// Mozilla has modified this file - see http://hg.mozilla.org/ for details.
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 */

package org.mozilla.apache.commons.codec.binary;

/**
 * Provides Base32 encoding and decoding as defined by <a href="http://www.ietf.org/rfc/rfc4648.txt">RFC 4648</a>.
 * 
 * <p>
 * The class can be parameterized in the following manner with various constructors:
 * <ul>
 * <li>Whether to use the "base32hex" variant instead of the default "base32"</li>
 * <li>Line length: Default 76. Line length that aren't multiples of 8 will still essentially end up being multiples of
 * 8 in the encoded data.
 * <li>Line separator: Default is CRLF ("\r\n")</li>
 * </ul>
 * </p>
 * <p>
 * This class operates directly on byte streams, and not character streams.
 * </p>
 * <p>
 * This class is not thread-safe. Each thread should use its own instance.
 * </p>
 * 
 * @see <a href="http://www.ietf.org/rfc/rfc4648.txt">RFC 4648</a>
 * 
 * @since 1.5
 * @version $Revision: 1080712 $
 */
public class Base32 extends BaseNCodec {

    /**
     * BASE32 characters are 5 bits in length. 
     * They are formed by taking a block of five octets to form a 40-bit string, 
     * which is converted into eight BASE32 characters.
     */
    private static final int BITS_PER_ENCODED_BYTE = 5;
    private static final int BYTES_PER_ENCODED_BLOCK = 8;
    private static final int BYTES_PER_UNENCODED_BLOCK = 5;

    /**
     * Chunk separator per RFC 2045 section 2.1.
     *
     * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045 section 2.1</a>
     */
    private static final byte[] CHUNK_SEPARATOR = {'\r', '\n'};

    /**
     * This array is a lookup table that translates Unicode characters drawn from the "Base32 Alphabet" (as specified in
     * Table 3 of RFC 2045) into their 5-bit positive integer equivalents. Characters that are not in the Base32
     * alphabet but fall within the bounds of the array are translated to -1.
     * 
     */
    private static final byte[] DECODE_TABLE = {
         //  0   1   2   3   4   5   6   7   8   9   A   B   C   D   E   F
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 00-0f
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 10-1f
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 63, // 20-2f
            -1, -1, 26, 27, 28, 29, 30, 31, -1, -1, -1, -1, -1, -1, -1, -1, // 30-3f 2-7
            -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, // 40-4f A-N
            15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,                     // 50-5a O-Z
    };

    /**
     * This array is a lookup table that translates 5-bit positive integer index values into their "Base32 Alphabet"
     * equivalents as specified in Table 3 of RFC 2045.
     */
    private static final byte[] ENCODE_TABLE = {
            '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',
            '2', '3', '4', '5', '6', '7',
    };

    /**
     * This array is a lookup table that translates Unicode characters drawn from the "Base32 |Hex Alphabet" (as specified in
     * Table 3 of RFC 2045) into their 5-bit positive integer equivalents. Characters that are not in the Base32 Hex
     * alphabet but fall within the bounds of the array are translated to -1.
     * 
     */
    private static final byte[] HEX_DECODE_TABLE = {
         //  0   1   2   3   4   5   6   7   8   9   A   B   C   D   E   F
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 00-0f
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 10-1f
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 63, // 20-2f
             0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1, // 30-3f 2-7
            -1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, // 40-4f A-N
            25, 26, 27, 28, 29, 30, 31, 32,                                 // 50-57 O-V
    };

    /**
     * This array is a lookup table that translates 5-bit positive integer index values into their "Base32 Hex Alphabet"
     * equivalents as specified in Table 3 of RFC 2045.
     */
    private static final byte[] HEX_ENCODE_TABLE = {
            '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 
            'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
            'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V',
    };

    /** Mask used to extract 5 bits, used when encoding Base32 bytes */
    private static final int MASK_5BITS = 0x1f;

    // The static final fields above are used for the original static byte[] methods on Base32.
    // The private member fields below are used with the new streaming approach, which requires
    // some state be preserved between calls of encode() and decode().

