[Original] C # function pointer for cross-platform Calling C ++

In this article, we will focus on the columns. We can clearly see how to use C # To call C ++.Code.

Column: a standard Win32 API library cclic in C ++. in DLL, there is a function void * winapi getfunctionaddress (unsigned int Sn). This function obtains the function pointer, that is, the address of a function by passing the SN number. then call other functions through the returned address.

Then we must know the function structure corresponding to a Sn, such as Sn = 1-> bool winapi ccaskserverlicenseinfo (const char * server_address, unsigned short port, pcclic_info plicenseinfo)

In

 

Typedef struct _ cclic_info {

Char ower [64];

Unsigned short Manage_ip;

Unsigned short Ramained_ip;

Unsigned short Useable_time;

Unsigned char Type;

} Cclic_info, * pcclic_info;

The purpose of this column is to call the ccaskserverlicenseinfo function through C.

 

[Dllimport ( @" Cclic. dll " )]
Public   Static   Extern System. intptr matrix (system. uint32 Sn); // famous entry function
// Define the function pointer Model
Public   Delegate System. int32 ccaskserverlicenseinfohandle (system. String servername, system. uint16 port, system. intptr );

Public static licenseinfo getlicentinfo (string Server, System. uint16 port)
{

System. intptr fptr = matrix (1); // obtainCcaskserverlicenseinfo addressCcaskserverlicenseinfohandle ccaskserverlicenseinfo=Marshal. getdelegateforfunctionpointer (fptr,Typeof(Ccaskserverlicenseinfohandle ))AsCcaskserverlicenseinfohandle; // converts an address to a function pointer in C #.

Licenseinfo info =   New Licenseinfo (); // name structure and initialization
Intptr infoptr = Marshal. alloccotaskmem (marshal. sizeof (Info); // converts struct to pointer
Ccaskserverlicenseinfo (server, port, infoptr); // call a function
Info = (Licenseinfo) Marshal. ptrtostructure (infoptr, Typeof (Licenseinfo); // converts a pointer to a struct.
Return Info;
}

[Structlayout (layoutkind. Sequential, charset = Charset. ANSI)]
Public   Struct Licenseinfo
{
[Financialas (unmanagedtype. byvalarray, sizeconst =   64 )]
Public System. Char [] ower;
Public System. uint16 manage_ip;
Public System. uint16 ramained_ip;
Public System. uint16 useable_time;
Public System. byte type;
}

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[dllimport ( @" cclic. DLL " )]
Public static extern system. intptr matrix (system. uint32 Sn);

Public DelegateSystem. int32 ccaskserverlicenseinfohandle (system. String servername, system. uint16 port, system. intptr );

Public   Static Licenseinfo getlicentinfo (string Server, System. uint16 port)
{
System. intptr fptr = Matrix ( 8 );
Ccaskserverlicenseinfohandle ccaskserverlicenseinfo = Marshal. getdelegateforfunctionpointer (fptr, Typeof (Ccaskserverlicenseinfohandle )) As Ccaskserverlicenseinfohandle;
Licenseinfo info =   New Licenseinfo ();
Intptr infoptr = Marshal. alloccotaskmem (marshal. sizeof (Info ));
Ccaskserverlicenseinfo (server, port, infoptr );
Info = (Licenseinfo) Marshal. ptrtostructure (infoptr, Typeof (Licenseinfo ));
Return Info;