最终代码
源：vec-final.md Commit: f3fb7c9a8f73998aaaab8177562f0c58ff082e37
#![feature(ptr_internals)]
#![feature(allocator_api)]
#![feature(alloc_layout_extra)]
use std::ptr::{Unique, NonNull, self};
use std::mem;
use std::ops::{Deref, DerefMut};
use std::marker::PhantomData;
use std::alloc::{Alloc, GlobalAlloc, Layout, Global, handle_alloc_error};
struct RawVec<T> {
ptr: Unique<T>,
cap: usize,
}
impl<T> RawVec<T> {
fn new() -> Self {
// !0 is usize::MAX. This branch should be stripped at compile time.
let cap = if mem::size_of::<T>() == 0 { !0 } else { 0 };
// Unique::empty() doubles as "unallocated" and "zero-sized allocation"
RawVec { ptr: Unique::empty(), cap: cap }
}
fn grow(&mut self) {
unsafe {
let elem_size = mem::size_of::<T>();
// since we set the capacity to usize::MAX when elem_size is
// 0, getting to here necessarily means the Vec is overfull.
assert!(elem_size != 0, "capacity overflow");
let (new_cap, ptr) = if self.cap == 0 {
let ptr = Global.alloc(Layout::array::<T>(1).unwrap());
(1, ptr)
} else {
let new_cap = 2 * self.cap;
let c: NonNull<T> = self.ptr.into();
let ptr = Global.realloc(c.cast(),
Layout::array::<T>(self.cap).unwrap(),
Layout::array::<T>(new_cap).unwrap().size());
(new_cap, ptr)
};
// If allocate or reallocate fail, oom
if ptr.is_err() {
handle_alloc_error(Layout::from_size_align_unchecked(
new_cap * elem_size,
mem::align_of::<T>(),
))
}
let ptr = ptr.unwrap();
self.ptr = Unique::new_unchecked(ptr.as_ptr() as *mut _);
self.cap = new_cap;
}
}
}
impl<T> Drop for RawVec<T> {
fn drop(&mut self) {
let elem_size = mem::size_of::<T>();
if self.cap != 0 && elem_size != 0 {
unsafe {
let c: NonNull<T> = self.ptr.into();
Global.dealloc(c.cast(),
Layout::array::<T>(self.cap).unwrap());
}
}
}
}
pub struct Vec<T> {
buf: RawVec<T>,
len: usize,
}
impl<T> Vec<T> {
fn ptr(&self) -> *mut T { self.buf.ptr.as_ptr() }
fn cap(&self) -> usize { self.buf.cap }
pub fn new() -> Self {
Vec { buf: RawVec::new(), len: 0 }
}
pub fn push(&mut self, elem: T) {
if self.len == self.cap() { self.buf.grow(); }
unsafe {
ptr::write(self.ptr().offset(self.len as isize), elem);
}
// Can't fail, we'll OOM first.
self.len += 1;
}
pub fn pop(&mut self) -> Option<T> {
if self.len == 0 {
None
} else {
self.len -= 1;
unsafe {
Some(ptr::read(self.ptr().offset(self.len as isize)))
}
}
}
pub fn insert(&mut self, index: usize, elem: T) {
assert!(index <= self.len, "index out of bounds");
if self.cap() == self.len { self.buf.grow(); }
unsafe {
if index < self.len {
ptr::copy(self.ptr().offset(index as isize),
self.ptr().offset(index as isize + 1),
self.len - index);
}
ptr::write(self.ptr().offset(index as isize), elem);
self.len += 1;
}
}
pub fn remove(&mut self, index: usize) -> T {
assert!(index < self.len, "index out of bounds");
unsafe {
self.len -= 1;
let result = ptr::read(self.ptr().offset(index as isize));
ptr::copy(self.ptr().offset(index as isize + 1),
self.ptr().offset(index as isize),
self.len - index);
result
}
}
pub fn into_iter(self) -> IntoIter<T> {
unsafe {
let iter = RawValIter::new(&self);
let buf = ptr::read(&self.buf);
mem::forget(self);
IntoIter {
iter: iter,
_buf: buf,
}
}
}
pub fn drain(&mut self) -> Drain<T> {
unsafe {
let iter = RawValIter::new(&self);
// this is a mem::forget safety thing. If Drain is forgotten, we just
// leak the whole Vec's contents. Also we need to do this *eventually*
// anyway, so why not do it now?
