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};
19 use option::{Some, None, Option};
20 use result::{Ok, Err};
21 use slice::{ImmutableSlice, MutableSlice};
25 /// Wraps a Reader and buffers input from it
27 /// It can be excessively inefficient to work directly with a `Reader`. For
28 /// example, every call to `read` on `TcpStream` results in a system call. A
29 /// `BufferedReader` performs large, infrequent reads on the underlying
30 /// `Reader` and maintains an in-memory buffer of the results.
35 /// use std::io::{BufferedReader, File};
37 /// let file = File::open(&Path::new("message.txt"));
38 /// let mut reader = BufferedReader::new(file);
40 /// let mut buf = [0, ..100];
41 /// match reader.read(buf) {
42 /// Ok(nread) => println!("Read {} bytes", nread),
43 /// Err(e) => println!("error reading: {}", e)
46 pub struct BufferedReader<R> {
53 impl<R: Reader> BufferedReader<R> {
54 /// Creates a new `BufferedReader` with the specified buffer capacity
55 pub fn with_capacity(cap: uint, inner: R) -> BufferedReader<R> {
56 // It's *much* faster to create an uninitialized buffer than it is to
57 // fill everything in with 0. This buffer is entirely an implementation
58 // detail and is never exposed, so we're safe to not initialize
59 // everything up-front. This allows creation of BufferedReader instances
60 // to be very cheap (large mallocs are not nearly as expensive as large
62 let mut buf = Vec::with_capacity(cap);
63 unsafe { buf.set_len(cap); }
72 /// Creates a new `BufferedReader` with a default buffer capacity
73 pub fn new(inner: R) -> BufferedReader<R> {
74 BufferedReader::with_capacity(DEFAULT_BUF_SIZE, inner)
77 /// Gets a reference to the underlying reader.
79 /// This type does not expose the ability to get a mutable reference to the
80 /// underlying reader because that could possibly corrupt the buffer.
81 pub fn get_ref<'a>(&'a self) -> &'a R { &self.inner }
83 /// Unwraps this `BufferedReader`, returning the underlying reader.
85 /// Note that any leftover data in the internal buffer is lost.
86 pub fn unwrap(self) -> R { self.inner }
89 impl<R: Reader> Buffer for BufferedReader<R> {
90 fn fill_buf<'a>(&'a mut self) -> IoResult<&'a [u8]> {
91 if self.pos == self.cap {
92 self.cap = try!(self.inner.read(self.buf[mut]));
95 Ok(self.buf[self.pos..self.cap])
98 fn consume(&mut self, amt: uint) {
100 assert!(self.pos <= self.cap);
104 impl<R: Reader> Reader for BufferedReader<R> {
105 fn read(&mut self, buf: &mut [u8]) -> IoResult<uint> {
106 if self.pos == self.cap && buf.len() >= self.buf.capacity() {
107 return self.inner.read(buf);
110 let available = try!(self.fill_buf());
111 let nread = cmp::min(available.len(), buf.len());
112 slice::bytes::copy_memory(buf, available[..nread]);
120 /// Wraps a Writer and buffers output to it
122 /// It can be excessively inefficient to work directly with a `Writer`. For
123 /// example, every call to `write` on `TcpStream` results in a system call. A
124 /// `BufferedWriter` keeps an in memory buffer of data and writes it to the
125 /// underlying `Writer` in large, infrequent batches.
127 /// This writer will be flushed when it is dropped.
132 /// use std::io::{BufferedWriter, File};
134 /// let file = File::create(&Path::new("message.txt")).unwrap();
135 /// let mut writer = BufferedWriter::new(file);
137 /// writer.write_str("hello, world").unwrap();
138 /// writer.flush().unwrap();
140 pub struct BufferedWriter<W> {
146 impl<W: Writer> BufferedWriter<W> {
147 /// Creates a new `BufferedWriter` with the specified buffer capacity
148 pub fn with_capacity(cap: uint, inner: W) -> BufferedWriter<W> {
149 // See comments in BufferedReader for why this uses unsafe code.
