80 lines
2.6 KiB
Rust
80 lines
2.6 KiB
Rust
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// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use owned_slice::OwnedSlice;
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use std::ptr;
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pub trait MoveMap<T>: Sized {
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fn move_map<F>(self, mut f: F) -> Self where F: FnMut(T) -> T {
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self.move_flat_map(|e| Some(f(e)))
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}
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fn move_flat_map<F, I>(self, f: F) -> Self
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where F: FnMut(T) -> I,
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I: IntoIterator<Item=T>;
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}
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impl<T> MoveMap<T> for Vec<T> {
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fn move_flat_map<F, I>(mut self, mut f: F) -> Self
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where F: FnMut(T) -> I,
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I: IntoIterator<Item=T>
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{
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let mut read_i = 0;
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let mut write_i = 0;
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unsafe {
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let mut old_len = self.len();
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self.set_len(0); // make sure we just leak elements in case of panic
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while read_i < old_len {
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// move the read_i'th item out of the vector and map it
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// to an iterator
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let e = ptr::read(self.get_unchecked(read_i));
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let mut iter = f(e).into_iter();
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read_i += 1;
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while let Some(e) = iter.next() {
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if write_i < read_i {
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ptr::write(self.get_unchecked_mut(write_i), e);
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write_i += 1;
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} else {
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// If this is reached we ran out of space
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// in the middle of the vector.
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// However, the vector is in a valid state here,
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// so we just do a somewhat inefficient insert.
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self.set_len(old_len);
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self.insert(write_i, e);
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old_len = self.len();
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self.set_len(0);
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read_i += 1;
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write_i += 1;
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}
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}
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}
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// write_i tracks the number of actually written new items.
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self.set_len(write_i);
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}
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self
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}
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}
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impl<T> MoveMap<T> for OwnedSlice<T> {
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fn move_flat_map<F, I>(self, f: F) -> Self
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where F: FnMut(T) -> I,
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I: IntoIterator<Item=T>
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{
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OwnedSlice::from_vec(self.into_vec().move_flat_map(f))
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}
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}
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