2016-11-10 16:22:26 +00:00
|
|
|
<html>
|
|
|
|
|
<head>
|
|
|
|
|
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
|
2018-02-26 21:50:04 +00:00
|
|
|
<title>1.8.2 Manual</title>
|
2016-11-10 16:22:26 +00:00
|
|
|
</head>
|
|
|
|
|
<body>
|
2018-02-26 21:50:04 +00:00
|
|
|
<h1>1.8.2 Manual</h1>
|
2016-11-10 16:22:26 +00:00
|
|
|
<hr>
|
|
|
|
|
<a name="Contents"></a><h2>Contents</h2>
|
|
|
|
|
<ol>
|
|
|
|
|
<li><a href="#Chapter1">Introduction</a></li>
|
2017-01-23 15:03:40 +00:00
|
|
|
<li><a href="#Chapter2">Version</a></li>
|
|
|
|
|
<li><a href="#Chapter3">Tuning parameter</a></li>
|
2016-11-11 21:00:02 +00:00
|
|
|
<li><a href="#Chapter4">Simple Functions</a></li>
|
|
|
|
|
<li><a href="#Chapter5">Advanced Functions</a></li>
|
|
|
|
|
<li><a href="#Chapter6">Streaming Compression Functions</a></li>
|
|
|
|
|
<li><a href="#Chapter7">Streaming Decompression Functions</a></li>
|
2018-04-13 08:01:54 +00:00
|
|
|
<li><a href="#Chapter8">Unstable declarations</a></li>
|
|
|
|
|
<li><a href="#Chapter9">Private definitions</a></li>
|
|
|
|
|
<li><a href="#Chapter10">Obsolete Functions</a></li>
|
2016-11-10 16:22:26 +00:00
|
|
|
</ol>
|
|
|
|
|
<hr>
|
|
|
|
|
<a name="Chapter1"></a><h2>Introduction</h2><pre>
|
|
|
|
|
LZ4 is lossless compression algorithm, providing compression speed at 400 MB/s per core,
|
|
|
|
|
scalable with multi-cores CPU. It features an extremely fast decoder, with speed in
|
|
|
|
|
multiple GB/s per core, typically reaching RAM speed limits on multi-core systems.
|
|
|
|
|
|
|
|
|
|
The LZ4 compression library provides in-memory compression and decompression functions.
|
|
|
|
|
Compression can be done in:
|
|
|
|
|
- a single step (described as Simple Functions)
|
|
|
|
|
- a single step, reusing a context (described in Advanced Functions)
|
|
|
|
|
- unbounded multiple steps (described as Streaming compression)
|
|
|
|
|
|
|
|
|
|
lz4.h provides block compression functions. It gives full buffer control to user.
|
2017-01-23 15:03:40 +00:00
|
|
|
Decompressing an lz4-compressed block also requires metadata (such as compressed size).
|
|
|
|
|
Each application is free to encode such metadata in whichever way it wants.
|
|
|
|
|
|
|
|
|
|
An additional format, called LZ4 frame specification (doc/lz4_Frame_format.md),
|
|
|
|
|
take care of encoding standard metadata alongside LZ4-compressed blocks.
|
|
|
|
|
If your application requires interoperability, it's recommended to use it.
|
2016-11-10 16:22:26 +00:00
|
|
|
A library is provided to take care of it, see lz4frame.h.
|
|
|
|
|
<BR></pre>
|
|
|
|
|
|
2017-01-23 15:03:40 +00:00
|
|
|
<a name="Chapter2"></a><h2>Version</h2><pre></pre>
|
|
|
|
|
|
2018-02-07 10:21:25 +00:00
|
|
|
<pre><b>int LZ4_versionNumber (void); </b>/**< library version number; useful to check dll version */<b>
|
2016-11-10 16:22:26 +00:00
|
|
|
</b></pre><BR>
|
2018-02-07 10:21:25 +00:00
|
|
|
<pre><b>const char* LZ4_versionString (void); </b>/**< library version string; unseful to check dll version */<b>
|
2017-01-23 15:03:40 +00:00
|
|
|
</b></pre><BR>
|
|
|
|
|
<a name="Chapter3"></a><h2>Tuning parameter</h2><pre></pre>
|
2016-11-10 16:22:26 +00:00
|
|
|
|
2017-01-23 15:03:40 +00:00
|
|
|
<pre><b>#ifndef LZ4_MEMORY_USAGE
|
|
|
|
|
# define LZ4_MEMORY_USAGE 14
|
|
|
|
|
#endif
|
2016-11-10 16:22:26 +00:00
|
|
|
</b><p> Memory usage formula : N->2^N Bytes (examples : 10 -> 1KB; 12 -> 4KB ; 16 -> 64KB; 20 -> 1MB; etc.)
