Call a function in a shared library: Difference between revisions
Call a function in a shared library (view source)
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[[Category:Functions and subroutines]]
{{task|Programming environment operations}}
Show how to call a function in a shared library (without dynamically linking to it at compile-time). In particular, show how to call the shared library function if the library is available, otherwise use an internal equivalent function.
This is a special case of [[Call foreign language function|calling a foreign language function]] where the focus is close to the [https://en.wikipedia.org/wiki/Application_binary_interface ABI] level and not at the normal API level.
;Related task:
* [[OpenGL]] -- OpenGL is usually maintained as a shared library.
<br><br>
=={{header|Ada}}==
===Windows===
The following solution calls ''MessageBox'' from [[Windows]]' dynamic library ''user32.dll''. It does not use Win32 bindings, which would be meaningless, because ''MessageBox'' is already there. Instead of that it links statically to ''kernel32.dll'', which required to load anything under [[Windows]]. From there it uses ''LoadLibrary'' to load ''user32.dll'' and then ''GetProcAddress'' to get the ''MessageBox'' entry point there. Note how [[Windows]] mangles names of functions in the import libraries. So "LoadLibrary" becomes "_LoadLibraryA@4", which is its real name. "A" means ASCII. Once address of ''MessageBox'' is obtained it is converted to a pointer to a function that has an interface corresponding to it. Note [[Windows]]' call convention, which is '''stdcall'''.
<
with Interfaces; use Interfaces;
with Interfaces.C; use Interfaces.C;
Line 22 ⟶ 24:
-- There are ready to use Win32 bindings. We don't want to use them here.
--
type HANDLE is new Unsigned_32; -- on x64 system, replace by Unsigned_64 to make it work
function LoadLibrary (lpFileName : char_array) return HANDLE;
pragma Import (stdcall, LoadLibrary, "LoadLibrary", "_LoadLibraryA"); -- Ada95 does not have the @n suffix.
Line 54 ⟶ 56:
Put_Line ("Unable to load the library " & HANDLE'Image (Library));
end if;
end Shared_Library_Call;</
===Linux===
Here we are using the ''dl'' library statically (-ldl switch upon linking) and ''Xlib'' dynamically (''libX11.so''). The function ''dlopen'' loads a library. The function ''dlsym'' looks up for an entry point there. From ''libX11.so'', first ''XOpenDisplay'' is called to open an X11 display, which name is in the DISPLAY environment variable. Then XDisplayWidth of the display is obtained an printed into the standard output.
<
with Ada.Text_IO; use Ada.Text_IO;
with Interfaces; use Interfaces;
Line 106 ⟶ 108:
Put_Line ("Unable to load the library");
end if;
end Shared_Library_Call;</
=={{header|Arturo}}==
<syntaxhighlight lang="rebol">getCurlVersion: function [][
try? [
call.external:'curl "curl_version" .expect: :string []
]
else [
"library not found"
]
]
print ["curl version:" getCurlVersion]</syntaxhighlight>
{{out}}
<pre>curl version: libcurl/7.64.1 SecureTransport (LibreSSL/2.8.3) zlib/1.2.11 nghttp2/1.41.0 </pre>
=={{header|AutoHotkey}}==
{{works with|http://www.autohotkey.net/~tinku99/ahkdll/ AutoHotkey.dll}}<br>
dllhost.ahk
<
clientHandle := DllCall("AutoHotkey\ahkdll", "str", "dllclient.ahk", "str"
, "", "str", "parameter1 parameter2", "Cdecl Int")</
dllclient.ahk
<syntaxhighlight lang
=={{header|BASIC}}==
==={{header|BaCon}}===
<syntaxhighlight lang="qbasic">' Call a dynamic library function
PROTO j0
bessel0 = j0(1.0)
PRINT bessel0
</syntaxhighlight>
{{out}}
<pre>prompt$ bacon calllib.bac
Converting 'calllib.bac'... done, 4 lines were processed in 0.004 seconds.
Compiling 'calllib.bac'... cc -c calllib.bac.c
cc -o calllib calllib.bac.o -lbacon -lm
Done, program 'calllib' ready.
prompt$ ./calllib
0.765198</pre>
==={{header|BBC BASIC}}===
{{works with|BBC BASIC for Windows}}
The following shared libraries are automatically available: ADVAPI32.DLL, COMCTL32.DLL, COMDLG32.DLL, GDI32.DLL, KERNEL32.DLL, SHELL32.DLL, USER32.DLL and WINMM.DLL.
<
</syntaxhighlight>
=={{header|C}}==
Line 128 ⟶ 162:
'''Tested with''' gcc on a GNU/Linux system (on GNU/Linux <code>dl*</code> functions are available linking to <tt>libdl</tt>, i.e. with <tt>-ldl</tt> option)
<
#include <stdlib.h>
#include <dlfcn.h>
Line 163 ⟶ 197:
if (imglib != NULL ) dlclose(imglib);
return EXIT_SUCCESS;
}</
The fake <tt>fakeimglib.so</tt> code is
<
/* gcc -shared -nostartfiles fakeimglib.c -o fakeimglib.so */
int openimage(const char *s)
Line 174 ⟶ 208:
fprintf(stderr, "opening %s\n", s);
return handle++;
}</
When the library <tt>fakeimglib.so</tt> exists in the current directory (this choice is senseful only for testing purposes), the output is:
Line 185 ⟶ 219:
<pre>internal openimage opens fake.img...
opened with handle 0</pre>
=={{header|C sharp|C#}}==
In Windows.
<
class Program {
Line 197 ⟶ 230:
int r = fakefunction(10);
}
}</
=={{header|COBOL}}==
Tested with GnuCOBOL, GNU/Linux.
<
program-id. callsym.
Line 238 ⟶ 270:
goback.
end program callsym.</
{{out}}
<pre>prompt$ cobc -xj callsym.cob
Success</pre>
=={{header|Common Lisp}}==
{{libheader|CFFI}}
<
#<CFFI::FOREIGN-LIBRARY {1004F4ECC1}>
CL-USER> (cffi:foreign-funcall "XOpenDisplay"
Line 254 ⟶ 285:
#-sbcl ":0.0"
:pointer)
#.(SB-SYS:INT-SAP #X00650FD0)</
=={{header|Crystal}}==
<syntaxhighlight lang="ruby">libm = LibC.dlopen("libm.so.6", LibC::RTLD_LAZY)
sqrtptr = LibC.dlsym(libm, "sqrt") unless libm.null?
if sqrtptr
sqrtproc = Proc(Float64, Float64).new sqrtptr, Pointer(Void).null
at_exit { LibC.dlclose(libm) }
else
sqrtproc = ->Math.sqrt(Float64)
end
puts "the sqrt of 4 is #{sqrtproc.call(4.0)}"</syntaxhighlight>
=={{header|D}}==
<
import std.stdio, std.c.windows.windows;
Line 265 ⟶ 308:
void main() {
writeln(GetDoubleClickTime());
}</
<pre>500</pre>
=={{header|Dart}}==
add.c
<syntaxhighlight lang="c">
int add(int num1, int num2) {
return num1 + num2;
}
</syntaxhighlight>
Dart code
<syntaxhighlight lang="javascript">import 'dart:ffi'
show DynamicLibrary, NativeFunction, Int32;
main(){
final lib = DynamicLibrary.open('add.dylib'); // Load library
final int Function(int num1,int num2) add = lib // Write Dart function binding
.lookup<NativeFunction<Int32 Function( Int32, Int32 )>>('add') // Lookup function in library
.asFunction(); // convert to Dart Function
print( add( 1, 2 ) );
}
</syntaxhighlight>
=={{header|Delphi}}==
Line 274 ⟶ 339:
Loads library on startup.
<
Line 280 ⟶ 345:
Loads library on first call to DoSomething.
<
Line 286 ⟶ 351:
Loads and unloads library on demand.
