Re: [Pharo-project] [squeak-dev] Question about FFI and constants

Another alternative to what Andreas suggested is to reify in meaningful messages the constants, see senders of YAZODRFFILibrary>>odrCreate: in the Z3950 project at SqueakSource. Cheers, Hernán 2009/9/30 Mariano Martinez Peck <marianopeck@gmail.com>:

Hi folks: I am calling to the OpenDBX library and this library uses C constants. Suppose something like this:

enum odbxerr {     ODBX_ERR_SUCCESS, #define ODBX_ERR_SUCCESS   ODBX_ERR_SUCCESS     ODBX_ERR_BACKEND, #define ODBX_ERR_BACKEND   ODBX_ERR_BACKEND     ODBX_ERR_NOCAP, #define ODBX_ERR_NOCAP   ODBX_ERR_NOCAP     ODBX_ERR_PARAM, .........

Then I have a function like this:

char* odbx_error( odbx_t* handle, int error )

In that case the int error es the index of the array or I can use the constant. Right now, I am using int from 0 to N. But I would like to invoke calls to that function using Smalltalk Strings that represent C constants.

For example, now I have this:

OpenDBXUnix>>apiError: handle number: err     "long odbx_error(odbx_t*, int)"     <cdecl: char* 'odbx_error' (ulong long) module: 'opendbx' >     ^self externalCallFailed

And I call them this way for example:

OpenDBXUnix apiError:  handle number: 1.

But, I would love to do:

OpenDBXUnix apiError:  handle number: 'ODBX_ERR_BACKEND'.

Of course this fails because it cannot coerce and String to a long.

So, that someone know how can I do this (if I can) ?

Thanks

Mariano