/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package java.io;

import java.util.Arrays;

import java.util.Objects;

/**

 * This abstract class is the superclass of all classes representing

 * an input stream of bytes.

 *

 * <p> Applications that need to define a subclass of <code>InputStream</code>

 * must always provide a method that returns the next byte of input.

 *

 * @author  Arthur van Hoff

 * @see     java.io.BufferedInputStream

 * @see     java.io.ByteArrayInputStream

 * @see     java.io.DataInputStream

 * @see     java.io.FilterInputStream

 * @see     java.io.InputStream#read()

 * @see     java.io.OutputStream

 * @see     java.io.PushbackInputStream

 * @since   1.0

 */

public abstract class InputStream implements Closeable {

    // MAX_SKIP_BUFFER_SIZE is used to determine the maximum buffer size to

    // use when skipping.

    private static final int MAX_SKIP_BUFFER_SIZE = 2048;

    private static final int DEFAULT_BUFFER_SIZE = 8192;

    /**

     * 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.

     *

     * <p> A subclass must provide an implementation of this method.

     *

     * @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.

     */

    public abstract int read() throws IOException;

    /**

     * Reads some number of bytes from the input stream and stores them into

     * the buffer array <code>b</code>. The number of bytes actually read is

     * returned as an integer.  This method blocks until input data is

     * available, end of file is detected, or an exception is thrown.

     *

     * <p> If the length of <code>b</code> is zero, then no bytes are read and

     * <code>0</code> is returned; otherwise, there is an attempt to read at

     * least one byte. If no byte is available because the stream is at the

     * end of the file, the value <code>-1</code> is returned; otherwise, at

     * least one byte is read and stored into <code>b</code>.

     *

     * <p> The first byte read is stored into element <code>b[0]</code>, the

     * next one into <code>b[1]</code>, and so on. The number of bytes read is,

     * at most, equal to the length of <code>b</code>. Let <i>k</i> be the

     * number of bytes actually read; these bytes will be stored in elements

     * <code>b[0]</code> through <code>b[</code><i>k</i><code>-1]</code>,

     * leaving elements <code>b[</code><i>k</i><code>]</code> through

     * <code>b[b.length-1]</code> unaffected.

     *

     * <p> The <code>read(b)</code> method for class <code>InputStream</code>

     * has the same effect as: <pre><code> read(b, 0, b.length) </code></pre>

     *

     * @param      b   the buffer into which the data is read.

     * @return     the total number of bytes read into the buffer, or

     *             <code>-1</code> if there is no more data because the end of

     *             the stream has been reached.

     * @exception  IOException  If the first byte cannot be read for any reason

     * other than the end of the file, if the input stream has been closed, or

     * if some other I/O error occurs.

     * @exception  NullPointerException  if <code>b</code> is <code>null</code>.

     * @see        java.io.InputStream#read(byte[], int, int)

     */

    public int read(byte b[]) throws IOException {

        return read(b, 0, b.length);

    }

    /**

     * Reads up to <code>len</code> bytes of data from the input stream into

     * an array of bytes.  An attempt is made to read as many as

     * <code>len</code> bytes, but a smaller number may be read.

     * The number of bytes actually read is returned as an integer.

     *

     * <p> This method blocks until input data is available, end of file is

     * detected, or an exception is thrown.

     *

     * <p> If <code>len</code> is zero, then no bytes are read and

     * <code>0</code> is returned; otherwise, there is an attempt to read at

     * least one byte. If no byte is available because the stream is at end of

     * file, the value <code>-1</code> is returned; otherwise, at least one

     * byte is read and stored into <code>b</code>.

     *

     * <p> The first byte read is stored into element <code>b[off]</code>, the

     * next one into <code>b[off+1]</code>, and so on. The number of bytes read

     * is, at most, equal to <code>len</code>. Let <i>k</i> be the number of

     * bytes actually read; these bytes will be stored in elements

     * <code>b[off]</code> through <code>b[off+</code><i>k</i><code>-1]</code>,

     * leaving elements <code>b[off+</code><i>k</i><code>]</code> through

     * <code>b[off+len-1]</code> unaffected.

     *

     * <p> In every case, elements <code>b[0]</code> through

     * <code>b[off]</code> and elements <code>b[off+len]</code> through

     * <code>b[b.length-1]</code> are unaffected.

