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">Version</a></li> 13<li><a href="#Chapter3">Tuning parameter</a></li> 14<li><a href="#Chapter4">Simple Functions</a></li> 15<li><a href="#Chapter5">Advanced Functions</a></li> 16<li><a href="#Chapter6">Streaming Compression Functions</a></li> 17<li><a href="#Chapter7">Streaming Decompression Functions</a></li> 18<li><a href="#Chapter8">Experimental section</a></li> 19<li><a href="#Chapter9">Private Definitions</a></li> 20<li><a href="#Chapter10">Obsolete Functions</a></li> 21</ol> 22<hr> 23<a name="Chapter1"></a><h2>Introduction</h2><pre> 24 LZ4 is lossless compression algorithm, providing compression speed >500 MB/s per core, 25 scalable with multi-cores CPU. It features an extremely fast decoder, with speed in 26 multiple GB/s per core, typically reaching RAM speed limits on multi-core systems. 27 28 The LZ4 compression library provides in-memory compression and decompression functions. 29 It gives full buffer control to user. 30 Compression can be done in: 31 - a single step (described as Simple Functions) 32 - a single step, reusing a context (described in Advanced Functions) 33 - unbounded multiple steps (described as Streaming compression) 34 35 lz4.h generates and decodes LZ4-compressed blocks (doc/lz4_Block_format.md). 36 Decompressing such a compressed block requires additional metadata. 37 Exact metadata depends on exact decompression function. 38 For the typical case of LZ4_decompress_safe(), 39 metadata includes block's compressed size, and maximum bound of decompressed size. 40 Each application is free to encode and pass such metadata in whichever way it wants. 41 42 lz4.h only handle blocks, it can not generate Frames. 43 44 Blocks are different from Frames (doc/lz4_Frame_format.md). 45 Frames bundle both blocks and metadata in a specified manner. 46 Embedding metadata is required for compressed data to be self-contained and portable. 47 Frame format is delivered through a companion API, declared in lz4frame.h. 48 The `lz4` CLI can only manage frames. 49<BR></pre> 50 51<a name="Chapter2"></a><h2>Version</h2><pre></pre> 52 53<pre><b>int LZ4_versionNumber (void); </b>/**< library version number; useful to check dll version */<b> 54</b></pre><BR> 55<pre><b>const char* LZ4_versionString (void); </b>/**< library version string; useful to check dll version */<b> 56</b></pre><BR> 57<a name="Chapter3"></a><h2>Tuning parameter</h2><pre></pre> 58 59<pre><b>#ifndef LZ4_MEMORY_USAGE 60# define LZ4_MEMORY_USAGE 14 61#endif 62</b><p> Memory usage formula : N->2^N Bytes (examples : 10 -> 1KB; 12 -> 4KB ; 16 -> 64KB; 20 -> 1MB; etc.) 63 Increasing memory usage improves compression ratio. 64 Reduced memory usage may improve speed, thanks to better cache locality. 65 Default value is 14, for 16KB, which nicely fits into Intel x86 L1 cache 66 67</p></pre><BR> 68 69<a name="Chapter4"></a><h2>Simple Functions</h2><pre></pre> 70 71<pre><b>int LZ4_compress_default(const char* src, char* dst, int srcSize, int dstCapacity); 72</b><p> Compresses 'srcSize' bytes from buffer 'src' 73 into already allocated 'dst' buffer of size 'dstCapacity'. 74 Compression is guaranteed to succeed if 'dstCapacity' >= LZ4_compressBound(srcSize). 75 It also runs faster, so it's a recommended setting. 76 If the function cannot compress 'src' into a more limited 'dst' budget, 77 compression stops *immediately*, and the function result is zero. 78 In which case, 'dst' content is undefined (invalid). 79 srcSize : max supported value is LZ4_MAX_INPUT_SIZE. 80 dstCapacity : size of buffer 'dst' (which must be already allocated) 81 @return : the number of bytes written into buffer 'dst' (necessarily <= dstCapacity) 82 or 0 if compression fails 83 Note : This function is protected against buffer overflow scenarios (never writes outside 'dst' buffer, nor read outside 'source' buffer). 84 85</p></pre><BR> 86 87<pre><b>int LZ4_decompress_safe (const char* src, char* dst, int compressedSize, int dstCapacity); 88</b><p> compressedSize : is the exact complete size of the compressed block. 89 dstCapacity : is the size of destination buffer (which must be already allocated), presumed an upper bound of decompressed size. 90 @return : the number of bytes decompressed into destination buffer (necessarily <= dstCapacity) 91 If destination buffer is not large enough, decoding will stop and output an error code (negative value). 