Class LZ4
- java.lang.Object
-
- org.lwjgl.util.lz4.LZ4
-
public class LZ4 extends java.lang.Object
Native bindings to LZ4, a lossless compression algorithm, providing compression speed > 500 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.Speed can be tuned dynamically, selecting an "acceleration" factor which trades compression ratio for faster speed. On the other end, a high compression derivative,
LZ4_HC
, is also provided, trading CPU time for improved compression ratio. All versions feature the same decompression speed.LZ4 is also compatible with dictionary compression, and can ingest any input file as dictionary, including those created by Zstandard Dictionary Builder. (note: only the final 64KB are used).
The raw LZ4 block compression format is detailed within lz4_Block_format.
Arbitrarily long files or data streams are compressed using multiple blocks, for streaming requirements. These blocks are organized into a frame, defined into lz4_Frame_format. Interoperable versions of LZ4 must also respect the frame format.
In-place compression and decompression
It's possible to have input and output sharing the same buffer, for highly contrained memory environments. In both cases, it requires input to lay at the end of the buffer, and decompression to start at beginning of the buffer. Buffer size must feature some margin, hence be larger than final size.
|<------------------------buffer--------------------------------->| |<-----------compressed data--------->| |<-----------decompressed size------------------>| |<----margin---->|
This technique is more useful for decompression, since decompressed size is typically larger, and margin is short.
In-place decompression will work inside any buffer which size is ≥
LZ4_DECOMPRESS_INPLACE_BUFFER_SIZE(decompressedSize)
. This presumes thatdecompressedSize
>compressedSize
. Otherwise, it means compression actually expanded data, and it would be more efficient to store such data with a flag indicating it's not compressed. This can happen when data is not compressible (already compressed, or encrypted).For in-place compression, margin is larger, as it must be able to cope with both history preservation, requiring input data to remain unmodified up to
DISTANCE_MAX
, and data expansion, which can happen when input is not compressible. As a consequence, buffer size requirements are much higher, and memory savings offered by in-place compression are more limited.There are ways to limit this cost for compression:
- Reduce history size, by modifying
LZ4_DISTANCE_MAX
. Note that it is a compile-time constant, so all compressions will apply this limit. Lower values will reduce compression ratio, except when input_size <LZ4_DISTANCE_MAX
, so it's a reasonable trick when inputs are known to be small. - Require the compressor to deliver a "maximum compressed size". This is the
dstCapacity
parameter inLZ4_compress*()
. When this size is <LZ4_COMPRESSBOUND(inputSize)
, then compression can fail, in which case, the return code will be 0 (zero). The caller must be ready for these cases to happen, and typically design a backup scheme to send data uncompressed.
The combination of both techniques can significantly reduce the amount of margin required for in-place compression.
In-place compression can work in any buffer which size is ≥
(maxCompressedSize)
withmaxCompressedSize == LZ4_COMPRESSBOUND(srcSize)
for guaranteed compression success.COMPRESS_INPLACE_BUFFER_SIZE
depends on bothmaxCompressedSize
andLZ4_DISTANCE_MAX
, so it's possible to reduce memory requirements by playing with them. - Reduce history size, by modifying
-
-
Field Summary
Fields Modifier and Type Field Description static int
LZ4_DISTANCE_MAX
History window size; can be user-defined at compile time.static int
LZ4_HASH_SIZE_U32
LZ4_HASHLOG
LZ4_HASHTABLESIZEstatic int
LZ4_MAX_INPUT_SIZE
Maximum input size.static int
LZ4_MEMORY_USAGE
Memory usage formula :N->2^N
Bytes (examples:10 -> 1KB; 12 -> 4KB ; 16 -> 64KB; 20 -> 1MB;
etc.)static int
LZ4_STREAMDECODESIZE
LZ4_STREAMDECODESIZE_U64
LZ4_STREAMSIZE
LZ4_STREAMSIZE_U64static int
LZ4_VERSION_MAJOR
LZ4_VERSION_MINORVersion number part.static int
LZ4_VERSION_NUMBER
Version number.static int
LZ4_VERSION_RELEASE
Version number part.static java.lang.String
LZ4_VERSION_STRING
Version string.