|
|
|
|
|
Increasing memory usage improves compression ratio
|
2018-02-07 10:21:25 +00:00
|
|
|
Reduced memory usage may improve speed, thanks to cache effect
|
2016-11-10 16:22:26 +00:00
|
|
|
Default value is 14, for 16KB, which nicely fits into Intel x86 L1 cache
|
|
|
|
|
|
|
|
|
|
</p></pre><BR>
|
|
|
|
|
|
2016-11-11 21:00:02 +00:00
|
|
|
<a name="Chapter4"></a><h2>Simple Functions</h2><pre></pre>
|
2016-11-10 16:22:26 +00:00
|
|
|
|
2017-11-20 18:27:05 +00:00
|
|
|
<pre><b>int LZ4_compress_default(const char* src, char* dst, int srcSize, int dstCapacity);
|
|
|
|
|
</b><p> Compresses 'srcSize' bytes from buffer 'src'
|
|
|
|
|
into already allocated 'dst' buffer of size 'dstCapacity'.
|
|
|
|
|
Compression is guaranteed to succeed if 'dstCapacity' >= LZ4_compressBound(srcSize).
|
2016-11-10 16:22:26 +00:00
|
|
|
It also runs faster, so it's a recommended setting.
|
2018-02-07 10:21:25 +00:00
|
|
|
If the function cannot compress 'src' into a more limited 'dst' budget,
|
2016-11-10 16:22:26 +00:00
|
|
|
compression stops *immediately*, and the function result is zero.
|
2018-02-07 10:21:25 +00:00
|
|
|
Note : as a consequence, 'dst' content is not valid.
|
|
|
|
|
Note 2 : This function is protected against buffer overflow scenarios (never writes outside 'dst' buffer, nor read outside 'source' buffer).
|
|
|
|
|
srcSize : max supported value is LZ4_MAX_INPUT_SIZE.
|
|
|
|
|
dstCapacity : size of buffer 'dst' (which must be already allocated)
|
2017-11-20 18:27:05 +00:00
|
|
|
return : the number of bytes written into buffer 'dst' (necessarily <= dstCapacity)
|
|
|
|
|
or 0 if compression fails
|
|
|
|
|
</p></pre><BR>
|
|
|
|
|
|
|
|
|
|
<pre><b>int LZ4_decompress_safe (const char* src, char* dst, int compressedSize, int dstCapacity);
|
|
|
|
|
</b><p> compressedSize : is the exact complete size of the compressed block.
|
|
|
|
|
dstCapacity : is the size of destination buffer, which must be already allocated.
|
|
|
|
|
return : the number of bytes decompressed into destination buffer (necessarily <= dstCapacity)
|
|
|
|
|
If destination buffer is not large enough, decoding will stop and output an error code (negative value).
|
2016-11-10 16:22:26 +00:00
|
|
|
If the source stream is detected malformed, the function will stop decoding and return a negative result.
|
2018-02-07 10:21:25 +00:00
|
|
|
This function is protected against malicious data packets.
|
2016-11-10 16:22:26 +00:00
|
|
|
</p></pre><BR>
|
|
|
|
|
|
2016-11-11 21:00:02 +00:00
|
|
|
<a name="Chapter5"></a><h2>Advanced Functions</h2><pre></pre>
|
2016-11-10 16:22:26 +00:00
|
|
|
|
|
|
|
|
<pre><b>int LZ4_compressBound(int inputSize);
|
|
|
|
|
</b><p> Provides the maximum size that LZ4 compression may output in a "worst case" scenario (input data not compressible)
|
|
|
|
|
This function is primarily useful for memory allocation purposes (destination buffer size).
|
|
|
|
|
Macro LZ4_COMPRESSBOUND() is also provided for compilation-time evaluation (stack memory allocation for example).
|
2018-02-07 10:21:25 +00:00
|
|
|
Note that LZ4_compress_default() compresses faster when dstCapacity is >= LZ4_compressBound(srcSize)
|
2016-11-10 16:22:26 +00:00
|
|
|
inputSize : max supported value is LZ4_MAX_INPUT_SIZE
|
|
|
|
|
return : maximum output size in a "worst case" scenario
|
2018-02-07 10:21:25 +00:00
|
|
|
or 0, if input size is incorrect (too large or negative)
|
2016-11-10 16:22:26 +00:00
|
|
|
</p></pre><BR>
|
|
|
|
|
|
2017-11-20 18:27:05 +00:00
|
|
|
<pre><b>int LZ4_compress_fast (const char* src, char* dst, int srcSize, int dstCapacity, int acceleration);
|
2018-02-07 10:21:25 +00:00
|
|
|
</b><p> Same as LZ4_compress_default(), but allows selection of "acceleration" factor.