92 If the source stream is detected malformed, the function will stop decoding and return a negative result. 93 Note 1 : This function is protected against malicious data packets : 94 it will never writes outside 'dst' buffer, nor read outside 'source' buffer, 95 even if the compressed block is maliciously modified to order the decoder to do these actions. 96 In such case, the decoder stops immediately, and considers the compressed block malformed. 97 Note 2 : compressedSize and dstCapacity must be provided to the function, the compressed block does not contain them. 98 The implementation is free to send / store / derive this information in whichever way is most beneficial. 99 If there is a need for a different format which bundles together both compressed data and its metadata, consider looking at lz4frame.h instead. 100 101</p></pre><BR> 102 103<a name="Chapter5"></a><h2>Advanced Functions</h2><pre></pre> 104 105<pre><b>int LZ4_compressBound(int inputSize); 106</b><p> Provides the maximum size that LZ4 compression may output in a "worst case" scenario (input data not compressible) 107 This function is primarily useful for memory allocation purposes (destination buffer size). 108 Macro LZ4_COMPRESSBOUND() is also provided for compilation-time evaluation (stack memory allocation for example). 109 Note that LZ4_compress_default() compresses faster when dstCapacity is >= LZ4_compressBound(srcSize) 110 inputSize : max supported value is LZ4_MAX_INPUT_SIZE 111 return : maximum output size in a "worst case" scenario 112 or 0, if input size is incorrect (too large or negative) 113</p></pre><BR> 114 115<pre><b>int LZ4_compress_fast (const char* src, char* dst, int srcSize, int dstCapacity, int acceleration); 116</b><p> Same as LZ4_compress_default(), but allows selection of "acceleration" factor. 117 The larger the acceleration value, the faster the algorithm, but also the lesser the compression. 118 It's a trade-off. It can be fine tuned, with each successive value providing roughly +~3% to speed. 119 An acceleration value of "1" is the same as regular LZ4_compress_default() 120 Values <= 0 will be replaced by LZ4_ACCELERATION_DEFAULT (currently == 1, see lz4.c). 121 Values > LZ4_ACCELERATION_MAX will be replaced by LZ4_ACCELERATION_MAX (currently == 65537, see lz4.c). 122</p></pre><BR> 123 124<pre><b>int LZ4_sizeofState(void); 125int LZ4_compress_fast_extState (void* state, const char* src, char* dst, int srcSize, int dstCapacity, int acceleration); 126</b><p> Same as LZ4_compress_fast(), using an externally allocated memory space for its state. 127 Use LZ4_sizeofState() to know how much memory must be allocated, 128 and allocate it on 8-bytes boundaries (using `malloc()` typically). 129 Then, provide this buffer as `void* state` to compression function. 130 131</p></pre><BR> 132 133<pre><b>int LZ4_compress_destSize (const char* src, char* dst, int* srcSizePtr, int targetDstSize); 134</b><p> Reverse the logic : compresses as much data as possible from 'src' buffer 135 into already allocated buffer 'dst', of size >= 'targetDestSize'. 136 This function either compresses the entire 'src' content into 'dst' if it's large enough, 137 or fill 'dst' buffer completely with as much data as possible from 'src'. 138 note: acceleration parameter is fixed to "default". 139 140 *srcSizePtr : will be modified to indicate how many bytes where read from 'src' to fill 'dst'. 141 New value is necessarily <= input value. 142 @return : Nb bytes written into 'dst' (necessarily <= targetDestSize) 143 or 0 if compression fails. 144 145 Note : from v1.8.2 to v1.9.1, this function had a bug (fixed un v1.9.2+): 146 the produced compressed content could, in specific circumstances, 147 require to be decompressed into a destination buffer larger 148 by at least 1 byte than the content to decompress. 149 If an application uses `LZ4_compress_destSize()`, 150 it's highly recommended to update liblz4 to v1.9.2 or better. 