Eclipse Plug-in Developer Guide (Galileo) - GapTextStore (Eclipse Platform API Specification)

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Eclipse Platform
Release 3.5

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org.eclipse.jface.text
Class GapTextStore


java.lang.Object
  
org.eclipse.jface.text.GapTextStore

All Implemented Interfaces:: ITextStore

public class GapTextStore
extends Object
implements ITextStore
extends Object
implements ITextStore

Implements a gap managing text store. The gap text store relies on the assumption that consecutive changes to a document are co-located. The start of the gap is always moved to the location of the last change.

Performance: Typing-style changes perform in constant time unless re-allocation becomes necessary. Generally, a change that does not cause re-allocation will cause at most one arraycopy operation of a length of about d, where d is the distance from the previous change. Let a(x) be the algorithmic performance of an arraycopy operation of the length x, then such a change then performs in O(a(x)), get(int, length) performs in O(a(length)), get(int) in O(1).

How frequently the array needs re-allocation is controlled by the constructor parameters.

This class is not intended to be subclassed.

See Also:: for a copy-on-write text store wrapper
Restriction:: This class is not intended to be subclassed by clients.

Constructor Summary

GapTextStore ()
          Equivalent to new GapTextStore(256, 4096, 0.1f).

GapTextStore (int lowWatermark, int highWatermark)
          Deprecated. use GapTextStore(int, int, float) instead

GapTextStore (int minSize, int maxSize, float maxGapFactor)
          Creates an empty text store that uses re-allocation thresholds relative to the content length.

Method Summary

char get (int offset)
          Returns the character at the specified offset.

String get (int offset, int length)
          Returns the text of the specified character range.

protected String getContentAsString ()
          Returns a copy of the content of this text store.

protected int getGapEndIndex ()
          Returns the end index of the gap managed by this text store.

protected int getGapStartIndex ()
          Returns the start index of the gap managed by this text store.

int getLength ()
          Returns number of characters stored in this text store.

void replace (int offset, int length, String text)
          Replaces the specified character range with the given text.

void set ( String text)
          Replace the content of the text store with the given text.

Methods inherited from class java.lang. Object

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

Constructor Detail

GapTextStore

public GapTextStore(int lowWatermark,
                    int highWatermark)

Deprecated. use GapTextStore(int, int, float) instead

Creates a new empty text store using the specified low and high watermarks.

Parameters:: lowWatermark - unused - at the lower bound, the array is only resized when the content does not fit; highWatermark - if the gap is ever larger than this, it will automatically be shrunken (>= 0)

GapTextStore

public GapTextStore()

Equivalent to new GapTextStore(256, 4096, 0.1f).

Since:: 3.3

GapTextStore

public GapTextStore(int minSize,
                    int maxSize,
                    float maxGapFactor)

Creates an empty text store that uses re-allocation thresholds relative to the content length. Re-allocation is controlled by the gap factor, which is the quotient of the gap size and the array size. Re-allocation occurs if a change causes the gap factor to go outside [0, maxGapFactor]. When re-allocation occurs, the array is sized such that the gap factor is 0.5 * maxGapFactor. The gap size computed in this manner is bounded by the minSize and maxSize parameters.

A maxGapFactor of 0 creates a text store that never has a gap at all (if minSize is 0); a maxGapFactor of 1 creates a text store that doubles its size with every re-allocation and that never shrinks.

The minSize and maxSize parameters are absolute bounds to the allocated gap size. Use minSize to avoid frequent re-allocation for small documents. Use maxSize to avoid a huge gap being allocated for large documents.

Parameters:: minSize - the minimum gap size to allocate (>= 0; use 0 for no minimum); maxSize - the maximum gap size to allocate (>= minSize; use Integer.MAX_VALUE for no maximum); maxGapFactor - is the maximum fraction of the array that is occupied by the gap (0 <= maxGapFactor <= 1)
Since:: 3.3

Method Detail