NCode.ArrayLeases

PM> Install-Package NCode.ArrayLeases

This library provides provides IDisposable leases for Microsoft's new ArrayPool class from the System.Buffers package. These IDisposable implementations will automatically return the array back to the ArrayPool when the lease is disposed.

Usage

Before

public static void Main(string[] args)
{
  var pool = ArrayPool<byte>.Shared;
  var buffer = pool.Rent(4096);
  try
  {
    // use the buffer...
  }
  finally
  {
    pool.Return(buffer);
  }
}

After

public static void Main(string[] args)
{
  var pool = ArrayPool<byte>.Shared;
  using (var lease = pool.Lease(4096))
  {
    // use the buffer...
  }
}

IArrayLease

Represents a lease by encapsulating it's array and item count. The item Count property is assignable to any value less than or equal to the array length.

public interface IArrayLease<out T> : IDisposable
{
  int Count { get; set; }
  T[] Array { get; }
}

Count Property

The impetus for allowing to assign the item Count is because arrays returned from the pool are not the exact length requested. The Count property is initially set to the requested length but can be assigned to any value less than or equal to the array length so that consumers may know how much data to consume. See the ArrayPool API for additional details about buffer sizes.

ArrayLease

Base class for IArrayLease<T> and provides a default implementation for it's properties. Derived classes must override the following method to relinquish the lease. The default implementation for Return does nothing.

public class ArrayLease<T>
{
  public ArrayLease(T[] array) { /* ... */ }
  public ArrayLease(T[] array, int count) { /* ... */ }

  // other members ...

  protected virtual void Return(T[] array)
  {
    // override for custom behavior
  }
}

ArrayPoolLease

Contains an implementation of ArrayLease<T> that will Rent an array from ArrayPool<T> and then Return the array after the lease is disposed.

public class ArrayPoolLease<T> : ArrayLease<T>
{
  // uses static 'ArrayPool<T>.Shared' instance:
  public ArrayPoolLease(
    int count,
    bool clearArrayOnReturn = false
  );

  // specify any other 'ArrayPool<T>' instance:
  public ArrayPoolLease(
    ArrayPool<T> pool,
    int count,
    bool clearArrayOnReturn = false
  );

  protected override void Return(T[] array)
  {
    _pool.Return(array);
  }
}

Extension Methods

Various extension methods exist to create leases for multiple use-cases.

// From an array to a lease:
// The Dispose implementation on these leases perform nothing.
public static IArrayLease<T> Lease<T>(this T[] array);
public static IArrayLease<T> Lease<T>(this T[] array, int count);

// From an array pool to a lease:
// The Dispose implementation on these leases will return the array back to the pool.
public static IArrayLease<T> Lease<T>(this ArrayPool<T> pool, int count, bool clearArrayOnReturn = false);

// From a lease to an array segment:
public static ArraySegment<T> Segment<T>(this IArrayLease<T> lease);
public static ArraySegment<T> Segment<T>(this IArrayLease<T> lease, int offset, int count);

Release Notes

• v1.0.0 - Initial Release
• v1.0.1 - Refresh the build

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