151 If this can't be done or ensured, 152 the receiving decompression function should provide 153 a dstCapacity which is > decompressedSize, by at least 1 byte. 154 See https://github.com/lz4/lz4/issues/859 for details 155 156</p></pre><BR> 157 158<pre><b>int LZ4_decompress_safe_partial (const char* src, char* dst, int srcSize, int targetOutputSize, int dstCapacity); 159</b><p> Decompress an LZ4 compressed block, of size 'srcSize' at position 'src', 160 into destination buffer 'dst' of size 'dstCapacity'. 161 Up to 'targetOutputSize' bytes will be decoded. 162 The function stops decoding on reaching this objective. 163 This can be useful to boost performance 164 whenever only the beginning of a block is required. 165 166 @return : the number of bytes decoded in `dst` (necessarily <= targetOutputSize) 167 If source stream is detected malformed, function returns a negative result. 168 169 Note 1 : @return can be < targetOutputSize, if compressed block contains less data. 170 171 Note 2 : targetOutputSize must be <= dstCapacity 172 173 Note 3 : this function effectively stops decoding on reaching targetOutputSize, 174 so dstCapacity is kind of redundant. 175 This is because in older versions of this function, 176 decoding operation would still write complete sequences. 177 Therefore, there was no guarantee that it would stop writing at exactly targetOutputSize, 178 it could write more bytes, though only up to dstCapacity. 179 Some "margin" used to be required for this operation to work properly. 180 Thankfully, this is no longer necessary. 181 The function nonetheless keeps the same signature, in an effort to preserve API compatibility. 182 183 Note 4 : If srcSize is the exact size of the block, 184 then targetOutputSize can be any value, 185 including larger than the block's decompressed size. 186 The function will, at most, generate block's decompressed size. 187 188 Note 5 : If srcSize is _larger_ than block's compressed size, 189 then targetOutputSize **MUST** be <= block's decompressed size. 190 Otherwise, *silent corruption will occur*. 191 192</p></pre><BR> 193 194<a name="Chapter6"></a><h2>Streaming Compression Functions</h2><pre></pre> 195 196<pre><b>void LZ4_resetStream_fast (LZ4_stream_t* streamPtr); 197</b><p> Use this to prepare an LZ4_stream_t for a new chain of dependent blocks 198 (e.g., LZ4_compress_fast_continue()). 199 200 An LZ4_stream_t must be initialized once before usage. 201 This is automatically done when created by LZ4_createStream(). 202 However, should the LZ4_stream_t be simply declared on stack (for example), 203 it's necessary to initialize it first, using LZ4_initStream(). 204 205 After init, start any new stream with LZ4_resetStream_fast(). 206 A same LZ4_stream_t can be re-used multiple times consecutively 207 and compress multiple streams, 208 provided that it starts each new stream with LZ4_resetStream_fast(). 209 210 LZ4_resetStream_fast() is much faster than LZ4_initStream(), 211 but is not compatible with memory regions containing garbage data. 212 213 Note: it's only useful to call LZ4_resetStream_fast() 214 in the context of streaming compression. 215 The *extState* functions perform their own resets. 216 Invoking LZ4_resetStream_fast() before is redundant, and even counterproductive. 217 218</p></pre><BR> 219 220<pre><b>int LZ4_loadDict (LZ4_stream_t* streamPtr, const char* dictionary, int dictSize); 221</b><p> Use this function to reference a static dictionary into LZ4_stream_t. 222 The dictionary must remain available during compression. 223 LZ4_loadDict() triggers a reset, so any previous data will be forgotten. 224 The same dictionary will have to be loaded on decompression side for successful decoding. 225 Dictionary are useful for better compression of small data (KB range). 226 While LZ4 accept any input as dictionary, 227 results are generally better when using Zstandard's Dictionary Builder. 228 Loading a size of 0 is allowed, and is the same as reset. 229 @return : loaded dictionary size, in bytes (necessarily <= 64 KB) 230 231</p></pre><BR> 232 233<pre><b>int LZ4_compress_fast_continue (LZ4_stream_t* streamPtr, const char* src, char* dst, int srcSize, int dstCapacity, int acceleration); 234</b><p> Compress 'src' content using data from previously compressed blocks, for better compression ratio. 235 'dst' buffer must be already allocated. 