org.apache.commons.compress.compressors.lz77support

Class Parameters.Builder

java.lang.Object

org.apache.commons.compress.compressors.lz77support.Parameters.Builder

Enclosing class:

Parameters

public static class Parameters.Builder
extends Object

Builder for Parameters instances.

Method Summary

Modifier and Type	Method and Description
Parameters	build() Creates the Parameters instance.
Parameters.Builder	tunedForCompressionRatio() Changes the default setting for "nice back-reference length" and "maximum number of candidates" for improved compression ratio at the cost of compression speed.
Parameters.Builder	tunedForSpeed() Changes the default setting for "nice back-reference length" and "maximum number of candidates" for improved compression speed at the cost of compression ratio.
Parameters.Builder	withLazyMatching(boolean lazy) Sets whether lazy matching should be performed.
Parameters.Builder	withLazyThreshold(int threshold) Sets the threshold for lazy matching.
Parameters.Builder	withMaxBackReferenceLength(int maxBackReferenceLength) Sets the maximal length of a back-reference.
Parameters.Builder	withMaxLiteralLength(int maxLiteralLength) Sets the maximal length of a literal block.
Parameters.Builder	withMaxNumberOfCandidates(int maxCandidates) Sets the maximum number of back-reference candidates that should be consulted.
Parameters.Builder	withMaxOffset(int maxOffset) Sets the maximal offset of a back-reference.
Parameters.Builder	withMinBackReferenceLength(int minBackReferenceLength) Sets the mininal length of a back-reference.
Parameters.Builder	withNiceBackReferenceLength(int niceLen) Sets the "nice length" of a back-reference.

Methods inherited from class java.lang.Object

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

Method Detail

withMinBackReferenceLength

public Parameters.Builder withMinBackReferenceLength(int minBackReferenceLength)

Sets the mininal length of a back-reference.

Ensures maxBackReferenceLength is not smaller than minBackReferenceLength.

It is recommended to not use this method directly but rather tune a pre-configured builder created by a format specific factory like SnappyCompressorOutputStream.createParameterBuilder(int).

Parameters:

minBackReferenceLength - the minimal length of a back-reference found. A true minimum of 3 is hard-coded inside of this implemention but bigger lengths can be configured.

Returns:

the builder

Throws:

IllegalArgumentException - if windowSize is smaller than minBackReferenceLength.

withMaxBackReferenceLength

public Parameters.Builder withMaxBackReferenceLength(int maxBackReferenceLength)

Sets the maximal length of a back-reference.

It is recommended to not use this method directly but rather tune a pre-configured builder created by a format specific factory like SnappyCompressorOutputStream.createParameterBuilder(int).

Parameters:

maxBackReferenceLength - maximal length of a back-reference found. A value smaller than minBackReferenceLength is interpreted as minBackReferenceLength. maxBackReferenceLength is capped at windowSize - 1.

Returns:

the builder

withMaxOffset

public Parameters.Builder withMaxOffset(int maxOffset)

Sets the maximal offset of a back-reference.

It is recommended to not use this method directly but rather tune a pre-configured builder created by a format specific factory like SnappyCompressorOutputStream.createParameterBuilder(int).

Parameters:

maxOffset - maximal offset of a back-reference. A non-positive value as well as values bigger than windowSize - 1 are interpreted as windowSize - 1.

Returns:

the builder

withMaxLiteralLength

public Parameters.Builder withMaxLiteralLength(int maxLiteralLength)

Sets the maximal length of a literal block.

It is recommended to not use this method directly but rather tune a pre-configured builder created by a format specific factory like SnappyCompressorOutputStream.createParameterBuilder(int).

Parameters:

maxLiteralLength - maximal length of a literal block. Negative numbers and 0 as well as values bigger than windowSize are interpreted as windowSize.

Returns:

the builder

withNiceBackReferenceLength

public Parameters.Builder withNiceBackReferenceLength(int niceLen)

Sets the "nice length" of a back-reference.

When a back-references if this size has been found, stop searching for longer back-references.

This settings can be used to tune the tradeoff between compression speed and compression ratio.

Parameters:

niceLen - the "nice length" of a back-reference

Returns:

the builder

withMaxNumberOfCandidates

public Parameters.Builder withMaxNumberOfCandidates(int maxCandidates)

Sets the maximum number of back-reference candidates that should be consulted.

This settings can be used to tune the tradeoff between compression speed and compression ratio.

Parameters:

maxCandidates - maximum number of back-reference candidates

Returns:

the builder

withLazyMatching

public Parameters.Builder withLazyMatching(boolean lazy)

Sets whether lazy matching should be performed.

Lazy matching means that after a back-reference for a certain position has been found the compressor will try to find a longer match for the next position.

Lazy matching is enabled by default and disabled when tuning for speed.

Parameters:

lazy - whether lazy matching should be performed

Returns:

the builder

withLazyThreshold

public Parameters.Builder withLazyThreshold(int threshold)

Sets the threshold for lazy matching.

Even if lazy matching is enabled it will not be performed if the length of the back-reference found for the current position is longer than this value.

Parameters:

threshold - the threshold for lazy matching

Returns:

the builder

tunedForSpeed

public Parameters.Builder tunedForSpeed()

Changes the default setting for "nice back-reference length" and "maximum number of candidates" for improved compression speed at the cost of compression ratio.

Use this method after configuring "maximum back-reference length".

Returns:

the builder

tunedForCompressionRatio

public Parameters.Builder tunedForCompressionRatio()

Changes the default setting for "nice back-reference length" and "maximum number of candidates" for improved compression ratio at the cost of compression speed.

Use this method after configuring "maximum back-reference length".

Returns:

the builder

build

public Parameters build()

Creates the Parameters instance.

Returns:

the configured Parameters instance.