     *

     * <p> The <code>read(b,</code> <code>off,</code> <code>len)</code> method

     * for class <code>InputStream</code> simply calls the method

     * <code>read()</code> repeatedly. If the first such call results in an

     * <code>IOException</code>, that exception is returned from the call to

     * the <code>read(b,</code> <code>off,</code> <code>len)</code> method.  If

     * any subsequent call to <code>read()</code> results in a

     * <code>IOException</code>, the exception is caught and treated as if it

     * were end of file; the bytes read up to that point are stored into

     * <code>b</code> and the number of bytes read before the exception

     * occurred is returned. The default implementation of this method blocks

     * until the requested amount of input data <code>len</code> has been read,

     * end of file is detected, or an exception is thrown. Subclasses are encouraged

     * to provide a more efficient implementation of this method.

     *

     * @param      b     the buffer into which the data is read.

     * @param      off   the start offset in array <code>b</code>

     *                   at which the data is written.

     * @param      len   the maximum number of bytes to read.

     * @return     the total number of bytes read into the buffer, or

     *             <code>-1</code> if there is no more data because the end of

     *             the stream has been reached.

     * @exception  IOException If the first byte cannot be read for any reason

     * other than end of file, or if the input stream has been closed, or if

     * some other I/O error occurs.

     * @exception  NullPointerException If <code>b</code> is <code>null</code>.

     * @exception  IndexOutOfBoundsException If <code>off</code> is negative,

     * <code>len</code> is negative, or <code>len</code> is greater than

     * <code>b.length - off</code>

     * @see        java.io.InputStream#read()

     */

    public int read(byte b[], int off, int len) throws IOException {

            return 0;

        }

        int c = read();

        if (c == -1) {

            return -1;

        }

        b[off] = (byte)c;

        int i = 1;

        try {

            for (; i < len ; i++) {

                c = read();

                if (c == -1) {

                    break;

                }

                b[off + i] = (byte)c;

            }

        } catch (IOException ee) {

        }

        return i;

    }

    /**

     * The maximum size of array to allocate.

     * Some VMs reserve some header words in an array.

     * Attempts to allocate larger arrays may result in

     * OutOfMemoryError: Requested array size exceeds VM limit

     */

    private static final int MAX_BUFFER_SIZE = Integer.MAX_VALUE - 8;

    /**

     * Reads all remaining bytes from the input stream. This method blocks until

     * all remaining bytes have been read and end of stream is detected, or an

     * exception is thrown. This method does not close the input stream.

     *

     * <p> When this stream reaches end of stream, further invocations of this

     * method will return an empty byte array.

     *

     * <p> Note that this method is intended for simple cases where it is

     * convenient to read all bytes into a byte array. It is not intended for

     * reading input streams with large amounts of data.

     *

     * <p> The behavior for the case where the input stream is <i>asynchronously

     * closed</i>, or the thread interrupted during the read, is highly input

     * stream specific, and therefore not specified.

     *

     * <p> If an I/O error occurs reading from the input stream, then it may do

     * so after some, but not all, bytes have been read. Consequently the input

     * stream may not be at end of stream and may be in an inconsistent state.

     * It is strongly recommended that the stream be promptly closed if an I/O

     * error occurs.

     *

     * @return a byte array containing the bytes read from this input stream

     * @throws IOException if an I/O error occurs

     * @throws OutOfMemoryError if an array of the required size cannot be

     *         allocated. For example, if an array larger than {@code 2GB} would

     *         be required to store the bytes.

     *

     * @since 9

     */

    public byte[] readAllBytes() throws IOException {

        byte[] buf = new byte[DEFAULT_BUFFER_SIZE];

        int capacity = buf.length;

        int nread = 0;

        int n;

        for (;;) {

            // read to EOF which may read more or less than initial buffer size

            while ((n = read(buf, nread, capacity - nread)) > 0)

                nread += n;

            // if the last call to read returned -1, then we're done

            if (n < 0)

                break;

            // need to allocate a larger buffer

            if (capacity <= MAX_BUFFER_SIZE - capacity) {

                capacity = capacity << 1;

            } else {

                if (capacity == MAX_BUFFER_SIZE)

                    throw new OutOfMemoryError("Required array size too large");

                capacity = MAX_BUFFER_SIZE;

            }

            buf = Arrays.copyOf(buf, capacity);

        }

        return (capacity == nread) ? buf : Arrays.copyOf(buf, nread);

    }

    /**

     * Reads the requested number of bytes from the input stream into the given

     * byte array. This method blocks until {@code len} bytes of input data have

     * been read, end of stream is detected, or an exception is thrown. The

     * number of bytes actually read, possibly zero, is returned. This method

     * does not close the input stream.

     *

     * <p> In the case where end of stream is reached before {@code len} bytes

     * have been read, then the actual number of bytes read will be returned.

     * When this stream reaches end of stream, further invocations of this

     * method will return zero.

     *

     * <p> If {@code len} is zero, then no bytes are read and {@code 0} is

     * returned; otherwise, there is an attempt to read up to {@code len} bytes.