236 If dstCapacity >= LZ4_compressBound(srcSize), compression is guaranteed to succeed, and runs faster. 237 238 @return : size of compressed block 239 or 0 if there is an error (typically, cannot fit into 'dst'). 240 241 Note 1 : Each invocation to LZ4_compress_fast_continue() generates a new block. 242 Each block has precise boundaries. 243 Each block must be decompressed separately, calling LZ4_decompress_*() with relevant metadata. 244 It's not possible to append blocks together and expect a single invocation of LZ4_decompress_*() to decompress them together. 245 246 Note 2 : The previous 64KB of source data is __assumed__ to remain present, unmodified, at same address in memory ! 247 248 Note 3 : When input is structured as a double-buffer, each buffer can have any size, including < 64 KB. 249 Make sure that buffers are separated, by at least one byte. 250 This construction ensures that each block only depends on previous block. 251 252 Note 4 : If input buffer is a ring-buffer, it can have any size, including < 64 KB. 253 254 Note 5 : After an error, the stream status is undefined (invalid), it can only be reset or freed. 255 256</p></pre><BR> 257 258<pre><b>int LZ4_saveDict (LZ4_stream_t* streamPtr, char* safeBuffer, int maxDictSize); 259</b><p> If last 64KB data cannot be guaranteed to remain available at its current memory location, 260 save it into a safer place (char* safeBuffer). 261 This is schematically equivalent to a memcpy() followed by LZ4_loadDict(), 262 but is much faster, because LZ4_saveDict() doesn't need to rebuild tables. 263 @return : saved dictionary size in bytes (necessarily <= maxDictSize), or 0 if error. 264 265</p></pre><BR> 266 267<a name="Chapter7"></a><h2>Streaming Decompression Functions</h2><pre> Bufferless synchronous API 268<BR></pre> 269 270<pre><b>LZ4_streamDecode_t* LZ4_createStreamDecode(void); 271int LZ4_freeStreamDecode (LZ4_streamDecode_t* LZ4_stream); 272</b><p> creation / destruction of streaming decompression tracking context. 273 A tracking context can be re-used multiple times. 274 275</p></pre><BR> 276 277<pre><b>int LZ4_setStreamDecode (LZ4_streamDecode_t* LZ4_streamDecode, const char* dictionary, int dictSize); 278</b><p> An LZ4_streamDecode_t context can be allocated once and re-used multiple times. 279 Use this function to start decompression of a new stream of blocks. 280 A dictionary can optionally be set. Use NULL or size 0 for a reset order. 281 Dictionary is presumed stable : it must remain accessible and unmodified during next decompression. 282 @return : 1 if OK, 0 if error 283 284</p></pre><BR> 285 286<pre><b>int LZ4_decoderRingBufferSize(int maxBlockSize); 287#define LZ4_DECODER_RING_BUFFER_SIZE(maxBlockSize) (65536 + 14 + (maxBlockSize)) </b>/* for static allocation; maxBlockSize presumed valid */<b> 288</b><p> Note : in a ring buffer scenario (optional), 289 blocks are presumed decompressed next to each other 290 up to the moment there is not enough remaining space for next block (remainingSize < maxBlockSize), 291 at which stage it resumes from beginning of ring buffer. 292 When setting such a ring buffer for streaming decompression, 293 provides the minimum size of this ring buffer 294 to be compatible with any source respecting maxBlockSize condition. 295 @return : minimum ring buffer size, 296 or 0 if there is an error (invalid maxBlockSize). 297 298</p></pre><BR> 299 300<pre><b>int LZ4_decompress_safe_continue (LZ4_streamDecode_t* LZ4_streamDecode, const char* src, char* dst, int srcSize, int dstCapacity); 301</b><p> These decoding functions allow decompression of consecutive blocks in "streaming" mode. 302 A block is an unsplittable entity, it must be presented entirely to a decompression function. 303 Decompression functions only accepts one block at a time. 304 The last 64KB of previously decoded data *must* remain available and unmodified at the memory position where they were decoded. 305 If less than 64KB of data has been decoded, all the data must be present. 306 307 Special : if decompression side sets a ring buffer, it must respect one of the following conditions : 308 - Decompression buffer size is _at least_ LZ4_decoderRingBufferSize(maxBlockSize). 309 maxBlockSize is the maximum size of any single block. It can have any value > 16 bytes. 