Rollup merge of #120900 - marcospb19:std-use-seek-stream-position, r=joshtriplett

std: use `stream_position` where applicable

by replacing `seek(SeekFrom::Current(0))` calls

3 files changed, 31 insertions, 29 deletions

diff --git a/library/std/src/fs.rs b/library/std/src/fs.rs
index 1b8fafd0089..8a24949631c 100644
--- a/library/std/src/fs.rs
+++ b/library/std/src/fs.rs
@@ -993,7 +993,7 @@ impl OpenOptions {
     /// If a file is opened with both read and append access, beware that after
     /// opening, and after every write, the position for reading may be set at the
     /// end of the file. So, before writing, save the current position (using
-    /// <code>[seek]\([SeekFrom]::[Current]\(0))</code>), and restore it before the next read.
+    /// <code>[Seek]::[stream_position]</code>), and restore it before the next read.
     ///
     /// ## Note
     ///
@@ -1002,8 +1002,7 @@ impl OpenOptions {
     ///
     /// [`write()`]: Write::write "io::Write::write"
     /// [`flush()`]: Write::flush "io::Write::flush"
-    /// [seek]: Seek::seek "io::Seek::seek"
-    /// [Current]: SeekFrom::Current "io::SeekFrom::Current"
+    /// [stream_position]: Seek::stream_position "io::Seek::stream_position"
     ///
     /// # Examples
     ///
diff --git a/library/std/src/fs/tests.rs b/library/std/src/fs/tests.rs
index 6a92832fcdb..ff399a0acd5 100644
--- a/library/std/src/fs/tests.rs
+++ b/library/std/src/fs/tests.rs
@@ -187,9 +187,9 @@ fn file_test_io_seek_and_tell_smoke_test() {
     {
         let mut read_stream = check!(File::open(filename));
         check!(read_stream.seek(SeekFrom::Start(set_cursor)));
-        tell_pos_pre_read = check!(read_stream.seek(SeekFrom::Current(0)));
+        tell_pos_pre_read = check!(read_stream.stream_position());
         check!(read_stream.read(&mut read_mem));
-        tell_pos_post_read = check!(read_stream.seek(SeekFrom::Current(0)));
+        tell_pos_post_read = check!(read_stream.stream_position());
     }
     check!(fs::remove_file(filename));
     let read_str = str::from_utf8(&read_mem).unwrap();
@@ -284,42 +284,42 @@ fn file_test_io_read_write_at() {
         let oo = OpenOptions::new().create_new(true).write(true).read(true).clone();
         let mut rw = check!(oo.open(&filename));
         assert_eq!(check!(rw.write_at(write1.as_bytes(), 5)), write1.len());
-        assert_eq!(check!(rw.seek(SeekFrom::Current(0))), 0);
+        assert_eq!(check!(rw.stream_position()), 0);
         assert_eq!(check!(rw.read_at(&mut buf, 5)), write1.len());
         assert_eq!(str::from_utf8(&buf[..write1.len()]), Ok(write1));
-        assert_eq!(check!(rw.seek(SeekFrom::Current(0))), 0);
+        assert_eq!(check!(rw.stream_position()), 0);
         assert_eq!(check!(rw.read_at(&mut buf[..write2.len()], 0)), write2.len());
         assert_eq!(str::from_utf8(&buf[..write2.len()]), Ok("\0\0\0\0\0"));
-        assert_eq!(check!(rw.seek(SeekFrom::Current(0))), 0);
+        assert_eq!(check!(rw.stream_position()), 0);
         assert_eq!(check!(rw.write(write2.as_bytes())), write2.len());
-        assert_eq!(check!(rw.seek(SeekFrom::Current(0))), 5);
+        assert_eq!(check!(rw.stream_position()), 5);
         assert_eq!(check!(rw.read(&mut buf)), write1.len());
         assert_eq!(str::from_utf8(&buf[..write1.len()]), Ok(write1));
-        assert_eq!(check!(rw.seek(SeekFrom::Current(0))), 9);
+        assert_eq!(check!(rw.stream_position()), 9);
         assert_eq!(check!(rw.read_at(&mut buf[..write2.len()], 0)), write2.len());
         assert_eq!(str::from_utf8(&buf[..write2.len()]), Ok(write2));
-        assert_eq!(check!(rw.seek(SeekFrom::Current(0))), 9);
+        assert_eq!(check!(rw.stream_position()), 9);
         assert_eq!(check!(rw.write_at(write3.as_bytes(), 9)), write3.len());
-        assert_eq!(check!(rw.seek(SeekFrom::Current(0))), 9);
+        assert_eq!(check!(rw.stream_position()), 9);
     }
     {
         let mut read = check!(File::open(&filename));
         assert_eq!(check!(read.read_at(&mut buf, 0)), content.len());
         assert_eq!(str::from_utf8(&buf[..content.len()]), Ok(content));
-        assert_eq!(check!(read.seek(SeekFrom::Current(0))), 0);
+        assert_eq!(check!(read.stream_position()), 0);
         assert_eq!(check!(read.seek(SeekFrom::End(-5))), 9);