    /**
     * Place holder for the bytes we're dealing with for our based logic. 
     * Bitwise operations store and extract the encoding or decoding from this variable.
     */
    private long bitWorkArea;

    /**
     * Convenience variable to help us determine when our buffer is going to run out of room and needs resizing.
     * <code>decodeSize = {@link BYTES_PER_ENCODED_BLOCK} - 1 + lineSeparator.length;</code>
     */
    private final int decodeSize;

    /**
     * Decode table to use.
     */
    private final byte[] decodeTable;

    /**
     * Convenience variable to help us determine when our buffer is going to run out of room and needs resizing.
     * <code>encodeSize = {@link BYTES_PER_ENCODED_BLOCK} + lineSeparator.length;</code>
     */
    private final int encodeSize;

    /**
     * Encode table to use.
     */
    private final byte[] encodeTable;

    /**
     * Line separator for encoding. Not used when decoding. Only used if lineLength > 0.
     */
    private final byte[] lineSeparator;

    /**
     * Creates a Base32 codec used for decoding and encoding.
     * <p>
     * When encoding the line length is 0 (no chunking).
     * </p>
     * 
     */
    public Base32() {
        this(false);
    }

    /**
     * Creates a Base32 codec used for decoding and encoding.
     * <p>
     * When encoding the line length is 0 (no chunking).
     * </p>
     * @param useHex if <code>true</code> then use Base32 Hex alphabet
     */
    public Base32(boolean useHex) {
        this(0, null, useHex);
    }

    /**
     * Creates a Base32 codec used for decoding and encoding.
     * <p>
     * When encoding the line length is given in the constructor, the line separator is CRLF.
     * </p>
     * 
     * @param lineLength
     *            Each line of encoded data will be at most of the given length (rounded down to nearest multiple of 8).
     *            If lineLength <= 0, then the output will not be divided into lines (chunks). Ignored when decoding.
     */
    public Base32(int lineLength) {
        this(lineLength, CHUNK_SEPARATOR);
    }

    /**
     * Creates a Base32 codec used for decoding and encoding.
     * <p>
     * When encoding the line length and line separator are given in the constructor.
     * </p>
     * <p>
     * Line lengths that aren't multiples of 8 will still essentially end up being multiples of 8 in the encoded data.
     * </p>
     * 
     * @param lineLength
     *            Each line of encoded data will be at most of the given length (rounded down to nearest multiple of 8).
     *            If lineLength <= 0, then the output will not be divided into lines (chunks). Ignored when decoding.
     * @param lineSeparator
     *            Each line of encoded data will end with this sequence of bytes.
     * @throws IllegalArgumentException
     *             The provided lineSeparator included some Base32 characters. That's not going to work!
     */
    public Base32(int lineLength, byte[] lineSeparator) {
        this(lineLength, lineSeparator, false);
    }
    
    /**
     * Creates a Base32 / Base32 Hex codec used for decoding and encoding.
     * <p>
     * When encoding the line length and line separator are given in the constructor.
     * </p>
     * <p>
     * Line lengths that aren't multiples of 8 will still essentially end up being multiples of 8 in the encoded data.
     * </p>
     * 
     * @param lineLength
     *            Each line of encoded data will be at most of the given length (rounded down to nearest multiple of 8).
     *            If lineLength <= 0, then the output will not be divided into lines (chunks). Ignored when decoding.
     * @param lineSeparator
     *            Each line of encoded data will end with this sequence of bytes.
     * @param useHex if <code>true</code>, then use Base32 Hex alphabet, otherwise use Base32 alphabet
     * @throws IllegalArgumentException
     *             The provided lineSeparator included some Base32 characters. That's not going to work!
     *             Or the lineLength > 0 and lineSeparator is null.
     */
    public Base32(int lineLength, byte[] lineSeparator, boolean useHex) {
        super(BYTES_PER_UNENCODED_BLOCK, BYTES_PER_ENCODED_BLOCK, 
                lineLength, 
                lineSeparator == null ? 0 : lineSeparator.length);
        if (useHex){
            this.encodeTable = HEX_ENCODE_TABLE;
            this.decodeTable = HEX_DECODE_TABLE;            
        } else {
            this.encodeTable = ENCODE_TABLE;
            this.decodeTable = DECODE_TABLE;            
        }
        if (lineLength > 0) {
            if (lineSeparator == null) {
                throw new IllegalArgumentException("lineLength "+lineLength+" > 0, but lineSeparator is null");
            }
            // Must be done after initializing the tables
            if (containsAlphabetOrPad(lineSeparator)) {
                String sep = StringUtils.newStringUtf8(lineSeparator);
                throw new IllegalArgumentException("lineSeparator must not contain Base32 characters: [" + sep + "]");
            }
            this.encodeSize = BYTES_PER_ENCODED_BLOCK + lineSeparator.length;
            this.lineSeparator = new byte[lineSeparator.length];
            System.arraycopy(lineSeparator, 0, this.lineSeparator, 0, lineSeparator.length);
        } else {
            this.encodeSize = BYTES_PER_ENCODED_BLOCK;
            this.lineSeparator = null;
        }
        this.decodeSize = this.encodeSize - 1;
    }

