/*
 * Copyright (c) 2003, PostgreSQL Global Development Group
 * See the LICENSE file in the project root for more information.
 */

package org.postgresql.util;

/**
 * <p>This code is a stripped down version of Robert Harder's Public Domain Base64 implementation. GZIP
 * support, InputStream and OutputStream stuff and some unneeded encode/decode methods have been
 * removed.</p>
 *
 * <p>-- Original comments follow --</p>
 *
 * <p>Encodes and decodes to and from Base64 notation.</p>
 *
 * <p>
 * Change Log:
 * </p>
 * <ul>
 * <li>v2.1 - Cleaned up javadoc comments and unused variables and methods. Added some convenience
 * methods for reading and writing to and from files.</li>
 * <li>v2.0.2 - Now specifies UTF-8 encoding in places where the code fails on systems with other
 * encodings (like EBCDIC).</li>
 * <li>v2.0.1 - Fixed an error when decoding a single byte, that is, when the encoded data was a
 * single byte.</li>
 * <li>v2.0 - I got rid of methods that used booleans to set options. Now everything is more
 * consolidated and cleaner. The code now detects when data that's being decoded is gzip-compressed
 * and will decompress it automatically. Generally things are cleaner. You'll probably have to
 * change some method calls that you were making to support the new options format (<tt>int</tt>s
 * that you "OR" together).</li>
 * <li>v1.5.1 - Fixed bug when decompressing and decoding to a byte[] using
 * <tt>decode( String s, boolean gzipCompressed )</tt>. Added the ability to "suspend" encoding in
 * the Output Stream so you can turn on and off the encoding if you need to embed base64 data in an
 * otherwise "normal" stream (like an XML file).</li>
 * <li>v1.5 - Output stream pases on flush() command but doesn't do anything itself. This helps when
 * using GZIP streams. Added the ability to GZip-compress objects before encoding them.</li>
 * <li>v1.4 - Added helper methods to read/write files.</li>
 * <li>v1.3.6 - Fixed OutputStream.flush() so that 'position' is reset.</li>
 * <li>v1.3.5 - Added flag to turn on and off line breaks. Fixed bug in input stream where last
 * buffer being read, if not completely full, was not returned.</li>
 * <li>v1.3.4 - Fixed when "improperly padded stream" error was thrown at the wrong time.</li>
 * <li>v1.3.3 - Fixed I/O streams which were totally messed up.</li>
 * </ul>
 *
 * <p>
 * I am placing this code in the Public Domain. Do with it as you will. This software comes with no
 * guarantees or warranties but with plenty of well-wishing instead! Please visit
 * <a href="http://iharder.net/base64">http://iharder.net/base64</a> periodically to check for
 * updates or to contribute improvements.
 * </p>
 *
 * @author Robert Harder
 * @author rob@iharder.net
 * @version 2.1
 */
public class Base64 {

  /* ******** P U B L I C F I E L D S ******** */


  /**
   * No options specified. Value is zero.
   */
  public static final int NO_OPTIONS = 0;

  /**
   * Specify encoding.
   */
  public static final int ENCODE = 1;


  /**
   * Specify decoding.
   */
  public static final int DECODE = 0;


  /**
   * Don't break lines when encoding (violates strict Base64 specification).
   */
  public static final int DONT_BREAK_LINES = 8;


  /* ******** P R I V A T E F I E L D S ******** */


  /**
   * Maximum line length (76) of Base64 output.
   */
  private static final int MAX_LINE_LENGTH = 76;


  /**
   * The equals sign (=) as a byte.
   */
  private static final byte EQUALS_SIGN = (byte) '=';


  /**
   * The new line character (\n) as a byte.
   */
  private static final byte NEW_LINE = (byte) '\n';


  /**
   * Preferred encoding.
   */
  private static final String PREFERRED_ENCODING = "UTF-8";