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Method Summary
All Methods Static Methods Concrete Methods Modifier and Type Method Description static void
LZ4_attach_dictionary(long workingStream, long dictionaryStream)
This is an experimental API that allows efficient use of a static dictionary many times.static int
LZ4_compress_default(java.nio.ByteBuffer src, java.nio.ByteBuffer dst)
CompressessrcSize
bytes from buffersrc
into already allocateddst
buffer of sizedstCapacity
.static int
LZ4_compress_destSize(java.nio.ByteBuffer src, java.nio.ByteBuffer dst, java.nio.IntBuffer srcSizePtr)
Reverse the logic: compresses as much data as possible fromsrc
buffer into already allocated bufferdst
of sizetargetDstSize
.static int
LZ4_compress_fast(java.nio.ByteBuffer src, java.nio.ByteBuffer dst, int acceleration)
Same ascompress_default
, but allows selection of "acceleration" factor.static int
LZ4_compress_fast_continue(long streamPtr, java.nio.ByteBuffer src, java.nio.ByteBuffer dst, int acceleration)
Compresssrc
content using data from previously compressed blocks, for better compression ratio.static int
LZ4_compress_fast_extState(java.nio.ByteBuffer state, java.nio.ByteBuffer src, java.nio.ByteBuffer dst, int acceleration)
Same ascompress_fast
, using an externally allocated memory space for its state.static int
LZ4_compress_fast_extState_fastReset(java.nio.ByteBuffer state, java.nio.ByteBuffer src, java.nio.ByteBuffer dst, int acceleration)
A variant ofcompress_fast_extState
.static int
LZ4_COMPRESS_INPLACE_BUFFER_SIZE(int maxCompressedSize)
static int
LZ4_COMPRESS_INPLACE_MARGIN()
static int
LZ4_compressBound(int inputSize)
Provides the maximum size that LZ4 compression may output in a "worst case" scenario (input data not compressible).static int
LZ4_COMPRESSBOUND(int isize)
SeecompressBound
.static long
LZ4_createStream()
Allocates and initializes anLZ4_stream_t
structure.static long
LZ4_createStreamDecode()
Creates a streaming decompression tracking context.static int
LZ4_DECODER_RING_BUFFER_SIZE(int maxBlockSize)
For static allocation;maxBlockSize
presumed valid.static int
LZ4_decoderRingBufferSize(int maxBlockSize)
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.static int
LZ4_DECOMPRESS_INPLACE_BUFFER_SIZE(int decompressedSize)
Note: presumes thatcompressedSize
<decompressedSize
.static int
LZ4_DECOMPRESS_INPLACE_MARGIN(int compressedSize)
static int
LZ4_decompress_safe(java.nio.ByteBuffer src, java.nio.ByteBuffer dst)
If destination buffer is not large enough, decoding will stop and output an error code (negative value).static int
LZ4_decompress_safe_continue(long LZ4_streamDecode, java.nio.ByteBuffer src, java.nio.ByteBuffer dst)
These decoding functions allow decompression of consecutive blocks in "streaming" mode.static int
LZ4_decompress_safe_partial(java.nio.ByteBuffer src, java.nio.ByteBuffer dst, int targetOutputSize)
Decompresses an LZ4 compressed block, of sizesrcSize
at positionsrc
, into destination bufferdst
of sizedstCapacity
.static int
LZ4_decompress_safe_usingDict(java.nio.ByteBuffer src, java.nio.ByteBuffer dst, java.nio.ByteBuffer dictStart)
These decoding functions work the same as a combination ofsetStreamDecode
followed byLZ4_decompress_*_continue()
.static int
LZ4_freeStream(long streamPtr)
Releases memory of anLZ4_stream_t
structure.static int
LZ4_freeStreamDecode(long LZ4_stream)
Frees a streaming decompression tracking context.static long
LZ4_initStream(java.nio.ByteBuffer buffer)
AnLZ4_stream_t
structure must be initialized at least once.static int
LZ4_loadDict(long streamPtr, java.nio.ByteBuffer dictionary)
Use this function to reference a static dictionary intoLZ4_stream_t
.static void
LZ4_resetStream_fast(long streamPtr)
Use this to prepare anLZ4_stream_t
for a new chain of dependent blocks (e.g.,compress_fast_continue
).static int
LZ4_saveDict(long streamPtr, java.nio.ByteBuffer safeBuffer)
