BaseNCodec.java
/*
* 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;
import java.util.Arrays;
import org.apache.tomcat.util.buf.HexUtils;
import org.apache.tomcat.util.res.StringManager;
/**
* Abstract superclass for Base-N encoders and decoders.
*
* <p>
* This class is thread-safe.
* </p>
*
* @deprecated Unused. This class will be removed in Tomcat 11 onwards.
*/
@Deprecated
public abstract class BaseNCodec {
protected static final StringManager sm = StringManager.getManager(BaseNCodec.class);
/**
* 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 {
/**
* Placeholder 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;
/**
* 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;
/**
* 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, " +
"modulus=%s, pos=%s, readPos=%s]", this.getClass().getSimpleName(), HexUtils.toHexString(buffer),
currentLinePos, eof, ibitWorkArea, 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;
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 = 128;
/**
* The maximum size buffer to allocate.
*
* <p>This is set to the same size used in the JDK {@link java.util.ArrayList}:</p>
* <blockquote>
* Some VMs reserve some header words in an array.
* Attempts to allocate larger arrays may result in
* OutOfMemoryError: Requested array size exceeds VM limit.
* </blockquote>
*/
private static final int MAX_BUFFER_SIZE = Integer.MAX_VALUE - 8;
/** 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
/**
* Chunk separator per RFC 2045 section 2.1.
*
* @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045 section 2.1</a>
*/
static final byte[] CHUNK_SEPARATOR = {'\r', '\n'};
/**
* Create a positive capacity at least as large the minimum required capacity.
* If the minimum capacity is negative then this throws an OutOfMemoryError as no array
* can be allocated.
*
* @param minCapacity the minimum capacity
* @return the capacity
* @throws OutOfMemoryError if the {@code minCapacity} is negative
*/
private static int createPositiveCapacity(final int minCapacity) {
if (minCapacity < 0) {
// overflow
throw new OutOfMemoryError(sm.getString("base64.outOfMemory", Long.valueOf(minCapacity & 0xffffffffL)));
}
// This is called when we require buffer expansion to a very big array.
// Use the conservative maximum buffer size if possible, otherwise the biggest required.
//
// Note: In this situation JDK 1.8 java.util.ArrayList returns Integer.MAX_VALUE.
// This excludes some VMs that can exceed MAX_BUFFER_SIZE but not allocate a full
// Integer.MAX_VALUE length array.
// The result is that we may have to allocate an array of this size more than once if
// the capacity must be expanded again.
return Math.max(minCapacity, MAX_BUFFER_SIZE);
}
/**
* Increases our buffer by the {@link #DEFAULT_BUFFER_RESIZE_FACTOR}.
* @param context the context to be used
* @param minCapacity the minimum required capacity
* @return the resized byte[] buffer
* @throws OutOfMemoryError if the {@code minCapacity} is negative
*/
private static byte[] resizeBuffer(final Context context, final int minCapacity) {
// Overflow-conscious code treats the min and new capacity as unsigned.
final int oldCapacity = context.buffer.length;
int newCapacity = oldCapacity * DEFAULT_BUFFER_RESIZE_FACTOR;
if (Integer.compareUnsigned(newCapacity, minCapacity) < 0) {
newCapacity = minCapacity;
}
if (Integer.compareUnsigned(newCapacity, MAX_BUFFER_SIZE) > 0) {
newCapacity = createPositiveCapacity(minCapacity);
}
final byte[] b = Arrays.copyOf(context.buffer, newCapacity);
context.buffer = b;
return b;
}
/** Pad byte. Instance variable just in case it needs to vary later. */
protected final byte pad;
/** 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 the 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} is rounded down to the nearest multiple of the encoded block size.
* If {@code chunkSeparatorLength} 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 > 0, use chunking with a length {@code lineLength}
* @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} is rounded down to the nearest multiple of the encoded block size.
* If {@code chunkSeparatorLength} 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 > 0, use chunking with a length {@code lineLength}
* @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 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 hasData(context) ? context.pos - context.readPos : 0;
}
/**
* 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(final byte[] arrayOctet) {
if (arrayOctet == null) {
return false;
}
for (final byte element : arrayOctet) {
if (pad == element || isInAlphabet(element)) {
return true;
}
}
return false;
}
/**
* 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
*/
public byte[] decode(final byte[] pArray) {
return decode(pArray, 0, pArray.length);
}
public byte[] decode(final byte[] pArray, final int off, final int len) {
if (pArray == null || len == 0) {
return new byte[0];
}
final Context context = new Context();
decode(pArray, off, len, context);
decode(pArray, off, EOF, context); // Notify decoder of EOF.
final byte[] result = new byte[context.pos];
readResults(result, 0, result.length, context);
return result;
}
// package protected for access from I/O streams
abstract void decode(byte[] pArray, int i, int length, Context context);
/**
* 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));
}
/**
* 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
*/
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, final int offset, final 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);
/**
* 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.
* @since 1.5
*/
public String encodeAsString(final byte[] pArray){
return StringUtils.newStringUtf8(encode(pArray));
}
/**
* Ensure that the buffer has room for {@code size} 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 = new byte[Math.max(size, getDefaultBufferSize())];
context.pos = 0;
context.readPos = 0;
// Overflow-conscious:
// x + y > z == x + y - z > 0
} else if (context.pos + size - context.buffer.length > 0) {
return resizeBuffer(context, context.pos + size);
}
return context.buffer;
}
/**
* Gets the default buffer size. Can be overridden.
*
* @return the default buffer size.
*/
protected int getDefaultBufferSize() {
return DEFAULT_BUFFER_SIZE;
}
/**
* 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 encode 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 + 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;
}
/**
* 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.pos > context.readPos;
}
/**
* Returns whether or not the {@code octet} 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);
/**
* 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 private for access from I/O streams.
* </p>
*
* @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 (hasData(context)) {
final int len = Math.min(available(context), bAvail);
System.arraycopy(context.buffer, context.readPos, b, bPos, len);
context.readPos += len;
if (!hasData(context)) {
// All data read.
// Reset position markers but do not set buffer to null to allow its reuse.
// hasData(context) will still return false, and this method will return 0 until
// more data is available, or -1 if EOF.
context.pos = context.readPos = 0;
}
return len;
}
return context.eof ? EOF : 0;
}
}