|
2016-11-10 16:22:26 +00:00
|
|
|
The larger the acceleration value, the faster the algorithm, but also the lesser the compression.
|
|
|
|
|
It's a trade-off. It can be fine tuned, with each successive value providing roughly +~3% to speed.
|
|
|
|
|
An acceleration value of "1" is the same as regular LZ4_compress_default()
|
2018-02-07 10:21:25 +00:00
|
|
|
Values <= 0 will be replaced by ACCELERATION_DEFAULT (currently == 1, see lz4.c).
|
2016-11-10 16:22:26 +00:00
|
|
|
</p></pre><BR>
|
|
|
|
|
|
|
|
|
|
<pre><b>int LZ4_sizeofState(void);
|
2017-11-20 18:27:05 +00:00
|
|
|
int LZ4_compress_fast_extState (void* state, const char* src, char* dst, int srcSize, int dstCapacity, int acceleration);
|
2016-11-10 16:22:26 +00:00
|
|
|
</b><p> Same compression function, just using an externally allocated memory space to store compression state.
|
|
|
|
|
Use LZ4_sizeofState() to know how much memory must be allocated,
|
|
|
|
|
and allocate it on 8-bytes boundaries (using malloc() typically).
|
|
|
|
|
Then, provide it as 'void* state' to compression function.
|
|
|
|
|
</p></pre><BR>
|
|
|
|
|
|
2017-11-20 18:27:05 +00:00
|
|
|
<pre><b>int LZ4_compress_destSize (const char* src, char* dst, int* srcSizePtr, int targetDstSize);
|
|
|
|
|
</b><p> Reverse the logic : compresses as much data as possible from 'src' buffer
|
|
|
|
|
into already allocated buffer 'dst' of size 'targetDestSize'.
|
|
|
|
|
This function either compresses the entire 'src' content into 'dst' if it's large enough,
|
|
|
|
|
or fill 'dst' buffer completely with as much data as possible from 'src'.
|
|
|
|
|
*srcSizePtr : will be modified to indicate how many bytes where read from 'src' to fill 'dst'.
|
|
|
|
|
New value is necessarily <= old value.
|
|
|
|
|
return : Nb bytes written into 'dst' (necessarily <= targetDestSize)
|
|
|
|
|
or 0 if compression fails
|
2016-11-10 16:22:26 +00:00
|
|
|
</p></pre><BR>
|
|
|
|
|
|
2017-11-20 18:27:05 +00:00
|
|
|
<pre><b>int LZ4_decompress_fast (const char* src, char* dst, int originalSize);
|
2018-02-07 10:21:25 +00:00
|
|
|
</b><p>This function is a bit faster than LZ4_decompress_safe(),
|
2018-04-27 16:04:09 +00:00
|
|
|
but it may misbehave on malformed input because it doesn't perform full validation of compressed data.
|
2018-02-07 10:21:25 +00:00
|
|
|
originalSize : is the uncompressed size to regenerate
|
|
|
|
|
Destination buffer must be already allocated, and its size must be >= 'originalSize' bytes.
|
|
|
|
|
return : number of bytes read from source buffer (== compressed size).
|
|
|
|
|
If the source stream is detected malformed, the function stops decoding and return a negative result.
|
2018-04-27 16:04:09 +00:00
|
|
|
note : This function is only usable if the originalSize of uncompressed data is known in advance.
|
|
|
|
|
The caller should also check that all the compressed input has been consumed properly,
|
|
|
|
|
i.e. that the return value matches the size of the buffer with compressed input.
|
|
|
|
|
The function never writes past the output buffer. However, since it doesn't know its 'src' size,
|
|
|
|
|
it may read past the intended input. Also, because match offsets are not validated during decoding,
|
|
|
|
|
reads from 'src' may underflow. Use this function in trusted environment **only**.
|
2016-11-10 16:22:26 +00:00
|
|
|
</p></pre><BR>
|
|
|
|
|
|
2017-11-20 18:27:05 +00:00
|
|
|
<pre><b>int LZ4_decompress_safe_partial (const char* src, char* dst, int srcSize, int targetOutputSize, int dstCapacity);
|
|
|
|
|
</b><p> This function decompress a compressed block of size 'srcSize' at position 'src'
|
|
|
|
|
into destination buffer 'dst' of size 'dstCapacity'.
|
|
|
|
|
The function will decompress a minimum of 'targetOutputSize' bytes, and stop after that.
|
2018-02-07 10:21:25 +00:00
|
|
|
However, it's not accurate, and may write more than 'targetOutputSize' (but always <= dstCapacity).
|
2017-11-20 18:27:05 +00:00
|
|
|
@return : the number of bytes decoded in the destination buffer (necessarily <= dstCapacity)
|
2018-02-07 10:21:25 +00:00
|
|
|
Note : this number can also be < targetOutputSize, if compressed block contains less data.