         assert_eq!(check!(read.read_at(&mut buf, 0)), content.len());
         assert_eq!(str::from_utf8(&buf[..content.len()]), Ok(content));
-        assert_eq!(check!(read.seek(SeekFrom::Current(0))), 9);
+        assert_eq!(check!(read.stream_position()), 9);
         assert_eq!(check!(read.read(&mut buf)), write3.len());
         assert_eq!(str::from_utf8(&buf[..write3.len()]), Ok(write3));
-        assert_eq!(check!(read.seek(SeekFrom::Current(0))), 14);
+        assert_eq!(check!(read.stream_position()), 14);
         assert_eq!(check!(read.read_at(&mut buf, 0)), content.len());
         assert_eq!(str::from_utf8(&buf[..content.len()]), Ok(content));
-        assert_eq!(check!(read.seek(SeekFrom::Current(0))), 14);
+        assert_eq!(check!(read.stream_position()), 14);
         assert_eq!(check!(read.read_at(&mut buf, 14)), 0);
         assert_eq!(check!(read.read_at(&mut buf, 15)), 0);
-        assert_eq!(check!(read.seek(SeekFrom::Current(0))), 14);
+        assert_eq!(check!(read.stream_position()), 14);
     }
     check!(fs::remove_file(&filename));
 }
@@ -362,38 +362,38 @@ fn file_test_io_seek_read_write() {
         let oo = OpenOptions::new().create_new(true).write(true).read(true).clone();
         let mut rw = check!(oo.open(&filename));
         assert_eq!(check!(rw.seek_write(write1.as_bytes(), 5)), write1.len());
-        assert_eq!(check!(rw.seek(SeekFrom::Current(0))), 9);
+        assert_eq!(check!(rw.stream_position()), 9);
         assert_eq!(check!(rw.seek_read(&mut buf, 5)), write1.len());
         assert_eq!(str::from_utf8(&buf[..write1.len()]), Ok(write1));
-        assert_eq!(check!(rw.seek(SeekFrom::Current(0))), 9);
+        assert_eq!(check!(rw.stream_position()), 9);
         assert_eq!(check!(rw.seek(SeekFrom::Start(0))), 0);
         assert_eq!(check!(rw.write(write2.as_bytes())), write2.len());
-        assert_eq!(check!(rw.seek(SeekFrom::Current(0))), 5);
+        assert_eq!(check!(rw.stream_position()), 5);
         assert_eq!(check!(rw.read(&mut buf)), write1.len());
         assert_eq!(str::from_utf8(&buf[..write1.len()]), Ok(write1));
-        assert_eq!(check!(rw.seek(SeekFrom::Current(0))), 9);
+        assert_eq!(check!(rw.stream_position()), 9);
         assert_eq!(check!(rw.seek_read(&mut buf[..write2.len()], 0)), write2.len());
         assert_eq!(str::from_utf8(&buf[..write2.len()]), Ok(write2));
-        assert_eq!(check!(rw.seek(SeekFrom::Current(0))), 5);
+        assert_eq!(check!(rw.stream_position()), 5);
         assert_eq!(check!(rw.seek_write(write3.as_bytes(), 9)), write3.len());
-        assert_eq!(check!(rw.seek(SeekFrom::Current(0))), 14);
+        assert_eq!(check!(rw.stream_position()), 14);
     }
     {
         let mut read = check!(File::open(&filename));
         assert_eq!(check!(read.seek_read(&mut buf, 0)), content.len());
         assert_eq!(str::from_utf8(&buf[..content.len()]), Ok(content));
-        assert_eq!(check!(read.seek(SeekFrom::Current(0))), 14);
+        assert_eq!(check!(read.stream_position()), 14);
         assert_eq!(check!(read.seek(SeekFrom::End(-5))), 9);
         assert_eq!(check!(read.seek_read(&mut buf, 0)), content.len());
         assert_eq!(str::from_utf8(&buf[..content.len()]), Ok(content));
-        assert_eq!(check!(read.seek(SeekFrom::Current(0))), 14);
+        assert_eq!(check!(read.stream_position()), 14);
         assert_eq!(check!(read.seek(SeekFrom::End(-5))), 9);
         assert_eq!(check!(read.read(&mut buf)), write3.len());
         assert_eq!(str::from_utf8(&buf[..write3.len()]), Ok(write3));
-        assert_eq!(check!(read.seek(SeekFrom::Current(0))), 14);
+        assert_eq!(check!(read.stream_position()), 14);
         assert_eq!(check!(read.seek_read(&mut buf, 0)), content.len());
         assert_eq!(str::from_utf8(&buf[..content.len()]), Ok(content));
-        assert_eq!(check!(read.seek(SeekFrom::Current(0))), 14);
+        assert_eq!(check!(read.stream_position()), 14);
         assert_eq!(check!(read.seek_read(&mut buf, 14)), 0);
         assert_eq!(check!(read.seek_read(&mut buf, 15)), 0);
     }
diff --git a/library/std/src/io/buffered/tests.rs b/library/std/src/io/buffered/tests.rs
index 35a5291a347..ee0db30e22c 100644
--- a/library/std/src/io/buffered/tests.rs
+++ b/library/std/src/io/buffered/tests.rs
@@ -114,7 +114,7 @@ fn test_buffered_reader_seek() {
 
