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2<head>
3<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
Yann Collet36df9052024-07-20 14:46:11 -0700[diff] [blame]4<title>1.10.0 Manual</title>
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]5</head>
6<body>
Yann Collet36df9052024-07-20 14:46:11 -0700[diff] [blame]7<h1>1.10.0 Manual</h1>
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]8<hr>
9<a name="Contents"></a><h2>Contents</h2>
10<ol>
11<li><a href="#Chapter1">Introduction</a></li>
Przemyslaw Skibinski6a5633e2017-01-23 16:03:40 +0100[diff] [blame]12<li><a href="#Chapter2">Version</a></li>
Yann Colleta2e4da32023-12-07 16:14:37 -0800[diff] [blame]13<li><a href="#Chapter3">Tuning memory usage</a></li>
Nick Terrell85aeb0e2016-11-11 13:00:02 -0800[diff] [blame]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>
Yann Collet50f01d82019-04-03 14:27:21 -0700[diff] [blame]18<li><a href="#Chapter8">Experimental section</a></li>
Yann Colletbe634552020-11-08 12:54:59 -0800[diff] [blame]19<li><a href="#Chapter9">Private Definitions</a></li>
Cyan497357afa362018-04-13 01:01:54 -0700[diff] [blame]20<li><a href="#Chapter10">Obsolete Functions</a></li>
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]21</ol>
22<hr>
23<a name="Chapter1"></a><h2>Introduction</h2><pre>
Yann Collet1d759572019-06-06 13:20:30 -0700[diff] [blame]24 LZ4 is lossless compression algorithm, providing compression speed >500 MB/s per core,
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]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.
Yann Collet21ff1a82019-04-12 11:27:44 -0700[diff] [blame]29 It gives full buffer control to user.
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]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
Yann Collet21ff1a82019-04-12 11:27:44 -0700[diff] [blame]35 lz4.h generates and decodes LZ4-compressed blocks (doc/lz4_Block_format.md).
Yann Collet1d759572019-06-06 13:20:30 -0700[diff] [blame]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.
Yann Collet21ff1a82019-04-12 11:27:44 -0700[diff] [blame]40 Each application is free to encode and pass such metadata in whichever way it wants.
Przemyslaw Skibinski6a5633e2017-01-23 16:03:40 +0100[diff] [blame]41
Yann Collet21ff1a82019-04-12 11:27:44 -0700[diff] [blame]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.
Yann Colletb17f5782019-05-29 12:06:13 -0700[diff] [blame]46 Embedding metadata is required for compressed data to be self-contained and portable.
Yann Collet21ff1a82019-04-12 11:27:44 -0700[diff] [blame]47 Frame format is delivered through a companion API, declared in lz4frame.h.
Yann Colletb17f5782019-05-29 12:06:13 -0700[diff] [blame]48 The `lz4` CLI can only manage frames.
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]49<BR></pre>
50
Yann Collet18b293d2022-08-11 14:06:17 -0700[diff] [blame]51<pre><b>#if defined(LZ4_FREESTANDING) && (LZ4_FREESTANDING == 1)
52# define LZ4_HEAPMODE 0
53# define LZ4HC_HEAPMODE 0
54# define LZ4_STATIC_LINKING_ONLY_DISABLE_MEMORY_ALLOCATION 1
55# if !defined(LZ4_memcpy)
56# error "LZ4_FREESTANDING requires macro 'LZ4_memcpy'."
57# endif
58# if !defined(LZ4_memset)
59# error "LZ4_FREESTANDING requires macro 'LZ4_memset'."
60# endif
61# if !defined(LZ4_memmove)
62# error "LZ4_FREESTANDING requires macro 'LZ4_memmove'."
63# endif
64#elif ! defined(LZ4_FREESTANDING)
65# define LZ4_FREESTANDING 0
66#endif
67</b><p> When this macro is set to 1, it enables "freestanding mode" that is
68 suitable for typical freestanding environment which doesn't support
69 standard C library.
70
71 - LZ4_FREESTANDING is a compile-time switch.
72 - It requires the following macros to be defined:
73 LZ4_memcpy, LZ4_memmove, LZ4_memset.
74 - It only enables LZ4/HC functions which don't use heap.
75 All LZ4F_* functions are not supported.
76 - See tests/freestanding.c to check its basic setup.
77
78</p></pre><BR>
79
Przemyslaw Skibinski6a5633e2017-01-23 16:03:40 +0100[diff] [blame]80<a name="Chapter2"></a><h2>Version</h2><pre></pre>
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]81
Yann Collet7deae4b2022-07-13 15:55:56 +0200[diff] [blame]82<pre><b>int LZ4_versionNumber (void); </b>/**< library version number; useful to check dll version; requires v1.3.0+ */<b>
Przemyslaw Skibinski6a5633e2017-01-23 16:03:40 +0100[diff] [blame]83</b></pre><BR>
Yann Collet7deae4b2022-07-13 15:55:56 +0200[diff] [blame]84<pre><b>const char* LZ4_versionString (void); </b>/**< library version string; useful to check dll version; requires v1.7.5+ */<b>
Przemyslaw Skibinski6a5633e2017-01-23 16:03:40 +0100[diff] [blame]85</b></pre><BR>
Yann Colleta2e4da32023-12-07 16:14:37 -0800[diff] [blame]86<a name="Chapter3"></a><h2>Tuning memory usage</h2><pre></pre>
Przemyslaw Skibinski6a5633e2017-01-23 16:03:40 +0100[diff] [blame]87
88<pre><b>#ifndef LZ4_MEMORY_USAGE
Yann Colletce8ee022022-04-17 10:06:18 -0700[diff] [blame]89# define LZ4_MEMORY_USAGE LZ4_MEMORY_USAGE_DEFAULT
Przemyslaw Skibinski6a5633e2017-01-23 16:03:40 +0100[diff] [blame]90#endif
Yann Collet36df9052024-07-20 14:46:11 -0700[diff] [blame]91</b><p> Can be selected at compile time, by setting LZ4_MEMORY_USAGE.
92 Memory usage formula : N->2^N Bytes (examples : 10 -> 1KB; 12 -> 4KB ; 16 -> 64KB; 20 -> 1MB)
Yann Colleta2e4da32023-12-07 16:14:37 -0800[diff] [blame]93 Increasing memory usage improves compression ratio, generally at the cost of speed.
Yann Colletce8ee022022-04-17 10:06:18 -0700[diff] [blame]94 Reduced memory usage may improve speed at the cost of ratio, thanks to better cache locality.
Yann Colleta2e4da32023-12-07 16:14:37 -0800[diff] [blame]95 Default value is 14, for 16KB, which nicely fits into most L1 caches.
