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Link if let and shadowing chapters under keyboard code

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Philipp Oppermann
2019-04-15 14:10:34 +02:00
parent 0b9ca84735
commit ac16f2ed55
1 changed files with 7 additions and 1 deletions
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8
blog/content/second-edition/posts/08-hardware-interrupts/index.md
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@@ -576,7 +576,13 @@ extern "x86-interrupt" fn keyboard_interrupt_handler(
}
```
The above code just translates keypresses of the number keys 0-9 and ignores all other keys. Now we can write numbers:
The above code translates keypresses of the number keys 0-9 and ignores all other keys. It uses a [match] statement to assign a character or `None` to each scancode. It then uses [`if let`] to destructure the optional `key`. By using the same variable name `key` in the pattern, we [shadow] the previous declaration, which is a common pattern for destructuring `Option` types in Rust.
[match]: https://doc.rust-lang.org/book/ch06-02-match.html
[`if let`]: https://doc.rust-lang.org/book/ch18-01-all-the-places-for-patterns.html#conditional-if-let-expressions
[shadow]: https://doc.rust-lang.org/book/ch03-01-variables-and-mutability.html#shadowing
Now we can write numbers:
![QEMU printing numbers to the screen](qemu-printing-numbers.gif)