/*******************************************************************************
 * Copyright (c) 2001, 2005 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *     Jens Lukowski/Innoopract - initial renaming/restructuring
 *     
 *******************************************************************************/
package org.eclipse.wst.sse.core.internal.encoding.util;

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

import org.eclipse.wst.sse.core.internal.encoding.CodedIO;

/**
 * This is an "adapter" class, simply to get in input stream to act like a
 * reader. We could not use InputStreamReader directly because its internal
 * buffers are not controllable, and it sometimes pulls too much out of input
 * stream (even when it wasn't needed for our purposes).
 * 
 * The use of this class is highly specialized and by not means meant to be
 * general purpose. Its use is restricted to those cases where the input
 * stream can be regarded as ascii just long enough to determine what the real
 * encoding should be.
 */

public class ByteReader extends Reader {

	
	public static final int DEFAULT_BUFFER_SIZE = CodedIO.MAX_BUF_SIZE;

	protected byte[] fBuffer;

	protected InputStream fInputStream;

	protected ByteReader() {
		super();
	}

	public ByteReader(InputStream inputStream) {
		this(inputStream, DEFAULT_BUFFER_SIZE);
		if (!inputStream.markSupported()) {
			throw new IllegalArgumentException("ByteReader is required to have a resettable stream"); //$NON-NLS-1$
		}
	}

	public ByteReader(InputStream inputStream, int size) {
		this.fInputStream = inputStream;
		if (!inputStream.markSupported()) {
			throw new IllegalArgumentException("ByteReader is required to have a resettable stream"); //$NON-NLS-1$
		}
		this.fBuffer = new byte[size];

	}

	public void close() throws IOException {
		this.fInputStream.close();
	}

	public void mark(int readAheadLimit) {
		this.fInputStream.mark(readAheadLimit);
	}

	public boolean markSupported() {
		return true;
	}

	public int read() throws IOException {
		int b0 = this.fInputStream.read();
		return (b0 & 0x00FF);
	}

	public int read(char ch[], int offset, int length) throws IOException {
		if (length > this.fBuffer.length) {
			length = this.fBuffer.length;
		}

		int count = this.fInputStream.read(this.fBuffer, 0, length);

		for (int i = 0; i < count; i++) {
			int b0 = this.fBuffer[i];
			// the 0x00FF is to "lose" the negative bits filled in the byte to
			// int conversion
			// (and which would be there if cast directly from byte to char).
			char c0 = (char) (b0 & 0x00FF);
			ch[offset + i] = c0;
		}
		return count;
	}

	public boolean ready() throws IOException {
		return this.fInputStream.available() > 0;
	}

	public void reset() throws IOException {
		this.fInputStream.reset();
	}

	public long skip(long n) throws IOException {
		return this.fInputStream.skip(n);
	}

}