Module org.elasticsearch.nativeaccess

Package org.elasticsearch.nativeaccess

Class Zstd.DStream

java.lang.Object

org.elasticsearch.nativeaccess.Zstd.DStream

All Implemented Interfaces:

AutoCloseable

Enclosing class:

Zstd

public final class Zstd.DStream
extends Object
implements AutoCloseable

Streaming-mode zstd decompression resource. Backs PanamaZstdInputStream and any other consumer that needs incremental ZSTD_decompressStream semantics: refill an input chunk, call decompress(byte[], int, int, byte[], int, int), read lastSrcPos() / lastDstPos() to advance cursors, loop while the hint return is positive (more input wanted), and observe a zero return when the current frame finished.

Bounds are validated Java-side; error returns from libzstd are translated to IllegalArgumentException carrying the ZSTD_getErrorName string. All hot-path state (the two ZSTD_inBuffer/ZSTD_outBuffer struct holders, the native context handle) lives inside the binding — every decompress(byte[], int, int, byte[], int, int) call is allocation-free.

Not thread-safe.

Method Summary

Modifier and Type	Method	Description
void	close()	Idempotent — frees the native ZSTD_DStream and the cached struct holders.
long	decompress(byte[] dst, int dstPos, int dstLen, byte[] src, int srcPos, int srcLen)	Feed src[srcPos..srcLen) into the decoder and write decompressed bytes into dst[dstPos..dstLen).
int	lastDstPos()	Output position after the most recent decompress(byte[], int, int, byte[], int, int) — an absolute index into the dst array that was passed to that call.
int	lastSrcPos()	Input position after the most recent decompress(byte[], int, int, byte[], int, int) — an absolute index into the src array that was passed to that call.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Details

decompress

public long decompress(byte[] dst,
 int dstPos,
 int dstLen,
 byte[] src,
 int srcPos,
 int srcLen)

Feed src[srcPos..srcLen) into the decoder and write decompressed bytes into dst[dstPos..dstLen). Returns the libzstd hint: 0 means the current frame finished decoding (the decoder is implicitly reset for the next concatenated frame, if any), a positive return is libzstd's best guess for the amount of additional input it would like to see next, and a zstd-side error is translated to IllegalArgumentException.

After return, the caller reads lastSrcPos() / lastDstPos() to learn how far the input/output cursors advanced — these are absolute offsets within the supplied arrays, not deltas.

Chunking contract. Callers must pass at most Zstd.dStreamInSize() bytes of input per call (srcLen - srcPos <= dStreamInSize()). Larger slices raise IllegalArgumentException from the binding — the binding hard-fails rather than silently consuming a prefix because partial consumption is easy to overlook at call sites. PanamaZstdInputStream caches the recommended size in a static final and refills upstream in chunks of that size. Output may be any size; the binding internally caps each call at Zstd.dStreamOutSize() and the caller's outer loop drives subsequent calls as needed.

lastDstPos

public int lastDstPos()

Output position after the most recent decompress(byte[], int, int, byte[], int, int) — an absolute index into the dst array that was passed to that call.

lastSrcPos

public int lastSrcPos()

Input position after the most recent decompress(byte[], int, int, byte[], int, int) — an absolute index into the src array that was passed to that call.

close

public void close()

Idempotent — frees the native ZSTD_DStream and the cached struct holders.

Specified by:

close in interface AutoCloseable