java

Base64 Encoding in Android 2.1 or Earlier

by frankdu • January 27, 2011 • 3 Comments

Base64 is common used. Now Google added a utility class android.util.Base64. Unfortunately it is only available in Android 2.2 and later.

So, you need just a little bit work to use it with Android 2.1 or ealier. Yes, just copy and past the source of Base64 into your project. Make sure to preserve the Apache 2.0 license section, in order to conform to the license. The source code is provided at the end of this post, for your reference.

My disclaimer: I am not responsible for any result in doing the practice described hereby. Read the license if you need.

Now let’s see example usage:

import android.util.Base64;

public class Test {
    public static void main(String[] args) {
        String data = "this is a message by frank.";
        String encoded = Base64.encodeToString(data.getBytes(), Base64.DEFAULT);
        System.out.println("Encoded: " + encoded);

        String decoded = new String(Base64.decode(encoded, Base64.DEFAULT));
        System.out.println("Decoded: " + decoded);
    }
}

import android.util.Base64;

public class Test {

public static void main(String[] args) {

String data = "this is a message by frank.";

String encoded = Base64.encodeToString(data.getBytes(), Base64.DEFAULT);

System.out.println("Encoded: " + encoded);

String decoded = new String(Base64.decode(encoded, Base64.DEFAULT));

System.out.println("Decoded: " + decoded);

}

The output is:

Encoded: dGhpcyBpcyBhIG1lc3NhZ2UgYnkgZnJhbmsu

Decoded: this is a message by frank.

Let’s try decode the message in python:

import base64
print base64.b64decode('dGhpcyBpcyBhIG1lc3NhZ2UgYnkgZnJhbmsu')

1 2	import base64 print base64.b64decode('dGhpcyBpcyBhIG1lc3NhZ2UgYnkgZnJhbmsu')

You will get the same input message htere. Now you are ready to send your data to anywhere, like app engine, you know!

The android.util.Base64 source

package android.util;
/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */



import java.io.UnsupportedEncodingException;

/**
 * Utilities for encoding and decoding the Base64 representation of
 * binary data.  See RFCs <a
 * href="http://www.ietf.org/rfc/rfc2045.txt">2045</a> and <a
 * href="http://www.ietf.org/rfc/rfc3548.txt">3548</a>.
 */
public class Base64 {
    /**
     * Default values for encoder/decoder flags.
     */
    public static final int DEFAULT = 0;

    /**
     * Encoder flag bit to omit the padding '=' characters at the end
     * of the output (if any).
     */
    public static final int NO_PADDING = 1;

    /**
     * Encoder flag bit to omit all line terminators (i.e., the output
     * will be on one long line).
     */
    public static final int NO_WRAP = 2;

    /**
     * Encoder flag bit to indicate lines should be terminated with a
     * CRLF pair instead of just an LF.  Has no effect if {@code
     * NO_WRAP} is specified as well.
     */
    public static final int CRLF = 4;

    /**
     * Encoder/decoder flag bit to indicate using the "URL and
     * filename safe" variant of Base64 (see RFC 3548 section 4) where
     * {@code -} and {@code _} are used in place of {@code +} and
     * {@code /}.
     */
    public static final int URL_SAFE = 8;

    /**
     * Flag to pass to {@link Base64OutputStream} to indicate that it
     * should not close the output stream it is wrapping when it
     * itself is closed.
     */
    public static final int NO_CLOSE = 16;

    //  --------------------------------------------------------
    //  shared code
    //  --------------------------------------------------------

    /* package */ static abstract class Coder {
        public byte[] output;
        public int op;

        /**
         * Encode/decode another block of input data.  this.output is
         * provided by the caller, and must be big enough to hold all
         * the coded data.  On exit, this.opwill be set to the length
         * of the coded data.
         *
         * @param finish true if this is the final call to process for
         *        this object.  Will finalize the coder state and
         *        include any final bytes in the output.
         *
         * @return true if the input so far is good; false if some
         *         error has been detected in the input stream..
         */
        public abstract boolean process(byte[] input, int offset, int len, boolean finish);

        /**
         * @return the maximum number of bytes a call to process()
         * could produce for the given number of input bytes.  This may
         * be an overestimate.
         */
        public abstract int maxOutputSize(int len);
    }

    //  --------------------------------------------------------
    //  decoding
    //  --------------------------------------------------------

    /**
     * Decode the Base64-encoded data in input and return the data in
     * a new byte array.
     *
     * <p>The padding '=' characters at the end are considered optional, but
     * if any are present, there must be the correct number of them.
     *
     * @param str    the input String to decode, which is converted to
     *               bytes using the default charset
     * @param flags  controls certain features of the decoded output.
     *               Pass {@code DEFAULT} to decode standard Base64.
     *
     * @throws IllegalArgumentException if the input contains
     * incorrect padding
     */
    public static byte[] decode(String str, int flags) {
        return decode(str.getBytes(), flags);
    }

    /**
     * Decode the Base64-encoded data in input and return the data in
     * a new byte array.
     *
     * <p>The padding '=' characters at the end are considered optional, but
     * if any are present, there must be the correct number of them.
     *
     * @param input the input array to decode
     * @param flags  controls certain features of the decoded output.
     *               Pass {@code DEFAULT} to decode standard Base64.
     *
     * @throws IllegalArgumentException if the input contains
     * incorrect padding
     */
    public static byte[] decode(byte[] input, int flags) {
        return decode(input, 0, input.length, flags);
    }

    /**
     * Decode the Base64-encoded data in input and return the data in
     * a new byte array.
     *
     * <p>The padding '=' characters at the end are considered optional, but
     * if any are present, there must be the correct number of them.
     *
     * @param input  the data to decode
     * @param offset the position within the input array at which to start
     * @param len    the number of bytes of input to decode
     * @param flags  controls certain features of the decoded output.
     *               Pass {@code DEFAULT} to decode standard Base64.
     *
     * @throws IllegalArgumentException if the input contains
     * incorrect padding
     */
    public static byte[] decode(byte[] input, int offset, int len, int flags) {
        // Allocate space for the most data the input could represent.
        // (It could contain less if it contains whitespace, etc.)
        Decoder decoder = new Decoder(flags, new byte[len*3/4]);

        if (!decoder.process(input, offset, len, true)) {
            throw new IllegalArgumentException("bad base-64");
        }

        // Maybe we got lucky and allocated exactly enough output space.
        if (decoder.op == decoder.output.length) {
            return decoder.output;
        }

        // Need to shorten the array, so allocate a new one of the
        // right size and copy.
        byte[] temp = new byte[decoder.op];
        System.arraycopy(decoder.output, 0, temp, 0, decoder.op);
        return temp;
    }

    /* package */ static class Decoder extends Coder {
        /**
         * Lookup table for turning bytes into their position in the
         * Base64 alphabet.
         */
        private static final int DECODE[] = {
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
            52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1,
            -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
            15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
            -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
            41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        };

        /**
         * Decode lookup table for the "web safe" variant (RFC 3548
         * sec. 4) where - and _ replace + and /.
         */
        private static final int DECODE_WEBSAFE[] = {
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1,
            52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1,
            -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
            15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, 63,
            -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
            41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        };

        /** Non-data values in the DECODE arrays. */
        private static final int SKIP = -1;
        private static final int EQUALS = -2;

        /**
         * States 0-3 are reading through the next input tuple.
         * State 4 is having read one '=' and expecting exactly
         * one more.
         * State 5 is expecting no more data or padding characters
         * in the input.
         * State 6 is the error state; an error has been detected
         * in the input and no future input can "fix" it.
         */
        private int state;   // state number (0 to 6)
        private int value;

        final private int[] alphabet;

        public Decoder(int flags, byte[] output) {
            this.output = output;

            alphabet = ((flags & URL_SAFE) == 0) ? DECODE : DECODE_WEBSAFE;
            state = 0;
            value = 0;
        }

        /**
         * @return an overestimate for the number of bytes {@code
         * len} bytes could decode to.
         */
        public int maxOutputSize(int len) {
            return len * 3/4 + 10;
        }

        /**
         * Decode another block of input data.
         *
         * @return true if the state machine is still healthy.  false if
         *         bad base-64 data has been detected in the input stream.
         */
        public boolean process(byte[] input, int offset, int len, boolean finish) {
            if (this.state == 6) return false;

            int p = offset;
            len += offset;

