hash.rs

//this works
fn hash(data: &[u8], key: &[u8]) {
	let mut hmac = Hmac::new(Sha1::new(), key);
	hmac.input(data);

	let signature = &hmac.result().code().to_base64(B64_STD);
	println!("sig:\n{}", signature);
}

//this does not work (compiler error in next file)
fn hash(data: &[u8], key: &[u8]) {
	let mut hmac = Hmac::new(Sha1::new(), key);
	hmac.input(data);

	let result = hmac.result().code();
	let signature = &result.to_base64(B64_STD);
	println!("sig:\n{}", signature);
}

//but this works
fn hash(data: &[u8], key: &[u8]) {
	let mut hmac = Hmac::new(Sha1::new(), key);
	hmac.input(data);

	let result = hmac.result();
	let code = result.code();
	let signature = &code.to_base64(B64_STD);
	println!("sig:\n{}", signature);
}

//this doesn't work (same error, on `result.code()`)
fn hash<'a>(data: &[u8], key: &[u8]) -> &'a [u8] {
	let mut hmac = Hmac::new(Sha1::new(), key);
	hmac.input(data);

	let result = hmac.result();
	let code = result.code();
	
	code
}

//my ultimate goal is something along these lines
//with `let bytes = hash(foo, bar);` in the calling function taking ownership
fn hash<'a>(data: &[u8], key: &[u8]) -> &'a [u8] {
	let mut hmac = Hmac::new(Sha1::new(), key);
	hmac.input(data);

	&hmac.result().code()
}

rustc-err

src/main.rs:48:15: 48:28 error: borrowed value does not live long enough
src/main.rs:48 	let result = hmac.result().code();
               	             ^~~~~~~~~~~~~
src/main.rs:48:36: 51:2 note: reference must be valid for the block suffix following statement 2 at 48:35...
src/main.rs:48 	let result = hmac.result().code();
src/main.rs:49 	let signature = &result.to_base64(B64_STD);
src/main.rs:50 	println!("sig:\n{}", signature);
src/main.rs:51 }
src/main.rs:48:2: 48:36 note: ...but borrowed value is only valid for the statement at 48:1
src/main.rs:48 	let result = hmac.result().code();
               	^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/main.rs:48:2: 48:36 help: consider using a `let` binding to increase its lifetime
src/main.rs:48 	let result = hmac.result().code();
               	^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~