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]96
97</p></pre><BR>
98
Nick Terrell85aeb0e2016-11-11 13:00:02 -0800[diff] [blame]99<a name="Chapter4"></a><h2>Simple Functions</h2><pre></pre>
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]100
Yann Colletda8bed42017-11-20 10:27:05 -0800[diff] [blame]101<pre><b>int LZ4_compress_default(const char* src, char* dst, int srcSize, int dstCapacity);
Yann Collet1d759572019-06-06 13:20:30 -0700[diff] [blame]102</b><p> Compresses 'srcSize' bytes from buffer 'src'
103 into already allocated 'dst' buffer of size 'dstCapacity'.
104 Compression is guaranteed to succeed if 'dstCapacity' >= LZ4_compressBound(srcSize).
105 It also runs faster, so it's a recommended setting.
106 If the function cannot compress 'src' into a more limited 'dst' budget,
107 compression stops *immediately*, and the function result is zero.
108 In which case, 'dst' content is undefined (invalid).
109 srcSize : max supported value is LZ4_MAX_INPUT_SIZE.
110 dstCapacity : size of buffer 'dst' (which must be already allocated)
111 @return : the number of bytes written into buffer 'dst' (necessarily <= dstCapacity)
112 or 0 if compression fails
113 Note : This function is protected against buffer overflow scenarios (never writes outside 'dst' buffer, nor read outside 'source' buffer).
114
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]115</p></pre><BR>
116
Yann Colletda8bed42017-11-20 10:27:05 -0800[diff] [blame]117<pre><b>int LZ4_decompress_safe (const char* src, char* dst, int compressedSize, int dstCapacity);
Yann Colleta2e4da32023-12-07 16:14:37 -0800[diff] [blame]118</b><p> @compressedSize : is the exact complete size of the compressed block.
119 @dstCapacity : is the size of destination buffer (which must be already allocated),
120 presumed an upper bound of decompressed size.
Yann Collet1d759572019-06-06 13:20:30 -0700[diff] [blame]121 @return : the number of bytes decompressed into destination buffer (necessarily <= dstCapacity)
122 If destination buffer is not large enough, decoding will stop and output an error code (negative value).
123 If the source stream is detected malformed, the function will stop decoding and return a negative result.
124 Note 1 : This function is protected against malicious data packets :
125 it will never writes outside 'dst' buffer, nor read outside 'source' buffer,
126 even if the compressed block is maliciously modified to order the decoder to do these actions.
127 In such case, the decoder stops immediately, and considers the compressed block malformed.
128 Note 2 : compressedSize and dstCapacity must be provided to the function, the compressed block does not contain them.
129 The implementation is free to send / store / derive this information in whichever way is most beneficial.
130 If there is a need for a different format which bundles together both compressed data and its metadata, consider looking at lz4frame.h instead.
131
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]132</p></pre><BR>
133
Nick Terrell85aeb0e2016-11-11 13:00:02 -0800[diff] [blame]134<a name="Chapter5"></a><h2>Advanced Functions</h2><pre></pre>
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]135
136<pre><b>int LZ4_compressBound(int inputSize);
137</b><p> Provides the maximum size that LZ4 compression may output in a "worst case" scenario (input data not compressible)
138 This function is primarily useful for memory allocation purposes (destination buffer size).
139 Macro LZ4_COMPRESSBOUND() is also provided for compilation-time evaluation (stack memory allocation for example).
Yann Colletea252502018-02-07 02:21:25 -0800[diff] [blame]140 Note that LZ4_compress_default() compresses faster when dstCapacity is >= LZ4_compressBound(srcSize)
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]141 inputSize : max supported value is LZ4_MAX_INPUT_SIZE
142 return : maximum output size in a "worst case" scenario
Yann Colletea252502018-02-07 02:21:25 -0800[diff] [blame]143 or 0, if input size is incorrect (too large or negative)
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]144</p></pre><BR>
145
Yann Colletda8bed42017-11-20 10:27:05 -0800[diff] [blame]146<pre><b>int LZ4_compress_fast (const char* src, char* dst, int srcSize, int dstCapacity, int acceleration);
Yann Colletea252502018-02-07 02:21:25 -0800[diff] [blame]147</b><p> Same as LZ4_compress_default(), but allows selection of "acceleration" factor.
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]148 The larger the acceleration value, the faster the algorithm, but also the lesser the compression.
149 It's a trade-off. It can be fine tuned, with each successive value providing roughly +~3% to speed.
150 An acceleration value of "1" is the same as regular LZ4_compress_default()
Yann Collet293713a2020-09-29 14:27:39 -0700[diff] [blame]151 Values <= 0 will be replaced by LZ4_ACCELERATION_DEFAULT (currently == 1, see lz4.c).
152 Values > LZ4_ACCELERATION_MAX will be replaced by LZ4_ACCELERATION_MAX (currently == 65537, see lz4.c).
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]153</p></pre><BR>
154
155<pre><b>int LZ4_sizeofState(void);
Yann Colletda8bed42017-11-20 10:27:05 -0800[diff] [blame]156int LZ4_compress_fast_extState (void* state, const char* src, char* dst, int srcSize, int dstCapacity, int acceleration);
Yann Colleta8032302018-09-13 16:02:11 -0700[diff] [blame]157</b><p> Same as LZ4_compress_fast(), using an externally allocated memory space for its state.
158 Use LZ4_sizeofState() to know how much memory must be allocated,
159 and allocate it on 8-bytes boundaries (using `malloc()` typically).
160 Then, provide this buffer as `void* state` to compression function.
161
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]162</p></pre><BR>
163
Yann Colletda5e8b72023-12-28 13:47:08 -0800[diff] [blame]164<pre><b>int LZ4_compress_destSize(const char* src, char* dst, int* srcSizePtr, int targetDstSize);
Yann Colleteaed9ea2018-09-07 16:21:31 -0700[diff] [blame]165</b><p> Reverse the logic : compresses as much data as possible from 'src' buffer
Yann Colletda5e8b72023-12-28 13:47:08 -0800[diff] [blame]166 into already allocated buffer 'dst', of size >= 'dstCapacity'.
Yann Colleteaed9ea2018-09-07 16:21:31 -0700[diff] [blame]167 This function either compresses the entire 'src' content into 'dst' if it's large enough,
168 or fill 'dst' buffer completely with as much data as possible from 'src'.
169 note: acceleration parameter is fixed to "default".
170
Yann Colletda5e8b72023-12-28 13:47:08 -0800[diff] [blame]171 *srcSizePtr : in+out parameter. Initially contains size of input.
172 Will be modified to indicate how many bytes where read from 'src' to fill 'dst'.
Yann Colleteaed9ea2018-09-07 16:21:31 -0700[diff] [blame]173 New value is necessarily <= input value.
Yann Colletda5e8b72023-12-28 13:47:08 -0800[diff] [blame]174 @return : Nb bytes written into 'dst' (necessarily <= dstCapacity)
Yann Colleteaed9ea2018-09-07 16:21:31 -0700[diff] [blame]175 or 0 if compression fails.
