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

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

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

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package java.nio;

import jdk.internal.HotSpotIntrinsicCandidate;

import jdk.internal.access.JavaNioAccess;

import jdk.internal.access.SharedSecrets;

import jdk.internal.misc.Unsafe;

import java.util.Spliterator;

/**

 * A container for data of a specific primitive type.

 *

 * <p> A buffer is a linear, finite sequence of elements of a specific

 * primitive type.  Aside from its content, the essential properties of a

 * buffer are its capacity, limit, and position: </p>

 *

 * <blockquote>

 *

 *   <p> A buffer's <i>capacity</i> is the number of elements it contains.  The

 *   capacity of a buffer is never negative and never changes.  </p>

 *

 *   <p> A buffer's <i>limit</i> is the index of the first element that should

 *   not be read or written.  A buffer's limit is never negative and is never

 *   greater than its capacity.  </p>

 *

 *   <p> A buffer's <i>position</i> is the index of the next element to be

 *   read or written.  A buffer's position is never negative and is never

 *   greater than its limit.  </p>

 *

 * </blockquote>

 *

 * <p> There is one subclass of this class for each non-boolean primitive type.

 *

 *

 * <h2> Transferring data </h2>

 *

 * <p> Each subclass of this class defines two categories of <i>get</i> and

 * <i>put</i> operations: </p>

 *

 * <blockquote>

 *

 *   <p> <i>Relative</i> operations read or write one or more elements starting

 *   at the current position and then increment the position by the number of

 *   elements transferred.  If the requested transfer exceeds the limit then a

 *   relative <i>get</i> operation throws a {@link BufferUnderflowException}

 *   and a relative <i>put</i> operation throws a {@link

 *   BufferOverflowException}; in either case, no data is transferred.  </p>

 *

 *   <p> <i>Absolute</i> operations take an explicit element index and do not

 *   affect the position.  Absolute <i>get</i> and <i>put</i> operations throw

 *   an {@link IndexOutOfBoundsException} if the index argument exceeds the

 *   limit.  </p>

 *

 * </blockquote>

 *

 * <p> Data may also, of course, be transferred in to or out of a buffer by the

 * I/O operations of an appropriate channel, which are always relative to the

 * current position.

 *

 *

 * <h2> Marking and resetting </h2>

 *

 * <p> A buffer's <i>mark</i> is the index to which its position will be reset

 * when the {@link #reset reset} method is invoked.  The mark is not always

 * defined, but when it is defined it is never negative and is never greater

 * than the position.  If the mark is defined then it is discarded when the

 * position or the limit is adjusted to a value smaller than the mark.  If the

 * mark is not defined then invoking the {@link #reset reset} method causes an

 * {@link InvalidMarkException} to be thrown.

 *

 *

 * <h2> Invariants </h2>

 *

 * <p> The following invariant holds for the mark, position, limit, and

 * capacity values:

 *

 * <blockquote>

 *     {@code 0} {@code <=}

 *     <i>mark</i> {@code <=}

 *     <i>position</i> {@code <=}

 *     <i>limit</i> {@code <=}

 *     <i>capacity</i>

 * </blockquote>

 *

 * <p> A newly-created buffer always has a position of zero and a mark that is

 * undefined.  The initial limit may be zero, or it may be some other value

 * that depends upon the type of the buffer and the manner in which it is

 * constructed.  Each element of a newly-allocated buffer is initialized

 * to zero.

 *

 *

 * <h2> Additional operations </h2>

 *

 * <p> In addition to methods for accessing the position, limit, and capacity

 * values and for marking and resetting, this class also defines the following

 * operations upon buffers:

 *

 * <ul>

 *

 *   <li><p> {@link #clear} makes a buffer ready for a new sequence of

 *   channel-read or relative <i>put</i> operations: It sets the limit to the

 *   capacity and the position to zero.  </p></li>

 *

 *   <li><p> {@link #flip} makes a buffer ready for a new sequence of

 *   channel-write or relative <i>get</i> operations: It sets the limit to the

 *   current position and then sets the position to zero.  </p></li>

 *

 *   <li><p> {@link #rewind} makes a buffer ready for re-reading the data that

 *   it already contains: It leaves the limit unchanged and sets the position

 *   to zero.  </p></li>

 *

 *   <li><p> The {@link #slice} and {@link #slice(int,int) slice(index,length)}

 *   methods create a subsequence of a buffer: They leave the limit and the

 *   position unchanged. </p></li>

 *

 *   <li><p> {@link #duplicate} creates a shallow copy of a buffer: It leaves

 *   the limit and the position unchanged. </p></li>

 *

 * </ul>

 *

 *

 * <h2> Read-only buffers </h2>

 *

 * <p> Every buffer is readable, but not every buffer is writable.  The

 * mutation methods of each buffer class are specified as <i>optional

 * operations</i> that will throw a {@link ReadOnlyBufferException} when

 * invoked upon a read-only buffer.  A read-only buffer does not allow its

 * content to be changed, but its mark, position, and limit values are mutable.

