactly at end of current frame, and @return 0. 326 327 If decompression failed, @return is an error code, which can be tested using LZ4F_isError(). 328 After a decompression error, the `dctx` context is not resumable. 329 Use LZ4F_resetDecompressionContext() to return to clean state. 330 331 After a frame is fully decoded, dctx can be used again to decompress another frame. 332 333</p></pre><BR> 334 335<pre><b>void LZ4F_resetDecompressionContext(LZ4F_dctx* dctx); </b>/* always successful */<b> 336</b><p> In case of an error, the context is left in "undefined" state. 337 In which case, it's necessary to reset it, before re-using it. 338 This method can also be used to abruptly stop any unfinished decompression, 339 and start a new one using same context resources. 340</p></pre><BR> 341 342<pre><b>typedef enum { LZ4F_LIST_ERRORS(LZ4F_GENERATE_ENUM) 343 _LZ4F_dummy_error_enum_for_c89_never_used } LZ4F_errorCodes; 344</b></pre><BR> 345<a name="Chapter11"></a><h2>Bulk processing dictionary API</h2><pre></pre> 346 347<pre><b>LZ4FLIB_STATIC_API LZ4F_CDict* LZ4F_createCDict(const void* dictBuffer, size_t dictSize); 348LZ4FLIB_STATIC_API void LZ4F_freeCDict(LZ4F_CDict* CDict); 349</b><p> When compressing multiple messages / blocks using the same dictionary, it's recommended to load it just once. 350 LZ4_createCDict() will create a digested dictionary, ready to start future compression operations without startup delay. 351 LZ4_CDict can be created once and shared by multiple threads concurrently, since its usage is read-only. 352 `dictBuffer` can be released after LZ4_CDict creation, since its content is copied within CDict 353</p></pre><BR> 354 355<pre><b>LZ4FLIB_STATIC_API size_t LZ4F_compressFrame_usingCDict( 356 LZ4F_cctx* cctx, 357 void* dst, size_t dstCapacity, 358 const void* src, size_t srcSize, 359 const LZ4F_CDict* cdict, 360 const LZ4F_preferences_t* preferencesPtr); 361</b><p> Compress an entire srcBuffer into a valid LZ4 frame using a digested Dictionary. 362 cctx must point to a context created by LZ4F_createCompressionContext(). 363 If cdict==NULL, compress without a dictionary. 364 dstBuffer MUST be >= LZ4F_compressFrameBound(srcSize, preferencesPtr). 365 If this condition is not respected, function will fail (@return an errorCode). 366 The LZ4F_preferences_t structure is optional : you may provide NULL as argument, 367 but it's not recommended, as it's the only way to provide dictID in the frame header. 368 @return : number of bytes written into dstBuffer. 369 or an error code if it fails (can be tested using LZ4F_isError()) 370</p></pre><BR> 371 372<pre><b>LZ4FLIB_STATIC_API size_t LZ4F_compressBegin_usingCDict( 373 LZ4F_cctx* cctx, 374 void* dstBuffer, size_t dstCapacity, 375 const LZ4F_CDict* cdict, 376 const LZ4F_preferences_t* prefsPtr); 377</b><p> Inits streaming dictionary compression, and writes the frame header into dstBuffer. 378 dstCapacity must be >= LZ4F_HEADER_SIZE_MAX bytes. 379 `prefsPtr` is optional : you may provide NULL as argument, 380 however, it's the only way to provide dictID in the frame header. 381 @return : number of bytes written into dstBuffer for the header, 382 or an error code (which can be tested using LZ4F_isError()) 383</p></pre><BR> 384 385<pre><b>LZ4FLIB_STATIC_API size_t LZ4F_decompress_usingDict( 386 LZ4F_dctx* dctxPtr, 387 void* dstBuffer, size_t* dstSizePtr, 388 const void* srcBuffer, size_t* srcSizePtr, 389 const void* dict, size_t dictSize, 390 const LZ4F_decompressOptions_t* decompressOptionsPtr); 391</b><p> Same as LZ4F_decompress(), using a predefined dictionary. 392 Dictionary is used "in place", without any preprocessing. 393 It must remain accessible throughout the entire frame decoding. 394</p></pre><BR> 395 396</html> 397</body> 398
