| use std::ptr; |
| use smallvec::{Array, SmallVec}; |
| |
| pub trait MapInPlace<T>: Sized { |
| fn map_in_place<F>(&mut self, mut f: F) where F: FnMut(T) -> T { |
| self.flat_map_in_place(|e| Some(f(e))) |
| } |
| |
| fn flat_map_in_place<F, I>(&mut self, f: F) |
| where F: FnMut(T) -> I, |
| I: IntoIterator<Item=T>; |
| } |
| |
| impl<T> MapInPlace<T> for Vec<T> { |
| fn flat_map_in_place<F, I>(&mut self, mut f: F) |
| where F: FnMut(T) -> I, |
| I: IntoIterator<Item=T> |
| { |
| let mut read_i = 0; |
| let mut write_i = 0; |
| unsafe { |
| let mut old_len = self.len(); |
| self.set_len(0); // make sure we just leak elements in case of panic |
| |
| while read_i < old_len { |
| // move the read_i'th item out of the vector and map it |
| // to an iterator |
| let e = ptr::read(self.get_unchecked(read_i)); |
| let iter = f(e).into_iter(); |
| read_i += 1; |
| |
| for e in iter { |
| if write_i < read_i { |
| ptr::write(self.get_unchecked_mut(write_i), e); |
| write_i += 1; |
| } else { |
| // If this is reached we ran out of space |
| // in the middle of the vector. |
| // However, the vector is in a valid state here, |
| // so we just do a somewhat inefficient insert. |
| self.set_len(old_len); |
| self.insert(write_i, e); |
| |
| old_len = self.len(); |
| self.set_len(0); |
| |
| read_i += 1; |
| write_i += 1; |
| } |
| } |
| } |
| |
| // write_i tracks the number of actually written new items. |
| self.set_len(write_i); |
| } |
| } |
| } |
| |
| impl<T, A: Array<Item = T>> MapInPlace<T> for SmallVec<A> { |
| fn flat_map_in_place<F, I>(&mut self, mut f: F) |
| where F: FnMut(T) -> I, |
| I: IntoIterator<Item=T> |
| { |
| let mut read_i = 0; |
| let mut write_i = 0; |
| unsafe { |
| let mut old_len = self.len(); |
| self.set_len(0); // make sure we just leak elements in case of panic |
| |
| while read_i < old_len { |
| // move the read_i'th item out of the vector and map it |
| // to an iterator |
| let e = ptr::read(self.get_unchecked(read_i)); |
| let iter = f(e).into_iter(); |
| read_i += 1; |
| |
| for e in iter { |
| if write_i < read_i { |
| ptr::write(self.get_unchecked_mut(write_i), e); |
| write_i += 1; |
| } else { |
| // If this is reached we ran out of space |
| // in the middle of the vector. |
| // However, the vector is in a valid state here, |
| // so we just do a somewhat inefficient insert. |
| self.set_len(old_len); |
| self.insert(write_i, e); |
| |
| old_len = self.len(); |
| self.set_len(0); |
| |
| read_i += 1; |
| write_i += 1; |
| } |
| } |
| } |
| |
| // write_i tracks the number of actually written new items. |
| self.set_len(write_i); |
| } |
| } |
| } |