using System;

using System.Diagnostics;

using System.Threading;

namespace ServiceStack.Redis

{

/// <summary>

/// Courtesy of @marcgravell

/// http://code.google.com/p/protobuf-net/source/browse/trunk/protobuf-net/BufferPool.cs

/// </summary>

internal class BufferPool

{

internal static void Flush()

{

for (int i = 0; i < pool.Length; i++)

{

Interlocked.Exchange(ref pool[i], null); // and drop the old value on the floor

}

}

private BufferPool() { }

const int PoolSize = 1000; //1.45MB

//internal const int BufferLength = 1450; //MTU size - some headers

private static readonly object[] pool = new object[PoolSize];

internal static byte[] GetBuffer(int bufferSize)

{

return bufferSize > RedisConfig.BufferPoolMaxSize

? new byte[bufferSize]

: GetBuffer();

}

internal static byte[] GetBuffer()

{

object tmp;

for (int i = 0; i < pool.Length; i++)

{

if ((tmp = Interlocked.Exchange(ref pool[i], null)) != null)

return (byte[])tmp;

}

return new byte[RedisConfig.BufferLength];

}

internal static void ResizeAndFlushLeft(ref byte[] buffer, int toFitAtLeastBytes, int copyFromIndex, int copyBytes)

{

Debug.Assert(buffer != null);

Debug.Assert(toFitAtLeastBytes > buffer.Length);

Debug.Assert(copyFromIndex >= 0);

Debug.Assert(copyBytes >= 0);

// try doubling, else match

int newLength = buffer.Length * 2;

if (newLength < toFitAtLeastBytes) newLength = toFitAtLeastBytes;

var newBuffer = new byte[newLength];

if (copyBytes > 0)

{

Buffer.BlockCopy(buffer, copyFromIndex, newBuffer, 0, copyBytes);

}

if (buffer.Length == RedisConfig.BufferLength)

{

ReleaseBufferToPool(ref buffer);

}

buffer = newBuffer;

}

internal static void ReleaseBufferToPool(ref byte[] buffer)

{

if (buffer == null) return;

if (buffer.Length == RedisConfig.BufferLength)

{

for (int i = 0; i < pool.Length; i++)

{

if (Interlocked.CompareExchange(ref pool[i], buffer, null) == null)

{

break; // found a null; swapped it in

}

}

}

// if no space, just drop it on the floor

buffer = null;

}

}

}