Merge pull request #40 from TheBlueMatt/main

[ldk-c-bindings] / lightning-c-bindings / src / c_types / mod.rs

diff --git a/lightning-c-bindings/src/c_types/mod.rs b/lightning-c-bindings/src/c_types/mod.rs
index 2648a9b39092dbdf96576e4dc998cae10eaf8282..09c8a5147d4c096fea4c1313af2497a659072269 100644 (file)
--- a/lightning-c-bindings/src/c_types/mod.rs
+++ b/lightning-c-bindings/src/c_types/mod.rs
@@ -527,3 +527,51 @@ impl<T> TakePointer<*mut T> for *mut T {
                ret
        }
 }
+
+
+pub(crate) mod ObjOps {
+       #[inline]
+       #[must_use = "returns new dangling pointer"]
+       pub(crate) fn heap_alloc<T>(obj: T) -> *mut T {
+               let ptr = Box::into_raw(Box::new(obj));
+               nonnull_ptr_to_inner(ptr)
+       }
+       #[inline]
+       pub(crate) fn nonnull_ptr_to_inner<T>(ptr: *const T) -> *mut T {
+               if core::mem::size_of::<T>() == 0 {
+                       // We map `None::<T>` as `T { inner: null, .. }` which works great for all
+                       // non-Zero-Sized-Types `T`.
+                       // For ZSTs, we need to differentiate between null implying `None` and null implying
+                       // `Some` with no allocation.
+                       // Thus, for ZSTs, we add one (usually) page here, which should always be aligned.
+                       // Note that this relies on undefined behavior! A pointer to NULL may be valid, but a
+                       // pointer to NULL + 4096 is almost certainly not. That said, Rust's existing use of
+                       // `(*mut T)1` for the pointer we're adding to is also not defined, so we should be
+                       // fine.
+                       // Note that we add 4095 here as at least the Java client assumes that the low bit on
+                       // any heap pointer is 0, which is generally provided by malloc, but which is not true
+                       // for ZSTs "allocated" by `Box::new`.
+                       debug_assert_eq!(ptr as usize, 1);
+                       unsafe { (ptr as *mut T).cast::<u8>().add(4096 - 1).cast::<T>() }
+               } else {
+                       // In order to get better test coverage, also increment non-ZST pointers with
+                       // --cfg=test_mod_pointers, which is set in genbindings.sh for debug builds.
+                       #[cfg(test_mod_pointers)]
+                       unsafe { (ptr as *mut T).cast::<u8>().add(4096).cast::<T>() }
+                       #[cfg(not(test_mod_pointers))]
+                       unsafe { ptr as *mut T }
+               }
+       }
+       #[inline]
+       /// Invert nonnull_ptr_to_inner
+       pub(crate) fn untweak_ptr<T>(ptr: *mut T) -> *mut T {
+               if core::mem::size_of::<T>() == 0 {
+                       unsafe { ptr.cast::<u8>().sub(4096 - 1).cast::<T>() }
+               } else {
+                       #[cfg(test_mod_pointers)]
+                       unsafe { ptr.cast::<u8>().sub(4096).cast::<T>() }
+                       #[cfg(not(test_mod_pointers))]
+                       ptr
+               }
+       }
+}