it.unimi.dsi.big.util
Class SemiExternalGammaBigList

java.lang.Object
  extended by java.util.AbstractCollection<Long>
      extended by it.unimi.dsi.fastutil.longs.AbstractLongCollection
          extended by it.unimi.dsi.fastutil.longs.AbstractLongBigList
              extended by it.unimi.dsi.big.util.SemiExternalGammaBigList
All Implemented Interfaces:
BigList<Long>, LongBigList, LongCollection, LongIterable, LongStack, Size64, Stack<Long>, Comparable<BigList<? extends Long>>, Iterable<Long>, Collection<Long>

public class SemiExternalGammaBigList
extends AbstractLongBigList

Provides semi-external random access to a big list of γ-encoded integers.

This class is a semi-external LongBigList that MG4J uses to access files containing frequencies.

Instead, this class accesses frequencies in their compressed forms, and provides entry points for random access to each long. At construction time, entry points are computed with a certain step, which is the number of longs accessible from each entry point, or, equivalently, the maximum number of longs that will be necessary to read to access a given long.

Warning: This class is not thread safe, and needs to be synchronised to be used in a multithreaded environment.

Since:
2.0
Author:
Fabien Campagne, Sebastiano Vigna

Nested Class Summary
 
Nested classes/interfaces inherited from class it.unimi.dsi.fastutil.longs.AbstractLongBigList
AbstractLongBigList.LongSubList
 
Field Summary
static int DEFAULT_STEP
           
 
Constructor Summary
SemiExternalGammaBigList(InputBitStream longs)
          Creates a new semi-external list.
SemiExternalGammaBigList(InputBitStream longs, int step, long numLongs)
          Creates a new semi-external list.
 
Method Summary
 long getLong(long index)
           
 long size64()
           
 
Methods inherited from class it.unimi.dsi.fastutil.longs.AbstractLongBigList
add, add, add, addAll, addAll, addAll, addAll, addAll, addAll, addAll, addElements, addElements, compareTo, contains, ensureIndex, ensureRestrictedIndex, equals, get, getElements, getLong, hashCode, indexOf, indexOf, iterator, lastIndexOf, lastIndexOf, listIterator, listIterator, listIterator, peek, peekLong, pop, popLong, push, push, rem, remove, remove, removeElements, removeLong, removeLong, set, set, set, size, size, size, subList, top, topLong, toString
 
Methods inherited from class it.unimi.dsi.fastutil.longs.AbstractLongCollection
add, contains, containsAll, containsAll, isEmpty, longIterator, rem, remove, removeAll, removeAll, retainAll, retainAll, toArray, toArray, toArray, toLongArray, toLongArray
 
Methods inherited from class java.util.AbstractCollection
clear
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
 
Methods inherited from interface it.unimi.dsi.fastutil.longs.LongCollection
containsAll, longIterator, removeAll, retainAll, toArray, toArray, toLongArray, toLongArray
 
Methods inherited from interface java.util.Collection
add, clear, contains, containsAll, isEmpty, remove, removeAll, retainAll, toArray
 
Methods inherited from interface it.unimi.dsi.fastutil.Stack
isEmpty
 

Field Detail

DEFAULT_STEP

public static final int DEFAULT_STEP
See Also:
Constant Field Values
Constructor Detail

SemiExternalGammaBigList

public SemiExternalGammaBigList(InputBitStream longs,
                                int step,
                                long numLongs)
                         throws IOException
Creates a new semi-external list.

Parameters:
longs - a bit stream containing γ-encoded longs.
step - the step used to build random-access entry points, or -1 to get DEFAULT_STEP; note that a step causing more than 231 slots will be silently increased.
numLongs - the overall number of offsets (i.e., the number of terms).
Throws:
IOException

SemiExternalGammaBigList

public SemiExternalGammaBigList(InputBitStream longs)
                         throws IOException
Creates a new semi-external list.

This quick-and-dirty constructor estimates the number of longs by checking for an EOFException.

Parameters:
longs - a bit stream containing γ-encoded longs.
Throws:
IOException
Method Detail

getLong

public final long getLong(long index)

size64

public long size64()