If last 64KB data cannot be guaranteed to remain available at its current memory location, save it into a safer place (char* safeBuffer
).static boolean
LZ4_setStreamDecode(long LZ4_streamDecode, java.nio.ByteBuffer dictionary)
AnLZ4_streamDecode_t
context can be allocated once and re-used multiple times.static int
LZ4_sizeofState()
static int
LZ4_versionNumber()
Returns the version number.static java.lang.String
LZ4_versionString()
Returns the version string.static void
nLZ4_attach_dictionary(long workingStream, long dictionaryStream)
Unsafe version of:attach_dictionary
static int
nLZ4_compress_default(long src, long dst, int srcSize, int dstCapacity)
Unsafe version of:compress_default
static int
nLZ4_compress_destSize(long src, long dst, long srcSizePtr, int targetDstSize)
Unsafe version of:compress_destSize
static int
nLZ4_compress_fast(long src, long dst, int srcSize, int dstCapacity, int acceleration)
Unsafe version of:compress_fast
static int
nLZ4_compress_fast_continue(long streamPtr, long src, long dst, int srcSize, int dstCapacity, int acceleration)
Unsafe version of:compress_fast_continue
static int
nLZ4_compress_fast_extState(long state, long src, long dst, int srcSize, int dstCapacity, int acceleration)
Unsafe version of:compress_fast_extState
static int
nLZ4_compress_fast_extState_fastReset(long state, long src, long dst, int srcSize, int dstCapacity, int acceleration)
Unsafe version of:compress_fast_extState_fastReset
static int
nLZ4_decompress_safe(long src, long dst, int compressedSize, int dstCapacity)
Unsafe version of:decompress_safe
static int
nLZ4_decompress_safe_continue(long LZ4_streamDecode, long src, long dst, int srcSize, int dstCapacity)
Unsafe version of:decompress_safe_continue
static int
nLZ4_decompress_safe_partial(long src, long dst, int compressedSize, int targetOutputSize, int dstCapacity)
Unsafe version of:decompress_safe_partial
static int
nLZ4_decompress_safe_usingDict(long src, long dst, int srcSize, int dstCapacity, long dictStart, int dictSize)
Unsafe version of:decompress_safe_usingDict
static int
nLZ4_freeStream(long streamPtr)
Unsafe version of:freeStream
static int
nLZ4_freeStreamDecode(long LZ4_stream)
Unsafe version of:freeStreamDecode
static long
nLZ4_initStream(long buffer, long size)
Unsafe version of:initStream
static int
nLZ4_loadDict(long streamPtr, long dictionary, int dictSize)
Unsafe version of:loadDict
static void
nLZ4_resetStream_fast(long streamPtr)
Unsafe version of:resetStream_fast
static int
nLZ4_saveDict(long streamPtr, long safeBuffer, int maxDictSize)
Unsafe version of:saveDict
static int
nLZ4_setStreamDecode(long LZ4_streamDecode, long dictionary, int dictSize)
Unsafe version of:setStreamDecode
static long
nLZ4_versionString()
Unsafe version of:versionString
-
-
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Field Detail
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LZ4_VERSION_MAJOR, LZ4_VERSION_MINOR, LZ4_VERSION_RELEASE
Version number part.
-
LZ4_VERSION_NUMBER
Version number.
-
LZ4_VERSION_STRING
Version string.
-
LZ4_MAX_INPUT_SIZE
Maximum input size.
-
LZ4_MEMORY_USAGE
Memory usage formula :N->2^N
Bytes (examples:10 -> 1KB; 12 -> 4KB ; 16 -> 64KB; 20 -> 1MB;
etc.)Increasing memory usage improves compression ratio. Reduced memory usage may improve speed, thanks to better cache locality. Default value is 14, for 16KB, which nicely fits into Intel x86 L1 cache.
-
LZ4_HASHLOG
- See Also:
- Constant Field Values
-
LZ4_HASHTABLESIZE
- See Also:
- Constant Field Values
-
LZ4_HASH_SIZE_U32
- See Also:
- Constant Field Values
-
LZ4_STREAMSIZE_U64
-
LZ4_STREAMSIZE
public static final int LZ4_STREAMSIZE
-
LZ4_STREAMDECODESIZE_U64
-
LZ4_STREAMDECODESIZE
public static final int LZ4_STREAMDECODESIZE
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LZ4_DISTANCE_MAX
History window size; can be user-defined at compile time.
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-
Method Detail
-
LZ4_versionNumber
public static int LZ4_versionNumber()
Returns the version number.
-
nLZ4_versionString
public static long nLZ4_versionString()
Unsafe version of:versionString
-
LZ4_versionString
public static java.lang.String LZ4_versionString()
Returns the version string.
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nLZ4_compress_default
public static int nLZ4_compress_default(long src, long dst, int srcSize, int dstCapacity)
Unsafe version of:compress_default
- Parameters:
srcSize
- max supported value isMAX_INPUT_SIZE
dstCapacity
- size of bufferdst
(which must be already allocated)
-
LZ4_compress_default
public static int LZ4_compress_default(java.nio.ByteBuffer src, java.nio.ByteBuffer dst)
CompressessrcSize
bytes from buffersrc
into already allocateddst
buffer of sizedstCapacity
.Compression is guaranteed to succeed if
dstCapacity
≥compressBound
(srcSize)
. It also runs faster, so it's a recommended setting.If the function cannot compress
src
into a more limiteddst
budget, compression stops immediately, and the function result is zero. In which case,dst
content is undefined (invalid).This function is protected against buffer overflow scenarios (never writes outside
dst
buffer, nor read outsidesrc
buffer).- Returns:
- the number of bytes written into buffer
dest
(necessarily ≤maxOutputSize
) or 0 if compression fails
-
nLZ4_decompress_safe
public static int nLZ4_decompress_safe(long src, long dst, int compressedSize, int dstCapacity)
Unsafe version of:decompress_safe
- Parameters:
compressedSize
- is the exact complete size of the compressed blockdstCapacity
- is the size of destination buffer (which must be already allocated), presumed an upper bound of decompressed size
-
LZ4_decompress_safe
public static int LZ4_decompress_safe(java.nio.ByteBuffer src, java.nio.ByteBuffer dst)
If destination buffer is not large enough, decoding will stop and output an error code (negative value).If the source stream is detected malformed, the function will stop decoding and return a negative result.
Note 1: This function is protected against malicious data packets: it will never write outside
dst
buffer, nor read outsidesource
buffer, even if the compressed block is maliciously modified to order the decoder to do these actions. In such case, the decoder stops immediately, and considers the compressed block malformed.Note 2:
compressedSize
anddstCapacity
must be provided to the function, the compressed block does not contain them. The implementation is free to send / store / derive this information in whichever way is most beneficial. If there is a need for a different format which bundles together both compressed data and its metadata, consider looking atlz4frame.h
instead.- Returns:
- the number of bytes decompressed into destination buffer (necessarily ≤
dstCapacity
)
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LZ4_COMPRESSBOUND
public static int LZ4_COMPRESSBOUND(int isize)
SeecompressBound
.
-
LZ4_compressBound
public static int LZ4_compressBound(int inputSize)
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
COMPRESSBOUND
is also provided for compilation-time evaluation (stack memory allocation for example).Note that
compress_default
compresses faster whendstCapacity
is ≥compressBound
(srcSize)
- Parameters:
inputSize
- max supported value isMAX_INPUT_SIZE
- Returns:
- maximum output size in a "worst case" scenario or 0, if input size is incorrect (too large or negative)
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nLZ4_compress_fast
public static int nLZ4_compress_fast(long src, long dst, int srcSize, int dstCapacity, int acceleration)
Unsafe version of:compress_fast
-
LZ4_compress_fast
public static int LZ4_compress_fast(java.nio.ByteBuffer src, java.nio.ByteBuffer dst, int acceleration)
Same ascompress_default
, but allows selection of "acceleration" factor.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
compress_default
. Values ≤ 0 will be replaced byACCELERATION_DEFAULT
(currently == 1, see lz4.c).
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LZ4_sizeofState
public static int LZ4_sizeofState()
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nLZ4_compress_fast_extState
public static int nLZ4_compress_fast_extState(long state, long src, long dst, int srcSize, int dstCapacity, int acceleration)
Unsafe version of:compress_fast_extState
-
LZ4_compress_fast_extState
public static int LZ4_compress_fast_extState(java.nio.ByteBuffer state, java.nio.ByteBuffer src, java.nio.ByteBuffer dst, int acceleration)
Same ascompress_fast
, using an externally allocated memory space for its state.Use
sizeofState
to know how much memory must be allocated, and allocate it on 8-bytes boundaries (usingmalloc()
typically). Then, provide it asvoid* state
to compression function.