|
|
|
|
|
Therefore, always control how many bytes were decoded.
|
|
|
|
|
If source stream is detected malformed, function returns a negative result.
|
|
|
|
|
This function is protected against malicious data packets.
|
2016-11-10 16:22:26 +00:00
|
|
|
</p></pre><BR>
|
|
|
|
|
|
2016-11-11 21:00:02 +00:00
|
|
|
<a name="Chapter6"></a><h2>Streaming Compression Functions</h2><pre></pre>
|
2016-11-10 16:22:26 +00:00
|
|
|
|
|
|
|
|
<pre><b>LZ4_stream_t* LZ4_createStream(void);
|
|
|
|
|
int LZ4_freeStream (LZ4_stream_t* streamPtr);
|
|
|
|
|
</b><p> LZ4_createStream() will allocate and initialize an `LZ4_stream_t` structure.
|
|
|
|
|
LZ4_freeStream() releases its memory.
|
2017-01-23 15:03:40 +00:00
|
|
|
|
|
|
|
|
</p></pre><BR>
|
|
|
|
|
|
|
|
|
|
<pre><b>void LZ4_resetStream (LZ4_stream_t* streamPtr);
|
|
|
|
|
</b><p> An LZ4_stream_t structure can be allocated once and re-used multiple times.
|
2017-08-30 23:09:10 +00:00
|
|
|
Use this function to start compressing a new stream.
|
2016-11-10 16:22:26 +00:00
|
|
|
|
|
|
|
|
</p></pre><BR>
|
|
|
|
|
|
|
|
|
|
<pre><b>int LZ4_loadDict (LZ4_stream_t* streamPtr, const char* dictionary, int dictSize);
|
2017-08-30 23:09:10 +00:00
|
|
|
</b><p> Use this function to load a static dictionary into LZ4_stream_t.
|
2016-11-10 16:22:26 +00:00
|
|
|
Any previous data will be forgotten, only 'dictionary' will remain in memory.
|
2017-08-30 23:09:10 +00:00
|
|
|
Loading a size of 0 is allowed, and is the same as reset.
|
|
|
|
|
@return : dictionary size, in bytes (necessarily <= 64 KB)
|
2016-11-10 16:22:26 +00:00
|
|
|
|
|
|
|
|
</p></pre><BR>
|
|
|
|
|
|
2017-05-10 20:26:04 +00:00
|
|
|
<pre><b>int LZ4_compress_fast_continue (LZ4_stream_t* streamPtr, const char* src, char* dst, int srcSize, int dstCapacity, int acceleration);
|
2018-02-26 21:31:18 +00:00
|
|
|
</b><p> Compress 'src' content using data from previously compressed blocks, for better compression ratio.
|
2016-11-10 16:22:26 +00:00
|
|
|
'dst' buffer must be already allocated.
|
2017-05-10 20:26:04 +00:00
|
|
|
If dstCapacity >= LZ4_compressBound(srcSize), compression is guaranteed to succeed, and runs faster.
|
2017-08-30 23:09:10 +00:00
|
|
|
|
2018-02-26 21:31:18 +00:00
|
|
|
Important : The previous 64KB of compressed data is assumed to remain present and unmodified in memory!
|
|
|
|
|
|
2018-02-18 19:00:33 +00:00
|
|
|
Special 1 : When input is a double-buffer, they can have any size, including < 64 KB.
|
|
|
|
|
Make sure that buffers are separated by at least one byte.
|
2018-02-26 21:31:18 +00:00
|
|
|
This way, each block only depends on previous block.
|
2018-01-31 22:33:16 +00:00
|
|
|
Special 2 : If input buffer is a ring-buffer, it can have any size, including < 64 KB.
|
2017-08-30 23:09:10 +00:00
|
|
|
|
|
|
|
|
@return : size of compressed block
|
2018-02-26 21:31:18 +00:00
|
|
|
or 0 if there is an error (typically, cannot fit into 'dst').
|
2017-08-10 07:48:19 +00:00
|
|
|
After an error, the stream status is invalid, it can only be reset or freed.
|
2016-11-10 16:22:26 +00:00
|
|
|
|
|
|
|
|
</p></pre><BR>
|
|
|
|
|
|
2018-02-26 21:31:18 +00:00
|
|
|
<pre><b>int LZ4_saveDict (LZ4_stream_t* streamPtr, char* safeBuffer, int maxDictSize);
|
|
|
|
|
</b><p> If last 64KB data cannot be guaranteed to remain available at its current memory location,
|
2016-11-10 16:22:26 +00:00
|
|
|
save it into a safer place (char* safeBuffer).
