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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-or algorithm
 * 
 * @author dennis
 * 
 */
public class ShiftOrByteBufferMatcher implements ByteBufferMatcher {

  private int[] b;
  private int lim;

  private int patternLen;

  public ShiftOrByteBufferMatcher(IoBuffer pat) {
    if (pat == null || pat.remaining() == 0) {
      throw new IllegalArgumentException("blank buffer");
    }
    this.patternLen = pat.remaining();
    preprocess(pat);
  }

  /**
   * Ԥ����
   * 
   * @param pat
   */
  private void preprocess(IoBuffer pat) {
    this.b = new int[256];
    this.lim = 0;
    for (int i = 0; i < 256; i++) {
      this.b[i] = ~0;

    }
    for (int i = 0, j = 1; i < this.patternLen; i++, j <<= 1) {
      this.b[ByteBufferUtils.uByte(pat.get(i))] &= ~j;
      this.lim |= j;
    }
    this.lim = ~(this.lim >> 1);

  }

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

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

}