001package votorola.g.util; // Copyright 2001-2003, 2006, Michael Allan. Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Votorola Software"), to deal in the Votorola Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicence, and/or sell copies of the Votorola Software, and to permit persons to whom the Votorola Software is furnished to do so, subject to the following conditions: The preceding copyright notice and this permission notice shall be included in all copies or substantial portions of the Votorola Software. THE VOTOROLA SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE VOTOROLA SOFTWARE OR THE USE OR OTHER DEALINGS IN THE VOTOROLA SOFTWARE. 002 003import votorola.g.lang.*; 004 005 006/** Index offsetter for a sequence of fixed size. It implements a logical index 007 * whose start (logical zero) may be offset from actual zero, and whose increments 008 * will wrap around the end of sequence. 009 */ 010public @ThreadRestricted("touch") final class IndexOffsetter implements java.io.Serializable 011{ 012 013 private static final long serialVersionUID = 0L; 014 015 016 017 /** Constructs an IndexOffsetter. 018 * 019 * @param s size per {@linkplain #size() size}() 020 */ 021 public IndexOffsetter( int s ) { size = s; } 022 023 024 025 // ------------------------------------------------------------------------------------ 026 027 028 /** Returns the actual index of a given logical index. 029 * 030 * @param logicalIndex logical index in sequence (positive or negative) 031 * @return actual index, wrapped as necessary around the end of the sequence 032 * 033 * @throws ArrayIndexOutOfBoundsException if |logicalIndex| >= size() 034 */ 035 public int actualIndex( int logicalIndex ) 036 { 037 if( Math.abs(logicalIndex) >= size ) throw new ArrayIndexOutOfBoundsException( logicalIndex ); 038 039 int actualIndex = actualIndexOfLogicalZero + logicalIndex; 040 if( actualIndex >= size ) actualIndex -= size; 041 else if( actualIndex < 0 ) actualIndex += size; 042 return actualIndex; 043 } 044 045 046 047 /** Sets the actual index of logical index zero. When this is zero (the default), 048 * the logical index is identical to the actual index. 049 * 050 * @throws ArrayIndexOutOfBoundsException if actualIndex < 0 051 * or actualIndex >= size() 052 */ 053 public @ThreadRestricted void setActualIndexOfLogicalZero( int actualIndex ) 054 { 055 if( actualIndex < 0 || actualIndex >= size ) throw new ArrayIndexOutOfBoundsException( actualIndex ); 056 057 actualIndexOfLogicalZero = actualIndex; 058 } 059 060 061 private int actualIndexOfLogicalZero = 0; // by default 062 063 064 065 /** Returns the size of the sequence. 066 */ 067 public int size() { return size; } 068 069 070 private final int size; 071 072 073 074}