 * Whether or not a buffer is read-only may be determined by invoking its

 * {@link #isReadOnly isReadOnly} method.

 *

 *

 * <h2> Thread safety </h2>

 *

 * <p> Buffers are not safe for use by multiple concurrent threads.  If a

 * buffer is to be used by more than one thread then access to the buffer

 * should be controlled by appropriate synchronization.

 *

 *

 * <h2> Invocation chaining </h2>

 *

 * <p> Methods in this class that do not otherwise have a value to return are

 * specified to return the buffer upon which they are invoked.  This allows

 * method invocations to be chained; for example, the sequence of statements

 *

 * <blockquote><pre>

 * b.flip();

 * b.position(23);

 * b.limit(42);</pre></blockquote>

 *

 * can be replaced by the single, more compact statement

 *

 * <blockquote><pre>

 * b.flip().position(23).limit(42);</pre></blockquote>

 *

 *

 * @author Mark Reinhold

 * @author JSR-51 Expert Group

 * @since 1.4

 */

public abstract class Buffer {

    // Cached unsafe-access object

    static final Unsafe UNSAFE = Unsafe.getUnsafe();

    /**

     * The characteristics of Spliterators that traverse and split elements

     * maintained in Buffers.

     */

    static final int SPLITERATOR_CHARACTERISTICS =

        Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.ORDERED;

    // Invariants: mark <= position <= limit <= capacity

    private int mark = -1;

    private int position = 0;

    private int limit;

    private int capacity;

    // Used by heap byte buffers or direct buffers with Unsafe access

    // For heap byte buffers this field will be the address relative to the

    // array base address and offset into that array. The address might

    // not align on a word boundary for slices, nor align at a long word

    // (8 byte) boundary for byte[] allocations on 32-bit systems.

    // For direct buffers it is the start address of the memory region. The

    // address might not align on a word boundary for slices, nor when created

    // using JNI, see NewDirectByteBuffer(void*, long).

    // Should ideally be declared final

    // NOTE: hoisted here for speed in JNI GetDirectBufferAddress

    long address;

    // Creates a new buffer with the given mark, position, limit, and capacity,

    // after checking invariants.

    //

    Buffer(int mark, int pos, int lim, int cap) {       // package-private

        if (cap < 0)

            throw createCapacityException(cap);

        this.capacity = cap;

        limit(lim);

        position(pos);

        if (mark >= 0) {

            if (mark > pos)

                throw new IllegalArgumentException("mark > position: ("

                                                   + mark + " > " + pos + ")");

            this.mark = mark;

        }

    }

    /**

     * Returns an {@code IllegalArgumentException} indicating that the source

     * and target are the same {@code Buffer}.  Intended for use in

     * {@code put(src)} when the parameter is the {@code Buffer} on which the

     * method is being invoked.

     *

     * @return  IllegalArgumentException

     *          With a message indicating equal source and target buffers

     */

    static IllegalArgumentException createSameBufferException() {

        return new IllegalArgumentException("The source buffer is this buffer");

    }

    /**

     * Verify that the capacity is nonnegative.

     *

     * @param  capacity

     *         The new buffer's capacity, in $type$s

     *

     */

    static IllegalArgumentException createCapacityException(int capacity) {

        assert capacity < 0 : "capacity expected to be negative";

        return new IllegalArgumentException("capacity < 0: ("

            + capacity + " < 0)");

    }

    /**

     * Returns this buffer's capacity.

     *

     * @return  The capacity of this buffer

     */

    public final int capacity() {

        return capacity;

    }

    /**

     * Returns this buffer's position.

     *

     * @return  The position of this buffer

     */

    public final int position() {

        return position;

    }

    /**

     * Sets this buffer's position.  If the mark is defined and larger than the

     * new position then it is discarded.

     *

     * @param  newPosition

     *         The new position value; must be non-negative

     *         and no larger than the current limit

     *

     * @return  This buffer

     *

     * @throws  IllegalArgumentException

     *          If the preconditions on {@code newPosition} do not hold

     */

    public Buffer position(int newPosition) {

        if (newPosition > limit | newPosition < 0)

            throw createPositionException(newPosition);

        position = newPosition;

        if (mark > position) mark = -1;

        return this;

    }

    /**

     * Verify that {@code 0 < newPosition <= limit}

     *

     * @param newPosition

     *        The new position value

     *

     * @throws IllegalArgumentException

     *         If the specified position is out of bounds.

     */

    private IllegalArgumentException createPositionException(int newPosition) {

        String msg = null;

        if (newPosition > limit) {

            msg = "newPosition > limit: (" + newPosition + " > " + limit + ")";

        } else { // assume negative

            assert newPosition < 0 : "newPosition expected to be negative";

            msg = "newPosition < 0: (" + newPosition + " < 0)";

        }

        return new IllegalArgumentException(msg);

    }

    /**

     * Returns this buffer's limit.