            // Using local variables makes the decoder about 12%
            // faster than if we manipulate the member variables in
            // the loop.  (Even alphabet makes a measurable
            // difference, which is somewhat surprising to me since
            // the member variable is final.)
            int state = this.state;
            int value = this.value;
            int op = 0;
            final byte[] output = this.output;
            final int[] alphabet = this.alphabet;

            while (p < len) {
                // Try the fast path:  we're starting a new tuple and the
                // next four bytes of the input stream are all data
                // bytes.  This corresponds to going through states
                // 0-1-2-3-0.  We expect to use this method for most of
                // the data.
                //
                // If any of the next four bytes of input are non-data
                // (whitespace, etc.), value will end up negative.  (All
                // the non-data values in decode are small negative
                // numbers, so shifting any of them up and or'ing them
                // together will result in a value with its top bit set.)
                //
                // You can remove this whole block and the output should
                // be the same, just slower.
                if (state == 0) {
                    while (p+4 <= len &&
                           (value = ((alphabet[input[p] & 0xff] << 18) |
                                     (alphabet[input[p+1] & 0xff] << 12) |
                                     (alphabet[input[p+2] & 0xff] << 6) |
                                     (alphabet[input[p+3] & 0xff]))) >= 0) {
                        output[op+2] = (byte) value;
                        output[op+1] = (byte) (value >> 8);
                        output[op] = (byte) (value >> 16);
                        op += 3;
                        p += 4;
                    }
                    if (p >= len) break;
                }

                // The fast path isn't available -- either we've read a
                // partial tuple, or the next four input bytes aren't all
                // data, or whatever.  Fall back to the slower state
                // machine implementation.

                int d = alphabet[input[p++] & 0xff];

                switch (state) {
                case 0:
                    if (d >= 0) {
                        value = d;
                        ++state;
                    } else if (d != SKIP) {
                        this.state = 6;
                        return false;
                    }
                    break;

                case 1:
                    if (d >= 0) {
                        value = (value << 6) | d;
                        ++state;
                    } else if (d != SKIP) {
                        this.state = 6;
                        return false;
                    }
                    break;

                case 2:
                    if (d >= 0) {
                        value = (value << 6) | d;
                        ++state;
                    } else if (d == EQUALS) {
                        // Emit the last (partial) output tuple;
                        // expect exactly one more padding character.
                        output[op++] = (byte) (value >> 4);
                        state = 4;
                    } else if (d != SKIP) {
                        this.state = 6;
                        return false;
                    }
                    break;

                case 3:
                    if (d >= 0) {
                        // Emit the output triple and return to state 0.
                        value = (value << 6) | d;
                        output[op+2] = (byte) value;
                        output[op+1] = (byte) (value >> 8);
                        output[op] = (byte) (value >> 16);
                        op += 3;
                        state = 0;
                    } else if (d == EQUALS) {
                        // Emit the last (partial) output tuple;
                        // expect no further data or padding characters.
                        output[op+1] = (byte) (value >> 2);
                        output[op] = (byte) (value >> 10);
                        op += 2;
                        state = 5;
                    } else if (d != SKIP) {
                        this.state = 6;
                        return false;
                    }
                    break;

                case 4:
                    if (d == EQUALS) {
                        ++state;
                    } else if (d != SKIP) {
                        this.state = 6;
                        return false;
                    }
                    break;

                case 5:
                    if (d != SKIP) {
                        this.state = 6;
                        return false;
                    }
                    break;
                }
            }

            if (!finish) {
                // We're out of input, but a future call could provide
                // more.
                this.state = state;
                this.value = value;
                this.op = op;
                return true;
            }

            // Done reading input.  Now figure out where we are left in
            // the state machine and finish up.

            switch (state) {
            case 0:
                // Output length is a multiple of three.  Fine.
                break;
            case 1:
                // Read one extra input byte, which isn't enough to
                // make another output byte.  Illegal.
                this.state = 6;
                return false;
            case 2:
                // Read two extra input bytes, enough to emit 1 more
                // output byte.  Fine.
                output[op++] = (byte) (value >> 4);
                break;
            case 3:
                // Read three extra input bytes, enough to emit 2 more
                // output bytes.  Fine.
                output[op++] = (byte) (value >> 10);
                output[op++] = (byte) (value >> 2);
                break;
            case 4:
                // Read one padding '=' when we expected 2.  Illegal.
                this.state = 6;
                return false;
            case 5:
                // Read all the padding '='s we expected and no more.
                // Fine.
                break;
            }

            this.state = state;
            this.op = op;
            return true;
        }
    }

    //  --------------------------------------------------------
    //  encoding
    //  --------------------------------------------------------

    /**
     * Base64-encode the given data and return a newly allocated
     * String with the result.
     *
     * @param input  the data to encode
     * @param flags  controls certain features of the encoded output.
     *               Passing {@code DEFAULT} results in output that
     *               adheres to RFC 2045.
     */
    public static String encodeToString(byte[] input, int flags) {
        try {
            return new String(encode(input, flags), "US-ASCII");
        } catch (UnsupportedEncodingException e) {
            // US-ASCII is guaranteed to be available.
            throw new AssertionError(e);
        }
    }

    /**
     * Base64-encode the given data and return a newly allocated
     * String with the result.
     *
     * @param input  the data to encode
     * @param offset the position within the input array at which to
     *               start
     * @param len    the number of bytes of input to encode
     * @param flags  controls certain features of the encoded output.
     *               Passing {@code DEFAULT} results in output that
     *               adheres to RFC 2045.
     */
    public static String encodeToString(byte[] input, int offset, int len, int flags) {
        try {
            return new String(encode(input, offset, len, flags), "US-ASCII");
        } catch (UnsupportedEncodingException e) {
            // US-ASCII is guaranteed to be available.
            throw new AssertionError(e);
        }
    }

    /**
     * Base64-encode the given data and return a newly allocated
     * byte[] with the result.
     *
     * @param input  the data to encode
     * @param flags  controls certain features of the encoded output.
     *               Passing {@code DEFAULT} results in output that
     *               adheres to RFC 2045.
     */
    public static byte[] encode(byte[] input, int flags) {
        return encode(input, 0, input.length, flags);
    }

    /**
     * Base64-encode the given data and return a newly allocated
     * byte[] with the result.
     *
     * @param input  the data to encode
     * @param offset the position within the input array at which to
     *               start
     * @param len    the number of bytes of input to encode
     * @param flags  controls certain features of the encoded output.
     *               Passing {@code DEFAULT} results in output that
     *               adheres to RFC 2045.
     */
    public static byte[] encode(byte[] input, int offset, int len, int flags) {
        Encoder encoder = new Encoder(flags, null);

        // Compute the exact length of the array we will produce.
        int output_len = len / 3 * 4;

        // Account for the tail of the data and the padding bytes, if any.
        if (encoder.do_padding) {
            if (len % 3 > 0) {
                output_len += 4;
            }
        } else {
            switch (len % 3) {
                case 0: break;
                case 1: output_len += 2; break;
                case 2: output_len += 3; break;
            }
        }

        // Account for the newlines, if any.
        if (encoder.do_newline && len > 0) {
            output_len += (((len-1) / (3 * Encoder.LINE_GROUPS)) + 1) *
                (encoder.do_cr ? 2 : 1);
        }

        encoder.output = new byte[output_len];
        encoder.process(input, offset, len, true);

        assert encoder.op == output_len;

        return encoder.output;
    }

    /* package */ static class Encoder extends Coder {
        /**
         * Emit a new line every this many output tuples.  Corresponds to
         * a 76-character line length (the maximum allowable according to
         * <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045</a>).
         */
        public static final int LINE_GROUPS = 19;

        /**
         * Lookup table for turning Base64 alphabet positions (6 bits)
         * into output bytes.
         */
        private static final byte ENCODE[] = {
            'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
            'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
            'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
            'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/',
        };

        /**
         * Lookup table for turning Base64 alphabet positions (6 bits)
         * into output bytes.
         */
        private static final byte ENCODE_WEBSAFE[] = {
            'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
            'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
            'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
            'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '-', '_',
        };

        final private byte[] tail;
        /* package */ int tailLen;
        private int count;

        final public boolean do_padding;
        final public boolean do_newline;
        final public boolean do_cr;
        final private byte[] alphabet;

        public Encoder(int flags, byte[] output) {
            this.output = output;

            do_padding = (flags & NO_PADDING) == 0;
            do_newline = (flags & NO_WRAP) == 0;
            do_cr = (flags & CRLF) != 0;
            alphabet = ((flags & URL_SAFE) == 0) ? ENCODE : ENCODE_WEBSAFE;

            tail = new byte[2];
            tailLen = 0;

            count = do_newline ? LINE_GROUPS : -1;
        }

        /**
         * @return an overestimate for the number of bytes {@code
         * len} bytes could encode to.
         */
        public int maxOutputSize(int len) {
            return len * 8/5 + 10;
        }

        public boolean process(byte[] input, int offset, int len, boolean finish) {
            // Using local variables makes the encoder about 9% faster.
            final byte[] alphabet = this.alphabet;
            final byte[] output = this.output;
            int op = 0;
            int count = this.count;

            int p = offset;
            len += offset;
            int v = -1;

