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/*
* Copyright (c) 2008, Harald Kuhr
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* * Neither the name of the copyright holder nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package com.twelvemonkeys.io.enc;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
/**
* An {@code InputStream} that provides on-the-fly decoding from an underlying stream.
*
* @see EncoderStream
* @see Decoder
*
* @author Harald Kuhr
* @version $Id: //depot/branches/personal/haraldk/twelvemonkeys/release-2/twelvemonkeys-core/src/main/java/com/twelvemonkeys/io/enc/DecoderStream.java#2 $
*/
public final class DecoderStream extends FilterInputStream {
protected final ByteBuffer buffer;
protected final Decoder decoder;
/**
* Creates a new decoder stream and chains it to the
* input stream specified by the {@code pStream} argument.
* The stream will use a default decode buffer size.
*
* @param pStream the underlying input stream.
* @param pDecoder the decoder that will be used to decode the underlying stream
*
* @see java.io.FilterInputStream#in
*/
public DecoderStream(final InputStream pStream, final Decoder pDecoder) {
// TODO: Let the decoder decide preferred buffer size
this(pStream, pDecoder, 1024);
}
/**
* Creates a new decoder stream and chains it to the
* input stream specified by the {@code pStream} argument.
*
* @param pStream the underlying input stream.
* @param pDecoder the decoder that will be used to decode the underlying stream
* @param pBufferSize the size of the decode buffer
*
* @see java.io.FilterInputStream#in
*/
public DecoderStream(final InputStream pStream, final Decoder pDecoder, final int pBufferSize) {
super(pStream);
decoder = pDecoder;
buffer = ByteBuffer.allocate(pBufferSize);
buffer.flip();
}
public int available() throws IOException {
return buffer.remaining();
}
public int read() throws IOException {
if (!buffer.hasRemaining()) {
if (fill() < 0) {
return -1;
}
}
return buffer.get() & 0xff;
}
public int read(final byte pBytes[], final int pOffset, final int pLength) throws IOException {
if (pBytes == null) {
throw new NullPointerException();
}
else if ((pOffset < 0) || (pOffset > pBytes.length) || (pLength < 0) ||
((pOffset + pLength) > pBytes.length) || ((pOffset + pLength) < 0)) {
throw new IndexOutOfBoundsException("bytes.length=" + pBytes.length + " offset=" + pOffset + " length=" + pLength);
}
else if (pLength == 0) {
return 0;
}
// End of file?
if (!buffer.hasRemaining()) {
if (fill() < 0) {
return -1;
}
}
// Read until we have read pLength bytes, or have reached EOF
int count = 0;
int off = pOffset;
while (pLength > count) {
if (!buffer.hasRemaining()) {
if (fill() < 0) {
break;
}
}
// Copy as many bytes as possible
int dstLen = Math.min(pLength - count, buffer.remaining());
buffer.get(pBytes, off, dstLen);
// Update offset (rest)
off += dstLen;
// Increase count
count += dstLen;
}
return count;
}
public long skip(final long pLength) throws IOException {
// End of file?
if (!buffer.hasRemaining()) {
if (fill() < 0) {
return 0; // Yes, 0, not -1
}
}
// Skip until we have skipped pLength bytes, or have reached EOF
long total = 0;
while (total < pLength) {
if (!buffer.hasRemaining()) {
if (fill() < 0) {
break;
}
}
// NOTE: Skipped can never be more than avail, which is an int, so the cast is safe
int skipped = (int) Math.min(pLength - total, buffer.remaining());
buffer.position(buffer.position() + skipped);
total += skipped;
}
return total;
}
/**
* Fills the buffer, by decoding data from the underlying input stream.
*
* @return the number of bytes decoded, or {@code -1} if the end of the
* file is reached
*
* @throws IOException if an I/O error occurs
*/
protected int fill() throws IOException {
buffer.clear();
int read = decoder.decode(in, buffer);
// TODO: Enforce this in test case, leave here to aid debugging
if (read > buffer.capacity()) {
throw new AssertionError(
String.format(
"Decode beyond buffer (%d): %d (using %s decoder)",
buffer.capacity(), read, decoder.getClass().getName()
)
);
}
buffer.flip();
if (read == 0) {
return -1;
}
return read;
}
}
