i3ipc-packed-struct-reduction.zig

const std = @import("std");

// Proving to myself the struct should be 14 bytes
// #include <stdio.h>
// #include <stdint.h>

// // /** Never change this, only on major IPC breakage (don’t do that) */
// #define I3_IPC_MAGIC "i3-ipc"

// typedef struct i3_ipc_header {
    // /* 6 = strlen(I3_IPC_MAGIC) */
    // char magic[6];
    // uint32_t size;
    // uint32_t type;
// } __attribute__((packed)) i3_ipc_header_t;

// int main() {
        // printf("believe me it's %lu == 14 => %s\n", sizeof(i3_ipc_header_t), (sizeof(i3_ipc_header_t) == 14) ? "true" : "false");
// }

pub const Magic1 = "i3-ipc";
pub const I3Header1 = packed struct {
    _magic: [6]u8 = Magic1,
    size: u32 = 0,
    type: u32,
};

pub const Magic2 = "i3-ipc"[0..6].*;
pub const I3Header2 = packed struct {
    _magic: [6]u8 = Magic2,
    size: u32 = 0,
    type: u32,
};

// how do I just remove a sentinel? :P
pub const Magic3 = std.mem.sliceAsBytes("i3-ipc")[0..6].*;
comptime {
    @compileLog(Magic3); // => [6]u8{105,51,45,105,112,99}
}
pub const I3Header3 = packed struct {
    _magic: [6]u8 = Magic3,
    size: u32 = 0,
    type: u32,
};

// what actually worked (:
pub const I3Header4 = packed struct {
    _i: u8 = 'i',
    _3: u8 = '3',
    @"_-": u8 = '-',
    _i2: u8 = 'i',
    _p: u8 = 'p',
    _c: u8 = 'c',
    size: u32 = 0,
    type: u32,
};

test "1: size == 14" {
    try std.testing.expect(@sizeOf(I3Header1) == 14);
}
test "2: size == 14" {
    try std.testing.expect(@sizeOf(I3Header2) == 14);
}
test "3: size == 14" {
    try std.testing.expect(@sizeOf(I3Header3) == 14);
}
test "4: size == 14" {
    try std.testing.expect(@sizeOf(I3Header4) == 14);
}