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POField-wise comparison of unmanaged struct
 

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  1. POField-wise comparison of unmanaged struct
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    <p>For test purpose, I want to compare two structs (of unknown type T) marshaled from unmanaged code.</p> <p>Because they may contain some packing in unmanaged representation, it is inappropriate to convert whole struct to byte array and then compare byte by byte:</p> <pre><code>int size = Marshal.SizeOf(typeof(T)); IntPtr buf1 = Marshal.AllocHGlobal(size); // FreeHGlobal omitted for simplicity IntPtr buf2 = Marshal.AllocHGlobal(size); byte[] array1 = new byte[size]; byte[] array2 = new byte[size]; Marshal.StructureToPtr(st1, buf1, false); Marshal.StructureToPtr(st2, buf2, false); Marshal.Copy(buf1, array1, 0, size); Marshal.Copy(buf2, array2, 0, size); // inapropriate for (int i = 0; i &lt; size; ++i) { if (array1[i] != array2[i]) { return false; } } return true; </code></pre> <p>I think it is necessary to compare field by field.</p> <p>Thanks to reflection, I can enumerate FieldInfo, and then using Marshal.OffsetOf method I can get offsets of the fields.</p> <p>Unfortunately, however, I have no idea how to get sizes of the fields. Without it I think I can't compare two fields eliminating the effect of packing.</p> <pre><code>foreach (var fieldInfo in typeof(T).GetFields()) { int offset = (int)Marshal.OffsetOf(typeof(T), fieldInfo.Name); int fieldSize = ...; // I need this for (int i = offset; i &lt; offset + fieldSize; ++i) { if (array1[i] != array2[i]) { return false; } } } return true; </code></pre> <p>Is there any way to accomplish this? Or Is there better way to compare the unmanaged structs?</p> <p><strong>Note:</strong> Field types are arbitrary (may be primitive integers, arrays, strings, enums, structs, etc).</p>
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