<syntaxhighlight lang="delphi">var
lLibraryHandle: THandle;
lDoSomething: procedure; stdcall;
Line 297 ⟶ 362:
FreeLibrary(lLibraryHandle);
end;
end;</
=={{header|Ecstasy}}==
Ecstasy was designed around software containers and a strong security model. As such, Ecstasy does not have an FFI, and Ecstasy code cannot direcly access operating system or other foreign functions. More specifically, code running within an Ecstasy container cannot call foreign functions; any such required capabilities must be implemented outside of Ecstasy (for example, in C) and then <i>injected</i> into an Ecstasy container.
=={{header|Forth}}==
===GNU Forth 0.7.9 on Linux===
Call tgamma() from limbm.so
<syntaxhighlight lang="forth">
c-library math
s" m" add-lib
\c #include <math.h>
c-function gamma tgamma r -- r
end-c-library
</syntaxhighlight>
{{Out}}
<pre>
require ./foreign.fs ok
1.01e2 gamma fs. 9.33262154439442E157 ok
</pre>
=={{header|Fortran}}==
===GNU Fortran on Linux===
Line 306 ⟶ 391:
A simple "C" function add_n in add_n.c
<syntaxhighlight lang="c">
double add_n(double* a, double* b)
{
return *a + *b;
}
</
compile it
Line 320 ⟶ 405:
File add_nf.f90
<
function add_nf(a,b) bind(c, name='add_nf')
use, intrinsic :: iso_c_binding
Line 329 ⟶ 414:
add_nf = a + b
end function add_nf
</
Compile it
Line 342 ⟶ 427:
File shared_lib_new_test.f90
<
!-----------------------------------------------------------------------
!module dll_module
Line 618 ⟶ 703:
end program test_load_dll
</syntaxhighlight>
Compile test program
Line 640 ⟶ 725:
===Intel Fortran on Windows===
First, the DLL. Compile with '''ifort /dll dllfun.f90'''. The function is compiled with the STDCALL calling convention: it's not necessary here but it shows how to do it.
<
implicit none
!DEC$ ATTRIBUTES DLLEXPORT, STDCALL, REFERENCE :: FFUN
double precision :: x, y, ffun
ffun = x + y * y
end function</
Now, the main program. It will wait for two
<
use kernel32
use iso_c_binding
Line 665 ⟶ 750:
integer(c_intptr_t) :: ptr
integer(handle) :: h
double precision :: x, y
Line 680 ⟶ 763:
if (FreeLibrary(h) == 0) error stop "Error: FreeLibrary"
end program</
=== GNU Fortran on Windows ===
The program for Intel Fortran can easily be adapted to the GNU Fortran compiler. A kernel32 module must be provided (here a small version with only the three necessary functions is given). Also, the STDCALL declaration is different. The '''dllfun.dll''' library must be in the PATH, but also MinGW libraries.
To compile:
<pre>gfortran -Wall -c kernel32.f90
gfortran -Wall -shared dllfun.f90 -o dllfun.dll
gfortran -Wall dynload.f90 -lkernel32</pre>
With the standard conformance option '''-std=f2008''', GNU Fortran will complain about the ''c_f_procpointer'' call in the main program. Use '''-std=f2008ts''' instead.
First the DLL:
<syntaxhighlight lang="fortran">function ffun(x, y)
implicit none
!GCC$ ATTRIBUTES DLLEXPORT, STDCALL :: FFUN
double precision :: x, y, ffun
ffun = x + y * y
end function</syntaxhighlight>
Main program:
<syntaxhighlight lang="fortran">program dynload
use kernel32
use iso_c_binding
implicit none
abstract interface
function ffun_int(x, y)
!GCC$ ATTRIBUTES DLLEXPORT, STDCALL :: FFUN
double precision :: ffun_int, x, y
end function
end interface
procedure(ffun_int), pointer :: ffun_ptr
integer(c_intptr_t) :: ptr
integer(handle) :: h
double precision :: x, y
h = LoadLibrary("dllfun.dll" // c_null_char)
if (h == 0) error stop "Error: LoadLibrary"
ptr = GetProcAddress(h, "ffun_@8" // c_null_char)
if (ptr == 0) error stop "Error: GetProcAddress"
call c_f_procpointer(transfer(ptr, c_null_funptr), ffun_ptr)
read *, x, y
print *, ffun_ptr(x, y)
if (FreeLibrary(h) == 0) error stop "Error: FreeLibrary"
end program</syntaxhighlight>
Interface module:
<syntaxhighlight lang="fortran">module kernel32
use iso_c_binding
implicit none
integer, parameter :: HANDLE = C_INTPTR_T
integer, parameter :: PVOID = C_INTPTR_T
integer, parameter :: BOOL = C_INT
interface
function LoadLibrary(lpFileName) bind(C, name="LoadLibraryA")
import C_CHAR, HANDLE
!GCC$ ATTRIBUTES STDCALL :: LoadLibrary
integer(HANDLE) :: LoadLibrary
character(C_CHAR) :: lpFileName
end function
end interface
interface
function FreeLibrary(hModule) bind(C, name="FreeLibrary")
import HANDLE, BOOL
!GCC$ ATTRIBUTES STDCALL :: FreeLibrary
integer(BOOL) :: FreeLibrary
integer(HANDLE), value :: hModule
end function
end interface
interface
function GetProcAddress(hModule, lpProcName) bind(C, name="GetProcAddress")
import C_CHAR, PVOID, HANDLE
!GCC$ ATTRIBUTES STDCALL :: GetProcAddress
integer(PVOID) :: GetProcAddress
integer(HANDLE), value :: hModule
character(C_CHAR) :: lpProcName
end function
end interface
end module</syntaxhighlight>
=={{header|FreeBASIC}}==
<
' Attempt to call Beep function in Win32 API
Line 705 ⟶ 875:
Print
Print "Press any key to quit"
Sleep</
=={{header|FutureBasic}}==
Use GameplayKit framework to quickly generate random integers.
<syntaxhighlight lang="futurebasic">
include "tlbx GameplayKit.incl"
UInt64 randomInteger
NSUInteger i
for i = 1 to 20
randomInteger = fn GKLinearCongruentialRandomSourceSeed( fn GKLinearCongruentialRandomSourceInit )
print randomInteger
next
HandleEvents
</syntaxhighlight>
=={{header|Go}}==
{{trans|C}}
{{works with|Ubuntu 18.04}}
<br>
Dynamically calling a function from a shared library can only be accomplished in Go using 'cgo' and, even then, the function pointer returned by 'dlsym' can only be called via a C bridging function as calling C function pointers directly from Go is not currently supported.
This is the C code to produce fakeimglib.so:
<syntaxhighlight lang="c">#include <stdio.h>
/* gcc -shared -fPIC -nostartfiles fakeimglib.c -o fakeimglib.so */
int openimage(const char *s)
{
static int handle = 100;
fprintf(stderr, "opening %s\n", s);
return handle++;
}</syntaxhighlight>
And this is the Go code to dynamically load the .so file and call the 'openimage' function - or if the .so file (or the function itself) is not available, to call the internal version of the function:
<syntaxhighlight lang="go">package main
/*
#cgo LDFLAGS: -ldl
#include <stdlib.h>
#include <dlfcn.h>
typedef int (*someFunc) (const char *s);
int bridge_someFunc(someFunc f, const char *s) {
return f(s);
}
*/
import "C"
import (
"fmt"
"os"
"unsafe"
)
var handle = -1
func myOpenImage(s string) int {
fmt.Fprintf(os.Stderr, "internal openImage opens %s...\n", s)
handle++
return handle
}
func main() {
libpath := C.CString("./fakeimglib.so")
defer C.free(unsafe.Pointer(libpath))
imglib := C.dlopen(libpath, C.RTLD_LAZY)
var imghandle int
if imglib != nil {
openimage := C.CString("openimage")
defer C.free(unsafe.Pointer(openimage))
fp := C.dlsym(imglib, openimage)
if fp != nil {
fi := C.CString("fake.img")
defer C.free(unsafe.Pointer(fi))
imghandle = int(C.bridge_someFunc(C.someFunc(fp), fi))
} else {
imghandle = myOpenImage("fake.img")
}
C.dlclose(imglib)
} else {
imghandle = myOpenImage("fake.img")
}
fmt.Printf("opened with handle %d\n", imghandle)
}</syntaxhighlight>
{{output}}
<pre>
Same as C entry.
