90 lines
2.5 KiB
Java
90 lines
2.5 KiB
Java
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/*
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(C) Copyright Taligent, Inc. 1996 - All Rights Reserved
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(C) Copyright IBM Corp. 1996 - All Rights Reserved
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The original version of this source code and documentation is copyrighted and
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owned by Taligent, Inc., a wholly-owned subsidiary of IBM. These materials are
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provided under terms of a License Agreement between Taligent and Sun. This
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technology is protected by multiple US and International patents. This notice and
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attribution to Taligent may not be removed.
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Taligent is a registered trademark of Taligent, Inc.
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*/
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package com.ibm.text.utility;
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public class FastByteBinarySearch
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{
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private byte dataArray[];
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private int auxStart;
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private int power;
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private static final int exp2[] = { 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, 65536, 131072 };
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public FastByteBinarySearch(byte data[])
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{
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if (data.length < 1) throw new IllegalArgumentException();
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if (data.length >= exp2[exp2.length-1]) throw new IllegalArgumentException();
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dataArray = data;
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for (power = exp2.length-1; power > 0 && dataArray.length < exp2[power]; power--) {}
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if (exp2[power] != dataArray.length) {
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auxStart = dataArray.length - exp2[power];
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}
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else {
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auxStart = 0;
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}
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}
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public byte[] getData()
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{
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return dataArray;
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}
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public int findIndex(int value)
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{
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int index = exp2[power]-1;
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if (value >= dataArray[auxStart]) {
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index += auxStart;
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}
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switch (power) {
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case 17:
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if (value < dataArray[index-65536]) index -= 65536;
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case 16:
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if (value < dataArray[index-32768]) index -= 32768;
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case 15:
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if (value < dataArray[index-16384]) index -= 16384;
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case 14:
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if (value < dataArray[index-8192]) index -= 8192;
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case 13:
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if (value < dataArray[index-4096]) index -= 4096;
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case 12:
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if (value < dataArray[index-2048]) index -= 2048;
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case 11:
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if (value < dataArray[index-1024]) index -= 1024;
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case 10:
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if (value < dataArray[index-512]) index -= 512;
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case 9:
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if (value < dataArray[index-256]) index -= 256;
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case 8:
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if (value < dataArray[index-128]) index -= 128;
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case 7:
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if (value < dataArray[index-64]) index -= 64;
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case 6:
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if (value < dataArray[index-32]) index -= 32;
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case 5:
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if (value < dataArray[index-16]) index -= 16;
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case 4:
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if (value < dataArray[index-8]) index -= 8;
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case 3:
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if (value < dataArray[index-4]) index -= 4;
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case 2:
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if (value < dataArray[index-2]) index -= 2;
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case 1:
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if (value < dataArray[index-1]) index -= 1;
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case 0:
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if (value < dataArray[index]) index -= 1;
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}
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return index;
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}
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}
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