95 lines
3.0 KiB
Java
95 lines
3.0 KiB
Java
/**
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* Copyright [2009-2010] [dennis zhuang(killme2008@gmail.com)] Licensed under the Apache License,
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* Version 2.0 (the "License"); you may not use this file except in compliance with the License. You
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* may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by
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* applicable law or agreed to in writing, software distributed under the License is distributed on
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* an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
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* the License for the specific language governing permissions and limitations under the License
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*/
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/**
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* Copyright [2009-2010] [dennis zhuang(killme2008@gmail.com)] Licensed under the Apache License,
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* Version 2.0 (the "License"); you may not use this file except in compliance with the License. You
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* may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by
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* applicable law or agreed to in writing, software distributed under the License is distributed on
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* an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
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* the License for the specific language governing permissions and limitations under the License
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*/
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package com.google.code.yanf4j.util;
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import java.util.ArrayList;
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import java.util.List;
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import com.google.code.yanf4j.buffer.IoBuffer;
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/**
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* ByteBuffer matcher based on shift-and algorithm
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*
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* @author dennis
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*
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*/
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public class ShiftAndByteBufferMatcher implements ByteBufferMatcher {
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private int[] b;
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private int mask;
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private int patternLimit;
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private int patternPos;
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private int patternLen;
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public ShiftAndByteBufferMatcher(IoBuffer pat) {
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if (pat == null || pat.remaining() == 0) {
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throw new IllegalArgumentException("blank buffer");
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}
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this.patternLimit = pat.limit();
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this.patternPos = pat.position();
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this.patternLen = pat.remaining();
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preprocess(pat);
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this.mask = 1 << (this.patternLen - 1);
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}
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/**
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* Ԥ<><D4A4><EFBFBD><EFBFBD>
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*
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* @param pat
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*/
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private void preprocess(IoBuffer pat) {
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this.b = new int[256];
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for (int i = this.patternPos; i < this.patternLimit; i++) {
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int p = ByteBufferUtils.uByte(pat.get(i));
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this.b[p] = this.b[p] | (1 << i);
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}
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}
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public final List<Integer> matchAll(IoBuffer buffer) {
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List<Integer> matches = new ArrayList<Integer>();
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int bufferLimit = buffer.limit();
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int d = 0;
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for (int pos = buffer.position(); pos < bufferLimit; pos++) {
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d <<= 1;
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d |= 1;
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d &= this.b[ByteBufferUtils.uByte(buffer.get(pos))];
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if ((d & this.mask) != 0) {
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matches.add(pos - this.patternLen + 1);
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}
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}
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return matches;
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}
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public final int matchFirst(IoBuffer buffer) {
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if (buffer == null) {
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return -1;
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}
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int bufferLimit = buffer.limit();
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int d = 0;
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for (int pos = buffer.position(); pos < bufferLimit; pos++) {
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d <<= 1;
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d |= 1;
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d &= this.b[buffer.get(pos) & 0XFF];
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if ((d & this.mask) != 0) {
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return pos - this.patternLen + 1;
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}
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}
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return -1;
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}
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}
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