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/*
* Copyright (C) 2007 The Guava Authors
*
* Licensed 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.
*/
package com.google.common.io;
import com.google.common.annotations.Beta;
import com.google.common.base.Preconditions;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
/**
* An InputStream that limits the number of bytes which can be read.
*
* @author Charles Fry
* @since 1.0
*/
@Beta
public final class LimitInputStream extends FilterInputStream {
private long left;
private long mark = -1;
/**
* Wraps another input stream, limiting the number of bytes which can be read.
*
* @param in the input stream to be wrapped
* @param limit the maximum number of bytes to be read
*/
public LimitInputStream(InputStream in, long limit) {
super(in);
Preconditions.checkNotNull(in);
Preconditions.checkArgument(limit >= 0, "limit must be non-negative");
left = limit;
}
@Override public int available() throws IOException {
return (int) Math.min(in.available(), left);
}
@Override public synchronized void mark(int readlimit) {
in.mark(readlimit);
mark = left;
// it's okay to mark even if mark isn't supported, as reset won't work
}
@Override public int read() throws IOException {
if (left == 0) {
return -1;
}
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) {
return -1;
}
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("Mark not supported");
}
if (mark == -1) {
throw new IOException("Mark not set");
}
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;
}
}
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