150 let mut buf = Vec::with_capacity(cap);
151 unsafe { buf.set_len(cap); }
159 /// Creates a new `BufferedWriter` with a default buffer capacity
160 pub fn new(inner: W) -> BufferedWriter<W> {
161 BufferedWriter::with_capacity(DEFAULT_BUF_SIZE, inner)
164 fn flush_buf(&mut self) -> IoResult<()> {
166 let ret = self.inner.as_mut().unwrap().write(self.buf[..self.pos]);
174 /// Gets a reference to the underlying writer.
176 /// This type does not expose the ability to get a mutable reference to the
177 /// underlying reader because that could possibly corrupt the buffer.
178 pub fn get_ref<'a>(&'a self) -> &'a W { self.inner.as_ref().unwrap() }
180 /// Unwraps this `BufferedWriter`, returning the underlying writer.
182 /// The buffer is flushed before returning the writer.
183 pub fn unwrap(mut self) -> W {
184 // FIXME(#12628): is panicking the right thing to do if flushing panicks?
185 self.flush_buf().unwrap();
186 self.inner.take().unwrap()
190 impl<W: Writer> Writer for BufferedWriter<W> {
191 fn write(&mut self, buf: &[u8]) -> IoResult<()> {
192 if self.pos + buf.len() > self.buf.len() {
193 try!(self.flush_buf());
196 if buf.len() > self.buf.len() {
197 self.inner.as_mut().unwrap().write(buf)
199 let dst = self.buf[mut self.pos..];
200 slice::bytes::copy_memory(dst, buf);
201 self.pos += buf.len();
206 fn flush(&mut self) -> IoResult<()> {
207 self.flush_buf().and_then(|()| self.inner.as_mut().unwrap().flush())
212 impl<W: Writer> Drop for BufferedWriter<W> {
214 if self.inner.is_some() {
215 // dtors should not panic, so we ignore a panicked flush
216 let _ = self.flush_buf();
221 /// Wraps a Writer and buffers output to it, flushing whenever a newline (`0x0a`,
222 /// `'\n'`) is detected.
224 /// This writer will be flushed when it is dropped.
225 pub struct LineBufferedWriter<W> {
226 inner: BufferedWriter<W>,
229 impl<W: Writer> LineBufferedWriter<W> {
230 /// Creates a new `LineBufferedWriter`
231 pub fn new(inner: W) -> LineBufferedWriter<W> {
232 // Lines typically aren't that long, don't use a giant buffer
234 inner: BufferedWriter::with_capacity(1024, inner)
238 /// Gets a reference to the underlying writer.
240 /// This type does not expose the ability to get a mutable reference to the
241 /// underlying reader because that could possibly corrupt the buffer.
242 pub fn get_ref<'a>(&'a self) -> &'a W { self.inner.get_ref() }
244 /// Unwraps this `LineBufferedWriter`, returning the underlying writer.
246 /// The internal buffer is flushed before returning the writer.
247 pub fn unwrap(self) -> W { self.inner.unwrap() }
250 impl<W: Writer> Writer for LineBufferedWriter<W> {
251 fn write(&mut self, buf: &[u8]) -> IoResult<()> {
252 match buf.iter().rposition(|&b| b == b'\n') {
254 try!(self.inner.write(buf[..i + 1]));
255 try!(self.inner.flush());
256 try!(self.inner.write(buf[i + 1..]));
259 None => self.inner.write(buf),
263 fn flush(&mut self) -> IoResult<()> { self.inner.flush() }
266 struct InternalBufferedWriter<W>(BufferedWriter<W>);
268 impl<W> InternalBufferedWriter<W> {
269 fn get_mut<'a>(&'a mut self) -> &'a mut BufferedWriter<W> {
270 let InternalBufferedWriter(ref mut w) = *self;
275 impl<W: Reader> Reader for InternalBufferedWriter<W> {
276 fn read(&mut self, buf: &mut [u8]) -> IoResult<uint> {
277 self.get_mut().inner.as_mut().unwrap().read(buf)
281 /// Wraps a Stream and buffers input and output to and from it.
