content: /*
   * 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 com.zzzmode.apkeditor.utils;
  
  import java.util.Arrays;
  
  /**
   * Abstract superclass for Base-N encoders and decoders.
   *
   * <p>
   * This class is thread-safe.
   * </p>
   *
   * @version $Id$
   */
  public abstract class BaseNCodec implements BinaryEncoder, BinaryDecoder {
  
      /**
       * Holds thread context so classes can be thread-safe.
       *
       * This class is not itself thread-safe; each thread must allocate its own copy.
       *
       * @since 1.7
       */
      static class Context {
  
          /**
           * 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.
           */
          int ibitWorkArea;
  
          /**
           * 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.
           */
          long lbitWorkArea;
  
          /**
           * Buffer for streaming.
           */
          byte[] buffer;
  
          /**
           * Position where next character should be written in the buffer.
           */
          int pos;
  
          /**
           * Position where next character should be read from the buffer.
           */
          int readPos;
  
          /**
           * Boolean flag to indicate the EOF has been reached. Once EOF has been reached, this object becomes useless,
           * and must be thrown away.
           */
          boolean eof;
  
          /**
           * Variable tracks how many characters have been written to the current line. Only used when encoding. We use
           * it to make sure each encoded line never goes beyond lineLength (if lineLength &gt; 0).
           */
          int currentLinePos;
  
          /**
           * Writes to the buffer only occur after every 3/5 reads when encoding, and every 4/8 reads when decoding. This
           * variable helps track that.
           */
          int modulus;
  
          Context() {
          }
  
          /**
           * Returns a String useful for debugging (especially within a debugger.)
           *
           * @return a String useful for debugging.
           */
          @SuppressWarnings("boxing") // OK to ignore boxing here
          @Override
          public String toString() {
              return String.format("%s[buffer=%s, currentLinePos=%s, eof=%s, ibitWorkArea=%s, lbitWorkArea=%s, " +
                      "modulus=%s, pos=%s, readPos=%s]", this.getClass().getSimpleName(), Arrays.toString(buffer),
                      currentLinePos, eof, ibitWorkArea, lbitWorkArea, modulus, pos, readPos);
          }
      }
  
      /**
       * EOF
       *
       * @since 1.7
       */
      static final int EOF = -1;
  
      /**
       *  MIME chunk size per RFC 2045 section 6.8.
       *
       * <p>
       * The {@value} character limit does not count the trailing CRLF, but counts all other characters, including any
       * equal signs.
       * </p>
       *
       * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045 section 6.8</a>
       */
      public static final int MIME_CHUNK_SIZE = 76;
  
      /**
       * PEM chunk size per RFC 1421 section 4.3.2.4.
       *
       * <p>
       * The {@value} character limit does not count the trailing CRLF, but counts all other characters, including any
       * equal signs.
       * </p>
       *
       * @see <a href="http://tools.ietf.org/html/rfc1421">RFC 1421 section 4.3.2.4</a>
       */
      public static final int PEM_CHUNK_SIZE = 64;
  
      private static final int DEFAULT_BUFFER_RESIZE_FACTOR = 2;
  
      /**
       * Defines the default buffer size - currently {@value}
       * - must be large enough for at least one encoded block+separator
       */
      private static final int DEFAULT_BUFFER_SIZE = 8192;
  
      /** Mask used to extract 8 bits, used in decoding bytes */
      protected static final int MASK_8BITS = 0xff;
  
      /**
       * Byte used to pad output.
       */
      protected static final byte PAD_DEFAULT = '='; // Allow static access to default
  
      /**
       * @deprecated Use {@link #pad}. Will be removed in 2.0.
       */
      @Deprecated
      protected final byte PAD = PAD_DEFAULT; // instance variable just in case it needs to vary later
  
      protected final byte pad; // instance variable just in case it needs to vary later
  
      /** Number of bytes in each full block of unencoded data, e.g. 4 for Base64 and 5 for Base32 */
      private final int unencodedBlockSize;
  
      /** Number of bytes in each full block of encoded data, e.g. 3 for Base64 and 8 for Base32 */
      private final int encodedBlockSize;
  
      /**
       * Chunksize for encoding. Not used when decoding.
       * A value of zero or less implies no chunking of the encoded data.
       * Rounded down to nearest multiple of encodedBlockSize.
       */
      protected final int lineLength;
  
