[geekraver]

Originally Posted by igorsk

Is this better?

struct Request {
 DWORD reqNo;
 DWORD reserved[2];
 DWORD extralen;
};
struct Answer {
 DWORD reserved[3];
 DWORD dataLen;
 char  data[1]; //variable length
};
struct SendBuffer {
 DWORD type; //0x10005 for WriteFile
 DWORD reserved[2];
 DWORD dataLen;
 char  data[1]; //variable length
};

int UsbReceiveProc(Request* request, size_t answersize, Answer* answer);
void UsbBuffFree(Answer* answer);
int UsbSendProc(Request* request, SendBuffer* buf, size_t sendsize, DWORD* bytesSent);

Every request and answer further defines the variable data part, e.g.:

struct FileOpenRequest: Request {
 DWORD nPathLen;
 char path[1]; //variable length
};
struct FileOpenAnswer: Asnswer {
 DWORD hFile;
};

Couple of questions about this:

1) is the size that gets passed through for the read data just for the extra stuff; i.e. for FileOpen it would be "sizeof(FileOpenAnswer) - 16"?

2) Should the "Answer* answer" arg in UsbReceiveProc actually be "Answer** answer", i.e. something like:

FileOpenAnswer *pAns = 0;
HREF hErr = UsbReceiveProc(pReq, sizeof(FileOpenAnswer)-16, &pAns);
if (hErr == 0)
{
    // do something with the answer
    ...
    // free the answer
    UsbFreeProc(pAns);
}