/*
 * Copyright (c) 1997, 2018 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0, which is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

/* FROM mail.jar */
package org.jvnet.mimepull;

import java.io.*;

This class is to support reading CRLF terminated lines that
contain only US-ASCII characters from an input stream. Provides
functionality that is similar to the deprecated 
DataInputStream.readLine(). Expected use is to read
lines as String objects from a RFC822 stream.
It is implemented as a FilterInputStream, so one can just wrap 
this class around any input stream and read bytes from this filter.
Author:
John Mani/**
 * This class is to support reading CRLF terminated lines that
 * contain only US-ASCII characters from an input stream. Provides
 * functionality that is similar to the deprecated 
 * <code>DataInputStream.readLine()</code>. Expected use is to read
 * lines as String objects from a RFC822 stream.
 *
 * It is implemented as a FilterInputStream, so one can just wrap 
 * this class around any input stream and read bytes from this filter.
 * 
 * @author John Mani
 */

final class LineInputStream extends FilterInputStream {

    private char[] lineBuffer = null; // reusable byte buffer
    private static int MAX_INCR = 1024*1024;	// 1MB

    public LineInputStream(InputStream in) {
	super(in);
    }

    
Read a line containing only ASCII characters from the input 
stream. A line is terminated by a CR or NL or CR-NL sequence.
A common error is a CR-CR-NL sequence, which will also terminate
a line.
The line terminator is not returned as part of the returned 
String. Returns null if no data is available. 

This class is similar to the deprecated 
DataInputStream.readLine()
/**
     * Read a line containing only ASCII characters from the input 
     * stream. A line is terminated by a CR or NL or CR-NL sequence.
     * A common error is a CR-CR-NL sequence, which will also terminate
     * a line.
     * The line terminator is not returned as part of the returned 
     * String. Returns null if no data is available. <p>
     *
     * This class is similar to the deprecated 
     * <code>DataInputStream.readLine()</code>
     */
    public String readLine() throws IOException {
	//InputStream in = this.in;
	char[] buf = lineBuffer;

	if (buf == null) {
            buf = lineBuffer = new char[128];
        }

	int c1;
	int room = buf.length;
	int offset = 0;

	while ((c1 = in.read()) != -1) {
	    if (c1 == '\n') {
                break;
            } else if (c1 == '\r') {
		// Got CR, is the next char NL ?
		boolean twoCRs = false;
		if (in.markSupported()) {
                    in.mark(2);
                }
		int c2 = in.read();
		if (c2 == '\r') {		// discard extraneous CR
		    twoCRs = true;
		    c2 = in.read();
		}
		if (c2 != '\n') {
		    /*
		     * If the stream supports it (which we hope will always
		     * be the case), reset to after the first CR.  Otherwise,
		     * we wrap a PushbackInputStream around the stream so we
		     * can unread the characters we don't need.  The only
		     * problem with that is that the caller might stop
		     * reading from this LineInputStream, throw it away,
		     * and then start reading from the underlying stream.
		     * If that happens, the pushed back characters will be
		     * lost forever.
		     */
		    if (in.markSupported()) {
                        in.reset();
                    } else {
			if (!(in instanceof PushbackInputStream)) {
                            in /*= this.in*/ = new PushbackInputStream(in, 2);
                        }
			if (c2 != -1) {
                            ((PushbackInputStream)in).unread(c2);
                        }
			if (twoCRs) {
                            ((PushbackInputStream)in).unread('\r');
                        }
		    }
		}
		break; // outa here.
	    }

	    // Not CR, NL or CR-NL ...
	    // .. Insert the byte into our byte buffer
	    if (--room < 0) { // No room, need to grow.
		if (buf.length < MAX_INCR) {
                    buf = new char[buf.length * 2];
                } else {
                    buf = new char[buf.length + MAX_INCR];
                }
		room = buf.length - offset - 1;
		System.arraycopy(lineBuffer, 0, buf, 0, offset);
		lineBuffer = buf;
	    }
	    buf[offset++] = (char)c1;
	}

	if ((c1 == -1) && (offset == 0)) {
            return null;
        }
	
	return String.copyValueOf(buf, 0, offset);
    }
}