blob: fb8f13d843f8ba9f2089a0c9d5eb4b3dedc878e6 (
plain)
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
|
//
// ------------------------------------------------------------
// TOP SECRET TOP SECRET TOP SECRET TOP SECRET TOP SECRET
// ------------------------------------------------------------
//
// Are you ready for the THE TRUTH about Zig string literals?
//
// Here it is:
//
// @TypeOf("foo") == *const [3:0]u8
//
// Which means a string literal is a "constant pointer to a
// zero-terminated (null-terminated) fixed-size array of u8".
//
// Now you know. You've earned it. Welcome to the secret club!
//
// ------------------------------------------------------------
//
// Why do we bother using a zero/null sentinel to terminate
// strings in Zig when we already have a known length?
//
// Versatility! Zig strings are compatible with C strings (which
// are null-terminated) AND can be coerced to a variety of other
// Zig types:
//
// const a: [5]u8 = "array".*;
// const b: *const [16]u8 = "pointer to array";
// const c: []const u8 = "slice";
// const d: [:0]const u8 = "slice with sentinel";
// const e: [*:0]const u8 = "many-item pointer with sentinel";
// const f: [*]const u8 = "many-item pointer";
//
// All but 'f' may be printed. (A many-item pointer without a
// sentinel is not safe to print because we don't know where it
// ends!)
//
const print = @import("std").debug.print;
const WeirdContainer = struct {
data: [*]const u8,
length: usize,
};
pub fn main() void {
// WeirdContainer is an awkward way to house a string.
//
// Being a many-item pointer (with no sentinel termination),
// the 'data' field "loses" the length information AND the
// sentinel termination of the string literal "Weird Data!".
//
// Luckily, the 'length' field makes it possible to still
// work with this value.
const foo = WeirdContainer{
.data = "Weird Data!",
.length = 11,
};
// How do we get a printable value from 'foo'? One way is to
// turn it into something with a known length. We do have a
// length... You've actually solved this problem before!
//
// Here's a big hint: do you remember how to take a slice?
const printable = ???;
print("{s}\n", .{printable});
}
|
