ByteMatcher.java

/**
 * Copyright 2011 Yusuke Matsubara
 *
 * 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 org.wikimedia.wikihadoop;

import java.io.*;

import org.apache.hadoop.io.DataOutputBuffer;
import org.apache.hadoop.fs.Seekable;

public class ByteMatcher {
  private final InputStream in;
  private final Seekable pos;
  private long lastPos;
  private long currentPos;
  private long bytes;
  public ByteMatcher(InputStream in, Seekable pos) throws IOException {
    this.in = in;
    this.pos = pos;
    this.bytes = 0;
    this.lastPos = -1;
    this.currentPos = -1;
  }
  public ByteMatcher(SeekableInputStream is) throws IOException {
    this(is, is);
  }
  public long getReadBytes() {
    return this.bytes;
  }
  public long getPos() throws IOException {
    return this.pos.getPos();
  }
  public long getLastUnmatchPos() { return this.lastPos; }

  public void skip(long len) throws IOException {
    this.in.skip(len);
    this.bytes += len;
  }

  boolean readUntilMatch(String textPat, DataOutputBuffer outBufOrNull, long end) throws IOException {
    byte[] match = textPat.getBytes("UTF-8");
    int i = 0;
    while (true) {
      int b = this.in.read();
      // end of file:
      if (b == -1) {
        System.err.println("eof 1");
        return false;
      }
      ++this.bytes;    //! TODO: count up later in batch
      // save to buffer:
      if (outBufOrNull != null)
        outBufOrNull.write(b);
      
      // check if we're matching:
      if (b == match[i]) {
        i++;
        if (i >= match.length)
          return true;
      } else {
        i = 0;
        if ( this.currentPos != this.getPos() ) {
          this.lastPos = this.currentPos;
          this.currentPos = this.getPos();
        }
      }
      // see if we've passed the stop point:
      if (i == 0 && this.pos.getPos() >= end) {
        System.err.println("eof 2: end=" + end);
        return false;
      }
    }
  }
}