fastbase64.java

这是一个获取文件MD5码的JAVA程序。可以用于学习JAVA

                }
            }
        }

        // form integral number of 6-bit groups
        dataIndex = i * 3;

        if (fewerThan24bits == EIGHTBIT) {
            b1 = binaryData[dataIndex];
            k = (byte) (b1 & 0x03);
            //log.debug("b1=" + b1);
            //log.debug("b1<<2 = " + (b1>>2) );
            byte val1 =
                ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
            encodedData[encodedIndex] = lookUpBase64Alphabet[val1];
            encodedData[encodedIndex + 1] = lookUpBase64Alphabet[k << 4];
            encodedData[encodedIndex + 2] = PAD;
            encodedData[encodedIndex + 3] = PAD;
        } else if (fewerThan24bits == SIXTEENBIT) {

            b1 = binaryData[dataIndex];
            b2 = binaryData[dataIndex + 1];
            l = (byte) (b2 & 0x0f);
            k = (byte) (b1 & 0x03);

            byte val1 =
                ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
            byte val2 =
                ((b2 & SIGN) == 0) ? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);

            encodedData[encodedIndex] = lookUpBase64Alphabet[val1];
            encodedData[encodedIndex + 1] =
                lookUpBase64Alphabet[val2 | (k << 4)];
            encodedData[encodedIndex + 2] = lookUpBase64Alphabet[l << 2];
            encodedData[encodedIndex + 3] = PAD;
        }

        if (isChunked) {
            // we also add a separator to the end of the final chunk.
            if (chunksSoFar < nbrChunks) {
                System.arraycopy(
                    CHUNK_SEPARATOR,
                    0,
                    encodedData,
                    encodedDataLength - CHUNK_SEPARATOR.length,
                    CHUNK_SEPARATOR.length);
            }
        }

        return encodedData;
    }

    /**
     * Decodes Base64 data into octects
     *
     * @param base64Data Byte array containing Base64 data
     * @return Array containing decoded data.
     */
    public static byte[] decodeBase64(byte[] base64Data) {
        // RFC 2045 requires that we discard ALL non-Base64 characters
        base64Data = discardNonBase64(base64Data);

        // handle the edge case, so we don't have to worry about it later
        if (base64Data.length == 0) {
            return new byte[0];
        }

        int numberQuadruple = base64Data.length / FOURBYTE;
        byte decodedData[] = null;
        byte b1 = 0, b2 = 0, b3 = 0, b4 = 0, marker0 = 0, marker1 = 0;

        // Throw away anything not in base64Data

        int encodedIndex = 0;
        int dataIndex = 0;
        {
            // this sizes the output array properly - rlw
            int lastData = base64Data.length;
            // ignore the '=' padding
            while (base64Data[lastData - 1] == PAD) {
                if (--lastData == 0) {
                    return new byte[0];
                }
            }
            decodedData = new byte[lastData - numberQuadruple];
        }
        
        for (int i = 0; i < numberQuadruple; i++) {
            dataIndex = i * 4;
            marker0 = base64Data[dataIndex + 2];
            marker1 = base64Data[dataIndex + 3];
            
            b1 = base64Alphabet[base64Data[dataIndex]];
            b2 = base64Alphabet[base64Data[dataIndex + 1]];
            
            if (marker0 != PAD && marker1 != PAD) {
                //No PAD e.g 3cQl
                b3 = base64Alphabet[marker0];
                b4 = base64Alphabet[marker1];
                
                decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
                decodedData[encodedIndex + 1] =
                    (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
                decodedData[encodedIndex + 2] = (byte) (b3 << 6 | b4);
            } else if (marker0 == PAD) {
                //Two PAD e.g. 3c[Pad][Pad]
                decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
            } else if (marker1 == PAD) {
                //One PAD e.g. 3cQ[Pad]
                b3 = base64Alphabet[marker0];
                
                decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
                decodedData[encodedIndex + 1] =
                    (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
            }
            encodedIndex += 3;
        }
        return decodedData;
    }
    
    /**
     * Decodes Base64 data into octects
     *
     * @param base64Data Byte array containing Base64 data
     * @return Array containing decoded data.
     */
    public static byte[] decodeBase64(byte[] base64Data, int pos, int length) {
        // RFC 2045 requires that we discard ALL non-Base64 characters
        base64Data = discardNonBase64(base64Data, pos, length);

        // handle the edge case, so we don't have to worry about it later
        if (base64Data.length == 0) {
            return new byte[0];
        }

        int numberQuadruple = base64Data.length / FOURBYTE;
        byte decodedData[] = null;
        byte b1 = 0, b2 = 0, b3 = 0, b4 = 0, marker0 = 0, marker1 = 0;

