/*
    * Copyright 2012 The Netty Project
    *
    * The Netty Project 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.
   */
  /*
   * Written by Robert Harder and released to the public domain, as explained at
   * http://creativecommons.org/licenses/publicdomain
   */
  package org.jboss.netty.handler.codec.base64;
  
  import org.jboss.netty.buffer.ChannelBuffer;
  import org.jboss.netty.buffer.ChannelBufferFactory;
  import org.jboss.netty.buffer.HeapChannelBufferFactory;
  
  /**
   * Utility class for {@link ChannelBuffer} that encodes and decodes to and from
   * <a href="http://en.wikipedia.org/wiki/Base64">Base64</a> notation.
   * <p>
   * The encoding and decoding algorithm in this class has been derived from
   * <a href="http://iharder.sourceforge.net/current/java/base64/">Robert Harder's Public Domain
   * Base64 Encoder/Decoder</a>.
   *
   * @apiviz.landmark
   * @apiviz.uses org.jboss.netty.handler.codec.base64.Base64Dialect
   */
  public final class Base64 {
  
      /** 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';
  
      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
  
      private static byte[] alphabet(Base64Dialect dialect) {
          if (dialect == null) {
              throw new NullPointerException("dialect");
          }
          return dialect.alphabet;
      }
  
      private static byte[] decodabet(Base64Dialect dialect) {
          if (dialect == null) {
              throw new NullPointerException("dialect");
          }
          return dialect.decodabet;
      }
  
      private static boolean breakLines(Base64Dialect dialect) {
          if (dialect == null) {
              throw new NullPointerException("dialect");
          }
          return dialect.breakLinesByDefault;
      }
  
      public static ChannelBuffer encode(ChannelBuffer src) {
          return encode(src, Base64Dialect.STANDARD);
      }
  
      public static ChannelBuffer encode(ChannelBuffer src, Base64Dialect dialect) {
          return encode(src, breakLines(dialect), dialect);
      }
  
      public static ChannelBuffer encode(
              ChannelBuffer src, ChannelBufferFactory bufferFactory) {
          return encode(src, Base64Dialect.STANDARD, bufferFactory);
      }
  
      public static ChannelBuffer encode(
              ChannelBuffer src, Base64Dialect dialect, ChannelBufferFactory bufferFactory) {
          return encode(src, breakLines(dialect), dialect, bufferFactory);
      }
  
      public static ChannelBuffer encode(ChannelBuffer src, boolean breakLines) {
          return encode(src, breakLines, Base64Dialect.STANDARD);
      }
  
      public static ChannelBuffer encode(
              ChannelBuffer src, boolean breakLines, Base64Dialect dialect) {
          return encode(src, breakLines, dialect, HeapChannelBufferFactory.getInstance());
      }
  
     public static ChannelBuffer encode(
             ChannelBuffer src, boolean breakLines, ChannelBufferFactory bufferFactory) {
         return encode(src, breakLines, Base64Dialect.STANDARD, bufferFactory);
     }
 
     public static ChannelBuffer encode(
             ChannelBuffer src, boolean breakLines, Base64Dialect dialect, ChannelBufferFactory bufferFactory) {
 
         if (src == null) {
             throw new NullPointerException("src");
         }
 
         ChannelBuffer dest = encode(
                 src, src.readerIndex(), src.readableBytes(), breakLines, dialect, bufferFactory);
         src.readerIndex(src.writerIndex());
         return dest;
     }
 
     public static ChannelBuffer encode(ChannelBuffer src, int off, int len) {
         return encode(src, off, len, Base64Dialect.STANDARD);
     }
 
     public static ChannelBuffer encode(ChannelBuffer src, int off, int len, Base64Dialect dialect) {
         return encode(src, off, len, breakLines(dialect), dialect);
     }
 
     public static ChannelBuffer encode(ChannelBuffer src, int off, int len, ChannelBufferFactory bufferFactory) {
         return encode(src, off, len, Base64Dialect.STANDARD, bufferFactory);
     }
 
     public static ChannelBuffer encode(
             ChannelBuffer src, int off, int len, Base64Dialect dialect, ChannelBufferFactory bufferFactory) {
         return encode(src, off, len, breakLines(dialect), dialect, bufferFactory);
     }
 
