New upstream version 1.52.0~beta.3+dfsg1

[rustc.git] / library / std / src / io / tests.rs

diff --git a/library/std/src/io/tests.rs b/library/std/src/io/tests.rs
index f176c2f088cb314e850d11057fbd3f4f120b5773..a85dd0d98271565ca6d6fb9cf69e54d3ba22aa7d 100644 (file)
--- a/library/std/src/io/tests.rs
+++ b/library/std/src/io/tests.rs
@@ -1,7 +1,7 @@
 use super::{repeat, Cursor, SeekFrom};
 use crate::cmp::{self, min};
 use crate::io::{self, IoSlice, IoSliceMut};
-use crate::io::{BufRead, Read, Seek, Write};
+use crate::io::{BufRead, BufReader, Read, Seek, Write};
 use crate::ops::Deref;
 
 #[test]
@@ -198,6 +198,53 @@ fn chain_bufread() {
     cmp_bufread(chain1, chain2, &testdata[..]);
 }
 
+#[test]
+fn bufreader_size_hint() {
+    let testdata = b"ABCDEFGHIJKL";
+    let mut buf_reader = BufReader::new(&testdata[..]);
+    assert_eq!(buf_reader.buffer().len(), 0);
+
+    let buffer_length = testdata.len();
+    buf_reader.fill_buf().unwrap();
+
+    // Check that size hint matches buffer contents
+    let mut buffered_bytes = buf_reader.bytes();
+    let (lower_bound, _upper_bound) = buffered_bytes.size_hint();
+    assert_eq!(lower_bound, buffer_length);
+
+    // Check that size hint matches buffer contents after advancing
+    buffered_bytes.next().unwrap().unwrap();
+    let (lower_bound, _upper_bound) = buffered_bytes.size_hint();
+    assert_eq!(lower_bound, buffer_length - 1);
+}
+
+#[test]
+fn empty_size_hint() {
+    let size_hint = io::empty().bytes().size_hint();
+    assert_eq!(size_hint, (0, Some(0)));
+}
+
+#[test]
+fn chain_empty_size_hint() {
+    let chain = io::empty().chain(io::empty());
+    let size_hint = chain.bytes().size_hint();
+    assert_eq!(size_hint, (0, Some(0)));
+}
+
+#[test]
+fn chain_size_hint() {
+    let testdata = b"ABCDEFGHIJKL";
+    let mut buf_reader_1 = BufReader::new(&testdata[..6]);
+    let mut buf_reader_2 = BufReader::new(&testdata[6..]);
+
+    buf_reader_1.fill_buf().unwrap();
+    buf_reader_2.fill_buf().unwrap();
+
+    let chain = buf_reader_1.chain(buf_reader_2);
+    let size_hint = chain.bytes().size_hint();
+    assert_eq!(size_hint, (testdata.len(), None));
+}
+
 #[test]
 fn chain_zero_length_read_is_not_eof() {
     let a = b"A";