link#

C Strings are Terrible! | Tsoding | C의 String은 끔찍하다. ㅋ C String 정말 끔찍해! 자동 더빙 | Tsoding
같이 연관 되는 blog글
- These patterns prevent crashes, overflow, UB, or invalid memory access
- C & Rust로 구현한(StringView)
  - StringView(C, Rust 코드 비교해서 정리)

Zig Code#

sample zig code
zig version (0.16.0-dev.2984+cb7d2b056)

// main.zig
const std = @import("std");
const Io = std.Io;

const string_view_zig = @import("string_view_zig");

const StringView = struct {
    data: [*]const u8,
    count: usize,

    // String_View sv(const char *cstr)
    pub fn sv(cstr: [*:0]const u8) StringView {
        return StringView{
            .data = cstr,
            .count = std.mem.len(cstr),
        };
    }

    pub fn chopLeft(self: *StringView, n: usize) void {
        var k = n;
        if (k > self.count) {
            k = self.count;
        }

        self.count -= k;
        self.data += k;
    }

    pub fn chopRight(self: *StringView, n: usize) void {
        var k = n;
        if (k > self.count) {
            k = self.count;
        }

        self.count -= k;
    }
};

pub fn main(init: std.process.Init) !void {
    try std.Io.File.stdout().writeStreamingAll(init.io, "StringView zig lang (ver0.16.0-dev.2984+cb7d2b056)\n\n\n");

    var s = StringView.sv("Hello, World");

    s.chopRight(3);
    s.chopLeft(2);

    std.debug.print("{s}\n", .{s.data[0..s.count]});
}

result

$ zig build run

StringView zig lang (ver0.16.0-dev.2984+cb7d2b056)


llo, Wo

zig코드 자세히 분석#

pointer to a null-terminated C string.#

In Zig,

cstr: [*:0]const u8

means pointer to a null-terminated C string.
I used this type because your original C code takes const char *, and in C that usually means a 0-terminated string.
Let’s break it down.

1. Your C code#

String_View sv(const char *cstr) {
    return (String_View){
        .data = cstr,
        .count = strlen(cstr),
    };
}

Here:

// main.c
const char *cstr

means:
- pointer to char
- string must end with '\0'
- required by strlen
So Zig must use a type that guarantees null-termination.

2. Meaning of `[ *:0 ]const u8` in Zig#

[*:0]const u8

Breakdown:

Part	Meaning
`u8`	byte (same as char)
`const`	read-only
`[*]`	pointer to many items
`:0`	sentinel value = 0 (null terminator)

[*:0]const u8

means

pointer to many bytes, terminated by 0

Exactly like:

// main.c
const char *

but safer, because Zig knows there is a terminator.

3. Why not []const u8 ?#

Because this:

[]const u8

is a slice, not a C string.
Slice already has length:

ptr + len

So you don’t need strlen.
Your C code uses strlen, so we need null-terminated string.

4. Why `std.mem.len(cstr)` works#

std.mem.len expects a sentinel pointer:

std.mem.len(cstr)

Works only if type is:

[*:0]const u8

because it scans until 0.
Same as:

// main.c
strlen(cstr)

5. If we used wrong type (example)#

❌ Wrong:

pub fn sv(cstr: []const u8) StringView

Then this fails:

std.mem.len(cstr) // error

because slice already has length.

6. Summary#

Zig type	Meaning	C equivalent
`[*:0]const u8`	null-terminated pointer	`const char *`
`[]const u8`	slice (ptr + len)	pointer + length
`[*]const u8`	pointer without length	raw pointer

So I used:

// main.zig
cstr: [*:0]const u8

because your C code uses:

// main.c
const char * + strlen

which requires a null-terminated string.

link#

Zig Code#

zig코드 자세히 분석#

pointer to a null-terminated C string.#

1. Your C code#

2. Meaning of [ *:0 ]const u8 in Zig#

3. Why not []const u8 ?#

4. Why std.mem.len(cstr) works#

5. If we used wrong type (example)#

6. Summary#

2. Meaning of `[ *:0 ]const u8` in Zig#

4. Why `std.mem.len(cstr)` works#