bendns' repos / helix
Unnamed repository; edit this file 'description' to name the repository.
Diffstat (limited to 'helix-config/src/any.rs')
-rw-r--r--helix-config/src/any.rs76
1 files changed, 76 insertions, 0 deletions
diff --git a/helix-config/src/any.rs b/helix-config/src/any.rs
new file mode 100644
index 00000000..891d9e8c
--- /dev/null
+++ b/helix-config/src/any.rs
@@ -0,0 +1,76 @@
+/// this is a reimplementation of dynamic dispatch that only stores the
+/// information we need and stores everythin inline. Values that are smaller or
+/// the same size as a slice (2 usize) are also stored inline. This avoids
+/// significant overallocation when setting lots of simple config
+/// options (integers, strings, lists, enums)
+use std::any::{Any, TypeId};
+use std::mem::{align_of, size_of, MaybeUninit};
+
+pub struct ConfigData {
+ data: MaybeUninit<[usize; 2]>,
+ ty: TypeId,
+ drop_fn: unsafe fn(MaybeUninit<[usize; 2]>),
+}
+
+const fn store_inline<T>() -> bool {
+ size_of::<T>() <= size_of::<[usize; 2]>() && align_of::<T>() <= align_of::<[usize; 2]>()
+}
+
+impl ConfigData {
+ unsafe fn drop_impl<T: Any>(mut data: MaybeUninit<[usize; 2]>) {
+ if store_inline::<T>() {
+ data.as_mut_ptr().cast::<T>().drop_in_place();
+ } else {
+ let ptr = data.as_mut_ptr().cast::<*mut T>().read();
+ drop(Box::from_raw(ptr));
+ }
+ }
+
+ pub fn get<T: Any>(&self) -> &T {
+ assert_eq!(TypeId::of::<T>(), self.ty);
+ unsafe {
+ if store_inline::<T>() {
+ return &*self.data.as_ptr().cast();
+ }
+ let data: *const T = self.data.as_ptr().cast::<*const T>().read();
+ &*data
+ }
+ }
+ pub fn new<T: Any>(val: T) -> Self {
+ let mut data = MaybeUninit::uninit();
+ if store_inline::<T>() {
+ let data: *mut T = data.as_mut_ptr() as _;
+ unsafe {
+ data.write(val);
+ }
+ } else {
+ assert!(store_inline::<*const T>());
+ let data: *mut *const T = data.as_mut_ptr() as _;
+ unsafe {
+ data.write(Box::into_raw(Box::new(val)));
+ }
+ };
+ Self {
+ data,
+ ty: TypeId::of::<T>(),
+ drop_fn: ConfigData::drop_impl::<T>,
+ }
+ }
+}
+
+impl Drop for ConfigData {
+ fn drop(&mut self) {
+ unsafe {
+ (self.drop_fn)(self.data);
+ }
+ }
+}
+
+impl std::fmt::Debug for ConfigData {
+ fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+ f.debug_struct("ConfigData").finish_non_exhaustive()
+ }
+}
+
+unsafe impl Send for ConfigData {}
+unsafe impl Sync for ConfigData {}