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 collections::Collection;
17 use io::{Reader, Writer, Stream, Buffer, DEFAULT_BUF_SIZE, IoResult};
20 use option::{Some, None, Option};
21 use result::{Ok, Err};
22 use slice::{ImmutableSlice, MutableSlice};
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(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.
80 /// This type does not expose the ability to get a mutable reference to the
81 /// underlying reader because that could possibly corrupt the buffer.
82 pub fn get_ref<'a>(&'a self) -> &'a R { &self.inner }
84 /// Unwraps this `BufferedReader`, returning the underlying reader.
86 /// Note that any leftover data in the internal buffer is lost.
87 pub fn unwrap(self) -> R { self.inner }
90 impl<R: Reader> Buffer for BufferedReader<R> {
91 fn fill_buf<'a>(&'a mut self) -> IoResult<&'a [u8]> {
92 if self.pos == self.cap {
93 self.cap = try!(self.inner.read(self.buf.as_mut_slice()));
96 Ok(self.buf.slice(self.pos, self.cap))
99 fn consume(&mut self, amt: uint) {
101 assert!(self.pos <= self.cap);
105 impl<R: Reader> Reader for BufferedReader<R> {
106 fn read(&mut self, buf: &mut [u8]) -> IoResult<uint> {
108 let available = try!(self.fill_buf());
109 let nread = cmp::min(available.len(), buf.len());
110 slice::bytes::copy_memory(buf, available.slice_to(nread));
118 /// Wraps a Writer and buffers output to it
120 /// It can be excessively inefficient to work directly with a `Writer`. For
121 /// example, every call to `write` on `TcpStream` results in a system call. A
122 /// `BufferedWriter` keeps an in memory buffer of data and writes it to the
123 /// underlying `Writer` in large, infrequent batches.
125 /// This writer will be flushed when it is dropped.
130 /// # #![allow(unused_must_use)]
131 /// use std::io::{BufferedWriter, File};
133 /// let file = File::open(&Path::new("message.txt"));
134 /// let mut writer = BufferedWriter::new(file);
136 /// writer.write_str("hello, world");
139 pub struct BufferedWriter<W> {
145 impl<W: Writer> BufferedWriter<W> {
146 /// Creates a new `BufferedWriter` with the specified buffer capacity
147 pub fn with_capacity(cap: uint, inner: W) -> BufferedWriter<W> {
148 // See comments in BufferedReader for why this uses unsafe code.
149 let mut buf = Vec::with_capacity(cap);
150 unsafe { buf.set_len(cap); }
158 /// Creates a new `BufferedWriter` with a default buffer capacity
159 pub fn new(inner: W) -> BufferedWriter<W> {
160 BufferedWriter::with_capacity(DEFAULT_BUF_SIZE, inner)
163 fn flush_buf(&mut self) -> IoResult<()> {
165 let ret = self.inner.get_mut_ref().write(self.buf.slice_to(self.pos));
173 /// Gets a reference to the underlying writer.
175 /// This type does not expose the ability to get a mutable reference to the
176 /// underlying reader because that could possibly corrupt the buffer.
177 pub fn get_ref<'a>(&'a self) -> &'a W { self.inner.get_ref() }
179 /// Unwraps this `BufferedWriter`, returning the underlying writer.
181 /// The buffer is flushed before returning the writer.
182 pub fn unwrap(mut self) -> W {
183 // FIXME(#12628): is failing the right thing to do if flushing fails?
184 self.flush_buf().unwrap();
185 self.inner.take_unwrap()
189 impl<W: Writer> Writer for BufferedWriter<W> {
190 fn write(&mut self, buf: &[u8]) -> IoResult<()> {
191 if self.pos + buf.len() > self.buf.len() {
192 try!(self.flush_buf());
195 if buf.len() > self.buf.len() {
196 self.inner.get_mut_ref().write(buf)
198 let dst = self.buf.mut_slice_from(self.pos);
199 slice::bytes::copy_memory(dst, buf);
200 self.pos += buf.len();
205 fn flush(&mut self) -> IoResult<()> {
206 self.flush_buf().and_then(|()| self.inner.get_mut_ref().flush())
211 impl<W: Writer> Drop for BufferedWriter<W> {
213 if self.inner.is_some() {
214 // dtors should not fail, so we ignore a failed flush
215 let _ = self.flush_buf();
220 /// Wraps a Writer and buffers output to it, flushing whenever a newline (`0x0a`,
221 /// `'\n'`) is detected.
