/*

 * Copyright (c) 2000, 2005, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package java.util.prefs;

/**

 * Static methods for translating Base64 encoded strings to byte arrays

 * and vice-versa.

 *

 * @author  Josh Bloch

 * @see     Preferences

 * @since   1.4

 */

class Base64 {

    /**

     * Translates the specified byte array into a Base64 string as per

     * Preferences.put(byte[]).

     */

    static String byteArrayToBase64(byte[] a) {

        return byteArrayToBase64(a, false);

    }

    /**

     * Translates the specified byte array into an "alternate representation"

     * Base64 string.  This non-standard variant uses an alphabet that does

     * not contain the uppercase alphabetic characters, which makes it

     * suitable for use in situations where case-folding occurs.

     */

    static String byteArrayToAltBase64(byte[] a) {

        return byteArrayToBase64(a, true);

    }

    private static String byteArrayToBase64(byte[] a, boolean alternate) {

        int aLen = a.length;

        int numFullGroups = aLen/3;

        int numBytesInPartialGroup = aLen - 3*numFullGroups;

        int resultLen = 4*((aLen + 2)/3);

        StringBuilder result = new StringBuilder(resultLen);

        char[] intToAlpha = (alternate ? intToAltBase64 : intToBase64);

        // Translate all full groups from byte array elements to Base64

        int inCursor = 0;

        for (int i=0; i<numFullGroups; i++) {

            int byte0 = a[inCursor++] & 0xff;

            int byte1 = a[inCursor++] & 0xff;

            int byte2 = a[inCursor++] & 0xff;

            result.append(intToAlpha[byte0 >> 2]);

            result.append(intToAlpha[(byte0 << 4)&0x3f | (byte1 >> 4)]);

            result.append(intToAlpha[(byte1 << 2)&0x3f | (byte2 >> 6)]);

            result.append(intToAlpha[byte2 & 0x3f]);

        }

        // Translate partial group if present

        if (numBytesInPartialGroup != 0) {

            int byte0 = a[inCursor++] & 0xff;

            result.append(intToAlpha[byte0 >> 2]);

            if (numBytesInPartialGroup == 1) {

                result.append(intToAlpha[(byte0 << 4) & 0x3f]);

                result.append("==");

            } else {

                // assert numBytesInPartialGroup == 2;

                int byte1 = a[inCursor++] & 0xff;

                result.append(intToAlpha[(byte0 << 4)&0x3f | (byte1 >> 4)]);

                result.append(intToAlpha[(byte1 << 2)&0x3f]);

                result.append('=');

            }

        }

        // assert inCursor == a.length;

        // assert result.length() == resultLen;

        return result.toString();

    }

    /**

     * This array is a lookup table that translates 6-bit positive integer

     * index values into their "Base64 Alphabet" equivalents as specified

     * in Table 1 of RFC 2045.

     */

    private static final char intToBase64[] = {

        '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', '+', '/'

    };

    /**

     * This array is a lookup table that translates 6-bit positive integer

     * index values into their "Alternate Base64 Alphabet" equivalents.

     * This is NOT the real Base64 Alphabet as per in Table 1 of RFC 2045.

     * This alternate alphabet does not use the capital letters.  It is

     * designed for use in environments where "case folding" occurs.

     */

    private static final char intToAltBase64[] = {

        '!', '"', '#', '$', '%', '&', '\'', '(', ')', ',', '-', '.', ':',

        ';', '<', '>', '@', '[', ']', '^',  '`', '_', '{', '|', '}', '~',

        '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', '+', '?'

    };

    /**

     * Translates the specified Base64 string (as per Preferences.get(byte[]))

     * into a byte array.

     *

     * @throws IllegalArgumentException if {@code s} is not a valid Base64

     *         string.

     */

    static byte[] base64ToByteArray(String s) {

        return base64ToByteArray(s, false);

    }

    /**

     * Translates the specified "alternate representation" Base64 string

     * into a byte array.

     *

     * @throws IllegalArgumentException or ArrayOutOfBoundsException

     *         if {@code s} is not a valid alternate representation

     *         Base64 string.

