add support C.**char

raygui3_5/cstring.go

@@ -0,0 +1,102 @@
+package raygui3_5
+
+/*
+#include <stdlib.h>
+// Code from https://blog.pytool.com/language/golang/cgo/go-cgo-string/
+
+static char** make_str_array(int size) {
+	return calloc(sizeof(char*), size);
+}
+
+static int len_str_array(char **arr) {
+	int i = 0;
+	while (arr[i] != NULL) i++;
+	return i+1; // NULL does count
+}
+
+static void set_str_array(char **arr, int idx, char *s) {
+	arr[idx] = s;
+}
+
+static void free_str_array(char **arr, int size) {
+	int i;
+	for (i = 0; i < size; i++) {
+		free(arr[i]);
+	}
+	free(arr);
+}
+*/
+import "C"
+
+import (
+	"unsafe"
+)
+
+// CStringArray represents an array of pointers to NULL terminated C strings,
+// the array itself is terminated with a NULL
+type CStringArray struct {
+	Pointer unsafe.Pointer
+	Length  int
+}
+
+// NewCStringArray returns an instance of CStringArray
+func NewCStringArray() *CStringArray {
+	return &CStringArray{}
+}
+
+// NewCStringArrayFromSlice makes an instance of CStringArray then copy the
+// input slice to it.
+func NewCStringArrayFromSlice(ss []string) *CStringArray {
+	var arr CStringArray
+	arr.Copy(ss)
+	return &arr
+}
+
+func NewCStringArrayFromPointer(p unsafe.Pointer) *CStringArray {
+	return &CStringArray{
+		Length:  int(C.len_str_array((**C.char)(p))),
+		Pointer: p,
+	}
+}
+
+// ToSlice converts CStringArray to Go slice of strings
+func (arr *CStringArray) ToSlice() []string {
+	if arr.Length == 0 || arr.Pointer == nil {
+		return []string{}
+	}
+
+	var ss []string
+	var cs **C.char
+	defer C.free(unsafe.Pointer(cs))
+	p := uintptr(arr.Pointer)
+	for {
+		cs = (**C.char)(unsafe.Pointer(p))
+		if *cs == nil { // skip NULL - the last element
+			break
+		}
+		ss = append(ss, C.GoString(*cs))
+		p += unsafe.Sizeof(p)
+	}
+
+	return ss
+}
+
+// Copy converts Go slice of strings to C underlying struct of CStringArray
+func (arr *CStringArray) Copy(ss []string) {
+	arr.Length = len(ss) + 1 // one more element for NULL at the end
+	arr.Pointer = unsafe.Pointer(C.make_str_array(C.int(arr.Length)))
+
+	for i, s := range ss {
+		cs := C.CString(s) // will be free by Free() method
+		C.set_str_array((**C.char)(arr.Pointer), C.int(i), cs)
+	}
+}
+
+// Free frees C underlying struct of CStringArray
+// MUST call this method after using CStringArray
+// Exception: If you use NewCStringArrayFromPointer() to create CStringArray object
+// and you use other way to free C underlying structure pointed by the pointer,
+// then don't need to call Free()
+func (arr *CStringArray) Free() {
+	C.free_str_array((**C.char)(arr.Pointer), C.int(arr.Length))
+}