  /**
   * The 64 valid Base64 values.
   */
  private static final byte[] ALPHABET;
  private static final byte[] _NATIVE_ALPHABET = { /* May be something funny like EBCDIC */
      (byte) 'A', (byte) 'B', (byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F', (byte) 'G',
      (byte) 'H', (byte) 'I', (byte) 'J', (byte) 'K', (byte) 'L', (byte) 'M', (byte) 'N',
      (byte) 'O', (byte) 'P', (byte) 'Q', (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U',
      (byte) 'V', (byte) 'W', (byte) 'X', (byte) 'Y', (byte) 'Z',
      (byte) 'a', (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e', (byte) 'f', (byte) 'g',
      (byte) 'h', (byte) 'i', (byte) 'j', (byte) 'k', (byte) 'l', (byte) 'm', (byte) 'n',
      (byte) 'o', (byte) 'p', (byte) 'q', (byte) 'r', (byte) 's', (byte) 't', (byte) 'u',
      (byte) 'v', (byte) 'w', (byte) 'x', (byte) 'y', (byte) 'z',
      (byte) '0', (byte) '1', (byte) '2', (byte) '3', (byte) '4', (byte) '5',
      (byte) '6', (byte) '7', (byte) '8', (byte) '9', (byte) '+', (byte) '/'
  };

  /* Determine which ALPHABET to use. */
  static {
    byte[] __bytes;
    try {
      __bytes = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
          .getBytes(PREFERRED_ENCODING);
    } catch (java.io.UnsupportedEncodingException use) {
      __bytes = _NATIVE_ALPHABET; // Fall back to native encoding
    }
    ALPHABET = __bytes;
  }


  /**
   * Translates a Base64 value to either its 6-bit reconstruction value or a negative number
   * indicating some other meaning.
   **/
  private static final byte[] DECODABET = {-9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 0 - 8
      -5, -5, // Whitespace: Tab and Linefeed
      -9, -9, // Decimal 11 - 12
      -5, // Whitespace: Carriage Return
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 14 - 26
      -9, -9, -9, -9, -9, // Decimal 27 - 31
      -5, // Whitespace: Space
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 33 - 42
      62, // Plus sign at decimal 43
      -9, -9, -9, // Decimal 44 - 46
      63, // Slash at decimal 47
      52, 53, 54, 55, 56, 57, 58, 59, 60, 61, // Numbers zero through nine
      -9, -9, -9, // Decimal 58 - 60
      -1, // Equals sign at decimal 61
      -9, -9, -9, // Decimal 62 - 64
      0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, // Letters 'A' through 'N'
      14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, // Letters 'O' through 'Z'
      -9, -9, -9, -9, -9, -9, // Decimal 91 - 96
      26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, // Letters 'a' through 'm'
      39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, // Letters 'n' through 'z'
      -9, -9, -9, -9 // Decimal 123 - 126
      /*
       * ,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 127 - 139
       * -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 140 - 152
       * -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 153 - 165
       * -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 166 - 178
       * -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 179 - 191
       * -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 192 - 204
       * -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 205 - 217
       * -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 218 - 230
       * -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 231 - 243
       * -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9 // Decimal 244 - 255
       */
  };

  // I think I end up not using the BAD_ENCODING indicator.
  // private final static byte BAD_ENCODING = -9; // Indicates error in encoding
  private static final byte WHITE_SPACE_ENC = -5; // Indicates white space in encoding
  private static final byte EQUALS_SIGN_ENC = -1; // Indicates equals sign in encoding


  /**
   * Defeats instantiation.
   */
  private Base64() {
  }


  /* ******** E N C O D I N G M E T H O D S ******** */


  /**
   * Encodes up to the first three bytes of array <var>threeBytes</var> and returns a four-byte
   * array in Base64 notation. The actual number of significant bytes in your array is given by
   * <var>numSigBytes</var>. The array <var>threeBytes</var> needs only be as big as
   * <var>numSigBytes</var>. Code can reuse a byte array by passing a four-byte array as
   * <var>b4</var>.
   *
   * @param b4 A reusable byte array to reduce array instantiation
   * @param threeBytes the array to convert
   * @param numSigBytes the number of significant bytes in your array
   * @return four byte array in Base64 notation.
   * @since 1.5.1
   */
  private static byte[] encode3to4(byte[] b4, byte[] threeBytes, int numSigBytes) {
    encode3to4(threeBytes, 0, numSigBytes, b4, 0);
    return b4;
  } // end encode3to4


