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RollingBuffer.cs
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RollingBuffer.cs
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using Lucene.Net.Diagnostics;
using System;
using System.Runtime.CompilerServices;
namespace Lucene.Net.Util
{
/*
* 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.
*/
/// <summary>
/// LUCENENET specific class to allow referencing static members of
/// <see cref="RollingBuffer{T}"/> without referencing its generic closing type.
/// </summary>
public static class RollingBuffer
{
/// <summary>
/// Implement to reset an instance
/// </summary>
public interface IResettable
{
void Reset();
}
}
/// <summary>
/// Acts like forever growing <see cref="T:T[]"/>, but internally uses a
/// circular buffer to reuse instances of <typeparam name="T"/>.
/// <para/>
/// @lucene.internal
/// </summary>
public abstract class RollingBuffer<T>
where T : RollingBuffer.IResettable
{
private T[] buffer = new T[8];
// Next array index to write to:
private int nextWrite;
// Next position to write:
private int nextPos;
// How many valid Position are held in the
// array:
private int count;
protected RollingBuffer()
{
for (var idx = 0; idx < buffer.Length; idx++)
{
buffer[idx] = NewInstance(); // TODO GIVE ROLLING BUFFER A DELEGATE FOR NEW INSTANCE
}
}
protected RollingBuffer(Func<T> factory)
{
for (int idx = 0; idx < buffer.Length; idx++)
{
buffer[idx] = factory();
}
}
protected abstract T NewInstance();
public virtual void Reset()
{
nextWrite--;
while (count > 0)
{
if (nextWrite == -1)
{
nextWrite = buffer.Length - 1;
}
buffer[nextWrite--].Reset();
count--;
}
nextWrite = 0;
nextPos = 0;
count = 0;
}
// For assert:
private bool InBounds(int pos)
{
return pos < nextPos && pos >= nextPos - count;
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private int GetIndex(int pos)
{
int index = nextWrite - (nextPos - pos);
if (index < 0)
{
index += buffer.Length;
}
return index;
}
/// <summary>
/// Get <typeparamref name="T"/> instance for this absolute position;
/// This is allowed to be arbitrarily far "in the
/// future" but cannot be before the last <see cref="FreeBefore(int)"/>.
/// </summary>
public virtual T Get(int pos)
{
//System.out.println("RA.get pos=" + pos + " nextPos=" + nextPos + " nextWrite=" + nextWrite + " count=" + count);
while (pos >= nextPos)
{
if (count == buffer.Length)
{
var newBuffer = new T[ArrayUtil.Oversize(1 + count, RamUsageEstimator.NUM_BYTES_OBJECT_REF)];
Array.Copy(buffer, nextWrite, newBuffer, 0, buffer.Length - nextWrite);
Array.Copy(buffer, 0, newBuffer, buffer.Length - nextWrite, nextWrite);
for (int i = buffer.Length; i < newBuffer.Length; i++)
{
newBuffer[i] = NewInstance();
}
nextWrite = buffer.Length;
buffer = newBuffer;
}
if (nextWrite == buffer.Length)
{
nextWrite = 0;
}
// Should have already been reset:
nextWrite++;
nextPos++;
count++;
}
if (Debugging.AssertsEnabled) Debugging.Assert(InBounds(pos));
int index = GetIndex(pos);
//System.out.println(" pos=" + pos + " nextPos=" + nextPos + " -> index=" + index);
//assert buffer[index].pos == pos;
return buffer[index];
}
/// <summary>
/// Returns the maximum position looked up, or -1 if no
/// position has been looked up since <see cref="Reset()"/>/init.
/// </summary>
public virtual int MaxPos => nextPos - 1;
public virtual void FreeBefore(int pos)
{
int toFree = count - (nextPos - pos);
if (Debugging.AssertsEnabled)
{
Debugging.Assert(toFree >= 0);
Debugging.Assert(toFree <= count, "toFree={0} count={1}", toFree, count);
}
int index = nextWrite - count;
if (index < 0)
{
index += buffer.Length;
}
for (int i = 0; i < toFree; i++)
{
if (index == buffer.Length)
{
index = 0;
}
//System.out.println(" fb idx=" + index);
buffer[index].Reset();
index++;
}
count -= toFree;
}
}
}