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Resolved Declaring external function call with pointer to structure WITHOUT declaring structure itself

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  1. Jörg Walter
    Jörg Walter
  2. PowerBuilder
  3. Friday, 18 August 2017 12:11 PM UTC

Hi

I want to use a DLL, in which Functions require as parameter and yield pointers to a certain structure.

 

Let's say I have a library header:

 

struct StructType

{

int a;

void* p;

};

extern _declspec(dllimport) StructType* Func(StructType*,bool);

I want to PB-write something like this:

declare pointer here as p

p = Func(p, true)

I dont care about the contents of the struct. I want to treat a pointer to that structure type as ... a long value or something like that.

How do I declare an external function for this?

 

 

 

  1. Function
  2. DLL
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Accepted Answer
Bruce Armstrong
Bruce Armstrong Accepted Answer Pending Moderation
  1. Friday, 18 August 2017 14:46 PM UTC
  2. PowerBuilder
  3. # Permalink

>>struct StructType
​>>{
>>int a;
>>void* p;
>>};

>>extern _declspec(dllimport) StructType* Func(StructType*,bool);
>>How do I declare an external function for this?

You still have to declare the structure, but you define the second attribute as a long because it is a pointer

mystruct
int a
long p

Declare your local external function as:

FUNCTION myStruct Func ( myStruct struct, boolean flag ) LIBRARY "libname"

Call it as:

mystruct struct
struct = Func ( struct, true ) 

The p attribute of the structure will be your pointer.

See 

http://infocenter-archive.sybase.com/help/index.jsp?topic=/com.sybase.dc37781_1150/html/psref/CCJBAEEF.htm
Comment
Jörg Walter
  1. Jörg Walter
  2. Monday, 21 August 2017 08:52 AM UTC
Thanks for the answers!



A follow-up:



In the struct I actually have the following types:



struct StructType



{



size_t a; // 32 bit or maybe 64 bit



char name[MAX_CHARS];



SomeEnumType type;



};



How do I translate these types into PB types?



I see this:



http://infocenter-archive.sybase.com/help/index.jsp?topic=/com.sybase.dc37781_1150/html/psref/BCGEGBDD.htm



and would translate it into



UnsignedInteger a;



Blob name; // ??? or : char name [1000]; ?



integer type;



Is that correct?



I tried the listed and got a bad runtime function reference error.



A call to a function in the same DLL without parameters or return type succeeded.



A call to a function with extern _declspec(dllimport) StructType* Func();



succeeded  when I declared it as:



FUNCTION long Func() LIBRARY "mydll.dll"



At least I got a long value back that smelled like a valid pointer



 



 

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Responses (2)
Roland Smith
Roland Smith Accepted Answer Pending Moderation
  1. Saturday, 19 August 2017 22:09 PM UTC
  2. PowerBuilder
  3. # 1

In the external function declaration you can use "structure" as the datatype.

Comment
Jörg Walter
  1. Jörg Walter
  2. Monday, 28 August 2017 13:12 PM UTC
Thanks for the answers!



A follow-up:



In the struct I actually have the following types:



struct StructType



{



size_t a; // 32 bit or maybe 64 bit



char name[MAX_CHARS];



SomeEnumType type;



};



How do I translate these types into PB types?



I see this:



http://infocenter-archive.sybase.com/help/index.jsp?topic=/com.sybase.dc37781_1150/html/psref/BCGEGBDD.htm



and would translate it into



UnsignedInteger a;



Blob name; // ??? or : char name [1000]; ?



integer type;



Is that correct?



I tried the listed and got a bad runtime function reference error.



A call to a function in the same DLL without parameters or return type succeeded.



A call to a function with extern _declspec(dllimport) StructType* Func();



succeeded  when I declared it as:



FUNCTION long Func() LIBRARY "mydll.dll"



At least I got a long value back that smelled like a valid pointer

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