cgo: examples

_demo/cgobasic/cgobasic.go

@@ -0,0 +1,55 @@
+package main
+
+/*
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+*/
+import "C"
+import (
+	"fmt"
+	"unsafe"
+)
+
+func main() {
+	// C.CString example
+	cstr := C.CString("Hello, World!")
+	C.puts(cstr)
+
+	// C.CBytes example
+	bytes := []byte{65, 66, 67, 68} // ABCD
+	cbytes := C.CBytes(bytes)
+
+	// C.GoString example
+	gostr := C.GoString(cstr)
+	println("Converted back to Go string: ", gostr)
+
+	// C.GoStringN example (with length limit)
+	gostringN := C.GoStringN(cstr, 5) // only take first 5 characters
+	println("Length-limited string: ", gostringN)
+
+	// C.GoBytes example
+	gobytes := C.GoBytes(cbytes, 4) // 4 is the length
+	println("Converted back to Go byte slice: ", gobytes)
+
+	// C math library examples
+	x := 2.0
+	// Calculate square root
+	sqrtResult := C.sqrt(C.double(x))
+	fmt.Printf("sqrt(%v) = %v\n", x, float64(sqrtResult))
+
+	// Calculate sine
+	sinResult := C.sin(C.double(x))
+	fmt.Printf("sin(%v) = %v\n", x, float64(sinResult))
+
+	// Calculate cosine
+	cosResult := C.cos(C.double(x))
+	fmt.Printf("cos(%v) = %v\n", x, float64(cosResult))
+
+	// Calculate natural logarithm
+	logResult := C.log(C.double(x))
+	fmt.Printf("log(%v) = %v\n", x, float64(logResult))
+
+	C.free(unsafe.Pointer(cstr))
+	C.free(cbytes)
+}

_demo/cgocfiles/cgocfiles.go

@@ -0,0 +1,21 @@
+package main
+
+/*
+#include "in.h"
+*/
+import "C"
+import "fmt"
+
+// TODO(lijie): workaround for c files compiling
+const (
+	LLGoFiles   = "in.c"
+	LLGoPackage = "link"
+)
+
+func main() {
+	r := C.test_structs(&C.s4{a: 1}, &C.s8{a: 1, b: 2}, &C.s12{a: 1, b: 2, c: 3}, &C.s16{a: 1, b: 2, c: 3, d: 4}, &C.s20{a: 1, b: 2, c: 3, d: 4, e: 5})
+	fmt.Println(r)
+	if r != 35 {
+		panic("test_structs failed")
+	}
+}

_demo/cgocfiles/in.c

@@ -0,0 +1,12 @@
+#include <stdio.h>
+#include "in.h"
+
+int test_structs(s4* s4, s8* s8, s12* s12, s16* s16, s20* s20) {
+  printf("s4.a: %d\n", s4->a);
+  printf("s8.a: %d, s8.b: %d\n", s8->a, s8->b);
+  printf("s12.a: %d, s12.b: %d, s12.c: %d\n", s12->a, s12->b, s12->c);
+  printf("s16.a: %d, s16.b: %d, s16.c: %d, s16.d: %d\n", s16->a, s16->b, s16->c, s16->d);
+  printf("s20.a: %d, s20.b: %d, s20.c: %d, s20.d: %d, s20.e: %d\n", s20->a, s20->b, s20->c, s20->d, s20->e);
+
+  return s4->a + s8->a + s8->b + s12->a + s12->b + s12->c + s16->a + s16->b + s16->c + s16->d + s20->a + s20->b + s20->c + s20->d + s20->e;
+}

_demo/cgocfiles/in.h

@@ -0,0 +1,33 @@
+#pragma once
+
+typedef struct {
+	int a;
+} s4;
+
+typedef struct {
+  int a;
+  int b;
+} s8;
+
+typedef struct {
+  int a;
+  int b;
+  int c;
+} s12;
+
+typedef struct {
+  int a;
+  int b;
+  int c;
+  int d;
+} s16;
+
+typedef struct {
+  int a;
+  int b;
+  int c;
+  int d;
+  int e;
+} s20;
+
+extern int test_structs(s4* s4, s8* s8, s12* s12, s16* s16, s20* s20);

_demo/cgopython/cgopython.go

@@ -0,0 +1,18 @@
+package main
+
+/*
+#cgo pkg-config: python3-embed
+#include <Python.h>
+*/
+import "C"
+
+// TODO(lijie): workaround for cgo pkg-config not working
+const (
+	LLGoPackage = "link: $LLGO_LIB_PYTHON; $(pkg-config --libs python3-embed)"
+)
+
+func main() {
+	C.Py_Initialize()
+	defer C.Py_Finalize()
+	C.PyRun_SimpleString(C.CString("print('Hello, Python!')"))
+}