Mega Code Archive
Performs Base-64 decoding on an underlying stream
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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. *
****************************************************************/
import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.BufferUnderflowException;
import java.util.HashSet;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Set;
/**
* Performs Base-64 decoding on an underlying stream.
*/
public class Base64InputStream extends InputStream {
private static final int ENCODED_BUFFER_SIZE = 1536;
private static final int[] BASE64_DECODE = new int[256];
static {
for (int i = 0; i < 256; i++)
BASE64_DECODE[i] = -1;
for (int i = 0; i < Base64OutputStream.BASE64_TABLE.length; i++)
BASE64_DECODE[Base64OutputStream.BASE64_TABLE[i] & 0xff] = i;
}
private static final byte BASE64_PAD = '=';
private static final int EOF = -1;
private final byte[] singleByte = new byte[1];
private boolean strict;
private final InputStream in;
private boolean closed = false;
private final byte[] encoded = new byte[ENCODED_BUFFER_SIZE];
private int position = 0; // current index into encoded buffer
private int size = 0; // current size of encoded buffer
private final ByteQueue q = new ByteQueue();
private boolean eof; // end of file or pad character reached
public Base64InputStream(InputStream in) {
this(in, false);
}
public Base64InputStream(InputStream in, boolean strict) {
if (in == null)
throw new IllegalArgumentException();
this.in = in;
this.strict = strict;
}
@Override
public int read() throws IOException {
if (closed)
throw new IOException("Base64InputStream has been closed");
while (true) {
int bytes = read0(singleByte, 0, 1);
if (bytes == EOF)
return EOF;
if (bytes == 1)
return singleByte[0] & 0xff;
}
}
@Override
public int read(byte[] buffer) throws IOException {
if (closed)
throw new IOException("Base64InputStream has been closed");
if (buffer == null)
throw new NullPointerException();
if (buffer.length == 0)
return 0;
return read0(buffer, 0, buffer.length);
}
@Override
public int read(byte[] buffer, int offset, int length) throws IOException {
if (closed)
throw new IOException("Base64InputStream has been closed");
if (buffer == null)
throw new NullPointerException();
if (offset < 0 || length < 0 || offset + length > buffer.length)
throw new IndexOutOfBoundsException();
if (length == 0)
return 0;
return read0(buffer, offset, offset + length);
}
@Override
public void close() throws IOException {
if (closed)
return;
closed = true;
}
private int read0(final byte[] buffer, final int from, final int to)
throws IOException {
int index = from; // index into given buffer
// check if a previous invocation left decoded bytes in the queue
int qCount = q.count();
while (qCount-- > 0 && index < to) {
buffer[index++] = q.dequeue();
}
// eof or pad reached?
if (eof)
return index == from ? EOF : index - from;
// decode into given buffer
int data = 0; // holds decoded data; up to four sextets
int sextets = 0; // number of sextets
while (index < to) {
// make sure buffer not empty
while (position == size) {
int n = in.read(encoded, 0, encoded.length);
if (n == EOF) {
eof = true;
if (sextets != 0) {
// error in encoded data
handleUnexpectedEof(sextets);
}
return index == from ? EOF : index - from;
} else if (n > 0) {
position = 0;
size = n;
} else {
assert n == 0;
}
}
// decode buffer
while (position < size && index < to) {
int value = encoded[position++] & 0xff;
if (value == BASE64_PAD) {
index = decodePad(data, sextets, buffer, index, to);
return index - from;
}
int decoded = BASE64_DECODE[value];
if (decoded < 0) // -1: not a base64 char
continue;
data = (data << 6) | decoded;
sextets++;
if (sextets == 4) {
sextets = 0;
byte b1 = (byte) (data >>> 16);
byte b2 = (byte) (data >>> 8);
byte b3 = (byte) data;
if (index < to - 2) {
buffer[index++] = b1;
buffer[index++] = b2;
buffer[index++] = b3;
} else {
if (index < to - 1) {
buffer[index++] = b1;
buffer[index++] = b2;
q.enqueue(b3);
} else if (index < to) {
buffer[index++] = b1;
q.enqueue(b2);
q.enqueue(b3);
} else {
q.enqueue(b1);
q.enqueue(b2);
q.enqueue(b3);
}
assert index == to;
return to - from;
}
}
}
}
assert sextets == 0;
assert index == to;
return to - from;
}
