介绍

本系列录制的视频主要放在B站上Rust死灵书学习视频

Rust 死灵书相关的源码资料在github.com/anonymousGiga/Rustonomi...

详细内容

下面为MyVec实现insert和remove函数：

复制
#![feature(ptr_internals)]
use std::mem;
use std::alloc::{alloc, realloc, dealloc, Layout, handle_alloc_error};
use std::ptr::{Unique, self};
use std::ops::{Deref, DerefMut};
use std::slice;
 
#[derive(Debug)]
pub struct MyVec<T> {
    ptr: Unique<T>,
    cap: usize,
    len: usize,
}
 
impl<T> MyVec<T> {
    fn new() -> Self {
        assert!(mem::size_of::<T>() != 0, "还没准备好处理零尺寸类型");
        MyVec { ptr: Unique::dangling(), len: 0, cap: 0 }}
 
    fn grow(&mut self) {
        unsafe {let align = mem::align_of::<T>();let elem_size = mem::size_of::<T>();let layout: Layout;
 
            let (new_cap, ptr) = if self.cap == 0 {
                layout = Layout::from_size_align_unchecked(elem_size, align);let ptr = alloc(layout);(1, ptr)} else {let new_cap = self.cap * 2;let old_num_bytes = self.cap * elem_size;
 
                assert!(old_num_bytes <= (isize::MAX as usize) / 2,"capacity overflow");
 
                let new_num_bytes = old_num_bytes * 2;
                layout = Layout::from_size_align_unchecked(new_num_bytes, align);let ptr = realloc(self.ptr.as_ptr() as *mut _,
                                      layout,
                                    new_num_bytes);(new_cap, ptr)};
 
            if ptr.is_null() { handle_alloc_error(layout); }
 
            if let Some(ptr) = Unique::new(ptr as *mut _) {
                self.ptr = ptr;} else {
                panic!("error!");}
            self.cap = new_cap;}}
 
    fn push(&mut self, elem: T) {if self.len == self.cap { 
            self.grow(); 
        }
 
        //关键点在于要直接覆盖，因为不知道内存之前是否有东西 
        unsafe {
            ptr::write(self.ptr.as_ptr().offset(self.len as isize), elem);}
 
        self.len += 1;}
 
    fn pop(&mut self) -> Option<T> {if self.len == 0 {
            None
        } else {
            self.len -= 1;
            unsafe {Some(ptr::read(self.ptr.as_ptr().offset(self.len as isize)))}}}
 
    fn insert(&mut self, index: usize, elem: T) {
        assert!(index <= self.len, "越界");if self.cap == self.len { 
            self.grow(); 
        }
 
        unsafe {if index < self.len {
                ptr::copy(self.ptr.as_ptr().offset(index as isize),
                        self.ptr.as_ptr().offset((index as isize) + 1),
                        self.len - index);}
            ptr::write(self.ptr.as_ptr().offset(index as isize), elem);
            self.len += 1;}}
 
    fn remove(&mut self, index: usize) -> T {
        assert!(index < self.len, "越界");
        unsafe {
            self.len -= 1;let result = ptr::read(self.ptr.as_ptr().offset(index as isize));
            ptr::copy(self.ptr.as_ptr().offset(index as isize + 1), 
                    self.ptr.as_ptr().offset(index as isize),
                    self.len - index);
            result
        }}
}
 
impl<T> Drop for MyVec<T> {
    fn drop(&mut self) {if self.cap != 0 {while let Some(_) = self.pop() {}
 
            let align = mem::align_of::<T>();let elem_size = mem::size_of::<T>();let num_bytes = elem_size * self.cap;
 
            unsafe {let layout: Layout = Layout::from_size_align_unchecked(num_bytes, align);dealloc(self.ptr.as_ptr() as *mut _, layout)}
 
            println!("release memory in drop function!");}}
}
 
impl<T> Deref for MyVec<T> {
    type Target = [T];
    fn deref(&self) -> &[T] {
        unsafe {
            slice::from_raw_parts(self.ptr.as_ptr(), self.len)}}
}
 
impl<T> DerefMut for MyVec<T> {
    fn deref_mut(&mut self) -> &mut [T] {
        unsafe {
            slice::from_raw_parts_mut(self.ptr.as_ptr(), self.len)}}
}
 
fn main() {
 
    {let mut vec: MyVec<i32> = MyVec::new();
        vec.push(8);
        vec.push(7);
        vec.push(6);
 
        while let Some(v) = vec.pop() {
            println!("v == {}", v);}
 
        vec.push(8);
        vec.push(7);
        vec.push(6);
 
        let s = &vec[1..];
        println!("s[0] == {}", s[0]);
 
        let s = &mut vec[1..];
        s[0] = 10;
        println!("s[0] == {}", s[0]);
 
        println!("-------------------------------");let mut vec2: MyVec<i32> = MyVec::new();
        vec2.push(1);
        vec2.push(2);
        vec2.push(3);//打印//while let Some(v) = vec2.pop() {//    println!("v == {}", v);//}
 
 
        vec2.insert(1, 11);let ret = vec2.remove(2);
        println!("remove elem: {}", ret);//打印while let Some(v) = vec2.pop() { 
            println!("v == {}", v);}}
 
    println!("Hello, world!");
}