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nLZ4_compress_destSize
public static int nLZ4_compress_destSize(long src, long dst, long srcSizePtr, int targetDstSize)
Unsafe version of:compress_destSize
- Parameters:
srcSizePtr
- will be modified to indicate how many bytes where read fromsource
to filldest
. New value is necessarily ≤ input value.
-
LZ4_compress_destSize
public static int LZ4_compress_destSize(java.nio.ByteBuffer src, java.nio.ByteBuffer dst, java.nio.IntBuffer srcSizePtr)
Reverse the logic: compresses as much data as possible fromsrc
buffer into already allocated bufferdst
of sizetargetDstSize
.This function either compresses the entire
src
content intodst
if it's large enough, or filldst
buffer completely with as much data as possible fromsrc
. Note: acceleration parameter is fixed to"default"
.- Parameters:
srcSizePtr
- will be modified to indicate how many bytes where read fromsource
to filldest
. New value is necessarily ≤ input value.- Returns:
- nb bytes written into
dest
(necessarily ≤targetDestSize
) or 0 if compression fails
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nLZ4_decompress_safe_partial
public static int nLZ4_decompress_safe_partial(long src, long dst, int compressedSize, int targetOutputSize, int dstCapacity)
Unsafe version of:decompress_safe_partial
-
LZ4_decompress_safe_partial
public static int LZ4_decompress_safe_partial(java.nio.ByteBuffer src, java.nio.ByteBuffer dst, int targetOutputSize)
Decompresses an LZ4 compressed block, of sizesrcSize
at positionsrc
, into destination bufferdst
of sizedstCapacity
. Up totargetOutputSize
bytes will be decoded. The function stops decoding on reaching this objective, which can boost performance when only the beginning of a block is required.Note: this function features 2 parameters,
targetOutputSize
anddstCapacity
, and expectstargetOutputSize ≤ dstCapacity
. It effectively stops decoding on reachingtargetOutputSize
, sodstCapacity
is kind of redundant. This is because in a previous version of this function, decoding operation would not "break" a sequence in the middle. As a consequence, there was no guarantee that decoding would stop at exactlytargetOutputSize
, it could write more bytes, though only up todstCapacity
. Some "margin" used to be required for this operation to work properly. This is no longer necessary. The function nonetheless keeps its signature, in an effort to not break API.- Returns:
- the number of bytes decoded in
dst
(necessarily ≤dstCapacity
). If source stream is detected malformed, function returns a negative result.Note: can be <
targetOutputSize
, if compressed block contains less data.
-
LZ4_createStream
public static long LZ4_createStream()
Allocates and initializes anLZ4_stream_t
structure.
-
nLZ4_freeStream
public static int nLZ4_freeStream(long streamPtr)
Unsafe version of:freeStream
-
LZ4_freeStream
public static int LZ4_freeStream(long streamPtr)
Releases memory of anLZ4_stream_t
structure.
-
nLZ4_resetStream_fast
public static void nLZ4_resetStream_fast(long streamPtr)
Unsafe version of:resetStream_fast
-
LZ4_resetStream_fast
public static void LZ4_resetStream_fast(long streamPtr)
Use this to prepare anLZ4_stream_t
for a new chain of dependent blocks (e.g.,compress_fast_continue
).An
LZ4_stream_t
must be initialized once before usage. This is automatically done when created bycreateStream
. However, should theLZ4_stream_t
be simply declared on stack (for example), it's necessary to initialize it first, usinginitStream
.After init, start any new stream with
LZ4_resetStream_fast()
. A sameLZ4_stream_t
can be re-used multiple times consecutively and compress multiple streams, provided that it starts each new stream withLZ4_resetStream_fast()
.LZ4_resetStream_fast()
is much faster thanLZ4_initStream()
, but is not compatible with memory regions containing garbage data.Note: it's only useful to call
LZ4_resetStream_fast()
in the context of streaming compression. TheextState
functions perform their own resets. InvokingLZ4_resetStream_fast()
before is redundant, and even counterproductive.- Since:
- version 1.9.0
-
nLZ4_loadDict
public static int nLZ4_loadDict(long streamPtr, long dictionary, int dictSize)
Unsafe version of:loadDict
-
LZ4_loadDict
public static int LZ4_loadDict(long streamPtr, @Nullable java.nio.ByteBuffer dictionary)
Use this function to reference a static dictionary intoLZ4_stream_t
.The dictionary must remain available during compression.
