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
16 use io::{Reader, Writer, Stream, Buffer, DEFAULT_BUF_SIZE, IoResult};
17 use iter::ExactSizeIterator;
20 use option::Option::{Some, None};
21 use result::Result::{Ok, Err};
22 use slice::{SliceExt};
26 /// Wraps a Reader and buffers input from it
28 /// It can be excessively inefficient to work directly with a `Reader`. For
29 /// example, every call to `read` on `TcpStream` results in a system call. A
30 /// `BufferedReader` performs large, infrequent reads on the underlying
31 /// `Reader` and maintains an in-memory buffer of the results.
36 /// use std::io::{BufferedReader, File};
38 /// let file = File::open(&Path::new("message.txt"));
39 /// let mut reader = BufferedReader::new(file);
41 /// let mut buf = [0; 100];
42 /// match reader.read(&mut buf) {
43 /// Ok(nread) => println!("Read {} bytes", nread),
44 /// Err(e) => println!("error reading: {}", e)
47 pub struct BufferedReader<R> {
54 impl<R: Reader> BufferedReader<R> {
55 /// Creates a new `BufferedReader` with the specified buffer capacity
56 pub fn with_capacity(cap: uint, inner: R) -> BufferedReader<R> {
57 // It's *much* faster to create an uninitialized buffer than it is to
58 // fill everything in with 0. This buffer is entirely an implementation
59 // detail and is never exposed, so we're safe to not initialize
60 // everything up-front. This allows creation of BufferedReader instances
61 // to be very cheap (large mallocs are not nearly as expensive as large
63 let mut buf = Vec::with_capacity(cap);
64 unsafe { buf.set_len(cap); }
73 /// Creates a new `BufferedReader` with a default buffer capacity
74 pub fn new(inner: R) -> BufferedReader<R> {
75 BufferedReader::with_capacity(DEFAULT_BUF_SIZE, inner)
78 /// Gets a reference to the underlying reader.
79 pub fn get_ref<'a>(&self) -> &R { &self.inner }
81 /// Gets a mutable reference to the underlying reader.
85 /// It is inadvisable to directly read from the underlying reader.
86 pub fn get_mut(&mut self) -> &mut R { &mut self.inner }
88 /// Unwraps this `BufferedReader`, returning the underlying reader.
90 /// Note that any leftover data in the internal buffer is lost.
91 pub fn into_inner(self) -> R { self.inner }
94 impl<R: Reader> Buffer for BufferedReader<R> {
95 fn fill_buf<'a>(&'a mut self) -> IoResult<&'a [u8]> {
96 if self.pos == self.cap {
97 self.cap = try!(self.inner.read(self.buf.as_mut_slice()));
100 Ok(self.buf[self.pos..self.cap])
103 fn consume(&mut self, amt: uint) {
105 assert!(self.pos <= self.cap);
109 impl<R: Reader> Reader for BufferedReader<R> {
110 fn read(&mut self, buf: &mut [u8]) -> IoResult<uint> {
111 if self.pos == self.cap && buf.len() >= self.buf.capacity() {
112 return self.inner.read(buf);
115 let available = try!(self.fill_buf());
116 let nread = cmp::min(available.len(), buf.len());
117 slice::bytes::copy_memory(buf, available[..nread]);
125 /// Wraps a Writer and buffers output to it
127 /// It can be excessively inefficient to work directly with a `Writer`. For
128 /// example, every call to `write` on `TcpStream` results in a system call. A
129 /// `BufferedWriter` keeps an in memory buffer of data and writes it to the
130 /// underlying `Writer` in large, infrequent batches.
132 /// This writer will be flushed when it is dropped.
137 /// use std::io::{BufferedWriter, File};
139 /// let file = File::create(&Path::new("message.txt")).unwrap();
140 /// let mut writer = BufferedWriter::new(file);
142 /// writer.write_str("hello, world").unwrap();
143 /// writer.flush().unwrap();
145 pub struct BufferedWriter<W> {
151 impl<W: Writer> BufferedWriter<W> {
152 /// Creates a new `BufferedWriter` with the specified buffer capacity
153 pub fn with_capacity(cap: uint, inner: W) -> BufferedWriter<W> {
154 // See comments in BufferedReader for why this uses unsafe code.