private int decodePad(int data, int sextets, final byte[] buffer,
int index, final int end) throws IOException {
eof = true;
if (sextets == 2) {
// one byte encoded as "XY=="
byte b = (byte) (data >>> 4);
if (index < end) {
buffer[index++] = b;
} else {
q.enqueue(b);
}
} else if (sextets == 3) {
// two bytes encoded as "XYZ="
byte b1 = (byte) (data >>> 10);
byte b2 = (byte) ((data >>> 2) & 0xFF);
if (index < end - 1) {
buffer[index++] = b1;
buffer[index++] = b2;
} else if (index < end) {
buffer[index++] = b1;
q.enqueue(b2);
} else {
q.enqueue(b1);
q.enqueue(b2);
}
} else {
// error in encoded data
handleUnexpecedPad(sextets);
}
return index;
}
private void handleUnexpectedEof(int sextets) throws IOException {
if (strict)
throw new IOException("unexpected end of file");
}
private void handleUnexpecedPad(int sextets) throws IOException {
if (strict)
throw new IOException("unexpected padding character");
}
}
class ByteQueue implements Iterable<Byte> {
private UnboundedFifoByteBuffer buf;
private int initialCapacity = -1;
public ByteQueue() {
buf = new UnboundedFifoByteBuffer();
}
public ByteQueue(int initialCapacity) {
buf = new UnboundedFifoByteBuffer(initialCapacity);
this.initialCapacity = initialCapacity;
}
public void enqueue(byte b) {
buf.add(b);
}
public byte dequeue() {
return buf.remove();
}
public int count() {
return buf.size();
}
public void clear() {
if (initialCapacity != -1)
buf = new UnboundedFifoByteBuffer(initialCapacity);
else
buf = new UnboundedFifoByteBuffer();
}
public Iterator<Byte> iterator() {
return buf.iterator();
}
}
/**
* UnboundedFifoByteBuffer is a very efficient buffer implementation.
* According to performance testing, it exhibits a constant access time, but it
* also outperforms ArrayList when used for the same purpose.
* <p>
* The removal order of an <code>UnboundedFifoByteBuffer</code> is based on the insertion
* order; elements are removed in the same order in which they were added.
* The iteration order is the same as the removal order.
* <p>
* The {@link #remove()} and {@link #get()} operations perform in constant time.
* The {@link #add(Object)} operation performs in amortized constant time. All
* other operations perform in linear time or worse.
* <p>
* Note that this implementation is not synchronized. The following can be
* used to provide synchronized access to your <code>UnboundedFifoByteBuffer</code>:
* <pre>
* Buffer fifo = BufferUtils.synchronizedBuffer(new UnboundedFifoByteBuffer());
* </pre>
* <p>
* This buffer prevents null objects from being added.
*
* @since Commons Collections 3.0 (previously in main package v2.1)
*/
class UnboundedFifoByteBuffer {
protected byte[] buffer;
protected int head;
protected int tail;
/**
* Constructs an UnboundedFifoByteBuffer with the default number of elements.
* It is exactly the same as performing the following:
*
* <pre>
* new UnboundedFifoByteBuffer(32);
* </pre>
*/
public UnboundedFifoByteBuffer() {
this(32);
}
/**
* Constructs an UnboundedFifoByteBuffer with the specified number of elements.
* The integer must be a positive integer.
*
* @param initialSize the initial size of the buffer
* @throws IllegalArgumentException if the size is less than 1
*/
public UnboundedFifoByteBuffer(int initialSize) {
if (initialSize <= 0) {
throw new IllegalArgumentException("The size must be greater than 0");
}
buffer = new byte[initialSize + 1];
head = 0;
tail = 0;
}
/**
* Returns the number of elements stored in the buffer.
*
* @return this buffer's size
*/
public int size() {
int size = 0;
if (tail < head) {
size = buffer.length - head + tail;
} else {
size = tail - head;
}
return size;
}
/**
* Returns true if this buffer is empty; false otherwise.
*
* @return true if this buffer is empty
*/
public boolean isEmpty() {
return (size() == 0);
}
/**
* Adds the given element to this buffer.
*
* @param b the byte to add
* @return true, always
*/
public boolean add(final byte b) {
if (size() + 1 >= buffer.length) {
byte[] tmp = new byte[((buffer.length - 1) * 2) + 1];
int j = 0;
for (int i = head; i != tail;) {
tmp[j] = buffer[i];
buffer[i] = 0;
j++;
i++;
if (i == buffer.length) {
i = 0;
}
}
buffer = tmp;
head = 0;
tail = j;
}
buffer[tail] = b;
tail++;
if (tail >= buffer.length) {
tail = 0;
}
return true;
}
/**
* Returns the next object in the buffer.