223 /// This writer will be flushed when it is dropped.
224 pub struct LineBufferedWriter<W> {
225 inner: BufferedWriter<W>,
228 impl<W: Writer> LineBufferedWriter<W> {
229 /// Creates a new `LineBufferedWriter`
230 pub fn new(inner: W) -> LineBufferedWriter<W> {
231 // Lines typically aren't that long, don't use a giant buffer
233 inner: BufferedWriter::with_capacity(1024, inner)
237 /// Gets a reference to the underlying writer.
239 /// This type does not expose the ability to get a mutable reference to the
240 /// underlying reader because that could possibly corrupt the buffer.
241 pub fn get_ref<'a>(&'a self) -> &'a W { self.inner.get_ref() }
243 /// Unwraps this `LineBufferedWriter`, returning the underlying writer.
245 /// The internal buffer is flushed before returning the writer.
246 pub fn unwrap(self) -> W { self.inner.unwrap() }
249 impl<W: Writer> Writer for LineBufferedWriter<W> {
250 fn write(&mut self, buf: &[u8]) -> IoResult<()> {
251 match buf.iter().rposition(|&b| b == b'\n') {
253 try!(self.inner.write(buf.slice_to(i + 1)));
254 try!(self.inner.flush());
255 try!(self.inner.write(buf.slice_from(i + 1)));
258 None => self.inner.write(buf),
262 fn flush(&mut self) -> IoResult<()> { self.inner.flush() }
265 struct InternalBufferedWriter<W>(BufferedWriter<W>);
267 impl<W> InternalBufferedWriter<W> {
268 fn get_mut_ref<'a>(&'a mut self) -> &'a mut BufferedWriter<W> {
269 let InternalBufferedWriter(ref mut w) = *self;
274 impl<W: Reader> Reader for InternalBufferedWriter<W> {
275 fn read(&mut self, buf: &mut [u8]) -> IoResult<uint> {
276 self.get_mut_ref().inner.get_mut_ref().read(buf)
280 /// Wraps a Stream and buffers input and output to and from it.
282 /// It can be excessively inefficient to work directly with a `Stream`. For
283 /// example, every call to `read` or `write` on `TcpStream` results in a system
284 /// call. A `BufferedStream` keeps in memory buffers of data, making large,
285 /// infrequent calls to `read` and `write` on the underlying `Stream`.
287 /// The output half will be flushed when this stream is dropped.
292 /// # #![allow(unused_must_use)]
293 /// use std::io::{BufferedStream, File};
295 /// let file = File::open(&Path::new("message.txt"));
296 /// let mut stream = BufferedStream::new(file);
298 /// stream.write("hello, world".as_bytes());
301 /// let mut buf = [0, ..100];
302 /// match stream.read(buf) {
303 /// Ok(nread) => println!("Read {} bytes", nread),
304 /// Err(e) => println!("error reading: {}", e)
307 pub struct BufferedStream<S> {
308 inner: BufferedReader<InternalBufferedWriter<S>>
311 impl<S: Stream> BufferedStream<S> {
312 /// Creates a new buffered stream with explicitly listed capacities for the
313 /// reader/writer buffer.
314 pub fn with_capacities(reader_cap: uint, writer_cap: uint, inner: S)
315 -> BufferedStream<S> {
316 let writer = BufferedWriter::with_capacity(writer_cap, inner);
317 let internal_writer = InternalBufferedWriter(writer);
318 let reader = BufferedReader::with_capacity(reader_cap,
320 BufferedStream { inner: reader }
323 /// Creates a new buffered stream with the default reader/writer buffer
325 pub fn new(inner: S) -> BufferedStream<S> {
326 BufferedStream::with_capacities(DEFAULT_BUF_SIZE, DEFAULT_BUF_SIZE,
330 /// Gets a reference to the underlying stream.