310 In which case, encoding and decoding buffers do not need to be synchronized. 311 Actually, data can be produced by any source compliant with LZ4 format specification, and respecting maxBlockSize. 312 - Synchronized mode : 313 Decompression buffer size is _exactly_ the same as compression buffer size, 314 and follows exactly same update rule (block boundaries at same positions), 315 and decoding function is provided with exact decompressed size of each block (exception for last block of the stream), 316 _then_ decoding & encoding ring buffer can have any size, including small ones ( < 64 KB). 317 - Decompression buffer is larger than encoding buffer, by a minimum of maxBlockSize more bytes. 318 In which case, encoding and decoding buffers do not need to be synchronized, 319 and encoding ring buffer can have any size, including small ones ( < 64 KB). 320 321 Whenever these conditions are not possible, 322 save the last 64KB of decoded data into a safe buffer where it can't be modified during decompression, 323 then indicate where this data is saved using LZ4_setStreamDecode(), before decompressing next block. 324</p></pre><BR> 325 326<pre><b>int LZ4_decompress_safe_usingDict (const char* src, char* dst, int srcSize, int dstCapcity, const char* dictStart, int dictSize); 327</b><p> These decoding functions work the same as 328 a combination of LZ4_setStreamDecode() followed by LZ4_decompress_*_continue() 329 They are stand-alone, and don't need an LZ4_streamDecode_t structure. 330 Dictionary is presumed stable : it must remain accessible and unmodified during decompression. 331 Performance tip : Decompression speed can be substantially increased 332 when dst == dictStart + dictSize. 333 334</p></pre><BR> 335 336<a name="Chapter8"></a><h2>Experimental section</h2><pre> 337 Symbols declared in this section must be considered unstable. Their 338 signatures or semantics may change, or they may be removed altogether in the 339 future. They are therefore only safe to depend on when the caller is 340 statically linked against the library. 341 342 To protect against unsafe usage, not only are the declarations guarded, 343 the definitions are hidden by default 344 when building LZ4 as a shared/dynamic library. 345 346 In order to access these declarations, 347 define LZ4_STATIC_LINKING_ONLY in your application 348 before including LZ4's headers. 349 350 In order to make their implementations accessible dynamically, you must 351 define LZ4_PUBLISH_STATIC_FUNCTIONS when building the LZ4 library. 352<BR></pre> 353 354<pre><b>LZ4LIB_STATIC_API int LZ4_compress_fast_extState_fastReset (void* state, const char* src, char* dst, int srcSize, int dstCapacity, int acceleration); 355</b><p> A variant of LZ4_compress_fast_extState(). 356 357 Using this variant avoids an expensive initialization step. 358 It is only safe to call if the state buffer is known to be correctly initialized already 359 (see above comment on LZ4_resetStream_fast() for a definition of "correctly initialized"). 360 From a high level, the difference is that 361 this function initializes the provided state with a call to something like LZ4_resetStream_fast() 362 while LZ4_compress_fast_extState() starts with a call to LZ4_resetStream(). 363 364</p></pre><BR> 365 366<pre><b>LZ4LIB_STATIC_API void LZ4_attach_dictionary(LZ4_stream_t* workingStream, const LZ4_stream_t* dictionaryStream); 367</b><p> This is an experimental API that allows 368 efficient use of a static dictionary many times. 369 370 Rather than re-loading the dictionary buffer into a working context before 371 each compression, or copying a pre-loaded dictionary's LZ4_stream_t into a 372 working LZ4_stream_t, this function introduces a no-copy setup mechanism, 373 in which the working stream references the dictionary stream in-place. 374 375 Several assumptions are made about the state of the dictionary stream. 376 Currently, only streams which have been prepared by LZ4_loadDict() should 377 be expected to work. 378 379 Alternatively, the provided dictionaryStream may be NULL, 380 in which case any existing dictionary stream is unset. 381 382 If a dictionary is provided, it replaces any pre-existing stream history. 