  /**
   * Encodes up to three bytes of the array <var>source</var> and writes the resulting four Base64
   * bytes to <var>destination</var>. The source and destination arrays can be manipulated anywhere
   * along their length by specifying <var>srcOffset</var> and <var>destOffset</var>. This method
   * does not check to make sure your arrays are large enough to accommodate <var>srcOffset</var> + 3
   * for the <var>source</var> array or <var>destOffset</var> + 4 for the <var>destination</var>
   * array. The actual number of significant bytes in your array is given by <var>numSigBytes</var>.
   *
   * @param source the array to convert
   * @param srcOffset the index where conversion begins
   * @param numSigBytes the number of significant bytes in your array
   * @param destination the array to hold the conversion
   * @param destOffset the index where output will be put
   * @return the <var>destination</var> array
   * @since 1.3
   */
  private static byte[] encode3to4(byte[] source, int srcOffset, int numSigBytes,
      byte[] destination, int destOffset) {
    //           1         2         3
    // 01234567890123456789012345678901 Bit position
    // --------000000001111111122222222 Array position from threeBytes
    // --------|    ||    ||    ||    | Six bit groups to index ALPHABET
    //          >>18  >>12  >> 6  >> 0  Right shift necessary
    //                0x3f  0x3f  0x3f  Additional AND

    // Create buffer with zero-padding if there are only one or two
    // significant bytes passed in the array.
    // We have to shift left 24 in order to flush out the 1's that appear
    // when Java treats a value as negative that is cast from a byte to an int.
    int inBuff = (numSigBytes > 0 ? ((source[srcOffset] << 24) >>> 8) : 0)
        | (numSigBytes > 1 ? ((source[srcOffset + 1] << 24) >>> 16) : 0)
        | (numSigBytes > 2 ? ((source[srcOffset + 2] << 24) >>> 24) : 0);

    switch (numSigBytes) {
      case 3:
        destination[destOffset] = ALPHABET[(inBuff >>> 18)];
        destination[destOffset + 1] = ALPHABET[(inBuff >>> 12) & 0x3f];
        destination[destOffset + 2] = ALPHABET[(inBuff >>> 6) & 0x3f];
        destination[destOffset + 3] = ALPHABET[(inBuff) & 0x3f];
        return destination;

      case 2:
        destination[destOffset] = ALPHABET[(inBuff >>> 18)];
        destination[destOffset + 1] = ALPHABET[(inBuff >>> 12) & 0x3f];
        destination[destOffset + 2] = ALPHABET[(inBuff >>> 6) & 0x3f];
        destination[destOffset + 3] = EQUALS_SIGN;
        return destination;

      case 1:
        destination[destOffset] = ALPHABET[(inBuff >>> 18)];
        destination[destOffset + 1] = ALPHABET[(inBuff >>> 12) & 0x3f];
        destination[destOffset + 2] = EQUALS_SIGN;
        destination[destOffset + 3] = EQUALS_SIGN;
        return destination;

      default:
        return destination;
    } // end switch
  } // end encode3to4

  /**
   * Encodes a byte array into Base64 notation. Does not GZip-compress data.
   *
   * @param source The data to convert
   * @return Base64 notation of input data
   * @since 1.4
   */
  public static String encodeBytes(byte[] source) {
    return encodeBytes(source, 0, source.length, NO_OPTIONS);
  } // end encodeBytes


  /**
   * <p>Encodes a byte array into Base64 notation.</p>
   *
   * <p>Valid options:</p>
   *
   * <pre>
   *   GZIP: gzip-compresses object before encoding it.
   *   DONT_BREAK_LINES: don't break lines at 76 characters
   *     <i>Note: Technically, this makes your encoding non-compliant.</i>
   * </pre>
   *
   * <p>Example: <code>encodeBytes( myData, Base64.GZIP )</code> or</p>
   *
   * <p>Example: <code>encodeBytes(
   * myData, Base64.GZIP | Base64.DONT_BREAK_LINES )</code></p>
   *
   * @param source The data to convert
   * @param options Specified options
   * @return Base64 notation
   * @see Base64#DONT_BREAK_LINES
   * @since 2.0
   */
  public static String encodeBytes(byte[] source, int options) {
    return encodeBytes(source, 0, source.length, options);
  } // end encodeBytes


  /**
   * Encodes a byte array into Base64 notation. Does not GZip-compress data.
   *
   * @param source The data to convert
   * @param off Offset in array where conversion should begin
   * @param len Length of data to convert
   * @return Base64 notation
   * @since 1.4
   */
  public static String encodeBytes(byte[] source, int off, int len) {
    return encodeBytes(source, off, len, NO_OPTIONS);
  } // end encodeBytes