Yann Collet293713a2020-09-29 14:27:39 -0700[diff] [blame]176
Yann Colleta2e4da32023-12-07 16:14:37 -0800[diff] [blame]177 Note : from v1.8.2 to v1.9.1, this function had a bug (fixed in v1.9.2+):
Yann Collet293713a2020-09-29 14:27:39 -0700[diff] [blame]178 the produced compressed content could, in specific circumstances,
179 require to be decompressed into a destination buffer larger
180 by at least 1 byte than the content to decompress.
181 If an application uses `LZ4_compress_destSize()`,
182 it's highly recommended to update liblz4 to v1.9.2 or better.
183 If this can't be done or ensured,
184 the receiving decompression function should provide
185 a dstCapacity which is > decompressedSize, by at least 1 byte.
186 See https://github.com/lz4/lz4/issues/859 for details
187
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]188</p></pre><BR>
189
Yann Colletda8bed42017-11-20 10:27:05 -0800[diff] [blame]190<pre><b>int LZ4_decompress_safe_partial (const char* src, char* dst, int srcSize, int targetOutputSize, int dstCapacity);
Yann Colleteaed9ea2018-09-07 16:21:31 -0700[diff] [blame]191</b><p> Decompress an LZ4 compressed block, of size 'srcSize' at position 'src',
192 into destination buffer 'dst' of size 'dstCapacity'.
193 Up to 'targetOutputSize' bytes will be decoded.
Yann Collet293713a2020-09-29 14:27:39 -0700[diff] [blame]194 The function stops decoding on reaching this objective.
195 This can be useful to boost performance
196 whenever only the beginning of a block is required.
Yann Colleteaed9ea2018-09-07 16:21:31 -0700[diff] [blame]197
Yann Collet293713a2020-09-29 14:27:39 -0700[diff] [blame]198 @return : the number of bytes decoded in `dst` (necessarily <= targetOutputSize)
Yann Colleteaed9ea2018-09-07 16:21:31 -0700[diff] [blame]199 If source stream is detected malformed, function returns a negative result.
200
Yann Collet293713a2020-09-29 14:27:39 -0700[diff] [blame]201 Note 1 : @return can be < targetOutputSize, if compressed block contains less data.
Yann Colleteaed9ea2018-09-07 16:21:31 -0700[diff] [blame]202
Yann Collet293713a2020-09-29 14:27:39 -0700[diff] [blame]203 Note 2 : targetOutputSize must be <= dstCapacity
204
205 Note 3 : this function effectively stops decoding on reaching targetOutputSize,
Yann Colleteaed9ea2018-09-07 16:21:31 -0700[diff] [blame]206 so dstCapacity is kind of redundant.
Yann Collet293713a2020-09-29 14:27:39 -0700[diff] [blame]207 This is because in older versions of this function,
208 decoding operation would still write complete sequences.
209 Therefore, there was no guarantee that it would stop writing at exactly targetOutputSize,
Yann Colleteaed9ea2018-09-07 16:21:31 -0700[diff] [blame]210 it could write more bytes, though only up to dstCapacity.
211 Some "margin" used to be required for this operation to work properly.
Yann Collet293713a2020-09-29 14:27:39 -0700[diff] [blame]212 Thankfully, this is no longer necessary.
213 The function nonetheless keeps the same signature, in an effort to preserve API compatibility.
214
215 Note 4 : If srcSize is the exact size of the block,
216 then targetOutputSize can be any value,
217 including larger than the block's decompressed size.
218 The function will, at most, generate block's decompressed size.
219
220 Note 5 : If srcSize is _larger_ than block's compressed size,
221 then targetOutputSize **MUST** be <= block's decompressed size.
222 Otherwise, *silent corruption will occur*.
Yann Colleteaed9ea2018-09-07 16:21:31 -0700[diff] [blame]223
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]224</p></pre><BR>
225
Nick Terrell85aeb0e2016-11-11 13:00:02 -0800[diff] [blame]226<a name="Chapter6"></a><h2>Streaming Compression Functions</h2><pre></pre>
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]227
Yann Colleta2e4da32023-12-07 16:14:37 -0800[diff] [blame]228<pre><b>#if !defined(RC_INVOKED) </b>/* https://docs.microsoft.com/en-us/windows/win32/menurc/predefined-macros */<b>
229#if !defined(LZ4_STATIC_LINKING_ONLY_DISABLE_MEMORY_ALLOCATION)
230LZ4_stream_t* LZ4_createStream(void);
231int LZ4_freeStream (LZ4_stream_t* streamPtr);
232#endif </b>/* !defined(LZ4_STATIC_LINKING_ONLY_DISABLE_MEMORY_ALLOCATION) */<b>
233#endif
234</b><p>
235 - RC_INVOKED is predefined symbol of rc.exe (the resource compiler which is part of MSVC/Visual Studio).
236 https://docs.microsoft.com/en-us/windows/win32/menurc/predefined-macros
237
238 - Since rc.exe is a legacy compiler, it truncates long symbol (> 30 chars)
239 and reports warning "RC4011: identifier truncated".
240
241 - To eliminate the warning, we surround long preprocessor symbol with
242 "#if !defined(RC_INVOKED) ... #endif" block that means
243 "skip this block when rc.exe is trying to read it".
244</p></pre><BR>
245
Yann Collet2ece0d82019-04-05 12:54:13 -0700[diff] [blame]246<pre><b>void LZ4_resetStream_fast (LZ4_stream_t* streamPtr);
247</b><p> Use this to prepare an LZ4_stream_t for a new chain of dependent blocks
248 (e.g., LZ4_compress_fast_continue()).
249
Yann Collet14c71df2019-04-09 13:55:42 -0700[diff] [blame]250 An LZ4_stream_t must be initialized once before usage.
Yann Collet2ece0d82019-04-05 12:54:13 -0700[diff] [blame]251 This is automatically done when created by LZ4_createStream().
252 However, should the LZ4_stream_t be simply declared on stack (for example),
Yann Collet14c71df2019-04-09 13:55:42 -0700[diff] [blame]253 it's necessary to initialize it first, using LZ4_initStream().
Yann Collet2ece0d82019-04-05 12:54:13 -0700[diff] [blame]254
Yann Collet14c71df2019-04-09 13:55:42 -0700[diff] [blame]255 After init, start any new stream with LZ4_resetStream_fast().
Yann Collet2ece0d82019-04-05 12:54:13 -0700[diff] [blame]256 A same LZ4_stream_t can be re-used multiple times consecutively
257 and compress multiple streams,
258 provided that it starts each new stream with LZ4_resetStream_fast().
259
260 LZ4_resetStream_fast() is much faster than LZ4_initStream(),
261 but is not compatible with memory regions containing garbage data.
Yann Collet14c71df2019-04-09 13:55:42 -0700[diff] [blame]262
263 Note: it's only useful to call LZ4_resetStream_fast()
264 in the context of streaming compression.
