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auto merge of #20143 : csouth3/rust/vecmap-reserve, r=Gankro

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Implement `reserve_len` and `reserve_len_exact` for `VecMap` in accordance with rust-lang/rfcs#509.
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bors 2014-12-27 04:41:53 +00:00
commit 18842f89f0
1 changed files with 46 additions and 0 deletions
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46
src/libcollections/vec_map.rs
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@ -138,6 +138,52 @@ impl<V> VecMap<V> {
self.v.capacity()
}
/// Reserves capacity for the given `VecMap` to contain `len` distinct keys.
/// In the case of `VecMap` this means reallocations will not occur as long
/// as all inserted keys are less than `len`.
///
/// The collection may reserve more space to avoid frequent reallocations.
///
/// # Examples
///
/// ```
/// use std::collections::VecMap;
/// let mut map: VecMap<&str> = VecMap::new();
/// map.reserve_len(10);
/// assert!(map.capacity() >= 10);
/// ```
#[unstable = "matches collection reform specification, waiting for dust to settle"]
pub fn reserve_len(&mut self, len: uint) {
let cur_len = self.v.len();
if len >= cur_len {
self.v.reserve(len - cur_len);
}
}
/// Reserves the minimum capacity for the given `VecMap` to contain `len` distinct keys.
/// In the case of `VecMap` this means reallocations will not occur as long as all inserted
/// keys are less than `len`.
///
/// Note that the allocator may give the collection more space than it requests.
/// Therefore capacity cannot be relied upon to be precisely minimal. Prefer
/// `reserve_len` if future insertions are expected.
///
/// # Examples
///
/// ```
/// use std::collections::VecMap;
/// let mut map: VecMap<&str> = VecMap::new();
/// map.reserve_len_exact(10);
/// assert!(map.capacity() >= 10);
/// ```
#[unstable = "matches collection reform specification, waiting for dust to settle"]
pub fn reserve_len_exact(&mut self, len: uint) {
let cur_len = self.v.len();
if len >= cur_len {
self.v.reserve_exact(len - cur_len);
}
}
/// Returns an iterator visiting all keys in ascending order by the keys.
/// The iterator's element type is `uint`.
#[unstable = "matches collection reform specification, waiting for dust to settle"]