Thursday, April 09, 2015

Malloc in BinaryReader and BinaryWriter

In my efforts to write a malloc-free network library for Unity3D, I discovered that BinaryReader and BinaryWriter perform malloc operations when reading/writing floats and doubles.

It seems this is the case, because C# does not allow bit shifting operations on these types, which is used to turn these types into 4 or 8 bytes.

I ended up using this code to convert these types without using the builtin BitConverter (which performs a malloc!)

float[] FLOAT = new float[1];

public float ReadFloat ()
   Buffer.BlockCopy(buffer, (int)readStream.Position, FLOAT, 0, 4);
   readStream.Position += 4;
   return FLOAT[0];

public void Write (float value)
   FLOAT[0] = value;
   Buffer.BlockCopy(FLOAT, 0, buffer, (int)writeStream.Position, 4);
   writeStream.Position += 4;

1 comment:

Nevermind said...

C# is tricky like that. I remember seeing this allocation when we were making an MMO game... we decided to just live with it though.

There are even stranger things there. Did you know that DateTime.Now makes an allocation sometimes?

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