            // First we need to concatenate the tail of the previous call
            // with any input bytes available now and see if we can empty
            // the tail.

            switch (tailLen) {
                case 0:
                    // There was no tail.
                    break;

                case 1:
                    if (p+2 <= len) {
                        // A 1-byte tail with at least 2 bytes of
                        // input available now.
                        v = ((tail[0] & 0xff) << 16) |
                            ((input[p++] & 0xff) << 8) |
                            (input[p++] & 0xff);
                        tailLen = 0;
                    };
                    break;

                case 2:
                    if (p+1 <= len) {
                        // A 2-byte tail with at least 1 byte of input.
                        v = ((tail[0] & 0xff) << 16) |
                            ((tail[1] & 0xff) << 8) |
                            (input[p++] & 0xff);
                        tailLen = 0;
                    }
                    break;
            }

            if (v != -1) {
                output[op++] = alphabet[(v >> 18) & 0x3f];
                output[op++] = alphabet[(v >> 12) & 0x3f];
                output[op++] = alphabet[(v >> 6) & 0x3f];
                output[op++] = alphabet[v & 0x3f];
                if (--count == 0) {
                    if (do_cr) output[op++] = 'r';
                    output[op++] = 'n';
                    count = LINE_GROUPS;
                }
            }

            // At this point either there is no tail, or there are fewer
            // than 3 bytes of input available.

            // The main loop, turning 3 input bytes into 4 output bytes on
            // each iteration.
            while (p+3 <= len) {
                v = ((input[p] & 0xff) << 16) |
                    ((input[p+1] & 0xff) << 8) |
                    (input[p+2] & 0xff);
                output[op] = alphabet[(v >> 18) & 0x3f];
                output[op+1] = alphabet[(v >> 12) & 0x3f];
                output[op+2] = alphabet[(v >> 6) & 0x3f];
                output[op+3] = alphabet[v & 0x3f];
                p += 3;
                op += 4;
                if (--count == 0) {
                    if (do_cr) output[op++] = 'r';
                    output[op++] = 'n';
                    count = LINE_GROUPS;
                }
            }

            if (finish) {
                // Finish up the tail of the input.  Note that we need to
                // consume any bytes in tail before any bytes
                // remaining in input; there should be at most two bytes
                // total.

                if (p-tailLen == len-1) {
                    int t = 0;
                    v = ((tailLen > 0 ? tail[t++] : input[p++]) & 0xff) << 4;
                    tailLen -= t;
                    output[op++] = alphabet[(v >> 6) & 0x3f];
                    output[op++] = alphabet[v & 0x3f];
                    if (do_padding) {
                        output[op++] = '=';
                        output[op++] = '=';
                    }
                    if (do_newline) {
                        if (do_cr) output[op++] = 'r';
                        output[op++] = 'n';
                    }
                } else if (p-tailLen == len-2) {
                    int t = 0;
                    v = (((tailLen > 1 ? tail[t++] : input[p++]) & 0xff) << 10) |
                        (((tailLen > 0 ? tail[t++] : input[p++]) & 0xff) << 2);
                    tailLen -= t;
                    output[op++] = alphabet[(v >> 12) & 0x3f];
                    output[op++] = alphabet[(v >> 6) & 0x3f];
                    output[op++] = alphabet[v & 0x3f];
                    if (do_padding) {
                        output[op++] = '=';
                    }
                    if (do_newline) {
                        if (do_cr) output[op++] = 'r';
                        output[op++] = 'n';
                    }
                } else if (do_newline && op > 0 && count != LINE_GROUPS) {
                    if (do_cr) output[op++] = 'r';
                    output[op++] = 'n';
                }

                assert tailLen == 0;
                assert p == len;
            } else {
                // Save the leftovers in tail to be consumed on the next
                // call to encodeInternal.

                if (p == len-1) {
                    tail[tailLen++] = input[p];
                } else if (p == len-2) {
                    tail[tailLen++] = input[p];
                    tail[tailLen++] = input[p+1];
                }
            }

            this.op = op;
            this.count = count;

            return true;
        }
    }

    private Base64() { }   // don't instantiate
}

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package android.util;

* Licensed under the Apache License, Version 2.0 (the "License");

* you may not use this file except in compliance with the License.

* You may obtain a copy of the License at

* http://www.apache.org/licenses/LICENSE-2.0

* Unless required by applicable law or agreed to in writing, software

* distributed under the License is distributed on an "AS IS" BASIS,

* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

* See the License for the specific language governing permissions and

* limitations under the License.

import java.io.UnsupportedEncodingException;

/**

* Utilities for encoding and decoding the Base64 representation of

* binary data. See RFCs <a

* href="http://www.ietf.org/rfc/rfc2045.txt">2045</a> and <a

* href="http://www.ietf.org/rfc/rfc3548.txt">3548</a>.

public class Base64 {

/**

* Default values for encoder/decoder flags.

public static final int DEFAULT = 0;

/**

* Encoder flag bit to omit the padding '=' characters at the end

* of the output (if any).

public static final int NO_PADDING = 1;

/**

* Encoder flag bit to omit all line terminators (i.e., the output

* will be on one long line).

public static final int NO_WRAP = 2;

/**

* Encoder flag bit to indicate lines should be terminated with a

* CRLF pair instead of just an LF. Has no effect if {@code

* NO_WRAP} is specified as well.

public static final int CRLF = 4;

/**

* Encoder/decoder flag bit to indicate using the "URL and

* filename safe" variant of Base64 (see RFC 3548 section 4) where

* {@code -} and {@code _} are used in place of {@code +} and

* {@code /}.

public static final int URL_SAFE = 8;

/**

* Flag to pass to {@link Base64OutputStream} to indicate that it

* should not close the output stream it is wrapping when it

* itself is closed.

public static final int NO_CLOSE = 16;

// --------------------------------------------------------

// shared code

// --------------------------------------------------------

/* package */ static abstract class Coder {

public byte[] output;

public int op;

/**

* Encode/decode another block of input data. this.output is

* provided by the caller, and must be big enough to hold all

* the coded data. On exit, this.opwill be set to the length

* of the coded data.

* @param finish true if this is the final call to process for

* this object. Will finalize the coder state and

* include any final bytes in the output.

* @return true if the input so far is good; false if some

* error has been detected in the input stream..

public abstract boolean process(byte[] input, int offset, int len, boolean finish);

/**

* @return the maximum number of bytes a call to process()

* could produce for the given number of input bytes. This may

* be an overestimate.

public abstract int maxOutputSize(int len);

}

// --------------------------------------------------------

// decoding

// --------------------------------------------------------

/**

* Decode the Base64-encoded data in input and return the data in

* a new byte array.

* <p>The padding '=' characters at the end are considered optional, but

* if any are present, there must be the correct number of them.

* @param str the input String to decode, which is converted to

* bytes using the default charset

* @param flags controls certain features of the decoded output.

* Pass {@code DEFAULT} to decode standard Base64.

* @throws IllegalArgumentException if the input contains

* incorrect padding

public static byte[] decode(String str, int flags) {

return decode(str.getBytes(), flags);

}

/**

* Decode the Base64-encoded data in input and return the data in

* a new byte array.

* <p>The padding '=' characters at the end are considered optional, but

* if any are present, there must be the correct number of them.

* @param input the input array to decode

* @param flags controls certain features of the decoded output.

* Pass {@code DEFAULT} to decode standard Base64.

* @throws IllegalArgumentException if the input contains

* incorrect padding

public static byte[] decode(byte[] input, int flags) {

return decode(input, 0, input.length, flags);

}

/**

* Decode the Base64-encoded data in input and return the data in

* a new byte array.

* <p>The padding '=' characters at the end are considered optional, but

* if any are present, there must be the correct number of them.

* @param input the data to decode

* @param offset the position within the input array at which to start

* @param len the number of bytes of input to decode

* @param flags controls certain features of the decoded output.

* Pass {@code DEFAULT} to decode standard Base64.

