I am trying to write a flexible function that will accept anything that can provide a &[u8] reference — for example, the &[u8], &str and String types.
In the function I need to do things like take a slice, find a length, etc. I'm clearly missing some necessary trait bounds.
The compiler suggests ExactSizeIterator to implement len(), but then changes its mind when I add it. (So fickle!) I also tried adding the bound Index<Range<usize>, Output=T> to get the slice to work, but that also didn't work.
I'm a new to Rust, so any help is appreciated.
use std::fmt::Debug;
//use std::ops::{Index, Range};
//use std::iter::ExactSizeIterator;
fn decode<T>(buf: T)
where T: AsRef<[u8]> + Debug
{
// println!("{:?}", buf); // this works
if buf.len() > 4 {
let subset = buf[2..4];
println!("{:?} {}", subset, subset.len());
}
}
fn main() {
decode(b"byte array");
decode("static string literal");
decode("string".to_string());
}
Errors:
Compiling playground v0.0.1 (/playground)
error[E0599]: no method named `len` found for type parameter `T` in the current scope
--> src/main.rs:10:12
|
6 | fn decode<T>(buf: T)
| - method `len` not found for this type parameter
...
10 | if buf.len() > 4 {
| ^^^ method not found in `T`
|
= help: items from traits can only be used if the type parameter is bounded by the trait
help: the following trait defines an item `len`, perhaps you need to restrict type parameter `T` with it:
|
7 | where T: AsRef<[u8]> + Debug + ExactSizeIterator
| +++++++++++++++++++
error[E0608]: cannot index into a value of type `T`
--> src/main.rs:11:22
|
11 | let subset = buf[2..4];
| ^^^^^^^^^
Some errors have detailed explanations: E0599, E0608.
For more information about an error, try `rustc --explain E0599`.
error: could not compile `playground` due to 2 previous errors