Merge pull request #1 from juanmanuel-tirado/chapter/cgo

Added cgo content.

Author: juanmanuel-tirado

013_cgo/example_01/main.go

@@ -0,0 +1,13 @@
+package main
+
+// #include <stdio.h>
+// void func_in_c() {
+//	printf("printed with C code\n");
+// }
+import "C"
+import "fmt"
+
+func main() {
+	C.func_in_c()
+	fmt.Println("printed with Go code")
+}

013_cgo/example_02/main.go

@@ -0,0 +1,16 @@
+package main
+
+/*
+ #include <stdio.h>
+ // This is a comment
+ void func_in_c() {
+	printf("printed with C code\n");
+ }
+*/
+import "C"
+import "fmt"
+
+func main() {
+	C.func_in_c()
+	fmt.Println("printed with Go code")
+}

013_cgo/example_03/main.go

@@ -0,0 +1,20 @@
+package main
+
+/*
+ int sum(int a, int b) {
+	return a + b;
+ }
+*/
+import "C"
+import (
+	"fmt"
+	"reflect"
+)
+
+func main() {
+	a := 1
+	b := 1
+	c := C.sum(C.int(a), C.int(b))
+	fmt.Printf("%d + %d = %d\n", a, b, c)
+	fmt.Println(reflect.TypeOf(c).MethodByName("))
+}

013_cgo/example_04/main.go

@@ -0,0 +1,67 @@
+package main
+
+/*
+#include<stdio.h>
+void f_char(char in) {
+	printf("char %c\n", in);
+}
+void f_schar(signed char in) {
+	printf("signed char %X\n", in);
+}
+void f_uchar(unsigned char in) {
+	printf("unsigned char %c\n", in);
+}
+void f_short(short in) {
+	printf("short %d\n", in);
+}
+void f_ushort(unsigned short in) {
+	printf("unsigned short %u\n", in);
+}
+void f_int(int in) {
+	printf("int %d\n", in);
+}
+void f_uint(unsigned int in) {
+	printf("unsigned int %u\n", in);
+}
+void f_long(long in) {
+	printf("long %X\n", in);
+}
+void f_ulong(unsigned long in) {
+	printf("unsigned long %X\n", in);
+}
+void f_longlong(long long in) {
+	printf("long long %X\n", in);
+}
+void f_ulonglong(unsigned long long in) {
+	printf("unsigned long long %X\n", in);
+}
+void f_float(float in) {
+	printf("float %e\n", in);
+}
+void f_double(double in) {
+	printf("float %e\n", in);
+}
+*/
+import "C"
+import "math"
+
+func main() {
+	C.f_char(C.char(42))
+	C.f_schar(C.schar(-42))
+	C.f_uchar(C.uchar(42))
+
+	C.f_short(C.short(-42))
+	C.f_ushort(C.ushort(42))
+
+	C.f_int(C.int(-42))
+	C.f_uint(C.uint(math.MaxInt32))
+
+	C.f_long(C.long(-42))
+	C.f_ulong(C.ulong(math.MaxUint64))
+
+	C.f_longlong(C.longlong(math.MaxInt64))
+	C.f_ulonglong(C.ulonglong(math.MaxUint64))
+
+	C.f_float(C.float(math.MaxFloat32))
+	C.f_double(C.double(math.MaxFloat64))
+}

013_cgo/example_05/main.go

@@ -0,0 +1,32 @@
+package main
+
+/*
+ #include <stdlib.h>
+ #include <stdio.h>
+ void func_c_print(char* input) {
+	 printf("C prints: %s\n",input);
+ }
+ char* func_c_str() {
+	 char* str = "this is a C string";
+	 return str;
+ }
+*/
+import "C"
+import (
+	"fmt"
+	"unsafe"
+)
+
+func main() {
+	str := "this is a Go string"
+	goToC := C.CString(str)
+	C.func_c_print(goToC)
+	defer C.free(unsafe.Pointer(goToC))
+
+	cStr := C.func_c_str()
+	cToGo := C.GoString(cStr)
+	fmt.Printf("Go prints: %s\n", cToGo)
+
+	nCToGo := C.GoStringN(cStr, 10)
+	fmt.Printf("Go prints: %s\n", nCToGo)
+}

013_cgo/example_06/main.go

@@ -0,0 +1,21 @@
+package main
+
+/*
+ #include<stdio.h>
+ int sum_array(int a[], int length)  {
+	 int i,result = 0;
+	 for (i = 0; i < length; i++) {
+		result += a[i];
+	 }
+	 return result;
+ }
+*/
+import "C"
+import "fmt"
+
+func main() {
+	a := []int32{0, 1, 2, 3, 4}
+	first := (*C.int)(&a[0])
+	res := C.sum_array(first, C.int(len(a)))
+	fmt.Printf("The result is: %d\n", res)
+}

013_cgo/example_07/main.go

@@ -0,0 +1,29 @@
+package main
+
+/*
+ #include <stdlib.h>
+ int* create_array(int n) {
+	int* result;
+	result = (int*)malloc(sizeof(int)*n);
+	for( int i = 0; i < n; i++){
+		result[i] = i;
+	}
+	return result;
+ }
+*/
+import "C"
+import (
+	"fmt"
+	"unsafe"
+)
+
+func main() {
+	array := C.create_array(5)
+	defer C.free(unsafe.Pointer(array))
+	fmt.Printf("C returns a pointer: %d\n", array)
+	aux := (*[5]int32)(unsafe.Pointer(array))
+	fmt.Printf("We extract the content: %d\n", aux)
+	for _, i := range aux {
+		fmt.Printf("->%d\n", i)
+	}
+}

013_cgo/example_08/main.go

@@ -0,0 +1,27 @@
+package main
+
+/*
+ #include <stdio.h>
+ typedef struct {
+	 int id;
+	 int age;
+ } User;
+
+ void print_user(User *u) {
+	 printf("Id: %d\n", u->id);
+	 printf("Age: %d\n", u->age);
+ }
+*/
+import "C"
+import "unsafe"
+
+type User struct {
+	Id  int32
+	Age int32
+}
+
+func main() {
+	u := User{1234, 33}
+	userToC := (*C.User)(unsafe.Pointer(&u))
+	C.print_user(userToC)
+}

013_cgo/example_09/main.go

@@ -0,0 +1,30 @@
+package main
+
+/*
+ #include <stdlib.h>
+ typedef struct {
+	char* name;
+	int id;
+ } User;
+
+ User* create_user(char* name) {
+	 User* u;
+	 u = (User*)malloc(sizeof(User*));
+	 u -> name = name;
+	 u -> id = 1234;
+	 return u;
+ }
+*/
+import "C"
+import (
+	"fmt"
+	"unsafe"
+)
+
+func main() {
+	name := C.CString("John")
+	u := C.create_user(name)
+	defer C.free(unsafe.Pointer(u))
+	fmt.Printf("User name: %s\n", C.GoString(u.name))
+	fmt.Printf("User id: %d\n", u.id)
+}

013_cgo/example_10/main.go

@@ -0,0 +1,23 @@
+package main
+
+/*
+ #include <stdlib.h>
+ typedef struct {
+	char* name;
+	int id;
+ } User;
+*/
+import "C"
+import (
+	"fmt"
+	"unsafe"
+)
+
+func main() {
+	name := C.CString("John")
+	defer C.free(unsafe.Pointer(name))
+	x := C.User{name: name, id: C.int(1234)}
+	fmt.Println(C.GoString(x.name), x.id)
+	// Should we release x?
+	//C.free(unsafe.Pointer(&x))
+}