more functionalities for the vec

crates/datastructures/src/vec.rs

@@ -4,7 +4,6 @@
 //! https://doc.rust-lang.org/nomicon/vec/vec.html
 
 use std::{
-    marker::PhantomData,
     mem,
     ops::{Deref, DerefMut, Index, IndexMut},
     ptr,
@@ -15,7 +14,6 @@ use crate::raw_vec::RawVec;
 #[derive(Clone, Debug)]
 pub struct Vec<T> {
     used: usize,
-    marker: PhantomData<T>,
     buf: RawVec<T>,
 }
 
@@ -32,7 +30,6 @@ impl<T> Vec<T> {
         }
         Vec {
             used: 0,
-            marker: PhantomData,
             buf: RawVec::new(),
         }
     }
@@ -47,6 +44,14 @@ impl<T> Vec<T> {
         v
     }
 
+    pub fn from_slice(data: &[T]) -> Self {
+        let mut v = Vec::<T>::with_capacity(data.len());
+        unsafe {
+            ptr::copy_nonoverlapping(data.as_ptr(), v.as_mut_ptr(), data.len());
+        }
+        v
+    }
+
     pub fn pop(&mut self) -> Option<T> {
         if self.used == 0 {
             None
@@ -121,6 +126,32 @@ impl<T> Vec<T> {
     pub fn reserve(&mut self, added_capacity: usize) {
         self.buf.grow_by(added_capacity);
     }
+
+    #[must_use]
+    pub fn split_off(&mut self, at: usize) -> Self {
+        let other_len = self.used - at;
+        let mut other = Self::with_capacity(other_len);
+        unsafe {
+            self.set_len(at);
+            other.set_len(other_len);
+            ptr::copy_nonoverlapping(self.as_ptr().add(at), other.as_mut_ptr(), other.len());
+        }
+        other
+    }
+
+    unsafe fn set_len(&mut self, new_length: usize) {
+        self.used = new_length
+    }
+
+    #[must_use]
+    pub const fn as_ptr(&self) -> *const T {
+        self.buf.ptr.as_ptr()
+    }
+
+    #[must_use]
+    pub const fn as_mut_ptr(&mut self) -> *mut T {
+        self.buf.ptr.as_ptr()
+    }
 }
 
 impl<T> Index<usize> for Vec<T> {
@@ -158,6 +189,12 @@ impl<T> Drop for Vec<T> {
     }
 }
 
+impl<T> From<&[T]> for Vec<T> {
+    fn from(value: &[T]) -> Self {
+        Self::from_slice(value)
+    }
+}
+
 unsafe impl<T: Send> Send for Vec<T> {}
 unsafe impl<T: Sync> Sync for Vec<T> {}