|
2018-02-26 21:31:18 +00:00
|
|
|
This is schematically equivalent to a memcpy() followed by LZ4_loadDict(),
|
|
|
|
|
but is much faster, because LZ4_saveDict() doesn't need to rebuild tables.
|
|
|
|
|
@return : saved dictionary size in bytes (necessarily <= maxDictSize), or 0 if error.
|
2016-11-10 16:22:26 +00:00
|
|
|
|
|
|
|
|
</p></pre><BR>
|
|
|
|
|
|
2017-01-23 15:03:40 +00:00
|
|
|
<a name="Chapter7"></a><h2>Streaming Decompression Functions</h2><pre> Bufferless synchronous API
|
|
|
|
|
<BR></pre>
|
2016-11-10 16:22:26 +00:00
|
|
|
|
|
|
|
|
<pre><b>LZ4_streamDecode_t* LZ4_createStreamDecode(void);
|
|
|
|
|
int LZ4_freeStreamDecode (LZ4_streamDecode_t* LZ4_stream);
|
2018-05-02 23:05:42 +00:00
|
|
|
</b><p> creation / destruction of streaming decompression tracking context.
|
|
|
|
|
A tracking context can be re-used multiple times.
|
|
|
|
|
|
2016-11-10 16:22:26 +00:00
|
|
|
</p></pre><BR>
|
|
|
|
|
|
|
|
|
|
<pre><b>int LZ4_setStreamDecode (LZ4_streamDecode_t* LZ4_streamDecode, const char* dictionary, int dictSize);
|
2018-05-02 23:05:42 +00:00
|
|
|
</b><p> An LZ4_streamDecode_t context can be allocated once and re-used multiple times.
|
2017-08-30 23:09:10 +00:00
|
|
|
Use this function to start decompression of a new stream of blocks.
|
2018-07-29 02:12:55 +00:00
|
|
|
A dictionary can optionally be set. Use NULL or size 0 for a reset order.
|
2018-05-02 23:05:42 +00:00
|
|
|
Dictionary is presumed stable : it must remain accessible and unmodified during next decompression.
|
2017-08-30 22:42:04 +00:00
|
|
|
@return : 1 if OK, 0 if error
|
2016-11-10 16:22:26 +00:00
|
|
|
|
|
|
|
|
</p></pre><BR>
|
|
|
|
|
|
2018-05-02 23:05:42 +00:00
|
|
|
<pre><b>int LZ4_decoderRingBufferSize(int maxBlockSize);
|
|
|
|
|
#define LZ4_DECODER_RING_BUFFER_SIZE(mbs) (65536 + 14 + (mbs)) </b>/* for static allocation; mbs presumed valid */<b>
|
|
|
|
|
</b><p> Note : in a ring buffer scenario (optional),
|
|
|
|
|
blocks are presumed decompressed next to each other
|
|
|
|
|
up to the moment there is not enough remaining space for next block (remainingSize < maxBlockSize),
|
|
|
|
|
at which stage it resumes from beginning of ring buffer.
|
|
|
|
|
When setting such a ring buffer for streaming decompression,
|
|
|
|
|
provides the minimum size of this ring buffer
|
|
|
|
|
to be compatible with any source respecting maxBlockSize condition.
|
|
|
|
|
@return : minimum ring buffer size,
|
|
|
|
|
or 0 if there is an error (invalid maxBlockSize).
|
|
|
|
|
|
|
|
|
|
</p></pre><BR>
|
|
|
|
|
|
2017-11-20 18:27:05 +00:00
|
|
|
<pre><b>int LZ4_decompress_safe_continue (LZ4_streamDecode_t* LZ4_streamDecode, const char* src, char* dst, int srcSize, int dstCapacity);
|
|
|
|
|
int LZ4_decompress_fast_continue (LZ4_streamDecode_t* LZ4_streamDecode, const char* src, char* dst, int originalSize);
|
2017-08-30 22:42:04 +00:00
|
|
|
</b><p> These decoding functions allow decompression of consecutive blocks in "streaming" mode.
|
|
|
|
|
A block is an unsplittable entity, it must be presented entirely to a decompression function.
|
2018-05-02 23:05:42 +00:00
|
|
|
Decompression functions only accepts one block at a time.
|
2018-02-07 10:21:25 +00:00
|
|
|
The last 64KB of previously decoded data *must* remain available and unmodified at the memory position where they were decoded.
|
2018-05-02 23:05:42 +00:00
|
|
|
If less than 64KB of data has been decoded, all the data must be present.
|
|
|
|
|
|
|
|
|
|
Special : if decompression side sets a ring buffer, it must respect one of the following conditions :
|
|
|
|
|
- Decompression buffer size is _at least_ LZ4_decoderRingBufferSize(maxBlockSize).
|
|
|
|
|
maxBlockSize is the maximum size of any single block. It can have any value > 16 bytes.
|
|
|
|
|
In which case, encoding and decoding buffers do not need to be synchronized.
|
|
|
|
|
Actually, data can be produced by any source compliant with LZ4 format specification, and respecting maxBlockSize.
|
|
|
|
|
- Synchronized mode :
|
|
|
|
|
Decompression buffer size is _exactly_ the same as compression buffer size,
|
|
|
|
|
and follows exactly same update rule (block boundaries at same positions),
|
|
|
|
|
and decoding function is provided with exact decompressed size of each block (exception for last block of the stream),
|
|
|
|
|
_then_ decoding & encoding ring buffer can have any size, including small ones ( < 64 KB).
|
|
|
|
|
- Decompression buffer is larger than encoding buffer, by a minimum of maxBlockSize more bytes.
|
2017-08-10 07:48:19 +00:00
|
|
|
In which case, encoding and decoding buffers do not need to be synchronized,
|
|
|
|
|
and encoding ring buffer can have any size, including small ones ( < 64 KB).
|
2018-05-02 23:05:42 +00:00
|
|
|
|
|
|
|
|
Whenever these conditions are not possible,
|
|
|
|
|
save the last 64KB of decoded data into a safe buffer where it can't be modified during decompression,
|
|
|
|
|
then indicate where this data is saved using LZ4_setStreamDecode(), before decompressing next block.
|
2016-11-10 16:22:26 +00:00
|
|
|
</p></pre><BR>
|
|
|
|
|
|
2017-11-20 18:27:05 +00:00
|
|
|
<pre><b>int LZ4_decompress_safe_usingDict (const char* src, char* dst, int srcSize, int dstCapcity, const char* dictStart, int dictSize);
|
|
|
|
|
int LZ4_decompress_fast_usingDict (const char* src, char* dst, int originalSize, const char* dictStart, int dictSize);
|
2017-01-23 15:03:40 +00:00
|
|
|
</b><p> These decoding functions work the same as
|
|
|
|
|
a combination of LZ4_setStreamDecode() followed by LZ4_decompress_*_continue()
|
|
|
|
|
They are stand-alone, and don't need an LZ4_streamDecode_t structure.
|
2018-05-02 23:05:42 +00:00
|
|
|
Dictionary is presumed stable : it must remain accessible and unmodified during next decompression.
|
2017-01-23 15:03:40 +00:00
|
|
|
|
|
|
|
|
</p></pre><BR>
|
|
|
|
|
|
2018-04-13 08:01:54 +00:00
|
|
|
<a name="Chapter8"></a><h2>Unstable declarations</h2><pre>
|
|
|
|
|
Declarations in this section should be considered unstable.
|
|
|
|
|
Use at your own peril, etc., etc.
|
|
|
|
|
They may be removed in the future.
|
|
|
|
|
Their signatures may change.
|
|
|
|
|
<BR></pre>
|
|
|
|
|
|
|
|
|
|
<pre><b>void LZ4_resetStream_fast (LZ4_stream_t* streamPtr);
|
2018-05-03 22:40:01 +00:00
|
|
|
</b><p> Use this, like LZ4_resetStream(), to prepare a context for a new chain of
|
|
|
|
|
calls to a streaming API (e.g., LZ4_compress_fast_continue()).
|
|
|
|
|
|
|
|
|
|
Note:
|
|
|
|
|
Using this in advance of a non- streaming-compression function is redundant,
|
|
|
|
|
and potentially bad for performance, since they all perform their own custom
|
|
|
|
|
reset internally.
|
|
|
|
|
|
|
|
|
|
Differences from LZ4_resetStream():
|
|
|
|
|
When an LZ4_stream_t is known to be in a internally coherent state,
|
2018-04-13 08:01:54 +00:00
|
|
|
it can often be prepared for a new compression with almost no work, only
|
|
|
|
|
sometimes falling back to the full, expensive reset that is always required
|
|
|
|
|
when the stream is in an indeterminate state (i.e., the reset performed by
|
|
|
|
|
LZ4_resetStream()).
|
|
|
|
|
|
|
|
|
|
LZ4_streams are guaranteed to be in a valid state when:
|
|
|
|
|
- returned from LZ4_createStream()
|
|
|
|
|
- reset by LZ4_resetStream()
|
2018-05-03 22:40:01 +00:00
|
|
|
- memset(stream, 0, sizeof(LZ4_stream_t)), though this is discouraged
|
2018-04-13 08:01:54 +00:00
|
|
|
- the stream was in a valid state and was reset by LZ4_resetStream_fast()
|
|
|
|
|
- the stream was in a valid state and was then used in any compression call
|
|
|
|
|
that returned success
|
|
|
|
|
- the stream was in an indeterminate state and was used in a compression
|
2018-05-03 22:40:01 +00:00
|
|
|
call that fully reset the state (e.g., LZ4_compress_fast_extState()) and
|
|
|
|
|
that returned success
|
|
|
|
|
|
|
|
|
|
When a stream isn't known to be in a valid state, it is not safe to pass to
|
|
|
|
|
any fastReset or streaming function. It must first be cleansed by the full
|
|
|
|
|
LZ4_resetStream().