</pre>
=={{header|Haskell}}==
{{Works with|GHC|7.10.3}}
{{libheader|unix}}
<syntaxhighlight lang="haskell">#!/usr/bin/env stack
-- stack --resolver lts-6.33 --install-ghc runghc --package unix
import Control.Exception ( try )
import Foreign ( FunPtr, allocaBytes )
import Foreign.C
( CSize(..), CString, withCAStringLen, peekCAStringLen )
import System.Info ( os )
import System.IO.Error ( ioeGetErrorString )
import System.IO.Unsafe ( unsafePerformIO )
import System.Posix.DynamicLinker
( RTLDFlags(RTLD_LAZY), dlsym, dlopen )
dlSuffix :: String
dlSuffix = if os == "darwin" then ".dylib" else ".so"
type RevFun = CString -> CString -> CSize -> IO ()
foreign import ccall "dynamic"
mkFun :: FunPtr RevFun -> RevFun
callRevFun :: RevFun -> String -> String
callRevFun f s = unsafePerformIO $ withCAStringLen s $ \(cs, len) -> do
allocaBytes len $ \buf -> do
f buf cs (fromIntegral len)
peekCAStringLen (buf, len)
getReverse :: IO (String -> String)
getReverse = do
lib <- dlopen ("libcrypto" ++ dlSuffix) [RTLD_LAZY]
fun <- dlsym lib "BUF_reverse"
return $ callRevFun $ mkFun fun
main = do
x <- try getReverse
let (msg, rev) =
case x of
Left e -> (ioeGetErrorString e ++ "; using fallback", reverse)
Right f -> ("Using BUF_reverse from OpenSSL", f)
putStrLn msg
putStrLn $ rev "a man a plan a canal panama"</syntaxhighlight>
=={{header|J}}==
Most of this was borrowed from [[Call a foreign-language function#J]]
<
strdup=: 'msvcrt.dll _strdup >x *' cd <
free=: 'msvcrt.dll free n x' cd <
Line 720 ⟶ 1,027:
y
end.
)</
You get a domain error when the required library is not present at run time. A try/catch will let you handle this (as would the <code>::</code> adverse operator).
Example use:
<
hello
getstr@strdup ::] 'hello'
hello</
=={{header|Java}}==
If you have Unix [[make]], then edit the ''Makefile'', run <code>make</code>, run <code>java -Djava.library.path=. RSort</code>. If you don't set java.library.path, or don't build the library, then the Java code falls back from using C to using Java. For more info about building a JNI library, see [[Call a foreign-language function#Java]].
<syntaxhighlight lang="java">/* TrySort.java */
import java.util.Collections;
import java.util.Random;
public class TrySort {
static boolean useC;
static {
try {
System.loadLibrary("TrySort");
useC = true;
} catch(UnsatisfiedLinkError e) {
useC = false;
}
}
static native void sortInC(int[] ary);
static class IntList extends java.util.AbstractList<Integer> {
int[] ary;
IntList(int[] ary) { this.ary = ary; }
public Integer get(int i) { return ary[i]; }
public Integer set(int i, Integer j) {
Integer o = ary[i]; ary[i] = j; return o;
}
public int size() { return ary.length; }
}
static class ReverseAbsCmp
implements java.util.Comparator<Integer>
{
public int compare(Integer pa, Integer pb) {
/* Order from highest to lowest absolute value. */
int a = pa > 0 ? -pa : pa;
int b = pb > 0 ? -pb : pb;
return a < b ? -1 : a > b ? 1 : 0;
}
}
static void sortInJava(int[] ary) {
Collections.sort(new IntList(ary), new ReverseAbsCmp());
}
public static void main(String[] args) {
/* Create an array of random integers. */
int[] ary = new int[1000000];
Random rng = new Random();
for (int i = 0; i < ary.length; i++)
ary[i] = rng.nextInt();
/* Do the reverse sort. */
if (useC) {
System.out.print("Sorting in C... ");
sortInC(ary);
} else {
System.out.print
("Missing library for C! Sorting in Java... ");
sortInJava(ary);
}
for (int i = 0; i < ary.length - 1; i++) {
int a = ary[i];
int b = ary[i + 1];
if ((a > 0 ? -a : a) > (b > 0 ? -b : b)) {
System.out.println("*BUG IN SORT*");
System.exit(1);
}
}
System.out.println("ok");
}
}</syntaxhighlight>
<syntaxhighlight lang="c">/* TrySort.c */
#include <stdlib.h>
#include "TrySort.h"
static void fail(JNIEnv *jenv, const char *error_name) {
jclass error_class = (*jenv)->FindClass(jenv, error_name);
(*jenv)->ThrowNew(jenv, error_class, NULL);
}
static int reverse_abs_cmp(const void *pa, const void *pb) {
jint a = *(jint *)pa;
jint b = *(jint *)pb;
a = a > 0 ? -a : a;
b = b > 0 ? -b : b;
return a < b ? -1 : a > b ? 1 : 0;
}
void Java_TrySort_sortInC(JNIEnv *jenv, jclass obj, jintArray ary) {
jint *elem, length;
if (ary == NULL) {
fail(jenv, "java/lang/NullPointerException");
return;
}
length = (*jenv)->GetArrayLength(jenv, ary);
elem = (*jenv)->GetPrimitiveArrayCritical(jenv, ary, NULL);
if (elem == NULL) {
fail(jenv, "java/lang/OutOfMemoryError");
return;
}
qsort(elem, length, sizeof(jint), reverse_abs_cmp);
(*jenv)->ReleasePrimitiveArrayCritical(jenv, ary, elem, 0);
}</syntaxhighlight>
<syntaxhighlight lang="make"># Makefile
# Edit the next lines to match your JDK.
JAVA_HOME = /usr/local/jdk-1.8.0
CPPFLAGS = -I$(JAVA_HOME)/include -I$(JAVA_HOME)/include/openbsd
JAVAC = $(JAVA_HOME)/bin/javac
JAVAH = $(JAVA_HOME)/bin/javah
CC = cc
LDFLAGS = -shared -fPIC
LIB = libTrySort.so
all: TrySort.class $(LIB)
$(LIB): TrySort.c TrySort.h
$(CC) $(CPPFLAGS) $(LDFLAGS) -o $@ TrySort.c
.SUFFIXES: .class .java .h
.class.h:
rm -f $@
$(JAVAH) -jni -o $@ $(<:.class=)
.java.class:
$(JAVAC) $<
clean:
rm -f TrySort.class TrySort?IntList.class \
TrySort?ReverseAbsCmp.class TrySort.h $(LIB)</syntaxhighlight>
===JNA===
{{libheader|JNA}}
<
import com.sun.jna.Native;
Line 755 ⟶ 1,192:
lib.sharedLibraryFunction();
}
}</
=={{header|Jsish}}==
Jsish includes a '''load('library.so');''' function, which calls a specially crafted management function in the library,
'''JsiInitmoduleName''', where the moduleName part of the exported symbol is the name of the library loaded.
Normally, this function would register commands to the shell, but this is just a DISPLAY statement on load, and then again on unload as jsish runs down. Note the name used, "Jsi_Initbyjsi", from "byjsi.so".
<syntaxhighlight lang="javascript">#!/usr/local/bin/jsish
load('byjsi.so');</syntaxhighlight>
For example, a COBOL library generated from
<syntaxhighlight lang="cobol"> identification division.
program-id. sample as "Jsi_Initbyjsi".
environment division.
configuration section.
special-names.
call-convention 0 is extern.
repository.
function all intrinsic.
data division.
linkage section.
