undo last commit, fix some wording

src/lib.rs

@@ -8,15 +8,12 @@ mod test;
 pub mod prelude;
 
 use core::panic;
-#[cfg(feature = "only_store_meta")]
-use std::{ptr::Pointee, mem::align_of_val_raw};
 use std::{
-    ptr::{NonNull, self, drop_in_place, metadata, Pointee},
+    ptr::{NonNull, self, drop_in_place, metadata},
     marker::PhantomData,
     alloc::{alloc, Layout},
-    mem::{size_of, size_of_val, align_of_val, self, size_of_val_raw, align_of_val_raw},
+    mem::{size_of, size_of_val, align_of_val, self, size_of_val_raw},
     slice,
-    fmt::Debug,
     ops::{CoerceUnsized, Index, IndexMut}
 };
 
@@ -44,75 +41,15 @@ fn align_up_mut<T: ?Sized>(ptr: *mut T, align: usize) -> *mut T {
     align_up(ptr as _, align) as _
 }
 
-trait Strategy<T: ?Sized>: Sized {
-    type Metadata: Copy;
-
-    unsafe fn get_ptr(vec: &Vec<T, Self>, index: usize) -> *const T;
-
-    unsafe fn next(vec: &Vec<T, Self>, prev: *const T, index: usize) -> *const T;
-
-    fn create_meta_from_ptr(vec: &Vec<T, Self>, ptr: *const T) -> Self::Metadata;
-}
-
-struct StorePtr;
-
-impl<T: ?Sized> Strategy<T> for StorePtr {
-    type Metadata = *const T;
-
-    unsafe fn get_ptr(vec: &Vec<T, Self>, index: usize) -> *const T {
-        vec.get_ptr_to_meta(index + 1).cast::<*const T>().read()
-    }
-
-    unsafe fn next(vec: &Vec<T, Self>, _prev: *const T, index: usize) -> *const T {
-        Self::get_ptr(vec, index)
-    }
-
-    fn create_meta_from_ptr(_vec: &Vec<T, Self>, ptr: *const T) -> Self::Metadata {
-        ptr
-    }
-}
-
-struct OnlyStoreMeta;
-
-impl<T: ?Sized> Strategy<T> for OnlyStoreMeta {
-    type Metadata = <T as Pointee>::Metadata;
-
-    unsafe fn get_ptr(vec: &Vec<T, Self>, index: usize) -> *const T {
-        let meta = vec.get_ptr_to_meta(1).cast::<<T as Pointee>::Metadata>().read();
-        let fake = ptr::from_raw_parts::<T>(0 as _, meta);
-        let ptr = align_up(vec.ptr.as_ptr(), align_of_val_raw(fake));
-        let mut ptr = ptr::from_raw_parts(ptr.cast(), meta);
-
-        for index in 1..=index {
-            ptr = Self::next(vec, ptr, index);
-        }
-
-        ptr
-    }
-
-    unsafe fn next(vec: &Vec<T, Self>, prev: *const T, index: usize) -> *const T {
-        let ptr = prev.cast::<u8>().wrapping_add(size_of_val_raw(prev));
-
-        let meta = vec.get_ptr_to_meta(index + 1).cast::<<T as Pointee>::Metadata>().read();
-        let fake = ptr::from_raw_parts::<T>(0 as _, meta);
-        let ptr = align_up(ptr, align_of_val_raw(fake));
-        ptr::from_raw_parts(ptr.cast(), meta)
-    }
-
-    fn create_meta_from_ptr(_vec: &Vec<T, Self>, ptr: *const T) -> Self::Metadata {
-        metadata(ptr)
-    }
-}
-
 /// A heap allocated, dynamically sized collection of `?Sized` elements.
 /// 
 /// See [`::alloc::vec::Vec`] (the standard library `Vec` type) for more information.
-struct Vec<T: ?Sized, S: Strategy<T>> {
+pub struct Vec<T: ?Sized> {
     ptr: NonNull<u8>,
     len: usize,
     capacity: usize,
     end_ptr: NonNull<u8>,
-    _phantom: PhantomData<(*mut S, T)>
+    _phantom: PhantomData<T>
 }
 
 // keeps this file cleaner
@@ -120,23 +57,10 @@ mod impls;
 mod iter;
 pub use iter::*;
 
-/// The data stored as metadata at the end of the allocation.
+/// The extra data stored at the end of the allocation.
-#[cfg(feature = "only_store_meta")]
+type Extra<T> = *const T;
-type Meta<T> = <T as Pointee>::Metadata;
-#[cfg(not(feature = "only_store_meta"))]
-type Meta<T> = *const T;
 
