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POC# unsafe value type array to byte array conversions
 

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    <p>I use an extension method to convert float arrays into byte arrays:</p> <pre><code>public static unsafe byte[] ToByteArray(this float[] floatArray, int count) { int arrayLength = floatArray.Length &gt; count ? count : floatArray.Length; byte[] byteArray = new byte[4 * arrayLength]; fixed (float* floatPointer = floatArray) { fixed (byte* bytePointer = byteArray) { float* read = floatPointer; float* write = (float*)bytePointer; for (int i = 0; i &lt; arrayLength; i++) { *write++ = *read++; } } } return byteArray; } </code></pre> <p>I understand that an array is a pointer to memory associated with information on the type and number of elements. Also, it seems to me that there is no way of doing a conversion from and to a byte array without copying the data as above.</p> <p>Have I understood this? Would it even be impossible to write IL to create an array from a pointer, type and length without copying data?</p> <p><strong>EDIT:</strong> Thanks for the answers, I learned some fundamentals and got to try out new tricks!</p> <p>After initially accepting Davy Landman's answer I found out that while his brilliant StructLayout hack does convert byte arrays into float arrays, it does not work the other way around. To demonstrate:</p> <pre><code>[StructLayout(LayoutKind.Explicit)] struct UnionArray { [FieldOffset(0)] public Byte[] Bytes; [FieldOffset(0)] public float[] Floats; } static void Main(string[] args) { // From bytes to floats - works byte[] bytes = { 0, 1, 2, 4, 8, 16, 32, 64 }; UnionArray arry = new UnionArray { Bytes = bytes }; for (int i = 0; i &lt; arry.Bytes.Length / 4; i++) Console.WriteLine(arry.Floats[i]); // From floats to bytes - index out of range float[] floats = { 0.1f, 0.2f, 0.3f }; arry = new UnionArray { Floats = floats }; for (int i = 0; i &lt; arry.Floats.Length * 4; i++) Console.WriteLine(arry.Bytes[i]); } </code></pre> <p>It seems that the CLR sees both arrays as having the same length. If the struct is created from float data, the byte array's length is just too short. </p>
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    1. COApart from the question, your first statement would be clearer if you used Math.Min(count, floatArray.Length)
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