it.unimi.dsi.mg4j.util
Class FrontCodedStringList

java.lang.Object
  it.unimi.dsi.fastutil.objects.AbstractObjectCollection
      it.unimi.dsi.fastutil.objects.AbstractObjectList
          it.unimi.dsi.mg4j.util.FrontCodedStringList

All Implemented Interfaces:

Collection, Comparable, List, ObjectCollection, ObjectList, Serializable, Stack

public class FrontCodedStringList

extends AbstractObjectList

implements Serializable

Compact storage of strings using front-coding compression.

This class stores a list of strings using front-coding compression (of course, the compression will be reasonable only if the list is sorted, but you could also use instances of this class just as a handy way to manage a large amount of strings). It implements an immutable ObjectList that returns the i-th string (as a MutableString) when the get(int) method is called with argument i. The returned mutable string may be freely modified.

As a commodity, this class provides a main method that reads from standard input a sequence of newline-separated words, and writes a corresponding serialized front-coded string list.

Implementation Details

To store the list of strings, we use either a UTF-8 coded ByteArrayFrontCodedList, or a CharArrayFrontCodedList, depending on the value of the utf8 parameter at creation time. In the first case, if the strings are ASCII-oriented the resulting array will be much smaller, but access times will increase manifold, as each string must be UTF-8 encoded before being returned.

See Also:

Serialized Form

Field Summary

protected ByteArrayFrontCodedList	byteFrontCodedList The underlying ByteArrayFrontCodedList, or null.
protected CharArrayFrontCodedList	charFrontCodedList The underlying CharArrayFrontCodedList, or null.
protected ObjectList	frontCodedList The underlying front-coded list (either a ByteArrayFrontCodedList, or a CharArrayFrontCodedList, depending on the value of utf8).
static long	serialVersionUID
protected boolean	utf8 Whether this front-coded list is UTF-8 encoded.

Constructor Summary

FrontCodedStringList(Collection c, int ratio, boolean utf8)
Creates a new front-coded string list containing the character sequences contained in the given collection.

FrontCodedStringList(Iterator words, int ratio, boolean utf8)
Creates a new front-coded string list containing the character sequences returned by the given iterator.

Method Summary

Object	get(int index) Returns the element at the specified position in this front-coded as a mutable string.
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.
static void	main(String[] arg)
ObjectListIterator	objectListIterator(int k)
int	ratio() Returns the ratio of the underlying front-coded list.
int	size()
boolean	utf8() Returns whether this front-coded string list is storing its strings as UTF-8 encoded bytes.

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

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

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

add, clear, containsAll, isEmpty, iterator, remove, removeAll, retainAll, toArray, toArray

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.List

add, clear, containsAll, isEmpty, iterator, remove, removeAll, retainAll, toArray, toArray

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

isEmpty

Field Detail

serialVersionUID

public static final long serialVersionUID

See Also:

Constant Field Values

frontCodedList

protected ObjectList frontCodedList

The underlying front-coded list (either a ByteArrayFrontCodedList, or a CharArrayFrontCodedList, depending on the value of utf8).

byteFrontCodedList

protected transient ByteArrayFrontCodedList byteFrontCodedList

The underlying ByteArrayFrontCodedList, or null.

charFrontCodedList

protected transient CharArrayFrontCodedList charFrontCodedList

The underlying CharArrayFrontCodedList, or null.

utf8

protected boolean utf8

Whether this front-coded list is UTF-8 encoded.

Constructor Detail

FrontCodedStringList

public FrontCodedStringList(Iterator words,
                            int ratio,
                            boolean utf8)

Creates a new front-coded string list containing the character sequences returned by the given iterator.

Parameters:

words - an iterator returning character sequences.

ratio - the desired ratio.

utf8 - if true, the strings will be stored as UTF-8 byte arrays.

FrontCodedStringList

public FrontCodedStringList(Collection c,
                            int ratio,
                            boolean utf8)

Creates a new front-coded string list containing the character sequences contained in the given collection.

Parameters:

c - a collection containing character sequences.

ratio - the desired ratio.

utf8 - if true, the strings will be stored as UTF-8 byte arrays.

Method Detail

utf8

public boolean utf8()

Returns whether this front-coded string list is storing its strings as UTF-8 encoded bytes.

Returns:

true if this front-coded string list is keeping its data as an array of UTF-8 encoded bytes.

ratio

public int ratio()

Returns the ratio of the underlying front-coded list.

Returns:

the ratio of the underlying front-coded list.

get

public Object get(int index)

Returns the element at the specified position in this front-coded as a mutable string.

Specified by:

get in interface List

Parameters:

index - an index in the list.

Returns:

a MutableString that will contain the string at the specified position. The string may be freely modified.

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.

objectListIterator

public ObjectListIterator objectListIterator(int k)

Specified by:

objectListIterator in interface ObjectList

size

public int size()

Specified by:

size in interface List

main

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

Throws:

FileNotFoundException

IOException