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/**
 *Copyright [2009-2010] [dennis zhuang([email protected])]
 *Licensed under the Apache License, Version 2.0 (the "License");
 *you may not use this file except in compliance with the License. 
 *You may obtain a copy of the License at 
 *             http://www.apache.org/licenses/LICENSE-2.0 
 *Unless required by applicable law or agreed to in writing, 
 *software distributed under the License is distributed on an "AS IS" BASIS, 
 *WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, 
 *either express or implied. See the License for the specific language governing permissions and limitations under the License
 */
/**
 *Copyright [2009-2010] [dennis zhuang([email protected])]
 *Licensed under the Apache License, Version 2.0 (the "License");
 *you may not use this file except in compliance with the License.
 *You may obtain a copy of the License at
 *             http://www.apache.org/licenses/LICENSE-2.0
 *Unless required by applicable law or agreed to in writing,
 *software distributed under the License is distributed on an "AS IS" BASIS,
 *WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 *either express or implied. See the License for the specific language governing permissions and limitations under the License
 */
package com.google.code.yanf4j.util;

import java.util.ArrayList;
import java.util.List;

import com.google.code.yanf4j.buffer.IoBuffer;

/**
 * ByteBuffer matcher based on shift-and algorithm
 * 
 * @author dennis
 * 
 */
public class ShiftAndByteBufferMatcher implements ByteBufferMatcher {

	private int[] b;
	private int mask;

	private int patternLimit;
	private int patternPos;
	private int patternLen;

	public ShiftAndByteBufferMatcher(IoBuffer pat) {
		if (pat == null || pat.remaining() == 0) {
			throw new IllegalArgumentException("blank buffer");
		}
		this.patternLimit = pat.limit();
		this.patternPos = pat.position();
		this.patternLen = pat.remaining();
		preprocess(pat);
		this.mask = 1 << (this.patternLen - 1);
	}

	/**
	 * Ԥ����
	 * 
	 * @param pat
	 */
	private void preprocess(IoBuffer pat) {
		this.b = new int[256];
		for (int i = this.patternPos; i < this.patternLimit; i++) {
			int p = ByteBufferUtils.uByte(pat.get(i));
			this.b[p] = this.b[p] | (1 << i);
		}
	}

	public final List matchAll(IoBuffer buffer) {
		List matches = new ArrayList();
		int bufferLimit = buffer.limit();
		int d = 0;
		for (int pos = buffer.position(); pos < bufferLimit; pos++) {
			d <<= 1;
			d |= 1;
			d &= this.b[ByteBufferUtils.uByte(buffer.get(pos))];
			if ((d & this.mask) != 0) {
				matches.add(pos - this.patternLen + 1);
			}
		}
		return matches;
	}

	public final int matchFirst(IoBuffer buffer) {
		if (buffer == null) {
			return -1;
		}
		int bufferLimit = buffer.limit();
		int d = 0;
		for (int pos = buffer.position(); pos < bufferLimit; pos++) {
			d <<= 1;
			d |= 1;
			d &= this.b[ByteBufferUtils.uByte(buffer.get(pos))];
			if ((d & this.mask) != 0) {
				return pos - this.patternLen + 1;
			}
		}
		return -1;
	}

}