LZ4_loadDict()
triggers a reset, so any previous data will be forgotten. The same dictionary will have to be loaded on decompression side for successful decoding. Dictionarys are useful for better compression of small data (KB range). While LZ4 accepts any input as dictionary, results are generally better when using Zstandard's Dictionary Builder. Loading a size of 0 is allowed, and is the same as reset.- Returns:
- loaded dictionary size, in bytes (necessarily ≤ 64 KB)
-
nLZ4_compress_fast_continue
public static int nLZ4_compress_fast_continue(long streamPtr, long src, long dst, int srcSize, int dstCapacity, int acceleration)
Unsafe version of:compress_fast_continue
-
LZ4_compress_fast_continue
public static int LZ4_compress_fast_continue(long streamPtr, java.nio.ByteBuffer src, java.nio.ByteBuffer dst, int acceleration)
Compresssrc
content using data from previously compressed blocks, for better compression ratio.dst
buffer must be already allocated. IfdstCapacity
≥compressBound
(srcSize)
, compression is guaranteed to succeed, and runs faster.Note 1: Each invocation to
LZ4_compress_fast_continue()
generates a new block. Each block has precise boundaries. Each block must be decompressed separately, callingLZ4_decompress_*()
with relevant metadata. It's not possible to append blocks together and expect a single invocation ofLZ4_decompress_*()
to decompress them together.Note 2: The previous 64KB of source data is assumed to remain present, unmodified, at same address in memory!
Note 3: When input is structured as a double-buffer, each buffer can have any size, including < 64 KB. Make sure that buffers are separated, by at least one byte. This construction ensures that each block only depends on previous block.
Note 4: If input buffer is a ring-buffer, it can have any size, including < 64 KB.
- Returns:
- size of compressed block or 0 if there is an error (typically, cannot fit into
dst
). After an error, the stream status is undefined (invalid), it can only be reset or freed.
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nLZ4_saveDict
public static int nLZ4_saveDict(long streamPtr, long safeBuffer, int maxDictSize)
Unsafe version of:saveDict
-
LZ4_saveDict
public static int LZ4_saveDict(long streamPtr, java.nio.ByteBuffer safeBuffer)
If last 64KB data cannot be guaranteed to remain available at its current memory location, save it into a safer place (char* safeBuffer
).This is schematically equivalent to a
memcpy()
followed byloadDict
, but is much faster, becauseLZ4_saveDict()
doesn't need to rebuild tables.- Returns:
- saved dictionary size in bytes (necessarily ≤
maxDictSize
), or 0 if error
-
LZ4_createStreamDecode
public static long LZ4_createStreamDecode()
Creates a streaming decompression tracking context.A tracking context can be re-used multiple times.
-
nLZ4_freeStreamDecode
public static int nLZ4_freeStreamDecode(long LZ4_stream)
Unsafe version of:freeStreamDecode
-
LZ4_freeStreamDecode
public static int LZ4_freeStreamDecode(long LZ4_stream)
Frees a streaming decompression tracking context.
-
nLZ4_setStreamDecode
public static int nLZ4_setStreamDecode(long LZ4_streamDecode, long dictionary, int dictSize)
Unsafe version of:setStreamDecode
-
LZ4_setStreamDecode
public static boolean LZ4_setStreamDecode(long LZ4_streamDecode, java.nio.ByteBuffer dictionary)
AnLZ4_streamDecode_t
context can be allocated once and re-used multiple times. Use this function to start decompression of a new stream of blocks.A dictionary can optionally be set. Use
NULL
or size 0 for a reset order. Dictionary is presumed stable: it must remain accessible and unmodified during next decompression.- Returns:
- 1 if OK, 0 if error
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LZ4_decoderRingBufferSize
public static int LZ4_decoderRingBufferSize(int maxBlockSize)
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 respectingmaxBlockSize
condition.- Returns:
- minimum ring buffer size, or 0 if there is an error (invalid
maxBlockSize
) - Since:
- version 1.8.2
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nLZ4_decompress_safe_continue
public static int nLZ4_decompress_safe_continue(long LZ4_streamDecode, long src, long dst, int srcSize, int dstCapacity)
Unsafe version of:decompress_safe_continue
-
LZ4_decompress_safe_continue
public static int LZ4_decompress_safe_continue(long LZ4_streamDecode, java.nio.ByteBuffer src, java.nio.ByteBuffer dst)
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. Decompression functions only accept one block at a time. The last 64KB of previously decoded data must remain available and unmodified at the memory position where they were decoded. 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
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 respectingmaxBlockSize
. - 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. 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).
