| // Copyright 2014 The Rust Project Developers. See the COPYRIGHT |
| // file at the top-level directory of this distribution and at |
| // http://rust-lang.org/COPYRIGHT. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| // Test that an `&mut self` method, when invoked on an lvalue whose |
| // type is `&mut [u8]`, passes in a pointer to the lvalue and not a |
| // temporary. Issue #19147. |
| |
| use std::slice; |
| use std::cmp; |
| |
| trait MyWriter { |
| fn my_write(&mut self, buf: &[u8]) -> Result<(), ()>; |
| } |
| |
| impl<'a> MyWriter for &'a mut [u8] { |
| fn my_write(&mut self, buf: &[u8]) -> Result<(), ()> { |
| let amt = cmp::min(self.len(), buf.len()); |
| self[..amt].clone_from_slice(&buf[..amt]); |
| |
| let write_len = buf.len(); |
| unsafe { |
| *self = slice::from_raw_parts_mut( |
| self.as_mut_ptr().offset(write_len as isize), |
| self.len() - write_len |
| ); |
| } |
| |
| Ok(()) |
| } |
| } |
| |
| fn main() { |
| let mut buf = [0; 6]; |
| |
| { |
| let mut writer: &mut [_] = &mut buf; |
| writer.my_write(&[0, 1, 2]).unwrap(); |
| writer.my_write(&[3, 4, 5]).unwrap(); |
| } |
| |
| // If `my_write` is not modifying `buf` in place, then we will |
| // wind up with `[3, 4, 5, 0, 0, 0]` because the first call to |
| // `my_write()` doesn't update the starting point for the write. |
| |
| assert_eq!(buf, [0, 1, 2, 3, 4, 5]); |
| } |