1 // Copyright 2013 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 // ignore-lexer-test FIXME #15883
13 //! Buffering wrappers for I/O traits
19 use error::Error as StdError;
22 use io::{self, Cursor, DEFAULT_BUF_SIZE, Error, ErrorKind};
25 /// Wraps a `Read` and buffers input from it
27 /// It can be excessively inefficient to work directly with a `Read` instance.
28 /// For example, every call to `read` on `TcpStream` results in a system call.
29 /// A `BufReader` performs large, infrequent reads on the underlying `Read`
30 /// and maintains an in-memory buffer of the results.
31 pub struct BufReader<R> {
36 impl<R: Read> BufReader<R> {
37 /// Creates a new `BufReader` with a default buffer capacity
38 pub fn new(inner: R) -> BufReader<R> {
39 BufReader::with_capacity(DEFAULT_BUF_SIZE, inner)
42 /// Creates a new `BufReader` with the specified buffer capacity
43 pub fn with_capacity(cap: usize, inner: R) -> BufReader<R> {
46 buf: Cursor::new(Vec::with_capacity(cap)),
50 /// Gets a reference to the underlying reader.
51 pub fn get_ref<'a>(&self) -> &R { &self.inner }
53 /// Gets a mutable reference to the underlying reader.
57 /// It is inadvisable to directly read from the underlying reader.
58 pub fn get_mut(&mut self) -> &mut R { &mut self.inner }
60 /// Unwraps this `BufReader`, returning the underlying reader.
62 /// Note that any leftover data in the internal buffer is lost.
63 pub fn into_inner(self) -> R { self.inner }
66 impl<R: Read> Read for BufReader<R> {
67 fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
68 // If we don't have any buffered data and we're doing a massive read
69 // (larger than our internal buffer), bypass our internal buffer
71 if self.buf.get_ref().len() == self.buf.position() as usize &&
72 buf.len() >= self.buf.get_ref().capacity() {
73 return self.inner.read(buf);
75 try!(self.fill_buf());
80 impl<R: Read> BufRead for BufReader<R> {
81 fn fill_buf(&mut self) -> io::Result<&[u8]> {
82 // If we've reached the end of our internal buffer then we need to fetch
83 // some more data from the underlying reader.
84 if self.buf.position() as usize == self.buf.get_ref().len() {
85 self.buf.set_position(0);
86 let v = self.buf.get_mut();
88 let inner = &mut self.inner;
89 try!(super::with_end_to_cap(v, |b| inner.read(b)));
94 fn consume(&mut self, amt: uint) {
99 #[stable(feature = "rust1", since = "1.0.0")]
100 impl<R> fmt::Debug for BufReader<R> where R: fmt::Debug {
101 fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
102 write!(fmt, "BufReader {{ reader: {:?}, buffer: {}/{} }}",
103 self.inner, self.buf.position(), self.buf.get_ref().len())
107 /// Wraps a Writer and buffers output to it
109 /// It can be excessively inefficient to work directly with a `Write`. For
110 /// example, every call to `write` on `TcpStream` results in a system call. A
111 /// `BufWriter` keeps an in memory buffer of data and writes it to the
112 /// underlying `Write` in large, infrequent batches.
114 /// This writer will be flushed when it is dropped.
115 pub struct BufWriter<W> {
120 /// An error returned by `into_inner` which indicates whether a flush error
123 pub struct IntoInnerError<W>(W, Error);
125 impl<W: Write> BufWriter<W> {
126 /// Creates a new `BufWriter` with a default buffer capacity
127 pub fn new(inner: W) -> BufWriter<W> {
128 BufWriter::with_capacity(DEFAULT_BUF_SIZE, inner)
131 /// Creates a new `BufWriter` with the specified buffer capacity
132 pub fn with_capacity(cap: usize, inner: W) -> BufWriter<W> {
135 buf: Vec::with_capacity(cap),
139 fn flush_buf(&mut self) -> io::Result<()> {
141 let len = self.buf.len();
142 let mut ret = Ok(());
143 while written < len {
144 match self.inner.as_mut().unwrap().write(&self.buf[written..]) {
146 ret = Err(Error::new(ErrorKind::WriteZero,
147 "failed to flush", None));
150 Ok(n) => written += n,
151 Err(e) => { ret = Err(e); break }
156 // NB: would be better expressed as .remove(0..n) if it existed
158 ptr::copy_memory(self.buf.as_mut_ptr(),
159 self.buf.as_ptr().offset(written as isize),
163 self.buf.truncate(len - written);
167 /// Gets a reference to the underlying writer.