265 The *extState* functions perform their own resets.
266 Invoking LZ4_resetStream_fast() before is redundant, and even counterproductive.
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]267
268</p></pre><BR>
269
270<pre><b>int LZ4_loadDict (LZ4_stream_t* streamPtr, const char* dictionary, int dictSize);
Yann Colletbcb26562019-04-11 15:19:48 -0700[diff] [blame]271</b><p> Use this function to reference a static dictionary into LZ4_stream_t.
272 The dictionary must remain available during compression.
273 LZ4_loadDict() triggers a reset, so any previous data will be forgotten.
274 The same dictionary will have to be loaded on decompression side for successful decoding.
275 Dictionary are useful for better compression of small data (KB range).
Yann Colletda5e8b72023-12-28 13:47:08 -0800[diff] [blame]276 While LZ4 itself accepts any input as dictionary, dictionary efficiency is also a topic.
277 When in doubt, employ the Zstandard's Dictionary Builder.
Yann Collet3d260f32017-08-30 16:09:10 -0700[diff] [blame]278 Loading a size of 0 is allowed, and is the same as reset.
Yann Colletda5e8b72023-12-28 13:47:08 -0800[diff] [blame]279 @return : loaded dictionary size, in bytes (note: only the last 64 KB are loaded)
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]280
281</p></pre><BR>
282
Yann Collet36df9052024-07-20 14:46:11 -0700[diff] [blame]283<pre><b>int LZ4_loadDictSlow(LZ4_stream_t* streamPtr, const char* dictionary, int dictSize);
284</b><p> Same as LZ4_loadDict(),
285 but uses a bit more cpu to reference the dictionary content more thoroughly.
286 This is expected to slightly improve compression ratio.
287 The extra-cpu cost is likely worth it if the dictionary is re-used across multiple sessions.
288 @return : loaded dictionary size, in bytes (note: only the last 64 KB are loaded)
289
290</p></pre><BR>
291
292<pre><b>void
293LZ4_attach_dictionary(LZ4_stream_t* workingStream,
294 const LZ4_stream_t* dictionaryStream);
295</b><p>
296 This allows efficient re-use of a static dictionary multiple times.
297
298 Rather than re-loading the dictionary buffer into a working context before
299 each compression, or copying a pre-loaded dictionary's LZ4_stream_t into a
300 working LZ4_stream_t, this function introduces a no-copy setup mechanism,
301 in which the working stream references @dictionaryStream in-place.
302
303 Several assumptions are made about the state of @dictionaryStream.
304 Currently, only states which have been prepared by LZ4_loadDict() or
305 LZ4_loadDictSlow() should be expected to work.
306
307 Alternatively, the provided @dictionaryStream may be NULL,
308 in which case any existing dictionary stream is unset.
309
310 If a dictionary is provided, it replaces any pre-existing stream history.
311 The dictionary contents are the only history that can be referenced and
312 logically immediately precede the data compressed in the first subsequent
313 compression call.
314
315 The dictionary will only remain attached to the working stream through the
316 first compression call, at the end of which it is cleared.
317 @dictionaryStream stream (and source buffer) must remain in-place / accessible / unchanged
318 through the completion of the compression session.
319
320 Note: there is no equivalent LZ4_attach_*() method on the decompression side
321 because there is no initialization cost, hence no need to share the cost across multiple sessions.
322 To decompress LZ4 blocks using dictionary, attached or not,
323 just employ the regular LZ4_setStreamDecode() for streaming,
324 or the stateless LZ4_decompress_safe_usingDict() for one-shot decompression.
325
326</p></pre><BR>
327
Yann Colletb8575f22017-05-10 13:26:04 -0700[diff] [blame]328<pre><b>int LZ4_compress_fast_continue (LZ4_stream_t* streamPtr, const char* src, char* dst, int srcSize, int dstCapacity, int acceleration);
Yann Colletba115382018-02-26 13:31:18 -0800[diff] [blame]329</b><p> Compress 'src' content using data from previously compressed blocks, for better compression ratio.
Yann Colleta8032302018-09-13 16:02:11 -0700[diff] [blame]330 'dst' buffer must be already allocated.
Yann Colletb8575f22017-05-10 13:26:04 -0700[diff] [blame]331 If dstCapacity >= LZ4_compressBound(srcSize), compression is guaranteed to succeed, and runs faster.
Yann Collet3d260f32017-08-30 16:09:10 -0700[diff] [blame]332
Yann Collet3d260f32017-08-30 16:09:10 -0700[diff] [blame]333 @return : size of compressed block
Yann Colletba115382018-02-26 13:31:18 -0800[diff] [blame]334 or 0 if there is an error (typically, cannot fit into 'dst').
Yann Colleteaed9ea2018-09-07 16:21:31 -0700[diff] [blame]335
336 Note 1 : Each invocation to LZ4_compress_fast_continue() generates a new block.
337 Each block has precise boundaries.
Yann Colleta8032302018-09-13 16:02:11 -0700[diff] [blame]338 Each block must be decompressed separately, calling LZ4_decompress_*() with relevant metadata.
Yann Colleteaed9ea2018-09-07 16:21:31 -0700[diff] [blame]339 It's not possible to append blocks together and expect a single invocation of LZ4_decompress_*() to decompress them together.
Yann Colleteaed9ea2018-09-07 16:21:31 -0700[diff] [blame]340
Yann Colleta8032302018-09-13 16:02:11 -0700[diff] [blame]341 Note 2 : The previous 64KB of source data is __assumed__ to remain present, unmodified, at same address in memory !
Yann Colleteaed9ea2018-09-07 16:21:31 -0700[diff] [blame]342
343 Note 3 : When input is structured as a double-buffer, each buffer can have any size, including < 64 KB.
344 Make sure that buffers are separated, by at least one byte.
345 This construction ensures that each block only depends on previous block.
346
347 Note 4 : If input buffer is a ring-buffer, it can have any size, including < 64 KB.
348
Yann Colleta8032302018-09-13 16:02:11 -0700[diff] [blame]349 Note 5 : After an error, the stream status is undefined (invalid), it can only be reset or freed.
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]350
351</p></pre><BR>
352
Yann Colletba115382018-02-26 13:31:18 -0800[diff] [blame]353<pre><b>int LZ4_saveDict (LZ4_stream_t* streamPtr, char* safeBuffer, int maxDictSize);
354</b><p> If last 64KB data cannot be guaranteed to remain available at its current memory location,
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]355 save it into a safer place (char* safeBuffer).
Yann Colletba115382018-02-26 13:31:18 -0800[diff] [blame]356 This is schematically equivalent to a memcpy() followed by LZ4_loadDict(),
357 but is much faster, because LZ4_saveDict() doesn't need to rebuild tables.
358 @return : saved dictionary size in bytes (necessarily <= maxDictSize), or 0 if error.
