rust: add a bit operation module

The bindgen supports `static inline` function binding since v0.64.0 as
an experimental feature (`--wrap-static-fns`), and stabilizes it after
v0.70.0.

But the oldest version of bindgen supported by QEMU is v0.60.1, so
there's no way to generate the binding for deposit64() which is `static
inline` (in include/qemu/bitops.h).

Instead, implement it by hand in Rust and make it available for all
unsigned types through an IntegerExt trait. Since it only involves bit
operations, the Rust version of the code is almost identical to the
original C version, but it applies to more types than just u64.

Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Co-authored-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/rust/qemu-api/meson.build b/rust/qemu-api/meson.build
index b927eb58c8e672cd52066efc5915ce8b8a3098ef..adcee661150a697b2f1b98253f7a5a173e27dd2b 100644 (file)
--- a/rust/qemu-api/meson.build
+++ b/rust/qemu-api/meson.build
@@ -16,6 +16,7 @@ _qemu_api_rs = static_library(
     [
       'src/lib.rs',
       'src/bindings.rs',
+      'src/bitops.rs',
       'src/cell.rs',
       'src/c_str.rs',
       'src/definitions.rs',

diff --git a/rust/qemu-api/src/bitops.rs b/rust/qemu-api/src/bitops.rs
new file mode 100644 (file)
index 0000000..023ec1a
--- /dev/null
+++ b/rust/qemu-api/src/bitops.rs
@@ -0,0 +1,119 @@
+// Copyright (C) 2024 Intel Corporation.
+// Author(s): Zhao Liu <zhai1.liu@intel.com>
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+//! This module provides bit operation extensions to integer types.
+//! It is usually included via the `qemu_api` prelude.
+
+use std::ops::{
+    Add, AddAssign, BitAnd, BitAndAssign, BitOr, BitOrAssign, BitXor, BitXorAssign, Div, DivAssign,
+    Mul, MulAssign, Not, Rem, RemAssign, Shl, ShlAssign, Shr, ShrAssign,
+};
+
+/// Trait for extensions to integer types
+pub trait IntegerExt:
+    Add<Self, Output = Self> + AddAssign<Self> +
+    BitAnd<Self, Output = Self> + BitAndAssign<Self> +
+    BitOr<Self, Output = Self> + BitOrAssign<Self> +
+    BitXor<Self, Output = Self> + BitXorAssign<Self> +
+    Copy +
+    Div<Self, Output = Self> + DivAssign<Self> +
+    Eq +
+    Mul<Self, Output = Self> + MulAssign<Self> +
+    Not<Output = Self> + Ord + PartialOrd +
+    Rem<Self, Output = Self> + RemAssign<Self> +
+    Shl<Self, Output = Self> + ShlAssign<Self> +
+    Shl<u32, Output = Self> + ShlAssign<u32> + // add more as needed
+    Shr<Self, Output = Self> + ShrAssign<Self> +
+    Shr<u32, Output = Self> + ShrAssign<u32> // add more as needed
+{
+    const BITS: u32;
+    const MAX: Self;
+    const MIN: Self;
+    const ONE: Self;
+    const ZERO: Self;
+
+    #[inline]
+    #[must_use]
+    fn bit(start: u32) -> Self
+    {
+        debug_assert!(start < Self::BITS);
+
+        Self::ONE << start
+    }
+
+    #[inline]
+    #[must_use]
+    fn mask(start: u32, length: u32) -> Self
+    {
+        /* FIXME: Implement a more elegant check with error handling support? */
+        debug_assert!(start < Self::BITS && length > 0 && length <= Self::BITS - start);
+
+        (Self::MAX >> (Self::BITS - length)) << start
+    }
+
+    #[inline]
+    #[must_use]
+    fn deposit<U: IntegerExt>(self, start: u32, length: u32,
+                          fieldval: U) -> Self
+        where Self: From<U>
+    {
+        debug_assert!(length <= U::BITS);
+
+        let mask = Self::mask(start, length);
+        (self & !mask) | ((Self::from(fieldval) << start) & mask)
+    }
+
+    #[inline]
+    #[must_use]
+    fn extract(self, start: u32, length: u32) -> Self
+    {
+        let mask = Self::mask(start, length);
+        (self & mask) >> start
+    }
+}
+
+macro_rules! impl_num_ext {
+    ($type:ty) => {
+        impl IntegerExt for $type {
+            const BITS: u32 = <$type>::BITS;
+            const MAX: Self = <$type>::MAX;
+            const MIN: Self = <$type>::MIN;
+            const ONE: Self = 1;
+            const ZERO: Self = 0;
+        }
+    };
+}
+
+impl_num_ext!(u8);
+impl_num_ext!(u16);
+impl_num_ext!(u32);
+impl_num_ext!(u64);
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_deposit() {
+        assert_eq!(15u32.deposit(8, 8, 1u32), 256 + 15);
+        assert_eq!(15u32.deposit(8, 1, 255u8), 256 + 15);
+    }
+
+    #[test]
+    fn test_extract() {
+        assert_eq!(15u32.extract(2, 4), 3);
+    }
+
+    #[test]
+    fn test_bit() {
+        assert_eq!(u8::bit(7), 128);
+        assert_eq!(u32::bit(16), 0x10000);
+    }
+
+    #[test]
+    fn test_mask() {
+        assert_eq!(u8::mask(7, 1), 128);
+        assert_eq!(u32::mask(8, 8), 0xff00);
+    }
+}

diff --git a/rust/qemu-api/src/lib.rs b/rust/qemu-api/src/lib.rs
index 0efbef474419dbb52e21144c48aaa94cca588b8c..9e007e163546a299eefb813305964a2d27fb9fc7 100644 (file)
--- a/rust/qemu-api/src/lib.rs
+++ b/rust/qemu-api/src/lib.rs
@@ -12,6 +12,7 @@ pub mod bindings;
 #[rustfmt::skip]
 pub mod prelude;
 
+pub mod bitops;
 pub mod c_str;
 pub mod cell;
 pub mod definitions;

diff --git a/rust/qemu-api/src/prelude.rs b/rust/qemu-api/src/prelude.rs
index dfaddbd062ad30075d648d016d629f6d8758952a..a39e228babf2ccf8e53801d602f6324bd53502c3 100644 (file)
--- a/rust/qemu-api/src/prelude.rs
+++ b/rust/qemu-api/src/prelude.rs
@@ -2,5 +2,7 @@
 // Author(s): Paolo Bonzini <pbonzini@redhat.com>
 // SPDX-License-Identifier: GPL-2.0-or-later
 
+pub use crate::bitops::IntegerExt;
+
 pub use crate::cell::BqlCell;
 pub use crate::cell::BqlRefCell;