Method read

crates/stdlib/src/mmap.rs:1106–1135

(&self, n: OptionalArg<PyObjectRef>, vm: &VirtualMachine)

        #[pymethod]
        fn read(&self, n: OptionalArg<PyObjectRef>, vm: &VirtualMachine) -> PyResult<PyBytesRef> {
            let num_bytes = n
                .map(|obj| {
                    let class = obj.class().to_owned();
                    obj.try_into_value::<Option<isize>>(vm).map_err(|_| {
                        vm.new_type_error(format!(
                            "read argument must be int or None, not {}",
                            class.name()
                        ))
                    })
                })
                .transpose()?
                .flatten();
            let mmap = self.check_valid(vm)?;
            let pos = self.pos();
            let remaining = self.__len__().saturating_sub(pos);
            let num_bytes = num_bytes
                .filter(|&n| n >= 0 && (n as usize) <= remaining)
                .map(|n| n as usize)
                .unwrap_or(remaining);

            let end_pos = pos + num_bytes;
            let bytes = mmap.deref().as_ref().unwrap().as_slice()[pos..end_pos].to_vec();

            let result = PyBytes::from(bytes).into_ref(&vm.ctx);

            self.advance_pos(num_bytes);

            Ok(result)
        }

        #[pymethod]
        fn read_byte(&self, vm: &VirtualMachine) -> PyResult<PyIntRef> {