     */

    static byte[] altBase64ToByteArray(String s) {

        return base64ToByteArray(s, true);

    }

    private static byte[] base64ToByteArray(String s, boolean alternate) {

        byte[] alphaToInt = (alternate ?  altBase64ToInt : base64ToInt);

        int sLen = s.length();

        int numGroups = sLen/4;

        if (4*numGroups != sLen)

            throw new IllegalArgumentException(

                "String length must be a multiple of four.");

        int missingBytesInLastGroup = 0;

        int numFullGroups = numGroups;

        if (sLen != 0) {

            if (s.charAt(sLen-1) == '=') {

                missingBytesInLastGroup++;

                numFullGroups--;

            }

            if (s.charAt(sLen-2) == '=')

                missingBytesInLastGroup++;

        }

        byte[] result = new byte[3*numGroups - missingBytesInLastGroup];

        // Translate all full groups from base64 to byte array elements

        int inCursor = 0, outCursor = 0;

        for (int i=0; i<numFullGroups; i++) {

            int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);

            int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);

            int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);

            int ch3 = base64toInt(s.charAt(inCursor++), alphaToInt);

            result[outCursor++] = (byte) ((ch0 << 2) | (ch1 >> 4));

            result[outCursor++] = (byte) ((ch1 << 4) | (ch2 >> 2));

            result[outCursor++] = (byte) ((ch2 << 6) | ch3);

        }

        // Translate partial group, if present

        if (missingBytesInLastGroup != 0) {

            int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);

            int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);

            result[outCursor++] = (byte) ((ch0 << 2) | (ch1 >> 4));

            if (missingBytesInLastGroup == 1) {

                int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);

                result[outCursor++] = (byte) ((ch1 << 4) | (ch2 >> 2));

            }

        }

        // assert inCursor == s.length()-missingBytesInLastGroup;

        // assert outCursor == result.length;

        return result;

    }

    /**

     * Translates the specified character, which is assumed to be in the

     * "Base 64 Alphabet" into its equivalent 6-bit positive integer.

     *

     * @throws IllegalArgumentException or ArrayOutOfBoundsException if

     *         c is not in the Base64 Alphabet.

     */

    private static int base64toInt(char c, byte[] alphaToInt) {

        int result = alphaToInt[c];

        if (result < 0)

            throw new IllegalArgumentException("Illegal character " + c);

        return result;

    }

    /**

     * This array is a lookup table that translates unicode characters

     * drawn from the "Base64 Alphabet" (as specified in Table 1 of RFC 2045)

     * into their 6-bit positive integer equivalents.  Characters that

     * are not in the Base64 alphabet but fall within the bounds of the

     * array are translated to -1.

     */

    private static final byte base64ToInt[] = {

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

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

    };

    /**

     * This array is the analogue of base64ToInt, but for the nonstandard

     * variant that avoids the use of uppercase alphabetic characters.

     */

    private static final byte altBase64ToInt[] = {

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

        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0, 1,

        2, 3, 4, 5, 6, 7, 8, -1, 62, 9, 10, 11, -1 , 52, 53, 54, 55, 56, 57,

        58, 59, 60, 61, 12, 13, 14, -1, 15, 63, 16, -1, -1, -1, -1, -1, -1,

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

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

    };

    public static void main(String args[]) {

        int numRuns  = Integer.parseInt(args[0]);

        int numBytes = Integer.parseInt(args[1]);

        java.util.Random rnd = new java.util.Random();

        for (int i=0; i<numRuns; i++) {

            for (int j=0; j<numBytes; j++) {

                byte[] arr = new byte[j];

                for (int k=0; k<j; k++)

                    arr[k] = (byte)rnd.nextInt();

                String s = byteArrayToBase64(arr);

                byte [] b = base64ToByteArray(s);

                if (!java.util.Arrays.equals(arr, b))

                    System.out.println("Dismal failure!");

                s = byteArrayToAltBase64(arr);

                b = altBase64ToByteArray(s);

                if (!java.util.Arrays.equals(arr, b))

                    System.out.println("Alternate dismal failure!");

            }

        }

    }

}