docs/csharp/language-reference/operators/snippets/shared/StackallocOperator.cs - main - aprogrammer/dotnet-docs

docs/csharp/language-reference/operators/snippets/shared/StackallocOperator.cs

78 строк2 KB

Genevieve Warren

Add third option for collection expressions analyzers (#39199)

19 янв 2024, 19:46

19 янв 2024, 19:462e00fb6

namespace operators;

public static class StackallocOperator
{
    public static void Examples()
    {
        StackallocInNestedExpressions();
    }

    private static void AssignToPointer()
    {
        // <SnippetAssignToPointer>
        unsafe
        {
            int length = 3;
            int* numbers = stackalloc int[length];
            for (var i = 0; i < length; i++)
            {
                numbers[i] = i;
            }
        }
        // </SnippetAssignToPointer>
    }

    private static void AssignToSpan()
    {
        // <SnippetAssignToSpan>
        int length = 3;
        Span<int> numbers = stackalloc int[length];
        for (var i = 0; i < length; i++)
        {
            numbers[i] = i;
        }
        // </SnippetAssignToSpan>
    }

    private static void AsExpression()
    {
        // <SnippetAsExpression>
        int length = 1000;
        Span<byte> buffer = length <= 1024 ? stackalloc byte[length] : new byte[length];
        // </SnippetAsExpression>
    }

    private static void StackallocInit()
    {
        // <SnippetStackallocInit>
        Span<int> first = stackalloc int[3] { 1, 2, 3 };
        Span<int> second = stackalloc int[] { 1, 2, 3 };
        ReadOnlySpan<int> third = stackalloc[] { 1, 2, 3 };

        // Using collection expressions:
        Span<int> fourth = [1, 2, 3];
        ReadOnlySpan<int> fifth = [1, 2, 3];
        // </SnippetStackallocInit>
    }

    private static void StackallocInNestedExpressions()
    {
        // <SnippetNested>
        Span<int> numbers = stackalloc[] { 1, 2, 3, 4, 5, 6 };
        var ind = numbers.IndexOfAny(stackalloc[] { 2, 4, 6, 8 });
        Console.WriteLine(ind);  // output: 1

        Span<int> numbers2 = [1, 2, 3, 4, 5, 6];
        var ind2 = numbers2.IndexOfAny([2, 4, 6, 8]);
        Console.WriteLine(ind2);  // output: 1
        // </SnippetNested>
    }

    private static void LimitStackAllocatedMemory(int inputLength)
    {
        // <SnippetLimitStackalloc>
        const int MaxStackLimit = 1024;
        Span<byte> buffer = inputLength <= MaxStackLimit ? stackalloc byte[MaxStackLimit] : new byte[inputLength];
        // </SnippetLimitStackalloc>
    }
}