     assert_eq!(reader.seek(SeekFrom::Start(3)).ok(), Some(3));
     assert_eq!(reader.fill_buf().ok(), Some(&[0, 1][..]));
-    assert_eq!(reader.seek(SeekFrom::Current(0)).ok(), Some(3));
+    assert_eq!(reader.stream_position().ok(), Some(3));
     assert_eq!(reader.fill_buf().ok(), Some(&[0, 1][..]));
     assert_eq!(reader.seek(SeekFrom::Current(1)).ok(), Some(4));
     assert_eq!(reader.fill_buf().ok(), Some(&[1, 2][..]));
@@ -230,6 +230,9 @@ fn test_buffered_reader_seek_underflow() {
             Ok(len)
         }
     }
+    // note: this implementation of `Seek` is "broken" due to position
+    // wrapping, so calling `reader.seek(Current(0))` is semantically different
+    // than `reader.stream_position()`
     impl Seek for PositionReader {
         fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
             match pos {
@@ -374,7 +377,7 @@ fn test_buffered_writer_seek() {
     let mut w = BufWriter::with_capacity(3, io::Cursor::new(Vec::new()));
     w.write_all(&[0, 1, 2, 3, 4, 5]).unwrap();
     w.write_all(&[6, 7]).unwrap();
-    assert_eq!(w.seek(SeekFrom::Current(0)).ok(), Some(8));
+    assert_eq!(w.stream_position().ok(), Some(8));
     assert_eq!(&w.get_ref().get_ref()[..], &[0, 1, 2, 3, 4, 5, 6, 7][..]);
     assert_eq!(w.seek(SeekFrom::Start(2)).ok(), Some(2));
     w.write_all(&[8, 9]).unwrap();