* @throws IllegalArgumentException if the input contains

* incorrect padding

public static byte[] decode(byte[] input, int offset, int len, int flags) {

// Allocate space for the most data the input could represent.

// (It could contain less if it contains whitespace, etc.)

Decoder decoder = new Decoder(flags, new byte[len*3/4]);

if (!decoder.process(input, offset, len, true)) {

throw new IllegalArgumentException("bad base-64");

}

// Maybe we got lucky and allocated exactly enough output space.

if (decoder.op == decoder.output.length) {

return decoder.output;

}

// Need to shorten the array, so allocate a new one of the

// right size and copy.

byte[] temp = new byte[decoder.op];

System.arraycopy(decoder.output, 0, temp, 0, decoder.op);

return temp;

}

/* package */ static class Decoder extends Coder {

/**

* Lookup table for turning bytes into their position in the

* Base64 alphabet.

private static final int DECODE[] = {

-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,

-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,

52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1,

-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,

15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,

-1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,

41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1,

-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,

};

/**

* Decode lookup table for the "web safe" variant (RFC 3548

* sec. 4) where - and _ replace + and /.

private static final int DECODE_WEBSAFE[] = {

-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,

-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1,

52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1,

-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,

15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, 63,

-1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,

41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1,

-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,

};

/** Non-data values in the DECODE arrays. */

private static final int SKIP = -1;

private static final int EQUALS = -2;

/**

* States 0-3 are reading through the next input tuple.

* State 4 is having read one '=' and expecting exactly

* one more.

* State 5 is expecting no more data or padding characters

* in the input.

* State 6 is the error state; an error has been detected

* in the input and no future input can "fix" it.

private int state; // state number (0 to 6)

private int value;

final private int[] alphabet;

public Decoder(int flags, byte[] output) {

this.output = output;

alphabet = ((flags & URL_SAFE) == 0) ? DECODE : DECODE_WEBSAFE;

state = 0;

value = 0;

}

/**

* @return an overestimate for the number of bytes {@code

* len} bytes could decode to.

public int maxOutputSize(int len) {

return len * 3/4 + 10;

}

/**

* Decode another block of input data.

* @return true if the state machine is still healthy. false if

* bad base-64 data has been detected in the input stream.

public boolean process(byte[] input, int offset, int len, boolean finish) {

if (this.state == 6) return false;

int p = offset;

len += offset;

// Using local variables makes the decoder about 12%

// faster than if we manipulate the member variables in

// the loop. (Even alphabet makes a measurable

// difference, which is somewhat surprising to me since

// the member variable is final.)

int state = this.state;

int value = this.value;

int op = 0;

final byte[] output = this.output;

final int[] alphabet = this.alphabet;

while (p < len) {

// Try the fast path: we're starting a new tuple and the

// next four bytes of the input stream are all data

// bytes. This corresponds to going through states

// 0-1-2-3-0. We expect to use this method for most of

// the data.

// If any of the next four bytes of input are non-data

// (whitespace, etc.), value will end up negative. (All

// the non-data values in decode are small negative

// numbers, so shifting any of them up and or'ing them

// together will result in a value with its top bit set.)

// You can remove this whole block and the output should

// be the same, just slower.

if (state == 0) {

while (p+4 <= len &&

(value = ((alphabet[input[p] & 0xff] << 18) |

(alphabet[input[p+1] & 0xff] << 12) |

(alphabet[input[p+2] & 0xff] << 6) |

(alphabet[input[p+3] & 0xff]))) >= 0) {

output[op+2] = (byte) value;

output[op+1] = (byte) (value >> 8);

output[op] = (byte) (value >> 16);

op += 3;

p += 4;

}

if (p >= len) break;

}

// The fast path isn't available -- either we've read a

// partial tuple, or the next four input bytes aren't all

// data, or whatever. Fall back to the slower state

// machine implementation.

int d = alphabet[input[p++] & 0xff];

switch (state) {

case 0:

if (d >= 0) {

value = d;

++state;

} else if (d != SKIP) {

this.state = 6;

return false;

}

break;

case 1:

if (d >= 0) {

value = (value << 6) | d;

++state;

} else if (d != SKIP) {

this.state = 6;

return false;

}

break;

case 2:

if (d >= 0) {

value = (value << 6) | d;

++state;

} else if (d == EQUALS) {

// Emit the last (partial) output tuple;

// expect exactly one more padding character.

output[op++] = (byte) (value >> 4);

state = 4;

} else if (d != SKIP) {

this.state = 6;

return false;

}

break;

case 3:

if (d >= 0) {

// Emit the output triple and return to state 0.

value = (value << 6) | d;

output[op+2] = (byte) value;

output[op+1] = (byte) (value >> 8);

output[op] = (byte) (value >> 16);

op += 3;

state = 0;

} else if (d == EQUALS) {

// Emit the last (partial) output tuple;

// expect no further data or padding characters.

output[op+1] = (byte) (value >> 2);

output[op] = (byte) (value >> 10);

op += 2;

state = 5;

} else if (d != SKIP) {

this.state = 6;

return false;

}

break;

case 4:

if (d == EQUALS) {

++state;

} else if (d != SKIP) {

this.state = 6;

return false;

}

break;

case 5:

if (d != SKIP) {

this.state = 6;

return false;

}

break;

}

if (!finish) {

// We're out of input, but a future call could provide

// more.

this.state = state;

this.value = value;

this.op = op;

return true;

}

// Done reading input. Now figure out where we are left in

// the state machine and finish up.

switch (state) {

case 0:

// Output length is a multiple of three. Fine.

break;

case 1:

// Read one extra input byte, which isn't enough to

// make another output byte. Illegal.

this.state = 6;

return false;

case 2:

// Read two extra input bytes, enough to emit 1 more

// output byte. Fine.

output[op++] = (byte) (value >> 4);

break;

case 3:

// Read three extra input bytes, enough to emit 2 more

// output bytes. Fine.

output[op++] = (byte) (value >> 10);

output[op++] = (byte) (value >> 2);

break;

case 4:

// Read one padding '=' when we expected 2. Illegal.

this.state = 6;

return false;

case 5:

// Read all the padding '='s we expected and no more.

// Fine.

break;

}

this.state = state;

this.op = op;

return true;

}

// --------------------------------------------------------

// encoding

// --------------------------------------------------------

/**

* Base64-encode the given data and return a newly allocated

* String with the result.

* @param input the data to encode

* @param flags controls certain features of the encoded output.

* Passing {@code DEFAULT} results in output that

* adheres to RFC 2045.

public static String encodeToString(byte[] input, int flags) {

try {

return new String(encode(input, flags), "US-ASCII");

} catch (UnsupportedEncodingException e) {

// US-ASCII is guaranteed to be available.

throw new AssertionError(e);

}

/**

* Base64-encode the given data and return a newly allocated

* String with the result.

* @param input the data to encode

* @param offset the position within the input array at which to

* start

* @param len the number of bytes of input to encode

* @param flags controls certain features of the encoded output.

* Passing {@code DEFAULT} results in output that

* adheres to RFC 2045.

public static String encodeToString(byte[] input, int offset, int len, int flags) {

try {

return new String(encode(input, offset, len, flags), "US-ASCII");

} catch (UnsupportedEncodingException e) {

// US-ASCII is guaranteed to be available.

throw new AssertionError(e);

}

/**

* Base64-encode the given data and return a newly allocated

* byte[] with the result.

* @param input the data to encode

* @param flags controls certain features of the encoded output.

* Passing {@code DEFAULT} results in output that

* adheres to RFC 2045.

public static byte[] encode(byte[] input, int flags) {

return encode(input, 0, input.length, flags);

}

/**

* Base64-encode the given data and return a newly allocated

* byte[] with the result.

* @param input the data to encode

* @param offset the position within the input array at which to

* start

* @param len the number of bytes of input to encode

* @param flags controls certain features of the encoded output.

