[RFC 05/13] rust: add a bit operation binding for deposit64

[Zhao Liu]

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).

Manually implement a binding. Since it only involves bit operations,
fortunately, the Rust version of deposit64() is almost identical to the
original C version.

Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
---
 rust/qemu-api/meson.build   |  1 +
 rust/qemu-api/src/bitops.rs | 11 +++++++++++
 rust/qemu-api/src/lib.rs    |  1 +
 3 files changed, 13 insertions(+)
 create mode 100644 rust/qemu-api/src/bitops.rs

diff --git a/rust/qemu-api/meson.build b/rust/qemu-api/meson.build
index 3ac69cbc76c4..00e86a679d8a 100644
--- 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/irq.rs',
diff --git a/rust/qemu-api/src/bitops.rs b/rust/qemu-api/src/bitops.rs
new file mode 100644
index 000000000000..a11a07fb8830
--- /dev/null
+++ b/rust/qemu-api/src/bitops.rs
@@ -0,0 +1,11 @@
+// Copyright (C) 2024 Intel Corporation.
+// Author(s): Zhao Liu <zhai1.liu@intel.com>
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+pub fn deposit64(value: u64, start: usize, length: usize, fieldval: u64) -> 
u64 {
+    /* FIXME: Implement a more elegant check with error handling support? */
+    assert!(length > 0 && length <= 64 - start);
+
+    let mask = (u64::MAX >> (64 - length)) << start;
+    (value & !mask) | ((fieldval << start) & mask)
+}
diff --git a/rust/qemu-api/src/lib.rs b/rust/qemu-api/src/lib.rs
index 0d46b372c6bb..009906c907e7 100644
--- a/rust/qemu-api/src/lib.rs
+++ b/rust/qemu-api/src/lib.rs
@@ -7,6 +7,7 @@
 #[rustfmt::skip]
 pub mod bindings;
 
+pub mod bitops;
 pub mod c_str;
 pub mod cell;
 pub mod irq;
-- 
2.34.1