Optimize RepeatedField<Scalar>::copy_from
PiperOrigin-RevId: 582851734
diff --git a/rust/upb.rs b/rust/upb.rs
index 778dddc..136f4ed 100644
--- a/rust/upb.rs
+++ b/rust/upb.rs
@@ -13,7 +13,7 @@
use std::cell::UnsafeCell;
use std::fmt;
use std::marker::PhantomData;
-use std::mem::MaybeUninit;
+use std::mem::{size_of, MaybeUninit};
use std::ops::Deref;
use std::ptr::{self, NonNull};
use std::slice;
@@ -370,7 +370,9 @@
fn upb_Array_Set(arr: RawRepeatedField, i: usize, val: upb_MessageValue);
fn upb_Array_Get(arr: RawRepeatedField, i: usize) -> upb_MessageValue;
fn upb_Array_Append(arr: RawRepeatedField, val: upb_MessageValue, arena: RawArena);
- fn upb_Array_Resize(arr: RawRepeatedField, size: usize, arena: RawArena);
+ fn upb_Array_Resize(arr: RawRepeatedField, size: usize, arena: RawArena) -> bool;
+ fn upb_Array_MutableDataPtr(arr: RawRepeatedField) -> *mut std::ffi::c_void;
+ fn upb_Array_DataPtr(arr: RawRepeatedField) -> *const std::ffi::c_void;
}
macro_rules! impl_repeated_primitives {
@@ -412,16 +414,18 @@
) }
}
pub fn copy_from(&mut self, src: &RepeatedField<'_, $rs_type>) {
- // TODO: Optimize this copy_from implementation using memcopy.
- // NOTE: `src` cannot be `self` because this would violate borrowing rules.
- unsafe { upb_Array_Resize(self.inner.raw, 0, self.inner.arena.raw()) };
- // `upb_Array_DeepClone` is not used here because it returns
- // a new `upb_Array*`. The contained `RawRepeatedField` must
- // then be set to this new pointer, but other copies of this
- // pointer may exist because of re-borrowed `RepeatedMut`s.
- // Alternatively, a `clone_into` method could be exposed by upb.
- for i in 0..src.len() {
- self.push(src.get(i).unwrap());
+ // SAFETY:
+ // - `upb_Array_Resize` is unsafe but assumed to be always sound to call.
+ // - `copy_nonoverlapping` is unsafe but here we guarantee that both pointers
+ // are valid, the pointers are `#[repr(u8)]`, and the size is correct.
+ unsafe {
+ if (!upb_Array_Resize(self.inner.raw, src.len(), self.inner.arena.raw())) {
+ panic!("upb_Array_Resize failed.");
+ }
+ ptr::copy_nonoverlapping(
+ upb_Array_DataPtr(src.inner.raw).cast::<u8>(),
+ upb_Array_MutableDataPtr(self.inner.raw).cast::<u8>(),
+ size_of::<$rs_type>() * src.len());
}
}
}
