Call a function in a shared library: Difference between revisions

=={{header|Kotlin}}==

{{trans|C}}

{{Works with|Ubuntu 14.04}}

This is the C code to produce fakeimglib.so:

<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++;

}</lang>

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:

<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")

}</lang>

{{out}}

<pre>

Same as C entry

</pre>