FFI Structure Help

> -----Original Message-----
> From: [hidden email] [mailto:squeak-dev-
> [hidden email]] On Behalf Of Ron Teitelbaum
> Sent: Monday, August 14, 2006 4:32 PM
> To: 'The general-purpose Squeak developers list'
> Subject: FFI Structure Help
>
> Hello all,
>
> I'm still having some trouble with FFI and was wondering if someone could
> help explain why this is not working.
>
> The following works on C++
>
> typedef struct _CRYPT_KEY_PROV_INFO {
>     LPWSTR                  pwszContainerName;
>     LPWSTR                  pwszProvName;
>     DWORD                   dwProvType;
>     DWORD                   dwFlags;
>     DWORD                   cProvParam;
>     PCRYPT_KEY_PROV_PARAM   rgProvParam;
>     DWORD                   dwKeySpec;
> } CRYPT_KEY_PROV_INFO, *PCRYPT_KEY_PROV_INFO;
>
> typedef struct _CRYPT_KEY_PROV_PARAM {
>     DWORD           dwParam;
>     BYTE            *pbData;
>     DWORD           cbData;
>     DWORD           dwFlags;
> } CRYPT_KEY_PROV_PARAM, *PCRYPT_KEY_PROV_PARAM;
>
> The equivilent on squeak:
>
> Win32FFICertKeyProviderInfo class>>fields
> fields
>
> ^#(
> (pwszContainerName 'char *')
> (pwszProvName 'char *')
>   (dwProvType 'long')
> (dwFlags 'long')
> (cProvParam 'long')
> (rgProvParam 'Win32FFICertKeyProviderParameter')
> (dwKeySpec 'long')
>   )
>
> Win32FFICertKeyProviderParameter class >> fields
>
> ^#(
> (dwParam 'long')
> (pbData 'byte *')
> (cbData 'long')
> (dwFlags 'long')
>   )
>
> The calls in C++:
>
> CertGetCertificateContextProperty(
>     pCertContext,                 // A pointer to the certificate
>                                   // where the property will be set.
>     CERT_KEY_PROV_INFO_PROP_ID,   // An identifier of the property to get.
>                                   // In this case,
>                                   // CERT_KEY_PROV_INFO_PROP_ID
>     NULL,                         // NULL on the first call to get the
>                                   // length.
>     &cbData)
>
> Returns 200.
>
> In squeak:
>
> getCertProviderInfoSize
>
> "#define CERT_KEY_PROV_INFO_PROP_ID          2"
>
> | buffer result |
> [buffer := (ExternalAddress allocate: 4).
> self class certGetCertificateContextProperty: self
> selectedCertificate getHandle asInteger property: 2 structPointerOrNull:
> nil
> buffer: buffer asInteger
>
> ] ensure: [
> result := buffer unsignedLongAt: 1.
> buffer free.
> ].
> ^result
>
> Returns 200.  So this apparently works!
>
> Here is the problem:
>
> In C++:
>
> if(!(pCryptKeyProvInfo = (CRYPT_KEY_PROV_INFO *)malloc(cbData)))
>      {
>              MyHandleError("Error in allocation of memory.");
>      }
>      if(CertGetCertificateContextProperty(
>                 pCertContext,
>                 CERT_KEY_PROV_INFO_PROP_ID,
>                 pCryptKeyProvInfo,
>                 &cbData))
>      {
>                printf("\n The current key container is %S.",
>                    pCryptKeyProvInfo->pwszContainerName);
>      }
>
> Works fine.
>
> In squeak:
>
> Win32FFICertificateStore>>getCertProviderInfo
>
> "#define CERT_KEY_PROV_INFO_PROP_ID          2"
>
> | providerInfo aHandle |
> aHandle := ExternalAddress allocate: self getCertProviderInfoSize.
> providerInfo := Win32FFICertKeyProviderInfo fromHandle: aHandle.
> self class certGetCertificateContextProperty: self
> selectedCertificate getHandle asInteger property: 2 structPointerOrNull:
> aHandle asInteger buffer: self getCertProviderInfoSize.
> self certProviderInfo: providerInfo.
>
>
> Win32FFICertificateStore class>>certGetCertificateContextProperty:
> aContext
> property: aProperty structPointerOrNull: pvData buffer: aBuffer
>
> "BOOL WINAPI CertGetCertificateContextProperty(
>   PCCERT_CONTEXT pCertContext,
>   DWORD dwPropId,
>   void* pvData,
>   DWORD* pcbData
> );
> "
>
> <apicall: bool 'CertGetCertificateContextProperty' (long long long
> long) module: 'crypt32.dll'>
> ^self externalCallFailed
>
> Blows up with a C0000005 access violation error.
>
> I've tried changing the external type form long to
> Win32FFICertKeyProviderInfo, and I've tried initializing the
> Win32FFICertKeyProviderInfo rgProvParam: Win32FFICertKeyProviderParameter
> new.
>
> I've tried using externalNew instead of allocating 200 bytes in an
> external
> address on both structures.  But that hasn't worked; I still get the same
> error.
>
> I've even tried sending in a ByteArray new: 200, as a handle but that came
> back with can not coerce arguments.
>
> Sorry if I've been a bit of a pest.  Now that I have the code I need
> working
> in C++ I was hoping that the translation to squeak would go smoothly.  I'm
> sure I'm missing something, any suggestions are welcome!
>
> Ron Teitelbaum
>
>