equivilent of java's float buffer

[codifiesParticipant]

I want to be able to build and maintain a chunk of “raw” memory that I could (easily) put float values into and then send a pointer to a c library

I notice the GLES module uses ptr but I’m not too sure about the correct way to use this, for example, are “normal” mx2 float arrays guaranteed to be contiguous in memory…

[nerobotParticipant]

mx2 arrays are cpp arrays (because all mx-code translated to cpp before compiling), so they must be contiguous in memory, I think.

[Mark SiblyKeymaster]

are “normal” mx2 float arrays guaranteed to be contiguous in memory…

Yes, and arrays also have a ‘Data’ property that returns the raw memory used by the array in the form of a pointer, eg: an Int[] will return an Int Ptr.

You can also use a DataBuffer and poke in values using PokeFloat etc, or even a Stack<Float> which also has a Data property only it returns the underlying array, eg:

Monkey

Local buf:=New Stack<Float> For Local i:=0 until 1000 buf.Push( i ) Next Local rawData:=buf.Data.Data 'A float ptr pointing to 0,1,2,3...!

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Local buf:=New Stack<Float> For Local i:=0 until 1000     buf.Push( i ) Next Local rawData:=buf.Data.Data    'A float ptr pointing to 0,1,2,3...!

Also note that if the stack is modified, the underlying array may have to be resized (therefore changed) so you need to be a bit careful using stack like this.

[codifiesParticipant]

thanks thats a great help I ended up with…

Monkey

Local texture:GLuint[] = New GLuint[1] texture[0]=123 ' any old value to see some change glGenTextures(1,texture.Data) Print("texture ="+texture[0])

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Local texture:GLuint[] = New GLuint[1] texture[0]=123 ' any old value to see some change glGenTextures(1,texture.Data) Print("texture ="+texture[0])

I assume this is only safe as long as texture never leaves scope or is global

looks like its much closer to the “metal” than I thought which is nice…

[Mark SiblyKeymaster]

Yep, that should work. There’s also Varptr:

Monkey

Local texture:GLuint glGenTextures( 1,Varptr texture )

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Local texture:GLuint glGenTextures( 1,Varptr texture )

And of course there always good old ‘malloc’:

Monkey

Local fp:=Cast<Float Ptr>( libc.malloc( 1024 ) ) fp[0]=1 fp[1]=2 libc.free( fp )

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Local fp:=Cast<Float Ptr>( libc.malloc( 1024 ) ) fp[0]=1 fp[1]=2 libc.free( fp )

looks like its much closer to the “metal” than I thought which is nice…

You can indeed use it *very* close to the metal! The general idea is that if you write code without the use of pointers, the code should be 100% ‘safe’. Once you go into pointer land you’re on your own so you need to be careful, but at the same time mx2 doesn’t do anything to stop you doing this if you want/need to.

[codifiesParticipant]

I managed to find varptr and Cast<type> by grep-ing …

Its interesting that I like I can get to the “metal”, but equally love the fact that it uses actual human readable words in the code, I’ve been using Java for a while since the days of BlitzMax but its just getting too much ASCII soup and every shiny new fashionable language feature, sometimes you just want easy to read code, but that shouldn’t mean lack of power.

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