pub unsafe fn transmute_copy<T, U>(src: &T) -> U
Expand description
Interprets src
as having type &U
, and then reads src
without moving
the contained value.
This function will unsafely assume the pointer src
is valid for size_of::<U>
bytes by transmuting &T
to &U
and then reading the &U
(except that this is done in a way
that is correct even when &U
makes stricter alignment requirements than &T
). It will also
unsafely create a copy of the contained value instead of moving out of src
.
It is not a compile-time error if T
and U
have different sizes, but it
is highly encouraged to only invoke this function where T
and U
have the
same size. This function triggers undefined behavior if U
is larger than
T
.
Examples
use std::mem;
#[repr(packed)]
struct Foo {
bar: u8,
}
let foo_array = [10u8];
unsafe {
// Copy the data from 'foo_array' and treat it as a 'Foo'
let mut foo_struct: Foo = mem::transmute_copy(&foo_array);
assert_eq!(foo_struct.bar, 10);
// Modify the copied data
foo_struct.bar = 20;
assert_eq!(foo_struct.bar, 20);
}
// The contents of 'foo_array' should not have changed
assert_eq!(foo_array, [10]);
Run