    /**
     * <p>
     * Decodes all of the provided data, starting at inPos, for inAvail bytes. Should be called at least twice: once
     * with the data to decode, and once with inAvail set to "-1" to alert decoder that EOF has been reached. The "-1"
     * call is not necessary when decoding, but it doesn't hurt, either.
     * </p>
     * <p>
     * Ignores all non-Base32 characters. This is how chunked (e.g. 76 character) data is handled, since CR and LF are
     * silently ignored, but has implications for other bytes, too. This method subscribes to the garbage-in,
     * garbage-out philosophy: it will not check the provided data for validity.
     * </p>
     * 
     * @param in
     *            byte[] array of ascii data to Base32 decode.
     * @param inPos
     *            Position to start reading data from.
     * @param inAvail
     *            Amount of bytes available from input for encoding.
     *
     * Output is written to {@link #buffer} as 8-bit octets, using {@link pos} as the buffer position
     */
    void decode(byte[] in, int inPos, int inAvail) { // package protected for access from I/O streams
        if (eof) {
            return;
        }
        if (inAvail < 0) {
            eof = true;
        }
        for (int i = 0; i < inAvail; i++) {
            byte b = in[inPos++];
            if (b == PAD) {
                // We're done.
                eof = true;
                break;
            } else {
                ensureBufferSize(decodeSize);
                if (b >= 0 && b < this.decodeTable.length) {
                    int result = this.decodeTable[b];
                    if (result >= 0) {
                        modulus = (modulus+1) % BYTES_PER_ENCODED_BLOCK;
                        bitWorkArea = (bitWorkArea << BITS_PER_ENCODED_BYTE) + result; // collect decoded bytes
                        if (modulus == 0) { // we can output the 5 bytes
                            buffer[pos++] = (byte) ((bitWorkArea >> 32) & MASK_8BITS);
                            buffer[pos++] = (byte) ((bitWorkArea >> 24) & MASK_8BITS);
                            buffer[pos++] = (byte) ((bitWorkArea >> 16) & MASK_8BITS);
                            buffer[pos++] = (byte) ((bitWorkArea >> 8) & MASK_8BITS);
                            buffer[pos++] = (byte) (bitWorkArea & MASK_8BITS);
                        }
                    }
                }
            }
        }
    
        // Two forms of EOF as far as Base32 decoder is concerned: actual
        // EOF (-1) and first time '=' character is encountered in stream.
        // This approach makes the '=' padding characters completely optional.
        if (eof && modulus >= 2) { // if modulus < 2, nothing to do
            ensureBufferSize(decodeSize);
    