283 /// It can be excessively inefficient to work directly with a `Stream`. For
284 /// example, every call to `read` or `write` on `TcpStream` results in a system
285 /// call. A `BufferedStream` keeps in memory buffers of data, making large,
286 /// infrequent calls to `read` and `write` on the underlying `Stream`.
288 /// The output half will be flushed when this stream is dropped.
293 /// # #![allow(unused_must_use)]
294 /// use std::io::{BufferedStream, File};
296 /// let file = File::open(&Path::new("message.txt"));
297 /// let mut stream = BufferedStream::new(file);
299 /// stream.write("hello, world".as_bytes());
302 /// let mut buf = [0, ..100];
303 /// match stream.read(buf) {
304 /// Ok(nread) => println!("Read {} bytes", nread),
305 /// Err(e) => println!("error reading: {}", e)
308 pub struct BufferedStream<S> {
309 inner: BufferedReader<InternalBufferedWriter<S>>
312 impl<S: Stream> BufferedStream<S> {
313 /// Creates a new buffered stream with explicitly listed capacities for the
314 /// reader/writer buffer.
315 pub fn with_capacities(reader_cap: uint, writer_cap: uint, inner: S)
316 -> BufferedStream<S> {
317 let writer = BufferedWriter::with_capacity(writer_cap, inner);
318 let internal_writer = InternalBufferedWriter(writer);
319 let reader = BufferedReader::with_capacity(reader_cap,
321 BufferedStream { inner: reader }
324 /// Creates a new buffered stream with the default reader/writer buffer
326 pub fn new(inner: S) -> BufferedStream<S> {
327 BufferedStream::with_capacities(DEFAULT_BUF_SIZE, DEFAULT_BUF_SIZE,
331 /// Gets a reference to the underlying stream.
333 /// This type does not expose the ability to get a mutable reference to the
334 /// underlying reader because that could possibly corrupt the buffer.
335 pub fn get_ref<'a>(&'a self) -> &'a S {
336 let InternalBufferedWriter(ref w) = self.inner.inner;
340 /// Unwraps this `BufferedStream`, returning the underlying stream.
342 /// The internal buffer is flushed before returning the stream. Any leftover
343 /// data in the read buffer is lost.
344 pub fn unwrap(self) -> S {
345 let InternalBufferedWriter(w) = self.inner.inner;
350 impl<S: Stream> Buffer for BufferedStream<S> {
351 fn fill_buf<'a>(&'a mut self) -> IoResult<&'a [u8]> { self.inner.fill_buf() }
352 fn consume(&mut self, amt: uint) { self.inner.consume(amt) }
355 impl<S: Stream> Reader for BufferedStream<S> {
356 fn read(&mut self, buf: &mut [u8]) -> IoResult<uint> {
361 impl<S: Stream> Writer for BufferedStream<S> {
362 fn write(&mut self, buf: &[u8]) -> IoResult<()> {
363 self.inner.inner.get_mut().write(buf)
365 fn flush(&mut self) -> IoResult<()> {
366 self.inner.inner.get_mut().flush()
376 use super::super::{IoResult, EndOfFile};
377 use super::super::mem::{MemReader, MemWriter, BufReader};
378 use self::test::Bencher;
381 /// A type, free to create, primarily intended for benchmarking creation of
382 /// wrappers that, just for construction, don't need a Reader/Writer that
383 /// does anything useful. Is equivalent to `/dev/null` in semantics.
384 #[deriving(Clone,PartialEq,PartialOrd)]
385 pub struct NullStream;
387 impl Reader for NullStream {
388 fn read(&mut self, _: &mut [u8]) -> io::IoResult<uint> {
389 Err(io::standard_error(io::EndOfFile))
393 impl Writer for NullStream {
394 fn write(&mut self, _: &[u8]) -> io::IoResult<()> { Ok(()) }
397 /// A dummy reader intended at testing short-reads propagation.
