Computer Enhance Part 1 in Zig

main.zig

// I am a complete Zig noob so please be kind!

const std = @import("std");

pub fn getName(addr: u8, w: bool, dest: []u8) void {
    if (w) {
        std.mem.copy(u8, dest, switch (addr) {
            0b00_000_000 => "ax",
            0b00_000_001 => "cx",
            0b00_000_010 => "dx",
            0b00_000_011 => "bx",
            0b00_000_100 => "sp",
            0b00_000_101 => "bp",
            0b00_000_110 => "si",
            0b00_000_111 => "di",
            else => unreachable,
        });
    } else {
        std.mem.copy(u8, dest, switch (addr) {
            0b00_000_000 => "al",
            0b00_000_001 => "cl",
            0b00_000_010 => "dl",
            0b00_000_011 => "bl",
            0b00_000_100 => "ah",
            0b00_000_101 => "ch",
            0b00_000_110 => "dh",
            0b00_000_111 => "bh",
            else => unreachable,
        });
    }
}

pub fn main() !void {
    var file = try std.fs.cwd().openFile("listing_0038_many_register_mov", .{});
    defer file.close();

    var buf_reader = std.io.bufferedReader(file.reader());
    var in_stream = buf_reader.reader();

    var buf: [2]u8 = undefined;
    while (try in_stream.read(&buf) > 0) {
        //std.debug.print("{b} {b}\n", .{ buf[0], buf[1] });
        var instr = [_]u8{ 0, 0, 0 };
        std.mem.copy(u8, &instr, switch (buf[0] & 0b111111_0_0) {
            0b100010_00 => "mov",
            else => unreachable,
        });
        var d: bool = buf[0] & 0b000000_1_0 > 0;
        var w: bool = buf[0] & 0b000000_0_1 > 0;
        //var mod: u8 = buf[1] & 0b11_000_000;
        var pos1: u8 = (buf[1] & 0b00_111_000) >> 3;
        var pos2: u8 = buf[1] & 0b00_000_111;

        // if d, pos1 is the source and pos2 is the destination
        var name1 = [_]u8{ 0, 0 };
        var name2 = [_]u8{ 0, 0 };
        getName(if (d) pos1 else pos2, w, &name1);
        getName(if (d) pos2 else pos1, w, &name2);
        
        // I was too lazy to figure out how to write to a file in zig
        std.debug.print("{s} {s}, {s}\n", .{ instr, name1, name2 });
    }
}