/*
* Copyright 2013 Alex Kasko (alexkasko.com)
*
* Licensed 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 com.alexkasko.unsafe.offheaplong;
import com.alexkasko.unsafe.offheap.OffHeapDisposable;
import com.alexkasko.unsafe.offheap.OffHeapDisposableIterator;
import com.alexkasko.unsafe.offheap.OffHeapMemory;
import java.util.Iterator;
/**
* <p>Implementation of array-list of long using {@link com.alexkasko.unsafe.offheap.OffHeapMemory}.
* Memory area will be allocated another time and copied on elements adding. This class doesn't support elements removing.
* {@link #get(long)} and {@link #set(long, long)} access operations indexes are checked using {@code assert} keyword
* (indexes between size and capacity will be rejected).
*
* <p>Default implementation uses {@code sun.misc.Unsafe}, with all operations guarded with {@code assert} keyword.
* With assertions enabled in runtime ({@code -ea} java switch) {@link AssertionError}
* will be thrown on illegal index access. Without assertions illegal index will crash JVM.
*
* <p>Allocated memory may be freed manually using {@link #free()} (thread-safe
* and may be called multiple times) or it will be freed after {@link OffHeapLongArray}
* will be garbage collected.
*
* <p>Note: while class implements Iterable, iterator will create new autoboxed Long object
* <b>on every</b> {@code next()} call, this behaviour is inevitable with iterators in java 6/7.
*
* @author alexkasko
* Date: 3/1/13
*/
public class OffHeapLongArrayList implements OffHeapLongAddressable, OffHeapDisposable, Iterable<Long> {
private static final int MIN_CAPACITY_INCREMENT = 12;
private static final int ELEMENT_LENGTH = 8;
private OffHeapMemory ohm;
private long size;
private long capacity;
/**
* Constructor, {@code 12} is used as initial capacity
*/
public OffHeapLongArrayList() {
this(MIN_CAPACITY_INCREMENT);
}
/**
* Constructor
*
* @param capacity initial capacity
*/
public OffHeapLongArrayList(long capacity) {
this.capacity = capacity;
this.ohm = OffHeapMemory.allocateMemory(capacity * ELEMENT_LENGTH);
}
/**
* Adds element to the end of this list. Memory area will be allocated another time and copied
* on capacity exceed.
*
* @param value value to add
*/
public void add(long value) {
OffHeapMemory oh = ohm;
long s = size;
if (s == capacity) {
long len = s + (s < (MIN_CAPACITY_INCREMENT / 2) ? MIN_CAPACITY_INCREMENT : s >> 1);
OffHeapMemory newOhm = OffHeapMemory.allocateMemory(len * ELEMENT_LENGTH);
// maybe it's better to use Unsafe#reallocateMemory here
oh.copy(0, newOhm, 0, oh.length());
oh.free();
ohm = newOhm;
capacity = len;
}
size = s + 1;
set(s, value);
}
/**
* Whether unsafe implementation of {@link OffHeapMemory} is used
*
* @return whether unsafe implementation of {@link OffHeapMemory} is used
*/
public boolean isUnsafe() {
return ohm.isUnsafe();
}
/**
* Gets the element at position {@code index} from {@code 0} to {@code size-1}
*
* @param index list index
* @return long value
*/
@Override
public long get(long index) {
assert index < size : index;
return ohm.getLong(index * ELEMENT_LENGTH);
}
/**
* Sets the element at position {@code index} (from {@code 0} to {@code size-1}) to the given value
*
* @param index list index
* @param value long value
*/
@Override
public void set(long index, long value) {
assert index < size : index;
ohm.putLong(index * ELEMENT_LENGTH, value);
}
/**
* Returns number of elements in list
*
* @return number of elements in list
*/
@Override
public long size() {
return size;
}
/**
* Returns number of elements list may contain without additional memory allocation
*
* @return number of elements list may contain without additional memory allocation
*/
public long capacity() {
return capacity;
}
/**
* Frees allocated memory, may be called multiple times from any thread
*/
@Override
public void free() {
ohm.free();
}
/**
* {@inheritDoc}
*/
@Override
public OffHeapDisposableIterator<Long> iterator() {
return new OffHeapLongIterator(this);
}
/**
* Resets the collection setting size to 0.
* Actual memory contents stays untouched.
*/
public void reset() {
this.size = 0;
}
/**
* {@inheritDoc}
*/
@Override
public String toString() {
final StringBuilder sb = new StringBuilder();
sb.append("OffHeapLongArrayList");
sb.append("{size=").append(size());
sb.append(", capacity=").append(capacity);
sb.append(", unsafe=").append(isUnsafe());
sb.append('}');
return sb.toString();
}
}