168 lines
3.3 KiB
HTML
168 lines
3.3 KiB
HTML
|
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
|
<HTML><HEAD><TITLE>Man page of ffi_call</TITLE>
|
|
</HEAD><BODY>
|
|
<H1>ffi_call</H1>
|
|
Section: C Library Functions (3)<BR><A HREF="#index">Index</A>
|
|
<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
|
|
<BR>BSD mandoc<BR>
|
|
<A NAME="lbAB"> </A>
|
|
<H2>NAME</H2>
|
|
|
|
<B>ffi_call</B>
|
|
|
|
- Invoke a foreign function.
|
|
|
|
<A NAME="lbAC"> </A>
|
|
<H2>SYNOPSIS</H2>
|
|
|
|
In ffi.h
|
|
|
|
Ft void
|
|
|
|
Fo ffi_call
|
|
|
|
Fa ffi_cif *cif
|
|
|
|
Fa void (*fn)(void)
|
|
|
|
Fa void *rvalue
|
|
|
|
Fa void **avalue
|
|
|
|
Fc <A NAME="lbAD"> </A>
|
|
<H2>DESCRIPTION</H2>
|
|
|
|
|
|
|
|
The
|
|
<B>ffi_call</B>
|
|
|
|
function provides a simple mechanism for invoking a function without
|
|
requiring knowledge of the function's interface at compile time.
|
|
Fa fn
|
|
|
|
is called with the values retrieved from the pointers in the
|
|
Fa avalue
|
|
|
|
array. The return value from
|
|
Fa fn
|
|
|
|
is placed in storage pointed to by
|
|
Fa rvalue .
|
|
|
|
Fa cif
|
|
|
|
contains information describing the data types, sizes and alignments of the
|
|
arguments to and return value from
|
|
Fa fn ,
|
|
|
|
and must be initialized with
|
|
<B>ffi_prep_cif</B>
|
|
|
|
before it is used with
|
|
<B>ffi_call</B>
|
|
|
|
|
|
<P>
|
|
|
|
Fa rvalue
|
|
|
|
must point to storage that is sizeof(ffi_arg) or larger for non-floating point
|
|
types. For smaller-sized return value types, the
|
|
<B>ffi_arg</B>
|
|
|
|
or
|
|
<B>ffi_sarg</B>
|
|
|
|
integral type must be used to hold
|
|
the return value.
|
|
<A NAME="lbAE"> </A>
|
|
<H2>EXAMPLES</H2>
|
|
|
|
|
|
<PRE>
|
|
#include <<A HREF="file:///usr/include/ffi.h">ffi.h</A>>
|
|
#include <<A HREF="file:///usr/include/stdio.h">stdio.h</A>>
|
|
|
|
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 <<A HREF="file:///usr/include/ffi/ffi.h">ffi/ffi.h</A>>.
|
|
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;
|
|
}
|
|
</PRE>
|
|
|
|
<A NAME="lbAF"> </A>
|
|
<H2>SEE ALSO</H2>
|
|
|
|
<A HREF="/cgi-bin/man/man2html?3+ffi">ffi</A>(3),
|
|
|
|
|
|
ffi_prep_cif3
|
|
|
|
|
|
<P>
|
|
|
|
<HR>
|
|
<A NAME="index"> </A><H2>Index</H2>
|
|
<DL>
|
|
<DT id="1"><A HREF="#lbAB">NAME</A><DD>
|
|
<DT id="2"><A HREF="#lbAC">SYNOPSIS</A><DD>
|
|
<DT id="3"><A HREF="#lbAD">DESCRIPTION</A><DD>
|
|
<DT id="4"><A HREF="#lbAE">EXAMPLES</A><DD>
|
|
<DT id="5"><A HREF="#lbAF">SEE ALSO</A><DD>
|
|
</DL>
|
|
<HR>
|
|
This document was created by
|
|
<A HREF="/cgi-bin/man/man2html">man2html</A>,
|
|
using the manual pages.<BR>
|
|
Time: 00:05:42 GMT, March 31, 2021
|
|
</BODY>
|
|
</HTML>
|