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]359
360</p></pre><BR>
361
Przemyslaw Skibinski6a5633e2017-01-23 16:03:40 +0100[diff] [blame]362<a name="Chapter7"></a><h2>Streaming Decompression Functions</h2><pre> Bufferless synchronous API
363<BR></pre>
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]364
Yann Colleta2e4da32023-12-07 16:14:37 -0800[diff] [blame]365<pre><b>#if !defined(RC_INVOKED) </b>/* https://docs.microsoft.com/en-us/windows/win32/menurc/predefined-macros */<b>
366#if !defined(LZ4_STATIC_LINKING_ONLY_DISABLE_MEMORY_ALLOCATION)
Yann Collet18b293d2022-08-11 14:06:17 -0700[diff] [blame]367LZ4_streamDecode_t* LZ4_createStreamDecode(void);
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]368int LZ4_freeStreamDecode (LZ4_streamDecode_t* LZ4_stream);
Yann Collet18b293d2022-08-11 14:06:17 -0700[diff] [blame]369#endif </b>/* !defined(LZ4_STATIC_LINKING_ONLY_DISABLE_MEMORY_ALLOCATION) */<b>
Yann Colleta2e4da32023-12-07 16:14:37 -0800[diff] [blame]370#endif
Yann Colletc25eb162018-05-02 16:05:42 -0700[diff] [blame]371</b><p> creation / destruction of streaming decompression tracking context.
372 A tracking context can be re-used multiple times.
373
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]374</p></pre><BR>
375
376<pre><b>int LZ4_setStreamDecode (LZ4_streamDecode_t* LZ4_streamDecode, const char* dictionary, int dictSize);
Yann Colletc25eb162018-05-02 16:05:42 -0700[diff] [blame]377</b><p> An LZ4_streamDecode_t context can be allocated once and re-used multiple times.
Yann Collet3d260f32017-08-30 16:09:10 -0700[diff] [blame]378 Use this function to start decompression of a new stream of blocks.
Jack Luo3358e162018-07-28 22:12:55 -0400[diff] [blame]379 A dictionary can optionally be set. Use NULL or size 0 for a reset order.
Yann Colletc25eb162018-05-02 16:05:42 -0700[diff] [blame]380 Dictionary is presumed stable : it must remain accessible and unmodified during next decompression.
Yann Collete3c71582017-08-30 15:42:04 -0700[diff] [blame]381 @return : 1 if OK, 0 if error
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]382
383</p></pre><BR>
384
Yann Colletc25eb162018-05-02 16:05:42 -0700[diff] [blame]385<pre><b>int LZ4_decoderRingBufferSize(int maxBlockSize);
Yann Colleta8032302018-09-13 16:02:11 -0700[diff] [blame]386#define LZ4_DECODER_RING_BUFFER_SIZE(maxBlockSize) (65536 + 14 + (maxBlockSize)) </b>/* for static allocation; maxBlockSize presumed valid */<b>
Yann Colletc25eb162018-05-02 16:05:42 -0700[diff] [blame]387</b><p> Note : in a ring buffer scenario (optional),
388 blocks are presumed decompressed next to each other
389 up to the moment there is not enough remaining space for next block (remainingSize < maxBlockSize),
390 at which stage it resumes from beginning of ring buffer.
391 When setting such a ring buffer for streaming decompression,
392 provides the minimum size of this ring buffer
393 to be compatible with any source respecting maxBlockSize condition.
394 @return : minimum ring buffer size,
395 or 0 if there is an error (invalid maxBlockSize).
396
397</p></pre><BR>
398
Yann Collet18b293d2022-08-11 14:06:17 -0700[diff] [blame]399<pre><b>int
400LZ4_decompress_safe_continue (LZ4_streamDecode_t* LZ4_streamDecode,
401 const char* src, char* dst,
402 int srcSize, int dstCapacity);
Yann Colleta2e4da32023-12-07 16:14:37 -0800[diff] [blame]403</b><p> This decoding function allows decompression of consecutive blocks in "streaming" mode.
404 The difference with the usual independent blocks is that
405 new blocks are allowed to find references into former blocks.
406 A block is an unsplittable entity, and must be presented entirely to the decompression function.
407 LZ4_decompress_safe_continue() only accepts one block at a time.
408 It's modeled after `LZ4_decompress_safe()` and behaves similarly.
409
410 @LZ4_streamDecode : decompression state, tracking the position in memory of past data
411 @compressedSize : exact complete size of one compressed block.
412 @dstCapacity : size of destination buffer (which must be already allocated),
413 must be an upper bound of decompressed size.
414 @return : number of bytes decompressed into destination buffer (necessarily <= dstCapacity)
415 If destination buffer is not large enough, decoding will stop and output an error code (negative value).
416 If the source stream is detected malformed, the function will stop decoding and return a negative result.
417
418 The last 64KB of previously decoded data *must* remain available and unmodified
419 at the memory position where they were previously decoded.
Yann Colletc25eb162018-05-02 16:05:42 -0700[diff] [blame]420 If less than 64KB of data has been decoded, all the data must be present.
Yann Collete3c71582017-08-30 15:42:04 -0700[diff] [blame]421
Yann Colletc25eb162018-05-02 16:05:42 -0700[diff] [blame]422 Special : if decompression side sets a ring buffer, it must respect one of the following conditions :
423 - Decompression buffer size is _at least_ LZ4_decoderRingBufferSize(maxBlockSize).
424 maxBlockSize is the maximum size of any single block. It can have any value > 16 bytes.
425 In which case, encoding and decoding buffers do not need to be synchronized.
426 Actually, data can be produced by any source compliant with LZ4 format specification, and respecting maxBlockSize.
427 - Synchronized mode :
428 Decompression buffer size is _exactly_ the same as compression buffer size,
429 and follows exactly same update rule (block boundaries at same positions),
430 and decoding function is provided with exact decompressed size of each block (exception for last block of the stream),
431 _then_ decoding & encoding ring buffer can have any size, including small ones ( < 64 KB).
432 - Decompression buffer is larger than encoding buffer, by a minimum of maxBlockSize more bytes.
Yann Colletd8aafe22017-08-10 00:48:19 -0700[diff] [blame]433 In which case, encoding and decoding buffers do not need to be synchronized,
434 and encoding ring buffer can have any size, including small ones ( < 64 KB).
Yann Colletc25eb162018-05-02 16:05:42 -0700[diff] [blame]435
436 Whenever these conditions are not possible,
437 save the last 64KB of decoded data into a safe buffer where it can't be modified during decompression,
438 then indicate where this data is saved using LZ4_setStreamDecode(), before decompressing next block.
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]439</p></pre><BR>
440
Yann Collet18b293d2022-08-11 14:06:17 -0700[diff] [blame]441<pre><b>int
442LZ4_decompress_safe_usingDict(const char* src, char* dst,
443 int srcSize, int dstCapacity,
444 const char* dictStart, int dictSize);
Yann Colleta2e4da32023-12-07 16:14:37 -0800[diff] [blame]445</b><p> Works the same as
446 a combination of LZ4_setStreamDecode() followed by LZ4_decompress_safe_continue()
447 However, it's stateless: it doesn't need any LZ4_streamDecode_t state.
Yann Colleta8032302018-09-13 16:02:11 -0700[diff] [blame]448 Dictionary is presumed stable : it must remain accessible and unmodified during decompression.