*
* @return the next object in the buffer
* @throws BufferUnderflowException if this buffer is empty
*/
public byte get() {
if (isEmpty()) {
throw new IllegalStateException("The buffer is already empty");
}
return buffer[head];
}
/**
* Removes the next object from the buffer
*
* @return the removed object
* @throws BufferUnderflowException if this buffer is empty
*/
public byte remove() {
if (isEmpty()) {
throw new IllegalStateException("The buffer is already empty");
}
byte element = buffer[head];
head++;
if (head >= buffer.length) {
head = 0;
}
return element;
}
/**
* Increments the internal index.
*
* @param index the index to increment
* @return the updated index
*/
private int increment(int index) {
index++;
if (index >= buffer.length) {
index = 0;
}
return index;
}
/**
* Decrements the internal index.
*
* @param index the index to decrement
* @return the updated index
*/
private int decrement(int index) {
index--;
if (index < 0) {
index = buffer.length - 1;
}
return index;
}
/**
* Returns an iterator over this buffer's elements.
*
* @return an iterator over this buffer's elements
*/
public Iterator<Byte> iterator() {
return new Iterator<Byte>() {
private int index = head;
private int lastReturnedIndex = -1;
public boolean hasNext() {
return index != tail;
}
public Byte next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
lastReturnedIndex = index;
index = increment(index);
return new Byte(buffer[lastReturnedIndex]);
}
public void remove() {
if (lastReturnedIndex == -1) {
throw new IllegalStateException();
}
// First element can be removed quickly
if (lastReturnedIndex == head) {
UnboundedFifoByteBuffer.this.remove();
lastReturnedIndex = -1;
return;
}
// Other elements require us to shift the subsequent elements
int i = lastReturnedIndex + 1;
while (i != tail) {
if (i >= buffer.length) {
buffer[i - 1] = buffer[0];
i = 0;
} else {
buffer[i - 1] = buffer[i];
i++;
}
}
lastReturnedIndex = -1;
tail = decrement(tail);
buffer[tail] = 0;
index = decrement(index);
}
};
}
}
class Base64OutputStream extends FilterOutputStream {
// Default line length per RFC 2045 section 6.8.
private static final int DEFAULT_LINE_LENGTH = 76;
// CRLF line separator per RFC 2045 section 2.1.
private static final byte[] CRLF_SEPARATOR = { '\r', '\n' };
// This array is a lookup table that translates 6-bit positive integer index
// values into their "Base64 Alphabet" equivalents as specified in Table 1
// of RFC 2045.
static final byte[] BASE64_TABLE = { 'A', 'B', 'C', 'D', 'E', 'F',
'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S',
'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's',
't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5',
'6', '7', '8', '9', '+', '/' };
// Byte used to pad output.
private static final byte BASE64_PAD = '=';
// This set contains all base64 characters including the pad character. Used
// solely to check if a line separator contains any of these characters.
private static final Set<Byte> BASE64_CHARS = new HashSet<Byte>();
static {
for (byte b : BASE64_TABLE) {
BASE64_CHARS.add(b);
}
BASE64_CHARS.add(BASE64_PAD);
}
// Mask used to extract 6 bits
private static final int MASK_6BITS = 0x3f;
private static final int ENCODED_BUFFER_SIZE = 2048;
private final byte[] singleByte = new byte[1];
private final int lineLength;
private final byte[] lineSeparator;
private boolean closed = false;
private final byte[] encoded;
private int position = 0;
private int data = 0;
private int modulus = 0;
private int linePosition = 0;
/**
* Creates a <code>Base64OutputStream</code> that writes the encoded data
* to the given output stream using the default line length (76) and line
* separator (CRLF).
*
* @param out
* underlying output stream.
*/
public Base64OutputStream(OutputStream out) {
this(out, DEFAULT_LINE_LENGTH, CRLF_SEPARATOR);
}
/**
* Creates a <code>Base64OutputStream</code> that writes the encoded data
* to the given output stream using the given line length and the default
* line separator (CRLF).
* <p>
* The given line length will be rounded up to the nearest multiple of 4. If
* the line length is zero then the output will not be split into lines.
*
* @param out
* underlying output stream.
* @param lineLength
* desired line length.
*/
public Base64OutputStream(OutputStream out, int lineLength) {
this(out, lineLength, CRLF_SEPARATOR);
}
/**
* Creates a <code>Base64OutputStream</code> that writes the encoded data
* to the given output stream using the given line length and line
* separator.
* <p>
* The given line length will be rounded up to the nearest multiple of 4. If
* the line length is zero then the output will not be split into lines and
* the line separator is ignored.
* <p>
* The line separator must not include characters from the BASE64 alphabet
* (including the padding character <code>=</code>).