     public static ChannelBuffer encode(
             ChannelBuffer src, int off, int len, boolean breakLines) {
         return encode(src, off, len, breakLines, Base64Dialect.STANDARD);
     }
 
     public static ChannelBuffer encode(
             ChannelBuffer src, int off, int len,
             boolean breakLines, Base64Dialect dialect) {
         return encode(src, off, len, breakLines, dialect, HeapChannelBufferFactory.getInstance());
     }
 
     public static ChannelBuffer encode(
             ChannelBuffer src, int off, int len,
             boolean breakLines, ChannelBufferFactory bufferFactory) {
         return encode(src, off, len, breakLines, Base64Dialect.STANDARD, bufferFactory);
     }
 
     public static ChannelBuffer encode(
             ChannelBuffer src, int off, int len,
             boolean breakLines, Base64Dialect dialect, ChannelBufferFactory bufferFactory) {
 
         if (src == null) {
             throw new NullPointerException("src");
         }
         if (dialect == null) {
             throw new NullPointerException("dialect");
         }
         if (bufferFactory == null) {
             throw new NullPointerException("bufferFactory");
         }
 
         int len43 = len * 4 / 3;
         ChannelBuffer dest = bufferFactory.getBuffer(
                 src.order(),
                 len43 +
                 (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(src, d + off, 3, dest, e, dialect);
 
             lineLength += 4;
             if (breakLines && lineLength == MAX_LINE_LENGTH) {
                 dest.setByte(e + 4, NEW_LINE);
                 e ++;
                 lineLength = 0;
             } // end if: end of line
         } // end for: each piece of array
 
         if (d < len) {
             encode3to4(src, d + off, len - d, dest, e, dialect);
             e += 4;
         } // end if: some padding needed
 
         return dest.slice(0, e);
     }
 
     private static void encode3to4(
             ChannelBuffer src, int srcOffset, int numSigBytes,
             ChannelBuffer dest, int destOffset, Base64Dialect dialect) {
 
         byte[] ALPHABET = alphabet(dialect);
 
         //           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? src.getByte(srcOffset)     << 24 >>>  8 : 0) |
                 (numSigBytes > 1? src.getByte(srcOffset + 1) << 24 >>> 16 : 0) |
                 (numSigBytes > 2? src.getByte(srcOffset + 2) << 24 >>> 24 : 0);
 
         switch (numSigBytes) {
         case 3:
             dest.setByte(destOffset    , ALPHABET[inBuff >>> 18       ]);
             dest.setByte(destOffset + 1, ALPHABET[inBuff >>> 12 & 0x3f]);
             dest.setByte(destOffset + 2, ALPHABET[inBuff >>>  6 & 0x3f]);
             dest.setByte(destOffset + 3, ALPHABET[inBuff        & 0x3f]);
             break;
         case 2:
             dest.setByte(destOffset    , ALPHABET[inBuff >>> 18       ]);
             dest.setByte(destOffset + 1, ALPHABET[inBuff >>> 12 & 0x3f]);
             dest.setByte(destOffset + 2, ALPHABET[inBuff >>> 6  & 0x3f]);
             dest.setByte(destOffset + 3, EQUALS_SIGN);
             break;
         case 1:
             dest.setByte(destOffset    , ALPHABET[inBuff >>> 18       ]);
             dest.setByte(destOffset + 1, ALPHABET[inBuff >>> 12 & 0x3f]);
             dest.setByte(destOffset + 2, EQUALS_SIGN);
             dest.setByte(destOffset + 3, EQUALS_SIGN);
             break;
         }
     }
 
     public static ChannelBuffer decode(ChannelBuffer src) {
         return decode(src, Base64Dialect.STANDARD);
     }
 
     public static ChannelBuffer decode(ChannelBuffer src, Base64Dialect dialect) {
         return decode(src, dialect, HeapChannelBufferFactory.getInstance());
     }
 
     public static ChannelBuffer decode(ChannelBuffer src, ChannelBufferFactory bufferFactory) {
         return decode(src, Base64Dialect.STANDARD, bufferFactory);
     }
 
     public static ChannelBuffer decode(ChannelBuffer src, Base64Dialect dialect, ChannelBufferFactory bufferFactory) {
 
         if (src == null) {
             throw new NullPointerException("src");
         }
 