     *

     * @return  The limit of this buffer

     */

    public final int limit() {

        return limit;

    }

    /**

     * Sets this buffer's limit.  If the position is larger than the new limit

     * then it is set to the new limit.  If the mark is defined and larger than

     * the new limit then it is discarded.

     *

     * @param  newLimit

     *         The new limit value; must be non-negative

     *         and no larger than this buffer's capacity

     *

     * @return  This buffer

     *

     * @throws  IllegalArgumentException

     *          If the preconditions on {@code newLimit} do not hold

     */

    public Buffer limit(int newLimit) {

        if (newLimit > capacity | newLimit < 0)

            throw createLimitException(newLimit);

        limit = newLimit;

        if (position > limit) position = limit;

        if (mark > limit) mark = -1;

        return this;

    }

    /**

     * Verify that {@code 0 < newLimit <= capacity}

     *

     * @param newLimit

     *        The new limit value

     *

     * @throws IllegalArgumentException

     *         If the specified limit is out of bounds.

     */

    private IllegalArgumentException createLimitException(int newLimit) {

        String msg = null;

        if (newLimit > capacity) {

            msg = "newLimit > capacity: (" + newLimit + " > " + capacity + ")";

        } else { // assume negative

            assert newLimit < 0 : "newLimit expected to be negative";

            msg = "newLimit < 0: (" + newLimit + " < 0)";

        }

        return new IllegalArgumentException(msg);

    }

    /**

     * Sets this buffer's mark at its position.

     *

     * @return  This buffer

     */

    public Buffer mark() {

        mark = position;

        return this;

    }

    /**

     * Resets this buffer's position to the previously-marked position.

     *

     * <p> Invoking this method neither changes nor discards the mark's

     * value. </p>

     *

     * @return  This buffer

     *

     * @throws  InvalidMarkException

     *          If the mark has not been set

     */

    public Buffer reset() {

        int m = mark;

        if (m < 0)

            throw new InvalidMarkException();

        position = m;

        return this;

    }

    /**

     * Clears this buffer.  The position is set to zero, the limit is set to

     * the capacity, and the mark is discarded.

     *

     * <p> Invoke this method before using a sequence of channel-read or

     * <i>put</i> operations to fill this buffer.  For example:

     *

     * <blockquote><pre>

     * buf.clear();     // Prepare buffer for reading

     * in.read(buf);    // Read data</pre></blockquote>

     *

     * <p> This method does not actually erase the data in the buffer, but it

     * is named as if it did because it will most often be used in situations

     * in which that might as well be the case. </p>

     *

     * @return  This buffer

     */

    public Buffer clear() {

        position = 0;

        limit = capacity;

        mark = -1;

        return this;

    }

    /**

     * Flips this buffer.  The limit is set to the current position and then

     * the position is set to zero.  If the mark is defined then it is

     * discarded.

     *

     * <p> After a sequence of channel-read or <i>put</i> operations, invoke

     * this method to prepare for a sequence of channel-write or relative

     * <i>get</i> operations.  For example:

     *

     * <blockquote><pre>

     * buf.put(magic);    // Prepend header

     * in.read(buf);      // Read data into rest of buffer

     * buf.flip();        // Flip buffer

     * out.write(buf);    // Write header + data to channel</pre></blockquote>

     *

     * <p> This method is often used in conjunction with the {@link

     * java.nio.ByteBuffer#compact compact} method when transferring data from

     * one place to another.  </p>

     *

     * @return  This buffer

     */

    public Buffer flip() {

        limit = position;

        position = 0;

        mark = -1;

        return this;

    }

    /**

     * Rewinds this buffer.  The position is set to zero and the mark is

     * discarded.

     *

     * <p> Invoke this method before a sequence of channel-write or <i>get</i>

     * operations, assuming that the limit has already been set

     * appropriately.  For example:

     *

     * <blockquote><pre>

     * out.write(buf);    // Write remaining data

     * buf.rewind();      // Rewind buffer

     * buf.get(array);    // Copy data into array</pre></blockquote>

     *

     * @return  This buffer

     */

    public Buffer rewind() {

        position = 0;

        mark = -1;

        return this;

    }

    /**

     * Returns the number of elements between the current position and the

     * limit.

     *

     * @return  The number of elements remaining in this buffer

     */

    public final int remaining() {

        return limit - position;

    }

    /**

     * Tells whether there are any elements between the current position and

     * the limit.

     *

     * @return  {@code true} if, and only if, there is at least one element

     *          remaining in this buffer

     */

    public final boolean hasRemaining() {

        return position < limit;

    }

    /**

     * Tells whether or not this buffer is read-only.

     *

     * @return  {@code true} if, and only if, this buffer is read-only

     */

    public abstract boolean isReadOnly();

    /**

     * Tells whether or not this buffer is backed by an accessible

     * array.

     *

     * <p> If this method returns {@code true} then the {@link #array() array}

     * and {@link #arrayOffset() arrayOffset} methods may safely be invoked.

     * </p>

     *