Moving to bytemuck

Fushia_LICENSE

@@ -0,0 +1,24 @@
+Copyright 2019 The Fuchsia Authors.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

README.md

@@ -1,5 +1,5 @@
 # heed
-A fully typed [LMDB]/[MDBX] wrapper with minimum overhead, uses zerocopy internally.
+A fully typed [LMDB]/[MDBX] wrapper with minimum overhead, uses bytemuck internally.
 
 [![Build Status](https://dev.azure.com/renaultcle/heed/_apis/build/status/Kerollmops.heed?branchName=master)](https://dev.azure.com/renaultcle/heed/_build/latest?definitionId=1&branchName=master)
 [![Dependency Status](https://deps.rs/repo/github/Kerollmops/heed/status.svg)](https://deps.rs/repo/github/Kerollmops/heed)

heed-types/Cargo.toml

@@ -10,10 +10,14 @@ edition = "2018"
 
 [dependencies]
 bincode = { version = "1.2.1", optional = true }
+bytemuck = { version = "1.5.0", features = ["extern_crate_alloc"] }
+byteorder = "1.4.2"
 heed-traits = { version = "0.7.0", path = "../heed-traits" }
 serde = { version = "1.0.117", optional = true }
 serde_json = { version = "1.0.59", optional = true }
-zerocopy = "0.3.0"
+
+[dev-dependencies]
+rand = "0.8.2"
 
 [features]
 default = ["serde-bincode", "serde-json"]

heed-types/src/cow_slice.rs

@@ -1,9 +1,7 @@
 use std::borrow::Cow;
-use std::{mem, ptr};
 
-use crate::aligned_to;
+use bytemuck::{Pod, PodCastError, try_cast_slice, pod_collect_to_vec};
 use heed_traits::{BytesDecode, BytesEncode};
-use zerocopy::{AsBytes, FromBytes, LayoutVerified};
 
 /// Describes a slice that must be [memory aligned] and
 /// will be reallocated if it is not.
@@ -22,47 +20,22 @@ use zerocopy::{AsBytes, FromBytes, LayoutVerified};
 /// [`OwnedSlice`]: crate::OwnedSlice
 pub struct CowSlice<T>(std::marker::PhantomData<T>);
 
-impl<'a, T: 'a> BytesEncode<'a> for CowSlice<T>
-where
-    T: AsBytes,
-{
+impl<'a, T: Pod> BytesEncode<'a> for CowSlice<T> {
     type EItem = [T];
 
     fn bytes_encode(item: &'a Self::EItem) -> Option<Cow<[u8]>> {
-        Some(Cow::Borrowed(<[T] as AsBytes>::as_bytes(item)))
+        try_cast_slice(item).map(Cow::Borrowed).ok()
     }
 }
 
-impl<'a, T: 'a> BytesDecode<'a> for CowSlice<T>
-where
-    T: FromBytes + Copy,
-{
+impl<'a, T: Pod> BytesDecode<'a> for CowSlice<T> {
     type DItem = Cow<'a, [T]>;
 
     fn bytes_decode(bytes: &'a [u8]) -> Option<Self::DItem> {
-        match LayoutVerified::<_, [T]>::new_slice(bytes) {
-            Some(layout) => Some(Cow::Borrowed(layout.into_slice())),
-            None => {
-                let len = bytes.len();
-                let elem_size = mem::size_of::<T>();
-
-                // ensure that it is the alignment that is wrong
-                // and the length is valid
-                if len % elem_size == 0 && !aligned_to(bytes, mem::align_of::<T>()) {
-                    let elems = len / elem_size;
-                    let mut vec = Vec::<T>::with_capacity(elems);
-
-                    unsafe {
-                        let dst = vec.as_mut_ptr() as *mut u8;
-                        ptr::copy_nonoverlapping(bytes.as_ptr(), dst, len);
-                        vec.set_len(elems);
-                    }
-
-                    return Some(Cow::Owned(vec));
-                }
-
-                None
-            }
+        match try_cast_slice(bytes) {
+            Ok(items) => Some(Cow::Borrowed(items)),
+            Err(PodCastError::AlignmentMismatch) => Some(Cow::Owned(pod_collect_to_vec(bytes))),
+            Err(_) => None,
         }
     }
 }

heed-types/src/cow_type.rs

@@ -1,9 +1,7 @@
 use std::borrow::Cow;
-use std::{mem, ptr};
 
-use crate::aligned_to;
 use heed_traits::{BytesDecode, BytesEncode};
-use zerocopy::{AsBytes, FromBytes, LayoutVerified};
+use bytemuck::{Pod, PodCastError, bytes_of, bytes_of_mut, try_from_bytes};
 
 /// Describes a type that must be [memory aligned] and
 /// will be reallocated if it is not.
@@ -28,44 +26,26 @@ use zerocopy::{AsBytes, FromBytes, LayoutVerified};
 /// [`CowSlice`]: crate::CowSlice
 pub struct CowType<T>(std::marker::PhantomData<T>);
 
-impl<'a, T: 'a> BytesEncode<'a> for CowType<T>
-where
-    T: AsBytes,
-{
+impl<'a, T: Pod> BytesEncode<'a> for CowType<T> {
     type EItem = T;
 
     fn bytes_encode(item: &'a Self::EItem) -> Option<Cow<[u8]>> {
-        Some(Cow::Borrowed(<T as AsBytes>::as_bytes(item)))
+        Some(Cow::Borrowed(bytes_of(item)))
     }
 }
 
-impl<'a, T: 'a> BytesDecode<'a> for CowType<T>
-where
-    T: FromBytes + Copy,
-{
+impl<'a, T: Pod> BytesDecode<'a> for CowType<T> {
     type DItem = Cow<'a, T>;
 
     fn bytes_decode(bytes: &'a [u8]) -> Option<Self::DItem> {
-        match LayoutVerified::<_, T>::new(bytes) {
-            Some(layout) => Some(Cow::Borrowed(layout.into_ref())),
-            None => {
-                let len = bytes.len();
-                let elem_size = mem::size_of::<T>();
-
-                // ensure that it is the alignment that is wrong
-                // and the length is valid
-                if len == elem_size && !aligned_to(bytes, mem::align_of::<T>()) {
-                    let mut data = mem::MaybeUninit::<T>::uninit();
-
-                    unsafe {
-                        let dst = data.as_mut_ptr() as *mut u8;
-                        ptr::copy_nonoverlapping(bytes.as_ptr(), dst, len);
-                        return Some(Cow::Owned(data.assume_init()));
-                    }
-                }
-
-                None
-            }
+        match try_from_bytes(bytes) {
+            Ok(item) => Some(Cow::Borrowed(item)),
+            Err(PodCastError::TargetAlignmentGreaterAndInputNotAligned) => {
+                let mut item = T::zeroed();
+                bytes_of_mut(&mut item).copy_from_slice(bytes);
+                Some(Cow::Owned(item))
+            },
+            Err(_) => None,
         }
     }
 }