01 jsi-interp usage pointer.
01 rel usage binary-long.
procedure division using by value jsi-interp rel.
sample-main.
if rel equal zero then
display "GnuCOBOL from jsish load of " module-source()
" and cobc -m -fimplicit-init" upon syserr
goback
end-if
display "Called again with: " jsi-interp ", " rel upon syserr
goback.
end program sample.</syntaxhighlight>
{{out}}
<pre>prompt$ cobc -m -debug -fimplicit-init byjsi.cob
prompt$ ./callcob.jsi
GnuCOBOL from jsish load of byjsi.cob and cobc -m -fimplicit-init
Called again with: 0x00000000013a9260, +0000000002
prompt$</pre>
=={{header|Julia}}==
Julia has the `ccall` function which follows the form: ccall((symbol, library), RetType, (ArgType1, ...), ArgVar1, ...)
<
#this example works on Windows
ccall( (:GetDoubleClickTime, "User32"), stdcall,
Uint, (), )
ccall( (:clock, "libc"), Int32, ())</
For more information, see here [http://docs.julialang.org/en/latest/manual/calling-c-and-fortran-code.html]
=={{header|Kotlin}}==
{{trans|C}}
{{Works with|Ubuntu 14.04}}
This is the C code to produce fakeimglib.so:
<syntaxhighlight lang="c">#include <stdio.h>
/* gcc -shared -fPIC -nostartfiles fakeimglib.c -o fakeimglib.so */
int openimage(const char *s)
{
static int handle = 100;
fprintf(stderr, "opening %s\n", s);
return handle++;
}</syntaxhighlight>
And this is the Kotlin code to dynamically load the .so file and call the 'openimage' function - or if the .so file (or the function itself) is not available, to call the internal version of the function:
<syntaxhighlight lang="scala">// Kotlin Native version 0.5
import kotlinx.cinterop.*
import platform.posix.*
import platform.linux.*
typealias Func = (String)-> Int
var handle = 0
fun myOpenImage(s: String): Int {
fprintf(stderr, "internal openImage opens %s...\n", s)
return handle++
}
fun main(args: Array<String>) {
var imgHandle: Int
val imglib = dlopen("./fakeimglib.so", RTLD_LAZY)
if (imglib != null) {
val fp = dlsym(imglib, "openimage")
if (fp != null) {
val extOpenImage: CPointer<CFunction<Func>> = fp.reinterpret()
imgHandle = extOpenImage("fake.img")
}
else {
imgHandle = myOpenImage("fake.img")
}
dlclose(imglib)
}
else {
imgHandle = myOpenImage("fake.img")
}
println("opened with handle $imgHandle")
}</syntaxhighlight>
{{out}}
<pre>
Same as C entry
</pre>
=={{header|Lingo}}==
<
str = "The quick brown fox jumps over the lazy dog"
Line 785 ⟶ 1,317:
crc = crcObj.crc32(str)
end if</
=={{header|Lua}}==
There is no built-in mechanism, but several external library options exist. Here, the alien library is used to display a message box via the Win32 API.
<syntaxhighlight lang="lua">alien = require("alien")
msgbox = alien.User32.MessageBoxA
msgbox:types({ ret='long', abi='stdcall', 'long', 'string', 'string', 'long' })
retval = msgbox(0, 'Please press Yes, No or Cancel', 'The Title', 3)
print(retval) --> 6, 7 or 2</syntaxhighlight>
=={{header|Maple}}==
<
> cfloor( 2.3 );
2.</
=={{header|Lambdatalk}}==
Lambdatalk works in a wiki, lambdatank, hosted by any web browser coming with Javascript. Javascript has no native tools dealing with big numbers. Jonas Raoni Soares Silva has built a smart JS library, http://jsfromhell.com/classes/bignumber, which can be loaded in a wiki page, so called "lib_BN". Obviously interfaces must be built, for instance the BN.* operator multiplying two big numbers:.
<syntaxhighlight lang="scheme">
{script
LAMBDATALK.DICT['BN.*'] = function(){
var args = arguments[0].split(' '),
a = new BigNumber( args[0], BN_DEC ),
b = new BigNumber( args[1], BN_DEC );
return a.multiply( b )
};
</syntaxhighlight>
The lib_BN library can be loaded in any other wiki page via a {require lib_BN} expression and the BN.* primitive can be used this way:
<syntaxhighlight lang="scheme">
{BN.* 123456789123456789123456789 123456789123456789123456789}
-> 15241578780673678546105778281054720515622620750190521
to be compared with the "standard" lambdatalk builtin * operator
{* 123456789123456789123456789 123456789123456789123456789}
-> 1.524157878067368e+52
</syntaxhighlight>
=={{header|Mathematica}}/{{header|Wolfram Language}}==
This works on windows and on linux/mac too (through Mono)
<
externalFloor = DefineDLLFunction["floor", "msvcrt.dll", "double", { "double" }];
externalFloor[4.2]
-> 4.</
=={{header|Nim}}==
===Interacting with C code===
<
echo openimage("foo")
echo openimage("bar")
echo openimage("baz")</
The fake <code>fakeimglib.so</code> code is
<
/* gcc -shared -nostartfiles fakeimglib.c -o fakeimglib.so */
int openimage(const char *s)
Line 816 ⟶ 1,377:
fprintf(stderr, "opening %s\n", s);
return handle++;
}</
Output:
<pre>opening foo
Line 826 ⟶ 1,387:
===Interacting with Nim code===
<
echo openimage("foo")
echo openimage("bar")
echo openimage("baz")</
The fake <code>libfakeimg.so</code> code is
<
var handle = 100
Line 838 ⟶ 1,399:
stderr.writeln "opening ", s
result = handle
inc(handle)</
Output:
<pre>opening foo
Line 846 ⟶ 1,407:
opening baz
102</pre>
=={{header|OCaml}}==
As far as I know there is no solution in OCaml standard library to load a function from a C library dynamically. So I have quickly implemented [[Call a function in a shared library/OCaml|a module named Dlffi that you can find in this sub-page]]. It is basically a wrapper around the GNU/Linux dl* functions and the libffi.
Line 853 ⟶ 1,413:
Here is an example of use of this [[Call a function in a shared library/OCaml|Dlffi module]]:
<
let get_int = function Int v -> v | _ -> failwith "get_int"
Line 883 ⟶ 1,443:
Printf.printf "# Screen dimensions are: %d x %d pixels\n" width height;
dlclose xlib;
;;</
=={{header|Ol}}==
Simplest case. Will produce memory leak, because no C "free" function called for dupped string. Useful when no "free" function call required.
<syntaxhighlight lang="scheme">
(import (otus ffi))
(define self (load-dynamic-library #f))
(define strdup
(self type-string "strdup" type-string))
(print (strdup "Hello World!"))
</syntaxhighlight>
A bit complex case. No memory leaks, because "free" function called for dupped string.
<syntaxhighlight lang="scheme">
(import (otus ffi))
(define self (load-dynamic-library #f))
(define strdup
(let ((strdup (self type-vptr "strdup" type-string))
(free (self fft-void "free" type-vptr)))
(lambda (str)
(let*((dupped (strdup str))
(result (vptr->string dupped)))
(free dupped)
result))))
(print (strdup "Hello World!"))
</syntaxhighlight>
{{Out}}
<pre>
Hello World!
</pre>
=={{header|OxygenBasic}}==
<
'Loading a shared library at run time and calling a function.
Line 900 ⟶ 1,493:
FreeLibrary user32
</syntaxhighlight>
=={{header|PARI/GP}}==
<
where "G" is the parser code; see section 5.7.3 in the [http://pari.math.u-bordeaux.fr/pub/pari/manuals/2.4.4/libpari.pdf User's Guide to the PARI library] for more information.
=={{header|Pascal}}==
See [[Call_a_function_in_a_shared_library#Delphi | Delphi]]
=={{header|Perl
Examples for simple <code>C</code> library calls, but each module is capable of much more (and can work with other languages). Refer to their documentation for details.