155 let mut buf = Vec::with_capacity(cap);
156 unsafe { buf.set_len(cap); }
164 /// Creates a new `BufferedWriter` with a default buffer capacity
165 pub fn new(inner: W) -> BufferedWriter<W> {
166 BufferedWriter::with_capacity(DEFAULT_BUF_SIZE, inner)
169 fn flush_buf(&mut self) -> IoResult<()> {
171 let ret = self.inner.as_mut().unwrap().write(self.buf[..self.pos]);
179 /// Gets a reference to the underlying writer.
180 pub fn get_ref(&self) -> &W { self.inner.as_ref().unwrap() }
182 /// Gets a mutable reference to the underlying write.
186 /// It is inadvisable to directly read from the underlying writer.
187 pub fn get_mut(&mut self) -> &mut W { self.inner.as_mut().unwrap() }
189 /// Unwraps this `BufferedWriter`, returning the underlying writer.
191 /// The buffer is flushed before returning the writer.
192 pub fn into_inner(mut self) -> W {
193 // FIXME(#12628): is panicking the right thing to do if flushing panicks?
194 self.flush_buf().unwrap();
195 self.inner.take().unwrap()
199 impl<W: Writer> Writer for BufferedWriter<W> {
200 fn write(&mut self, buf: &[u8]) -> IoResult<()> {
201 if self.pos + buf.len() > self.buf.len() {
202 try!(self.flush_buf());
205 if buf.len() > self.buf.len() {
206 self.inner.as_mut().unwrap().write(buf)
208 let dst = self.buf.slice_from_mut(self.pos);
209 slice::bytes::copy_memory(dst, buf);
210 self.pos += buf.len();
215 fn flush(&mut self) -> IoResult<()> {
216 self.flush_buf().and_then(|()| self.inner.as_mut().unwrap().flush())
221 impl<W: Writer> Drop for BufferedWriter<W> {
223 if self.inner.is_some() {
224 // dtors should not panic, so we ignore a panicked flush
225 let _ = self.flush_buf();
230 /// Wraps a Writer and buffers output to it, flushing whenever a newline (`0x0a`,
231 /// `'\n'`) is detected.
233 /// This writer will be flushed when it is dropped.
234 pub struct LineBufferedWriter<W> {
235 inner: BufferedWriter<W>,
238 impl<W: Writer> LineBufferedWriter<W> {
239 /// Creates a new `LineBufferedWriter`
240 pub fn new(inner: W) -> LineBufferedWriter<W> {
241 // Lines typically aren't that long, don't use a giant buffer
243 inner: BufferedWriter::with_capacity(1024, inner)
247 /// Gets a reference to the underlying writer.
249 /// This type does not expose the ability to get a mutable reference to the
250 /// underlying reader because that could possibly corrupt the buffer.
251 pub fn get_ref<'a>(&'a self) -> &'a W { self.inner.get_ref() }
253 /// Unwraps this `LineBufferedWriter`, returning the underlying writer.
255 /// The internal buffer is flushed before returning the writer.
256 pub fn into_inner(self) -> W { self.inner.into_inner() }
259 impl<W: Writer> Writer for LineBufferedWriter<W> {
260 fn write(&mut self, buf: &[u8]) -> IoResult<()> {
261 match buf.iter().rposition(|&b| b == b'\n') {
263 try!(self.inner.write(buf[..i + 1]));
264 try!(self.inner.flush());
265 try!(self.inner.write(buf[i + 1..]));
268 None => self.inner.write(buf),
272 fn flush(&mut self) -> IoResult<()> { self.inner.flush() }
275 struct InternalBufferedWriter<W>(BufferedWriter<W>);
277 impl<W> InternalBufferedWriter<W> {
278 fn get_mut<'a>(&'a mut self) -> &'a mut BufferedWriter<W> {
279 let InternalBufferedWriter(ref mut w) = *self;
284 impl<W: Reader> Reader for InternalBufferedWriter<W> {
285 fn read(&mut self, buf: &mut [u8]) -> IoResult<uint> {
286 self.get_mut().inner.as_mut().unwrap().read(buf)
290 /// Wraps a Stream and buffers input and output to and from it.
