Help with Pointers.

[bigandParticipant]

Hey all.

Can somebody give me a little help with pointers please?

I am specifically wanting to work with SDL_MIXER and these functions:

Function Mix_LoadMUS:Mix_Music Ptr( file:CString Ptr )
Function Mix_FreeMusic( music:Mix_Music Ptr )
Function Mix_PlayMusic:Int( music:Mix_Music Ptr, loops:Int )

I understand pointers in C but I haven’t ever used them in Monkey before, so not sure how I should be declaring or even working with them. I have searched the forum but it just will not go in my thick skull.

Its like the first function above, I can’t even get my head around how I even pass the filename. I know in C it wants:
const char *file

But just not sure how to translate that to Monkey.

Just getting frustrated I guess as I know its a fingertip away from making sence.

Thanks in advance.

[Mark SiblyKeymaster]

Monkey pointers are similar to C pointers, only they use ‘Ptr’ instead of ‘*’ and ‘Varptr’ instead of ‘&’, eg:

Monkey

Function Main() Local i:Int=10 Local p:Int Ptr=Varptr i p[0]*=10 Print i End

1 2 3 4 5 6 7

Function Main()    Local i:Int=10    Local p:Int Ptr=Varptr i    p[0]*=10    Print i End

Also, you need to use ‘[]’ to dereference a pointer, so ‘p[0]’ is the same as ‘(*p)’ in C.

‘CString’ is a built-in type that should only appear in extern blocks and basically means ‘const char *’. It can be used as if it were a normal monkey2 string. So whenever you see ‘CString’ in a monkey2 extern block, just think ‘const char*’.

Note there is an error in the sdl-mixer file: ‘Function Mix_LoadMUS:Mix_Music Ptr( file:CString Ptr )’ is wrong as ‘CString Ptr’ is actually a ‘const char **’! This should just be ‘file:CString’. I have just pushed a fix for this to the develop branch at github. However, you can always just fix this yourself and update modules if you want.

I have not actually tried the sdl-mixer module myself as it has a dependancy on a shared library for decoding music etc that I wasn’t sure how to build/use. There is however a vsynth demo in bananas that using the module just for playing audio.

[bigandParticipant]

Awesome Mark, thats exactly what I needed to read.

The vsynth demo was what got me looking at sdl_mixer in the first place.

As you may remember I had issues with playing a load of OGG files but if I can get the original XM module working, that will save me a LOT of hassle as well as memory (the original XM file with all the music in it is as big as just one OOG file).

[Author]

Posts