Using Postgres connection functions

[Adam D. Ruppe]

On Saturday, 13 January 2018 at 04:17:02 UTC, Joe wrote:
> It only compiled after I removed the second 'const' in the 
> first and second arguments.

Yeah, D's const applies down the chain automatically, so you 
don't write it twice there.

> string[] keywords = ["hostaddr", "port", "dbname"];
> string[] values = ["127.0.0.1", "5432", "testdb"];

>     conn = PQconnectdbParams(cast(const char **)kws,
>                              cast(const char **)vals, 1);
>
> So my question is: is there an easier or better way of passing 
> two arrays of C null-terminated strings to an extern(C) 
> function?

If and only if the values are known at compile time, you can do:

const char** keywords = ["hostaddr".ptr, "port".ptr, 
"dbname".ptr, null].ptr;

or even do it inline:


PQconnectdbParams(["hostaddr".ptr, "port".ptr, "dbname".ptr, 
null].ptr, ditto_for_values, 1);



Otherwise, what you did there is decent... being a C style of 
array of arrays, it will need to be coded in a C style with stuff 
like malloc and toStringz to convert D to C strings too.