===Inline===
This modules auto-builds a wrapper to the library on the first call, and subsequently uses that interface with no delay.
<syntaxhighlight lang="perl">use Inline
C => "DATA",
ENABLE => "AUTOWRAP",
LIBS => "-lm";
print 4*atan(1) . "\n";
__DATA__
__C__
double atan(double x);</syntaxhighlight>
{{out}}
<pre>
===FFI===
This module is smart about finding libraries, here getting <code>atan</code> (from 'lm') and <code>puts</code> (from 'libc').
<syntaxhighlight lang="perl">use FFI::Platypus;
my $ffi = FFI::Platypus->new;
$ffi->lib(undef);
$ffi->attach(puts => ['string'] => 'int');
$ffi->attach(atan => ['double'] => 'double');
puts(4*atan(1));</syntaxhighlight>
{{out}}
<pre>3.14159265358979</pre>
=={{header|Phix}}==
<!--<syntaxhighlight lang="phix">(notonline)-->
<span style="color: #008080;">without</span> <span style="color: #008080;">js</span> <span style="color: #000080;font-style:italic;">-- not from a browser, mate!</span>
<span style="color: #004080;">string</span> <span style="color: #0000FF;">{</span><span style="color: #000000;">libname</span><span style="color: #0000FF;">,</span><span style="color: #000000;">funcname</span><span style="color: #0000FF;">}</span> <span style="color: #0000FF;">=</span> <span style="color: #008080;">iff</span><span style="color: #0000FF;">(</span><span style="color: #7060A8;">platform</span><span style="color: #0000FF;">()=</span><span style="color: #004600;">WINDOWS</span><span style="color: #0000FF;">?{</span><span style="color: #008000;">"user32"</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"CharLowerA"</span><span style="color: #0000FF;">}:{</span><span style="color: #008000;">"libc"</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"tolower"</span><span style="color: #0000FF;">})</span>
<span style="color: #004080;">atom</span> <span style="color: #000000;">lib</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">open_dll</span><span style="color: #0000FF;">(</span><span style="color: #000000;">libname</span><span style="color: #0000FF;">)</span>
<span style="color: #004080;">integer</span> <span style="color: #000000;">func</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">define_c_func</span><span style="color: #0000FF;">(</span><span style="color: #000000;">lib</span><span style="color: #0000FF;">,</span><span style="color: #000000;">funcname</span><span style="color: #0000FF;">,{</span><span style="color: #000000;">C_INT</span><span style="color: #0000FF;">},</span><span style="color: #000000;">C_INT</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">func</span><span style="color: #0000FF;">=-</span><span style="color: #000000;">1</span> <span style="color: #008080;">then</span>
<span style="color: #0000FF;">?{{</span><span style="color: #7060A8;">lower</span><span style="color: #0000FF;">(</span><span style="color: #008000;">'A'</span><span style="color: #0000FF;">)}}</span> <span style="color: #000080;font-style:italic;">-- (you don't //have// to crash!)</span>
<span style="color: #008080;">else</span>
<span style="color: #0000FF;">?</span><span style="color: #7060A8;">c_func</span><span style="color: #0000FF;">(</span><span style="color: #000000;">func</span><span style="color: #0000FF;">,{</span><span style="color: #008000;">'A'</span><span style="color: #0000FF;">})</span> <span style="color: #000080;font-style:italic;">-- ('A'==65)</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<!--</syntaxhighlight>-->
{{out}}
<pre>
97 -- (or {{97}} if func not found)
</pre>
=={{header|PicoLisp}}==
This differs between the 32-bit and 64-bit versions. While the 64-bit version
Line 934 ⟶ 1,548:
===32-bit version===
For the 32-bit version, we need some glue code:
<
(gcc "x11" '("-lX11") 'xOpenDisplay 'xCloseDisplay)
Line 959 ⟶ 1,573:
-> 158094320
: (xCloseDisplay Display)
-> 0</
===64-bit version===
In the 64-bit version, we can call the library directly:
<
-> 6502688
: (native "/usr/lib/libX11.so.6" "XCloseDisplay" 'I Display)
-> 0</
=={{header|PowerBASIC}}==
{{Works with|PowerBASIC for Windows}}
In this example, if the library can't be found (user32), or the desired function in the library (MessageBoxA), the equivalent built-in function (MSGBOX) is at the "epicFail" label... but really, if you can't find user32.dll, you've got bigger things to worry about.
<
FUNCTION PBMAIN () AS LONG
Line 1,006 ⟶ 1,619:
IF ISFALSE(tmp&) THEN MSGBOX "Error freeing library... [shrug]"
END IF
END FUNCTION</
=={{header|PureBasic}}==
Older PureBasic versions normally relied on CallFunction() and CallFunctionFast()
<
*MessageBox = GetFunction(0, "MessageBoxA")
CallFunctionFast(*MessageBox, 0, "Body", "Title", 0)
CloseLibrary(0)
endif</
Since versions 4 the recommended way is via the usage of Prototypes even if the old system still is supported.
<
If OpenLibrary(0, "User32.dll")
Line 1,022 ⟶ 1,634:
MsgBox(0, "Hello", "World")
CloseLibrary(0)
EndIf</
=={{header|Python}}==
=== ctypes ===
Example that call User32.dll::GetDoubleClickTime() in windows.
<
user32_dll = ctypes.cdll.LoadLibrary('User32.dll')
print user32_dll.GetDoubleClickTime()</syntaxhighlight>
Or, to call printf out of the C standard library:
<syntaxhighlight lang="python">>>> import ctypes
>>> # libc = ctypes.cdll.msvcrt # Windows
>>> # libc = ctypes.CDLL('libc.dylib') # Mac
>>> libc = ctypes.CDLL('libc.so') # Linux and most other *nix
>>> libc.printf(b'hi there, %s\n', b'world')
hi there, world.
17</syntaxhighlight>
=== CFFI ===
[https://cffi.readthedocs.io/ CFFI] isn't built into the stdlib, but, on the other hand, it works with other Python implementations like PyPy. It also has a variety of advantages and disadvantages over ctypes, even for simple cases like this:
<syntaxhighlight lang="python">
>>> from cffi import FFI
>>> ffi = FFI()
>>> ffi.cdef("""
... int printf(const char *format, ...); // copy-pasted from the man page
... """)
>>> C = ffi.dlopen(None) # loads the entire C namespace
>>> arg = ffi.new("char[]", b"world") # equivalent to C code: char arg[] = "world";
>>> C.printf(b"hi there, %s.\n", arg) # call printf
hi there, world.
17</syntaxhighlight>
=={{header|QB64}}==
<syntaxhighlight lang="vb">
Declare Dynamic Library "Kernel32"
Sub SetLastError (ByVal dwErr As Long)
Function GetLastError& ()
End Declare
SetLastError 20
Print GetLastError</syntaxhighlight>
=={{header|R}}==
This is possible in R in only a few limited ways. If the library function one wishes to call is a (C-level) R function (of type SEXP), then one may call
<
.Call("my_lib_fun", arg1, arg2)</
It is also possible to use <code>.C()</code> and <code>.Fortran()</code> to call voids and subroutines respectively; here the return value(s) should be in the argument list (rather than merely modifying state). An example of this might look like
<
The return of the <code>.C()</code> function is an R list.
=={{header|Racket}}==
<
(require ffi/unsafe)
(define libm (ffi-lib "libm")) ; get a handle for the C math library
; look up sqrt in the math library. if we can't find it, return the builtin sqrt
(define extern-sqrt (get-ffi-obj 'sqrt libm (_fun _double -> _double)
(lambda () sqrt)))</
Output: <pre>> (extern-sqrt 42.0)
6.48074069840786</pre>
=={{header|Raku}}==
(formerly Perl 6)
{{works with|Rakudo|2018.11}}
<syntaxhighlight lang="raku" line>use NativeCall;
sub XOpenDisplay(Str $s --> int64) is native('X11') {*}
sub XCloseDisplay(int64 $i --> int32) is native('X11') {*}
if try my $d = XOpenDisplay ":0.0" {
say "ID = $d";
XCloseDisplay($d);
}
else {
say "No X11 library!";
say "Use this window instead --> ⬜";
}</syntaxhighlight>
{{out}}
<pre>ID = 94722089782960</pre>
=={{header|REXX}}==
{{works with|Regina REXX}}
The example is using the standard library that is supplied with Regina REXX that contains a wide range of functions.