  /**
   * <p>Encodes a byte array into Base64 notation.</p>
   *
   * <p>Valid options:</p>
   *
   * <pre>
   *   GZIP: gzip-compresses object before encoding it.
   *   DONT_BREAK_LINES: don't break lines at 76 characters
   *     <i>Note: Technically, this makes your encoding non-compliant.</i>
   * </pre>
   *
   * <p>Example: <code>encodeBytes( myData, Base64.GZIP )</code> or</p>
   *
   * <p>Example: <code>encodeBytes(
   * myData, Base64.GZIP | Base64.DONT_BREAK_LINES )</code></p>
   *
   * @param source The data to convert
   * @param off Offset in array where conversion should begin
   * @param len Length of data to convert
   * @param options Specified options
   * @return Base64 notation
   * @see Base64#DONT_BREAK_LINES
   * @since 2.0
   */
  public static String encodeBytes(byte[] source, int off, int len, int options) {
    // Isolate options
    int dontBreakLines = (options & DONT_BREAK_LINES);

    // Else, don't compress. Better not to use streams at all then.
    {
      // Convert option to boolean in way that code likes it.
      boolean breakLines = dontBreakLines == 0;

      int len43 = len * 4 / 3;
      byte[] outBuff = new byte[(len43) // Main 4:3
          + ((len % 3) > 0 ? 4 : 0) // Account for padding
          + (breakLines ? (len43 / MAX_LINE_LENGTH) : 0)]; // New lines
      int d = 0;
      int e = 0;
      int len2 = len - 2;
      int lineLength = 0;
      for (; d < len2; d += 3, e += 4) {
        encode3to4(source, d + off, 3, outBuff, e);

        lineLength += 4;
        if (breakLines && lineLength == MAX_LINE_LENGTH) {
          outBuff[e + 4] = NEW_LINE;
          e++;
          lineLength = 0;
        } // end if: end of line
      } // en dfor: each piece of array

      if (d < len) {
        encode3to4(source, d + off, len - d, outBuff, e);
        e += 4;
      } // end if: some padding needed


      // Return value according to relevant encoding.
      try {
        return new String(outBuff, 0, e, PREFERRED_ENCODING);
      } catch (java.io.UnsupportedEncodingException uue) {
        return new String(outBuff, 0, e);
      }

    }

  }


  /* ******** D E C O D I N G M E T H O D S ******** */


  /**
   * Decodes four bytes from array <var>source</var> and writes the resulting bytes (up to three of
   * them) to <var>destination</var>. The source and destination arrays can be manipulated anywhere
   * along their length by specifying <var>srcOffset</var> and <var>destOffset</var>. This method
   * does not check to make sure your arrays are large enough to accommodate <var>srcOffset</var> + 4
   * for the <var>source</var> array or <var>destOffset</var> + 3 for the <var>destination</var>
   * array. This method returns the actual number of bytes that were converted from the Base64
   * encoding.
   *
   * @param source the array to convert
   * @param srcOffset the index where conversion begins
   * @param destination the array to hold the conversion
   * @param destOffset the index where output will be put
   * @return the number of decoded bytes converted
   * @since 1.3
   */
  private static int decode4to3(byte[] source, int srcOffset, byte[] destination, int destOffset) {
    // Example: Dk==
    if (source[srcOffset + 2] == EQUALS_SIGN) {
      // Two ways to do the same thing. Don't know which way I like best.
      // int outBuff = ( ( DECODABET[ source[ srcOffset ] ] << 24 ) >>> 6 )
      // | ( ( DECODABET[ source[ srcOffset + 1] ] << 24 ) >>> 12 );
      int outBuff = ((DECODABET[source[srcOffset]] & 0xFF) << 18)
          | ((DECODABET[source[srcOffset + 1]] & 0xFF) << 12);

      destination[destOffset] = (byte) (outBuff >>> 16);
      return 1;
    } else if (source[srcOffset + 3] == EQUALS_SIGN) {
      // Example: DkL=
      // Two ways to do the same thing. Don't know which way I like best.
      // int outBuff = ( ( DECODABET[ source[ srcOffset ] ] << 24 ) >>> 6 )
      // | ( ( DECODABET[ source[ srcOffset + 1 ] ] << 24 ) >>> 12 )
      // | ( ( DECODABET[ source[ srcOffset + 2 ] ] << 24 ) >>> 18 );
      int outBuff = ((DECODABET[source[srcOffset]] & 0xFF) << 18)
          | ((DECODABET[source[srcOffset + 1]] & 0xFF) << 12)
          | ((DECODABET[source[srcOffset + 2]] & 0xFF) << 6);

