# phpman > man > ffi_call(3)

[ffi_call(3)](https://www.chedong.com/phpMan.php/man/fficall/3/markdown)              BSD Library Functions Manual              [ffi_call(3)](https://www.chedong.com/phpMan.php/man/fficall/3/markdown)

## NAME
     **ffi**___**call** — Invoke a foreign function.

## SYNOPSIS
### #include <ffi.h>

     _void_
     **ffi**___**call**(_ffi_cif_ _*cif_, _void_ _(*fn)(void)_, _void_ _*rvalue_, _void_ _**avalue_);

## DESCRIPTION
     The **ffi**___**call** function provides a simple mechanism for invoking a function without requiring
     knowledge of the function's interface at compile time.  _fn_ is called with the values retrieved
     from the pointers in the _avalue_ array. The return value from _fn_ is placed in storage pointed to
     by _rvalue_.  _cif_ contains information describing the data types, sizes and alignments of the ar‐
     guments to and return value from _fn_, and must be initialized with **ffi**___**prep**___**cif** before it is
     used with **ffi**___**call**.

     _rvalue_ must point to storage that is sizeof(ffi_arg) or larger for non-floating point types.
     For smaller-sized return value types, the **ffi**___**arg** or **ffi**___**sarg** integral type must be used to
     hold the return value.

## EXAMPLES
     #include <ffi.h>
     #include <stdio.h>

     unsigned char
     foo(unsigned int, float);

     int
     main(int argc, const char **argv)
     {
         ffi_cif cif;
         ffi_type *arg_types[2];
         void *arg_values[2];
         ffi_status status;

         // Because the return value from foo() is smaller than sizeof(long), it
         // must be passed as ffi_arg or ffi_sarg.
         ffi_arg result;

         // Specify the data type of each argument. Available types are defined
         // in <ffi/ffi.h>.
         arg_types[0] = &ffi_type_uint;
         arg_types[1] = &ffi_type_float;

         // Prepare the ffi_cif structure.
         if ((status = ffi_prep_cif(&cif, FFI_DEFAULT_ABI,
             2, &ffi_type_uint8, arg_types)) != FFI_OK)
         {
             // Handle the ffi_status error.
         }

         // Specify the values of each argument.
         unsigned int arg1 = 42;
         float arg2 = 5.1;

         arg_values[0] = &arg1;
         arg_values[1] = &arg2;

         // Invoke the function.
         ffi_call(&cif, FFI_FN(foo), &result, arg_values);

         // The ffi_arg 'result' now contains the unsigned char returned from foo(),
         // which can be accessed by a typecast.
         printf("result is %hhu", (unsigned char)result);

         return 0;
     }

     // The target function.
     unsigned char
     foo(unsigned int x, float y)
     {
         unsigned char result = x - y;
         return result;
     }

## SEE ALSO
     [ffi(3)](https://www.chedong.com/phpMan.php/man/ffi/3/markdown), [ffi_prep_cif(3)](https://www.chedong.com/phpMan.php/man/ffiprepcif/3/markdown)

                               February 15, 2008