398 pub struct ShortReader {
402 impl Reader for ShortReader {
403 fn read(&mut self, _: &mut [u8]) -> io::IoResult<uint> {
404 match self.lengths.remove(0) {
406 None => Err(io::standard_error(io::EndOfFile))
412 fn test_buffered_reader() {
413 let inner = MemReader::new(vec!(5, 6, 7, 0, 1, 2, 3, 4));
414 let mut reader = BufferedReader::with_capacity(2, inner);
416 let mut buf = [0, 0, 0];
417 let nread = reader.read(buf);
418 assert_eq!(Ok(3), nread);
419 let b: &[_] = &[5, 6, 7];
420 assert_eq!(buf.as_slice(), b);
422 let mut buf = [0, 0];
423 let nread = reader.read(buf);
424 assert_eq!(Ok(2), nread);
425 let b: &[_] = &[0, 1];
426 assert_eq!(buf.as_slice(), b);
429 let nread = reader.read(buf);
430 assert_eq!(Ok(1), nread);
432 assert_eq!(buf.as_slice(), b);
434 let mut buf = [0, 0, 0];
435 let nread = reader.read(buf);
436 assert_eq!(Ok(1), nread);
437 let b: &[_] = &[3, 0, 0];
438 assert_eq!(buf.as_slice(), b);
440 let nread = reader.read(buf);
441 assert_eq!(Ok(1), nread);
442 let b: &[_] = &[4, 0, 0];
443 assert_eq!(buf.as_slice(), b);
445 assert!(reader.read(buf).is_err());
449 fn test_buffered_writer() {
450 let inner = MemWriter::new();
451 let mut writer = BufferedWriter::with_capacity(2, inner);
453 writer.write([0, 1]).unwrap();
455 assert_eq!(writer.get_ref().get_ref(), b);
457 writer.write([2]).unwrap();
458 let b: &[_] = &[0, 1];
459 assert_eq!(writer.get_ref().get_ref(), b);
461 writer.write([3]).unwrap();
462 assert_eq!(writer.get_ref().get_ref(), b);
464 writer.flush().unwrap();
465 let a: &[_] = &[0, 1, 2, 3];
466 assert_eq!(a, writer.get_ref().get_ref());
468 writer.write([4]).unwrap();
469 writer.write([5]).unwrap();
470 assert_eq!(a, writer.get_ref().get_ref());
472 writer.write([6]).unwrap();
473 let a: &[_] = &[0, 1, 2, 3, 4, 5];
475 writer.get_ref().get_ref());
477 writer.write([7, 8]).unwrap();
478 let a: &[_] = &[0, 1, 2, 3, 4, 5, 6];
480 writer.get_ref().get_ref());
482 writer.write([9, 10, 11]).unwrap();
483 let a: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11];
485 writer.get_ref().get_ref());
487 writer.flush().unwrap();
489 writer.get_ref().get_ref());
493 fn test_buffered_writer_inner_flushes() {
494 let mut w = BufferedWriter::with_capacity(3, MemWriter::new());
495 w.write([0, 1]).unwrap();
497 assert_eq!(a, w.get_ref().get_ref());
499 let a: &[_] = &[0, 1];
500 assert_eq!(a, w.get_ref());
503 // This is just here to make sure that we don't infinite loop in the
504 // newtype struct autoderef weirdness
506 fn test_buffered_stream() {
509 impl io::Writer for S {
510 fn write(&mut self, _: &[u8]) -> io::IoResult<()> { Ok(()) }
513 impl io::Reader for S {
514 fn read(&mut self, _: &mut [u8]) -> io::IoResult<uint> {
515 Err(io::standard_error(io::EndOfFile))
519 let mut stream = BufferedStream::new(S);
521 assert!(stream.read(buf).is_err());
522 stream.write(buf).unwrap();
523 stream.flush().unwrap();
527 fn test_read_until() {
528 let inner = MemReader::new(vec!(0, 1, 2, 1, 0));
529 let mut reader = BufferedReader::with_capacity(2, inner);
530 assert_eq!(reader.read_until(0), Ok(vec!(0)));
531 assert_eq!(reader.read_until(2), Ok(vec!(1, 2)));
