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/*
* Copyright (C) 2009, 2013 Google Inc. and others
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Distribution License v. 1.0 which is available at
* https://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
package org.eclipse.jgit.util.io;
import java.io.IOException;
import java.io.InputStream;
import java.util.Iterator;
import java.util.LinkedList;
/**
* An InputStream which reads from one or more InputStreams.
* <p>
* This stream may enter into an EOF state, returning -1 from any of the read
* methods, and then later successfully read additional bytes if a new
* InputStream is added after reaching EOF.
* <p>
* Currently this stream does not support the mark/reset APIs. If mark and later
* reset functionality is needed the caller should wrap this stream with a
* {@link java.io.BufferedInputStream}.
*/
public class UnionInputStream extends InputStream {
private static final InputStream EOF = new InputStream() {
@Override
public int read() throws IOException {
return -1;
}
};
private final LinkedList<InputStream> streams = new LinkedList<>();
/**
* Create an empty InputStream that is currently at EOF state.
*/
public UnionInputStream() {
// Do nothing.
}
/**
* Create an InputStream that is a union of the individual streams.
* <p>
* As each stream reaches EOF, it will be automatically closed before bytes
* from the next stream are read.
*
* @param inputStreams
* streams to be pushed onto this stream.
*/
public UnionInputStream(InputStream... inputStreams) {
for (InputStream i : inputStreams)
add(i);
}
private InputStream head() {
return streams.isEmpty() ? EOF : streams.getFirst();
}
private void pop() throws IOException {
if (!streams.isEmpty())
streams.removeFirst().close();
}
/**
* Add the given InputStream onto the end of the stream queue.
* <p>
* When the stream reaches EOF it will be automatically closed.
*
* @param in
* the stream to add; must not be null.
*/
public void add(InputStream in) {
streams.add(in);
}
/**
* Returns true if there are no more InputStreams in the stream queue.
* <p>
* If this method returns {@code true} then all read methods will signal EOF
* by returning -1, until another InputStream has been pushed into the queue
* with {@link #add(InputStream)}.
*
* @return true if there are no more streams to read from.
*/
public boolean isEmpty() {
return streams.isEmpty();
}
@Override
public int read() throws IOException {
for (;;) {
final InputStream in = head();
final int r = in.read();
if (0 <= r)
return r;
else if (in == EOF)
return -1;
else
pop();
}
}
@Override
public int read(byte[] b, int off, int len) throws IOException {
if (len == 0)
return 0;
for (;;) {
final InputStream in = head();
final int n = in.read(b, off, len);
if (0 < n)
return n;
else if (in == EOF)
return -1;
else
pop();
}
}
@Override
public int available() throws IOException {
return head().available();
}
@Override
public long skip(long count) throws IOException {
long skipped = 0;
long cnt = count;
while (0 < cnt) {
final InputStream in = head();
final long n = in.skip(cnt);
if (0 < n) {
skipped += n;
cnt -= n;
} else if (in == EOF) {
return skipped;
} else {
// Is this stream at EOF? We can't tell from skip alone.
// Read one byte to test for EOF, discard it if we aren't
// yet at EOF.
//
final int r = in.read();
if (r < 0) {
pop();
if (0 < skipped)
break;
} else {
skipped += 1;
cnt -= 1;
}
}
}
return skipped;
}
@Override
public void close() throws IOException {
IOException err = null;
for (Iterator<InputStream> i = streams.iterator(); i.hasNext();) {
try {
i.next().close();
} catch (IOException closeError) {
err = closeError;
}
i.remove();
}
if (err != null)
throw err;
}
}
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