Question

I would like to get a byte[] from a float[] as quickly as possible, without looping through the whole array (via a cast, probably). Unsafe code is fine. Thanks!

I am looking for a byte array 4 time longer than the float array (the dimension of the byte array will be 4 times that of the float array, since each float is composed of 4 bytes). I’ll pass this to a BinaryWriter.

EDIT: To those critics screaming ‘premature optimization’: I have benchmarked this using ANTS profiler before I optimized. There was a significant speed increase because the file has a write-through cache and the float array is exactly sized to match the sector size on the disk. The binary writer wraps a file handle created with pinvoke‘d win32 API. The optimization occurs since this lessens the number of function calls.

And, with regard to memory, this application creates massive caches which use plenty of memory. I can allocate the byte buffer once and re-use it many times–the double memory usage in this particular instance amounts to a roundoff error in the overall memory consumption of the app.

So I guess the lesson here is not to make premature assumptions 😉

Answer 1

If you do not want any conversion to happen, I would suggest Buffer.BlockCopy().

public static void BlockCopy(     Array src,     int srcOffset,     Array dst,     int dstOffset,     int count ) 

For example:

float[] floatArray = new float[1000]; byte[] byteArray = new byte[floatArray.Length * 4];  Buffer.BlockCopy(floatArray, 0, byteArray, 0, byteArray.Length);