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::{IteratorExt, ExactSizeIterator};
20 use option::Option::{Some, None};
21 use result::Result::Ok;
22 use slice::{SliceExt};
26 // NOTE: for old macros; remove after the next snapshot
27 #[cfg(stage0)] use result::Result::Err;
29 /// Wraps a Reader and buffers input from it
31 /// It can be excessively inefficient to work directly with a `Reader`. For
32 /// example, every call to `read` on `TcpStream` results in a system call. A
33 /// `BufferedReader` performs large, infrequent reads on the underlying
34 /// `Reader` and maintains an in-memory buffer of the results.
39 /// use std::io::{BufferedReader, File};
41 /// let file = File::open(&Path::new("message.txt"));
42 /// let mut reader = BufferedReader::new(file);
44 /// let mut buf = [0; 100];
45 /// match reader.read(&mut buf) {
46 /// Ok(nread) => println!("Read {} bytes", nread),
47 /// Err(e) => println!("error reading: {}", e)
50 pub struct BufferedReader<R> {
57 impl<R: Reader> BufferedReader<R> {
58 /// Creates a new `BufferedReader` with the specified buffer capacity
59 pub fn with_capacity(cap: uint, inner: R) -> BufferedReader<R> {
60 // It's *much* faster to create an uninitialized buffer than it is to
61 // fill everything in with 0. This buffer is entirely an implementation
62 // detail and is never exposed, so we're safe to not initialize
63 // everything up-front. This allows creation of BufferedReader instances
64 // to be very cheap (large mallocs are not nearly as expensive as large
66 let mut buf = Vec::with_capacity(cap);
67 unsafe { buf.set_len(cap); }
76 /// Creates a new `BufferedReader` with a default buffer capacity
77 pub fn new(inner: R) -> BufferedReader<R> {
78 BufferedReader::with_capacity(DEFAULT_BUF_SIZE, inner)
81 /// Gets a reference to the underlying reader.
82 pub fn get_ref<'a>(&self) -> &R { &self.inner }
84 /// Gets a mutable reference to the underlying reader.
88 /// It is inadvisable to directly read from the underlying reader.
89 pub fn get_mut(&mut self) -> &mut R { &mut self.inner }
91 /// Unwraps this `BufferedReader`, returning the underlying reader.
93 /// Note that any leftover data in the internal buffer is lost.
94 pub fn into_inner(self) -> R { self.inner }
97 impl<R: Reader> Buffer for BufferedReader<R> {
98 fn fill_buf<'a>(&'a mut self) -> IoResult<&'a [u8]> {
99 if self.pos == self.cap {
100 self.cap = try!(self.inner.read(self.buf.as_mut_slice()));
103 Ok(self.buf[self.pos..self.cap])
106 fn consume(&mut self, amt: uint) {
108 assert!(self.pos <= self.cap);
112 impl<R: Reader> Reader for BufferedReader<R> {
113 fn read(&mut self, buf: &mut [u8]) -> IoResult<uint> {
114 if self.pos == self.cap && buf.len() >= self.buf.capacity() {
115 return self.inner.read(buf);
118 let available = try!(self.fill_buf());
119 let nread = cmp::min(available.len(), buf.len());
120 slice::bytes::copy_memory(buf, available[..nread]);
128 /// Wraps a Writer and buffers output to it
130 /// It can be excessively inefficient to work directly with a `Writer`. For
131 /// example, every call to `write` on `TcpStream` results in a system call. A
132 /// `BufferedWriter` keeps an in memory buffer of data and writes it to the
133 /// underlying `Writer` in large, infrequent batches.
135 /// This writer will be flushed when it is dropped.
140 /// use std::io::{BufferedWriter, File};
142 /// let file = File::create(&Path::new("message.txt")).unwrap();
143 /// let mut writer = BufferedWriter::new(file);
145 /// writer.write_str("hello, world").unwrap();
146 /// writer.flush().unwrap();
148 pub struct BufferedWriter<W> {
154 impl<W: Writer> BufferedWriter<W> {
155 /// Creates a new `BufferedWriter` with the specified buffer capacity
156 pub fn with_capacity(cap: uint, inner: W) -> BufferedWriter<W> {
157 // See comments in BufferedReader for why this uses unsafe code.