A little extra boilerplate code was added to make sure the return codes were OK.
The dropping of functions isn't really necessary for most REXX programs.
<syntaxhighlight lang="rexx">/*REXX program calls a function (sysTextScreenSize) in a shared library (regUtil). */
rca= rxFuncAdd('sysLoadFuncs', "regUtil", 'sysLoadFuncs') /*add a function library. */
if rca\==0 then do /*examine the return code.*/
say 'return code' rca "from rxFuncAdd" /*tell about bad " " */
exit rca /*exit this program with RC. */
end
rcl= sysLoadFuncs() /*we can load the functions. */
if rcl\==0 then do /*examine the return code.*/
say 'return code' rcl "from sysLoadFuncs" /*tell about bad " " */
exit rcl /*exit this program with RC. */
end
/* [↓] call a function. */
$= sysTextScreenSize() /*$ has 2 words: rows cols */
parse var $ rows cols . /*get two numeric words in $.*/
say ' rows=' rows /*show number of screen rows.*/
say ' cols=' cols /* " " " " cols.*/
rcd= SysDropFuncs() /*make functions inaccessible*/
if rcd\==0 then do /*examine the return code.*/
say 'return code' rcd "from sysDropFuncs" /*tell about bad " " */
exit rcd /*exit this program with RC. */
end
exit 0 /*stick a fork in it, we're all done. */</syntaxhighlight>
{{out|output|text= (which happens to reflect the program's author's particular screen size for the "DOS" window):}}
<pre>
rows= 62
cols= 96
</pre>
=={{header|RPL}}==
There is no library concept in RPL. However, in 1990, Jan Christiaan van Winkel proposed to the RPL community a way to get something close.
Assuming the programs frequently needed are stored in a specific directory named <code>MyLib</code> located at root directory, the following program, also located at the root directory, can be invoked by any program to access one of the library features.
{{works with|Halcyon Calc|4.2.7}}
{| class="wikitable"
! RPL code
! Comment
|-
|
≪
PATH ➜ owd
≪ HOME MyLib RCL
1 owd SIZE '''FOR''' i
owd i GET EVAL '''NEXT'''
≫ EVAL
≫ ''''CALL'''' STO
|
'''CALL''' ''( 'Program_name' -- depending on call )''
save the old directory
push the library routine on the stack
now go back to the old directory
step by step
run the library routine
|}
{{in}}
<pre>
97 'PRIM?' CALL
</pre>
{{out}}
<pre>
1: 1
</pre>
=={{header|Ruby}}==
This script uses Fiddle from Ruby's standard library to open <code>fakeimglib.so</code> from the [[#C|C example]].
{{works with|Ruby|2.0+}}
<syntaxhighlight lang="ruby">require 'fiddle/import'
module
extend Fiddle::Importer
begin
dlload './fakeimglib.so'
extern 'int openimage(const char *)'
rescue Fiddle::DLError
# Either fakeimglib or openimage() is missing.
@@handle = -1
def openimage(path)
$stderr.puts "internal openimage opens #{path}\n"
@@handle += 1
end
module_function :openimage
end
end
handle =
puts "opened with handle #{handle}"</syntaxhighlight>
The next script tries to use ImageMagick. First, it tries [https://rmagick.github.io/ rmagick] from RubyGems. If that library is missing, it tries to use [http://wiki.github.com/ffi/ffi ffi] from RubyGems to call C functions in ImageMagick. (FFI is an alternative to Fiddle). If that doesn't work, it falls back to code that only handles PNG images.
{{libheader|ImageMagick}}
{{libheader|RubyGems}}
{{works with|Ruby|1.9+}}
<syntaxhighlight lang="ruby"># This script shows the width x height of some images.
# Example:
# $ ruby imsize.rb dwarf-vs-elf.png swedish-chef.jpg
# dwarf-vs-elf.png: 242x176
# swedish-chef.jpg: 256x256
begin
require 'rmagick'
lib = :rmagick
rescue LoadError
# Missing rmagick. Try ffi.
begin
require 'ffi'
module F
extend FFI::Library
ffi_lib 'MagickWand-6.Q16'
attach_function :DestroyMagickWand, [:pointer], :pointer
attach_function :MagickGetImageHeight, [:pointer], :size_t
attach_function :MagickGetImageWidth, [:pointer], :size_t
attach_function :MagickPingImage, [:pointer, :string], :bool
attach_function :MagickWandGenesis, [], :void
attach_function :NewMagickWand, [], :pointer
end
lib = :ffi
rescue LoadError
# Missing ffi, MagickWand lib, or function in lib.
end
end
case lib
when :rmagick
# Returns [width, height] of an image file.
def size(path)
img = Magick::Image.ping(path).first
[img.columns, img.rows]
end
when :ffi
F.MagickWandGenesis()
def size(path)
wand = F.NewMagickWand()
F.MagickPingImage(wand, path) or fail 'problem reading image'
[F.MagickGetImageWidth(wand), F.MagickGetImageHeight(wand)]
ensure
F.DestroyMagickWand(wand) if wand
end
else
PngSignature = "\x89PNG\r\n\x1A\n".force_encoding('binary')
def size(path)
File.open(path, 'rb') do |file|
# Only works with PNG: https://www.w3.org/TR/PNG/
# Reads [width, height] from IDHR chunk.
# Checks height != nil, but doesn't check CRC of chunk.
sig, width, height = file.read(24).unpack('a8@16NN')
sig == PngSignature and height or fail 'not a PNG image'
[width, height]
end
end
end
# Show the size of each image in ARGV.
status = true
ARGV.empty? and (warn "usage: $0 file..."; exit false)
ARGV.each do |path|
begin
r, c = size(path)
puts "#{path}: #{r}x#{c}"
rescue
status = false
puts "#{path}: #$!"
end
end
exit status</syntaxhighlight>
=={{header|Rust}}==
The standard library does not provide a way to load dynamic libraries. Without using third-party libraries, we must use the FFI to call the relevant C functions directly.
===Unix===
<syntaxhighlight lang="rust">#![allow(unused_unsafe)]
extern crate libc;
use std::io::{self,Write};
use std::{mem,ffi,process};
use libc::{c_double, RTLD_NOW};
// Small macro which wraps turning a string-literal into a c-string.
// This is always safe to call, and the resulting pointer has 'static lifetime
macro_rules! to_cstr {
($s:expr) => {unsafe {ffi::CStr::from_bytes_with_nul_unchecked(concat!($s, "\0").as_bytes()).as_ptr()}}
}
macro_rules! from_cstr {
($p:expr) => {ffi::CStr::from_ptr($p).to_string_lossy().as_ref() }
}
fn main() {
unsafe {
let handle = libc::dlopen(to_cstr!("libm.so.6"), RTLD_NOW);
if handle.is_null() {
writeln!(&mut io::stderr(), "{}", from_cstr!(libc::dlerror())).unwrap();
process::exit(1);
}
let extern_cos = libc::dlsym(handle, to_cstr!("cos"))
.as_ref()
.map(mem::transmute::<_,fn (c_double) -> c_double)
.unwrap_or(builtin_cos);
println!("{}", extern_cos(4.0));
}
}
fn builtin_cos(x: c_double) -> c_double {
x.cos()
}</syntaxhighlight>
=={{header|Scala}}==
===Windows===
====Get free disk space====
{{libheader|net.java.dev.sna.SNA}}
<
import com.sun.jna.ptr.IntByReference
Line 1,133 ⟶ 1,957:
println(f"'$disk%s' ($ok%s): sectors/cluster: ${spc.getValue}%d, bytes/sector: ${bps.getValue}%d, " +
f" free-clusters: ${fc.getValue}%d, total/clusters: ${tc.getValue}%d%n")
}}</
=={{header|Smalltalk}}==
{{works with|GNU Smalltalk}}
The code tries to load the <tt>fakeimglib</tt> (cfr [[Call function in shared library#C|C example]]); if it succeed, the symbol <tt>openimage</tt> will exist, and will be called; otherwise, it is executed an "internal" code for <tt>openimage</tt>. In this example return code of the function of the library is ignored (<tt>ValueHolder null</tt>)
<
Object subclass: ExtLib [
Line 1,151 ⟶ 1,974:
].