|
2018-04-13 08:01:54 +00:00
|
|
|
|
|
|
|
|
</p></pre><BR>
|
|
|
|
|
|
|
|
|
|
<pre><b>int LZ4_compress_fast_extState_fastReset (void* state, const char* src, char* dst, int srcSize, int dstCapacity, int acceleration);
|
|
|
|
|
</b><p> A variant of LZ4_compress_fast_extState().
|
|
|
|
|
|
|
|
|
|
Using this variant avoids an expensive initialization step. It is only safe
|
|
|
|
|
to call if the state buffer is known to be correctly initialized already
|
|
|
|
|
(see above comment on LZ4_resetStream_fast() for a definition of "correctly
|
|
|
|
|
initialized"). From a high level, the difference is that this function
|
2018-05-03 22:40:01 +00:00
|
|
|
initializes the provided state with a call to something like
|
|
|
|
|
LZ4_resetStream_fast() while LZ4_compress_fast_extState() starts with a
|
|
|
|
|
call to LZ4_resetStream().
|
2018-04-13 08:01:54 +00:00
|
|
|
|
|
|
|
|
</p></pre><BR>
|
|
|
|
|
|
|
|
|
|
<pre><b>void LZ4_attach_dictionary(LZ4_stream_t *working_stream, const LZ4_stream_t *dictionary_stream);
|
|
|
|
|
</b><p> This is an experimental API that allows for the efficient use of a
|
|
|
|
|
static dictionary many times.
|
|
|
|
|
|
|
|
|
|
Rather than re-loading the dictionary buffer into a working context before
|
|
|
|
|
each compression, or copying a pre-loaded dictionary's LZ4_stream_t into a
|
|
|
|
|
working LZ4_stream_t, this function introduces a no-copy setup mechanism,
|
|
|
|
|
in which the working stream references the dictionary stream in-place.
|
|
|
|
|
|
|
|
|
|
Several assumptions are made about the state of the dictionary stream.
|
|
|
|
|
Currently, only streams which have been prepared by LZ4_loadDict() should
|
|
|
|
|
be expected to work.
|
|
|
|
|
|
|
|
|
|
Alternatively, the provided dictionary stream pointer may be NULL, in which
|
|
|
|
|
case any existing dictionary stream is unset.
|
|
|
|
|
|
|
|
|
|
If a dictionary is provided, it replaces any pre-existing stream history.
|
|
|
|
|
The dictionary contents are the only history that can be referenced and
|
|
|
|
|
logically immediately precede the data compressed in the first subsequent
|
|
|
|
|
compression call.
|
|
|
|
|
|
|
|
|
|
The dictionary will only remain attached to the working stream through the
|
|
|
|
|
first compression call, at the end of which it is cleared. The dictionary
|
|
|
|
|
stream (and source buffer) must remain in-place / accessible / unchanged
|
|
|
|
|
through the completion of the first compression call on the stream.
|
|
|
|
|
|
|
|
|
|
</p></pre><BR>
|
|
|
|
|
|
|
|
|
|
<a name="Chapter9"></a><h2>Private definitions</h2><pre>
|
2017-01-23 15:03:40 +00:00
|
|
|
Do not use these definitions.
|
|
|
|
|
They are exposed to allow static allocation of `LZ4_stream_t` and `LZ4_streamDecode_t`.
|
|
|
|
|
Using these definitions will expose code to API and/or ABI break in future versions of the library.
|
|
|
|
|
<BR></pre>
|
|
|
|
|
|
|
|
|
|
<pre><b>typedef struct {
|
|
|
|
|
const uint8_t* externalDict;
|
|
|
|
|
size_t extDictSize;
|
|
|
|
|
const uint8_t* prefixEnd;
|
|
|
|
|
size_t prefixSize;
|
|
|
|
|
} LZ4_streamDecode_t_internal;
|
|
|
|
|
</b></pre><BR>
|
|
|
|
|
<pre><b>typedef struct {
|
|
|
|
|
const unsigned char* externalDict;
|
|
|
|
|
size_t extDictSize;
|
|
|
|
|
const unsigned char* prefixEnd;
|
|
|
|
|
size_t prefixSize;
|
|
|
|
|
} LZ4_streamDecode_t_internal;
|
|
|
|
|
</b></pre><BR>
|
|
|
|
|
<pre><b>#define LZ4_STREAMSIZE_U64 ((1 << (LZ4_MEMORY_USAGE-3)) + 4)
|
|
|
|
|
#define LZ4_STREAMSIZE (LZ4_STREAMSIZE_U64 * sizeof(unsigned long long))
|
|
|
|
|
union LZ4_stream_u {
|
|
|
|
|
unsigned long long table[LZ4_STREAMSIZE_U64];
|
|
|
|
|
LZ4_stream_t_internal internal_donotuse;
|
|
|
|
|
} ; </b>/* previously typedef'd to LZ4_stream_t */<b>
|
|
|
|
|
</b><p> information structure to track an LZ4 stream.