158 let mut buf = Vec::with_capacity(cap);
159 unsafe { buf.set_len(cap); }
167 /// Creates a new `BufferedWriter` with a default buffer capacity
168 pub fn new(inner: W) -> BufferedWriter<W> {
169 BufferedWriter::with_capacity(DEFAULT_BUF_SIZE, inner)
172 fn flush_buf(&mut self) -> IoResult<()> {
174 let ret = self.inner.as_mut().unwrap().write(self.buf[..self.pos]);
182 /// Gets a reference to the underlying writer.
183 pub fn get_ref(&self) -> &W { self.inner.as_ref().unwrap() }
185 /// Gets a mutable reference to the underlying write.
189 /// It is inadvisable to directly read from the underlying writer.
190 pub fn get_mut(&mut self) -> &mut W { self.inner.as_mut().unwrap() }
192 /// Unwraps this `BufferedWriter`, returning the underlying writer.
194 /// The buffer is flushed before returning the writer.
195 pub fn into_inner(mut self) -> W {
196 // FIXME(#12628): is panicking the right thing to do if flushing panicks?
197 self.flush_buf().unwrap();
198 self.inner.take().unwrap()
202 impl<W: Writer> Writer for BufferedWriter<W> {
203 fn write(&mut self, buf: &[u8]) -> IoResult<()> {
204 if self.pos + buf.len() > self.buf.len() {
205 try!(self.flush_buf());
208 if buf.len() > self.buf.len() {
209 self.inner.as_mut().unwrap().write(buf)
211 let dst = self.buf.slice_from_mut(self.pos);
212 slice::bytes::copy_memory(dst, buf);
213 self.pos += buf.len();
218 fn flush(&mut self) -> IoResult<()> {
219 self.flush_buf().and_then(|()| self.inner.as_mut().unwrap().flush())
224 impl<W: Writer> Drop for BufferedWriter<W> {
226 if self.inner.is_some() {
227 // dtors should not panic, so we ignore a panicked flush
228 let _ = self.flush_buf();
233 /// Wraps a Writer and buffers output to it, flushing whenever a newline (`0x0a`,
234 /// `'\n'`) is detected.
236 /// This writer will be flushed when it is dropped.
237 pub struct LineBufferedWriter<W> {
238 inner: BufferedWriter<W>,
241 impl<W: Writer> LineBufferedWriter<W> {
242 /// Creates a new `LineBufferedWriter`
243 pub fn new(inner: W) -> LineBufferedWriter<W> {
244 // Lines typically aren't that long, don't use a giant buffer
246 inner: BufferedWriter::with_capacity(1024, inner)
250 /// Gets a reference to the underlying writer.
252 /// This type does not expose the ability to get a mutable reference to the
253 /// underlying reader because that could possibly corrupt the buffer.
254 pub fn get_ref<'a>(&'a self) -> &'a W { self.inner.get_ref() }
256 /// Unwraps this `LineBufferedWriter`, returning the underlying writer.
258 /// The internal buffer is flushed before returning the writer.
259 pub fn into_inner(self) -> W { self.inner.into_inner() }
262 impl<W: Writer> Writer for LineBufferedWriter<W> {
263 fn write(&mut self, buf: &[u8]) -> IoResult<()> {
264 match buf.iter().rposition(|&b| b == b'\n') {
266 try!(self.inner.write(buf[..i + 1]));
267 try!(self.inner.flush());
268 try!(self.inner.write(buf[i + 1..]));
271 None => self.inner.write(buf),
275 fn flush(&mut self) -> IoResult<()> { self.inner.flush() }
278 struct InternalBufferedWriter<W>(BufferedWriter<W>);
280 impl<W> InternalBufferedWriter<W> {
281 fn get_mut<'a>(&'a mut self) -> &'a mut BufferedWriter<W> {
282 let InternalBufferedWriter(ref mut w) = *self;
287 impl<W: Reader> Reader for InternalBufferedWriter<W> {
288 fn read(&mut self, buf: &mut [u8]) -> IoResult<uint> {
289 self.get_mut().inner.as_mut().unwrap().read(buf)
293 /// Wraps a Stream and buffers input and output to and from it.
