rust - How can I force a value to be moved from an inner scope to an outer instead of borrowing? -

i'm newbie in rust. how can force value moved inner scope outer instead of borrowing?

let mut r_buf = bufreader::new(file.unwrap()); let mut eof = false;  while !eof {     let piece = r_buf.fill_buf();     if piece.is_ok() {         let mut piece = piece.unwrap();         let piece_len = piece.len();          if opt.compress {             let deflated = deflate_bytes(piece);             if deflated.is_none() {                 panic!(format!("cant deflate file {}", path.to_str().unwrap_or("")));             }              let deflate_unwrapped = deflated.unwrap();             let deflate_deref = deflate_unwrapped.deref();             piece = deflate_deref;         }         /* bf: &mut bufstream<file>*/         let w = bf.write(piece);          if w.is_ok() {             written_bytes = w.unwrap();         } 

i can't move &[u8] deflate_deref piece. i've tried vec<u8> , box<&[u8]>. have error "deflate_unwrapped not live long enough"... can't operate [u8] type because doesn't have exact size in compile type, while references can borrow...

in case must use specific or rewrite code?

playground link http://is.gd/u8wfm7

let’s reduce code minimal example:

fn main() {     let = {         let b = 42;         &b     }; } 

for case boiling down to: trying take reference , storing reference after original object has passed out of scope.

there 2 main ways of dealing this:

1. change scope of variable taking reference to:

   fn main() {     let b;     let = {         b = 42;         &b     }; } 

   so long not dealing crossing function boundaries (that is, returning reference inside function) or combinations loop boundaries, typically best solution.

2. don’t take reference, rather processing wish @ time:

   fn main() {     let = {         let b = 42;         b.clone()     }; } 

   in particular case, turning &[u8] vec<u8>, can written vec::from(slice). of course, in specific example still need worry storing vector somewhere in first way, or else using cow<[u8]> whole thing.

there article have written among other things considers these questions might find helpful: http://chrismorgan.info/blog/rust-fizzbuzz.html. deals string , str dealing more vec<u8>/bytes , [u8], concepts same.