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/*
* Copyright (C) 2007 The Guava Authors
* Copyright (C) 2014, Sasa Zivkov <sasa.zivkov@sap.com>, SAP AG 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.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import org.eclipse.jgit.internal.JGitText;
/**
* Wraps a {@link java.io.InputStream}, limiting the number of bytes which can
* be read.
*
* This class was copied and modifed from the Google Guava 16.0. Differently
* from the original Guava code, when a caller tries to read from this stream
* past the given limit and the wrapped stream hasn't yet reached its EOF this
* class will call the limitExceeded method instead of returning EOF.
*
* @since 3.3
*/
public abstract class LimitedInputStream extends FilterInputStream {
private long left;
/** Max number of bytes to be read from the wrapped stream */
protected final long limit;
private long mark = -1;
/**
* Create a new LimitedInputStream
*
* @param in an InputStream
* @param limit max number of bytes to read from the InputStream
*/
protected LimitedInputStream(InputStream in, long limit) {
super(in);
left = limit;
this.limit = limit;
}
@Override
public int available() throws IOException {
return (int) Math.min(in.available(), left);
}
// it's okay to mark even if mark isn't supported, as reset won't work
@Override
public synchronized void mark(int readLimit) {
in.mark(readLimit);
mark = left;
}
@Override
public int read() throws IOException {
if (left == 0) {
if (in.available() == 0) {
return -1;
}
limitExceeded();
}
int result = in.read();
if (result != -1) {
--left;
}
return result;
}
@Override
public int read(byte[] b, int off, int len) throws IOException {
if (left == 0) {
if (in.available() == 0) {
return -1;
}
limitExceeded();
}
len = (int) Math.min(len, left);
int result = in.read(b, off, len);
if (result != -1) {
left -= result;
}
return result;
}
@Override
public synchronized void reset() throws IOException {
if (!in.markSupported())
throw new IOException(JGitText.get().unsupportedMark);
if (mark == -1)
throw new IOException(JGitText.get().unsetMark);
in.reset();
left = mark;
}
@Override
public long skip(long n) throws IOException {
n = Math.min(n, left);
long skipped = in.skip(n);
left -= skipped;
return skipped;
}
/**
* Called when trying to read past the given {@link #limit} and the wrapped
* InputStream {@link #in} hasn't yet reached its EOF
*
* @throws java.io.IOException
* subclasses can throw an {@link java.io.IOException} when the
* limit is exceeded. The throws java.io.IOException will be
* forwarded back to the caller of the read method which read
* the stream past the limit.
*/
protected abstract void limitExceeded() throws IOException;
}
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