|
|
|
|
|
init this structure before first use.
|
|
|
|
|
note : only use in association with static linking !
|
|
|
|
|
this definition is not API/ABI safe,
|
2017-08-09 23:51:19 +00:00
|
|
|
it may change in a future version !
|
2017-01-23 15:03:40 +00:00
|
|
|
|
|
|
|
|
</p></pre><BR>
|
|
|
|
|
|
|
|
|
|
<pre><b>#define LZ4_STREAMDECODESIZE_U64 4
|
|
|
|
|
#define LZ4_STREAMDECODESIZE (LZ4_STREAMDECODESIZE_U64 * sizeof(unsigned long long))
|
|
|
|
|
union LZ4_streamDecode_u {
|
|
|
|
|
unsigned long long table[LZ4_STREAMDECODESIZE_U64];
|
|
|
|
|
LZ4_streamDecode_t_internal internal_donotuse;
|
|
|
|
|
} ; </b>/* previously typedef'd to LZ4_streamDecode_t */<b>
|
|
|
|
|
</b><p> information structure to track an LZ4 stream during decompression.
|
|
|
|
|
init this structure using LZ4_setStreamDecode (or memset()) before first use
|
|
|
|
|
note : only use in association with static linking !
|
|
|
|
|
this definition is not API/ABI safe,
|
|
|
|
|
and may change in a future version !
|
|
|
|
|
|
|
|
|
|
</p></pre><BR>
|
|
|
|
|
|
2018-04-13 08:01:54 +00:00
|
|
|
<a name="Chapter10"></a><h2>Obsolete Functions</h2><pre></pre>
|
2017-01-23 15:03:40 +00:00
|
|
|
|
|
|
|
|
<pre><b>#ifdef LZ4_DISABLE_DEPRECATE_WARNINGS
|
|
|
|
|
# define LZ4_DEPRECATED(message) </b>/* disable deprecation warnings */<b>
|
|
|
|
|
#else
|
|
|
|
|
# define LZ4_GCC_VERSION (__GNUC__ * 100 + __GNUC_MINOR__)
|
2018-02-07 10:21:25 +00:00
|
|
|
# if defined (__cplusplus) && (__cplusplus >= 201402) </b>/* C++14 or greater */<b>
|
2017-01-23 15:03:40 +00:00
|
|
|
# define LZ4_DEPRECATED(message) [[deprecated(message)]]
|
2018-02-07 10:21:25 +00:00
|
|
|
# elif (LZ4_GCC_VERSION >= 405) || defined(__clang__)
|
2017-01-23 15:03:40 +00:00
|
|
|
# define LZ4_DEPRECATED(message) __attribute__((deprecated(message)))
|
|
|
|
|
# elif (LZ4_GCC_VERSION >= 301)
|
|
|
|
|
# define LZ4_DEPRECATED(message) __attribute__((deprecated))
|
|
|
|
|
# elif defined(_MSC_VER)
|
|
|
|
|
# define LZ4_DEPRECATED(message) __declspec(deprecated(message))
|
|
|
|
|
# else
|
|
|
|
|
# pragma message("WARNING: You need to implement LZ4_DEPRECATED for this compiler")
|
|
|
|
|
# define LZ4_DEPRECATED(message)
|
|
|
|
|
# endif
|
|
|
|
|
#endif </b>/* LZ4_DISABLE_DEPRECATE_WARNINGS */<b>
|
|
|
|
|
</b><p> Should deprecation warnings be a problem,
|
|
|
|
|
it is generally possible to disable them,
|
|
|
|
|
typically with -Wno-deprecated-declarations for gcc
|
|
|
|
|
or _CRT_SECURE_NO_WARNINGS in Visual.
|
|
|
|
|
Otherwise, it's also possible to define LZ4_DISABLE_DEPRECATE_WARNINGS
|
2016-11-10 16:22:26 +00:00
|
|
|
</p></pre><BR>
|
|
|
|
|
|
|
|
|
|
</html>
|
|
|
|
|
</body>
|
