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[squeak-dev] Question about FFI and constants

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Mariano Martinez Peck

[squeak-dev] Question about FFI and constants

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

Andreas.Raab

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

Use symbolic constants (pool/class vars), i.e.,

ODBXConstants class>>initialize
ODBXErrSuccess := 1.
"..."

and then

OpenDBXUnix apiError: handle number: ODBXErrBackend.

Cheers,
- Andreas

Mariano Martinez Peck wrote:

> 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
>
>
>
> ------------------------------------------------------------------------
>
>

hernanmd

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

In reply to this post by Mariano Martinez Peck

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 <[hidden email]>:

> 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
>
>
>
>
>
>