C# - ArrayPool Example - Dot Net Perls

ArrayPool. Sometimes in C# programs we want to allocate many arrays of similar lengths. These arrays may be needed only for short times.

Array

To reuse an array from an ArrayPool, we "rent" it with the Rent() method. We can then Return() the same array to allow later uses.

Here we introduce a method called UseSharedArray that uses the ArrayPool generic type. We call UseSharedArray 3 times with a different number.

Generic

Part 1 We access the ArrayPool type and specify a type parameter int. We use the Shared property, and call Rent.

int

Part 2 The rented array always has a length of at least the value specified (in this program, 5). We use the array here.

Array Length

Part 3 We call Return() to allow the rented array to be used by another call. This enables reuse of allocated arrays.

using System;
using System.Buffers;

class Program
{
    static void UseSharedArray(int x)
    {
        // Part 1: reference the ArrayPool and Rent an array.
        var shared = ArrayPool<int>.Shared;
        var rentedArray = shared.Rent(5);

        // Part 2: store values in rented array and print them.
        rentedArray[0] = 0;
        rentedArray[1] = 1 * x;
        rentedArray[2] = 2 * x;
        rentedArray[3] = 3 * x;
        rentedArray[4] = 4 * x;
        // ... Print integers.
        for (int i = 0; i < 5; i++)
        {
            Console.WriteLine("ARRAY {0}: {1}", x, rentedArray[i]);
        }

        // Part 3: return the rented array.
        shared.Return(rentedArray);
    }

    static void Main()
    {
        UseSharedArray(1);
        UseSharedArray(2);
        UseSharedArray(3);
    }
}ARRAY 1: 0
ARRAY 1: 1
ARRAY 1: 2
ARRAY 1: 3
ARRAY 1: 4
ARRAY 2: 0
ARRAY 2: 2
ARRAY 2: 4
ARRAY 2: 6
ARRAY 2: 8
ARRAY 3: 0
ARRAY 3: 3
ARRAY 3: 6
ARRAY 3: 9
ARRAY 3: 12

Static array. Sometimes we have simple array sharing requirements—only 1 array may be needed. We can just use a static array of a certain length.

static Array

using System;

class Program
{
    static int[] _shared = new int[5];

    static void UseStaticArray(int x)
    {
        var rentedArray = _shared;
        rentedArray[0] = 0;
        rentedArray[1] = 1 * x;
        rentedArray[2] = 2 * x;
        rentedArray[3] = 3 * x;
        rentedArray[4] = 4 * x;
        // ... Print integers.
        for (int i = 0; i < 5; i++)
        {
            Console.WriteLine("ARRAY {0}: {1}", x, rentedArray[i]);
        }
    }

    static void Main()
    {
        UseStaticArray(1);
        UseStaticArray(2);
        UseStaticArray(3);
    }
}ARRAY 1: 0
ARRAY 1: 1
ARRAY 1: 2
ARRAY 1: 3
ARRAY 1: 4
ARRAY 2: 0
ARRAY 2: 2
ARRAY 2: 4
ARRAY 2: 6
ARRAY 2: 8
ARRAY 3: 0
ARRAY 3: 3
ARRAY 3: 6
ARRAY 3: 9
ARRAY 3: 12

For complex array sharing requirements, ArrayPool is a good choice. For simple programs where only one array is shared, a static array can be used.

static