Unity C# Convert float to byte array and read with node js

Question

Can someone explain how I can convert a float(Vector3.x) to a byte array with c# and decode it with node js?

I read on the internet that Vector3.x is a system.single data type and use 4 bytes(32 bits). I use BitConverter to convert it to a byte array. With Nodejs I use readFloatBE().

I don`t know what I'm doing wrong, but I get constantly a bad result with node js with console.log().

Unity csharp:

     public static int FloatToBit(int offset, ref byte[] data, Single number)
     {
         byte[] byteArray = System.BitConverter.GetBytes(number);
        for (int i = 0;i<4;i++)
         {
             data[offset + i] = byteArray[i];
         }

         return 4;
     }

Node js

     readFloat: function (offset, data) {
        var b = new Buffer(4);
        for (var i = 0; i < 4; i++) {       
               b[i] = data[offset + i];
           }     
        return data.readFloatLE(b, 0);
     },

If I send -2.5, unity output is: 0 0 32 191 with -1 unity output is: 0 0 128 192

Nodejs output with readFloatLE: 3.60133705331478e-43

Documentation shows- const buf = Buffer.from([1,2,3,4,5,6,7,8]); buf.readDoubleBE(); // Returns: 8.20788039913184e-304 buf.readDoubleLE(); // Returns: 5.447603722011605e-270. But I don't know why. Curious myself. — micah
– micah, Commented Jun 2, 2016 at 21:30
Careful with new Buffer(size). That is deprecated with the most recent version of node. It might technically be okay, since you're overwriting the 4 bytes anyways, but I wanted to bring it up. — dvlsg
– dvlsg, Commented Jun 2, 2016 at 21:53
@MicahWilliamson side note: those are just the numbers represented. What you're making is a buffer containing 0x0102030405060708, and the doubles those represent are what you're seeing in your returns, based on whether you read them as big or little endian. — dvlsg
– dvlsg, Commented Jun 2, 2016 at 22:43

dvlsg · Accepted Answer · 2016-06-02 22:05:01Z

1

Here's a working set of data from front to back.

C#:

Single fl = 2.5F;
var bytes = System.BitConverter.GetBytes(fl);
var str = BitConverter.ToString(bytes); // 00-00-20-40

Nodejs:

let buffer = Buffer.from([ 0x00, 0x00, 0x20, 0x40 ]);
let float = buffer.readFloatLE(); // 2.5

Note the method I used to create the buffer in nodejs, especially (also tested and verified with -1, but I left the code off for brevity).

answered Jun 2, 2016 at 22:05

dvlsg

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Comments

Erik · Accepted Answer · 2016-06-04 16:43:10Z

0

Thanks for the replies.

I put the same question over here:Unity Questions

Somebody give me the answer to use:

  readFloat: function (offset, data) {
        return data.readFloatLE(offset);

},

instead creating a new buffer.

Parameter is a buffer. This was working for me. I still don`t understand why my example is not working.

answered Jun 4, 2016 at 16:43

Erik

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