168 pub fn get_ref(&self) -> &W { self.inner.as_ref().unwrap() }
170 /// Gets a mutable reference to the underlying write.
174 /// It is inadvisable to directly read from the underlying writer.
175 pub fn get_mut(&mut self) -> &mut W { self.inner.as_mut().unwrap() }
177 /// Unwraps this `BufWriter`, returning the underlying writer.
179 /// The buffer is flushed before returning the writer.
180 pub fn into_inner(mut self) -> Result<W, IntoInnerError<BufWriter<W>>> {
181 match self.flush_buf() {
182 Err(e) => Err(IntoInnerError(self, e)),
183 Ok(()) => Ok(self.inner.take().unwrap())
188 impl<W: Write> Write for BufWriter<W> {
189 fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
190 if self.buf.len() + buf.len() > self.buf.capacity() {
191 try!(self.flush_buf());
193 if buf.len() >= self.buf.capacity() {
194 self.inner.as_mut().unwrap().write(buf)
196 let amt = cmp::min(buf.len(), self.buf.capacity());
197 Write::write(&mut self.buf, &buf[..amt])
200 fn flush(&mut self) -> io::Result<()> {
201 self.flush_buf().and_then(|()| self.get_mut().flush())
205 #[stable(feature = "rust1", since = "1.0.0")]
206 impl<W> fmt::Debug for BufWriter<W> where W: fmt::Debug {
207 fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
208 write!(fmt, "BufWriter {{ writer: {:?}, buffer: {}/{} }}",
209 self.inner.as_ref().unwrap(), self.buf.len(), self.buf.capacity())
214 impl<W: Write> Drop for BufWriter<W> {
216 if self.inner.is_some() {
217 // dtors should not panic, so we ignore a failed flush
218 let _r = self.flush_buf();
223 impl<W> IntoInnerError<W> {
224 /// Returns the error which caused the call to `into_inner` to fail.
226 /// This error was returned when attempting to flush the internal buffer.
227 pub fn error(&self) -> &Error { &self.1 }
229 /// Returns the underlying `BufWriter` instance which generated the error.
231 /// The returned object can be used to retry a flush or re-inspect the
233 pub fn into_inner(self) -> W { self.0 }
236 impl<W> FromError<IntoInnerError<W>> for Error {
237 fn from_error(iie: IntoInnerError<W>) -> Error { iie.1 }
240 impl<W> StdError for IntoInnerError<W> {
241 fn description(&self) -> &str { self.error().description() }
244 impl<W> fmt::Display for IntoInnerError<W> {
245 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
250 /// Wraps a Writer and buffers output to it, flushing whenever a newline
251 /// (`0x0a`, `'\n'`) is detected.
253 /// This writer will be flushed when it is dropped.
254 pub struct LineWriter<W> {
258 impl<W: Write> LineWriter<W> {
259 /// Creates a new `LineWriter`
260 pub fn new(inner: W) -> LineWriter<W> {
261 // Lines typically aren't that long, don't use a giant buffer
262 LineWriter { inner: BufWriter::with_capacity(1024, inner) }
265 /// Gets a reference to the underlying writer.
267 /// This type does not expose the ability to get a mutable reference to the
268 /// underlying reader because that could possibly corrupt the buffer.
269 pub fn get_ref<'a>(&'a self) -> &'a W { self.inner.get_ref() }
271 /// Unwraps this `LineWriter`, returning the underlying writer.
273 /// The internal buffer is flushed before returning the writer.
