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/*
* Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
* and other copyright owners as documented in the project's IP log.
*
* This program and the accompanying materials are made available
* under the terms of the Eclipse Distribution License v1.0 which
* accompanies this distribution, is reproduced below, and is
* available at http://www.eclipse.org/org/documents/edl-v10.php
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or
* without modification, are permitted provided that the following
* conditions are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials provided
* with the distribution.
*
* - Neither the name of the Eclipse Foundation, Inc. nor the
* names of its contributors may be used to endorse or promote
* products derived from this software without specific prior
* written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package org.eclipse.jgit.revwalk;
class BlockObjQueue {
private BlockFreeList free;
private Block head;
private Block tail;
/** Create an empty queue. */
BlockObjQueue() {
free = new BlockFreeList();
}
void add(final RevObject c) {
Block b = tail;
if (b == null) {
b = free.newBlock();
b.add(c);
head = b;
tail = b;
return;
} else if (b.isFull()) {
b = free.newBlock();
tail.next = b;
tail = b;
}
b.add(c);
}
RevObject next() {
final Block b = head;
if (b == null)
return null;
final RevObject c = b.pop();
if (b.isEmpty()) {
head = b.next;
if (head == null)
tail = null;
free.freeBlock(b);
}
return c;
}
static final class BlockFreeList {
private Block next;
Block newBlock() {
Block b = next;
if (b == null)
return new Block();
next = b.next;
b.clear();
return b;
}
void freeBlock(final Block b) {
b.next = next;
next = b;
}
}
static final class Block {
private static final int BLOCK_SIZE = 256;
/** Next block in our chain of blocks; null if we are the last. */
Block next;
/** Our table of queued objects. */
final RevObject[] objects = new RevObject[BLOCK_SIZE];
/** Next valid entry in {@link #objects}. */
int headIndex;
/** Next free entry in {@link #objects} for addition at. */
int tailIndex;
boolean isFull() {
return tailIndex == BLOCK_SIZE;
}
boolean isEmpty() {
return headIndex == tailIndex;
}
void add(final RevObject c) {
objects[tailIndex++] = c;
}
RevObject pop() {
return objects[headIndex++];
}
void clear() {
next = null;
headIndex = 0;
tailIndex = 0;
}
}
}
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