            //  we ignore partial bytes, i.e. only multiples of 8 count
            switch (modulus) {
                case 2 : // 10 bits, drop 2 and output one byte
                    buffer[pos++] = (byte) ((bitWorkArea >> 2) & MASK_8BITS);
                    break;
                case 3 : // 15 bits, drop 7 and output 1 byte
                    buffer[pos++] = (byte) ((bitWorkArea >> 7) & MASK_8BITS);
                    break;
                case 4 : // 20 bits = 2*8 + 4
                    bitWorkArea = bitWorkArea >> 4; // drop 4 bits
                    buffer[pos++] = (byte) ((bitWorkArea >> 8) & MASK_8BITS);
                    buffer[pos++] = (byte) ((bitWorkArea) & MASK_8BITS);
                    break;
                case 5 : // 25bits = 3*8 + 1
                    bitWorkArea = bitWorkArea >> 1;
                    buffer[pos++] = (byte) ((bitWorkArea >> 16) & MASK_8BITS);
                    buffer[pos++] = (byte) ((bitWorkArea >> 8) & MASK_8BITS);
                    buffer[pos++] = (byte) ((bitWorkArea) & MASK_8BITS);
                    break;
                case 6 : // 30bits = 3*8 + 6
                    bitWorkArea = bitWorkArea >> 6;
                    buffer[pos++] = (byte) ((bitWorkArea >> 16) & MASK_8BITS);
                    buffer[pos++] = (byte) ((bitWorkArea >> 8) & MASK_8BITS);
                    buffer[pos++] = (byte) ((bitWorkArea) & MASK_8BITS);
                    break;
                case 7 : // 35 = 4*8 +3
                    bitWorkArea = bitWorkArea >> 3;
                    buffer[pos++] = (byte) ((bitWorkArea >> 24) & MASK_8BITS);
                    buffer[pos++] = (byte) ((bitWorkArea >> 16) & MASK_8BITS);
                    buffer[pos++] = (byte) ((bitWorkArea >> 8) & MASK_8BITS);
                    buffer[pos++] = (byte) ((bitWorkArea) & MASK_8BITS);
                    break;
            }
        }
    }

    /**
     * <p>
     * Encodes all of the provided data, starting at inPos, for inAvail bytes. Must be called at least twice: once with
     * the data to encode, and once with inAvail set to "-1" to alert encoder that EOF has been reached, so flush last
     * remaining bytes (if not multiple of 5).
     * </p>
     * 
     * @param in
     *            byte[] array of binary data to Base32 encode.
     * @param inPos
     *            Position to start reading data from.
     * @param inAvail
     *            Amount of bytes available from input for encoding.
     */
    void encode(byte[] in, int inPos, int inAvail) { // package protected for access from I/O streams
        if (eof) {
            return;
        }
        // inAvail < 0 is how we're informed of EOF in the underlying data we're
        // encoding.
        if (inAvail < 0) {
            eof = true;
            if (0 == modulus && lineLength == 0) {
                return; // no leftovers to process and not using chunking
            }
            ensureBufferSize(encodeSize);
            int savedPos = pos;
            switch (modulus) { // % 5
                case 1 : // Only 1 octet; take top 5 bits then remainder
                    buffer[pos++] = encodeTable[(int)(bitWorkArea >> 3) & MASK_5BITS]; // 8-1*5 = 3
                    buffer[pos++] = encodeTable[(int)(bitWorkArea << 2) & MASK_5BITS]; // 5-3=2
                    buffer[pos++] = PAD;
                    buffer[pos++] = PAD;
                    buffer[pos++] = PAD;
                    buffer[pos++] = PAD;
                    buffer[pos++] = PAD;
                    buffer[pos++] = PAD;
                    break;
    
