/*
 * 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 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/**
 * 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 /** Max number of bytes to be read from the wrapped stream */
	protected final long limit;
	private long mark = -1;

	
Create a new LimitedInputStream
Params:
in – an InputStream
limit – max number of bytes to read from the InputStream/**
	 * 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;
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@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
	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public synchronized void mark(int readLimit) {
		in.mark(readLimit);
		mark = left;
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@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;
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@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;
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@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;
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@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 limit and the wrapped InputStream FilterInputStream.in hasn't yet reached its EOF 
Throws:
IOException –  subclasses can throw an 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./**
	 * 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;
}