383 The dictionary contents are the only history that can be referenced and 384 logically immediately precede the data compressed in the first subsequent 385 compression call. 386 387 The dictionary will only remain attached to the working stream through the 388 first compression call, at the end of which it is cleared. The dictionary 389 stream (and source buffer) must remain in-place / accessible / unchanged 390 through the completion of the first compression call on the stream. 391 392</p></pre><BR> 393 394<pre><b></b><p> 395 It's possible to have input and output sharing the same buffer, 396 for highly contrained memory environments. 397 In both cases, it requires input to lay at the end of the buffer, 398 and decompression to start at beginning of the buffer. 399 Buffer size must feature some margin, hence be larger than final size. 400 401 |<------------------------buffer--------------------------------->| 402 |<-----------compressed data--------->| 403 |<-----------decompressed size------------------>| 404 |<----margin---->| 405 406 This technique is more useful for decompression, 407 since decompressed size is typically larger, 408 and margin is short. 409 410 In-place decompression will work inside any buffer 411 which size is >= LZ4_DECOMPRESS_INPLACE_BUFFER_SIZE(decompressedSize). 412 This presumes that decompressedSize > compressedSize. 413 Otherwise, it means compression actually expanded data, 414 and it would be more efficient to store such data with a flag indicating it's not compressed. 415 This can happen when data is not compressible (already compressed, or encrypted). 416 417 For in-place compression, margin is larger, as it must be able to cope with both 418 history preservation, requiring input data to remain unmodified up to LZ4_DISTANCE_MAX, 419 and data expansion, which can happen when input is not compressible. 420 As a consequence, buffer size requirements are much higher, 421 and memory savings offered by in-place compression are more limited. 422 423 There are ways to limit this cost for compression : 424 - Reduce history size, by modifying LZ4_DISTANCE_MAX. 425 Note that it is a compile-time constant, so all compressions will apply this limit. 426 Lower values will reduce compression ratio, except when input_size < LZ4_DISTANCE_MAX, 427 so it's a reasonable trick when inputs are known to be small. 428 - Require the compressor to deliver a "maximum compressed size". 429 This is the `dstCapacity` parameter in `LZ4_compress*()`. 430 When this size is < LZ4_COMPRESSBOUND(inputSize), then compression can fail, 431 in which case, the return code will be 0 (zero). 432 The caller must be ready for these cases to happen, 433 and typically design a backup scheme to send data uncompressed. 434 The combination of both techniques can significantly reduce 435 the amount of margin required for in-place compression. 436 437 In-place compression can work in any buffer 438 which size is >= (maxCompressedSize) 439 with maxCompressedSize == LZ4_COMPRESSBOUND(srcSize) for guaranteed compression success. 440 LZ4_COMPRESS_INPLACE_BUFFER_SIZE() depends on both maxCompressedSize and LZ4_DISTANCE_MAX, 441 so it's possible to reduce memory requirements by playing with them. 442 443</p></pre><BR> 444 445<pre><b>#define LZ4_DECOMPRESS_INPLACE_BUFFER_SIZE(decompressedSize) ((decompressedSize) + LZ4_DECOMPRESS_INPLACE_MARGIN(decompressedSize)) </b>/**< note: presumes that compressedSize < decompressedSize. note2: margin is overestimated a bit, since it could use compressedSize instead */<b> 446</b></pre><BR> 447<pre><b>#define LZ4_COMPRESS_INPLACE_BUFFER_SIZE(maxCompressedSize) ((maxCompressedSize) + LZ4_COMPRESS_INPLACE_MARGIN) </b>/**< maxCompressedSize is generally LZ4_COMPRESSBOUND(inputSize), but can be set to any lower value, with the risk that compression can fail (return code 0(zero)) */<b> 448</b></pre><BR> 449<a name="Chapter9"></a><h2>Private Definitions</h2><pre> 450 Do not use these definitions directly. 451 They are only exposed to allow static allocation of `LZ4_stream_t` and `LZ4_streamDecode_t`. 452 Accessing members will expose user code to API and/or ABI break in future versions of the library. 