295 /// It can be excessively inefficient to work directly with a `Stream`. For
296 /// example, every call to `read` or `write` on `TcpStream` results in a system
297 /// call. A `BufferedStream` keeps in memory buffers of data, making large,
298 /// infrequent calls to `read` and `write` on the underlying `Stream`.
300 /// The output half will be flushed when this stream is dropped.
305 /// # #![allow(unused_must_use)]
306 /// use std::io::{BufferedStream, File};
308 /// let file = File::open(&Path::new("message.txt"));
309 /// let mut stream = BufferedStream::new(file);
311 /// stream.write("hello, world".as_bytes());
314 /// let mut buf = [0; 100];
315 /// match stream.read(&mut buf) {
316 /// Ok(nread) => println!("Read {} bytes", nread),
317 /// Err(e) => println!("error reading: {}", e)
320 pub struct BufferedStream<S> {
321 inner: BufferedReader<InternalBufferedWriter<S>>
324 impl<S: Stream> BufferedStream<S> {
325 /// Creates a new buffered stream with explicitly listed capacities for the
326 /// reader/writer buffer.
327 pub fn with_capacities(reader_cap: uint, writer_cap: uint, inner: S)
328 -> BufferedStream<S> {
329 let writer = BufferedWriter::with_capacity(writer_cap, inner);
330 let internal_writer = InternalBufferedWriter(writer);
331 let reader = BufferedReader::with_capacity(reader_cap,
333 BufferedStream { inner: reader }
336 /// Creates a new buffered stream with the default reader/writer buffer
338 pub fn new(inner: S) -> BufferedStream<S> {
339 BufferedStream::with_capacities(DEFAULT_BUF_SIZE, DEFAULT_BUF_SIZE,
343 /// Gets a reference to the underlying stream.
344 pub fn get_ref(&self) -> &S {
345 let InternalBufferedWriter(ref w) = self.inner.inner;
349 /// Gets a mutable reference to the underlying stream.
353 /// It is inadvisable to read directly from or write directly to the
354 /// underlying stream.
355 pub fn get_mut(&mut self) -> &mut S {
356 let InternalBufferedWriter(ref mut w) = self.inner.inner;
360 /// Unwraps this `BufferedStream`, returning the underlying stream.
362 /// The internal buffer is flushed before returning the stream. Any leftover
363 /// data in the read buffer is lost.
364 pub fn into_inner(self) -> S {
365 let InternalBufferedWriter(w) = self.inner.inner;
370 impl<S: Stream> Buffer for BufferedStream<S> {
371 fn fill_buf<'a>(&'a mut self) -> IoResult<&'a [u8]> { self.inner.fill_buf() }
372 fn consume(&mut self, amt: uint) { self.inner.consume(amt) }
375 impl<S: Stream> Reader for BufferedStream<S> {
376 fn read(&mut self, buf: &mut [u8]) -> IoResult<uint> {
381 impl<S: Stream> Writer for BufferedStream<S> {
382 fn write(&mut self, buf: &[u8]) -> IoResult<()> {
383 self.inner.inner.get_mut().write(buf)
385 fn flush(&mut self) -> IoResult<()> {
386 self.inner.inner.get_mut().flush()
396 use super::super::{IoResult, EndOfFile};
397 use super::super::mem::MemReader;
398 use self::test::Bencher;
400 /// A type, free to create, primarily intended for benchmarking creation of
401 /// wrappers that, just for construction, don't need a Reader/Writer that
402 /// does anything useful. Is equivalent to `/dev/null` in semantics.
403 #[derive(Clone,PartialEq,PartialOrd)]
404 pub struct NullStream;
406 impl Reader for NullStream {
407 fn read(&mut self, _: &mut [u8]) -> io::IoResult<uint> {
408 Err(io::standard_error(io::EndOfFile))
412 impl Writer for NullStream {
413 fn write(&mut self, _: &[u8]) -> io::IoResult<()> { Ok(()) }
416 /// A dummy reader intended at testing short-reads propagation.
