public Class LZ4

History window size; can be user-defined at compile time.

Maximum input size.

Memory usage formula : N->2^N Bytes (examples : 10 -> 1KB; 12 -> 4KB ; 16 -> 64KB; 20 -> 1MB; )

Increasing memory usage improves compression ratio, at the cost of speed. Reduced memory usage may improve speed at the cost of ratio, thanks to better cache locality.

Default value is 14, for 16KB, which nicely fits into Intel x86 L1 cache.

Tuning parameters.

Tuning parameters.

Tuning parameters.

Version number part.

Version number part.

Version number.

Version number part.

Version string.

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 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 loadDict should be expected to work.

Alternatively, the provided dictionaryStream 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.

Compresses srcSize bytes from buffer src into already allocated dst buffer of size dstCapacity.

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 limited dst 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 outside src buffer).

Returns:int

the number of bytes written into buffer dest (necessarily ≤ maxOutputSize) or 0 if compression fails

Reverse the logic: compresses as much data as possible from src buffer into already allocated buffer dst of size targetDstSize.

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.

Parameters

srcSizePtr:IntBuffer

will be modified to indicate how many bytes where read from source to fill dest. New value is necessarily ≤ input value.

Returns:int

nb bytes written into dest (necessarily ≤ targetDestSize) or 0 if compression fails

Same as compress_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 by LZ4_ACCELERATION_DEFAULT (currently == 1, see lz4.c). Values > LZ4_ACCELERATION_MAX will be replaced by LZ4_ACCELERATION_MAX (currently == 65537, see lz4.c).

Compress src content using data from previously compressed blocks, for better compression ratio.

dst buffer must be already allocated. If dstCapacity ≥ 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, calling LZ4_decompress_*() with relevant metadata. It's not possible to append blocks together and expect a single invocation of LZ4_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:int

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.

Same as compress_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 (using malloc() typically). Then, provide it as void* state to compression function.

A variant of 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 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 like resetStream_fast while compress_fast_extState starts with a call to initStream.

Parameters

maxCompressedSize:int

is generally COMPRESSBOUND(inputSize), but can be set to any lower value, with the risk that compression can fail (return code 0)

See compressBound.

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 when dstCapacity is ≥ compressBound(srcSize)

Parameters

inputSize:int

max supported value is MAX_INPUT_SIZE

Returns:int

maximum output size in a "worst case" scenario or 0, if input size is incorrect (too large or negative)

Allocates and initializes an LZ4_stream_t structure.

Annotations

@NativeType:LZ4_stream_t *

Creates a streaming decompression tracking context.

A tracking context can be re-used multiple times.

Annotations

@NativeType:LZ4_streamDecode_t *

For static allocation; maxBlockSize presumed valid.

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.

Returns:int

minimum ring buffer size, or 0 if there is an error (invalid maxBlockSize)

Since

version 1.8.2

Note 2: margin is overestimated a bit, since it could use compressedSize instead.

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 outside source 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 and dstCapacity 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 at lz4frame.h instead.

Returns:int

the number of bytes decompressed into destination buffer (necessarily ≤ dstCapacity)

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 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. 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.

Decompresses an LZ4 compressed block, of size srcSize at position src, into destination buffer dst of size dstCapacity.

Up to targetOutputSize bytes will be decoded. The function stops decoding on reaching this objective. This can be useful to boost performance whenever only the beginning of a block is required.

Notes:

1. result can be < targetOutputSize, if compressed block contains less data.
2. targetOutputSize must be ≤ dstCapacity
3. this function effectively stops decoding on reaching targetOutputSize, so dstCapacity is kind of redundant. This is because in older versions of this function, decoding operation would still write complete sequences. Therefore, there was no guarantee that it would stop writing at exactly targetOutputSize, it could write more bytes, though only up to dstCapacity. Some "margin" used to be required for this operation to work properly. Thankfully, this is no longer necessary. The function nonetheless keeps the same signature, in an effort to preserve API compatibility.
4. if srcSize is the exact size of the block, then targetOutputSize can be any value, including larger than the block's decompressed size. The function will, at most, generate block's decompressed size.
5. if srcSize is larger than block's compressed size, then targetOutputSize MUST be ≤ block's decompressed size. Otherwise, silent corruption will occur.

Returns:int

the number of bytes decoded in dst (necessarily ≤ targetOutputSize). If source stream is detected malformed, function returns a negative result.

See decompress_safe_usingDict.

These decoding functions work the same as a combination of setStreamDecode followed by LZ4_decompress_*_continue(). They are stand-alone, and don't need an LZ4_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.

Releases memory of an LZ4_stream_t structure.

Frees a streaming decompression tracking context.

An LZ4_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 declared LZ4_stream_t. It can also initialize any arbitrary buffer of sufficient size, and will return a pointer of proper type upon initialization.

Note 2: An LZ4_stream_t structure guarantees correct alignment and size.

Annotations

@NativeType:LZ4_stream_t *

Since

1.9.0

Use this function to reference a static dictionary into LZ4_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:int

loaded dictionary size, in bytes (necessarily ≤ 64 KB)

Use this to prepare an LZ4_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 by createStream. However, should the LZ4_stream_t be simply declared on stack (for example), it's necessary to initialize it first, using initStream.

After init, start any new stream with LZ4_resetStream_fast(). A same LZ4_stream_t can be re-used multiple times consecutively and compress multiple streams, provided that it starts each new stream with LZ4_resetStream_fast().

LZ4_resetStream_fast() is much faster than LZ4_initStream(), but is not compatible with memory regions containing garbage data.

Since

version 1.9.0

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 by loadDict, but is much faster, because LZ4_saveDict() doesn't need to rebuild tables.

Returns:int

saved dictionary size in bytes (necessarily ≤ maxDictSize), or 0 if error

An LZ4_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:boolean

1 if OK, 0 if error

Annotations

@NativeType:int

Returns the version number.

Returns the version string.

Annotations

@NativeType:char const *

Unsafe version of: attach_dictionary

Unsafe version of: compress_default

Parameters

srcSize:int

max supported value is MAX_INPUT_SIZE

dstCapacity:int

size of buffer dst (which must be already allocated)

Unsafe version of: compress_destSize

Parameters

srcSizePtr:long

will be modified to indicate how many bytes where read from source to fill dest. New value is necessarily ≤ input value.

Unsafe version of: compress_fast

Unsafe version of: compress_fast_continue

Unsafe version of: compress_fast_extState

Unsafe version of: compress_fast_extState_fastReset

Unsafe version of: decompress_safe

Parameters

compressedSize:int

is the exact complete size of the compressed block

dstCapacity:int

is the size of destination buffer (which must be already allocated), presumed an upper bound of decompressed size

Unsafe version of: decompress_safe_continue

Unsafe version of: decompress_safe_partial

Unsafe version of: decompress_safe_partial_usingDict

Unsafe version of: decompress_safe_usingDict

Unsafe version of: freeStream

Unsafe version of: freeStreamDecode

Unsafe version of: initStream

Unsafe version of: loadDict

Unsafe version of: resetStream_fast

Unsafe version of: saveDict

Unsafe version of: setStreamDecode

Unsafe version of: versionString