274 pub fn into_inner(self) -> Result<W, IntoInnerError<LineWriter<W>>> {
275 self.inner.into_inner().map_err(|IntoInnerError(buf, e)| {
276 IntoInnerError(LineWriter { inner: buf }, e)
281 impl<W: Write> Write for LineWriter<W> {
282 fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
283 match buf.rposition_elem(&b'\n') {
285 let n = try!(self.inner.write(&buf[..i + 1]));
286 if n != i + 1 { return Ok(n) }
287 try!(self.inner.flush());
288 self.inner.write(&buf[i + 1..]).map(|i| n + i)
290 None => self.inner.write(buf),
294 fn flush(&mut self) -> io::Result<()> { self.inner.flush() }
297 #[stable(feature = "rust1", since = "1.0.0")]
298 impl<W> fmt::Debug for LineWriter<W> where W: fmt::Debug {
299 fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
300 write!(fmt, "LineWriter {{ writer: {:?}, buffer: {}/{} }}",
301 self.inner.inner, self.inner.buf.len(),
302 self.inner.buf.capacity())
306 struct InternalBufWriter<W>(BufWriter<W>);
308 impl<W> InternalBufWriter<W> {
309 fn get_mut(&mut self) -> &mut BufWriter<W> {
310 let InternalBufWriter(ref mut w) = *self;
315 impl<W: Read> Read for InternalBufWriter<W> {
316 fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
317 self.get_mut().inner.as_mut().unwrap().read(buf)
321 /// Wraps a Stream and buffers input and output to and from it.
323 /// It can be excessively inefficient to work directly with a `Stream`. For
324 /// example, every call to `read` or `write` on `TcpStream` results in a system
325 /// call. A `BufStream` keeps in memory buffers of data, making large,
326 /// infrequent calls to `read` and `write` on the underlying `Stream`.
328 /// The output half will be flushed when this stream is dropped.
329 pub struct BufStream<S> {
330 inner: BufReader<InternalBufWriter<S>>
333 impl<S: Read + Write> BufStream<S> {
334 /// Creates a new buffered stream with explicitly listed capacities for the
335 /// reader/writer buffer.
336 pub fn with_capacities(reader_cap: usize, writer_cap: usize, inner: S)
338 let writer = BufWriter::with_capacity(writer_cap, inner);
339 let internal_writer = InternalBufWriter(writer);
340 let reader = BufReader::with_capacity(reader_cap, internal_writer);
341 BufStream { inner: reader }
344 /// Creates a new buffered stream with the default reader/writer buffer
346 pub fn new(inner: S) -> BufStream<S> {
347 BufStream::with_capacities(DEFAULT_BUF_SIZE, DEFAULT_BUF_SIZE, inner)
350 /// Gets a reference to the underlying stream.
351 pub fn get_ref(&self) -> &S {
352 let InternalBufWriter(ref w) = self.inner.inner;
356 /// Gets a mutable reference to the underlying stream.
360 /// It is inadvisable to read directly from or write directly to the
361 /// underlying stream.
362 pub fn get_mut(&mut self) -> &mut S {
363 let InternalBufWriter(ref mut w) = self.inner.inner;
367 /// Unwraps this `BufStream`, returning the underlying stream.
369 /// The internal buffer is flushed before returning the stream. Any leftover
370 /// data in the read buffer is lost.
371 pub fn into_inner(self) -> Result<S, IntoInnerError<BufStream<S>>> {
372 let BufReader { inner: InternalBufWriter(w), buf } = self.inner;
373 w.into_inner().map_err(|IntoInnerError(w, e)| {
374 IntoInnerError(BufStream {
375 inner: BufReader { inner: InternalBufWriter(w), buf: buf },
381 impl<S: Read + Write> BufRead for BufStream<S> {
382 fn fill_buf(&mut self) -> io::Result<&[u8]> { self.inner.fill_buf() }
383 fn consume(&mut self, amt: uint) { self.inner.consume(amt) }
386 impl<S: Read + Write> Read for BufStream<S> {
387 fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
392 impl<S: Read + Write> Write for BufStream<S> {
393 fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
394 self.inner.inner.get_mut().write(buf)
396 fn flush(&mut self) -> io::Result<()> {
397 self.inner.inner.get_mut().flush()
401 #[stable(feature = "rust1", since = "1.0.0")]
402 impl<S> fmt::Debug for BufStream<S> where S: fmt::Debug {
403 fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
404 let reader = &self.inner;
405 let writer = &self.inner.inner.0;
406 write!(fmt, "BufStream {{ stream: {:?}, write_buffer: {}/{}, read_buffer: {}/{} }}",
408 writer.buf.len(), writer.buf.capacity(),
409 reader.buf.position(), reader.buf.get_ref().len())
417 use io::{self, BufReader, BufWriter, BufStream, Cursor, LineWriter};
420 /// A dummy reader intended at testing short-reads propagation.
