mem.rs - source
Description: Source of the Rust file `library/alloc/src/collections/btree/mem.rs`.
Keywords: rust, rustlang, rust-lang

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    use core::intrinsics;
    use core::mem;
    use core::ptr;

    /// This replaces the value behind the `v` unique reference by calling the
    /// relevant function.
    ///
    /// If a panic occurs in the `change` closure, the entire process will be aborted.
    #[inline]
    pub fn take_mut<T>(v: &mut T, change: impl FnOnce(T) -> T) {
        replace(v, |value| (change(value), ()))
    }

    /// This replaces the value behind the `v` unique reference by calling the
    /// relevant function, and returns a result obtained along the way.
    ///
    /// If a panic occurs in the `change` closure, the entire process will be aborted.
    #[inline]
    pub fn replace<T, R>(v: &mut T, change: impl FnOnce(T) -> (T, R)) -> R {
        struct PanicGuard;
        impl Drop for PanicGuard {
            fn drop(&mut self) {
                intrinsics::abort()
            }
        }
        let guard = PanicGuard;
        let value = unsafe { ptr::read(v) };
        let (new_value, ret) = change(value);
        unsafe {
            ptr::write(v, new_value);
        }
        mem::forget(guard);
        ret
    }