453<BR></pre> 454 455<pre><b>typedef struct { 456 const LZ4_byte* externalDict; 457 size_t extDictSize; 458 const LZ4_byte* prefixEnd; 459 size_t prefixSize; 460} LZ4_streamDecode_t_internal; 461</b></pre><BR> 462<pre><b>#define LZ4_STREAMSIZE 16416 </b>/* static size, for inter-version compatibility */<b> 463#define LZ4_STREAMSIZE_VOIDP (LZ4_STREAMSIZE / sizeof(void*)) 464union LZ4_stream_u { 465 void* table[LZ4_STREAMSIZE_VOIDP]; 466 LZ4_stream_t_internal internal_donotuse; 467}; </b>/* previously typedef'd to LZ4_stream_t */<b> 468</b><p> Do not use below internal definitions directly ! 469 Declare or allocate an LZ4_stream_t instead. 470 LZ4_stream_t can also be created using LZ4_createStream(), which is recommended. 471 The structure definition can be convenient for static allocation 472 (on stack, or as part of larger structure). 473 Init this structure with LZ4_initStream() before first use. 474 note : only use this definition in association with static linking ! 475 this definition is not API/ABI safe, and may change in future versions. 476 477</p></pre><BR> 478 479<pre><b>LZ4_stream_t* LZ4_initStream (void* buffer, size_t size); 480</b><p> An LZ4_stream_t structure must be initialized at least once. 481 This is automatically done when invoking LZ4_createStream(), 482 but it's not when the structure is simply declared on stack (for example). 483 484 Use LZ4_initStream() to properly initialize a newly declared LZ4_stream_t. 485 It can also initialize any arbitrary buffer of sufficient size, 486 and will @return a pointer of proper type upon initialization. 487 488 Note : initialization fails if size and alignment conditions are not respected. 489 In which case, the function will @return NULL. 490 Note2: An LZ4_stream_t structure guarantees correct alignment and size. 491 Note3: Before v1.9.0, use LZ4_resetStream() instead 492 493</p></pre><BR> 494 495<pre><b>#define LZ4_STREAMDECODESIZE_U64 (4 + ((sizeof(void*)==16) ? 2 : 0) </b>/*AS-400*/ )<b> 496#define LZ4_STREAMDECODESIZE (LZ4_STREAMDECODESIZE_U64 * sizeof(unsigned long long)) 497union LZ4_streamDecode_u { 498 unsigned long long table[LZ4_STREAMDECODESIZE_U64]; 499 LZ4_streamDecode_t_internal internal_donotuse; 500} ; </b>/* previously typedef'd to LZ4_streamDecode_t */<b> 501</b><p> information structure to track an LZ4 stream during decompression. 502 init this structure using LZ4_setStreamDecode() before first use. 503 note : only use in association with static linking ! 504 this definition is not API/ABI safe, 505 and may change in a future version ! 506 507</p></pre><BR> 508 509<a name="Chapter10"></a><h2>Obsolete Functions</h2><pre></pre> 510 511<pre><b>#ifdef LZ4_DISABLE_DEPRECATE_WARNINGS 512# define LZ4_DEPRECATED(message) </b>/* disable deprecation warnings */<b> 513#else 514# if defined (__cplusplus) && (__cplusplus >= 201402) </b>/* C++14 or greater */<b> 515# define LZ4_DEPRECATED(message) [[deprecated(message)]] 516# elif defined(_MSC_VER) 517# define LZ4_DEPRECATED(message) __declspec(deprecated(message)) 518# elif defined(__clang__) || (defined(__GNUC__) && (__GNUC__ * 10 + __GNUC_MINOR__ >= 45)) 519# define LZ4_DEPRECATED(message) __attribute__((deprecated(message))) 520# elif defined(__GNUC__) && (__GNUC__ * 10 + __GNUC_MINOR__ >= 31) 521# define LZ4_DEPRECATED(message) __attribute__((deprecated)) 522# else 523# pragma message("WARNING: LZ4_DEPRECATED needs custom implementation for this compiler") 524# define LZ4_DEPRECATED(message) </b>/* disabled */<b> 525# endif 526#endif </b>/* LZ4_DISABLE_DEPRECATE_WARNINGS */<b> 527</b><p> 528 Deprecated functions make the compiler generate a warning when invoked. 529 This is meant to invite users to update their source code. 530 Should deprecation warnings be a problem, it is generally possible to disable them, 531 typically with -Wno-deprecated-declarations for gcc 532 or _CRT_SECURE_NO_WARNINGS in Visual. 