COSFilterInputStream.java

package com.tom_roush.pdfbox.pdmodel.interactive.digitalsignature;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;

public class COSFilterInputStream extends FilterInputStream
{
	private final int[] byteRange;
	private long position = 0;

	public COSFilterInputStream(InputStream in, int[] byteRange)
	{
		super(in);
		this.byteRange = byteRange;
	}

	public COSFilterInputStream(byte[] in, int[] byteRange)
	{
		super(new ByteArrayInputStream(in));
		this.byteRange = byteRange;
	}

	@Override
	public int read() throws IOException
	{
		nextAvailable();
		int i = super.read();
		if (i>-1)
		{
			++position;
		}
		return i;
	}

	@Override
	public int read(byte[] b) throws IOException
	{
		return read(b,0,b.length);
	}

	@Override
	public int read(byte[] b, int off, int len) throws IOException
	{
		if (len == 0)
		{
			return 0;
		}

		int c = read();
		if (c == -1)
		{
			return -1;
		}
		b[off] = (byte)c;

		int i = 1;
		try
		{
			for (; i < len ; i++)
			{
				c = read();
				if (c == -1)
				{
					break;
				}
				b[off + i] = (byte)c;
			}
		}
		catch (IOException ee)
		{
		}
		return i;
	}

	private boolean inRange() throws IOException
	{
		long pos = position;
		for (int i = 0; i<byteRange.length/2;++i)
		{
			if(byteRange[i*2] <= pos &&  byteRange[i*2]+byteRange[i*2+1]>pos)
			{
				return true;
			}
		}
		return false;
	}

	private void nextAvailable() throws IOException
	{
		while (!inRange())
		{
			++position;
			if(super.read()<0)
			{
				break;
			}
		}
	}

	public byte[] toByteArray() throws IOException 
	{
		ByteArrayOutputStream byteOS = new ByteArrayOutputStream();
		byte[] buffer = new byte[1024];
		int c;
		while ((c = this.read(buffer)) != -1)
		{
			byteOS.write(buffer, 0, c);
		}
		return byteOS.toByteArray();
	}
}