go-ffi

Go bindings to libffi

Calling C Functions

go-ffi is interesting when a program needs to call C functions in a way that is not yet supported by cgo. For example if the function pointer was obtained dynamically or if the function as a variadic signature.

Here's an example showing how to call printf from Go using the go-ffi package:

package main

// #include <stdio.h>
//
// const void *printf__ = (void *) printf;
import "C"
import "github.com/achille-roussel/go-ffi"

func main() {
     ffi.Call(C.printf__, nil, "%s %s!\n", "Hello", "World")
}

Hello World!

Calling Go Functions

go-ffi also provides a mechanism for generating pointers that can be used to call Go functions from compiled C code.
Here's an example showing how this is done:

package main

import (
       "fmt"
       "strconv"
       "unsafe"

       "github.com/achille-roussel/go-ffi"
)

func main() {
     itoa := ffi.Closure(strconv.Itoa)
     fptr := itoa.Pointer()
     repr := ""

     ffi.Call(unsafe.Pointer(fptr), &repr, 42)

     fmt.Println(repr)
}

42

Type Conversions

go-ffi automatically converts between C and Go types when using the high-level interfaces.
The following table exposes what conversions are supported:

Go	C
int	int
int8	int8_t
int16	int16_t
int32	int32_t
int64	int64_t
uint	unsigned int
uint8	uint8_t
uint16	uint16_t
uint32	uint32_t
uintptr	size_t
float32	float
float64	double
string	char *
unsafe.Pointer	void *