self.len = 0;
Drain {
iter: iter,
vec: PhantomData,
}
}
}
}
impl<T> Drop for Vec<T> {
fn drop(&mut self) {
while let Some(_) = self.pop() {}
// allocation is handled by RawVec
}
}
impl<T> Deref for Vec<T> {
type Target = [T];
fn deref(&self) -> &[T] {
unsafe {
::std::slice::from_raw_parts(self.ptr(), self.len)
}
}
}
impl<T> DerefMut for Vec<T> {
fn deref_mut(&mut self) -> &mut [T] {
unsafe {
::std::slice::from_raw_parts_mut(self.ptr(), self.len)
}
}
}
struct RawValIter<T> {
start: *const T,
end: *const T,
}
impl<T> RawValIter<T> {
unsafe fn new(slice: &[T]) -> Self {
RawValIter {
start: slice.as_ptr(),
end: if mem::size_of::<T>() == 0 {
((slice.as_ptr() as usize) + slice.len()) as *const _
} else if slice.len() == 0 {
slice.as_ptr()
} else {
slice.as_ptr().offset(slice.len() as isize)
}
}
}
}
impl<T> Iterator for RawValIter<T> {
type Item = T;
fn next(&mut self) -> Option<T> {
if self.start == self.end {
None
} else {
unsafe {
let result = ptr::read(self.start);
self.start = if mem::size_of::<T>() == 0 {
(self.start as usize + 1) as *const _
} else {
self.start.offset(1)
};
Some(result)
}
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
let elem_size = mem::size_of::<T>();
let len = (self.end as usize - self.start as usize)
/ if elem_size == 0 { 1 } else { elem_size };
(len, Some(len))
}
}
impl<T> DoubleEndedIterator for RawValIter<T> {
fn next_back(&mut self) -> Option<T> {
if self.start == self.end {
None
} else {
unsafe {
self.end = if mem::size_of::<T>() == 0 {
(self.end as usize - 1) as *const _
} else {
self.end.offset(-1)
};
Some(ptr::read(self.end))
}
}
}
}
pub struct IntoIter<T> {
_buf: RawVec<T>, // we don't actually care about this. Just need it to live.
iter: RawValIter<T>,
}
impl<T> Iterator for IntoIter<T> {
type Item = T;
fn next(&mut self) -> Option<T> { self.iter.next() }
fn size_hint(&self) -> (usize, Option<usize>) { self.iter.size_hint() }
}
impl<T> DoubleEndedIterator for IntoIter<T> {
fn next_back(&mut self) -> Option<T> { self.iter.next_back() }
}
impl<T> Drop for IntoIter<T> {
fn drop(&mut self) {
for _ in &mut *self {}
}
}
pub struct Drain<'a, T: 'a> {
vec: PhantomData<&'a mut Vec<T>>,
iter: RawValIter<T>,
}
impl<'a, T> Iterator for Drain<'a, T> {
type Item = T;
fn next(&mut self) -> Option<T> { self.iter.next() }
fn size_hint(&self) -> (usize, Option<usize>) { self.iter.size_hint() }
}
impl<'a, T> DoubleEndedIterator for Drain<'a, T> {
fn next_back(&mut self) -> Option<T> { self.iter.next_back() }
}
impl<'a, T> Drop for Drain<'a, T> {
fn drop(&mut self) {
// pre-drain the iter
for _ in &mut self.iter {}
}
}
# fn main() {
# tests::create_push_pop();
# tests::iter_test();
# tests::test_drain();
# tests::test_zst();
# println!("All tests finished OK");
# }
# mod tests {
# use super::*;
# pub fn create_push_pop() {
# let mut v = Vec::new();
# v.push(1);
# assert_eq!(1, v.len());
# assert_eq!(1, v[0]);
# for i in v.iter_mut() {
# *i += 1;
# }
# v.insert(0, 5);
# let x = v.pop();
# assert_eq!(Some(2), x);
# assert_eq!(1, v.len());
# v.push(10);
# let x = v.remove(0);
# assert_eq!(5, x);
# assert_eq!(1, v.len());
# }
#
# pub fn iter_test() {
# let mut v = Vec::new();
# for i in 0..10 {
# v.push(Box::new(i))
# }
# let mut iter = v.into_iter();
# let first = iter.next().unwrap();
# let last = iter.next_back().unwrap();
# drop(iter);
# assert_eq!(0, *first);
# assert_eq!(9, *last);
# }
#
# pub fn test_drain() {
# let mut v = Vec::new();
# for i in 0..10 {
# v.push(Box::new(i))
# }
# {
# let mut drain = v.drain();
# let first = drain.next().unwrap();
# let last = drain.next_back().unwrap();
# assert_eq!(0, *first);
# assert_eq!(9, *last);
# }
# assert_eq!(0, v.len());
# v.push(Box::new(1));
# assert_eq!(1, *v.pop().unwrap());
# }
#
# pub fn test_zst() {
# let mut v = Vec::new();
# for _i in 0..10 {
# v.push(())
# }
#
# let mut count = 0;
#
# for _ in v.into_iter() {
# count += 1
# }
#
# assert_eq!(10, count);
# }
# }