292 /// It can be excessively inefficient to work directly with a `Stream`. For
293 /// example, every call to `read` or `write` on `TcpStream` results in a system
294 /// call. A `BufferedStream` keeps in memory buffers of data, making large,
295 /// infrequent calls to `read` and `write` on the underlying `Stream`.
297 /// The output half will be flushed when this stream is dropped.
302 /// # #![allow(unused_must_use)]
303 /// use std::io::{BufferedStream, File};
305 /// let file = File::open(&Path::new("message.txt"));
306 /// let mut stream = BufferedStream::new(file);
308 /// stream.write("hello, world".as_bytes());
311 /// let mut buf = [0; 100];
312 /// match stream.read(&mut buf) {
313 /// Ok(nread) => println!("Read {} bytes", nread),
314 /// Err(e) => println!("error reading: {}", e)
317 pub struct BufferedStream<S> {
318 inner: BufferedReader<InternalBufferedWriter<S>>
321 impl<S: Stream> BufferedStream<S> {
322 /// Creates a new buffered stream with explicitly listed capacities for the
323 /// reader/writer buffer.
324 pub fn with_capacities(reader_cap: uint, writer_cap: uint, inner: S)
325 -> BufferedStream<S> {
326 let writer = BufferedWriter::with_capacity(writer_cap, inner);
327 let internal_writer = InternalBufferedWriter(writer);
328 let reader = BufferedReader::with_capacity(reader_cap,
330 BufferedStream { inner: reader }
333 /// Creates a new buffered stream with the default reader/writer buffer
335 pub fn new(inner: S) -> BufferedStream<S> {
336 BufferedStream::with_capacities(DEFAULT_BUF_SIZE, DEFAULT_BUF_SIZE,
340 /// Gets a reference to the underlying stream.
341 pub fn get_ref(&self) -> &S {
342 let InternalBufferedWriter(ref w) = self.inner.inner;
346 /// Gets a mutable reference to the underlying stream.
350 /// It is inadvisable to read directly from or write directly to the
351 /// underlying stream.
352 pub fn get_mut(&mut self) -> &mut S {
353 let InternalBufferedWriter(ref mut w) = self.inner.inner;
357 /// Unwraps this `BufferedStream`, returning the underlying stream.
359 /// The internal buffer is flushed before returning the stream. Any leftover
360 /// data in the read buffer is lost.
361 pub fn into_inner(self) -> S {
362 let InternalBufferedWriter(w) = self.inner.inner;
367 impl<S: Stream> Buffer for BufferedStream<S> {
368 fn fill_buf<'a>(&'a mut self) -> IoResult<&'a [u8]> { self.inner.fill_buf() }
369 fn consume(&mut self, amt: uint) { self.inner.consume(amt) }
372 impl<S: Stream> Reader for BufferedStream<S> {
373 fn read(&mut self, buf: &mut [u8]) -> IoResult<uint> {
378 impl<S: Stream> Writer for BufferedStream<S> {
379 fn write(&mut self, buf: &[u8]) -> IoResult<()> {
380 self.inner.inner.get_mut().write(buf)
382 fn flush(&mut self) -> IoResult<()> {
383 self.inner.inner.get_mut().flush()
393 use super::super::{IoResult, EndOfFile};
394 use super::super::mem::MemReader;
395 use self::test::Bencher;
397 /// A type, free to create, primarily intended for benchmarking creation of
398 /// wrappers that, just for construction, don't need a Reader/Writer that
399 /// does anything useful. Is equivalent to `/dev/null` in semantics.
400 #[derive(Clone,PartialEq,PartialOrd)]
401 pub struct NullStream;
403 impl Reader for NullStream {
404 fn read(&mut self, _: &mut [u8]) -> io::IoResult<uint> {
405 Err(io::standard_error(io::EndOfFile))
409 impl Writer for NullStream {
410 fn write(&mut self, _: &[u8]) -> io::IoResult<()> { Ok(()) }
413 /// A dummy reader intended at testing short-reads propagation.