      /**
       * Size of chunk separator. Not used unless {@link #lineLength} &gt; 0.
       */
      private final int chunkSeparatorLength;
  
      /**
       * Note <code>lineLength</code> is rounded down to the nearest multiple of {@link #encodedBlockSize}
       * If <code>chunkSeparatorLength</code> is zero, then chunking is disabled.
       * @param unencodedBlockSize the size of an unencoded block (e.g. Base64 = 3)
       * @param encodedBlockSize the size of an encoded block (e.g. Base64 = 4)
       * @param lineLength if &gt; 0, use chunking with a length <code>lineLength</code>
       * @param chunkSeparatorLength the chunk separator length, if relevant
       */
      protected BaseNCodec(final int unencodedBlockSize, final int encodedBlockSize,
                           final int lineLength, final int chunkSeparatorLength) {
          this(unencodedBlockSize, encodedBlockSize, lineLength, chunkSeparatorLength, PAD_DEFAULT);
      }
  
      /**
       * Note <code>lineLength</code> is rounded down to the nearest multiple of {@link #encodedBlockSize}
       * If <code>chunkSeparatorLength</code> is zero, then chunking is disabled.
       * @param unencodedBlockSize the size of an unencoded block (e.g. Base64 = 3)
       * @param encodedBlockSize the size of an encoded block (e.g. Base64 = 4)
       * @param lineLength if &gt; 0, use chunking with a length <code>lineLength</code>
       * @param chunkSeparatorLength the chunk separator length, if relevant
       * @param pad byte used as padding byte.
       */
      protected BaseNCodec(final int unencodedBlockSize, final int encodedBlockSize,
                           final int lineLength, final int chunkSeparatorLength, final byte pad) {
          this.unencodedBlockSize = unencodedBlockSize;
          this.encodedBlockSize = encodedBlockSize;
          final boolean useChunking = lineLength > 0 && chunkSeparatorLength > 0;
          this.lineLength = useChunking ? (lineLength / encodedBlockSize) * encodedBlockSize : 0;
          this.chunkSeparatorLength = chunkSeparatorLength;
  
          this.pad = pad;
      }
  
      /**
       * Returns true if this object has buffered data for reading.
       *
       * @param context the context to be used
       * @return true if there is data still available for reading.
       */
      boolean hasData(final Context context) {  // package protected for access from I/O streams
          return context.buffer != null;
      }
  
      /**
       * Returns the amount of buffered data available for reading.
       *
       * @param context the context to be used
       * @return The amount of buffered data available for reading.
       */
      int available(final Context context) {  // package protected for access from I/O streams
          return context.buffer != null ? context.pos - context.readPos : 0;
      }
  
      /**
       * Get the default buffer size. Can be overridden.
       *
       * @return {@link #DEFAULT_BUFFER_SIZE}
       */
      protected int getDefaultBufferSize() {
          return DEFAULT_BUFFER_SIZE;
      }
  
      /**
       * Increases our buffer by the {@link #DEFAULT_BUFFER_RESIZE_FACTOR}.
       * @param context the context to be used
       */
      private byte[] resizeBuffer(final Context context) {
          if (context.buffer == null) {
              context.buffer = new byte[getDefaultBufferSize()];
              context.pos = 0;
              context.readPos = 0;
          } else {
              final byte[] b = new byte[context.buffer.length * DEFAULT_BUFFER_RESIZE_FACTOR];
              System.arraycopy(context.buffer, 0, b, 0, context.buffer.length);
              context.buffer = b;
          }
          return context.buffer;
      }
  
      /**
       * Ensure that the buffer has room for <code>size</code> bytes
       *
       * @param size minimum spare space required
       * @param context the context to be used
       * @return the buffer
       */
      protected byte[] ensureBufferSize(final int size, final Context context){
          if ((context.buffer == null) || (context.buffer.length < context.pos + size)){
              return resizeBuffer(context);
          }
          return context.buffer;
      }
  
