Declaring and Initializing Structure Handles

STRUCT_DECL(9F) and STRUCT_INIT(9F) can be used to declare and initialize a handle and space for decoding an ioctl on the stack. STRUCT_HANDLE(9F) and STRUCT_SET_HANDLE(9F) declare and initialize a handle without allocating space on the stack. The latter macros can be useful if the structure is very large, or is contained in some other data structure.

Note - Because the STRUCT_DECL(9F) and STRUCT_HANDLE(9F) macros expand to data structure declarations, these macros should be grouped with such declarations in C code.

The macros for declaring and initializing structures are as follows:

STRUCT_DECL(structname, handle): Declares a structure handle that is called handle for a structname data structure. STRUCT_DECL allocates space for its native form on the stack. The native form is assumed to be larger than or equal to the ILP32 form of the structure.
STRUCT_INIT(handle, umodel): Initializes the data model for handle to umodel. This macro must be invoked before any access is made to a structure handle declared with STRUCT_DECL(9F).
STRUCT_HANDLE(structname, handle): Declares a structure handle that is called handle. Contrast with STRUCT_DECL(9F).
STRUCT_SET_HANDLE(handle, umodel, addr): Initializes the data model for handle to umodel, and sets addr as the buffer used for subsequent manipulation. Invoke this macro before accessing a structure handle declared with STRUCT_DECL(9F).