417 pub struct ShortReader {
421 impl Reader for ShortReader {
422 fn read(&mut self, _: &mut [u8]) -> io::IoResult<uint> {
423 if self.lengths.is_empty() {
424 Err(io::standard_error(io::EndOfFile))
426 Ok(self.lengths.remove(0))
432 fn test_buffered_reader() {
433 let inner = MemReader::new(vec!(5, 6, 7, 0, 1, 2, 3, 4));
434 let mut reader = BufferedReader::with_capacity(2, inner);
436 let mut buf = [0, 0, 0];
437 let nread = reader.read(&mut buf);
438 assert_eq!(Ok(3), nread);
439 let b: &[_] = &[5, 6, 7];
442 let mut buf = [0, 0];
443 let nread = reader.read(&mut buf);
444 assert_eq!(Ok(2), nread);
445 let b: &[_] = &[0, 1];
449 let nread = reader.read(&mut buf);
450 assert_eq!(Ok(1), nread);
454 let mut buf = [0, 0, 0];
455 let nread = reader.read(&mut buf);
456 assert_eq!(Ok(1), nread);
457 let b: &[_] = &[3, 0, 0];
460 let nread = reader.read(&mut buf);
461 assert_eq!(Ok(1), nread);
462 let b: &[_] = &[4, 0, 0];
465 assert!(reader.read(&mut buf).is_err());
469 fn test_buffered_writer() {
470 let inner = Vec::new();
471 let mut writer = BufferedWriter::with_capacity(2, inner);
473 writer.write(&[0, 1]).unwrap();
475 assert_eq!(writer.get_ref()[], b);
477 writer.write(&[2]).unwrap();
478 let b: &[_] = &[0, 1];
479 assert_eq!(writer.get_ref()[], b);
481 writer.write(&[3]).unwrap();
482 assert_eq!(writer.get_ref()[], b);
484 writer.flush().unwrap();
485 let a: &[_] = &[0, 1, 2, 3];
486 assert_eq!(a, writer.get_ref()[]);
488 writer.write(&[4]).unwrap();
489 writer.write(&[5]).unwrap();
490 assert_eq!(a, writer.get_ref()[]);
492 writer.write(&[6]).unwrap();
493 let a: &[_] = &[0, 1, 2, 3, 4, 5];
497 writer.write(&[7, 8]).unwrap();
498 let a: &[_] = &[0, 1, 2, 3, 4, 5, 6];
502 writer.write(&[9, 10, 11]).unwrap();
503 let a: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11];
507 writer.flush().unwrap();
513 fn test_buffered_writer_inner_flushes() {
514 let mut w = BufferedWriter::with_capacity(3, Vec::new());
515 w.write(&[0, 1]).unwrap();
517 assert_eq!(a, w.get_ref()[]);
518 let w = w.into_inner();
519 let a: &[_] = &[0, 1];
523 // This is just here to make sure that we don't infinite loop in the
524 // newtype struct autoderef weirdness
526 fn test_buffered_stream() {
529 impl io::Writer for S {
530 fn write(&mut self, _: &[u8]) -> io::IoResult<()> { Ok(()) }
533 impl io::Reader for S {
534 fn read(&mut self, _: &mut [u8]) -> io::IoResult<uint> {
535 Err(io::standard_error(io::EndOfFile))
539 let mut stream = BufferedStream::new(S);
541 assert!(stream.read(&mut buf).is_err());
542 stream.write(&buf).unwrap();
543 stream.flush().unwrap();
547 fn test_read_until() {
548 let inner = MemReader::new(vec!(0, 1, 2, 1, 0));
549 let mut reader = BufferedReader::with_capacity(2, inner);
550 assert_eq!(reader.read_until(0), Ok(vec!(0)));
551 assert_eq!(reader.read_until(2), Ok(vec!(1, 2)));
552 assert_eq!(reader.read_until(1), Ok(vec!(1)));
553 assert_eq!(reader.read_until(8), Ok(vec!(0)));
