JDK14/Java14源码在线阅读

/*
 * Copyright (c) 2002-2018, the original author or authors.
 *
 * This software is distributable under the BSD license. See the terms of the
 * BSD license in the documentation provided with this software.
 *
 * https://opensource.org/licenses/BSD-3-Clause
 */
package jdk.internal.org.jline.utils;

import java.io.IOException;
import java.io.InputStream;

/**
 * Non blocking input stream
 */
public abstract class NonBlockingInputStream extends InputStream {

    public static final int EOF = -1;
    public static final int READ_EXPIRED = -2;

    /**
     * Reads the next byte of data from the input stream. The value byte is
     * returned as an <code>int</code> in the range <code>0</code> to
     * <code>255</code>. If no byte is available because the end of the stream
     * has been reached, the value <code>-1</code> is returned. This method
     * blocks until input data is available, the end of the stream is detected,
     * or an exception is thrown.
     *
     * @return     the next byte of data, or <code>-1</code> if the end of the
     *             stream is reached.
     * @exception  IOException  if an I/O error occurs.
     */
    @Override
    public int read() throws IOException {
        return read(0L, false);
    }

    /**
     * Peeks to see if there is a byte waiting in the input stream without
     * actually consuming the byte.
     *
     * @param      timeout The amount of time to wait, 0 == forever
     * @return     -1 on eof, -2 if the timeout expired with no available input
     *             or the character that was read (without consuming it).
     * @exception  IOException  if an I/O error occurs.
     */
    public int peek(long timeout) throws IOException {
        return read(timeout, true);
    }

    /**
     * Attempts to read a character from the input stream for a specific
     * period of time.
     *
     * @param      timeout      The amount of time to wait for the character
     * @return     The character read, -1 if EOF is reached,
     *             or -2 if the read timed out.
     * @exception  IOException  if an I/O error occurs.
     */
    public int read(long timeout) throws IOException {
        return read(timeout, false);
    }

    public int read(byte b[], int off, int len) throws IOException {
        if (b == null) {
            throw new NullPointerException();
        } else if (off < 0 || len < 0 || len > b.length - off) {
            throw new IndexOutOfBoundsException();
        } else if (len == 0) {
            return 0;
        }
        int c = read();
        if (c == EOF) {
            return EOF;
        }
        b[off] = (byte)c;
        return 1;
    }

    /**

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