Essential COM
, DCE (Distributed Computing Environment ), . , (Interface Definition Language IDL). . IDL:
HRESULT f([in] const short *ps);
:
short s = 10; HRESULT hr = p->f(&s);
10 . , 10 ORPC- .
, , :
HRESULT hr = p->f(0); // pass a null pointer //
, . ? , , ? , , , ? , , , , , , . .
, . , , [ref]:
HRESULT g([in, ref] short *ps); // ps cannot be a null ptr. // ps
, [ref], (reference pointers). IDL- , , :
HRESULT hr = p->g(0); // danger: passing null [ref] ptr. // : [ref]
. p , , . , IDL- [unique]:
HRESULT h([in, unique] short *ps); // ps can be a null ptr. // ps
, [unique], (unique pointers). IDL- , , :
HRESULT hr = p->h(0); // relax: passing null [unique] ptr. // : [unique]
. , , . : , ORPC- . , , , . ORPC- . , 1, .
, [ref] [unique] . , . IDL:
HRESULT j([in] short *ps1, [in] short *ps2);
IDL- , :
short x = 100; HRESULT hr = p->j(&x, & ); // note: same ptr. passed twice // :
: ? , 100 ORPC- : *ps1 *ps2. , , . , , 100, , ps1 ps2 , . , . - :
STDMETHODIMP MyClass::j(short *ps1, short *ps2) { if (ps1 == ps2) return this->OneKindOfBehavior(ps1); else return this->AnotherKindOfBehavior(ps1, ps2); } (semantic contract) , .
[ref] [unique] , , , - . , , , IDL [ptr]:
HRESULT k([in, ptr] short *ps1, [in, ptr] short *ps2);
, [ptr], (full pointers), . IDL- , :
short x = 100; HRESULT hr = p->k(&x, &x); // note: same ptr. passed twice // :
100 , [ptr] ps1 , [ptr]. ps2 [ptr], 2, . , , ps1 ps2, .
, . , , . , ORPC- , , . , , , .
1 MIDL [ref] . , . , MIDL, , , HRESULT .
2 (ps1 == ps2), (*ps1 == *ps2); .