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
setStreamDecode
, before decompressing next block. - Decompression buffer size is at least
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nLZ4_decompress_safe_usingDict
public static int nLZ4_decompress_safe_usingDict(long src, long dst, int srcSize, int dstCapacity, long dictStart, int dictSize)
Unsafe version of:decompress_safe_usingDict
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LZ4_decompress_safe_usingDict
public static int LZ4_decompress_safe_usingDict(java.nio.ByteBuffer src, java.nio.ByteBuffer dst, java.nio.ByteBuffer dictStart)
These decoding functions work the same as a combination ofsetStreamDecode
followed byLZ4_decompress_*_continue()
. They are stand-alone, and don't need anLZ4_streamDecode_t
structure.Dictionary is presumed stable: it must remain accessible and unmodified during decompression.
Performance tip: Decompression speed can be substantially increased when
dst == dictStart + dictSize
.
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nLZ4_compress_fast_extState_fastReset
public static int nLZ4_compress_fast_extState_fastReset(long state, long src, long dst, int srcSize, int dstCapacity, int acceleration)
Unsafe version of:compress_fast_extState_fastReset
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LZ4_compress_fast_extState_fastReset
public static int LZ4_compress_fast_extState_fastReset(java.nio.ByteBuffer state, java.nio.ByteBuffer src, java.nio.ByteBuffer dst, int acceleration)
A variant ofcompress_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
resetStream_fast
for a definition of "correctly initialized"). From a high level, the difference is that this function initializes the provided state with a call to something likeresetStream_fast
whilecompress_fast_extState
starts with a call toinitStream
.
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nLZ4_attach_dictionary
public static void nLZ4_attach_dictionary(long workingStream, long dictionaryStream)
Unsafe version of:attach_dictionary
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LZ4_attach_dictionary
public static void LZ4_attach_dictionary(long workingStream, long dictionaryStream)
This is an experimental API that allows 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 workingLZ4_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
loadDict
should be expected to work.Alternatively, the provided
dictionaryStream
may beNULL
, 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.
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nLZ4_initStream
public static long nLZ4_initStream(long buffer, long size)
Unsafe version of:initStream
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LZ4_initStream
public static long LZ4_initStream(java.nio.ByteBuffer buffer)
AnLZ4_stream_t
structure must be initialized at least once. This is automatically done when invoking createStream(), but it's not when the structure is simply declared on stack (for example).Use
LZ4_initStream()
to properly initialize a newly declaredLZ4_stream_t
. It can also initialize any arbitrary buffer of sufficient size, and will return a pointer of proper type upon initialization.Note: initialization fails if size and alignment conditions are not respected. In which case, the function will
NULL
.Note 2: An
LZ4_stream_t
structure guarantees correct alignment and size.- Since:
- 1.9.0
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LZ4_DECOMPRESS_INPLACE_MARGIN
public static int LZ4_DECOMPRESS_INPLACE_MARGIN(int compressedSize)
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LZ4_DECOMPRESS_INPLACE_BUFFER_SIZE
public static int LZ4_DECOMPRESS_INPLACE_BUFFER_SIZE(int decompressedSize)
Note: presumes thatcompressedSize
<decompressedSize
.Note 2: margin is overestimated a bit, since it could use
compressedSize instead
.
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LZ4_COMPRESS_INPLACE_MARGIN
public static int LZ4_COMPRESS_INPLACE_MARGIN()
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LZ4_COMPRESS_INPLACE_BUFFER_SIZE
public static int LZ4_COMPRESS_INPLACE_BUFFER_SIZE(int maxCompressedSize)
- Parameters:
maxCompressedSize
- is generallyCOMPRESSBOUND
(inputSize)
, but can be set to any lower value, with the risk that compression can fail (return code 0)
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LZ4_DECODER_RING_BUFFER_SIZE
public static int LZ4_DECODER_RING_BUFFER_SIZE(int maxBlockSize)
For static allocation;maxBlockSize
presumed valid.
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