532 assert_eq!(reader.read_until(1), Ok(vec!(1)));
533 assert_eq!(reader.read_until(8), Ok(vec!(0)));
534 assert!(reader.read_until(9).is_err());
538 fn test_line_buffer() {
539 let mut writer = LineBufferedWriter::new(MemWriter::new());
540 writer.write([0]).unwrap();
542 assert_eq!(writer.get_ref().get_ref(), b);
543 writer.write([1]).unwrap();
544 assert_eq!(writer.get_ref().get_ref(), b);
545 writer.flush().unwrap();
546 let b: &[_] = &[0, 1];
547 assert_eq!(writer.get_ref().get_ref(), b);
548 writer.write([0, b'\n', 1, b'\n', 2]).unwrap();
549 let b: &[_] = &[0, 1, 0, b'\n', 1, b'\n'];
550 assert_eq!(writer.get_ref().get_ref(), b);
551 writer.flush().unwrap();
552 let b: &[_] = &[0, 1, 0, b'\n', 1, b'\n', 2];
553 assert_eq!(writer.get_ref().get_ref(), b);
554 writer.write([3, b'\n']).unwrap();
555 let b: &[_] = &[0, 1, 0, b'\n', 1, b'\n', 2, 3, b'\n'];
556 assert_eq!(writer.get_ref().get_ref(), b);
560 fn test_read_line() {
561 let in_buf = MemReader::new(b"a\nb\nc".to_vec());
562 let mut reader = BufferedReader::with_capacity(2, in_buf);
563 assert_eq!(reader.read_line(), Ok("a\n".to_string()));
564 assert_eq!(reader.read_line(), Ok("b\n".to_string()));
565 assert_eq!(reader.read_line(), Ok("c".to_string()));
566 assert!(reader.read_line().is_err());
571 let in_buf = MemReader::new(b"a\nb\nc".to_vec());
572 let mut reader = BufferedReader::with_capacity(2, in_buf);
573 let mut it = reader.lines();
574 assert_eq!(it.next(), Some(Ok("a\n".to_string())));
575 assert_eq!(it.next(), Some(Ok("b\n".to_string())));
576 assert_eq!(it.next(), Some(Ok("c".to_string())));
577 assert_eq!(it.next(), None);
581 fn test_short_reads() {
582 let inner = ShortReader{lengths: vec![0, 1, 2, 0, 1, 0]};
583 let mut reader = BufferedReader::new(inner);
584 let mut buf = [0, 0];
585 assert_eq!(reader.read(buf), Ok(0));
586 assert_eq!(reader.read(buf), Ok(1));
587 assert_eq!(reader.read(buf), Ok(2));
588 assert_eq!(reader.read(buf), Ok(0));
589 assert_eq!(reader.read(buf), Ok(1));
590 assert_eq!(reader.read(buf), Ok(0));
591 assert!(reader.read(buf).is_err());
595 fn read_char_buffered() {
596 let buf = [195u8, 159u8];
597 let mut reader = BufferedReader::with_capacity(1, BufReader::new(buf));
598 assert_eq!(reader.read_char(), Ok('ß'));
603 let buf = [195u8, 159u8, b'a'];
604 let mut reader = BufferedReader::with_capacity(1, BufReader::new(buf));
605 let mut it = reader.chars();
606 assert_eq!(it.next(), Some(Ok('ß')));
607 assert_eq!(it.next(), Some(Ok('a')));
608 assert_eq!(it.next(), None);
613 fn dont_panic_in_drop_on_panicked_flush() {
614 struct FailFlushWriter;
616 impl Writer for FailFlushWriter {
617 fn write(&mut self, _buf: &[u8]) -> IoResult<()> { Ok(()) }
618 fn flush(&mut self) -> IoResult<()> { Err(io::standard_error(EndOfFile)) }
621 let writer = FailFlushWriter;
622 let _writer = BufferedWriter::new(writer);
624 // If writer panics *again* due to the flush error then the process will abort.
629 fn bench_buffered_reader(b: &mut Bencher) {
631 BufferedReader::new(NullStream)
636 fn bench_buffered_writer(b: &mut Bencher) {
638 BufferedWriter::new(NullStream)
643 fn bench_buffered_stream(b: &mut Bencher) {
645 BufferedStream::new(NullStream);