Skip to content

Instantly share code, notes, and snippets.

@ca7023

ca7023/vec.rs

Created November 7, 2018 10:30
Show Gist options
  • Save ca7023/4c7527b2cc78c695da1091fbf7f340bb to your computer and use it in GitHub Desktop.
Save ca7023/4c7527b2cc78c695da1091fbf7f340bb to your computer and use it in GitHub Desktop.
Download ZIP
Toy Vec
Raw
vec.rs
#![feature(ptr_internals, alloc)]
use std::ops::{Deref, DerefMut};
use std::ptr::{self, Unique};
use std::{alloc, marker::PhantomData, mem};
struct RawVec<T> {
ptr: Unique<T>,
cap: usize,
}
impl<T> RawVec<T> {
pub fn new() -> Self {
let cap = [0, !0][(mem::size_of::<T>() == 0) as usize];
RawVec {
ptr: Unique::empty(),
cap,
}
}
fn grow(&mut self) {
unsafe {
let elem_size = mem::size_of::<T>();
assert!(elem_size != 0, "capacity overflow");
let align = mem::align_of::<T>();
let layout = alloc::Layout::new::<T>();
let (cap, ptr) = if self.cap == 0 {
let ptr = alloc::alloc(layout);
if ptr.is_null() {
alloc::handle_alloc_error(layout);
}
(1, ptr)
} else {
let new_cap = self.cap * 2;
let old_num_bytes = elem_size * self.cap;
assert!(
old_num_bytes <= (::std::isize::MAX as usize) / 2,
"capacity overflow"
);
let new_num_bytes = old_num_bytes * 2;
let layout = alloc::Layout::from_size_align_unchecked(old_num_bytes, align);
let ptr = alloc::realloc(self.ptr.as_ptr() as *mut _, layout, new_num_bytes);
if ptr.is_null() {
alloc::handle_alloc_error(layout);
}
(new_cap, ptr)
};
self.cap = cap;
self.ptr = Unique::new(ptr as *mut _).unwrap();
}
}
}
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 layout = alloc::Layout::from_size_align_unchecked(
self.cap * mem::size_of::<T>(),
mem::align_of::<T>(),
);
alloc::dealloc(self.ptr.as_ptr() as *mut _, layout);
}
}
}
}
pub struct Vec<T> {
buf: RawVec<T>,
len: usize,
}
impl<T> Default for Vec<T> {
fn default() -> Self {
Self::new()
}
}
impl<T> IntoIterator for Vec<T> {
type Item = T;
type IntoIter = IntoIter<T>;
fn into_iter(self) -> Self::IntoIter {
unsafe {
let buf = ptr::read(&self.buf);
let iter = RawValIter::new(&self);
mem::forget(self);
IntoIter { iter, _buf: buf }
}
}
}
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().add(self.len), elem);
}
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().add(self.len))) }
}
}
pub fn insert(&mut self, index: usize, elem: T) {
assert!(index <= self.len, "index out of bounds");
if self.len == self.cap() {
self.buf.grow();
}
unsafe {
if index < self.len {
ptr::copy(
self.ptr().add(index),
self.ptr().add(index + 1),
self.len - index,
);
}
ptr::write(self.ptr().add(index), 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().add(index));
ptr::copy(
self.ptr().add(index + 1),
self.ptr().add(index),
self.len - index,
);
result
}
}
pub fn drain(&mut self) -> Drain<T> {
unsafe {
let iter = RawValIter::new(&self);
self.len = 0;
Drain {
iter,
vec: PhantomData,
}
}
}
}
impl<T> Drop for Vec<T> {
fn drop(&mut self) {
if self.buf.cap != 0 {
eprintln!("Dropping cap: {}", self.buf.cap);
while let Some(_) = self.pop() {}
}
}
}
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.is_empty() {
slice.as_ptr()
} else {
slice.as_ptr().add(slice.len())
},
}
}
}
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>,
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) {
for _ in &mut self.iter {}
}
}
fn main() {
let mut v = Vec::<i32>::new();
v.push(3);
v.push(2);
v.push(1);
v.insert(1, 4);
v.insert(1, 8);
v.sort();
v.remove(1);
println!("{:?}", v.pop());
for i in v.into_iter().rev() {
print!("{} ", i);
}
println!();
let mut v = Vec::<()>::new();
v.push(());
v.push(());
v.push(());
for i in v.into_iter() {
print!("{:?} ", i);
}
}
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment