Issue with System.IO.BinaryReader( Span )

Unity Engine
,
1

Hi. I did some code to save and load mesh data.
The write is fine
The read is wrong
doing a BinaryReader.Read( Span ) returns the right value (the byte size of the span), but doesn’t modify the values of the array. reading byte by byte is (slow) fine.
(BinaryWriter.Write( Span ) was fine)
Do I miss something or this fread(file,buf,size) doesn’t work ?

        public    override    unsafe void    Read( System.IO.BinaryReader _reader )
        {
            System.Span<byte>    dst = new System.Span<byte>( NativeArrayUnsafeUtility.GetUnsafePtr(m_data), m_cnt * Stride() );
            dst.Fill( 0xAA );
            for    ( int i = 0; i < m_cnt * Stride(); i++ )
                dst[i] = _reader.ReadByte();
//            int    n = _reader.Read( dst );
        }
2

Most likely m_cnt * Stride() is zero.

I say this because you’re assigning to each chunk in the array… I’m unfamiliar with the System.Span type, but if that’s the right way to assign, SOMETHING should be changing the 0xAA fill.

If it does not, change to another number such as 0x55… if that assignment is happening (no exceptions), then SOMETHING has to be assigned.

You must find a way to get the information you need in order to reason about what the problem is.

What is often happening in these cases is one of the following:

  • the code you think is executing is not actually executing at all
  • the code is executing far EARLIER or LATER than you think
  • the code is executing far LESS OFTEN than you think
  • the code is executing far MORE OFTEN than you think
  • the code is executing on another GameObject than you think it is
  • you’re getting an error or warning and you haven’t noticed it in the console window

To help gain more insight into your problem, I recommend liberally sprinkling Debug.Log() statements through your code to display information in realtime.

Doing this should help you answer these types of questions:

  • is this code even running? which parts are running? how often does it run? what order does it run in?
  • what are the values of the variables involved? Are they initialized? Are the values reasonable?
  • are you meeting ALL the requirements to receive callbacks such as triggers / colliders (review the documentation)

Knowing this information will help you reason about the behavior you are seeing.

If your problem would benefit from in-scene or in-game visualization, Debug.DrawRay() or Debug.DrawLine() can help you visualize things like rays (used in raycasting) or distances.

You can also call Debug.Break() to pause the Editor when certain interesting pieces of code run, and then study the scene manually, looking for all the parts, where they are, what scripts are on them, etc.

You can also call GameObject.CreatePrimitive() to emplace debug-marker-ish objects in the scene at runtime.

You could also just display various important quantities in UI Text elements to watch them change as you play the game.

If you are running a mobile device you can also view the console output. Google for how on your particular mobile target.

Another useful approach is to temporarily strip out everything besides what is necessary to prove your issue. This can simplify and isolate compounding effects of other items in your scene or prefab.

Here’s an example of putting in a laser-focused Debug.Log() and how that can save you a TON of time wallowing around speculating what might be going wrong:

https://discussions.unity.com/t/839300/3

3

Hi.
I agree that something should change from 0xAA fill (that I add to debug)
the count is valid.
the write is writing (and returns the count)
the read (which originally was the symetric of the write) returns the count, but doesn’t modify the buffer

        public    override    unsafe void    Write( System.IO.BinaryWriter _writer )
        {
            _writer.Write( new System.Span<byte>( NativeArrayUnsafeUtility.GetUnsafeReadOnlyPtr(m_data), m_cnt * Stride() ) );
        }
        public    override    unsafe void    Read( System.IO.BinaryReader _reader )
        {
            System.Span<byte>    dst = new System.Span<byte>( NativeArrayUnsafeUtility.GetUnsafePtr(m_data), m_cnt * Stride() );
//            dst.Fill( 0xAA );
//            int    n = _reader.Read( dst );
            for    ( int i = 0; i < m_cnt * Stride(); i++ )
                dst[i] = _reader.ReadByte();
        }
4

it seems to be the same issue as here