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  /*
   * 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.tomcat.util.codec.binary;
 
Abstract superclass for Base-N encoders and decoders.

This class is thread-safe.

Version:
$Id: BaseNCodec.java 1459390 2013-03-21 16:38:39Z markt $
 
 public abstract class BaseNCodec implements BinaryEncoderBinaryDecoder {

    
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.)

Returns:
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(), ,
                    );
        }
    }

    
EOF

Since:
1.7
    static final int EOF = -1;

    
MIME chunk size per RFC 2045 section 6.8.

The character limit does not count the trailing CRLF, but counts all other characters, including any equal signs.

See also:
RFC 2045 section 6.8
    public static final int MIME_CHUNK_SIZE = 76;

    
PEM chunk size per RFC 1421 section 4.3.2.4.

The character limit does not count the trailing CRLF, but counts all other characters, including any equal signs.

See also:
RFC 1421 section 4.3.2.4
    public static final int PEM_CHUNK_SIZE = 64;
    private static final int DEFAULT_BUFFER_RESIZE_FACTOR = 2;

    
Defines the default buffer size - currently - must be large enough for at least one encoded block+separator
    private static final int DEFAULT_BUFFER_SIZE = 128;

    
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 = // 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 lineLength > 0.
    private final int chunkSeparatorLength;

    
Note lineLength is rounded down to the nearest multiple of encodedBlockSize If chunkSeparatorLength is zero, then chunking is disabled.

Parameters:
unencodedBlockSize the size of an unencoded block (e.g. Base64 = 3)
encodedBlockSize the size of an encoded block (e.g. Base64 = 4)
lineLength if > 0, use chunking with a length lineLength
chunkSeparatorLength the chunk separator length, if relevant
    protected BaseNCodec(final int unencodedBlockSizefinal int encodedBlockSize,
                         final int lineLengthfinal int chunkSeparatorLength) {
        this. = unencodedBlockSize;
        this. = encodedBlockSize;
        final boolean useChunking = lineLength > 0 && chunkSeparatorLength > 0;
        this. = useChunking ? (lineLength / encodedBlockSize) * encodedBlockSize : 0;
        this. = chunkSeparatorLength;
    }

    
Returns true if this object has buffered data for reading.

Parameters:
context the context to be used
Returns:
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.

Parameters:
context the context to be used
Returns:
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.

    protected int getDefaultBufferSize() {
        return ;
    }

    
Increases our buffer by the DEFAULT_BUFFER_RESIZE_FACTOR.

Parameters:
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 * ];
            System.arraycopy(context.buffer, 0, b, 0, context.buffer.length);
            context.buffer = b;
        }
        return context.buffer;
    }

    
Ensure that the buffer has room for size bytes

Parameters:
size minimum spare space required
context the context to be used
    protected byte[] ensureBufferSize(final int sizefinal 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.

Package protected for access from I/O streams.

Parameters:
b byte[] array to extract the buffered data into.
bPos position in byte[] array to start extraction at.
bAvail amount of bytes we're allowed to extract. We may extract fewer (if fewer are available).
context the context to be used
Returns:
The number of bytes successfully extracted into the provided byte[] array.
    int readResults(final byte[] bfinal int bPosfinal int bAvailfinal Context context) {
        if (context.buffer != null) {
            final int len = Math.min(available(context), bAvail);
            System.arraycopy(context.buffercontext.readPosbbPoslen);
            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 ?  : 0;
    }

    
Checks if a byte value is whitespace or not. Whitespace is taken to mean: space, tab, CR, LF

Parameters:
byteToCheck the byte to check
Returns:
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[].

Parameters:
obj Object to encode
Returns:
An object (of type byte[]) containing the Base-N encoded data which corresponds to the byte[] supplied.
Throws:
org.apache.tomcat.util.codec.EncoderException if the parameter supplied is not of type byte[]
    @Override
    public Object encode(final Object objthrows 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.

Parameters:
pArray a byte array containing binary data
Returns:
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.

Parameters:
pArray a byte array containing binary data
Returns:
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.

Parameters:
obj Object to decode
Returns:
An object (of type byte[]) containing the binary data which corresponds to the byte[] or String supplied.
Throws:
org.apache.tomcat.util.codec.DecoderException if the parameter supplied is not of type byte[]
    @Override
    public Object decode(final Object objthrows DecoderException {
        if (obj instanceof byte[]) {
            return decode((byte[]) obj);
        } else if (obj instanceof String) {
            return decode((Stringobj);
        } 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.

Parameters:
pArray A String containing Base-N character data
Returns:
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.

Parameters:
pArray A byte array containing Base-N character data
Returns:
a byte array containing binary data
    @Override
    public byte[] decode(final byte[] pArray) {
        return decode(pArray, 0, pArray.length);
    }
    public byte[] decode(final byte[] pArrayfinal int offfinal int len) {
        if (pArray == null || len == 0) {
            return new byte[0];
        }
        final Context context = new Context();
        decode(pArrayofflencontext);
        decode(pArrayoffcontext); // Notify decoder of EOF.
        final byte[] result = new byte[context.pos];
        readResults(result, 0, result.lengthcontext);
        return result;
    }

    
Encodes a byte[] containing binary data, into a byte[] containing characters in the alphabet.

Parameters:
pArray a byte array containing binary data
Returns:
A byte array containing only the basen alphabetic character data
    @Override
    public byte[] encode(final byte[] pArray) {
        if (pArray == null || pArray.length == 0) {
            return pArray;
        }
        final Context context = new Context();
        encode(pArray, 0, pArray.lengthcontext);
        encode(pArray, 0, context); // Notify encoder of EOF.
        final byte[] buf = new byte[context.pos - context.readPos];
        readResults(buf, 0, buf.lengthcontext);
        return buf;
    }
    // package protected for access from I/O streams
    abstract void encode(byte[] pArrayint iint lengthContext context);
    // package protected for access from I/O streams
    abstract void decode(byte[] pArrayint iint lengthContext context);

    
Returns whether or not the octet is in the current alphabet. Does not allow whitespace or pad.

Parameters:
value The value to test
Returns:
true if the value is defined in the current alphabet, 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.

Parameters:
arrayOctet byte array to test
allowWSPad if true, then whitespace and PAD are also allowed
Returns:
true if all bytes are valid characters in the alphabet or if the byte array is empty; false, otherwise
    public boolean isInAlphabet(final byte[] arrayOctetfinal boolean allowWSPad) {
        for (int i = 0; i < arrayOctet.lengthi++) {
            if (!isInAlphabet(arrayOctet[i]) &&
                    (!allowWSPad || (arrayOctet[i] != ) && !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.

Parameters:
basen String to test
Returns:
true if all characters in the String are valid characters in the alphabet or if the String is empty; false, otherwise
See also:
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

Parameters:
arrayOctet byte array to test
Returns:
true if any byte is a valid character in the alphabet or PAD; false otherwise
    protected boolean containsAlphabetOrPad(final byte[] arrayOctet) {
        if (arrayOctet == null) {
            return false;
        }
        for (final byte element : arrayOctet) {
            if ( == element || isInAlphabet(element)) {
                return true;
            }
        }
        return false;
    }

    
Calculates the amount of space needed to encode the supplied array.

Parameters:
pArray byte[] array which will later be encoded
Returns:
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(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 + -1)  / ) * (long;
        if ( > 0) { // We're using chunking
            // Round up to nearest multiple
            len += ((len + -1) / ) * ;
        }
        return len;
    }
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