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#![allow(unused_variables)] // <1> Silences a warnings caused by `open()` and `close()` not making use of needing their argument
#[derive(Debug)] // <2> This enables `File` to work with `println!` and its `fmt!` sibling macros, used at the bottom of the code listing
struct File {
name: String,
data: Vec<u8>,
}
fn open(f: &mut File) -> bool { // <3> These two functions will remain inert for now
true
}
fn close(f: &mut File) -> bool { // <3>
true
}
fn read(f: &File, save_to: &mut Vec<u8>) -> usize { // <4> Return the "number of bytes read"
let mut tmp = f.data.clone(); // <5> Make a copy of the data here, as `save_to.append()` will shrink the input vec
let read_length = tmp.len();
save_to.reserve(read_length); // <6> Not strictly necessary, but useful to know about
save_to.append(&mut tmp); // <7> Allocate sufficient data in the `save_to` buffer to hold the contents of `f`
read_length
}
fn main() {
let mut f2 = File {
name: String::from("2.txt"),
data: vec![114, 117, 115, 116, 33],
};
let mut buffer: Vec<u8> = vec![];
open(&mut f2); // <8> Do the hard work of interacting the the file.
let f2_length = read(&f2, &mut buffer); // <8>
close(&mut f2); // <8>
let text = String::from_utf8_lossy(&buffer); // <9> Convert `Vec<u8>` to `String`. Any bytes that are not valid UTF-8 are replaced with �
println!("{:?}", f2);
println!("{} is {} bytes long", &f2.name, f2_length);
println!("{}", text) // <10> View [114, 117, 115, 116, 33] as an actual word
}
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