449 Performance tip : Decompression speed can be substantially increased
450 when dst == dictStart + dictSize.
Przemyslaw Skibinski6a5633e2017-01-23 16:03:40 +0100[diff] [blame]451
452</p></pre><BR>
453
Yann Colleta2e4da32023-12-07 16:14:37 -0800[diff] [blame]454<pre><b>int
455LZ4_decompress_safe_partial_usingDict(const char* src, char* dst,
456 int compressedSize,
457 int targetOutputSize, int maxOutputSize,
458 const char* dictStart, int dictSize);
459</b><p> Behaves the same as LZ4_decompress_safe_partial()
460 with the added ability to specify a memory segment for past data.
461 Performance tip : Decompression speed can be substantially increased
462 when dst == dictStart + dictSize.
463
464</p></pre><BR>
465
Yann Collet50f01d82019-04-03 14:27:21 -0700[diff] [blame]466<a name="Chapter8"></a><h2>Experimental section</h2><pre>
467 Symbols declared in this section must be considered unstable. Their
468 signatures or semantics may change, or they may be removed altogether in the
Yann Collet25da6cc2019-04-03 14:18:00 -0700[diff] [blame]469 future. They are therefore only safe to depend on when the caller is
470 statically linked against the library.
471
Yann Collet50f01d82019-04-03 14:27:21 -0700[diff] [blame]472 To protect against unsafe usage, not only are the declarations guarded,
473 the definitions are hidden by default
474 when building LZ4 as a shared/dynamic library.
Yann Collet25da6cc2019-04-03 14:18:00 -0700[diff] [blame]475
Yann Collet50f01d82019-04-03 14:27:21 -0700[diff] [blame]476 In order to access these declarations,
477 define LZ4_STATIC_LINKING_ONLY in your application
478 before including LZ4's headers.
Yann Collet25da6cc2019-04-03 14:18:00 -0700[diff] [blame]479
480 In order to make their implementations accessible dynamically, you must
481 define LZ4_PUBLISH_STATIC_FUNCTIONS when building the LZ4 library.
Cyan497357afa362018-04-13 01:01:54 -0700[diff] [blame]482<BR></pre>
483
Yann Colleta8032302018-09-13 16:02:11 -0700[diff] [blame]484<pre><b>LZ4LIB_STATIC_API int LZ4_compress_fast_extState_fastReset (void* state, const char* src, char* dst, int srcSize, int dstCapacity, int acceleration);
Cyan497357afa362018-04-13 01:01:54 -0700[diff] [blame]485</b><p> A variant of LZ4_compress_fast_extState().
486
Yann Colleta8032302018-09-13 16:02:11 -0700[diff] [blame]487 Using this variant avoids an expensive initialization step.
488 It is only safe to call if the state buffer is known to be correctly initialized already
489 (see above comment on LZ4_resetStream_fast() for a definition of "correctly initialized").
490 From a high level, the difference is that
491 this function initializes the provided state with a call to something like LZ4_resetStream_fast()
492 while LZ4_compress_fast_extState() starts with a call to LZ4_resetStream().
Cyan497357afa362018-04-13 01:01:54 -0700[diff] [blame]493
494</p></pre><BR>
495
Yann Colletda5e8b72023-12-28 13:47:08 -0800[diff] [blame]496<pre><b>int LZ4_compress_destSize_extState(void* state, const char* src, char* dst, int* srcSizePtr, int targetDstSize, int acceleration);
497</b><p> Same as LZ4_compress_destSize(), but using an externally allocated state.
498 Also: exposes @acceleration
499
500</p></pre><BR>
501
Yann Colletb17f5782019-05-29 12:06:13 -0700[diff] [blame]502<pre><b></b><p>
503 It's possible to have input and output sharing the same buffer,
Yann Collet596c7472021-08-16 16:43:17 -0700[diff] [blame]504 for highly constrained memory environments.
Yann Colletb17f5782019-05-29 12:06:13 -0700[diff] [blame]505 In both cases, it requires input to lay at the end of the buffer,
Yann Collet22adbb12019-05-30 09:45:21 -0700[diff] [blame]506 and decompression to start at beginning of the buffer.
507 Buffer size must feature some margin, hence be larger than final size.
508
Yann Collet5997e132019-05-31 11:56:59 -0700[diff] [blame]509 |<------------------------buffer--------------------------------->|
510 |<-----------compressed data--------->|
Yann Collet22adbb12019-05-30 09:45:21 -0700[diff] [blame]511 |<-----------decompressed size------------------>|
Yann Collet5997e132019-05-31 11:56:59 -0700[diff] [blame]512 |<----margin---->|
Yann Colletb17f5782019-05-29 12:06:13 -0700[diff] [blame]513
514 This technique is more useful for decompression,
515 since decompressed size is typically larger,
Yann Collet5997e132019-05-31 11:56:59 -0700[diff] [blame]516 and margin is short.
Yann Colletb17f5782019-05-29 12:06:13 -0700[diff] [blame]517
Yann Collet22adbb12019-05-30 09:45:21 -0700[diff] [blame]518 In-place decompression will work inside any buffer
519 which size is >= LZ4_DECOMPRESS_INPLACE_BUFFER_SIZE(decompressedSize).
520 This presumes that decompressedSize > compressedSize.
521 Otherwise, it means compression actually expanded data,
Yann Collet22adbb12019-05-30 09:45:21 -0700[diff] [blame]522 and it would be more efficient to store such data with a flag indicating it's not compressed.
Yann Collet5997e132019-05-31 11:56:59 -0700[diff] [blame]523 This can happen when data is not compressible (already compressed, or encrypted).
Yann Collet22adbb12019-05-30 09:45:21 -0700[diff] [blame]524
Yann Collet5997e132019-05-31 11:56:59 -0700[diff] [blame]525 For in-place compression, margin is larger, as it must be able to cope with both
Yann Colletb17f5782019-05-29 12:06:13 -0700[diff] [blame]526 history preservation, requiring input data to remain unmodified up to LZ4_DISTANCE_MAX,
527 and data expansion, which can happen when input is not compressible.
Yann Collet22adbb12019-05-30 09:45:21 -0700[diff] [blame]528 As a consequence, buffer size requirements are much higher,
529 and memory savings offered by in-place compression are more limited.
Yann Colletb17f5782019-05-29 12:06:13 -0700[diff] [blame]530
531 There are ways to limit this cost for compression :
532 - Reduce history size, by modifying LZ4_DISTANCE_MAX.
Yann Collet5997e132019-05-31 11:56:59 -0700[diff] [blame]533 Note that it is a compile-time constant, so all compressions will apply this limit.