-#[cfg(feature = "only_store_meta")]
+impl<T: ?Sized> Vec<T> {
-unsafe fn size_of_val_meta<T: ?Sized>(meta: Meta<T>) -> usize {
-    size_of_val_raw(ptr::from_raw_parts::<T>(0 as *const (), meta))
-}
-
-#[cfg(feature = "only_store_meta")]
-unsafe fn align_of_val_meta<T: ?Sized>(meta: Meta<T>) -> usize {
-    align_of_val_raw(ptr::from_raw_parts::<T>(0 as *const (), meta))
-}
-
-impl<T: ?Sized, S: Strategy<T>> Vec<T, S> {
     /// Creates a new, empty `Vec`.
     pub fn new() -> Self {
         let ptr = NonNull::dangling();
@@ -182,7 +106,7 @@ impl<T: ?Sized, S: Strategy<T>> Vec<T, S> {
             // make sure we have enough space for a new element, but also space for future elements
             // this bit is tricky, we must make sure we have enough space for padding too, so its probably UB somehow
             // FIXME: ^^^
-            let new_alloc_size = self.capacity * 2 + size * 2 + size_of::<S::Metadata>();
+            let new_alloc_size = self.capacity * 2 + size * 2 + size_of::<Extra<T>>();
             self.realloc(new_alloc_size);
         }
 
@@ -201,7 +125,7 @@ impl<T: ?Sized, S: Strategy<T>> Vec<T, S> {
     /// Checks if a given element will fill in the `Vec` without reallocations.
     pub fn will_fit(&self, v: &T) -> bool {
         let remaining_space = self.get_ptr_to_meta(self.len) as usize - self.end_ptr.as_ptr() as usize;
-        let needed_space = size_of_val(v) + size_of::<S::Metadata>();
+        let needed_space = size_of_val(v) + size_of::<Extra<T>>();
         remaining_space >= needed_space
     }
 
@@ -252,7 +176,7 @@ impl<T: ?Sized, S: Strategy<T>> Vec<T, S> {
                 let meta_len = current_alloc_end as usize - meta_src as usize;
                 new_alloc_end.wrapping_sub(meta_len)
             };
-            let meta_size = self.len * size_of::<Meta<T>>();
+            let meta_size = self.len * size_of::<Extra<T>>();
             memcpy(meta_src.cast(), meta_dst, meta_size);
 
             dealloc(self.ptr.as_ptr(), Layout::from_size_align_unchecked(self.capacity, 8));
@@ -266,24 +190,19 @@ impl<T: ?Sized, S: Strategy<T>> Vec<T, S> {
     /// for internal use
     /// 
     /// NOTE: 1-indexed, to allow getting a pointer to the end of the alloc easily
-    fn get_ptr_to_meta(&self, index: usize) -> *mut S::Metadata {
+    fn get_ptr_to_meta(&self, index: usize) -> *mut Extra<T> {
         self.ptr.as_ptr()
         .wrapping_add(self.capacity)
-        .cast::<S::Metadata>()
+        .cast::<Extra<T>>()
         .wrapping_sub(index)
     }
 
-    /// for internal use
-    unsafe fn get_meta(&self, index: usize) -> S::Metadata {
-        *self.get_ptr_to_meta(index + 1)
-    }
-
     unsafe fn set_meta_from_ptr(&self, index: usize, ptr: *const T) {
-        self.get_ptr_to_meta(index + 1).write(S::create_meta_from_ptr(self, ptr));
+        self.get_ptr_to_meta(index + 1).write(ptr);
     }
 
     unsafe fn get_ptr(&self, index: usize) -> *const T {
-        S::get_ptr(self, index)
+        *self.get_ptr_to_meta(index + 1)
     }
 
     pub fn get(&self, index: usize) -> Option<&T> {
@@ -341,7 +260,7 @@ impl<T: ?Sized, S: Strategy<T>> Vec<T, S> {
     }
 
     /// Converts a `Vec<T: Sized>` into a `Vec<U: ?Sized>`, given that `T` can be `CoerceUnsized` into `U`.
-    pub fn unsize<U: ?Sized>(self) -> Vec<U> where for<'a> &'a T: CoerceUnsized<&'a U>, S: Strategy<U> {
+    pub fn unsize<U: ?Sized>(self) -> Vec<U> where for<'a> &'a T: CoerceUnsized<&'a U> {
         let new_vec = Vec::<U> {
             ptr: self.ptr,
             len: self.len,
@@ -350,15 +269,15 @@ impl<T: ?Sized, S: Strategy<T>> Vec<T, S> {
             _phantom: PhantomData,
         };
 
-        if size_of::<<S as Strategy<U>>::Metadata>() > size_of::<<S as Strategy<T>>::Metadata>() {
+        if size_of::<Extra<U>>() > size_of::<Extra<T>>() {
-            // new meta larger than old meta, must go from back to front
+            // new extra larger than old extra, must go from back to front
 
             for i in (0..self.len).rev() {
                 let current = unsafe { &*self.get_ptr(i) };
                 unsafe { new_vec.set_meta_from_ptr(i, current as &U) }
             }
         } else {
-            // new meta smaller or same size as old meta, must go from front to back
+            // new extra smaller or same size as old extra, must go from front to back
 
             for i in 0..self.len {
                 let current = unsafe { &*self.get_ptr(i) };