45 lines
1.1 KiB
Rust
45 lines
1.1 KiB
Rust
// run-pass
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// Test that an `&mut self` method, when invoked on a place whose
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// type is `&mut [u8]`, passes in a pointer to the place and not a
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// temporary. Issue #19147.
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use std::slice;
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use std::cmp;
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trait MyWriter {
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fn my_write(&mut self, buf: &[u8]) -> Result<(), ()>;
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}
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impl<'a> MyWriter for &'a mut [u8] {
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fn my_write(&mut self, buf: &[u8]) -> Result<(), ()> {
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let amt = cmp::min(self.len(), buf.len());
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self[..amt].clone_from_slice(&buf[..amt]);
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let write_len = buf.len();
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unsafe {
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*self = slice::from_raw_parts_mut(
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self.as_mut_ptr().add(write_len),
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self.len() - write_len
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);
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}
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Ok(())
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}
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}
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fn main() {
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let mut buf = [0; 6];
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{
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let mut writer: &mut [_] = &mut buf;
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writer.my_write(&[0, 1, 2]).unwrap();
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writer.my_write(&[3, 4, 5]).unwrap();
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}
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// If `my_write` is not modifying `buf` in place, then we will
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// wind up with `[3, 4, 5, 0, 0, 0]` because the first call to
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// `my_write()` doesn't update the starting point for the write.
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assert_eq!(buf, [0, 1, 2, 3, 4, 5]);
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}
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