* Passing {@code DEFAULT} results in output that

* adheres to RFC 2045.

public static byte[] encode(byte[] input, int offset, int len, int flags) {

Encoder encoder = new Encoder(flags, null);

// Compute the exact length of the array we will produce.

int output_len = len / 3 * 4;

// Account for the tail of the data and the padding bytes, if any.

if (encoder.do_padding) {

if (len % 3 > 0) {

output_len += 4;

}

} else {

switch (len % 3) {

case 0: break;

case 1: output_len += 2; break;

case 2: output_len += 3; break;

}

// Account for the newlines, if any.

if (encoder.do_newline && len > 0) {

output_len += (((len-1) / (3 * Encoder.LINE_GROUPS)) + 1) *

(encoder.do_cr ? 2 : 1);

}

encoder.output = new byte[output_len];

encoder.process(input, offset, len, true);

assert encoder.op == output_len;

return encoder.output;

}

/* package */ static class Encoder extends Coder {

/**

* Emit a new line every this many output tuples. Corresponds to

* a 76-character line length (the maximum allowable according to

* <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045</a>).

public static final int LINE_GROUPS = 19;

/**

* Lookup table for turning Base64 alphabet positions (6 bits)

* into output bytes.

private static final byte ENCODE[] = {

'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',

'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',

'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v',

'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/',

};

/**

* Lookup table for turning Base64 alphabet positions (6 bits)

* into output bytes.

private static final byte ENCODE_WEBSAFE[] = {

'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',

'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',

'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v',

'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '-', '_',

};

final private byte[] tail;

/* package */ int tailLen;

private int count;

final public boolean do_padding;

final public boolean do_newline;

final public boolean do_cr;

final private byte[] alphabet;

public Encoder(int flags, byte[] output) {

this.output = output;

do_padding = (flags & NO_PADDING) == 0;

do_newline = (flags & NO_WRAP) == 0;

do_cr = (flags & CRLF) != 0;

alphabet = ((flags & URL_SAFE) == 0) ? ENCODE : ENCODE_WEBSAFE;

tail = new byte[2];

tailLen = 0;

count = do_newline ? LINE_GROUPS : -1;

}

/**

* @return an overestimate for the number of bytes {@code

* len} bytes could encode to.

public int maxOutputSize(int len) {

return len * 8/5 + 10;

}

public boolean process(byte[] input, int offset, int len, boolean finish) {

// Using local variables makes the encoder about 9% faster.

final byte[] alphabet = this.alphabet;

final byte[] output = this.output;

int op = 0;

int count = this.count;

int p = offset;

len += offset;

int v = -1;

// First we need to concatenate the tail of the previous call

// with any input bytes available now and see if we can empty

// the tail.

switch (tailLen) {

case 0:

// There was no tail.

break;

case 1:

if (p+2 <= len) {

// A 1-byte tail with at least 2 bytes of

// input available now.

v = ((tail[0] & 0xff) << 16) |

((input[p++] & 0xff) << 8) |

(input[p++] & 0xff);

tailLen = 0;

};

break;

case 2:

if (p+1 <= len) {

// A 2-byte tail with at least 1 byte of input.

v = ((tail[0] & 0xff) << 16) |

((tail[1] & 0xff) << 8) |

(input[p++] & 0xff);

tailLen = 0;

}

break;

}

if (v != -1) {

output[op++] = alphabet[(v >> 18) & 0x3f];

output[op++] = alphabet[(v >> 12) & 0x3f];

output[op++] = alphabet[(v >> 6) & 0x3f];

output[op++] = alphabet[v & 0x3f];

if (--count == 0) {

if (do_cr) output[op++] = 'r';

output[op++] = 'n';

count = LINE_GROUPS;

}

// At this point either there is no tail, or there are fewer

// than 3 bytes of input available.

// The main loop, turning 3 input bytes into 4 output bytes on

// each iteration.

while (p+3 <= len) {

v = ((input[p] & 0xff) << 16) |

((input[p+1] & 0xff) << 8) |

(input[p+2] & 0xff);

output[op] = alphabet[(v >> 18) & 0x3f];

output[op+1] = alphabet[(v >> 12) & 0x3f];

output[op+2] = alphabet[(v >> 6) & 0x3f];

output[op+3] = alphabet[v & 0x3f];

p += 3;

op += 4;

if (--count == 0) {

if (do_cr) output[op++] = 'r';

output[op++] = 'n';

count = LINE_GROUPS;

}

if (finish) {

// Finish up the tail of the input. Note that we need to

// consume any bytes in tail before any bytes

// remaining in input; there should be at most two bytes

// total.

if (p-tailLen == len-1) {

int t = 0;

v = ((tailLen > 0 ? tail[t++] : input[p++]) & 0xff) << 4;

tailLen -= t;

output[op++] = alphabet[(v >> 6) & 0x3f];

output[op++] = alphabet[v & 0x3f];

if (do_padding) {

output[op++] = '=';

}

if (do_newline) {

if (do_cr) output[op++] = 'r';

output[op++] = 'n';

}

} else if (p-tailLen == len-2) {

int t = 0;

v = (((tailLen > 1 ? tail[t++] : input[p++]) & 0xff) << 10) |

(((tailLen > 0 ? tail[t++] : input[p++]) & 0xff) << 2);

tailLen -= t;

output[op++] = alphabet[(v >> 12) & 0x3f];

output[op++] = alphabet[(v >> 6) & 0x3f];

output[op++] = alphabet[v & 0x3f];

if (do_padding) {

output[op++] = '=';

}

if (do_newline) {

if (do_cr) output[op++] = 'r';

output[op++] = 'n';

}

} else if (do_newline && op > 0 && count != LINE_GROUPS) {

if (do_cr) output[op++] = 'r';

output[op++] = 'n';

}

assert tailLen == 0;

assert p == len;

} else {

// Save the leftovers in tail to be consumed on the next

// call to encodeInternal.

if (p == len-1) {

tail[tailLen++] = input[p];

} else if (p == len-2) {

tail[tailLen++] = input[p];

tail[tailLen++] = input[p+1];

}

this.op = op;

this.count = count;

return true;

}

private Base64() { } // don't instantiate

}

A simple thrift tutorial

by frankdu • April 7, 2010 • 0 Comments

Check it out at http://skorage.org/2009/03/08/simple-thrift-tutorial/

Set the source level to Java 6 for maven 2 compiler

by frankdu • January 10, 2010 • 0 Comments

By default, the source level is 1.3 in maven 2. We need to config maven compiler to use Java 1.6. Add the following snippet to your pom:

<build>
	<plugins>
		<plugin>
			<groupId>org.apache.maven.plugins</groupId>
			<artifactId>maven-compiler-plugin</artifactId>
			<configuration>
				<source>1.6</source>
				<target>1.6</target>
			</configuration>
		</plugin>
	</plugins>
</build>

<build>

<groupId>org.apache.maven.plugins</groupId>

<artifactId>maven-compiler-plugin</artifactId>

</configuration>

</plugin>

</plugins>

</build>

Very nice video for Eclipse & ANTLR v3 development

by frankdu • January 8, 2010 • 0 Comments

If you are doing antlr v3 for Java, you can be very interested in this series of video tutorials. It demos how to develop with antlr3 IDE, and also the process of a small language. It credits to Marcel for the recommendation. Check it out at:

ANTLR 3.x Tutorials:

http://vimeo.com/groups/29150/videos

Quick Example to Java Scripting Engine

by frankdu • September 28, 2009 • 0 Comments

Have you heard that Java support scripting engine? Try the source code below:

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;


public class TestScript {
	public static void main(String[] args) {
		String script = "println('Hello, world');";
		script += "s=0;";
		script += "for(var i=1; i<=100; i++)";
		script += "s += i;";
		script += "println('s='+s);";

		ScriptEngineManager factory = new ScriptEngineManager();
		ScriptEngine engine = factory.getEngineByName("JavaScript");
		try {
			engine.eval(script);
		} catch (ScriptException e) {
			e.printStackTrace();
		}
	}
}

import javax.script.ScriptEngine;

import javax.script.ScriptEngineManager;

import javax.script.ScriptException;

public class TestScript {

public static void main(String[] args) {

String script = "println('Hello, world');";

script += "s=0;";

script += "for(var i=1; i<=100; i++)";

script += "s += i;";

script += "println('s='+s);";

ScriptEngineManager factory = new ScriptEngineManager();

ScriptEngine engine = factory.getEngineByName("JavaScript");

try {

engine.eval(script);

} catch (ScriptException e) {

e.printStackTrace();

}

Eclipse: Dynamically Adjust Widget Size and Reflow a Form Page

by frankdu • September 25, 2009 • 0 Comments

Let’s say you need to dynamically adjust a widget size, and then update scroll bar information. Things are pretty simple, if we understand how eclipse layout works.

I have a PageBook widget, and wish to resize the form page as selection changes. Here is the important part:

// other code
pageBook.showPage(parent);
Point computeSize = pageBook.computeSize(SWT.DEFAULT, SWT.DEFAULT);

// the following two statements are very important, because they will tell swt/jface how to layout.
GridDataFactory.defaultsFor(pageBook).align(SWT.FILL, SWT.TOP).span(2, 1).hint(SWT.DEFAULT, computeSize.y + 20).applyTo(pageBook);

pageBook.layout(true, true);

// reflow the form
form.reflow(true);

// other code

pageBook.showPage(parent);

Point computeSize = pageBook.computeSize(SWT.DEFAULT, SWT.DEFAULT);

// the following two statements are very important, because they will tell swt/jface how to layout.