554 assert!(reader.read_until(9).is_err());
558 fn test_line_buffer() {
559 let mut writer = LineBufferedWriter::new(Vec::new());
560 writer.write(&[0]).unwrap();
562 assert_eq!(writer.get_ref()[], b);
563 writer.write(&[1]).unwrap();
564 assert_eq!(writer.get_ref()[], b);
565 writer.flush().unwrap();
566 let b: &[_] = &[0, 1];
567 assert_eq!(writer.get_ref()[], b);
568 writer.write(&[0, b'\n', 1, b'\n', 2]).unwrap();
569 let b: &[_] = &[0, 1, 0, b'\n', 1, b'\n'];
570 assert_eq!(writer.get_ref()[], b);
571 writer.flush().unwrap();
572 let b: &[_] = &[0, 1, 0, b'\n', 1, b'\n', 2];
573 assert_eq!(writer.get_ref()[], b);
574 writer.write(&[3, b'\n']).unwrap();
575 let b: &[_] = &[0, 1, 0, b'\n', 1, b'\n', 2, 3, b'\n'];
576 assert_eq!(writer.get_ref()[], b);
580 fn test_read_line() {
581 let in_buf = MemReader::new(b"a\nb\nc".to_vec());
582 let mut reader = BufferedReader::with_capacity(2, in_buf);
583 assert_eq!(reader.read_line(), Ok("a\n".to_string()));
584 assert_eq!(reader.read_line(), Ok("b\n".to_string()));
585 assert_eq!(reader.read_line(), Ok("c".to_string()));
586 assert!(reader.read_line().is_err());
591 let in_buf = MemReader::new(b"a\nb\nc".to_vec());
592 let mut reader = BufferedReader::with_capacity(2, in_buf);
593 let mut it = reader.lines();
594 assert_eq!(it.next(), Some(Ok("a\n".to_string())));
595 assert_eq!(it.next(), Some(Ok("b\n".to_string())));
596 assert_eq!(it.next(), Some(Ok("c".to_string())));
597 assert_eq!(it.next(), None);
601 fn test_short_reads() {
602 let inner = ShortReader{lengths: vec![0, 1, 2, 0, 1, 0]};
603 let mut reader = BufferedReader::new(inner);
604 let mut buf = [0, 0];
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(2));
608 assert_eq!(reader.read(&mut buf), Ok(0));
609 assert_eq!(reader.read(&mut buf), Ok(1));
610 assert_eq!(reader.read(&mut buf), Ok(0));
611 assert!(reader.read(&mut buf).is_err());
615 fn read_char_buffered() {
616 let buf = [195u8, 159u8];
617 let mut reader = BufferedReader::with_capacity(1, buf[]);
618 assert_eq!(reader.read_char(), Ok('ß'));
623 let buf = [195u8, 159u8, b'a'];
624 let mut reader = BufferedReader::with_capacity(1, buf[]);
625 let mut it = reader.chars();
626 assert_eq!(it.next(), Some(Ok('ß')));
627 assert_eq!(it.next(), Some(Ok('a')));
628 assert_eq!(it.next(), None);
633 fn dont_panic_in_drop_on_panicked_flush() {
634 struct FailFlushWriter;
636 impl Writer for FailFlushWriter {
637 fn write(&mut self, _buf: &[u8]) -> IoResult<()> { Ok(()) }
638 fn flush(&mut self) -> IoResult<()> { Err(io::standard_error(EndOfFile)) }
641 let writer = FailFlushWriter;
642 let _writer = BufferedWriter::new(writer);
644 // If writer panics *again* due to the flush error then the process will abort.
649 fn bench_buffered_reader(b: &mut Bencher) {
651 BufferedReader::new(NullStream)
656 fn bench_buffered_writer(b: &mut Bencher) {
658 BufferedWriter::new(NullStream)
663 fn bench_buffered_stream(b: &mut Bencher) {
665 BufferedStream::new(NullStream);