*
* @param out
* underlying output stream.
* @param lineLength
* desired line length.
* @param lineSeparator
* line separator to use.
*/
public Base64OutputStream(OutputStream out, int lineLength,
byte[] lineSeparator) {
super(out);
if (out == null)
throw new IllegalArgumentException();
if (lineLength < 0)
throw new IllegalArgumentException();
checkLineSeparator(lineSeparator);
this.lineLength = lineLength;
this.lineSeparator = new byte[lineSeparator.length];
System.arraycopy(lineSeparator, 0, this.lineSeparator, 0,
lineSeparator.length);
this.encoded = new byte[ENCODED_BUFFER_SIZE];
}
@Override
public final void write(final int b) throws IOException {
if (closed)
throw new IOException("Base64OutputStream has been closed");
singleByte[0] = (byte) b;
write0(singleByte, 0, 1);
}
@Override
public final void write(final byte[] buffer) throws IOException {
if (closed)
throw new IOException("Base64OutputStream has been closed");
if (buffer == null)
throw new NullPointerException();
if (buffer.length == 0)
return;
write0(buffer, 0, buffer.length);
}
@Override
public final void write(final byte[] buffer, final int offset,
final int length) throws IOException {
if (closed)
throw new IOException("Base64OutputStream has been closed");
if (buffer == null)
throw new NullPointerException();
if (offset < 0 || length < 0 || offset + length > buffer.length)
throw new IndexOutOfBoundsException();
if (length == 0)
return;
write0(buffer, offset, offset + length);
}
@Override
public void flush() throws IOException {
if (closed)
throw new IOException("Base64OutputStream has been closed");
flush0();
}
@Override
public void close() throws IOException {
if (closed)
return;
closed = true;
close0();
}
private void write0(final byte[] buffer, final int from, final int to)
throws IOException {
for (int i = from; i < to; i++) {
data = (data << 8) | (buffer[i] & 0xff);
if (++modulus == 3) {
modulus = 0;
// write line separator if necessary
if (lineLength > 0 && linePosition >= lineLength) {
// writeLineSeparator() inlined for performance reasons
linePosition = 0;
if (encoded.length - position < lineSeparator.length)
flush0();
for (byte ls : lineSeparator)
encoded[position++] = ls;
}
// encode data into 4 bytes
if (encoded.length - position < 4)
flush0();
encoded[position++] = BASE64_TABLE[(data >> 18) & MASK_6BITS];
encoded[position++] = BASE64_TABLE[(data >> 12) & MASK_6BITS];
encoded[position++] = BASE64_TABLE[(data >> 6) & MASK_6BITS];
encoded[position++] = BASE64_TABLE[data & MASK_6BITS];
linePosition += 4;
}
}
}
private void flush0() throws IOException {
if (position > 0) {
out.write(encoded, 0, position);
position = 0;
}
}
private void close0() throws IOException {
if (modulus != 0)
writePad();
// write line separator at the end of the encoded data
if (lineLength > 0 && linePosition > 0) {
writeLineSeparator();
}
flush0();
}
private void writePad() throws IOException {
// write line separator if necessary
if (lineLength > 0 && linePosition >= lineLength) {
writeLineSeparator();
}
// encode data into 4 bytes
if (encoded.length - position < 4)
flush0();
if (modulus == 1) {
encoded[position++] = BASE64_TABLE[(data >> 2) & MASK_6BITS];
encoded[position++] = BASE64_TABLE[(data << 4) & MASK_6BITS];
encoded[position++] = BASE64_PAD;
encoded[position++] = BASE64_PAD;
} else {
assert modulus == 2;
encoded[position++] = BASE64_TABLE[(data >> 10) & MASK_6BITS];
encoded[position++] = BASE64_TABLE[(data >> 4) & MASK_6BITS];
encoded[position++] = BASE64_TABLE[(data << 2) & MASK_6BITS];
encoded[position++] = BASE64_PAD;
}
linePosition += 4;
}
private void writeLineSeparator() throws IOException {
linePosition = 0;
if (encoded.length - position < lineSeparator.length)
flush0();
for (byte ls : lineSeparator)
encoded[position++] = ls;
}
private void checkLineSeparator(byte[] lineSeparator) {
if (lineSeparator.length > ENCODED_BUFFER_SIZE)
throw new IllegalArgumentException("line separator length exceeds "
+ ENCODED_BUFFER_SIZE);
for (byte b : lineSeparator) {
if (BASE64_CHARS.contains(b)) {
throw new IllegalArgumentException(
"line separator must not contain base64 character '"
+ (char) (b & 0xff) + "'");
}
}
}
}
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