421 pub struct ShortReader {
425 impl Read for ShortReader {
426 fn read(&mut self, _: &mut [u8]) -> io::Result<usize> {
427 if self.lengths.is_empty() {
430 Ok(self.lengths.remove(0))
436 fn test_buffered_reader() {
437 let inner: &[u8] = &[5, 6, 7, 0, 1, 2, 3, 4];
438 let mut reader = BufReader::with_capacity(2, inner);
440 let mut buf = [0, 0, 0];
441 let nread = reader.read(&mut buf);
442 assert_eq!(Ok(3), nread);
443 let b: &[_] = &[5, 6, 7];
446 let mut buf = [0, 0];
447 let nread = reader.read(&mut buf);
448 assert_eq!(Ok(2), nread);
449 let b: &[_] = &[0, 1];
453 let nread = reader.read(&mut buf);
454 assert_eq!(Ok(1), nread);
458 let mut buf = [0, 0, 0];
459 let nread = reader.read(&mut buf);
460 assert_eq!(Ok(1), nread);
461 let b: &[_] = &[3, 0, 0];
464 let nread = reader.read(&mut buf);
465 assert_eq!(Ok(1), nread);
466 let b: &[_] = &[4, 0, 0];
469 assert_eq!(reader.read(&mut buf), Ok(0));
473 fn test_buffered_writer() {
474 let inner = Vec::new();
475 let mut writer = BufWriter::with_capacity(2, inner);
477 writer.write(&[0, 1]).unwrap();
478 assert_eq!(*writer.get_ref(), [0, 1]);
480 writer.write(&[2]).unwrap();
481 assert_eq!(*writer.get_ref(), [0, 1]);
483 writer.write(&[3]).unwrap();
484 assert_eq!(*writer.get_ref(), [0, 1]);
486 writer.flush().unwrap();
487 assert_eq!(*writer.get_ref(), [0, 1, 2, 3]);
489 writer.write(&[4]).unwrap();
490 writer.write(&[5]).unwrap();
491 assert_eq!(*writer.get_ref(), [0, 1, 2, 3]);
493 writer.write(&[6]).unwrap();
494 assert_eq!(*writer.get_ref(), [0, 1, 2, 3, 4, 5]);
496 writer.write(&[7, 8]).unwrap();
497 assert_eq!(*writer.get_ref(), [0, 1, 2, 3, 4, 5, 6, 7, 8]);
499 writer.write(&[9, 10, 11]).unwrap();
500 let a: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11];
501 assert_eq!(*writer.get_ref(), [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]);
503 writer.flush().unwrap();
504 assert_eq!(*writer.get_ref(), [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]);
508 fn test_buffered_writer_inner_flushes() {
509 let mut w = BufWriter::with_capacity(3, Vec::new());
510 w.write(&[0, 1]).unwrap();
511 assert_eq!(*w.get_ref(), []);
512 let w = w.into_inner().unwrap();
513 assert_eq!(w, [0, 1]);
516 // This is just here to make sure that we don't infinite loop in the
517 // newtype struct autoderef weirdness
519 fn test_buffered_stream() {
523 fn write(&mut self, b: &[u8]) -> io::Result<usize> { Ok(b.len()) }
524 fn flush(&mut self) -> io::Result<()> { Ok(()) }
528 fn read(&mut self, _: &mut [u8]) -> io::Result<usize> { Ok(0) }
531 let mut stream = BufStream::new(S);
532 assert_eq!(stream.read(&mut [0; 10]), Ok(0));
533 stream.write(&[0; 10]).unwrap();
534 stream.flush().unwrap();
538 fn test_read_until() {
539 let inner: &[u8] = &[0, 1, 2, 1, 0];
540 let mut reader = BufReader::with_capacity(2, inner);
541 let mut v = Vec::new();
542 reader.read_until(0, &mut v).unwrap();
545 reader.read_until(2, &mut v).unwrap();
546 assert_eq!(v, [1, 2]);
548 reader.read_until(1, &mut v).unwrap();