GridDataFactory.defaultsFor(pageBook).align(SWT.FILL, SWT.TOP).span(2, 1).hint(SWT.DEFAULT, computeSize.y + 20).applyTo(pageBook);

pageBook.layout(true, true);

// reflow the form

form.reflow(true);

Code Snippet to use PageBook

by frankdu • September 24, 2009 • 0 Comments

Below is very straightforward code snippet to use PageBook. It is used together with eclipse form. Therefore you will see widgets are created via the FormToolkit class.

toolkit = new FormToolkit(container.getDisplay());
form = toolkit.createScrolledForm(container);

Composite parent = form.getBody();
GridLayoutFactory.fillDefaults().numColumns(1).applyTo(parent);

// create a table as selection provider
final Table table = toolkit.createTable(parent, SWT.BORDER | SWT.VIRTUAL);
table.setHeaderVisible(true);
table.setLinesVisible(true);
for(int i=1; i<=12; i++){
	TableItem item = new TableItem(table, 0);
	item.setText("Item " + i);
}

toolkit.createLabel(parent, "Selected pagebook:");

// create a PageBook
final ScrolledPageBook pageBook = toolkit.createPageBook(parent, SWT.NONE);
GridDataFactory.defaultsFor(pageBook).grab(true, true).applyTo(pageBook);

// create PageBook controls
for(int i=0; i<table.getItemCount(); i++){
	TableItem item = table.getItem(i);
	Composite pageContainer = pageBook.createPage(item.getText());
	GridLayoutFactory.fillDefaults().numColumns(1).applyTo(pageContainer);

	toolkit.createLabel(pageContainer, item.getText());
	toolkit.createText(pageContainer, "to be edited");

	pageBook.showPage(item.getText());
}

pageBook.showEmptyPage();

// add selection listener, and show relative PageBook on selection
table.addSelectionListener(new SelectionAdapter(){
	public void widgetSelected(SelectionEvent e) {
		TableItem item = (TableItem) e.item;
		pageBook.showPage(item.getText());
	}
});

toolkit = new FormToolkit(container.getDisplay());

form = toolkit.createScrolledForm(container);

Composite parent = form.getBody();

GridLayoutFactory.fillDefaults().numColumns(1).applyTo(parent);

// create a table as selection provider

final Table table = toolkit.createTable(parent, SWT.BORDER | SWT.VIRTUAL);

table.setHeaderVisible(true);

table.setLinesVisible(true);

for(int i=1; i<=12; i++){

TableItem item = new TableItem(table, 0);

item.setText("Item " + i);

}

toolkit.createLabel(parent, "Selected pagebook:");

// create a PageBook

final ScrolledPageBook pageBook = toolkit.createPageBook(parent, SWT.NONE);

GridDataFactory.defaultsFor(pageBook).grab(true, true).applyTo(pageBook);

// create PageBook controls

for(int i=0; i<table.getItemCount(); i++){

TableItem item = table.getItem(i);

Composite pageContainer = pageBook.createPage(item.getText());

GridLayoutFactory.fillDefaults().numColumns(1).applyTo(pageContainer);

toolkit.createLabel(pageContainer, item.getText());

toolkit.createText(pageContainer, "to be edited");

pageBook.showPage(item.getText());

}

pageBook.showEmptyPage();

// add selection listener, and show relative PageBook on selection

table.addSelectionListener(new SelectionAdapter(){

public void widgetSelected(SelectionEvent e) {

TableItem item = (TableItem) e.item;

pageBook.showPage(item.getText());

}

});

Use maven dependency plugin to copy all dependencies to a folder

by frankdu • July 5, 2009 • 0 Comments

In some cases, we’d like to get all the dependency jar files for a project. There is a maven plugin to do it simply, via a simple way. Just add the build sections to your pom file, as shown below:

<project>
<!-- ....... -->
<build>
	<plugins>
		<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-dependency-plugin</artifactId>
				<executions>
					<execution>
						<id>copy-dependencies</id>
						<phase>process-sources</phase>
						<goals>
							<goal>copy-dependencies</goal>
						</goals>
						<configuration>
							<outputDirectory>c:output</outputDirectory>
							<overWriteReleases>false</overWriteReleases>
							<overWriteSnapshots>false</overWriteSnapshots>
							<overWriteIfNewer>true</overWriteIfNewer>
						</configuration>
					</execution>
				</executions>
			</plugin>
			</plugins>
	</build>

<!-- ....... -->

</project>

<build>

<groupId>org.apache.maven.plugins</groupId>

<artifactId>maven-dependency-plugin</artifactId>

<id>copy-dependencies</id>

<phase>process-sources</phase>

<goals>

<goal>copy-dependencies</goal>

</goals>

<outputDirectory>c:output</outputDirectory>

<overWriteReleases>false</overWriteReleases>

<overWriteSnapshots>false</overWriteSnapshots>

</configuration>

</execution>

</executions>

</plugin>

</plugins>

</build>

</project>

Yahoo API & web services

by frankdu • June 5, 2009 • 0 Comments

Recently I am interested in Yahoo API and web services, especially inquirying finance data via the APIs.

Yahoo provides nice language support. For example, python is supported at

http://developer.yahoo.com/python/

At the bottom of the page, you can find a list of popular programming language, such as Java, .NET, Ruby, Javascript, and so on.

Also at the bottom, there is a list of yahoo services, such as search, finance, weather, flicker….seems a lot of stuff to play with.

The DSL implementation work

by frankdu • May 26, 2009 • 2 Comments

I started to experiment Domain-Specific Language (DSL) implementation two weeks ago. The tool I use is antlr v3. We know that Xtext, TCS, Boo are good DSL toolkit. The reason why we don’t use them for now, is because you may be restricted inside their available functions. For example, xtex is more a Domain-Specific Modeling tool than DSL tool, though they have overlaps. I will have to wait for future xtext versions as I see our requirements go beyonds its current features.

Right now have some experience that may be useful, which is from the coding debugging experience. The prototype I implemented is a dynamic script language. It has its own file structure, which defines input, process, and output options and rules.

The input part defines rules that will assign domain meaning to input data, based on evaluating conditions.

The process part supports arithmetical and string computing. It helps further yield, update data from input.

The output part supports dumping data into certain format like XML. Closure output is supported, since XML has such nature.

The following technologies are used in the prototype:

antlr parser – to construct AST as intermediate format
antlr tree walkers – to go through AST for certain tasks, like variable mapping, math computing, and string operation.
XML pretty printing – I spend no time on embedding such feature in any tree walker. Therefore, a utility class is used for pretty printing.

ANTLR works is a great GUI tool for grammar authoring and debugging. There are eclipse plug-ins for antlr, but I haven’t had time to test them. But more importantly, let’s talk about the grammars.

At antlr.org, we can download many sample grammars for popular languages. However, the parser grammar is only useful to say if an input is valid as the language. The main work is to define compiler/interpreter part in implementing a language. Generally there are two kinds of work in this part: (1). The supporting platform/framework to run the language; (2). The tree walker(s) to do staggered jobs, normally compiling or interpreting tasks. Or simply put, make the language runnable.

I defined 4 grammars, one for parser/lexer, and 3 for AST tree walking. When you DSL goes complicated, it helps to define separate groups functions in different grammar files. For example, we define an emitter class, which only deals with outputting XML results. You may say that there is performance problem if you walking through AST multiple times. I don’t have benchmark data so far and we will see. At least I can see that walking in-memory data structure should be quick and its time complexity is only increased linearly.

The expression calculation is in a separate grammar file, and the corresponding tree parser is a utility class. The statement executor is defined by another grammar file. By this way, it helps to refine the expression definition, and make it easy and quick to be reused in another project. In a production environment, it helps to define them in the same tree walker, but it helps to make it clear in current phase.

A beginner may encounter many issues going through the process. One possible issue is to generated runnable lexer/parser/walker. Since you embed action codes (java, c#, …) in grammar files, you may have to go back and forth multiple times to eliminate compilation errors. A good IDE (eclipse, visual studio) helps a lot in locating such issues.

Another issue is to understand how it works. I’d recommend: (1). debugging through parser/walker code to get famliar with it; (2). Read and run examples at antlr.org to explore wider problem space.

