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implement ZST and add update final code

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pull/182/head
Clifton King 6 years ago
parent 84179ba915
commit fac31bc0c9
2 changed files with 241 additions and 112 deletions
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302
src/vec-final.md
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@ -1,15 +1,14 @@
# The Final Code
```rust
#![feature(ptr_internals)]
#![feature(allocator_api)]
#![feature(alloc_layout_extra)]
#![feature(ptr_internals)] // std::ptr::Unique
#![feature(alloc_internals)] // std::alloc::*
use std::ptr::{Unique, NonNull, self};
use std::mem;
use std::ops::{Deref, DerefMut};
use std::alloc::{alloc, realloc, Layout, dealloc, rust_oom};
use std::marker::PhantomData;
use std::alloc::{Alloc, GlobalAlloc, Layout, Global, handle_alloc_error};
use std::ptr::{self, Unique};
struct RawVec<T> {
ptr: Unique<T>,
@ -18,11 +17,9 @@ struct RawVec<T> {
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 };
let cap = if mem::size_of::<T>() == 0 { ::std::usize::MAX } else { 0 };
// Unique::empty() doubles as "unallocated" and "zero-sized allocation"
RawVec { ptr: Unique::empty(), cap: cap }
RawVec { ptr: Unique::empty(), cap, }
}
fn grow(&mut self) {
@ -33,28 +30,34 @@ impl<T> RawVec<T> {
// 0, getting to here necessarily means the Vec is overfull.
assert!(elem_size != 0, "capacity overflow");
let align = mem::align_of::<T>();
let (new_cap, ptr) = if self.cap == 0 {
let ptr = Global.alloc(Layout::array::<T>(1).unwrap());
let layout = Layout::from_size_align_unchecked(elem_size, align);
let ptr = alloc(layout);
(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());
let new_cap = self.cap * 2;
let old_num_bytes = self.cap * elem_size;
assert!(
old_num_bytes <= (::std::isize::MAX as usize) / 2,
"Capacity overflow!"
);
let num_new_bytes = old_num_bytes * 2;
let layout = Layout::from_size_align_unchecked(old_num_bytes, align);
let ptr = realloc(self.ptr.as_ptr() as *mut _, layout, num_new_bytes);
(new_cap, ptr)
};
// If allocate or reallocate fail, oom
if ptr.is_err() {
handle_alloc_error(Layout::from_size_align_unchecked(
// If allocate or reallocate fail, we'll get `null` back
if ptr.is_null() {
rust_oom(Layout::from_size_align_unchecked(
new_cap * elem_size,
mem::align_of::<T>(),
))
align,
));
}
let ptr = ptr.unwrap();
self.ptr = Unique::new_unchecked(ptr.as_ptr() as *mut _);
self.ptr = Unique::new(ptr as *mut _).unwrap();
self.cap = new_cap;
}
}
@ -62,38 +65,47 @@ impl<T> RawVec<T> {
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());
if self.cap != 0 {
let elem_size = mem::size_of::<T>();
// don't free zero-sized allocations, as they were never allocated.
if self.cap != 0 && elem_size != 0 {
let align = mem::align_of::<T>();
let num_bytes = elem_size * self.cap;
unsafe {
let layout = Layout::from_size_align_unchecked(num_bytes, align);
dealloc(self.ptr.as_ptr() as *mut _, layout);
}
}
}
}
}
pub struct Vec<T> {
pub struct NomVec<T> {
buf: RawVec<T>,
len: usize,
}
impl<T> Vec<T> {
fn ptr(&self) -> *mut T { self.buf.ptr.as_ptr() }
impl<T> NomVec<T> {
fn ptr(&self) -> *mut T {
self.buf.ptr.as_ptr()
}
fn cap(&self) -> usize { self.buf.cap }
fn cap(&self) -> usize {
self.buf.cap
}
pub fn new() -> Self {
Vec { buf: RawVec::new(), len: 0 }
Self { 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;
}
@ -108,15 +120,21 @@ impl<T> Vec<T> {
}
}
pub fn len(&self) -> usize {
self.len
}
pub fn insert(&mut self, index: usize, elem: T) {
// Note: `<=` because it's valid to insert after everything
// which would be equivalent to push.
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);
self.len - index
);
}
ptr::write(self.ptr().offset(index as isize), elem);
self.len += 1;
@ -135,44 +153,38 @@ impl<T> Vec<T> {
}
}
pub fn into_iter(self) -> IntoIter<T> {
#[allow(dead_code)]
fn into_iter(self) -> IntoIter<T> {
unsafe {
// need to use ptr::read to unsafely move the buf out since it's
// not Copy, and Vec implements Drop (so we can't destructure it).