414 pub struct ShortReader {
418 impl Reader for ShortReader {
419 fn read(&mut self, _: &mut [u8]) -> io::IoResult<uint> {
420 if self.lengths.is_empty() {
421 Err(io::standard_error(io::EndOfFile))
423 Ok(self.lengths.remove(0))
429 fn test_buffered_reader() {
430 let inner = MemReader::new(vec!(5, 6, 7, 0, 1, 2, 3, 4));
431 let mut reader = BufferedReader::with_capacity(2, inner);
433 let mut buf = [0, 0, 0];
434 let nread = reader.read(&mut buf);
435 assert_eq!(Ok(3), nread);
436 let b: &[_] = &[5, 6, 7];
439 let mut buf = [0, 0];
440 let nread = reader.read(&mut buf);
441 assert_eq!(Ok(2), nread);
442 let b: &[_] = &[0, 1];
446 let nread = reader.read(&mut buf);
447 assert_eq!(Ok(1), nread);
451 let mut buf = [0, 0, 0];
452 let nread = reader.read(&mut buf);
453 assert_eq!(Ok(1), nread);
454 let b: &[_] = &[3, 0, 0];
457 let nread = reader.read(&mut buf);
458 assert_eq!(Ok(1), nread);
459 let b: &[_] = &[4, 0, 0];
462 assert!(reader.read(&mut buf).is_err());
466 fn test_buffered_writer() {
467 let inner = Vec::new();
468 let mut writer = BufferedWriter::with_capacity(2, inner);
470 writer.write(&[0, 1]).unwrap();
472 assert_eq!(writer.get_ref()[], b);
474 writer.write(&[2]).unwrap();
475 let b: &[_] = &[0, 1];
476 assert_eq!(writer.get_ref()[], b);
478 writer.write(&[3]).unwrap();
479 assert_eq!(writer.get_ref()[], b);
481 writer.flush().unwrap();
482 let a: &[_] = &[0, 1, 2, 3];
483 assert_eq!(a, writer.get_ref()[]);
485 writer.write(&[4]).unwrap();
486 writer.write(&[5]).unwrap();
487 assert_eq!(a, writer.get_ref()[]);
489 writer.write(&[6]).unwrap();
490 let a: &[_] = &[0, 1, 2, 3, 4, 5];
494 writer.write(&[7, 8]).unwrap();
495 let a: &[_] = &[0, 1, 2, 3, 4, 5, 6];
499 writer.write(&[9, 10, 11]).unwrap();
500 let a: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11];
504 writer.flush().unwrap();
510 fn test_buffered_writer_inner_flushes() {
511 let mut w = BufferedWriter::with_capacity(3, Vec::new());
512 w.write(&[0, 1]).unwrap();
514 assert_eq!(a, w.get_ref()[]);
515 let w = w.into_inner();
516 let a: &[_] = &[0, 1];
520 // This is just here to make sure that we don't infinite loop in the
521 // newtype struct autoderef weirdness
523 fn test_buffered_stream() {
526 impl io::Writer for S {
527 fn write(&mut self, _: &[u8]) -> io::IoResult<()> { Ok(()) }
530 impl io::Reader for S {
531 fn read(&mut self, _: &mut [u8]) -> io::IoResult<uint> {
532 Err(io::standard_error(io::EndOfFile))
536 let mut stream = BufferedStream::new(S);
538 assert!(stream.read(&mut buf).is_err());
539 stream.write(&buf).unwrap();
540 stream.flush().unwrap();
544 fn test_read_until() {
545 let inner = MemReader::new(vec!(0, 1, 2, 1, 0));
546 let mut reader = BufferedReader::with_capacity(2, inner);
547 assert_eq!(reader.read_until(0), Ok(vec!(0)));
548 assert_eq!(reader.read_until(2), Ok(vec!(1, 2)));
549 assert_eq!(reader.read_until(1), Ok(vec!(1)));
550 assert_eq!(reader.read_until(8), Ok(vec!(0)));
551 assert!(reader.read_until(9).is_err());
