ArrayWithOffset.cs

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using System.Diagnostics.CodeAnalysis;
using System.Runtime.CompilerServices;
 
namespace System.Runtime.InteropServices;
 
public readonly struct ArrayWithOffset
{
    private readonly object m_array;
 
    private readonly int m_offset;
 
    private readonly int m_count;
 
    public ArrayWithOffset(object? array, int offset)
    {
        int num = 0;
        if (array != null)
        {
            if (!(array is Array { Rank: 1 } array2) || !Marshal.IsPinnable(array2))
            {
                throw new ArgumentException(SR.ArgumentException_NotIsomorphic);
            }
            nuint num2 = array2.NativeLength * array2.GetElementSize();
            if (num2 > 2147483632)
            {
                throw new ArgumentException(SR.Argument_StructArrayTooLarge);
            }
            num = (int)num2;
        }
        if ((uint)offset > (uint)num)
        {
            throw new IndexOutOfRangeException(SR.IndexOutOfRange_ArrayWithOffset);
        }
        m_array = array;
        m_offset = offset;
        m_count = num - offset;
    }
 
    public object? GetArray()
    {
        return m_array;
    }
 
    public int GetOffset()
    {
        return m_offset;
    }
 
    public override int GetHashCode()
    {
        return m_count + m_offset;
    }
 
    public override bool Equals([NotNullWhen(true)] object? obj)
    {
        if (obj is ArrayWithOffset)
        {
            return Equals((ArrayWithOffset)obj);
        }
        return false;
    }
 
    public bool Equals(ArrayWithOffset obj)
    {
        if (obj.m_array == m_array && obj.m_offset == m_offset)
        {
            return obj.m_count == m_count;
        }
        return false;
    }
 
    public static bool operator ==(ArrayWithOffset a, ArrayWithOffset b)
    {
        return a.Equals(b);
    }
 
    public static bool operator !=(ArrayWithOffset a, ArrayWithOffset b)
    {
        return !(a == b);
    }
}