      destination[destOffset] = (byte) (outBuff >>> 16);
      destination[destOffset + 1] = (byte) (outBuff >>> 8);
      return 2;
    } else {
      // Example: DkLE
      try {
        // Two ways to do the same thing. Don't know which way I like best.
        // int outBuff = ( ( DECODABET[ source[ srcOffset ] ] << 24 ) >>> 6 )
        // | ( ( DECODABET[ source[ srcOffset + 1 ] ] << 24 ) >>> 12 )
        // | ( ( DECODABET[ source[ srcOffset + 2 ] ] << 24 ) >>> 18 )
        // | ( ( DECODABET[ source[ srcOffset + 3 ] ] << 24 ) >>> 24 );
        int outBuff = ((DECODABET[source[srcOffset]] & 0xFF) << 18)
            | ((DECODABET[source[srcOffset + 1]] & 0xFF) << 12)
            | ((DECODABET[source[srcOffset + 2]] & 0xFF) << 6)
            | ((DECODABET[source[srcOffset + 3]] & 0xFF));


        destination[destOffset] = (byte) (outBuff >> 16);
        destination[destOffset + 1] = (byte) (outBuff >> 8);
        destination[destOffset + 2] = (byte) (outBuff);

        return 3;
      } catch (Exception e) {
        System.out.println("" + source[srcOffset] + ": " + (DECODABET[source[srcOffset]]));
        System.out.println("" + source[srcOffset + 1] + ": " + (DECODABET[source[srcOffset + 1]]));
        System.out.println("" + source[srcOffset + 2] + ": " + (DECODABET[source[srcOffset + 2]]));
        System.out.println("" + source[srcOffset + 3] + ": " + (DECODABET[source[srcOffset + 3]]));
        return -1;
      } // e nd catch
    }
  } // end decodeToBytes


  /**
   * Very low-level access to decoding ASCII characters in the form of a byte array. Does not
   * support automatically gunzipping or any other "fancy" features.
   *
   * @param source The Base64 encoded data
   * @param off The offset of where to begin decoding
   * @param len The length of characters to decode
   * @return decoded data
   * @since 1.3
   */
  public static byte[] decode(byte[] source, int off, int len) {
    int len34 = len * 3 / 4;
    byte[] outBuff = new byte[len34]; // Upper limit on size of output
    int outBuffPosn = 0;

    byte[] b4 = new byte[4];
    int b4Posn = 0;
    int i = 0;
    byte sbiCrop = 0;
    byte sbiDecode = 0;
    for (i = off; i < off + len; i++) {
      sbiCrop = (byte) (source[i] & 0x7f); // Only the low seven bits
      sbiDecode = DECODABET[sbiCrop];

      if (sbiDecode >= WHITE_SPACE_ENC) { // White space, Equals sign or better
        if (sbiDecode >= EQUALS_SIGN_ENC) {
          b4[b4Posn++] = sbiCrop;
          if (b4Posn > 3) {
            outBuffPosn += decode4to3(b4, 0, outBuff, outBuffPosn);
            b4Posn = 0;

            // If that was the equals sign, break out of 'for' loop
            if (sbiCrop == EQUALS_SIGN) {
              break;
            }
          } // end if: quartet built

        } // end if: equals sign or better

      } else {
        // end if: white space, equals sign or better
        System.err.println("Bad Base64 input character at " + i + ": " + source[i] + "(decimal)");
        return null;
      } // end else:
    } // each input character

    byte[] out = new byte[outBuffPosn];
    System.arraycopy(outBuff, 0, out, 0, outBuffPosn);
    return out;
  } // end decode


  /**
   * Decodes data from Base64 notation, automatically detecting gzip-compressed data and
   * decompressing it.
   *
   * @param s the string to decode
   * @return the decoded data
   * @since 1.4
   */
  public static byte[] decode(String s) {
    byte[] bytes;
    try {
      bytes = s.getBytes(PREFERRED_ENCODING);
    } catch (java.io.UnsupportedEncodingException uee) {
      bytes = s.getBytes();
    }
    // </change>

    // Decode
    bytes = decode(bytes, 0, bytes.length);

    return bytes;
  } // end decode

} // end class Base64
