/*
* $HeadURL: http://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk/module-main/src/main/java/org/apache/http/impl/io/ContentLengthInputStream.java $
* $Revision: 652091 $
* $Date: 2008-04-29 13:41:07 -0700 (Tue, 29 Apr 2008) $
*
* ====================================================================
* 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.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* <http://www.apache.org/>.
*
*/
package org.apache.http.impl.io;
import java.io.IOException;
import java.io.InputStream;
import org.apache.http.io.SessionInputBuffer;
/**
* Stream that cuts off after a specified number of bytes.
* Note that this class NEVER closes the underlying stream, even when close
* gets called. Instead, it will read until the "end" of its chunking on
* close, which allows for the seamless execution of subsequent HTTP 1.1
* requests, while not requiring the client to remember to read the entire
* contents of the response.
*
* <p>Implementation note: Choices abound. One approach would pass
* through the {@link InputStream#mark} and {@link InputStream#reset} calls to
* the underlying stream. That's tricky, though, because you then have to
* start duplicating the work of keeping track of how much a reset rewinds.
* Further, you have to watch out for the "readLimit", and since the semantics
* for the readLimit leave room for differing implementations, you might get
* into a lot of trouble.</p>
*
* <p>Alternatively, you could make this class extend
* {@link java.io.BufferedInputStream}
* and then use the protected members of that class to avoid duplicated effort.
* That solution has the side effect of adding yet another possible layer of
* buffering.</p>
*
* <p>Then, there is the simple choice, which this takes - simply don't
* support {@link InputStream#mark} and {@link InputStream#reset}. That choice
* has the added benefit of keeping this class very simple.</p>
*
* @author Ortwin Glueck
* @author Eric Johnson
* @author <a href="mailto:mbowler@GargoyleSoftware.com">Mike Bowler</a>
*
* @since 4.0
*/
public class ContentLengthInputStream extends InputStream {
private static final int BUFFER_SIZE = 2048;
/**
* The maximum number of bytes that can be read from the stream. Subsequent
* read operations will return -1.
*/
private long contentLength;
/** The current position */
private long pos = 0;
/** True if the stream is closed. */
private boolean closed = false;
/**
* Wrapped input stream that all calls are delegated to.
*/
private SessionInputBuffer in = null;
/**
* Creates a new length limited stream
*
* @param in The session input buffer to wrap
* @param contentLength The maximum number of bytes that can be read from
* the stream. Subsequent read operations will return -1.
*/
public ContentLengthInputStream(final SessionInputBuffer in, long contentLength) {
super();
if (in == null) {
throw new IllegalArgumentException("Input stream may not be null");
}
if (contentLength < 0) {
throw new IllegalArgumentException("Content length may not be negative");
}
this.in = in;
this.contentLength = contentLength;
}
/**
* <p>Reads until the end of the known length of content.</p>
*
* <p>Does not close the underlying socket input, but instead leaves it
* primed to parse the next response.</p>
* @throws IOException If an IO problem occurs.
*/
public void close() throws IOException {
if (!closed) {
try {
byte buffer[] = new byte[BUFFER_SIZE];
while (read(buffer) >= 0) {
}
} finally {
// close after above so that we don't throw an exception trying
// to read after closed!
closed = true;
}
}
}
/**
* Read the next byte from the stream
* @return The next byte or -1 if the end of stream has been reached.
* @throws IOException If an IO problem occurs
* @see java.io.InputStream#read()
*/
public int read() throws IOException {
if (closed) {
throw new IOException("Attempted read from closed stream.");
}
if (pos >= contentLength) {
return -1;
}
pos++;
return this.in.read();
}
/**
* Does standard {@link InputStream#read(byte[], int, int)} behavior, but
* also notifies the watcher when the contents have been consumed.
*
* @param b The byte array to fill.
* @param off Start filling at this position.
* @param len The number of bytes to attempt to read.
* @return The number of bytes read, or -1 if the end of content has been
* reached.
*
* @throws java.io.IOException Should an error occur on the wrapped stream.
*/
public int read (byte[] b, int off, int len) throws java.io.IOException {
if (closed) {
throw new IOException("Attempted read from closed stream.");
}
if (pos >= contentLength) {
return -1;
}
if (pos + len > contentLength) {
len = (int) (contentLength - pos);
}
int count = this.in.read(b, off, len);
pos += count;
return count;
}
/**
* Read more bytes from the stream.
* @param b The byte array to put the new data in.
* @return The number of bytes read into the buffer.
* @throws IOException If an IO problem occurs
* @see java.io.InputStream#read(byte[])
*/
public int read(byte[] b) throws IOException {
return read(b, 0, b.length);
}
/**
* Skips and discards a number of bytes from the input stream.
* @param n The number of bytes to skip.
* @return The actual number of bytes skipped. <= 0 if no bytes
* are skipped.
* @throws IOException If an error occurs while skipping bytes.
* @see InputStream#skip(long)
*/
public long skip(long n) throws IOException {
if (n <= 0) {
return 0;
}
byte[] buffer = new byte[BUFFER_SIZE];
// make sure we don't skip more bytes than are
// still available
long remaining = Math.min(n, this.contentLength - this.pos);
// skip and keep track of the bytes actually skipped
long count = 0;
while (remaining > 0) {
int l = read(buffer, 0, (int)Math.min(BUFFER_SIZE, remaining));
if (l == -1) {
break;
}
count += l;
remaining -= l;
}
this.pos += count;
return count;
}
}
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