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Diffstat (limited to '')
-rw-r--r-- | library/alloc/src/collections/btree/mem.rs | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/library/alloc/src/collections/btree/mem.rs b/library/alloc/src/collections/btree/mem.rs new file mode 100644 index 000000000..e1363d1ae --- /dev/null +++ b/library/alloc/src/collections/btree/mem.rs @@ -0,0 +1,35 @@ +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. +#[allow(dead_code)] // keep as illustration and for future use +#[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 +} |