input.java

KWIC系统 采用管道/过滤器风格实现

import java.io.IOException;
import java.io.InputStream;



public class Input extends Filter
{
  private InputStream in_;

  public Input(InputStream in, Pipe output)
  {
    super(null, output);
    in_ = in;     //接通数据源
  }

/* This method reads and parses a KWIC input file. The parsed data is written to the output pipe. */

  protected void transform()
  {
    try{
      boolean is_new_line = false;
      boolean is_new_word = false;
      boolean is_line_started = false;

      int c = in_.read();   //从数据源读取数据

      while(c != -1){
        switch((byte) c){
        case '\n':
          is_new_line = true;
          break;
        case ' ':
          is_new_word = true;
          break;
        case '\t':
          is_new_word = true;
          break;
        case '\r':
          break;
        default:
          if(is_new_line)
          {
            output_.write('\n');
            is_new_line = false;
            is_line_started = false;
          }
          if(is_new_word)
          {
            if(is_line_started)
              output_.write(' ');
            is_new_word = false;
          }
          output_.write(c);     //写到"output"中
          is_line_started = true;
          break;
        }
        c = in_.read();
      }

      output_.write('\n');
      output_.closeWriter();
    }catch(IOException exc){
      exc.printStackTrace();
      System.err.println("KWIC Error: Could not read the input file.");
      System.exit(1);
    }
  }
}