2.20.2.4 struct x1f4_function_type

typedef struct x1f4_function_type {
    const char *name;
    int (*function) (void *, void *, void **), type;
    const int *args;
    unsigned count, flags, length;
} x1f4_function_type;

The struct x1f4_function_type record describes symbolic functions.

name

The name field is the function name. A valid C identifier is expected for the function name, thus the first character in the function name may be a letter or an underscore (_), while the rest may be letters, digits or underscores (_s).

length

The length field is the function name length, i.e. the number of characters (not including the terminal null) making up the function name.

type

The type field is the function symbolic type, i.e. the type to which it evaluates. It may be one of X1f4_E4_MODE, X1f4_E4_REAL, X1f4_E4_TEXT and X1f4_E4_VOID or it may indicate an application defined opaque type, case in which it is greater than X1f4_E4_LAST.

See Symbolic Types.

See Application Defined Types.

flags

The flags field is a bitwise OR of zero or more operator and function flag bits and function flag bits.

See Operator And Function Flags.

See Function Flags.

count

The count field indicates the function number of arguments.

args

The args field indicates the type of function arguments. It should point a memory location at which an int array of count elements is stored. The type of one function argument is indicated by the corresponding array element, i.e. the type of the first function argument is indicated by the first array element, the type of the second function argument is indicated by the second array element and so on. The type of function arguments may be one of X1f4_E4_MODE, X1f4_E4_REAL and X1f4_E4_TEXT or it may indicate an application defined opaque type, case in which it is greater than X1f4_E4_LAST.

See Symbolic Types.

See Application Defined Types.

If the function definition includes flags lists for function arguments (and thus X1f4_E4_POST_TYPE bit is present in the flags field) the args array is expected to be double allocated to provide for argument flags lists.

See Function Argument Flags.

Thus, the next count elements in the args following the first count elements specify the flags lists of the function arguments.

The function argument flags lists are interpreted as bitwise ORs of zero or more operator and function argument flag bits.

These extra args elements are observed by the expression evaluator if and only if the X1f4_E4_POST_TYPE bit is present in the flags field of the function definition.

function

The function field is the address of the routine performing the symbolic function logic.

The routine is supplied three arguments when called. The first is the execution context, an application supplied pointer that is otherwise not interpreted by the expression evaluator. The second is the address at which the function result, if any, is to be stored. The third is an array of addresses from which the function arguments, if any, are to be read.

The routine is expected to return 0 if it completes execution successfully, non zero otherwise. In the later case the expression evaluation will be terminated.