ExtLib openimage: 'test.png'.</
=={{header|SNOBOL4}}==
{{works with|CSNOBOL4}}
This code loads the <tt>libm</tt> library into the variable <tt>ffi_m</tt> and binds the <tt>hypot()</tt> function to the variable <tt>ffi_m_hypot</tt>. (The variable names are arbitrary.) It then declares a SNOBOL4 function called <tt>hypot()</tt> which takes two <tt>double</tt>s as arguments and returns a <tt>double</tt>, binding this name to the <tt>ffi_m_hypot</tt> object returned earlier. It then outputs four hypotenuse calculations using those values.
<syntaxhighlight lang="snobol4">-INCLUDE 'ffi.sno'
ffi_m = FFI_DLOPEN('/usr/lib/x86_64-linux-gnu/libm.so')
ffi_m_hypot = FFI_DLSYM(ffi_m, 'hypot')
DEFINE_FFI('hypot(double,double)double', ffi_m_hypot)
OUTPUT = hypot(1,2)
OUTPUT = hypot(2,3)
OUTPUT = hypot(3,4)
OUTPUT = hypot(4,5)
END</syntaxhighlight>
Execution looks like this:
<pre>$ snobol4 ffitest.sno
2.23606797749979
3.60555127546399
5.
6.40312423743285</pre>
=={{header|Tcl}}==
{{libheader|Ffidl}}
<
if {[catch {
Line 1,162 ⟶ 2,007:
# Create the OpenImage command by other means here...
}
set handle [OpenImage "/the/file/name"]</
Note that if the library is appropriately set up with the correct entry function, it can be accessed directly with <code>load</code> which will cause it to register a Tcl command for the functionality it exports. [http://www.swig.org SWIG] can be used to automatically generate the interface code. Alternatively, [[:Category:Critcl|critcl]] can be used to allow writing glue [[C]] code directly embedded within a Tcl script.
With this many ways to perform the call, the best approach often depends on the size and complexity of the API being mapped. SWIG excels at large APIs, Ffidl is better when you just want to call a particular simple function, and critcl handles complex cases (callbacks, etc.) better than the other two.
=={{header|TXR}}==
==== Call <code>uname</code> on Linux ====
<pre>This is the TXR Lisp interactive listener of TXR 176.
Use the :quit command or type Ctrl-D on empty line to exit.
1> (typedef utsarray (zarray 65 char))
#<ffi-type (zarray 65 char)>
2> (typedef utsname (struct utsname (sysname utsarray)
(nodename utsarray)
(release utsarray)
(version utsarray)
(machine utsarray)
(domainname utsarray)))
#<ffi-type (struct utsname (sysname utsarray) (nodename utsarray) (release utsarray)
(version utsarray) (machine utsarray) (domainname utsarray))>
3> (with-dyn-lib nil (deffi uname "uname" int ((ptr-out utsname))))
** warning: (expr-3:1) defun: redefining uname, which is a built-in defun
#:lib-0176
4> (let ((u (new utsname))) (prinl (uname u)) u)
0
#S(utsname sysname "Linux" nodename "zelenka" release "3.2.0-40-generic"
version "#64-Ubuntu SMP Mon Mar 25 21:22:26 UTC 2013" machine "i686"
domainname "(none)")</pre>
We use <code>typedef</code> to condense the declarations, much like in C. The FFI handles nested types like arrays in structures.
The <code>zarray</code> type denotes null-terminated arrays. A <code>zarray</code> of <code>char</code> is specialized; it converts between Lisp strings (which use wide characters made of Unicode code points) and C <code>char</code> strings encoded in UTF-8.
The argument of <code>uname</code> is <code>(ptr-out utsname)</code>. The semantics of <code>ptr-out</code> in this situation is that FFI prepares a C version of the Lisp structure, but doesn't perform any conversions from Lisp to initialize it. This not only saves CPU cycles, but allows us to use a blank structure produced by <code>(new utsname)</code> all of whose slots are <code>nil</code> and so wouldn't convert to C character arrays anyway! The function is called, and then conversions out of the structure to the Lisp structure take place, filling its slots with string values.
The <code>nil</code> argument in the <code>with-dyn-lib</code> macro causes the underlying implementation to call <code>dlopen(NULL)</code> to get access to the dynamic symbols available in the executable. We can use the name of a shared library instead, or a handle from TXR's <code>dlopen</code> library function.
=={{header|Ursala}}==
When abs(x) is evaluated, a run time check is performed for the
Line 1,172 ⟶ 2,048:
and if found, it is used. If not, the user defined replacement
function is invoked.
<
#import flo
my_replacement = fleq/0.?/~& negative
abs = math.|fabs my_replacement</
=={{header|VBA}}==
Here is an example using a Fortran function compiled as a DLL, using Intel Fortran.
First the DLL. Compile with '''ifort /dll vbafun.f90'''. The DLL must be in a directory in the PATH environment variable. Notice that for 32 bits VBA, DLL functions must be STDCALL, and not CDECL (the default with Intel Fortran). In 64 bits, there is only one calling convention, so it's not a problem anymore.
<syntaxhighlight lang="fortran">function ffun(x, y)
implicit none
!DEC$ ATTRIBUTES DLLEXPORT, STDCALL, REFERENCE :: ffun
double precision :: x, y, ffun
ffun = x + y * y
end function</syntaxhighlight>
Here is a VBA subroutine using the DLL
<syntaxhighlight lang="vb">Option Explicit
Declare Function ffun Lib "vbafun" (ByRef x As Double, ByRef y As Double) As Double
Sub Test()
Dim x As Double, y As Double
x = 2#
y = 10#
Debug.Print ffun(x, y)
End Sub</syntaxhighlight>
=={{header|Wren}}==
{{trans|C}}
An embedded program so we can ask the C host to call the shared library function for us.
<syntaxhighlight lang="wren">/* Call_a_function_in_a_shared_library.wren */
var RTLD_LAZY = 1
foreign class DL {
construct open(file, mode) {}
foreign call(symbol, arg)
foreign close()
}
class My {
static openimage(s) {
System.print("internal openimage opens %(s)...")
if (!__handle) __handle = 0
__handle = __handle + 1
return __handle - 1
}
}
var file = "fake.img"
var imglib = DL.open("./fakeimglib.so", RTLD_LAZY)
var imghandle = (imglib != null) ? imglib.call("openimage", file) : My.openimage(file)
System.print("opened with handle %(imghandle)")
if (imglib != null) imglib.close()</syntaxhighlight>
<br>
We also need to create the shared library, fakeimglib.so, and place it in the current directory.
