1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
|
// https://doc.rust-lang.org/rust-by-example/std/box.html
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <stc/ccommon.h>
struct {
double x;
double y;
} typedef Point;
// A Rectangle can be specified by where its top left and bottom right
// corners are in space
struct {
Point top_left;
Point bottom_right;
} typedef Rectangle;
#define i_val Point
#define i_opt c_no_lookup
#include <stc/cbox.h> // cbox_Point
#define i_val Rectangle
#define i_opt c_no_lookup
#include <stc/cbox.h> // cbox_Rectangle
// Box in box:
#define i_valboxed cbox_Point // NB: use i_valboxed when value is a cbox or carc!
// it will auto define i_valdrop, i_valfrom, and i_cmp.
#define i_tag BoxPoint
#define i_opt c_no_lookup
#include <stc/cbox.h> // cbox_BoxPoint
Point origin(void) {
return (Point){ .x=1.0, .y=2.0 };
}
cbox_Point boxed_origin(void) {
// Allocate this point on the heap, and return a pointer to it
return cbox_Point_make((Point){ .x=2.0, .y=3.0 });
}
int main(void) {
// Stack allocated variables
Point point = origin();
Rectangle rectangle = (Rectangle){
.top_left = origin(),
.bottom_right = (Point){ .x=3.0, .y=-4.0 }
};
// Declare auto-deleted box objects
c_AUTO (cbox_Rectangle, boxed_rectangle)
c_AUTO (cbox_Point, boxed_point)
c_AUTO (cbox_BoxPoint, box_in_a_box, boxbox2)
{
// Heap allocated rectangle
boxed_rectangle = cbox_Rectangle_make((Rectangle){
.top_left = origin(),
.bottom_right = (Point){ .x=3.0, .y=-4.0 }
});
// The output of functions can be boxed
boxed_point = cbox_Point_from(origin());
// Double indirection
box_in_a_box = cbox_BoxPoint_make(boxed_origin());
boxbox2 = cbox_BoxPoint_from(point); // !!
printf("boxbox2: x=%f\n", boxbox2.get->get->x);
printf("Point occupies %" c_ZU " bytes on the stack\n",
sizeof(point));
printf("Rectangle occupies %" c_ZU " bytes on the stack\n",
sizeof(rectangle));
// box size == pointer size
printf("Boxed point occupies %" c_ZU " bytes on the stack\n",
sizeof(boxed_point));
printf("Boxed rectangle occupies %" c_ZU " bytes on the stack\n",
sizeof(boxed_rectangle));
printf("Boxed box occupies %" c_ZU " bytes on the stack\n",
sizeof(box_in_a_box));
// Copy the data contained in `boxed_point` into `unboxed_point`
Point unboxed_point = *boxed_point.get;
printf("Unboxed point occupies %" c_ZU " bytes on the stack\n",
sizeof(unboxed_point));
}
}
|
