/* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 java.nio;
/** A buffer is a list of elements of a specific primitive type.
* <p>
* A buffer can be described by the following properties:
* <ul>
* <li>Capacity: the number of elements a buffer can hold. Capacity may not be negative and never changes.</li>
* <li>Position: a cursor of this buffer. Elements are read or written at the position if you do not specify an index explicitly.
* Position may not be negative and not greater than the limit.</li>
* <li>Limit: controls the scope of accessible elements. You can only read or write elements from index zero to
* <code>limit - 1</code>. Accessing elements out of the scope will cause an exception. Limit may not be negative and not greater
* than capacity.</li>
* <li>Mark: used to remember the current position, so that you can reset the position later. Mark may not be negative and no
* greater than position.</li>
* <li>A buffer can be read-only or read-write. Trying to modify the elements of a read-only buffer will cause a
* <code>ReadOnlyBufferException</code>, while changing the position, limit and mark of a read-only buffer is OK.</li>
* <li>A buffer can be direct or indirect. A direct buffer will try its best to take advantage of native memory APIs and it may
* not stay in the Java heap, thus it is not affected by garbage collection.</li>
* </ul>
* </p>
* <p>
* Buffers are not thread-safe. If concurrent access to a buffer instance is required, then the callers are responsible to take
* care of the synchronization issues.
* </p>
*
* @since Android 1.0 */
public abstract class Buffer {
/** <code>UNSET_MARK</code> means the mark has not been set. */
final static int UNSET_MARK = -1;
/** The capacity of this buffer, which never change. */
final int capacity;
/** <code>limit - 1</code> is the last element that can be read or written. Limit must be no less than zero and no greater than
* <code>capacity</code>. */
int limit;
/** Mark is where position will be set when <code>reset()</code> is called. Mark is not set by default. Mark is always no less
* than zero and no greater than <code>position</code>. */
int mark = UNSET_MARK;
/** The current position of this buffer. Position is always no less than zero and no greater than <code>limit</code>. */
int position = 0;
/** Construct a buffer with the specified capacity.
*
* @param capacity the capacity of this buffer. */
Buffer (int capacity) {
super();
if (capacity < 0) {
throw new IllegalArgumentException();
}
this.capacity = this.limit = capacity;
}
/** Returns the capacity of this buffer.
*
* @return the number of elements that are contained in this buffer.
* @since Android 1.0 */
public final int capacity () {
return capacity;
}
/** Clears this buffer.
* <p>
* While the content of this buffer is not changed, the following internal changes take place: the current position is reset
* back to the start of the buffer, the value of the buffer limit is made equal to the capacity and mark is cleared.
* </p>
*
* @return this buffer.
* @since Android 1.0 */
public final Buffer clear () {
position = 0;
mark = UNSET_MARK;
limit = capacity;
return this;
}
/** Flips this buffer.
* <p>
* The limit is set to the current position, then the position is set to zero, and the mark is cleared.
* </p>
* <p>
* The content of this buffer is not changed.
* </p>
*
* @return this buffer.
* @since Android 1.0 */
public final Buffer flip () {
limit = position;
position = 0;
mark = UNSET_MARK;
return this;
}
/** Indicates if there are elements remaining in this buffer, that is if {@code position < limit}.
*
* @return {@code true} if there are elements remaining in this buffer, {@code false} otherwise.
* @since Android 1.0 */
public final boolean hasRemaining () {
return position < limit;
}
/** Indicates whether this buffer is read-only.
*
* @return {@code true} if this buffer is read-only, {@code false} otherwise.
* @since Android 1.0 */
public abstract boolean isReadOnly ();
/** Returns the limit of this buffer.
*
* @return the limit of this buffer.
* @since Android 1.0 */
public final int limit () {
return limit;
}
/** Sets the limit of this buffer.
* <p>
* If the current position in the buffer is in excess of <code>newLimit</code> then, on returning from this call, it will have
* been adjusted to be equivalent to <code>newLimit</code>. If the mark is set and is greater than the new limit, then it is
* cleared.
* </p>
*
* @param newLimit the new limit, must not be negative and not greater than capacity.
* @return this buffer.
* @exception IllegalArgumentException if <code>newLimit</code> is invalid.
* @since Android 1.0 */
public final Buffer limit (int newLimit) {
if (newLimit < 0 || newLimit > capacity) {
throw new IllegalArgumentException();
}
limit = newLimit;
if (position > newLimit) {
position = newLimit;
}
if ((mark != UNSET_MARK) && (mark > newLimit)) {
mark = UNSET_MARK;
}
return this;
}
/** Marks the current position, so that the position may return to this point later by calling <code>reset()</code>.
*
* @return this buffer.
* @since Android 1.0 */
public final Buffer mark () {
mark = position;
return this;
}
/** Returns the position of this buffer.
*
* @return the value of this buffer's current position.
* @since Android 1.0 */
public final int position () {
return position;
}
/** Sets the position of this buffer.
* <p>
* If the mark is set and it is greater than the new position, then it is cleared.
* </p>
*
* @param newPosition the new position, must be not negative and not greater than limit.
* @return this buffer.
* @exception IllegalArgumentException if <code>newPosition</code> is invalid.
* @since Android 1.0 */
public final Buffer position (int newPosition) {
if (newPosition < 0 || newPosition > limit) {
throw new IllegalArgumentException();
}
position = newPosition;
if ((mark != UNSET_MARK) && (mark > position)) {
mark = UNSET_MARK;
}
return this;
}
/** Returns the number of remaining elements in this buffer, that is {@code limit - position}.
*
* @return the number of remaining elements in this buffer.
* @since Android 1.0 */
public final int remaining () {
return limit - position;
}
/** Resets the position of this buffer to the <code>mark</code>.
*
* @return this buffer.
* @exception InvalidMarkException if the mark is not set.
* @since Android 1.0 */
public final Buffer reset () {
if (mark == UNSET_MARK) {
throw new InvalidMarkException();
}
position = mark;
return this;
}
/** Rewinds this buffer.
* <p>
* The position is set to zero, and the mark is cleared. The content of this buffer is not changed.
* </p>
*
* @return this buffer.
* @since Android 1.0 */
public final Buffer rewind () {
position = 0;
mark = UNSET_MARK;
return this;
}
}