src/libsyntax/util/rc_slice.rs

// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

use std::fmt;
use std::ops::{Deref, Range};
use std::rc::Rc;

use rustc_data_structures::stable_hasher::{StableHasher, StableHasherResult,
                                           HashStable};

#[derive(Clone)]
pub struct RcSlice<T> {
    data: Rc<Box<[T]>>,
    offset: u32,
    len: u32,
}

impl<T> RcSlice<T> {
    pub fn new(vec: Vec<T>) -> Self {
        RcSlice {
            offset: 0,
            len: vec.len() as u32,
            data: Rc::new(vec.into_boxed_slice()),
        }
    }

    pub fn sub_slice(&self, range: Range<usize>) -> Self {
        RcSlice {
            data: self.data.clone(),
            offset: self.offset + range.start as u32,
            len: (range.end - range.start) as u32,
        }
    }
}

impl<T> Deref for RcSlice<T> {
    type Target = [T];
    fn deref(&self) -> &[T] {
        &self.data[self.offset as usize .. (self.offset + self.len) as usize]
    }
}

impl<T: fmt::Debug> fmt::Debug for RcSlice<T> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        fmt::Debug::fmt(self.deref(), f)
    }
}

impl<CTX, T> HashStable<CTX> for RcSlice<T>
    where T: HashStable<CTX>
{
    fn hash_stable<W: StableHasherResult>(&self,
                                          hcx: &mut CTX,
                                          hasher: &mut StableHasher<W>) {
        (**self).hash_stable(hcx, hasher);
    }
}