base64.java

用Java开发的、实现类似Visio功能的应用程序源码

                    
                    if( i == 4 )
                    {
                        numSigBytes = decode4to3( b4, 0, buffer, 0 );
                        position = 0;
                    }   // end if: got four characters
                    else if( i == 0 ){
                        return -1;
                    }   // end else if: also padded correctly
                    else
                    {
                        // Must have broken out from above.
                        throw new java.io.IOException( "Improperly padded Base64 input." );
                    }   // end 
                    
                }   // end else: decode
            }   // end else: get data
            
            // Got data?
            if( position >= 0 )
            {
                // End of relevant data?
                if( /*!encode &&*/ position >= numSigBytes )
                    return -1;
                
                if( encode && breakLines && lineLength >= MAX_LINE_LENGTH )
                {
                    lineLength = 0;
                    return '\n';
                }   // end if
                else
                {
                    lineLength++;   // This isn't important when decoding
                                    // but throwing an extra "if" seems
                                    // just as wasteful.
                    
                    int b = buffer[ position++ ];

                    if( position >= bufferLength )
                        position = -1;

                    return b & 0xFF; // This is how you "cast" a byte that's
                                     // intended to be unsigned.
                }   // end else
            }   // end if: position >= 0
            
            // Else error
            else
            {   
                // When JDK1.4 is more accepted, use an assertion here.
                throw new java.io.IOException( "Error in Base64 code reading stream." );
            }   // end else
        }   // end read
        
        
        /**
         * Calls read repeatedly until the end of stream
         * is reached or <var>len</var> bytes are read.
         * Returns number of bytes read into array or -1 if
         * end of stream is encountered.
         *
         * @param dest array to hold values
         * @param off offset for array
         * @param len max number of bytes to read into array
         * @return bytes read into array or -1 if end of stream is encountered.
         */
        public int read( byte[] dest, int off, int len ) throws java.io.IOException
        {
            int i;
            int b;
            for( i = 0; i < len; i++ )
            {
                b = read();
                
                //if( b < 0 && i == 0 )
                //    return -1;
                
                if( b >= 0 )
                    dest[off + i] = (byte)b;
                else if( i == 0 )
                    return -1;
                else
                    break; // Out of 'for' loop
            }   // end for: each byte read
            return i;
        }   // end read
        
    }   // end inner class InputStream
    
    
    
    
    
    
    /* ********  I N N E R   C L A S S   O U T P U T S T R E A M  ******** */
    
    
    
    /**
     * An OutputStream will write data to another OutputStream,
     * given in the constructor,
     * and encode/decode to/from Base64 notation on the fly.
     *
     */
    public static class OutputStream extends java.io.FilterOutputStream
    {
        private int     options;
        private boolean encode;
        private int     position;
        private byte[]  buffer;
        private int     bufferLength;
        private int     lineLength;
        private boolean breakLines;
        private byte[]  b4; // Scratch used in a few places
        private boolean suspendEncoding;
        
        /**
         * Constructs an OutputStream in ENCODE mode.
         *
         * @param out the OutputStream to which data will be written.
         */
        public OutputStream( java.io.OutputStream out )
        {   
            this( out, ENCODE );
        }   // end constructor
        
        
        /**
         * Constructs an OutputStream in
         * either ENCODE or DECODE mode.
         * <p>
         * Valid options:<pre>
         *   ENCODE or DECODE: Encode or Decode as data is read.
         *   DONT_BREAK_LINES: don't break lines at 76 characters
         *     (only meaningful when encoding)
         *     <i>Note: Technically, this makes your encoding non-compliant.</i>
         * </pre>
         * <p>
         * Example: <code>new Base64.OutputStream( out, Base64.ENCODE )</code>
         *
         * @param out the OutputStream to which data will be written.
         * @param options Specified options.
         */
        public OutputStream( java.io.OutputStream out, int options )
        {   
            super( out );
            this.options      = options;
            this.breakLines   = (options & DONT_BREAK_LINES) != DONT_BREAK_LINES;
            this.encode       = (options & ENCODE) == ENCODE;
            this.bufferLength = encode ? 3 : 4;
            this.buffer       = new byte[ bufferLength ];
            this.position     = 0;
            this.lineLength   = 0;
            this.suspendEncoding = false;
            this.b4           = new byte[4];
        }   // end constructor
        