      /**
       * Extracts buffered data into the provided byte[] array, starting at position bPos, up to a maximum of bAvail
       * bytes. Returns how many bytes were actually extracted.
       * <p>
       * Package protected for access from I/O streams.
       *
       * @param b
       *            byte[] array to extract the buffered data into.
       * @param bPos
       *            position in byte[] array to start extraction at.
       * @param bAvail
       *            amount of bytes we're allowed to extract. We may extract fewer (if fewer are available).
       * @param context
       *            the context to be used
       * @return The number of bytes successfully extracted into the provided byte[] array.
       */
      int readResults(final byte[] b, final int bPos, final int bAvail, final Context context) {
          if (context.buffer != null) {
              final int len = Math.min(available(context), bAvail);
              System.arraycopy(context.buffer, context.readPos, b, bPos, len);
              context.readPos += len;
              if (context.readPos >= context.pos) {
                  context.buffer = null; // so hasData() will return false, and this method can return -1
              }
              return len;
          }
          return context.eof ? EOF : 0;
      }
  
      /**
       * Checks if a byte value is whitespace or not.
       * Whitespace is taken to mean: space, tab, CR, LF
       * @param byteToCheck
       *            the byte to check
       * @return true if byte is whitespace, false otherwise
       */
      protected static boolean isWhiteSpace(final byte byteToCheck) {
          switch (byteToCheck) {
              case ' ' :
              case '\n' :
              case '\r' :
              case '\t' :
                  return true;
              default :
                  return false;
          }
      }
  
      /**
       * Encodes an Object using the Base-N algorithm. This method is provided in order to satisfy the requirements of
       * the Encoder interface, and will throw an EncoderException if the supplied object is not of type byte[].
       *
       * @param obj
       *            Object to encode
       * @return An object (of type byte[]) containing the Base-N encoded data which corresponds to the byte[] supplied.
       * @throws EncoderException
       *             if the parameter supplied is not of type byte[]
       */
      @Override
      public Object encode(final Object obj) throws EncoderException {
          if (!(obj instanceof byte[])) {
              throw new EncoderException("Parameter supplied to Base-N encode is not a byte[]");
          }
          return encode((byte[]) obj);
      }
  
      /**
       * Encodes a byte[] containing binary data, into a String containing characters in the Base-N alphabet.
       * Uses UTF8 encoding.
       *
       * @param pArray
       *            a byte array containing binary data
       * @return A String containing only Base-N character data
       */
      public String encodeToString(final byte[] pArray) {
          return StringUtils.newStringUtf8(encode(pArray));
      }
  
      /**
       * Encodes a byte[] containing binary data, into a String containing characters in the appropriate alphabet.
       * Uses UTF8 encoding.
       *
       * @param pArray a byte array containing binary data
       * @return String containing only character data in the appropriate alphabet.
      */
      public String encodeAsString(final byte[] pArray){
          return StringUtils.newStringUtf8(encode(pArray));
      }
  
      /**
       * Decodes an Object using the Base-N algorithm. This method is provided in order to satisfy the requirements of
       * the Decoder interface, and will throw a DecoderException if the supplied object is not of type byte[] or String.
       *
       * @param obj
       *            Object to decode
       * @return An object (of type byte[]) containing the binary data which corresponds to the byte[] or String
       *         supplied.
       * @throws DecoderException
       *             if the parameter supplied is not of type byte[]
       */
      @Override
      public Object decode(final Object obj) throws DecoderException {
          if (obj instanceof byte[]) {
              return decode((byte[]) obj);
          } else if (obj instanceof String) {
              return decode((String) obj);
          } else {
              throw new DecoderException("Parameter supplied to Base-N decode is not a byte[] or a String");
          }
      }
  
      /**
       * Decodes a String containing characters in the Base-N alphabet.
       *
       * @param pArray
       *            A String containing Base-N character data
       * @return a byte array containing binary data
       */
      public byte[] decode(final String pArray) {
          return decode(StringUtils.getBytesUtf8(pArray));
      }
  
      /**
       * Decodes a byte[] containing characters in the Base-N alphabet.
       *
       * @param pArray
       *            A byte array containing Base-N character data
       * @return a byte array containing binary data
       */
      @Override
      public byte[] decode(final byte[] pArray) {
          if (pArray == null || pArray.length == 0) {
              return pArray;
          }
          final Context context = new Context();
          decode(pArray, 0, pArray.length, context);
          decode(pArray, 0, EOF, context); // Notify decoder of EOF.
          final byte[] result = new byte[context.pos];
          readResults(result, 0, result.length, context);
          return result;
      }
  