Wish the above stuff may help someone in some way. Feel free to comment if any question.

p.s. I found a bug with CommonTreeNodeStream#index() of antlr-v3.1.3. A bug report had been filed at antlr.org days ago. The bug will affect the following tasks:

shortcut circuiting implementation (&&, ||)
conditional expression ( ? : )
if-else statement (depends on your action implementation)
function definition
may be others (I only explored a subset for now).

Eclipse: How to add a closable editor page in MultiPageEditorpart

by frankdu • March 10, 2009 • 0 Comments

By default, the MultiPageEditorPage doesn’t allow to create closable editor pages. What is closable editor page? It means you can dynamically load and close editor pages, like what you have in EditorPlus, UltraEdit, and Notepad++.

To enable closable editor page, there are a few works to do:

1. Create your subclass of MultiPageEditorPart

2. Add your own addPage method. It will call the existing addPage(…) method, and get a pageIndex of newly added editor page:

//......
int pageIndex = addPage(editor, new MyEditorInput(stepInfo));
setPageText(pageIndex, stepInfo.getName());
setActivePage(pageIndex);

// start to set closable property
Composite container = super.getContainer();
if(container instanceof CTabFolder){
	CTabItem tabItem = ((CTabFolder)container).getItem(pageIndex);
	tabItem.setShowClose(true);
}
// voila! done!

//......

int pageIndex = addPage(editor, new MyEditorInput(stepInfo));

setPageText(pageIndex, stepInfo.getName());

setActivePage(pageIndex);

// start to set closable property

Composite container = super.getContainer();

if(container instanceof CTabFolder){

CTabItem tabItem = ((CTabFolder)container).getItem(pageIndex);

tabItem.setShowClose(true);

}

// voila! done!

Reading notes: Textual DSLs and eclipse modeling (part 2)

by frankdu • February 27, 2009 • 1 Comment

Part 1 of the notes is located at http://www.frankdu.com/weblog/archives/46

The relative presentation slide is located at openArchitectureWare.org.

23. In XText, you start to work with defining concret syntax.

24. For existing meta model, use importMetamodel directive. Use preventMMGeneration to prvent any meta model generation.

25. Simple Editor Customization in Xtext
- Xtend, expression language used throughout oAW
- Constraint checks: oAW check language, based on Xtend
- OutlineView customization: override label(…) and image(…) for meta types
- Content Assist
- customize the font style for keyword (keyword only)

26. Xtext instantiates Ecore metamodels, which means that it can be processed with any EMF tool.
- Within oAW workflow: the only Xtext-specific aspect is using the generated parser. Xpand template language is powerful code generation tool. Easily traverse the model/meta model using Xtend language
- EMF way: EMF’s native resource mechanism (what are the details?)
- Your own code: use the generated parser.

27. NodeUtil with generated parser
- Typically you only work with AST (ecore file)
- Help to obtain info from the parser tree: element location, element text, parser tree node at certain offset.

28. Two phases for doing your DSL:
- designing your language
- building language tools
Xtext focuses on the second phase. Except from the phases, it is also important to provide framework that run the tasks defined your DSL.

29. oAW Xtext become a part of TMF project. The first release is expected in later half 2009.

30. A Xtext parser limitation. It’s impossible to add custom action code in the parser. Sometimes it results in ugly meta models, especially with building expression languages.

Reading notes: Textual DSLs and eclipse modeling (part 1)

by frankdu • February 26, 2009 • 1 Comment

The relative presentation slide is located at openArchitectureWare.org.

Part 2 of the notes is located at http://www.frankdu.com/weblog/archives/52

Below are my reading notes for Textual DSLs and text modeling in eclipse. I haven’t finished the ppt slides. Therefore, this is only part one.

1. EMF servers as the foundation. It provides Ecore Metamodel and framework tools like:
- editing
- transactions
- validation
- query
- distribution/persistence

2. GMF is used for building custom graphical editors based on EMF meta models. It is industry-proven technology. Based on GEF.

3. TMF is used for building custom textual editors. It is in incubation phase. There are two implementations: Xtext and TCS.

4. M2M (Model-to-Model) delivers an extensible framework for m2m transformation languages. ATL is M2M language from INRIA. QVT is an implementation.

5. M2T (Model-to-Text) focuses on transforming models into text (code generation, model serialization). For example, you may want to convert in-memory models into xml files for persistence/transportation purposes. You may want to use a parser to convert xml files back to models. There are 2 so-called frameworks:

- JET is code generation tools that are used by EMF
- Xpand is code generation tools that are part of M2T releases.

6. Xtext is originally from openArchitectureWare.com. It’s a good integration with eclipse. The oAW uses EMF as a basis, bases graphical editors on GMF, and all tooling are based on eclipse. Since Xtext has become part of eclipse TMF, there are two versions of Xtext: oAW Xtext, and TMF Xtext. The former is relatively mature. The latter is under active development, and expected to be first released sometime this year, namely in 2009.

7. DSL is a focused, processable language for addressing specific concerns in a specific domain. It is targeted to be a simple tool for a relatively complex domain. Therefore, in most cases, DSLs are human-readable to domain experts without any training. The popular DSL examples are SQL and Excel.

8. DSLs can be classified in many ways:
- configuration vs. customization
- internal vs. external
- graphical vs. textual

9. Xtext is a so-called framework tool for building external textual customization DSLs.

10. Is it possible to edit same model with both textual and graphical editing interfaces?
It might be possible. Consider one of the following: a. Visualize a subset of the model, using graphvis or prefuse. But it is typically read-only. b. Use different perspectives. Some of them use graphcial editor. It requires cross references between textual and graphical models). c. Edit the same model textually and graphically. Textual format is used as the serialization format from the graphical model. It requires writability and sync of both models!

11. Typically textual DSLs leverage one of many parser generators (ANTLR, Java CC, Lex/yacc). They help to generate a parser based on grammar definition. Consequencely, a parser tries to match text, and try to create a parse tree.

12. Typically, textual DSLs are transformed into an Abstract Syntax Tree (AST). It is ofen a binary tree. For exampe, the AST for 1 + 2*3:

Literal[1] AddExpression ( Literal[2] MultiplyExpression Literal[3])

Literal, AddExpression, and MultiplyExpression are binary nodes.

13. The AST can be taken as a model. But textual DSLs are written without careness of the AST. They can even be against AST.

14. Challenges in Xtext DSL implementation:
- Writting a parser is non-trivial.
- A parser generator makes life easier, but still not one for all.
- A parser generator only creates a matcher and/or a simplistic AST. You still need to further transform the model to easily processable form, and create an editor with syntax highlighting, code completion, etc.

Xtext is designed to ease unbearable burden of life like that.

15. Xtext is based on an EBNF grammar (what’s that? Why will it make a difference?). Xtext will generate:
- ANTLR-based parser
- EMF-based metamodel
- Eclipse editor with or extensible for: syntax highlighting, code completion, code folding, constraint checking, and so on.

16. Different Kinds of Xtext Rules:
- Type Rule
- String Rule
- Enum Rule
- Native Rule

17. Built-in Lexer Types in Xtext:
- ID
- STRING
- INT
- Comments ( Single line and multiple lines)
- Whitespace
The content of those rules is not transformed into the meta model. (How it matters?)

18. Built-in Reference Types in Xtext:
- Reference
- File Reference/Import

19. Abstract Type Rules are implicitly declared with a collection of OR-ed alternatives: R1 | R2 | R3. They will be mapped to abstract metaclass. The alternatives will become subclass. The common properties will be lifted into abstract superclass.

20. String Rules are declared in the format: String [rule_name]: [rule_definition];

21. Enum Rule is mapped to Enum in metamodel. Its format: Enum [rule_name]: [token_name="string"]+;

22. Native Rule. Example:
Native SL_COMMENT:
“‘#’ ~(‘n’|'r’)* ‘r’? ‘n’”;

Term:
1. EMF – Eclipse Modeling Framework
2. GMF – Graphical Modeling Framework
3. GEF – Graphical Editing Framework
4. TMF – Textual Modeling Framework
5. DSL – Domain Specific Langauge
6. JET – Jave Emitter Templates
7. AST – Abstract Syntax Tree

Continue to read: Part 2 of the notes is located at http://www.frankdu.com/weblog/archives/52

Eclipse: how to implement actions for annotation markers?

by frankdu • February 26, 2009 • 1 Comment

In the text editor, the markers are displayed on the vertical ruler. In Java source editor (CompilationUnitEditor class), you can click a problem marker, then a suggestion list will pop up. It’s pretty user friendly, isn’t it?