533 534 Another method is to define LZ4_DISABLE_DEPRECATE_WARNINGS 535 before including the header file. 536 537</p></pre><BR> 538 539<pre><b>LZ4_DEPRECATED("use LZ4_compress_default() instead") LZ4LIB_API int LZ4_compress (const char* src, char* dest, int srcSize); 540LZ4_DEPRECATED("use LZ4_compress_default() instead") LZ4LIB_API int LZ4_compress_limitedOutput (const char* src, char* dest, int srcSize, int maxOutputSize); 541LZ4_DEPRECATED("use LZ4_compress_fast_extState() instead") LZ4LIB_API int LZ4_compress_withState (void* state, const char* source, char* dest, int inputSize); 542LZ4_DEPRECATED("use LZ4_compress_fast_extState() instead") LZ4LIB_API int LZ4_compress_limitedOutput_withState (void* state, const char* source, char* dest, int inputSize, int maxOutputSize); 543LZ4_DEPRECATED("use LZ4_compress_fast_continue() instead") LZ4LIB_API int LZ4_compress_continue (LZ4_stream_t* LZ4_streamPtr, const char* source, char* dest, int inputSize); 544LZ4_DEPRECATED("use LZ4_compress_fast_continue() instead") LZ4LIB_API int LZ4_compress_limitedOutput_continue (LZ4_stream_t* LZ4_streamPtr, const char* source, char* dest, int inputSize, int maxOutputSize); 545</b><p></p></pre><BR> 546 547<pre><b>LZ4_DEPRECATED("use LZ4_decompress_fast() instead") LZ4LIB_API int LZ4_uncompress (const char* source, char* dest, int outputSize); 548LZ4_DEPRECATED("use LZ4_decompress_safe() instead") LZ4LIB_API int LZ4_uncompress_unknownOutputSize (const char* source, char* dest, int isize, int maxOutputSize); 549</b><p></p></pre><BR> 550 551<pre><b>LZ4_DEPRECATED("use LZ4_decompress_safe_usingDict() instead") LZ4LIB_API int LZ4_decompress_safe_withPrefix64k (const char* src, char* dst, int compressedSize, int maxDstSize); 552LZ4_DEPRECATED("use LZ4_decompress_fast_usingDict() instead") LZ4LIB_API int LZ4_decompress_fast_withPrefix64k (const char* src, char* dst, int originalSize); 553</b><p></p></pre><BR> 554 555<pre><b>LZ4_DEPRECATED("This function is deprecated and unsafe. Consider using LZ4_decompress_safe() instead") 556int LZ4_decompress_fast (const char* src, char* dst, int originalSize); 557LZ4_DEPRECATED("This function is deprecated and unsafe. Consider using LZ4_decompress_safe_continue() instead") 558int LZ4_decompress_fast_continue (LZ4_streamDecode_t* LZ4_streamDecode, const char* src, char* dst, int originalSize); 559LZ4_DEPRECATED("This function is deprecated and unsafe. Consider using LZ4_decompress_safe_usingDict() instead") 560int LZ4_decompress_fast_usingDict (const char* src, char* dst, int originalSize, const char* dictStart, int dictSize); 561</b><p> These functions used to be faster than LZ4_decompress_safe(), 562 but this is no longer the case. They are now slower. 563 This is because LZ4_decompress_fast() doesn't know the input size, 564 and therefore must progress more cautiously into the input buffer to not read beyond the end of block. 565 On top of that `LZ4_decompress_fast()` is not protected vs malformed or malicious inputs, making it a security liability. 566 As a consequence, LZ4_decompress_fast() is strongly discouraged, and deprecated. 567 568 The last remaining LZ4_decompress_fast() specificity is that 569 it can decompress a block without knowing its compressed size. 570 Such functionality can be achieved in a more secure manner 571 by employing LZ4_decompress_safe_partial(). 572 573 Parameters: 574 originalSize : is the uncompressed size to regenerate. 575 `dst` must be already allocated, its size must be >= 'originalSize' bytes. 576 @return : number of bytes read from source buffer (== compressed size). 577 The function expects to finish at block's end exactly. 578 If the source stream is detected malformed, the function stops decoding and returns a negative result. 579 note : LZ4_decompress_fast*() requires originalSize. Thanks to this information, it never writes past the output buffer. 580 However, since it doesn't know its 'src' size, it may read an unknown amount of input, past input buffer bounds. 581 Also, since match offsets are not validated, match reads from 'src' may underflow too. 582 These issues never happen if input (compressed) data is correct. 583 But they may happen if input data is invalid (error or intentional tampering). 584 As a consequence, use these functions in trusted environments with trusted data **only**. 585 586</p></pre><BR> 587 588<pre><b>void LZ4_resetStream (LZ4_stream_t* streamPtr); 589</b><p> An LZ4_stream_t structure must be initialized at least once. 590 This is done with LZ4_initStream(), or LZ4_resetStream(). 591 Consider switching to LZ4_initStream(), 592 invoking LZ4_resetStream() will trigger deprecation warnings in the future. 593 594</p></pre><BR> 595 596</html> 597</body> 598
