/jEdit/tags/jedit-4-3-pre5/bsh/CommandLineReader.java

  1/*****************************************************************************
  2 *                                                                           *
  3 *  This file is part of the BeanShell Java Scripting distribution.          *
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 11 *                                                                           *
 12 *  The Original Code is BeanShell. The Initial Developer of the Original    *
 13 *  Code is Pat Niemeyer. Portions created by Pat Niemeyer are Copyright     *
 14 *  (C) 2000.  All Rights Reserved.                                          *
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 16 *  GNU Public License Notice:                                               *
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 27 *                                                                           *
 28 *  Patrick Niemeyer (pat@pat.net)                                           *
 29 *  Author of Learning Java, O'Reilly & Associates                           *
 30 *  http://www.pat.net/~pat/                                                 *
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 32 *****************************************************************************/
 33
 34
 35package bsh;
 36
 37import java.io.*;
 38
 39/**
 40	This is a quick hack to turn empty lines entered interactively on the 
 41	command line into ';\n' empty lines for the interpreter.  It's just more 
 42	pleasant to be able to hit return on an empty line and see the prompt 
 43	reappear.
 44		
 45	This is *not* used when text is sourced from a file non-interactively.
 46*/
 47class CommandLineReader extends FilterReader {
 48
 49    public CommandLineReader( Reader in ) {
 50		super(in);
 51    }
 52
 53	static final int 
 54		normal = 0,
 55		lastCharNL = 1,
 56		sentSemi = 2;
 57
 58	int state = lastCharNL;
 59
 60    public int read() throws IOException {
 61		int b;
 62
 63		if ( state == sentSemi ) {
 64			state = lastCharNL;
 65			return '\n';
 66		}
 67
 68		// skip CR
 69        while ( (b = in.read()) == '\r' );
 70
 71		if ( b == '\n' )
 72			if ( state == lastCharNL ) {
 73				b = ';';
 74				state = sentSemi;
 75			} else
 76				state = lastCharNL;
 77		else
 78			state = normal;
 79
 80		return b;
 81    }
 82
 83	/**
 84		This is a degenerate implementation.
 85		I don't know how to keep this from blocking if we try to read more
 86		than one char...  There is no available() for Readers ??
 87	*/
 88    public int read(char buff[], int off, int len) throws IOException 
 89	{
 90		int b = read();
 91		if ( b == -1 )
 92			return -1;  // EOF, not zero read apparently
 93		else {
 94			buff[off]=(char)b;
 95			return 1;
 96		}
 97    }
 98
 99	// Test it
100	public static void main( String [] args ) throws Exception {
101		Reader in = new CommandLineReader( new InputStreamReader(System.in) );
102		while ( true )
103			System.out.println( in.read() );
104		
105	}
106}
107