Studio:Scl ptr

The scl_ptr pragma

The scl_ptr pragma is used to identify a pointer data type and assign it pointer-specific attributes, such as marshaling direction and memory usage.

Syntax

#pragma scl_ptr(type-name, direction, usage)

#pragma scl_ptr(type-name, field-name, direction, usage)

Parameters	Type	Description
type-name	Type	Name of the type that contains the pointer. The container type can be a structure, union, the pointer type itself, or a function. If the container type is a structure or union, the pointer is a member and the field-name must be specified. If the container type is a function, then the pointer is a parameter and the field-name must be specified.
field-name [Optional]	Member	Name of the pointer field, which may be a member field contained within a structure/union, or a parameter in the ParameterList of a function.
direction	String	Direction in which the pointer data is marshaled; refer to the Pointer Direction Table below. This affects read and write access to the pointer data.
usage	String	Pointer usage indicator; refer to the Pointer Memory Usage Table below.

Pointer Direction Table

Value	Meaning
"IN"	Specifies that the pointer memory can be used only as input to the receiver of the pointer. The Owner of the interface may only consider this read-only memory.
"OUT"	Specifies that the pointer memory can be used to output information. The memory is allocated by the User and only written to by the Owner.
"INOUT"	Specifies that the pointer memory can be used as both input and output. The User may send in data when sending the command (or calling the function), and may read the Owner’s output upon receipt of the response (or return of the function).
"RETURN"	Specifies that the pointer memory may be read by the User of the interface. The User may only consider this as read-only memory and must not free it.
"INRETURN"	Specifies that the pointer memory is allocated by both user and owner. There is no single block of memory pointed to by an "INRETURN" pointer. Rather there is one block on the call (or message send) and a second block on the return (or completion of the two-way message). Thus the first block has the characteristics of an "IN" block and the second the characteristics of a "RETURN" block.

Pointer Memory Usage Table

Value	Meaning
"PRIVATE"	Pointer memory is private and may not be released by the Reader.
"POOL"	Pointer memory is created from common pool and must be released by the Reader.

Notes

• A compiler error will be reported if an pointer does not point to a fixed size type.
• Response payloads cannot use the "OUT" or "INOUT" direction.
• Pointers with "OUT" or "INOUT" direction cannot indicate POOL pointer usage.
• One-way messages (command and response) cannot have data that contains an "OUT" or "INOUT" Pointer.
• The pointers declared type cannot be pointer to void; e.g., void *. This is considered an opaque pointer.
• For additional information on scl_ptr, including constraints, refer to the section on scl_ptr in the SCL Reference Guide.
• As of STRIDE 3.0.0102 the direction and usage attributes are not symbolic tokens anymore. They became string literals (need to be quoted). See this page for details.

Examples

Two examples using the scl_ptr pragma are shown below:

1. The first example uses the scl_ptr pragma to assign pointer attributes to a structure member and a parameter list member.
2. The second example uses the scl_ptr pragma to assign pointer attributes to type definitions.

Example 1

/* Typedef defining a structure with a member of type pointer to char */
typedef struct
{
  int f1;
  char * f2;
}data_t;

/* Function prototype with an "INOUT" pointer of type data_t */
void modifyData( data_t * p );

/* Use the scl_function pragma to associate a SUID with the function ModifyData */
#pragma scl_function( modifyData )
/* Use the scl_ptr pragma to define the member f2 as a "RETURN" pointer */
#pragma scl_ptr( data_t.f2, "OUT", "PRIVATE" )
/* Use the scl_ptr pragma to define the parameter p as an "INOUT" pointer */
#pragma scl_ptr( modifyData.p, "INOUT", "PRIVATE" )

Example 2

/* Typedef defining a pointer as a status type */
typedef int * StatusCode;

/* Apply scl_ptr to the StatusCode type. It is always an "OUT" pointer type */
#pragma scl_ptr ( StatusCode, "OUT", "PRIVATE" );

/* Prototype defining a function that returns a pointer to the data structure */
void GetStatus( StatusCode outCode );

/* Mark getStatus as an SCL-compliant function */
#pragma scl_function ( GetStatus );