Then, how to implement our own clickable annotation marker? Generally the following steps address the issue:

Add the extension org.eclipse.ui.editorActions.
Add an editorContribution sub node. Config the contribution.
Implement an AbstractRulerActionDelegate for the contribution. In its createAction method, return your customized action.
Implement your customized action by extending SelectMarkerRulerAction. In the action, you may be interested to traverse through annotation model, to invoke the appropriate commands.

Examples are best tutorials. Therefore, let’s take a look at Java source editor in org.eclipse.jdt.ui, step bey step:

1. The editorActions contribution in JDT UI plug-in:

<extension point="org.eclipse.ui.editorActions">
	<editorContribution
            targetID="org.eclipse.jdt.ui.CompilationUnitEditor"
            id="org.eclipse.jdt.internal.ui.CompilationUnitEditor.ruler.actions">
		<action
               label="%JavaSelectRulerAction.label"
               class="org.eclipse.jdt.internal.ui.javaeditor.JavaSelectRulerAction"
               actionID="RulerClick"
               id="org.eclipse.jdt.internal.ui.javaeditor.JavaSelectRulerAction">
         </action>
	</editorContribution>
</extension>

<editorContribution

targetID="org.eclipse.jdt.ui.CompilationUnitEditor"

id="org.eclipse.jdt.internal.ui.CompilationUnitEditor.ruler.actions">

<action

label="%JavaSelectRulerAction.label"

class="org.eclipse.jdt.internal.ui.javaeditor.JavaSelectRulerAction"

actionID="RulerClick"

id="org.eclipse.jdt.internal.ui.javaeditor.JavaSelectRulerAction">

</action>

</editorContribution>

</extension>

Pay attention to actionID and targetID.

2. The AbstractRulerActionDelegate. It uses template pattern to let you create your own action:

public class JavaSelectRulerAction extends AbstractRulerActionDelegate {
	protected IAction createAction(ITextEditor editor, IVerticalRulerInfo rulerInfo) {
		return new JavaSelectAnnotationRulerAction(JavaEditorMessages.getBundleForConstructedKeys(), "JavaSelectAnnotationRulerAction.", editor, rulerInfo); //$NON-NLS-1$
	}
}

public class JavaSelectRulerAction extends AbstractRulerActionDelegate {

protected IAction createAction(ITextEditor editor, IVerticalRulerInfo rulerInfo) {

return new JavaSelectAnnotationRulerAction(JavaEditorMessages.getBundleForConstructedKeys(), "JavaSelectAnnotationRulerAction.", editor, rulerInfo); //$NON-NLS-1$

}

3. The SelectMarkerRulerAction. It is needed to access the annotation model. If you don’t need to access annotation model, of course you can use other actions. The Java editor version is JavaSelectAnnotationRulerAction. It contains complicated relations. Therefore, to make it simple, here I paste my simple version:

public class DataRequestSelectAnnotationRulerAction extends SelectMarkerRulerAction {

	private ITextEditor fTextEditor;
	private boolean fHasCorrection;
	private Position fPosition;
	private Annotation fAnnotation;

	public DataRequestSelectAnnotationRulerAction(ResourceBundle bundle, String prefix,
			ITextEditor editor, IVerticalRulerInfo ruler) {
		super(bundle, prefix, editor, ruler);
		fTextEditor = editor;
	}

	@Override
	public void run() {
		runWithEvent(null);
	}

	@Override
	public void runWithEvent(Event event) {
		if(fHasCorrection){
			ITextOperationTarget operation= (ITextOperationTarget) fTextEditor.getAdapter(ITextOperationTarget.class);
			final int opCode= ISourceViewer.QUICK_ASSIST;
			if (operation != null && operation.canDoOperation(opCode)) {
				fTextEditor.selectAndReveal(fPosition.getOffset(), fPosition.getLength());
				operation.doOperation(opCode);
			}
		}
	}

	@Override
	public void update() {
		findDataRequestAnnotation();
		setEnabled(true);

		super.update();
	}

	private void findDataRequestAnnotation(){
		fPosition = null;
		fAnnotation = null;
		fHasCorrection = false;

		AbstractMarkerAnnotationModel model = this.getAnnotationModel();
		IAnnotationAccessExtension annotationAccess = this.getAnnotationAccessExtension();

		IDocument document = getDocument();
		if(model == null)
			return;

		boolean hasAssistLightbulb = true;

		Iterator iter = model.getAnnotationIterator();
		int layer = Integer.MIN_VALUE;

		while(iter.hasNext()){
			Annotation annotation = (Annotation)iter.next();

			if(annotation.isMarkedDeleted())
				continue;

			int annotationLayer = layer;
			if(annotationAccess != null){
				annotationLayer = annotationAccess.getLayer(annotation);
				if(annotationLayer < layer)
					continue;
			}

			Position position = model.getPosition(annotation);
			if(!includesRulerLine(position, document))
				continue;

			boolean isReadOnly = fTextEditor instanceof ITextEditorExtension && ((ITextEditorExtension)fTextEditor).isEditorInputReadOnly();

			if(!isReadOnly && (
					((hasAssistLightbulb && annotation instanceof TemporaryAnnotation)))
			){
				fPosition = position;
				fAnnotation = annotation;
				fHasCorrection = true;
				layer = annotationLayer;
				return;
			}

		}
	}

}

public class DataRequestSelectAnnotationRulerAction extends SelectMarkerRulerAction {

private ITextEditor fTextEditor;

private boolean fHasCorrection;

private Position fPosition;

private Annotation fAnnotation;

public DataRequestSelectAnnotationRulerAction(ResourceBundle bundle, String prefix,

ITextEditor editor, IVerticalRulerInfo ruler) {

super(bundle, prefix, editor, ruler);

fTextEditor = editor;

}

@Override

public void run() {

runWithEvent(null);

}

@Override

public void runWithEvent(Event event) {

if(fHasCorrection){

ITextOperationTarget operation= (ITextOperationTarget) fTextEditor.getAdapter(ITextOperationTarget.class);

final int opCode= ISourceViewer.QUICK_ASSIST;

if (operation != null && operation.canDoOperation(opCode)) {

fTextEditor.selectAndReveal(fPosition.getOffset(), fPosition.getLength());

operation.doOperation(opCode);

}

@Override

public void update() {

findDataRequestAnnotation();

setEnabled(true);

super.update();

}

private void findDataRequestAnnotation(){

fPosition = null;

fAnnotation = null;

fHasCorrection = false;

AbstractMarkerAnnotationModel model = this.getAnnotationModel();

IAnnotationAccessExtension annotationAccess = this.getAnnotationAccessExtension();

IDocument document = getDocument();

if(model == null)

return;

boolean hasAssistLightbulb = true;

Iterator iter = model.getAnnotationIterator();

int layer = Integer.MIN_VALUE;

while(iter.hasNext()){

Annotation annotation = (Annotation)iter.next();

if(annotation.isMarkedDeleted())

continue;

int annotationLayer = layer;

if(annotationAccess != null){

annotationLayer = annotationAccess.getLayer(annotation);

if(annotationLayer < layer)

continue;

}

Position position = model.getPosition(annotation);

if(!includesRulerLine(position, document))

continue;

boolean isReadOnly = fTextEditor instanceof ITextEditorExtension && ((ITextEditorExtension)fTextEditor).isEditorInputReadOnly();

if(!isReadOnly && (

((hasAssistLightbulb && annotation instanceof TemporaryAnnotation)))

){

fPosition = position;

fAnnotation = annotation;

fHasCorrection = true;

layer = annotationLayer;

return;

}

Hope the example above helps.

How to open a perspective and view programmatically in eclipse?

by frankdu • February 12, 2009 • 0 Comments

It is very straightforward. Though there are other ways, I will only present one way for now:

IWorkbench workbench = PlatformUI.getWorkbench();
IWorkbenchWindow window = workbench.getActiveWorkbenchWindow();

// open the perspective
workbench.showPerspective("com.frankdu.workbench.perspective_id", window);

// open the view
window.getActivePage().showView("com.frankdu.workbench.view_id");

IWorkbench workbench = PlatformUI.getWorkbench();

IWorkbenchWindow window = workbench.getActiveWorkbenchWindow();

// open the perspective

workbench.showPerspective("com.frankdu.workbench.perspective_id", window);

// open the view

window.getActivePage().showView("com.frankdu.workbench.view_id");

Please note: Of course you need to add the error handling code as prompted by eclipse.

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