555 fn test_line_buffer() {
556 let mut writer = LineBufferedWriter::new(Vec::new());
557 writer.write(&[0]).unwrap();
559 assert_eq!(writer.get_ref()[], b);
560 writer.write(&[1]).unwrap();
561 assert_eq!(writer.get_ref()[], b);
562 writer.flush().unwrap();
563 let b: &[_] = &[0, 1];
564 assert_eq!(writer.get_ref()[], b);
565 writer.write(&[0, b'\n', 1, b'\n', 2]).unwrap();
566 let b: &[_] = &[0, 1, 0, b'\n', 1, b'\n'];
567 assert_eq!(writer.get_ref()[], b);
568 writer.flush().unwrap();
569 let b: &[_] = &[0, 1, 0, b'\n', 1, b'\n', 2];
570 assert_eq!(writer.get_ref()[], b);
571 writer.write(&[3, b'\n']).unwrap();
572 let b: &[_] = &[0, 1, 0, b'\n', 1, b'\n', 2, 3, b'\n'];
573 assert_eq!(writer.get_ref()[], b);
577 fn test_read_line() {
578 let in_buf = MemReader::new(b"a\nb\nc".to_vec());
579 let mut reader = BufferedReader::with_capacity(2, in_buf);
580 assert_eq!(reader.read_line(), Ok("a\n".to_string()));
581 assert_eq!(reader.read_line(), Ok("b\n".to_string()));
582 assert_eq!(reader.read_line(), Ok("c".to_string()));
583 assert!(reader.read_line().is_err());
588 let in_buf = MemReader::new(b"a\nb\nc".to_vec());
589 let mut reader = BufferedReader::with_capacity(2, in_buf);
590 let mut it = reader.lines();
591 assert_eq!(it.next(), Some(Ok("a\n".to_string())));
592 assert_eq!(it.next(), Some(Ok("b\n".to_string())));
593 assert_eq!(it.next(), Some(Ok("c".to_string())));
594 assert_eq!(it.next(), None);
598 fn test_short_reads() {
599 let inner = ShortReader{lengths: vec![0, 1, 2, 0, 1, 0]};
600 let mut reader = BufferedReader::new(inner);
601 let mut buf = [0, 0];
602 assert_eq!(reader.read(&mut buf), Ok(0));
603 assert_eq!(reader.read(&mut buf), Ok(1));
604 assert_eq!(reader.read(&mut buf), Ok(2));
605 assert_eq!(reader.read(&mut buf), Ok(0));
606 assert_eq!(reader.read(&mut buf), Ok(1));
607 assert_eq!(reader.read(&mut buf), Ok(0));
608 assert!(reader.read(&mut buf).is_err());
612 fn read_char_buffered() {
613 let buf = [195u8, 159u8];
614 let mut reader = BufferedReader::with_capacity(1, buf[]);
615 assert_eq!(reader.read_char(), Ok('ß'));
620 let buf = [195u8, 159u8, b'a'];
621 let mut reader = BufferedReader::with_capacity(1, buf[]);
622 let mut it = reader.chars();
623 assert_eq!(it.next(), Some(Ok('ß')));
624 assert_eq!(it.next(), Some(Ok('a')));
625 assert_eq!(it.next(), None);
630 fn dont_panic_in_drop_on_panicked_flush() {
631 struct FailFlushWriter;
633 impl Writer for FailFlushWriter {
634 fn write(&mut self, _buf: &[u8]) -> IoResult<()> { Ok(()) }
635 fn flush(&mut self) -> IoResult<()> { Err(io::standard_error(EndOfFile)) }
638 let writer = FailFlushWriter;
639 let _writer = BufferedWriter::new(writer);
641 // If writer panics *again* due to the flush error then the process will abort.
646 fn bench_buffered_reader(b: &mut Bencher) {
648 BufferedReader::new(NullStream)
653 fn bench_buffered_writer(b: &mut Bencher) {
655 BufferedWriter::new(NullStream)
660 fn bench_buffered_stream(b: &mut Bencher) {
662 BufferedStream::new(NullStream);