Method try_writable

crates/stdlib/src/mmap.rs:891–908

(
            &self,
            vm: &VirtualMachine,
            f: impl FnOnce(&mut [u8]) -> R,
        )

        #[inline]
        fn try_writable<R>(
            &self,
            vm: &VirtualMachine,
            f: impl FnOnce(&mut [u8]) -> R,
        ) -> PyResult<R> {
            if matches!(self.access, AccessMode::Read) {
                return Err(vm.new_type_error("mmap can't modify a readonly memory map."));
            }

            match self.check_valid(vm)?.deref_mut().as_mut().unwrap() {
                MmapObj::Write(mmap) => Ok(f(&mut mmap[..])),
                #[cfg(windows)]
                MmapObj::Named(named) => Ok(f(unsafe {
                    core::slice::from_raw_parts_mut(named.view_ptr, named.len)
                })),
                _ => unreachable!("already checked"),
            }
        }

        fn check_valid(&self, vm: &VirtualMachine) -> PyResult<PyMutexGuard<'_, Option<MmapObj>>> {
            let m = self.mmap.lock();