551 reader.read_until(8, &mut v).unwrap();
554 reader.read_until(9, &mut v).unwrap();
559 fn test_line_buffer() {
560 let mut writer = LineWriter::new(Vec::new());
561 writer.write(&[0]).unwrap();
562 assert_eq!(*writer.get_ref(), []);
563 writer.write(&[1]).unwrap();
564 assert_eq!(*writer.get_ref(), []);
565 writer.flush().unwrap();
566 assert_eq!(*writer.get_ref(), [0, 1]);
567 writer.write(&[0, b'\n', 1, b'\n', 2]).unwrap();
568 assert_eq!(*writer.get_ref(), [0, 1, 0, b'\n', 1, b'\n']);
569 writer.flush().unwrap();
570 assert_eq!(*writer.get_ref(), [0, 1, 0, b'\n', 1, b'\n', 2]);
571 writer.write(&[3, b'\n']).unwrap();
572 assert_eq!(*writer.get_ref(), [0, 1, 0, b'\n', 1, b'\n', 2, 3, b'\n']);
576 fn test_read_line() {
577 let in_buf = b"a\nb\nc";
578 let mut reader = BufReader::with_capacity(2, in_buf);
579 let mut s = String::new();
580 reader.read_line(&mut s).unwrap();
581 assert_eq!(s, "a\n");
583 reader.read_line(&mut s).unwrap();
584 assert_eq!(s, "b\n");
586 reader.read_line(&mut s).unwrap();
589 reader.read_line(&mut s).unwrap();
595 let in_buf = b"a\nb\nc";
596 let mut reader = BufReader::with_capacity(2, in_buf);
597 let mut it = reader.lines();
598 assert_eq!(it.next(), Some(Ok("a".to_string())));
599 assert_eq!(it.next(), Some(Ok("b".to_string())));
600 assert_eq!(it.next(), Some(Ok("c".to_string())));
601 assert_eq!(it.next(), None);
605 fn test_short_reads() {
606 let inner = ShortReader{lengths: vec![0, 1, 2, 0, 1, 0]};
607 let mut reader = BufReader::new(inner);
608 let mut buf = [0, 0];
609 assert_eq!(reader.read(&mut buf), Ok(0));
610 assert_eq!(reader.read(&mut buf), Ok(1));
611 assert_eq!(reader.read(&mut buf), Ok(2));
612 assert_eq!(reader.read(&mut buf), Ok(0));
613 assert_eq!(reader.read(&mut buf), Ok(1));
614 assert_eq!(reader.read(&mut buf), Ok(0));
615 assert_eq!(reader.read(&mut buf), Ok(0));
619 fn read_char_buffered() {
620 let buf = [195u8, 159u8];
621 let mut reader = BufReader::with_capacity(1, &buf[]);
622 assert_eq!(reader.chars().next(), Some(Ok('ß')));
627 let buf = [195u8, 159u8, b'a'];
628 let mut reader = BufReader::with_capacity(1, &buf[]);
629 let mut it = reader.chars();
630 assert_eq!(it.next(), Some(Ok('ß')));
631 assert_eq!(it.next(), Some(Ok('a')));
632 assert_eq!(it.next(), None);
637 fn dont_panic_in_drop_on_panicked_flush() {
638 struct FailFlushWriter;
640 impl Write for FailFlushWriter {
641 fn write(&mut self, buf: &[u8]) -> io::Result<usize> { Ok(buf.len()) }
642 fn flush(&mut self) -> io::Result<()> {
643 Err(io::Error::last_os_error())
647 let writer = FailFlushWriter;
648 let _writer = BufWriter::new(writer);
650 // If writer panics *again* due to the flush error then the process will
656 fn bench_buffered_reader(b: &mut test::Bencher) {
658 BufReader::new(io::empty())
663 fn bench_buffered_writer(b: &mut test::Bencher) {
665 BufWriter::new(io::sink())
670 fn bench_buffered_stream(b: &mut test::Bencher) {
671 let mut buf = Cursor::new(Vec::new());
673 BufStream::new(&mut buf);