Package it.unimi.dsi.big.webgraph

Class MaskedLongIterator

java.lang.Object

it.unimi.dsi.big.webgraph.MaskedLongIterator

All Implemented Interfaces:

LazyLongIterator

public class MaskedLongIterator
extends Object
implements LazyLongIterator

An iterator returning the element of an underlying iterator but filters them using a inclusion-exclusion block list.

A mask is an array of integers. The sum of the values contained in the mask must not exceed the number of elements returned by the underlying iterator. Moreover, all integers in the mask must be positive, except possibly for the first one, which may be zero.

Mask values are interpreted as specifying inclusion-exclusion blocks. Suppose that the underlying iterator returns N values, and that the mask is n₀, n₁, …, n_k. Then, the first n₀ values returned by the underlying iterator must be kept, the next n₁ values must be ignored, the next n₂ must be kept and so on. The last N−(n₀+…+n_k) must be kept if k is odd, and must be ignored otherwise. An instance of this class will returns the kept values only, in increasing order.

Constructor Summary

Constructors

Constructor	Description
MaskedLongIterator(long[] mask, int maskLen, LazyLongIterator underlying)	Creates a new masked iterator using a given mask, mask length and underlying iterator.
MaskedLongIterator(long[] mask, LazyLongIterator underlying)	Creates a new masked iterator using a given mask and underlying iterator.

Method Summary

Modifier and Type	Method	Description
long	nextLong()	The next long returned by this iterator, or the special marker if this iterator is exhausted.
long	skip(long n)	Skips a given number of elements.

Methods inherited from class java.lang.Object

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

Constructor Details

MaskedLongIterator

public MaskedLongIterator(long[] mask,
 LazyLongIterator underlying)

Creates a new masked iterator using a given mask and underlying iterator.

Parameters:

mask - a mask, or null, meaning an empty mask (everything is copied).

underlying - an underlying iterator.

MaskedLongIterator

public MaskedLongIterator(long[] mask,
 int maskLen,
 LazyLongIterator underlying)

Creates a new masked iterator using a given mask, mask length and underlying iterator.

Parameters:

mask - a mask, or null, meaning an empty mask (everything is copied).

maskLen - an explicit mask length.

underlying - an underlying iterator.

Method Details

nextLong

public long nextLong()

Description copied from interface: LazyLongIterator

The next long returned by this iterator, or the special marker if this iterator is exhausted.

Specified by:

nextLong in interface LazyLongIterator

Returns:

next long returned by this iterator, or the special marker if this iterator is exhausted.

skip

public long skip(long n)

Description copied from interface: LazyLongIterator

Skips a given number of elements.

Specified by:

skip in interface LazyLongIterator

Parameters:

n - the number of elements to skip.

Returns:

the number of elements actually skipped (which might be less than n if this iterator is exhausted).