Function overwrite 

pub unsafe fn overwrite(target_base: *mut u8, source: *const u8) -> bool

Copy all entries from source map to target map

Safety

• Both maps must be properly initialized with compatible layouts (capacity can differ)
• Target map must have sufficient capacity

Panics

Panics if the maps have incompatible layouts (different bucket sizes, key sizes, or value sizes)

Returns

true if the operation succeeded, false if the target has insufficient capacity