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This procedural macro attribute provides a simple way to declare
a trait with a set of operations that later users can partially
implement, providing compile-time `HAS_*` boolean associated
constants that indicate whether a particular operation was overridden.
This is useful as the Rust counterpart to structs like
`file_operations` where some pointers may be `NULL`, indicating
an operation is not provided.
For instance:
#[vtable]
trait Operations {
fn read(...) -> Result<usize> {
Err(EINVAL)
}
fn write(...) -> Result<usize> {
Err(EINVAL)
}
}
#[vtable]
impl Operations for S {
fn read(...) -> Result<usize> {
...
}
}
assert_eq!(<S as Operations>::HAS_READ, true);
assert_eq!(<S as Operations>::HAS_WRITE, false);
Signed-off-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Sergio González Collado <sergio.collado@gmail.com>
[Reworded, adapted for upstream and applied latest changes]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
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