/*
 * The Apache Software License, Version 1.1
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 * reserved.
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 * modification, are permitted provided that the following conditions
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 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
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 * 2. Redistributions in binary form must reproduce the above copyright
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 *       "This product includes software developed by the
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 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
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 * 5. Products derived from this software may not be called "Apache",
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 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation and was
 * originally based on software copyright (c) 1999, International
 * Business Machines, Inc., http://www.apache.org.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

package org.apache.jasper.xmlparser;

import java.io.InputStream;
import java.io.IOException;
import java.io.Reader;
import org.apache.jasper.compiler.Localizer;

/**
 * A simple ASCII byte reader. This is an optimized reader for reading
 * byte streams that only contain 7-bit ASCII characters.
 *
 * @author Andy Clark, IBM
 *
 * @version $Id: ASCIIReader.java,v 1.2 2003/01/22 20:08:25 luehe Exp $
 */
public class ASCIIReader
    extends Reader {

    //
    // Constants
    //

    /** Default byte buffer size (2048). */
    public static final int DEFAULT_BUFFER_SIZE = 2048;

    //
    // Data
    //

    /** Input stream. */
    protected InputStream fInputStream;

    /** Byte buffer. */
    protected byte[] fBuffer;

    //
    // Constructors
    //

    /** 
     * Constructs an ASCII reader from the specified input stream 
     * and buffer size.
     *
     * @param inputStream The input stream.
     * @param size        The initial buffer size.
     */
    public ASCIIReader(InputStream inputStream, int size) {
        fInputStream = inputStream;
        fBuffer = new byte[size];
    }

    //
    // Reader methods
    //

    /**
     * Read a single character.  This method will block until a character is
     * available, an I/O error occurs, or the end of the stream is reached.
     *
     * <p> Subclasses that intend to support efficient single-character input
     * should override this method.
     *
     * @return     The character read, as an integer in the range 0 to 127
     *             (<tt>0x00-0x7f</tt>), or -1 if the end of the stream has
     *             been reached
     *
     * @exception  IOException  If an I/O error occurs
     */
    public int read() throws IOException {
        int b0 = fInputStream.read();
        if (b0 > 0x80) {
            throw new IOException(Localizer.getMessage("jsp.error.xml.invalidASCII",
						       Integer.toString(b0)));
        }
        return b0;
    } // read():int

    /**
     * Read characters into a portion of an array.  This method will block
     * until some input is available, an I/O error occurs, or the end of the
     * stream is reached.
     *
     * @param      ch     Destination buffer
     * @param      offset Offset at which to start storing characters
     * @param      length Maximum number of characters to read
     *
     * @return     The 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 ch[], int offset, int length) throws IOException {
        if (length > fBuffer.length) {
            length = fBuffer.length;
        }
        int count = fInputStream.read(fBuffer, 0, length);
        for (int i = 0; i < count; i++) {
            int b0 = fBuffer[i];
            if (b0 > 0x80) {
                throw new IOException(Localizer.getMessage("jsp.error.xml.invalidASCII",
							   Integer.toString(b0)));
            }
            ch[offset + i] = (char)b0;
        }
        return count;
    } // read(char[],int,int)

    /**
     * Skip characters.  This method will block until some characters are
     * available, an I/O error occurs, or the end of the stream is reached.
     *
     * @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 {
        return fInputStream.skip(n);
    } // skip(long):long

    /**
     * Tell whether this stream is ready to be read.
     *
     * @return True if the next read() is guaranteed not to block for input,
     * false otherwise.  Note that returning false does not guarantee that the
     * next read will block.
     *
     * @exception  IOException  If an I/O error occurs
     */
    public boolean ready() throws IOException {
	return false;
    } // ready()

    /**
     * Tell whether this stream supports the mark() operation.
     */
    public boolean markSupported() {
	return fInputStream.markSupported();
    } // markSupported()

    /**
     * Mark the present position in the stream.  Subsequent calls to reset()
     * will attempt to reposition the stream to this point.  Not all
     * character-input streams support the mark() operation.
     *
     * @param  readAheadLimit  Limit on the number of characters that may be
     *                         read while still preserving the mark.  After
     *                         reading this many characters, attempting to
     *                         reset the stream may fail.
     *
     * @exception  IOException  If the stream does not support mark(),
     *                          or if some other I/O error occurs
     */
    public void mark(int readAheadLimit) throws IOException {
	fInputStream.mark(readAheadLimit);
    } // mark(int)

    /**
     * Reset the stream.  If the stream has been marked, then attempt to
     * reposition it at the mark.  If the stream has not been marked, then
     * attempt to reset it in some way appropriate to the particular stream,
     * for example by repositioning it to its starting point.  Not all
     * character-input streams support the reset() operation, and some support
     * reset() without supporting mark().
     *
     * @exception  IOException  If the stream has not been marked,
     *                          or if the mark has been invalidated,
     *                          or if the stream does not support reset(),
     *                          or if some other I/O error occurs
     */
    public void reset() throws IOException {
        fInputStream.reset();
    } // reset()

    /**
     * Close the stream.  Once a stream has been closed, further read(),
     * ready(), mark(), or reset() invocations will throw an IOException.
     * Closing a previously-closed stream, however, has no effect.
     *
     * @exception  IOException  If an I/O error occurs
     */
     public void close() throws IOException {
         fInputStream.close();
     } // close()

} // class ASCIIReader