Yann Collet22adbb12019-05-30 09:45:21 -0700[diff] [blame]534 Lower values will reduce compression ratio, except when input_size < LZ4_DISTANCE_MAX,
Yann Colletb17f5782019-05-29 12:06:13 -0700[diff] [blame]535 so it's a reasonable trick when inputs are known to be small.
536 - Require the compressor to deliver a "maximum compressed size".
Yann Collet5997e132019-05-31 11:56:59 -0700[diff] [blame]537 This is the `dstCapacity` parameter in `LZ4_compress*()`.
Yann Colletb17f5782019-05-29 12:06:13 -0700[diff] [blame]538 When this size is < LZ4_COMPRESSBOUND(inputSize), then compression can fail,
539 in which case, the return code will be 0 (zero).
540 The caller must be ready for these cases to happen,
541 and typically design a backup scheme to send data uncompressed.
542 The combination of both techniques can significantly reduce
543 the amount of margin required for in-place compression.
Yann Collet22adbb12019-05-30 09:45:21 -0700[diff] [blame]544
545 In-place compression can work in any buffer
Yann Collet5997e132019-05-31 11:56:59 -0700[diff] [blame]546 which size is >= (maxCompressedSize)
Yann Collet22adbb12019-05-30 09:45:21 -0700[diff] [blame]547 with maxCompressedSize == LZ4_COMPRESSBOUND(srcSize) for guaranteed compression success.
Yann Collet5997e132019-05-31 11:56:59 -0700[diff] [blame]548 LZ4_COMPRESS_INPLACE_BUFFER_SIZE() depends on both maxCompressedSize and LZ4_DISTANCE_MAX,
549 so it's possible to reduce memory requirements by playing with them.
Yann Colletb17f5782019-05-29 12:06:13 -0700[diff] [blame]550
551</p></pre><BR>
552
Yann Collet5997e132019-05-31 11:56:59 -0700[diff] [blame]553<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>
Yann Colletb17f5782019-05-29 12:06:13 -0700[diff] [blame]554</b></pre><BR>
Yann Collet5997e132019-05-31 11:56:59 -0700[diff] [blame]555<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>
Yann Colletb17f5782019-05-29 12:06:13 -0700[diff] [blame]556</b></pre><BR>
Yann Colletbe634552020-11-08 12:54:59 -0800[diff] [blame]557<a name="Chapter9"></a><h2>Private Definitions</h2><pre>
Yann Colleta8032302018-09-13 16:02:11 -0700[diff] [blame]558 Do not use these definitions directly.
559 They are only exposed to allow static allocation of `LZ4_stream_t` and `LZ4_streamDecode_t`.
Yann Colletbe634552020-11-08 12:54:59 -0800[diff] [blame]560 Accessing members will expose user code to API and/or ABI break in future versions of the library.
Przemyslaw Skibinski6a5633e2017-01-23 16:03:40 +0100[diff] [blame]561<BR></pre>
562
Yann Collet7deae4b2022-07-13 15:55:56 +0200[diff] [blame]563<pre><b></b><p> Never ever use below internal definitions directly !
564 These definitions are not API/ABI safe, and may change in future versions.
565 If you need static allocation, declare or allocate an LZ4_stream_t object.
Yann Collet2ece0d82019-04-05 12:54:13 -0700[diff] [blame]566</p></pre><BR>
567
Yann Colletda5e8b72023-12-28 13:47:08 -0800[diff] [blame]568<pre><b>LZ4_stream_t* LZ4_initStream (void* stateBuffer, size_t size);
Yann Collet2ece0d82019-04-05 12:54:13 -0700[diff] [blame]569</b><p> An LZ4_stream_t structure must be initialized at least once.
Yann Collet14c71df2019-04-09 13:55:42 -0700[diff] [blame]570 This is automatically done when invoking LZ4_createStream(),
571 but it's not when the structure is simply declared on stack (for example).
572
573 Use LZ4_initStream() to properly initialize a newly declared LZ4_stream_t.
574 It can also initialize any arbitrary buffer of sufficient size,
575 and will @return a pointer of proper type upon initialization.
576
577 Note : initialization fails if size and alignment conditions are not respected.
578 In which case, the function will @return NULL.
579 Note2: An LZ4_stream_t structure guarantees correct alignment and size.
Yann Collet8d76c8a2019-04-11 14:15:33 -0700[diff] [blame]580 Note3: Before v1.9.0, use LZ4_resetStream() instead
Przemyslaw Skibinski6a5633e2017-01-23 16:03:40 +0100[diff] [blame]581</p></pre><BR>
582
Yann Collet7deae4b2022-07-13 15:55:56 +0200[diff] [blame]583<pre><b>typedef struct {
584 const LZ4_byte* externalDict;
585 const LZ4_byte* prefixEnd;
586 size_t extDictSize;
587 size_t prefixSize;
588} LZ4_streamDecode_t_internal;
589</b><p> Never ever use below internal definitions directly !
590 These definitions are not API/ABI safe, and may change in future versions.
591 If you need static allocation, declare or allocate an LZ4_streamDecode_t object.
Przemyslaw Skibinski6a5633e2017-01-23 16:03:40 +0100[diff] [blame]592</p></pre><BR>
593
Cyan497357afa362018-04-13 01:01:54 -0700[diff] [blame]594<a name="Chapter10"></a><h2>Obsolete Functions</h2><pre></pre>
Przemyslaw Skibinski6a5633e2017-01-23 16:03:40 +0100[diff] [blame]595
596<pre><b>#ifdef LZ4_DISABLE_DEPRECATE_WARNINGS
597# define LZ4_DEPRECATED(message) </b>/* disable deprecation warnings */<b>
598#else
Yann Colletea252502018-02-07 02:21:25 -0800[diff] [blame]599# if defined (__cplusplus) && (__cplusplus >= 201402) </b>/* C++14 or greater */<b>
Przemyslaw Skibinski6a5633e2017-01-23 16:03:40 +0100[diff] [blame]600# define LZ4_DEPRECATED(message) [[deprecated(message)]]
Przemyslaw Skibinski6a5633e2017-01-23 16:03:40 +0100[diff] [blame]601# elif defined(_MSC_VER)
602# define LZ4_DEPRECATED(message) __declspec(deprecated(message))
Yann Collet293713a2020-09-29 14:27:39 -0700[diff] [blame]603# elif defined(__clang__) || (defined(__GNUC__) && (__GNUC__ * 10 + __GNUC_MINOR__ >= 45))
604# define LZ4_DEPRECATED(message) __attribute__((deprecated(message)))
605# elif defined(__GNUC__) && (__GNUC__ * 10 + __GNUC_MINOR__ >= 31)
606# define LZ4_DEPRECATED(message) __attribute__((deprecated))
Przemyslaw Skibinski6a5633e2017-01-23 16:03:40 +0100[diff] [blame]607# else
Yann Collet293713a2020-09-29 14:27:39 -0700[diff] [blame]608# pragma message("WARNING: LZ4_DEPRECATED needs custom implementation for this compiler")
609# define LZ4_DEPRECATED(message) </b>/* disabled */<b>
Przemyslaw Skibinski6a5633e2017-01-23 16:03:40 +0100[diff] [blame]610# endif
611#endif </b>/* LZ4_DISABLE_DEPRECATE_WARNINGS */<b>
Yann Collet7a39fb82019-04-04 12:47:36 -0700[diff] [blame]612</b><p>
613 Deprecated functions make the compiler generate a warning when invoked.
614 This is meant to invite users to update their source code.
615 Should deprecation warnings be a problem, it is generally possible to disable them,
Yann Colletc4c19c72018-09-25 14:43:19 -0700[diff] [blame]616 typically with -Wno-deprecated-declarations for gcc
617 or _CRT_SECURE_NO_WARNINGS in Visual.