                case 2 : // 2 octets = 16 bits to use
                    buffer[pos++] = encodeTable[(int)(bitWorkArea >> 11) & MASK_5BITS]; // 16-1*5 = 11
                    buffer[pos++] = encodeTable[(int)(bitWorkArea >>  6) & MASK_5BITS]; // 16-2*5 = 6
                    buffer[pos++] = encodeTable[(int)(bitWorkArea >>  1) & MASK_5BITS]; // 16-3*5 = 1
                    buffer[pos++] = encodeTable[(int)(bitWorkArea <<  4) & MASK_5BITS]; // 5-1 = 4
                    buffer[pos++] = PAD;
                    buffer[pos++] = PAD;
                    buffer[pos++] = PAD;
                    buffer[pos++] = PAD;
                    break;
                case 3 : // 3 octets = 24 bits to use
                    buffer[pos++] = encodeTable[(int)(bitWorkArea >> 19) & MASK_5BITS]; // 24-1*5 = 19
                    buffer[pos++] = encodeTable[(int)(bitWorkArea >> 14) & MASK_5BITS]; // 24-2*5 = 14
                    buffer[pos++] = encodeTable[(int)(bitWorkArea >>  9) & MASK_5BITS]; // 24-3*5 = 9
                    buffer[pos++] = encodeTable[(int)(bitWorkArea >>  4) & MASK_5BITS]; // 24-4*5 = 4
                    buffer[pos++] = encodeTable[(int)(bitWorkArea <<  1) & MASK_5BITS]; // 5-4 = 1
                    buffer[pos++] = PAD;
                    buffer[pos++] = PAD;
                    buffer[pos++] = PAD;
                    break;
                case 4 : // 4 octets = 32 bits to use
                    buffer[pos++] = encodeTable[(int)(bitWorkArea >> 27) & MASK_5BITS]; // 32-1*5 = 27
                    buffer[pos++] = encodeTable[(int)(bitWorkArea >> 22) & MASK_5BITS]; // 32-2*5 = 22
                    buffer[pos++] = encodeTable[(int)(bitWorkArea >> 17) & MASK_5BITS]; // 32-3*5 = 17
                    buffer[pos++] = encodeTable[(int)(bitWorkArea >> 12) & MASK_5BITS]; // 32-4*5 = 12
                    buffer[pos++] = encodeTable[(int)(bitWorkArea >>  7) & MASK_5BITS]; // 32-5*5 =  7
                    buffer[pos++] = encodeTable[(int)(bitWorkArea >>  2) & MASK_5BITS]; // 32-6*5 =  2
                    buffer[pos++] = encodeTable[(int)(bitWorkArea <<  3) & MASK_5BITS]; // 5-2 = 3
                    buffer[pos++] = PAD;
                    break;
            }
            currentLinePos += pos - savedPos; // keep track of current line position
            // if currentPos == 0 we are at the start of a line, so don't add CRLF
            if (lineLength > 0 && currentLinePos > 0){ // add chunk separator if required
                System.arraycopy(lineSeparator, 0, buffer, pos, lineSeparator.length);
                pos += lineSeparator.length;
            }            
        } else {
            for (int i = 0; i < inAvail; i++) {
                ensureBufferSize(encodeSize);
                modulus = (modulus+1) % BYTES_PER_UNENCODED_BLOCK;
                int b = in[inPos++];
                if (b < 0) {
                    b += 256;
                }
                bitWorkArea = (bitWorkArea << 8) + b; // BITS_PER_BYTE
                if (0 == modulus) { // we have enough bytes to create our output 
                    buffer[pos++] = encodeTable[(int)(bitWorkArea >> 35) & MASK_5BITS];
                    buffer[pos++] = encodeTable[(int)(bitWorkArea >> 30) & MASK_5BITS];
                    buffer[pos++] = encodeTable[(int)(bitWorkArea >> 25) & MASK_5BITS];
                    buffer[pos++] = encodeTable[(int)(bitWorkArea >> 20) & MASK_5BITS];
                    buffer[pos++] = encodeTable[(int)(bitWorkArea >> 15) & MASK_5BITS];
                    buffer[pos++] = encodeTable[(int)(bitWorkArea >> 10) & MASK_5BITS];
                    buffer[pos++] = encodeTable[(int)(bitWorkArea >> 5) & MASK_5BITS];
                    buffer[pos++] = encodeTable[(int)bitWorkArea & MASK_5BITS];
                    currentLinePos += BYTES_PER_ENCODED_BLOCK;
                    if (lineLength > 0 && lineLength <= currentLinePos) {
                        System.arraycopy(lineSeparator, 0, buffer, pos, lineSeparator.length);
                        pos += lineSeparator.length;
                        currentLinePos = 0;
                    }
                }
            }
        }
    }

    /**
     * Returns whether or not the <code>octet</code> is in the Base32 alphabet.
     * 
     * @param octet
     *            The value to test
     * @return <code>true</code> if the value is defined in the the Base32 alphabet <code>false</code> otherwise.
     */
    public boolean isInAlphabet(byte octet) {
        return octet >= 0 && octet < decodeTable.length && decodeTable[octet] != -1;
    }
}