let iter = RawValIter::new(&self);
let buf = ptr::read(&self.buf);
mem::forget(self);
IntoIter {
iter: iter,
_buf: buf,
}
IntoIter { 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,
}
Drain { iter, vec: PhantomData, }
}
}
}
impl<T> Drop for Vec<T> {
impl<T> Drop for NomVec<T> {
fn drop(&mut self) {
// deallocation is handled by RawVec
while let Some(_) = self.pop() {}
// allocation is handled by RawVec
}
}
impl<T> Deref for Vec<T> {
impl<T> Deref for NomVec<T> {
type Target = [T];
fn deref(&self) -> &[T] {
unsafe {
@ -181,7 +193,7 @@ impl<T> Deref for Vec<T> {
}
}
impl<T> DerefMut for Vec<T> {
impl<T> DerefMut for NomVec<T> {
fn deref_mut(&mut self) -> &mut [T] {
unsafe {
::std::slice::from_raw_parts_mut(self.ptr(), self.len)
@ -191,6 +203,30 @@ impl<T> DerefMut for Vec<T> {
struct IntoIter<T> {
_buf: RawVec<T>,
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) {
// only need to ensure all our elements are read;
// buffer will clean itself up afterwards.
for _ in &mut self.iter {}
}
}
struct RawValIter<T> {
@ -199,12 +235,17 @@ struct RawValIter<T> {
}
impl<T> RawValIter<T> {
// unsafe to construct because it has no associated lifetimes.
// This is necessary to store a RawValIter in the same struct as
// its actual allocation. OK since it's a private implementation
// detail.
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 {
end: if slice.len() == 0 {
// if `len = 0`, then this is not actually allocated memory.
// Need to avoid offsetting because that will give wrong
// information to LLVM via GEP.
slice.as_ptr()
} else {
slice.as_ptr().offset(slice.len() as isize)
@ -232,9 +273,7 @@ impl<T> Iterator for RawValIter<T> {
}
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 };
let len = (self.end as usize - self.start as usize) / mem::size_of::<T>();
(len, Some(len))
}
}
@ -245,11 +284,7 @@ impl<T> DoubleEndedIterator for RawValIter<T> {
None
} else {
unsafe {
self.end = if mem::size_of::<T>() == 0 {
(self.end as usize - 1) as *const _
} else {
self.end.offset(-1)
};
self.end = self.end.offset(-1);
Some(ptr::read(self.end))
}
}
@ -258,50 +293,133 @@ impl<T> DoubleEndedIterator for RawValIter<T> {
pub struct IntoIter<T> {
_buf: RawVec<T>, // we don't actually care about this. Just need it to live.
pub struct Drain<'a, T: 'a> {
// Need to bound the lifetime here, so we do it with `&'a mut Vec<T>`
// because that's semantically what we contain. We're "just" calling
// `pop()` and `remove(0)`.
vec: PhantomData<&'a mut NomVec<T>>,
iter: RawValIter<T>,
}
impl<T> Iterator for IntoIter<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<T> DoubleEndedIterator for IntoIter<T> {
impl<'a, T> DoubleEndedIterator for Drain<'a, T> {
fn next_back(&mut self) -> Option<T> { self.iter.next_back() }
}
impl<T> Drop for IntoIter<T> {
impl<'a, T> Drop for Drain<'a, T> {
fn drop(&mut self) {
for _ in &mut *self {}
for _ in &mut self.iter {}
}
}
#[cfg(test)]
mod tests {
use super::*;
pub struct Drain<'a, T: 'a> {
vec: PhantomData<&'a mut Vec<T>>,
iter: RawValIter<T>,
}
#[test]
fn vec_push() {
let mut cv = NomVec::new();
cv.push(2);
assert_eq!(cv.len(), 1);
cv.push(3);
assert_eq!(cv.len(), 2);
}
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() }
}
#[test]
fn vec_iter() {
let mut cv = NomVec::new();
cv.push(2);
cv.push(3);
let mut accum = 0;
for x in cv.iter() {
accum += x;
}
assert_eq!(accum, 5);
}
impl<'a, T> DoubleEndedIterator for Drain<'a, T> {
fn next_back(&mut self) -> Option<T> { self.iter.next_back() }
}
#[test]
fn vec_into_iter() {
let mut cv = NomVec::new();
cv.push(2);
cv.push(3);
assert_eq!(cv.into_iter().collect::<Vec<i32>>(), vec![2, 3]);
}
impl<'a, T> Drop for Drain<'a, T> {
fn drop(&mut self) {
// pre-drain the iter
for _ in &mut self.iter {}
#[test]
fn vec_into_double_ended_iter() {
let mut cv = NomVec::new();
cv.push(2);
cv.push(3);
assert_eq!(*cv.iter().next_back().unwrap(), 3);
}
#[test]
fn vec_pop() {
let mut cv = NomVec::new();
cv.push(2);
assert_eq!(cv.len(), 1);
cv.pop();
assert_eq!(cv.len(), 0);
assert!(cv.pop() == None);
}
#[test]