     *

     * <p> The first byte read is stored into element {@code b[off]}, the next

     * one in to {@code b[off+1]}, and so on. The number of bytes read is, at

     * most, equal to {@code len}. Let <i>k</i> be the number of bytes actually

     * read; these bytes will be stored in elements {@code b[off]} through

     * {@code b[off+}<i>k</i>{@code -1]}, leaving elements {@code b[off+}<i>k</i>

     * {@code ]} through {@code b[off+len-1]} unaffected.

     *

     * <p> The behavior for the case where the input stream is <i>asynchronously

     * closed</i>, or the thread interrupted during the read, is highly input

     * stream specific, and therefore not specified.

     *

     * <p> If an I/O error occurs reading from the input stream, then it may do

     * so after some, but not all, bytes of {@code b} have been updated with

     * data from the input stream. Consequently the input stream and {@code b}

     * may be in an inconsistent state. It is strongly recommended that the

     * stream be promptly closed if an I/O error occurs.

     *

     * @param  b the byte array into which the data is read

     * @param  off the start offset in {@code b} at which the data is written

     * @param  len the maximum number of bytes to read

     * @return the actual number of bytes read into the buffer

     * @throws IOException if an I/O error occurs

     * @throws NullPointerException if {@code b} is {@code null}

     * @throws IndexOutOfBoundsException If {@code off} is negative, {@code len}

     *         is negative, or {@code len} is greater than {@code b.length - off}

     *

     * @since 9

     */

    public int readNBytes(byte[] b, int off, int len) throws IOException {

        Objects.requireNonNull(b);

        int n = 0;

        while (n < len) {

            int count = read(b, off + n, len - n);

            if (count < 0)

                break;

            n += count;

        }

        return n;

    }

    /**

     * Skips over and discards <code>n</code> bytes of data from this input

     * stream. The <code>skip</code> method may, for a variety of reasons, end

     * up skipping over some smaller number of bytes, possibly <code>0</code>.

     * This may result from any of a number of conditions; reaching end of file

     * before <code>n</code> bytes have been skipped is only one possibility.

     * The actual number of bytes skipped is returned. If {@code n} is

     * negative, the {@code skip} method for class {@code InputStream} always

     * returns 0, and no bytes are skipped. Subclasses may handle the negative

     * value differently.

     *

     * <p> The <code>skip</code> method implementation of this class creates a

     * byte array and then repeatedly reads into it until <code>n</code> bytes

     * have been read or the end of the stream has been reached. Subclasses are

     * encouraged to provide a more efficient implementation of this method.

     * For instance, the implementation may depend on the ability to seek.

     *

     * @param      n   the number of bytes to be skipped.

     * @return     the actual number of bytes skipped.

     * @throws     IOException  if an I/O error occurs.

     */

    public long skip(long n) throws IOException {

        long remaining = n;

        int nr;

        if (n <= 0) {

            return 0;

        }

        int size = (int)Math.min(MAX_SKIP_BUFFER_SIZE, remaining);

        byte[] skipBuffer = new byte[size];

        while (remaining > 0) {

            nr = read(skipBuffer, 0, (int)Math.min(size, remaining));

            if (nr < 0) {

                break;

            }

            remaining -= nr;

        }

        return n - remaining;

    }

    /**

     * Returns an estimate of the number of bytes that can be read (or

     * skipped over) from this input stream without blocking by the next

     * invocation of a method for this input stream. The next invocation

     * might be the same thread or another thread.  A single read or skip of this

     * many bytes will not block, but may read or skip fewer bytes.

     *

     * <p> Note that while some implementations of {@code InputStream} will return

     * the total number of bytes in the stream, many will not.  It is

     * never correct to use the return value of this method to allocate

     * a buffer intended to hold all data in this stream.

     *

     * <p> A subclass' implementation of this method may choose to throw an

     * {@link IOException} if this input stream has been closed by

     * invoking the {@link #close()} method.

     *

     * <p> The {@code available} method for class {@code InputStream} always

     * returns {@code 0}.

     *

     * <p> This method should be overridden by subclasses.

     *

     * @return     an estimate of the number of bytes that can be read (or skipped

     *             over) from this input stream without blocking or {@code 0} when

     *             it reaches the end of the input stream.

     * @exception  IOException if an I/O error occurs.

     */

    public int available() throws IOException {

        return 0;

    }

    /**

     * Closes this input stream and releases any system resources associated

     * with the stream.

     *

     * <p> The <code>close</code> method of <code>InputStream</code> does

     * nothing.

     *

     * @exception  IOException  if an I/O error occurs.

