Package edu.berkeley.cs.jqf.fuzz.guidance

Class StreamBackedRandom

java.lang.Object

java.util.Random

edu.berkeley.cs.jqf.fuzz.guidance.StreamBackedRandom

All Implemented Interfaces:

Serializable

public class StreamBackedRandom
extends Random

This class extends Random to act as a generator of "random" values, which themselves are read from a static file. The file-backed random number generator can be used for tuning the "random" choices made by various junit-quickcheck generators using a mutation-based genetic algorithm, in order to maximize some objective function that can be measured from the execution of each trial, such as code coverage.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor	Description
StreamBackedRandom(InputStream source)	Constructs a stream-backed random generator.
StreamBackedRandom(InputStream source, int leadinBytesToIgnore)	Convenience constructor for use with the junit-quickcheck framework.

Method Summary

Modifier and Type	Method	Description
int	getTotalBytesRead()
int	next(int bits)	Generates upto 32 bits of random data for internal use by the Random class.
byte	nextByte()
int	nextInt(int bound)
short	nextShort()

Methods inherited from class java.util.Random

doubles, doubles, doubles, doubles, ints, ints, ints, ints, longs, longs, longs, longs, nextBoolean, nextBytes, nextDouble, nextFloat, nextGaussian, nextInt, nextLong, setSeed

Methods inherited from class java.lang.Object

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

Constructor Detail

StreamBackedRandom

public StreamBackedRandom(InputStream source)

Constructs a stream-backed random generator. Also sets the seed of the underlying pseudo-random number generator deterministically to zero.

Parameters:

source - a generator of "random" bytes

StreamBackedRandom

public StreamBackedRandom(InputStream source,
                          int leadinBytesToIgnore)

Convenience constructor for use with the junit-quickcheck framework. The junit-quickcheck SourceOfRandomness annoyingly reads 8 bytes of random data as soon as it is instantiated, only to configure its own seed. As the seed is meaningless here, the 8 bytes get wasted. For this purpose, this constructor allows specifying how many bytes of requested random data to skip before starting to read from file.

Parameters:

source - a generator of "random" bytes

leadinBytesToIgnore - the number of leading bytes to ignore

Method Detail

next

public int next(int bits)

Generates upto 32 bits of random data for internal use by the Random class.

Attempts to read up to 4 bytes of data from the input file, and returns the requested lower order bits as a pseudo-random value.

If end-of-file is reached before reading 4 bytes, an IllegalStateException is thrown.

Overrides:

next in class Random

Parameters:

bits - the number of random bits to retain (1 to 32 inclusive)

Returns:

the integer value whose lower bits bits contain the next random data available in the backing source

Throws:

IllegalStateException - if EOF has already been reached

nextInt

public int nextInt(int bound)

Overrides:

nextInt in class Random

nextByte

public byte nextByte()

nextShort

public short nextShort()

getTotalBytesRead

public int getTotalBytesRead()