Basics of calling C from D

[Colin via Digitalmars-d-learn]

On Wednesday, 11 June 2014 at 15:14:19 UTC, Colin wrote:
> On Wednesday, 11 June 2014 at 14:28:49 UTC, belkin wrote:
>> On Wednesday, 11 June 2014 at 14:02:08 UTC, John Colvin wrote:
>>> On Wednesday, 11 June 2014 at 13:52:09 UTC, belkin wrote:
>>>> Example: I have this C function that is compiled into a 
>>>> library
>>>>
>>>> //File: factorial.h
>>>> int factorial(int n);
>>>>
>>>>
>>>> //File: factorial.c
>>>> #include "factorial.h"
>>>>
>>>> int factorial(int n)
>>>> {
>>>>  if(n!=1)
>>>>   return n*factorial(n-1);
>>>> }
>>>>
>>>> Question: How do I use it from D?
>>>
>>> //File: blah.d
>>>
>>> extern(C) int factorial(int n); //coincidentally identical to 
>>> the C declaration.
>>>
>>> void main()
>>> {
>>>   assert(factorial(3) == 6);
>>> }
>>>
>>>
>>> $ gcc -c factorial.c -ofactorial.o
>>> $ dmd blah.d factorial.o
>>> $ ./blah
>>>
>>> or
>>>
>>> $ gcc -c factorial.c -ofactorial.o
>>> $ ar rcs libfactorial.a factorial.o
>>> $ dmd blah.d -L-lfactorial
>>> $ ./blah
>>>
>>>
>>>
>>> Basically, you just translate the header files from C to D, 
>>> then link to the C implementation. See 
>>> http://code.dlang.org/packages/dstep for automatic 
>>> translation of headers.
>>
>> This is great.
>> How practical (reliable ) is it to translate a large and 
>> complex header file like oci.h ( the interface for Oracle's 
>> database API ) to D?
>
> You can do a lot of it by simply doing a find and replace in the
> file.
> For example, all C definitions of:
> unsigned char x
> become:
> ubyte x
>
> So a find an replace will do that for you quite easily.
> Other things like structs and typedefs are a bit more difficult
> to do with a find & replace.
> All the info you need is here anyway:
> wiki.dlang.org/Bind_D_to_C

And here:
http://dlang.org/interfaceToC.html