         ChannelBuffer dest = decode(src, src.readerIndex(), src.readableBytes(), dialect, bufferFactory);
         src.readerIndex(src.writerIndex());
         return dest;
     }
 
     public static ChannelBuffer decode(
             ChannelBuffer src, int off, int len) {
         return decode(src, off, len, Base64Dialect.STANDARD);
     }
 
     public static ChannelBuffer decode(
             ChannelBuffer src, int off, int len, Base64Dialect dialect) {
         return decode(src, off, len, dialect, HeapChannelBufferFactory.getInstance());
     }
 
     public static ChannelBuffer decode(
             ChannelBuffer src, int off, int len, ChannelBufferFactory bufferFactory) {
         return decode(src, off, len, Base64Dialect.STANDARD, bufferFactory);
     }
 
     public static ChannelBuffer decode(
             ChannelBuffer src, int off, int len, Base64Dialect dialect,
             ChannelBufferFactory bufferFactory) {
 
         if (src == null) {
             throw new NullPointerException("src");
         }
         if (dialect == null) {
             throw new NullPointerException("dialect");
         }
         if (bufferFactory == null) {
             throw new NullPointerException("bufferFactory");
         }
 
         byte[] DECODABET = decodabet(dialect);
 
         int len34 = len * 3 / 4;
         ChannelBuffer dest = bufferFactory.getBuffer(src.order(), 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) (src.getByte(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) { // Equals sign or better?
                     b4[b4Posn ++] = sbiCrop;
                     if (b4Posn > 3) { // Quartet built?
                         outBuffPosn += decode4to3(
                                 b4, 0, dest, outBuffPosn, dialect);
                         b4Posn = 0;
 
                         // If that was the equals sign, break out of 'for' loop
                         if (sbiCrop == EQUALS_SIGN) {
                             break;
                         }
                     }
                 }
             } else {
                 throw new IllegalArgumentException(
                         "bad Base64 input character at " + i + ": " +
                         src.getUnsignedByte(i) + " (decimal)");
             }
         }
 
         return dest.slice(0, outBuffPosn);
     }
 
     private static int decode4to3(
             byte[] src, int srcOffset,
             ChannelBuffer dest, int destOffset, Base64Dialect dialect) {
 
         byte[] DECODABET = decodabet(dialect);
 
         if (src[srcOffset + 2] == EQUALS_SIGN) {
             // Example: Dk==
             int outBuff =
                     (DECODABET[src[srcOffset    ]] & 0xFF) << 18 |
                     (DECODABET[src[srcOffset + 1]] & 0xFF) << 12;
 
             dest.setByte(destOffset, (byte) (outBuff >>> 16));
             return 1;
         } else if (src[srcOffset + 3] == EQUALS_SIGN) {
             // Example: DkL=
             int outBuff =
                     (DECODABET[src[srcOffset    ]] & 0xFF) << 18 |
                     (DECODABET[src[srcOffset + 1]] & 0xFF) << 12 |
                     (DECODABET[src[srcOffset + 2]] & 0xFF) <<  6;
 
             dest.setByte(destOffset    , (byte) (outBuff >>> 16));
             dest.setByte(destOffset + 1, (byte) (outBuff >>>  8));
             return 2;
         } else {
             // Example: DkLE
             int outBuff;
             try {
                 outBuff =
                         (DECODABET[src[srcOffset    ]] & 0xFF) << 18 |
                         (DECODABET[src[srcOffset + 1]] & 0xFF) << 12 |
                         (DECODABET[src[srcOffset + 2]] & 0xFF) <<  6 |
                          DECODABET[src[srcOffset + 3]] & 0xFF;
             } catch (IndexOutOfBoundsException e) {
                 throw new IllegalArgumentException("not encoded in Base64");
             }
 
             dest.setByte(destOffset    , (byte) (outBuff >> 16));
             dest.setByte(destOffset + 1, (byte) (outBuff >>  8));
             dest.setByte(destOffset + 2, (byte)  outBuff);
             return 3;
         }
     }
 
     private Base64() {
         // Unused
     }
 }