      /**
       * Encodes a byte[] containing binary data, into a byte[] containing characters in the alphabet.
       *
       * @param pArray
       *            a byte array containing binary data
       * @return A byte array containing only the base N alphabetic character data
       */
      @Override
      public byte[] encode(final byte[] pArray) {
          if (pArray == null || pArray.length == 0) {
              return pArray;
          }
          return encode(pArray, 0, pArray.length);
      }
  
  	/**
  	 * Encodes a byte[] containing binary data, into a byte[] containing
  	 * characters in the alphabet.
  	 *
  	 * @param pArray
  	 *            a byte array containing binary data
  	 * @param offset
  	 *            initial offset of the subarray.
  	 * @param length
  	 *            length of the subarray.
  	 * @return A byte array containing only the base N alphabetic character data
  	 * @since 1.11
  	 */
      public byte[] encode(final byte[] pArray, int offset, int length) {
          if (pArray == null || pArray.length == 0) {
              return pArray;
          }
          final Context context = new Context();
          encode(pArray, offset, length, context);
          encode(pArray, offset, EOF, context); // Notify encoder of EOF.
          final byte[] buf = new byte[context.pos - context.readPos];
          readResults(buf, 0, buf.length, context);
          return buf;
      }
  
      // package protected for access from I/O streams
      abstract void encode(byte[] pArray, int i, int length, Context context);
  
      // package protected for access from I/O streams
      abstract void decode(byte[] pArray, int i, int length, Context context);
  
      /**
       * Returns whether or not the <code>octet</code> is in the current alphabet.
       * Does not allow whitespace or pad.
       *
       * @param value The value to test
       *
       * @return <code>true</code> if the value is defined in the current alphabet, <code>false</code> otherwise.
       */
      protected abstract boolean isInAlphabet(byte value);
  
      /**
       * Tests a given byte array to see if it contains only valid characters within the alphabet.
       * The method optionally treats whitespace and pad as valid.
       *
       * @param arrayOctet byte array to test
       * @param allowWSPad if <code>true</code>, then whitespace and PAD are also allowed
       *
       * @return <code>true</code> if all bytes are valid characters in the alphabet or if the byte array is empty;
       *         <code>false</code>, otherwise
       */
      public boolean isInAlphabet(final byte[] arrayOctet, final boolean allowWSPad) {
          for (int i = 0; i < arrayOctet.length; i++) {
              if (!isInAlphabet(arrayOctet[i]) &&
                      (!allowWSPad || (arrayOctet[i] != pad) && !isWhiteSpace(arrayOctet[i]))) {
                  return false;
              }
          }
          return true;
      }
  
      /**
       * Tests a given String to see if it contains only valid characters within the alphabet.
       * The method treats whitespace and PAD as valid.
       *
       * @param basen String to test
       * @return <code>true</code> if all characters in the String are valid characters in the alphabet or if
       *         the String is empty; <code>false</code>, otherwise
       * @see #isInAlphabet(byte[], boolean)
       */
      public boolean isInAlphabet(final String basen) {
          return isInAlphabet(StringUtils.getBytesUtf8(basen), true);
      }
  
      /**
       * Tests a given byte array to see if it contains any characters within the alphabet or PAD.
       *
       * Intended for use in checking line-ending arrays
       *
       * @param arrayOctet
       *            byte array to test
       * @return <code>true</code> if any byte is a valid character in the alphabet or PAD; <code>false</code> otherwise
       */
      protected boolean containsAlphabetOrPad(final byte[] arrayOctet) {
          if (arrayOctet == null) {
              return false;
          }
          for (final byte element : arrayOctet) {
              if (pad == element || isInAlphabet(element)) {
                  return true;
              }
          }
          return false;
      }
  
      /**
       * Calculates the amount of space needed to encode the supplied array.
       *
       * @param pArray byte[] array which will later be encoded
       *
       * @return amount of space needed to encoded the supplied array.
       * Returns a long since a max-len array will require &gt; Integer.MAX_VALUE
       */
      public long getEncodedLength(final byte[] pArray) {
          // Calculate non-chunked size - rounded up to allow for padding
          // cast to long is needed to avoid possibility of overflow
          long len = ((pArray.length + unencodedBlockSize-1)  / unencodedBlockSize) * (long) encodedBlockSize;
          if (lineLength > 0) { // We're using chunking
              // Round up to nearest multiple
              len += ((len + lineLength-1) / lineLength) * chunkSeparatorLength;
          }
          return len;
      }
  }