/*
 * Created on Jul 23, 2004
 */
package com.philschatz.swt.dnd;

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

import org.eclipse.swt.internal.win32.BITMAPINFOHEADER;

/**
 * Converts a DIB (Device Independent Bitmap) taken from the clipboard, into a
 * Bitmap File.
 *
 * To do this, this InputStream prepends a BITMAPFILEHEADER to the stream.
 *
 * See
 * msdn.microsoft.com/library/en-us/winui/winui/windowsuserinterface/dataexchange/clipboard/clipboardformats.asp#_win32_Standard_Clipboard_Formats
 *
 *
 * If you found this class useful (or made some improvements) drop me a line.
 *
 *
 * @author Philip Schatz ( www.philschatz.com )
 */
class PrependWinBMPHeaderFilterInputStream extends InputStream {

        public static final int BITMAPFILEHEADER_SIZEOF = 14;
        private final InputStream in;
        private final byte[] buffer;
        private int index = 0;

        public PrependWinBMPHeaderFilterInputStream(InputStream dibStream) {
                //defined as 54
                final int offset = PrependWinBMPHeaderFilterInputStream.BITMAPFILEHEADER_SIZEOF
                                + BITMAPINFOHEADER.sizeof;

                this.in = dibStream;
                this.buffer = new byte[PrependWinBMPHeaderFilterInputStream.BITMAPFILEHEADER_SIZEOF];

                //see BITMAPFILEHEADER in windows documentation
                this.buffer[0] = 'B';
                this.buffer[1] = 'M';
                // write the offset in byte format
                this.buffer[10] = offset;
        }
        public int read() throws IOException {
                if (this.index < this.buffer.length) {
                        return 0xff & this.buffer[this.index++];
                }
                return this.in.read();
        }
}