it.unimi.dsi.util

Class PermutedFrontCodedStringList

java.lang.Object

java.util.AbstractCollection<K>

it.unimi.dsi.fastutil.objects.AbstractObjectCollection<K>

it.unimi.dsi.fastutil.objects.AbstractObjectList<CharSequence>

it.unimi.dsi.util.PermutedFrontCodedStringList

All Implemented Interfaces:

ObjectCollection<CharSequence>, ObjectIterable<CharSequence>, ObjectList<CharSequence>, Stack<CharSequence>, Serializable, Comparable<List<? extends CharSequence>>, Iterable<CharSequence>, Collection<CharSequence>, List<CharSequence>

public class PermutedFrontCodedStringList
extends AbstractObjectList<CharSequence>
implements Serializable

A FrontCodedStringList whose indices are permuted.

It may happen that a list of strings compresses very well using front coding, but unfortunately alphabetical order is not the right order for the strings in the list. Instances of this class wrap an instance of FrontCodedStringList together with a permutation π: inquiries with index i will actually return the string with index π_i.

In case you start from a newline-delimited non-sorted list of UTF-8 strings, the simplest way to build an instance of this map is obtaining a front-coded string list and a permutation with a simple UN*X pipe (which also avoids storing the sorted strings):

 nl -v0 -nln | sort -k2 | tee >(cut -f1 >perm.txt) \ 
        | cut -f2 | java it.unimi.dsi.util.FrontCodedStringList tmp-lex.fcl
 

The above command will read a list of strings from standard input, output a their sorted index list in perm.txt and create a tmp-lex.fcl front-coded string list containing the sorted list of strings.

Important: you must be sure to be using the byte-by-byte collation order—in UN*X, be sure that LC_COLLATE=C. Failure to do so will result in an order-of-magnitude-slower sorting and worse compression.

Now, in perm.txt you will find the permutation that you have to pass to this class (given that you will use the option -i). So the last step is just

 java it.unimi.dsi.util.PermutedFrontCodedStringList -i -t tmp-lex.fcl perm.txt your.fcl
 

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class it.unimi.dsi.fastutil.objects.AbstractObjectList

AbstractObjectList.ObjectSubList<K>

Field Summary

Fields

Modifier and Type	Field and Description
protected FrontCodedStringList	frontCodedStringList The underlying front-coded string list.
protected int[]	permutation The permutation.
static long	serialVersionUID

Constructor Summary

Constructors

Constructor and Description
PermutedFrontCodedStringList(FrontCodedStringList frontCodedStringList, int[] permutation) Creates a new permuted front-coded string list using a given front-coded string list and permutation.

Method Summary

Modifier and Type	Method and Description
CharSequence	get(int index)
void	get(int index, MutableString s) Returns the element at the specified position in this front-coded list by storing it in a mutable string.
ObjectListIterator<CharSequence>	listIterator(int k)
static void	main(String[] arg)
int	size()

Methods inherited from class it.unimi.dsi.fastutil.objects.AbstractObjectList

add, add, addAll, addAll, addElements, addElements, compareTo, contains, ensureIndex, ensureRestrictedIndex, equals, getElements, hashCode, indexOf, iterator, lastIndexOf, listIterator, objectListIterator, objectListIterator, objectSubList, peek, pop, push, remove, removeElements, set, size, subList, top, toString

Methods inherited from class it.unimi.dsi.fastutil.objects.AbstractObjectCollection

containsAll, isEmpty, objectIterator, removeAll, retainAll, toArray, toArray

Methods inherited from class java.util.AbstractCollection

clear, remove

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.List

clear, containsAll, isEmpty, remove, removeAll, replaceAll, retainAll, sort, spliterator, toArray, toArray

Methods inherited from interface it.unimi.dsi.fastutil.objects.ObjectCollection

objectIterator, toArray

Methods inherited from interface java.util.Collection

parallelStream, removeIf, stream

Methods inherited from interface java.lang.Iterable

forEach

Methods inherited from interface it.unimi.dsi.fastutil.Stack

isEmpty

Field Detail

serialVersionUID

public static final long serialVersionUID

See Also:

Constant Field Values

frontCodedStringList

protected final FrontCodedStringList frontCodedStringList

The underlying front-coded string list.

permutation

protected final int[] permutation

The permutation.

Constructor Detail

PermutedFrontCodedStringList

public PermutedFrontCodedStringList(FrontCodedStringList frontCodedStringList,
                                    int[] permutation)

Creates a new permuted front-coded string list using a given front-coded string list and permutation.

Parameters:

frontCodedStringList - the underlying front-coded string list.

permutation - the underlying permutation.

Method Detail

get

public CharSequence get(int index)

Specified by:

get in interface List<CharSequence>

get

public void get(int index,
                MutableString s)

Returns the element at the specified position in this front-coded list by storing it in a mutable string.

Parameters:

index - an index in the list.

s - a mutable string that will contain the string at the specified position.

size

public int size()

Specified by:

size in interface Collection<CharSequence>

Specified by:

size in interface List<CharSequence>

Specified by:

size in class AbstractCollection<CharSequence>

listIterator

public ObjectListIterator<CharSequence> listIterator(int k)

Specified by:

listIterator in interface ObjectList<CharSequence>

Specified by:

listIterator in interface List<CharSequence>

Overrides:

listIterator in class AbstractObjectList<CharSequence>

main

public static void main(String[] arg)
                 throws IOException,
                        ClassNotFoundException,
                        JSAPException

Throws:

IOException

ClassNotFoundException

JSAPException