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impl Seek for Empty

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Fix #78029
This commit is contained in:
oberien 2020-10-17 12:08:59 +02:00
parent bf469eb6c2
commit f1cd17961c
2 changed files with 37 additions and 2 deletions
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17
library/std/src/io/util.rs
View File

@ -4,7 +4,7 @@
mod tests;
use crate::fmt;
use crate::io::{self, BufRead, Initializer, IoSlice, IoSliceMut, Read, Write};
use crate::io::{self, BufRead, Initializer, IoSlice, IoSliceMut, Read, Seek, SeekFrom, Write};
/// A reader which is always at EOF.
///
@ -58,6 +58,21 @@ impl BufRead for Empty {
fn consume(&mut self, _n: usize) {}
}
#[stable(feature = "empty_seek", since = "1.51.0")]
impl Seek for Empty {
fn seek(&mut self, _pos: SeekFrom) -> io::Result<u64> {
Ok(0)
}
fn stream_len(&mut self) -> io::Result<u64> {
Ok(0)
}
fn stream_position(&mut self) -> io::Result<u64> {
Ok(0)
}
}
#[stable(feature = "std_debug", since = "1.16.0")]
impl fmt::Debug for Empty {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

22
library/std/src/io/util/tests.rs
View File

@ -1,5 +1,5 @@
use crate::io::prelude::*;
use crate::io::{copy, empty, repeat, sink, Empty, Repeat, Sink};
use crate::io::{copy, empty, repeat, sink, Empty, Repeat, SeekFrom, Sink};
#[test]
fn copy_copies() {
@ -29,6 +29,26 @@ fn empty_reads() {
assert_eq!(e.by_ref().read(&mut [0; 1024]).unwrap(), 0);
}
#[test]
fn empty_seeks() {
let mut e = empty();
assert!(matches!(e.seek(SeekFrom::Start(0)), Ok(0)));
assert!(matches!(e.seek(SeekFrom::Start(1)), Ok(0)));
assert!(matches!(e.seek(SeekFrom::Start(u64::MAX)), Ok(0)));
assert!(matches!(e.seek(SeekFrom::End(i64::MIN)), Ok(0)));
assert!(matches!(e.seek(SeekFrom::End(-1)), Ok(0)));
assert!(matches!(e.seek(SeekFrom::End(0)), Ok(0)));
assert!(matches!(e.seek(SeekFrom::End(1)), Ok(0)));
assert!(matches!(e.seek(SeekFrom::End(i64::MAX)), Ok(0)));
assert!(matches!(e.seek(SeekFrom::Current(i64::MIN)), Ok(0)));
assert!(matches!(e.seek(SeekFrom::Current(-1)), Ok(0)));
assert!(matches!(e.seek(SeekFrom::Current(0)), Ok(0)));
assert!(matches!(e.seek(SeekFrom::Current(1)), Ok(0)));
assert!(matches!(e.seek(SeekFrom::Current(i64::MAX)), Ok(0)));
}
#[test]
fn repeat_repeats() {
let mut r = repeat(4);