Re: Further questions on interfacing to Postgres libpq

[rikki cattermole via Digitalmars-d-learn]

On 27/01/2018 5:11 AM, Joe wrote:
An example test program that I'm using to learn D to C interfacing 
(specifically calling the libpq library) has a call to a C function 
declared as follows:


     void PQprint(FILE *fout,  /* output stream */
  const PGresult *res,
  const PQprintOpt *po);

PQprintOpt is a struct whose first six members are declared as 'pqbool' 
which is in turn declared as "typedef char pqbool;" in the distributed 
Postgres header file. I've defined an "alias pqbool = char;" in the D 
file, which is pretty straightforward.


Use ubyte, not char.
char has a bunch of logic related to Unicode surrounding it which is 
clearly not the intent.


The second of the six members has the name "align", which is a D 
keyword. So I renamed it "align_" and I presume that won't cause any 
problems.


You're good, layout+size just has to match not names of fields.

To deal with the first argument to PQprint, I added "import 
core.stdc.stdio : FILE;".  The question is how to pass the D "stdout" as 
that argument.  The D compiler tells me I can't pass it as is (as was 
done in C), because in D it's of type "File".


https://dlang.org/phobos/std_stdio.html#.File.getFP

Further questions on interfacing to Postgres libpq

[Joe via Digitalmars-d-learn]

An example test program that I'm using to learn D to C 
interfacing (specifically calling the libpq library) has a call 
to a C function declared as follows:


void PQprint(FILE *fout,  /* output stream */
 const PGresult *res,
 const PQprintOpt *po);

PQprintOpt is a struct whose first six members are declared as 
'pqbool' which is in turn declared as "typedef char pqbool;" in 
the distributed Postgres header file. I've defined an "alias 
pqbool = char;" in the D file, which is pretty straightforward.


The second of the six members has the name "align", which is a D 
keyword. So I renamed it "align_" and I presume that won't cause 
any problems.


To deal with the first argument to PQprint, I added "import 
core.stdc.stdio : FILE;".  The question is how to pass the D 
"stdout" as that argument.  The D compiler tells me I can't pass 
it as is (as was done in C), because in D it's of type "File".