fn vec_insert() {
let mut cv: NomVec<i32> = NomVec::new();
cv.insert(0, 2); // test insert at end
cv.insert(0, 1); // test insert at beginning
assert_eq!(cv.pop().unwrap(), 2);
}
#[test]
fn vec_remove() {
let mut cv = NomVec::new();
cv.push(2);
assert_eq!(cv.remove(0), 2);
assert_eq!(cv.len(), 0);
}
#[test]
#[should_panic(expected = "index out of bounds")]
fn vec_cant_remove() {
let mut cv: NomVec<i32> = NomVec::new();
cv.remove(0);
}
#[test]
fn vec_drain() {
let mut cv = NomVec::new();
cv.push(1);
cv.push(2);
cv.push(3);
assert_eq!(cv.len(), 3);
{
let mut drain = cv.drain();
assert_eq!(drain.next().unwrap(), 1);
assert_eq!(drain.next_back().unwrap(), 3);
}
assert_eq!(cv.len(), 0);
}
#[derive(PartialEq, Debug)]
struct ZST;
#[test]
fn vec_zst() {
let mut cv = NomVec::new();
cv.push(ZST {});
cv.push(ZST {});
assert_eq!(cv.len(), 2);
assert_eq!(cv.pop().unwrap(), ZST {});
assert_eq!(cv.pop().unwrap(), ZST {});
assert_eq!(cv.pop(), None);
}
}
@ -316,7 +434,7 @@ impl<'a, T> Drop for Drain<'a, T> {
# mod tests {
# use super::*;
# pub fn create_push_pop() {
# let mut v = Vec::new();
# let mut v = NomVec::new();
# v.push(1);
# assert_eq!(1, v.len());
# assert_eq!(1, v[0]);
@ -334,7 +452,7 @@ impl<'a, T> Drop for Drain<'a, T> {
# }
#
# pub fn iter_test() {
# let mut v = Vec::new();
# let mut v = NomVec::new();
# for i in 0..10 {
# v.push(Box::new(i))
# }
@ -347,7 +465,7 @@ impl<'a, T> Drop for Drain<'a, T> {
# }
#
# pub fn test_drain() {
# let mut v = Vec::new();
# let mut v = NomVec::new();
# for i in 0..10 {
# v.push(Box::new(i))
# }
@ -364,7 +482,7 @@ impl<'a, T> Drop for Drain<'a, T> {
# }
#
# pub fn test_zst() {
# let mut v = Vec::new();
# let mut v = NomVec::new();
# for _i in 0..10 {
# v.push(())
# }

51
src/vec-zsts.md
Unescape View File

@ -35,13 +35,12 @@ method of RawVec.
```rust,ignore
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 };
let cap = if mem::size_of::<T>() == 0 { ::std::usize::MAX } else { 0 };
// Unique::empty() doubles as "unallocated" and "zero-sized allocation"
RawVec { ptr: Unique::empty(), cap: cap }
RawVec { ptr: Unique::empty(), cap, }
}
// unchanged from Vec
fn grow(&mut self) {
unsafe {
let elem_size = mem::size_of::<T>();
@ -53,21 +52,31 @@ impl<T> RawVec<T> {
let align = mem::align_of::<T>();
let (new_cap, ptr) = if self.cap == 0 {
let ptr = heap::allocate(elem_size, align);
let layout = Layout::from_size_align_unchecked(elem_size, align);
let ptr = alloc(layout);
(1, ptr)
} else {
let new_cap = 2 * self.cap;
let ptr = heap::reallocate(self.ptr.as_ptr() as *mut _,
self.cap * elem_size,
new_cap * elem_size,
align);
let new_cap = self.cap * 2;
let old_num_bytes = self.cap * elem_size;
assert!(
old_num_bytes <= (::std::isize::MAX as usize) / 2,
"Capacity overflow!"
);
let num_new_bytes = old_num_bytes * 2;
let layout = Layout::from_size_align_unchecked(old_num_bytes, align);
let ptr = realloc(self.ptr.as_ptr() as *mut _, layout, num_new_bytes);
(new_cap, ptr)
};
// If allocate or reallocate fail, we'll get `null` back
if ptr.is_null() { oom() }
if ptr.is_null() {
rust_oom(Layout::from_size_align_unchecked(
new_cap * elem_size,
align,
));
}
self.ptr = Unique::new(ptr as *mut _);
self.ptr = Unique::new(ptr as *mut _).unwrap();
self.cap = new_cap;
}
}
@ -75,15 +84,17 @@ impl<T> RawVec<T> {
impl<T> Drop for RawVec<T> {
fn drop(&mut self) {
let elem_size = mem::size_of::<T>();
// don't free zero-sized allocations, as they were never allocated.
if self.cap != 0 && elem_size != 0 {
let align = mem::align_of::<T>();
if self.cap != 0 {
let elem_size = mem::size_of::<T>();
let num_bytes = elem_size * self.cap;
unsafe {
heap::deallocate(self.ptr.as_ptr() as *mut _, num_bytes, align);
// don't free zero-sized allocations, as they were never allocated.
if self.cap != 0 && elem_size != 0 {
let align = mem::align_of::<T>();
let num_bytes = elem_size * self.cap;
unsafe {
let layout = Layout::from_size_align_unchecked(num_bytes, align);
dealloc(self.ptr.as_ptr() as *mut _, layout);
}
}
}
}

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