<syntaxhighlight lang="c">/*
gcc -c -fpic fakeimglib.c
gcc -shared fakeimglib.o -o fakeimglib.so
*/
#include <stdio.h>
int openimage(const char *s) {
static int handle = 100;
fprintf(stderr, "opening %s\n", s);
return handle++;
}</syntaxhighlight>
<br>
Finally, we embed the Wren script in the following C program, compile and run it:
<syntaxhighlight lang="c">/* gcc Call_a_function_in_a_shared_library.c -o Call_a_function_in_a_shared_library -ldl -lwren -lm */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <dlfcn.h>
#include "wren.h"
/* C <=> Wren interface functions */
void C_dlAllocate(WrenVM* vm) {
const char *file = wrenGetSlotString(vm, 1);
int mode = (int)wrenGetSlotDouble(vm, 2);
void *imglib = dlopen(file, mode);
if (imglib == NULL) wrenSetSlotNull(vm, 0);
void** pimglib = (void**)wrenSetSlotNewForeign(vm, 0, 0, sizeof(void*));
*pimglib = imglib;
}
void C_call(WrenVM* vm) {
void *imglib = *(void**)wrenGetSlotForeign(vm, 0);
const char *symbol = wrenGetSlotString(vm, 1);
const char *arg = wrenGetSlotString(vm, 2);
int (*extopenimage)(const char *);
extopenimage = dlsym(imglib, symbol);
int imghandle = extopenimage(arg);
wrenSetSlotDouble(vm, 0, (double)imghandle);
}
void C_close(WrenVM* vm) {
void *imglib = *(void**)wrenGetSlotForeign(vm, 0);
dlclose(imglib);
}
WrenForeignClassMethods bindForeignClass(WrenVM* vm, const char* module, const char* className) {
WrenForeignClassMethods methods;
methods.finalize = NULL;
if (strcmp(module, "main") == 0) {
if (strcmp(className, "DL") == 0) {
methods.allocate = C_dlAllocate;
}
}
return methods;
}
WrenForeignMethodFn bindForeignMethod(
WrenVM* vm,
const char* module,
const char* className,
bool isStatic,
const char* signature) {
if (strcmp(module, "main") == 0) {
if (strcmp(className, "DL") == 0) {
if (!isStatic && strcmp(signature, "call(_,_)") == 0) return C_call;
if (!isStatic && strcmp(signature, "close()") == 0) return C_close;
}
}
return NULL;
}
static void writeFn(WrenVM* vm, const char* text) {
printf("%s", text);
}
void errorFn(WrenVM* vm, WrenErrorType errorType, const char* module, const int line, const char* msg) {
switch (errorType) {
case WREN_ERROR_COMPILE:
printf("[%s line %d] [Error] %s\n", module, line, msg);
break;
case WREN_ERROR_STACK_TRACE:
printf("[%s line %d] in %s\n", module, line, msg);
break;
case WREN_ERROR_RUNTIME:
printf("[Runtime Error] %s\n", msg);
break;
}
}
char *readFile(const char *fileName) {
FILE *f = fopen(fileName, "r");
fseek(f, 0, SEEK_END);
long fsize = ftell(f);
rewind(f);
char *script = malloc(fsize + 1);
fread(script, 1, fsize, f);
fclose(f);
script[fsize] = 0;
return script;
}
int main(int argc, char **argv) {
WrenConfiguration config;
wrenInitConfiguration(&config);
config.writeFn = &writeFn;
config.errorFn = &errorFn;
config.bindForeignClassFn = &bindForeignClass;
config.bindForeignMethodFn = &bindForeignMethod;
WrenVM* vm = wrenNewVM(&config);
const char* module = "main";
const char* fileName = "Call_a_function_in_a_shared_library.wren";
char *script = readFile(fileName);
WrenInterpretResult result = wrenInterpret(vm, module, script);
switch (result) {
case WREN_RESULT_COMPILE_ERROR:
printf("Compile Error!\n");
break;
case WREN_RESULT_RUNTIME_ERROR:
printf("Runtime Error!\n");
break;
case WREN_RESULT_SUCCESS:
break;
}
wrenFreeVM(vm);
free(script);
return 0;
}</syntaxhighlight>
{{out}}
<pre>
Same as C example depending on whether fakeimglib.so is present in the current directory or not.
</pre>
=={{header|X86-64 Assembly}}==
===UASM 2.52===
<syntaxhighlight lang="asm">
option casemap:none
windows64 equ 1
linux64 equ 3
ifndef __LIB_CLASS__
__LIB_CLASS__ equ 1
if @Platform eq windows64
option dllimport:<kernel32>
HeapAlloc proto :qword, :dword, :qword
HeapFree proto :qword, :dword, :qword
ExitProcess proto :dword
GetProcessHeap proto
LoadLibraryA proto :qword
FreeLibrary proto :qword
GetProcAddress proto :qword, :qword
option dllimport:none
exit equ ExitProcess
dlsym equ GetProcAddress
dlclose equ FreeLibrary
elseif @Platform eq linux64
malloc proto :qword
free proto :qword
exit proto :dword
dlclose proto :qword
dlopen proto :qword, :dword
dlsym proto :qword, :qword
endif
printf proto :qword, :vararg
CLASS libldr
CMETHOD getproc
ENDMETHODS
libname db 100 dup (0)
plib dq ?
ENDCLASS
METHOD libldr, Init, <VOIDARG>, <>, library:qword, namelen:qword
mov rbx, thisPtr
assume rbx:ptr libldr
.if library != 0
mov rcx, namelen
mov rsi, library
lea rdi, [rbx].libname
rep movsb
if @Platform eq windows64
invoke LoadLibraryA, addr [rbx].libname
.if rax == 0
invoke printf, CSTR("--> Failed to load library",10)
.else
mov [rbx].plib, rax
.endif
elseif @Platform eq linux64
invoke dlopen, addr [rbx].libname, 1
.if rax == 0
lea rax, [rbx].libname
invoke printf, CSTR("--> Failed to load library %s",10), rax
.else
mov [rbx].plib, rax
.endif
endif
.else
invoke printf, CSTR("--> Library name to load required..",10)
.endif
mov rax, rbx
assume rbx:nothing
ret
ENDMETHOD
METHOD libldr, getproc, <VOIDARG>, <>, func:qword
local tmp:qword
mov tmp, func
;; Just return RAX..
invoke dlsym, [thisPtr].libldr.plib, tmp
ret
ENDMETHOD
METHOD libldr, Destroy, <VOIDARG>, <>
mov rbx, thisPtr
assume rbx:ptr libldr
.if [rbx].plib != 0
invoke dlclose, [rbx].plib
.endif
assume rbx:nothing
ret
ENDMETHOD
endif
.data
LibName db "./somelib.l",0
.code
main proc
local ldr:ptr libldr
invoke printf, CSTR("--> Loading %s .. ",10), addr LibName
mov ldr, _NEW(libldr, addr LibName, sizeof(LibName))
ldr->getproc(CSTR("disappointment"))
.if rax == 0
lea rax, idisappointment
.endif
call rax
_DELETE(ldr)
invoke exit, 0
ret
main endp
idisappointment:
push rbp
mov rbp, rsp
invoke printf, CSTR("--> Well this is a internal disappointment..",10)
pop rbp
mov rax, 0
ret
end
</syntaxhighlight>
It's worth pointing out that under linux, dlopen CAN return NULL WITHOUT it being an error. One SHOULD call dlerror() to check for actual errors.
{{out}}
<pre>
--> Loading ./somelib.l ..
--> Well this is a external disappointment..
And on failure...
--> Loading ./somelib.l ..
--> Failed to load library ./somelib.l
--> Well this is a internal disappointment..
</pre>
=={{header|zkl}}==
In zkl, extensions/new objects are written in C as shared libraries. For example, big nums are implemented as a small glue library in front of GMP:
<syntaxhighlight lang="zkl">var BN=Import("zklBigNum");
BN(1)+2 //--> BN(3)</syntaxhighlight>
and it "just works" as all objects are "the same" whether statically or dynamically linked.
{{omit from|Batch File|Except for rundll32.exe (which is rather limited) there is no way of calling an external function}}
{{omit from|
{{omit from|GUISS}}
{{omit from|M4}}
{{omit from|Maxima}}
{{omit from|ML/I}}
{{omit from|Retro|No FFI}}
{{omit from|Scheme|No standard FFI, due to no standard implementation.}}
{{omit from|TI-83 BASIC|Does not have a standard FFI.}}
{{omit from|TI-89 BASIC|Does not have a standard FFI.}}
| |||