1. Open the Cargo.toml file that was generated earlier for you.

2. Under [dependencies], add the following lines:

bitflags = "1.0"

3. If you want, you can go to bitflags' crates.io page (https://crates.io/crates/bitflags) to check for the newest version and use that one instead.

4. In the bin folder, create a file called bit_fields.rs.

5. Add the following code and run it with cargo run --bin bit_fields:

1    #[macro_use]
2    extern crate bitflags;
3 
4    bitflags! {
5      struct Spices: u32 {
6        const SALT    = 0b0000_0001;
7        const PEPPER  = 0b0000_0010;
8        const CHILI   = 0b0000_0100;
9        const SAFFRON = 0b0000_1000;
10       const ALL     = Self::SALT.bits
11                     | Self::PEPPER.bits
12                     | Self::CHILI.bits
13                     | Self::SAFFRON.bits;
14     }
15   }
16 
17   impl Spices {
18     // Implementing a "clear" method can be useful
19     pub fn clear(&mut self) -> &mut Self {
20       self.bits = 0;
21       self
22     }
23   }
24 
25   fn main() {
26     let classic = Spices::SALT | Spices::PEPPER;
27     let spicy = Spices::PEPPER | Spices::CHILI;
28     // Bit fields can nicely be printed
29     println!("Classic: {:?}", classic);
30     println!("Bits: {:08b}", classic.bits());
31     println!("Spicy: {:?}", spicy);
32     println!("Bits: {:08b}", spicy.bits());
33 
34     println!();
35 
36     // Use set operations
37     println!("Union: {:?}", classic | spicy);
38     println!("Intersection: {:?}", classic & spicy);
39     println!("Difference: {:?}", classic - spicy);
40     println!("Complement: {:?}", !classic);
41 
42     // Interact with flags in a bit field
43     let mut custom = classic | spicy;
44     println!("Custom spice mix: {:?}", custom);
45     custom.insert(Spices::SAFFRON);
46     // Note that ALL is now also contained in the bit field
47     println!("Custom spice after adding saffron: {:?}", custom);
48     custom.toggle(Spices::CHILI);
49     println!("Custom spice after toggling chili: {:?}", custom);
50     custom.remove(Spices::SALT);
51     println!("Custom spice after removing salt: {:?}", custom);
52 
53     // This could be user input
54     let wants_salt = true;
55     custom.set(Spices::SALT, wants_salt);
56     if custom.contains(Spices::SALT) {
57       println!("I hope I didn't put too much salt in it");
58     }
59 
60     // Read flags from raw bits
61     let bits = 0b0000_1101;
62     if let Some(from_bits) = Spices::from_bits(bits) {
63       println!("The bits {:08b} represent the flags {:?}", bits,
         from_bits);
64     }
65 
66     custom.clear();
67     println!("Custom spice mix after clearing: {:?}", custom);
68   }