/*

  * 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.apache.commons.codec.binary;

 import org.apache.commons.codec.BinaryDecoder;

 import org.apache.commons.codec.BinaryEncoder;

 import org.apache.commons.codec.DecoderException;

 import org.apache.commons.codec.EncoderException;

 /**

  * 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 > 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(), 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

     protected final byte PAD = PAD_DEFAULT; // 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} > 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(int unencodedBlockSize, int encodedBlockSize, int lineLength, int chunkSeparatorLength) {

         this.unencodedBlockSize = unencodedBlockSize;

         this.encodedBlockSize = encodedBlockSize;

         final boolean useChunking = lineLength > 0 && chunkSeparatorLength > 0;

         this.lineLength = useChunking ? (lineLength / encodedBlockSize) * encodedBlockSize : 0;

         this.chunkSeparatorLength = chunkSeparatorLength;

     }

     /**

      * 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(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(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(Context context) {

         if (context.buffer == null) {

             context.buffer = new byte[getDefaultBufferSize()];

             context.pos = 0;

             context.readPos = 0;

         } else {

             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

      */

     protected byte[] ensureBufferSize(int size, 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(byte[] b, int bPos, int bAvail, Context context) {

         if (context.buffer != null) {

             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(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(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(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(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(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(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(byte[] pArray) {

         if (pArray == null || pArray.length == 0) {

             return pArray;

         }

         Context context = new Context();

         decode(pArray, 0, pArray.length, context);

         decode(pArray, 0, EOF, context); // Notify decoder of EOF.

         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 basen alphabetic character data

      */

     @Override

     public byte[] encode(byte[] pArray) {

         if (pArray == null || pArray.length == 0) {

             return pArray;

         }

         Context context = new Context();

         encode(pArray, 0, pArray.length, context);

         encode(pArray, 0, EOF, context); // Notify encoder of EOF.

         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} if the value is defined in the current alphabet, {@code false} 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}, then whitespace and PAD are also allowed

      *

      * @return {@code true} if all bytes are valid characters in the alphabet or if the byte array is empty;

      *         {@code false}, otherwise

      */

     public boolean isInAlphabet(byte[] arrayOctet, 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} if all characters in the String are valid characters in the alphabet or if

      *         the String is empty; {@code false}, otherwise

      * @see #isInAlphabet(byte[], boolean)

      */

     public boolean isInAlphabet(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} if any byte is a valid character in the alphabet or PAD; {@code false} otherwise

      */

     protected boolean containsAlphabetOrPad(byte[] arrayOctet) {

         if (arrayOctet == null) {

             return false;

         }

         for (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 > Integer.MAX_VALUE

      */

     public long getEncodedLength(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;

     }

 }