pinters to structs etc...

BlitzMax Forums/BlitzMax Programming/pinters to structs etc...

Nigel Brown

(Posted 2006) [#1]

I am returning a pointer to a type:

Type PmDeviceInfo
	Field	structVersion:Int
	Field	interf:Byte Ptr
	Field	name:Byte Ptr
	Field	Input:Int
	Field	output:Int
	Field	opened:Int
EndType

the values I get returned seem ok but I am having trouble accessing the fields interf and name. I use this code to print the returned strings:

Global deviceinfo:PmDeviceInfo = New PmDeviceInfo
MemCopy( Byte Ptr(deviceinfo), Pm_GetDeviceInfo(0), SizeOf(PmDeviceInfo) )
DebugLog "version = " + deviceinfo.structVersion
DebugLog "interf = " + String.FromCstring(Varptr(deviceinfo.interf))
DebugLog "name = " + String.FromCstring(Varptr(deviceinfo.name))

I think the debuglog is trying to print the variable and not the string pointed to by the variable? any suggestions? please.

Yan	(Posted 2006) [#2]

DebugLog "interf = " + String.FromCstring(deviceinfo.interf)
DebugLog "name = " + String.FromCstring(deviceinfo.name)

Nigel Brown

(Posted 2006) [#3]

DebugLog "interf = " + String.FromCstring(deviceinfo.interf)
DebugLog "name = " + String.FromCstring(deviceinfo.name)

these two lines should print the string retuned in the structure PmDeviceInfo, the problem I feel is that deviceinfo.name and deviceinfo.interf are (byte ptr) not actual C strings.
I have now uploaded the BlitzMAX module and test application to the website if you want to try it?

Dreamora

(Posted 2006) [#4]

What is it then if not C string?
Either it is a 0 terminated char array ( memory block ) -> C String or it isn't. In the later case it would mean that it is a structure itself ...

Nigel Brown

(Posted 2006) [#5]

the pointer returned from the call to Pm_GetDeviceInfo() is a pointer to a struct of type:

typedef struct {
int structVersion;
const char* interf;
const char* name;
int input;
int output;
int opend;
}

my blitz interpretation of this is:

Type PmDeviceInfo
	Field	structVersion:Int
	Field	interf:Byte Ptr
	Field	name:Byte Ptr
	Field	Input:Int
	Field	output:Int
	Field	opened:Int
EndType

so all I want to do is print the strings pointed to by interf and name?