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

[Paolo Bonzini]

On 12/5/24 07:07, Zhao Liu wrote:
> +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)
> +}

This should be more generic and implemented as a trait that is
implemented by u8/u16/u32/u64.  It's okay to rewrite these utility
functions in Rust instead of relying on bindgen, because the way
you'd like to use them is likely different from C.  Something like:

pub trait IntegerExt
{
    fn deposit(self, start: u32, length: u32, fieldval: U) -> Self;
}

impl IntegerExt for u64
{
    fn deposit(self, 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)
    }
}

And we can add a "prelude" module so that you can do

use qemu_api::prelude::*;

and get all these useful traits at once.  I will send a patch after
fleshing the idea out a bit more.

Paolo