Some more Buffer and Memory Fixes

[tinyzimmer]

• Fixes Buffer.FillBytes to work on Windows as well with the same fixes from NewBufferFromBytes
• Make calling Map on a Memory or Buffer safe to do multiple times (while still only requiring a single Unmap)

[tinyzimmer]

@vshashi01 I think this should suffice

[tinyzimmer]

Getting rid of these as I am not sure if they were implemented correctly and I feel like most users would be working with []byte sequences anyway. May consider reimplementing in the future.

[vshashi01]

Indeed I think keep just the FillBytes is good enough.

[vshashi01]

Another thing that I just thought of is as soon as the MapInfo is created, at the moment there is no way to check if its read only or writable as well. Do you think this should be available with the API as well. Though I think for small programs this is hardly ever a problem. The rest of it looks good.

[tinyzimmer]

Well to be clear the user has to specify how they are mapping the data the first time. That being said, I can see what you mean if the user maps once read, and then goes again to map write. It's probably worth at the very least adding documentation saying that if you call it twice, the memory will remain mapped with the access provided the first time, at least until you Unmap and Map again.

I think these are edge cases, because how much processing would you really be doing in the context of a single buffer? In my head, most of the time you'd create your data, shove it in there and let gstreamer take over. Or on the receiving end, you'd just pull the buffer into go memory with Bytes() and work from there.

EDIT: I guess I'll add that the mode on the memory is accessible with something like...

mapInfo := buffer.Map(gst.MapWrite | gst.MapRead)
if mapInfo.Flags()&gst.MapWrite != 0 {
    fmt.Println("Map has write access")
}
if mapInfo.Flags()&gst.MapRead != 0 {
    fmt.Println("Map has read access")
}

If this is what you meant by exposing an API for determining how the memory is mapped.

[vshashi01]

Yes this is good enough...