Initial data commit

Task/Call-a-function-in-a-shared-library/Go/call-a-function-in-a-shared-library-1.go

@@ -0,0 +1,8 @@
+#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++;
+}

Task/Call-a-function-in-a-shared-library/Go/call-a-function-in-a-shared-library-2.go

@@ -0,0 +1,52 @@
+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)
+}