http://www.bouncycastle.org/java.html: The Bouncy Castle Java APIs for CMS, PKCS, EAC, TSP, CMP, CRMF, OCSP, and certificate generation. This jar contains APIs for JDK 1.5 to JDK 1.8. The APIs can be used in conjunction with a JCE/JCA provider such as the one provided with the Bouncy Castle Cryptography APIs.
  • The Legion of the Bouncy Castle Inc. 
package org.bouncycastle.mime;

import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;

import org.bouncycastle.mime.smime.SMimeParserContext;

public class CanonicalOutputStream
    extends FilterOutputStream
{
    protected int lastb;
    protected static byte newline[];
    private final boolean is7Bit;

    public CanonicalOutputStream(SMimeParserContext parserContext, Headers headers, OutputStream outputstream)
    {
        super(outputstream);
        lastb = -1;
        // TODO: eventually may need to handle multiparts with binary...
        if (headers.getContentType() != null)
        {
            is7Bit = headers.getContentType() != null && !headers.getContentType().equals("binary");
        }
        else
        {
            is7Bit = parserContext.getDefaultContentTransferEncoding().equals("7bit");
        }
    }

    public void write(int i)
        throws IOException
    {
        if (is7Bit)
        {
            if (i == '\r')
            {
                out.write(newline);
            }
            else if (i == '\n')
            {
                if (lastb != '\r')
                {
                    out.write(newline);
                }
            }
            else
            {
                out.write(i);
            }
        }
        else
        {
            out.write(i);
        }
        
        lastb = i;
    }

    public void write(byte[] buf)
        throws IOException
    {
        this.write(buf, 0, buf.length);
    }

    public void write(byte buf[], int off, int len)
        throws IOException
    {
        for (int i = off; i != off + len; i++)
        {
            this.write(buf[i]);
        }
    }

    public void writeln()
        throws IOException
    {
        super.out.write(newline);
    }

    static 
    {
        newline = new byte[2];
        newline[0] = '\r';
        newline[1] = '\n';
    }
}