Yann Collet7a39fb82019-04-04 12:47:36 -0700[diff] [blame]618
619 Another method is to define LZ4_DISABLE_DEPRECATE_WARNINGS
620 before including the header file.
621
622</p></pre><BR>
623
Yann Colletbe634552020-11-08 12:54:59 -0800[diff] [blame]624<pre><b>LZ4_DEPRECATED("use LZ4_compress_default() instead") LZ4LIB_API int LZ4_compress (const char* src, char* dest, int srcSize);
625LZ4_DEPRECATED("use LZ4_compress_default() instead") LZ4LIB_API int LZ4_compress_limitedOutput (const char* src, char* dest, int srcSize, int maxOutputSize);
626LZ4_DEPRECATED("use LZ4_compress_fast_extState() instead") LZ4LIB_API int LZ4_compress_withState (void* state, const char* source, char* dest, int inputSize);
627LZ4_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);
628LZ4_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);
629LZ4_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);
630</b><p></p></pre><BR>
631
632<pre><b>LZ4_DEPRECATED("use LZ4_decompress_fast() instead") LZ4LIB_API int LZ4_uncompress (const char* source, char* dest, int outputSize);
633LZ4_DEPRECATED("use LZ4_decompress_safe() instead") LZ4LIB_API int LZ4_uncompress_unknownOutputSize (const char* source, char* dest, int isize, int maxOutputSize);
634</b><p></p></pre><BR>
635
636<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);
637LZ4_DEPRECATED("use LZ4_decompress_fast_usingDict() instead") LZ4LIB_API int LZ4_decompress_fast_withPrefix64k (const char* src, char* dst, int originalSize);
638</b><p></p></pre><BR>
639
Yann Colleta2e4da32023-12-07 16:14:37 -0800[diff] [blame]640<pre><b>LZ4_DEPRECATED("This function is deprecated and unsafe. Consider using LZ4_decompress_safe_partial() instead")
Yann Colletbe634552020-11-08 12:54:59 -0800[diff] [blame]641int LZ4_decompress_fast (const char* src, char* dst, int originalSize);
Yann Colleta2e4da32023-12-07 16:14:37 -0800[diff] [blame]642LZ4_DEPRECATED("This function is deprecated and unsafe. Consider migrating towards LZ4_decompress_safe_continue() instead. "
643 "Note that the contract will change (requires block's compressed size, instead of decompressed size)")
Yann Colletbe634552020-11-08 12:54:59 -0800[diff] [blame]644int LZ4_decompress_fast_continue (LZ4_streamDecode_t* LZ4_streamDecode, const char* src, char* dst, int originalSize);
Yann Colleta2e4da32023-12-07 16:14:37 -0800[diff] [blame]645LZ4_DEPRECATED("This function is deprecated and unsafe. Consider using LZ4_decompress_safe_partial_usingDict() instead")
Yann Colletbe634552020-11-08 12:54:59 -0800[diff] [blame]646int LZ4_decompress_fast_usingDict (const char* src, char* dst, int originalSize, const char* dictStart, int dictSize);
647</b><p> These functions used to be faster than LZ4_decompress_safe(),
648 but this is no longer the case. They are now slower.
Yann Collet0b876db2019-04-18 16:06:02 -0700[diff] [blame]649 This is because LZ4_decompress_fast() doesn't know the input size,
Yann Colletbe634552020-11-08 12:54:59 -0800[diff] [blame]650 and therefore must progress more cautiously into the input buffer to not read beyond the end of block.
Yann Collet0b876db2019-04-18 16:06:02 -0700[diff] [blame]651 On top of that `LZ4_decompress_fast()` is not protected vs malformed or malicious inputs, making it a security liability.
Yann Collet7a39fb82019-04-04 12:47:36 -0700[diff] [blame]652 As a consequence, LZ4_decompress_fast() is strongly discouraged, and deprecated.
653
Yann Collet0b876db2019-04-18 16:06:02 -0700[diff] [blame]654 The last remaining LZ4_decompress_fast() specificity is that
655 it can decompress a block without knowing its compressed size.
Yann Colletbe634552020-11-08 12:54:59 -0800[diff] [blame]656 Such functionality can be achieved in a more secure manner
657 by employing LZ4_decompress_safe_partial().
Yann Collet7a39fb82019-04-04 12:47:36 -0700[diff] [blame]658
659 Parameters:
660 originalSize : is the uncompressed size to regenerate.
661 `dst` must be already allocated, its size must be >= 'originalSize' bytes.
662 @return : number of bytes read from source buffer (== compressed size).
663 The function expects to finish at block's end exactly.
664 If the source stream is detected malformed, the function stops decoding and returns a negative result.
665 note : LZ4_decompress_fast*() requires originalSize. Thanks to this information, it never writes past the output buffer.
Yann Collet0b876db2019-04-18 16:06:02 -0700[diff] [blame]666 However, since it doesn't know its 'src' size, it may read an unknown amount of input, past input buffer bounds.
667 Also, since match offsets are not validated, match reads from 'src' may underflow too.
668 These issues never happen if input (compressed) data is correct.
Yann Collet7a39fb82019-04-04 12:47:36 -0700[diff] [blame]669 But they may happen if input data is invalid (error or intentional tampering).
670 As a consequence, use these functions in trusted environments with trusted data **only**.
671
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]672</p></pre><BR>
673
Yann Collet14c71df2019-04-09 13:55:42 -0700[diff] [blame]674<pre><b>void LZ4_resetStream (LZ4_stream_t* streamPtr);
Yann Collet2ece0d82019-04-05 12:54:13 -0700[diff] [blame]675</b><p> An LZ4_stream_t structure must be initialized at least once.
676 This is done with LZ4_initStream(), or LZ4_resetStream().
677 Consider switching to LZ4_initStream(),
678 invoking LZ4_resetStream() will trigger deprecation warnings in the future.
679
680</p></pre><BR>
681
Przemyslaw Skibinski93e24772016-11-10 17:22:26 +0100[diff] [blame]682</html>
683</body>