Package 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
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:
Restriction:
This class is not intended to be subclassed by clients.

  • Constructor Details

    • GapTextStore

      @Deprecated 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 Details

    • get

      public final char get(int offset)
      Description copied from interface: ITextStore
      Returns the character at the specified offset.
      Specified by:
      get in interface ITextStore
      Parameters:
      offset - the offset in this text store
      Returns:
      the character at this offset

    • get

      public final String get(int offset, int length)
      Description copied from interface: ITextStore
      Returns the text of the specified character range.
      Specified by:
      get in interface ITextStore
      Parameters:
      offset - the offset of the range
      length - the length of the range
      Returns:
      the text of the range

    • getLength

      public final int getLength()
      Description copied from interface: ITextStore
      Returns number of characters stored in this text store.
      Specified by:
      getLength in interface ITextStore
      Returns:
      the number of characters stored in this text store

    • set

      public final void set(String text)
      Description copied from interface: ITextStore
      Replace the content of the text store with the given text. Convenience method for replace(0, getLength(), text.
      Specified by:
      set in interface ITextStore
      Parameters:
      text - the new content of the text store

    • replace

      public final void replace(int offset, int length, String text)
      Description copied from interface: ITextStore
      Replaces the specified character range with the given text. replace(getLength(), 0, "some text") is a valid call and appends text to the end of the text store.
      Specified by:
      replace in interface ITextStore
      Parameters:
      offset - the offset of the range to be replaced
      length - the number of characters to be replaced
      text - the substitution text

    • getContentAsString

      protected String getContentAsString()
      Returns a copy of the content of this text store. For internal use only.
      Returns:
      a copy of the content of this text store

    • getGapStartIndex

      protected int getGapStartIndex()
      Returns the start index of the gap managed by this text store. For internal use only.
      Returns:
      the start index of the gap managed by this text store

    • getGapEndIndex

      protected int getGapEndIndex()
      Returns the end index of the gap managed by this text store. For internal use only.
      Returns:
      the end index of the gap managed by this text store