        // Throw away anything not in base64Data

        int encodedIndex = 0;
        int dataIndex = 0;
        {
            // this sizes the output array properly - rlw
            int lastData = base64Data.length;
            // ignore the '=' padding
            while (base64Data[lastData - 1] == PAD) {
                if (--lastData == 0) {
                    return new byte[0];
                }
            }
            decodedData = new byte[lastData - numberQuadruple];
        }
        
        for (int i = 0; i < numberQuadruple; i++) {
            dataIndex = i * 4;
            marker0 = base64Data[dataIndex + 2];
            marker1 = base64Data[dataIndex + 3];
            
            b1 = base64Alphabet[base64Data[dataIndex]];
            b2 = base64Alphabet[base64Data[dataIndex + 1]];
            
            if (marker0 != PAD && marker1 != PAD) {
                //No PAD e.g 3cQl
                b3 = base64Alphabet[marker0];
                b4 = base64Alphabet[marker1];
                
                decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
                decodedData[encodedIndex + 1] =
                    (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
                decodedData[encodedIndex + 2] = (byte) (b3 << 6 | b4);
            } else if (marker0 == PAD) {
                //Two PAD e.g. 3c[Pad][Pad]
                decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
            } else if (marker1 == PAD) {
                //One PAD e.g. 3cQ[Pad]
                b3 = base64Alphabet[marker0];
                
                decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
                decodedData[encodedIndex + 1] =
                    (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
            }
            encodedIndex += 3;
        }
        return decodedData;
    }
    
    /**
     * Discards any whitespace from a base-64 encoded block.
     *
     * @param data The base-64 encoded data to discard the whitespace
     * from.
     * @return The data, less whitespace (see RFC 2045).
     */
    static byte[] discardWhitespace(byte[] data) {
        byte groomedData[] = new byte[data.length];
        int bytesCopied = 0;
        
        for (int i = 0; i < data.length; i++) {
            switch (data[i]) {
            case (byte) ' ' :
            case (byte) '\n' :
            case (byte) '\r' :
            case (byte) '\t' :
                    break;
            default:
                    groomedData[bytesCopied++] = data[i];
            }
        }

        byte packedData[] = new byte[bytesCopied];

        System.arraycopy(groomedData, 0, packedData, 0, bytesCopied);

        return packedData;
    }

    /**
     * Discards any characters outside of the base64 alphabet, per
     * the requirements on page 25 of RFC 2045 - "Any characters
     * outside of the base64 alphabet are to be ignored in base64
     * encoded data."
     *
     * @param data The base-64 encoded data to groom
     * @return The data, less non-base64 characters (see RFC 2045).
     */
    static byte[] discardNonBase64(byte[] data) {
        byte groomedData[] = new byte[data.length];
        int bytesCopied = 0;

        for (int i = 0; i < data.length; i++) {
            if (isBase64(data[i])) {
                groomedData[bytesCopied++] = data[i];
            }
        }

        byte packedData[] = new byte[bytesCopied];

        System.arraycopy(groomedData, 0, packedData, 0, bytesCopied);

        return packedData;
    }

    static byte[] discardNonBase64(byte[] data, int pos, int length) {
        byte groomedData[] = new byte[length];
        int bytesCopied = 0;

        for (int i = pos; i < length; i++) {
            if (isBase64(data[i])) {
                groomedData[bytesCopied++] = data[i];
            }
        }

        byte packedData[] = new byte[bytesCopied];

        System.arraycopy(groomedData, 0, packedData, 0, bytesCopied);

        return packedData;
    }

    // Implementation of the Encoder Interface

    /**
     * Encodes an Object using the base64 algorithm.  This method
     * is provided in order to satisfy the requirements of the
     * Encoder interface, and will throw an EncoderException if the
     * supplied object is not of type byte[].
     *
     * @param pObject Object to encode
     * @return An object (of type byte[]) containing the 
     *         base64 encoded data which corresponds to the byte[] supplied.
     * @throws EncoderException if the parameter supplied is not
     *                          of type byte[]
     */
    public Object encode(Object pObject) throws EncoderException {
        if (!(pObject instanceof byte[])) {
            throw new EncoderException(
                "Parameter supplied to Base64 encode is not a byte[]");
        }
        return encode((byte[]) pObject);
    }

    /**
     * Encodes a byte[] containing binary data, into a byte[] containing
     * characters in the Base64 alphabet.
     *
     * @param pArray a byte array containing binary data
     * @return A byte array containing only Base64 character data
     */
    public byte[] encode(byte[] pArray) {
        return encodeBase64(pArray, false);
    }

}