     */

    public void close() throws IOException {}

    /**

     * Marks the current position in this input stream. A subsequent call to

     * the <code>reset</code> method repositions this stream at the last marked

     * position so that subsequent reads re-read the same bytes.

     *

     * <p> The <code>readlimit</code> arguments tells this input stream to

     * allow that many bytes to be read before the mark position gets

     * invalidated.

     *

     * <p> The general contract of <code>mark</code> is that, if the method

     * <code>markSupported</code> returns <code>true</code>, the stream somehow

     * remembers all the bytes read after the call to <code>mark</code> and

     * stands ready to supply those same bytes again if and whenever the method

     * <code>reset</code> is called.  However, the stream is not required to

     * remember any data at all if more than <code>readlimit</code> bytes are

     * read from the stream before <code>reset</code> is called.

     *

     * <p> Marking a closed stream should not have any effect on the stream.

     *

     * <p> The <code>mark</code> method of <code>InputStream</code> does

     * nothing.

     *

     * @param   readlimit   the maximum limit of bytes that can be read before

     *                      the mark position becomes invalid.

     * @see     java.io.InputStream#reset()

     */

    public synchronized void mark(int readlimit) {}

    /**

     * Repositions this stream to the position at the time the

     * <code>mark</code> method was last called on this input stream.

     *

     * <p> The general contract of <code>reset</code> is:

     *

     * <ul>

     * <li> If the method <code>markSupported</code> returns

     * <code>true</code>, then:

     *

     *     <ul><li> If the method <code>mark</code> has not been called since

     *     the stream was created, or the number of bytes read from the stream

     *     since <code>mark</code> was last called is larger than the argument

     *     to <code>mark</code> at that last call, then an

     *     <code>IOException</code> might be thrown.

     *

     *     <li> If such an <code>IOException</code> is not thrown, then the

     *     stream is reset to a state such that all the bytes read since the

     *     most recent call to <code>mark</code> (or since the start of the

     *     file, if <code>mark</code> has not been called) will be resupplied

     *     to subsequent callers of the <code>read</code> method, followed by

     *     any bytes that otherwise would have been the next input data as of

     *     the time of the call to <code>reset</code>. </ul>

     *

     * <li> If the method <code>markSupported</code> returns

     * <code>false</code>, then:

     *

     *     <ul><li> The call to <code>reset</code> may throw an

     *     <code>IOException</code>.

     *

     *     <li> If an <code>IOException</code> is not thrown, then the stream

     *     is reset to a fixed state that depends on the particular type of the

     *     input stream and how it was created. The bytes that will be supplied

     *     to subsequent callers of the <code>read</code> method depend on the

     *     particular type of the input stream. </ul></ul>

     *

     * <p>The method <code>reset</code> for class <code>InputStream</code>

     * does nothing except throw an <code>IOException</code>.

     *

     * @exception  IOException  if this stream has not been marked or if the

     *               mark has been invalidated.

     * @see     java.io.InputStream#mark(int)

     * @see     java.io.IOException

     */

    public synchronized void reset() throws IOException {

        throw new IOException("mark/reset not supported");

    }

    /**

     * Tests if this input stream supports the <code>mark</code> and

     * <code>reset</code> methods. Whether or not <code>mark</code> and

     * <code>reset</code> are supported is an invariant property of a

     * particular input stream instance. The <code>markSupported</code> method

     * of <code>InputStream</code> returns <code>false</code>.

     *

     * @return  <code>true</code> if this stream instance supports the mark

     *          and reset methods; <code>false</code> otherwise.

     * @see     java.io.InputStream#mark(int)

     * @see     java.io.InputStream#reset()

     */

    public boolean markSupported() {

        return false;

    }

    /**

     * Reads all bytes from this input stream and writes the bytes to the

     * given output stream in the order that they are read. On return, this

     * input stream will be at end of stream. This method does not close either

     * stream.

     * <p>

     * This method may block indefinitely reading from the input stream, or

     * writing to the output stream. The behavior for the case where the input

     * and/or output stream is <i>asynchronously closed</i>, or the thread

     * interrupted during the transfer, is highly input and output stream

     * specific, and therefore not specified.

     * <p>

     * If an I/O error occurs reading from the input stream or writing to the

     * output stream, then it may do so after some bytes have been read or

     * written. Consequently the input stream may not be at end of stream and

     * one, or both, streams may be in an inconsistent state. It is strongly

     * recommended that both streams be promptly closed if an I/O error occurs.

     *

     * @param  out the output stream, non-null

     * @return the number of bytes transferred

     * @throws IOException if an I/O error occurs when reading or writing

     * @throws NullPointerException if {@code out} is {@code null}

     *

     * @since 9