        
        /**
         * Writes the byte to the output stream after
         * converting to/from Base64 notation.
         * When encoding, bytes are buffered three
         * at a time before the output stream actually
         * gets a write() call.
         * When decoding, bytes are buffered four
         * at a time.
         *
         * @param theByte the byte to write
         */
        public void write(int theByte) throws java.io.IOException
        {
            // Encoding suspended?
            if( suspendEncoding )
            {
                super.out.write( theByte );
                return;
            }   // end if: supsended
            
            // Encode?
            if( encode )
            {
                buffer[ position++ ] = (byte)theByte;
                if( position >= bufferLength )  // Enough to encode.
                {
                    out.write( encode3to4( b4, buffer, bufferLength ) );

                    lineLength += 4;
                    if( breakLines && lineLength >= MAX_LINE_LENGTH )
                    {
                        out.write( NEW_LINE );
                        lineLength = 0;
                    }   // end if: end of line

                    position = 0;
                }   // end if: enough to output
            }   // end if: encoding

            // Else, Decoding
            else
            {
                // Meaningful Base64 character?
                if( DECODABET[ theByte & 0x7f ] > WHITE_SPACE_ENC )
                {
                    buffer[ position++ ] = (byte)theByte;
                    if( position >= bufferLength )  // Enough to output.
                    {
                        int len = Base64.decode4to3( buffer, 0, b4, 0 );
                        out.write( b4, 0, len );
                        //out.write( Base64.decode4to3( buffer ) );
                        position = 0;
                    }   // end if: enough to output
                }   // end if: meaningful base64 character
                else if( DECODABET[ theByte & 0x7f ] != WHITE_SPACE_ENC )
                {
                    throw new java.io.IOException( "Invalid character in Base64 data." );
                }   // end else: not white space either
            }   // end else: decoding
        }   // end write
        
        
        
        /**
         * Calls write repeatedly until <var>len</var> 
         * bytes are written.
         *
         * @param theBytes array from which to read bytes
         * @param off offset for array
         * @param len max number of bytes to read into array
         */
        public void write( byte[] theBytes, int off, int len ) throws java.io.IOException
        {
            // Encoding suspended?
            if( suspendEncoding )
            {
                super.out.write( theBytes, off, len );
                return;
            }   // end if: supsended
            
            for( int i = 0; i < len; i++ )
            {
                write( theBytes[ off + i ] );
            }   // end for: each byte written
            
        }   // end write
        
        
        
        /**
         * Method added by PHIL. [Thanks, PHIL. -Rob]
         * This pads the buffer without closing the stream.
         */
        public void flushBase64() throws java.io.IOException 
        {
            if( position > 0 )
            {
                if( encode )
                {
                    out.write( encode3to4( b4, buffer, position ) );
                    position = 0;
                }   // end if: encoding
                else
                {
                    throw new java.io.IOException( "Base64 input not properly padded." );
                }   // end else: decoding
            }   // end if: buffer partially full

        }   // end flush

        
        /** 
         * Flushes and closes (I think, in the superclass) the stream. 
         *
         */
        public void close() throws java.io.IOException
        {
            // 1. Ensure that pending characters are written
            flushBase64();

            // 2. Actually close the stream
            // Base class both flushes and closes.
            super.close();
            
            buffer = null;
            out    = null;
        }   // end close
        
        
        
        /**
         * Suspends encoding of the stream.
         * May be helpful if you need to embed a piece of
         * base640-encoded data in a stream.
         *
         */
        public void suspendEncoding() throws java.io.IOException 
        {
            flushBase64();
            this.suspendEncoding = true;
        }   // end suspendEncoding
        
        
        /**
         * Resumes encoding of the stream.
         * May be helpful if you need to embed a piece of
         * base640-encoded data in a stream.
         *
         */
        public void resumeEncoding()
        {
            this.suspendEncoding = false;
        }   // end resumeEncoding
        
        
        
    }   // end inner class OutputStream
    
    
}   // end class Base64