Vendor dependencies

notes-service/vendor/bitvec/doc/ptr/read_volatile.md

@@ -0,0 +1,39 @@
+# Single-Bit Volatile Read
+
+This reads the bit out of `src` directly, using a volatile I/O intrinsic to
+prevent compiler reördering or removal.
+
+You should not use `bitvec` to perform any volatile I/O operations. You should
+instead do volatile I/O work on integer values directly, or use a crate like
+[`voladdress`][0] to perform I/O transactions, and use `bitvec` only on stack
+locals that have no additional memory semantics.
+
+## Original
+
+[`ptr::read_volatile`](core::ptr::read_volatile)
+
+## Safety
+
+Because this performs a dereference of memory, it inherits the original
+`ptr::read_volatile`’s requirements:
+
+- `src` must be valid to read.
+- `src` must be properly aligned. This is an invariant of the `BitPtr` type as
+  well as of the memory access.
+- `src` must point to an initialized value of `T`.
+
+Remember that volatile accesses are ordinary loads that the compiler cannot
+remove or reörder! They are *not* an atomic synchronizer.
+
+## Examples
+
+```rust
+use bitvec::prelude::*;
+use bitvec::ptr as bv_ptr;
+
+let data = 128u8;
+let ptr = BitPtr::<_, _, Msb0>::from_ref(&data);
+assert!(unsafe { bv_ptr::read_volatile(ptr) });
+```
+
+[0]: https://docs.rs/voladdress/latest/voladdress