Java 1.2 How-To/JavaHowTo.iso/3rdParty/jbuilder/unsupported/JDK1.2beta3/SOURCE/SRC.ZIP/java/io/CharArrayReader.java

Java Source | 1998-03-20 | 4.7 KB | 191 lines

/*
 * @(#)CharArrayReader.java    1.10 98/03/18
 *
 * Copyright 1996-1998 by Sun Microsystems, Inc.,
 * 901 San Antonio Road, Palo Alto, California, 94303, U.S.A.
 * All rights reserved.
 *
 * This software is the confidential and proprietary information
 * of Sun Microsystems, Inc. ("Confidential Information").  You
 * shall not disclose such Confidential Information and shall use
 * it only in accordance with the terms of the license agreement
 * you entered into with Sun.
 */

package java.io;

/**
 * This class implements a character buffer that can be used as a
 * character-input stream.
 *
 * @author    Herb Jellinek
 * @version     1.10, 03/18/98
 * @since       JDK1.1
 */
public
class CharArrayReader extends Reader {
    /** Character buffer */
    protected char buf[];

    /** Current buffer position */
    protected int pos;

    /** Position of mark in buffer */
    protected int markedPos = 0;

    /** Number of valid characters in buffer */
    protected int count;

    /**
     * Create an CharArrayReader from the specified array of chars.
     * @param buf    Input buffer (not copied)
     */
    public CharArrayReader(char buf[]) {
    this.buf = buf;
        this.pos = 0;
    this.count = buf.length;
    }

    /**
     * Create an CharArrayReader from the specified array of chars.
     * @param buf    Input buffer (not copied)
     * @param offset    Offset of the first char to read
     * @param length    Number of chars to read
     */
    public CharArrayReader(char buf[], int offset, int length) {
    this.buf = buf;
        this.pos = offset;
    this.count = Math.min(offset + length, buf.length);
        this.markedPos = offset;
    }

    /** Check to make sure that the stream has not been closed */
    private void ensureOpen() throws IOException {
    if (buf == null)
        throw new IOException("Stream closed");
    }

    /**
     * Read a single character.
     *
     * @exception   IOException  If an I/O error occurs
     */
    public int read() throws IOException {
    synchronized (lock) {
        ensureOpen();
        if (pos >= count)
        return -1;
        else
        return buf[pos++];
    }
    }

    /**
     * Read characters into a portion of an array.
     * @param b     Destination buffer
     * @param off  Offset at which to start storing characters
     * @param len   Maximum number of characters to read
     * @return  The actual number of characters read, or -1 if
     *         the end of the stream has been reached
     *
     * @exception   IOException  If an I/O error occurs
     */
    public int read(char b[], int off, int len) throws IOException {
    synchronized (lock) {
        ensureOpen();
        if (pos >= count) {
        return -1;
        }
        if (pos + len > count) {
        len = count - pos;
        }
        if (len <= 0) {
        return 0;
        }
        System.arraycopy(buf, pos, b, off, len);
        pos += len;
        return len;
    }
    }

    /**
     * Skip characters.
     * @param n The number of characters to skip
     * @return    The number of characters actually skipped
     *
     * @exception   IOException  If an I/O error occurs
     */
    public long skip(long n) throws IOException {
    synchronized (lock) {
        ensureOpen();
        if (pos + n > count) {
        n = count - pos;
        }
        if (n < 0) {
        return 0;
        }
        pos += n;
        return n;
    }
    }

    /**
     * Tell whether this stream is ready to be read.  Character-array readers
     * are always ready to be read.
     *
     * @exception  IOException  If an I/O error occurs
     */
    public boolean ready() throws IOException {
    synchronized (lock) {
        ensureOpen();
        return (count - pos) > 0;
    }
    }

    /**
     * Tell whether this stream supports the mark() operation, which it does.
     */
    public boolean markSupported() {
    return true;
    }

    /**
     * Mark the present position in the stream.  Subsequent calls to reset()
     * will reposition the stream to this point.
     *
     * @param  readAheadLimit  Limit on the number of characters that may be
     *                         read while still preserving the mark.  Because
     *                         the stream's input comes from a character array,
     *                         there is no actual limit; hence this argument is
     *                         ignored.
     *
     * @exception  IOException  If an I/O error occurs
     */
    public void mark(int readAheadLimit) throws IOException {
    synchronized (lock) {
        ensureOpen();
        markedPos = pos;
    }
    }

    /**
     * Reset the stream to the most recent mark, or to the beginning if it has
     * never been marked.
     *
     * @exception  IOException  If an I/O error occurs
     */
    public void reset() throws IOException {
    synchronized (lock) {
        ensureOpen();
        pos = markedPos;
    }
    }

    /**
     * Close the stream.
     */
    public void close() {
    buf = null;
    }
}