332 /// This type does not expose the ability to get a mutable reference to the
333 /// underlying reader because that could possibly corrupt the buffer.
334 pub fn get_ref<'a>(&'a self) -> &'a S {
335 let InternalBufferedWriter(ref w) = self.inner.inner;
339 /// Unwraps this `BufferedStream`, returning the underlying stream.
341 /// The internal buffer is flushed before returning the stream. Any leftover
342 /// data in the read buffer is lost.
343 pub fn unwrap(self) -> S {
344 let InternalBufferedWriter(w) = self.inner.inner;
349 impl<S: Stream> Buffer for BufferedStream<S> {
350 fn fill_buf<'a>(&'a mut self) -> IoResult<&'a [u8]> { self.inner.fill_buf() }
351 fn consume(&mut self, amt: uint) { self.inner.consume(amt) }
354 impl<S: Stream> Reader for BufferedStream<S> {
355 fn read(&mut self, buf: &mut [u8]) -> IoResult<uint> {
360 impl<S: Stream> Writer for BufferedStream<S> {
361 fn write(&mut self, buf: &[u8]) -> IoResult<()> {
362 self.inner.inner.get_mut_ref().write(buf)
364 fn flush(&mut self) -> IoResult<()> {
365 self.inner.inner.get_mut_ref().flush()
375 use super::super::{IoResult, EndOfFile};
376 use super::super::mem::{MemReader, MemWriter, BufReader};
377 use self::test::Bencher;
380 /// A type, free to create, primarily intended for benchmarking creation of
381 /// wrappers that, just for construction, don't need a Reader/Writer that
382 /// does anything useful. Is equivalent to `/dev/null` in semantics.
383 #[deriving(Clone,PartialEq,PartialOrd)]
384 pub struct NullStream;
386 impl Reader for NullStream {
387 fn read(&mut self, _: &mut [u8]) -> io::IoResult<uint> {
388 Err(io::standard_error(io::EndOfFile))
392 impl Writer for NullStream {
393 fn write(&mut self, _: &[u8]) -> io::IoResult<()> { Ok(()) }
396 /// A dummy reader intended at testing short-reads propagation.
397 pub struct ShortReader {
401 impl Reader for ShortReader {
402 fn read(&mut self, _: &mut [u8]) -> io::IoResult<uint> {
403 match self.lengths.shift() {
405 None => Err(io::standard_error(io::EndOfFile))
411 fn test_buffered_reader() {
412 let inner = MemReader::new(vec!(0, 1, 2, 3, 4));
413 let mut reader = BufferedReader::with_capacity(2, inner);
415 let mut buf = [0, 0, 0];
416 let nread = reader.read(buf);
417 assert_eq!(Ok(2), nread);
418 assert_eq!(buf.as_slice(), &[0, 1, 0]);
421 let nread = reader.read(buf);
422 assert_eq!(Ok(1), nread);
423 assert_eq!(buf.as_slice(), &[2]);
425 let mut buf = [0, 0, 0];
426 let nread = reader.read(buf);
427 assert_eq!(Ok(1), nread);
428 assert_eq!(buf.as_slice(), &[3, 0, 0]);
430 let nread = reader.read(buf);
431 assert_eq!(Ok(1), nread);
432 assert_eq!(buf.as_slice(), &[4, 0, 0]);
434 assert!(reader.read(buf).is_err());
438 fn test_buffered_writer() {
439 let inner = MemWriter::new();
440 let mut writer = BufferedWriter::with_capacity(2, inner);
442 writer.write([0, 1]).unwrap();
443 assert_eq!(writer.get_ref().get_ref(), &[]);
445 writer.write([2]).unwrap();
446 assert_eq!(writer.get_ref().get_ref(), &[0, 1]);
448 writer.write([3]).unwrap();
449 assert_eq!(writer.get_ref().get_ref(), &[0, 1]);
451 writer.flush().unwrap();
452 assert_eq!(&[0, 1, 2, 3], writer.get_ref().get_ref());
454 writer.write([4]).unwrap();
455 writer.write([5]).unwrap();
456 assert_eq!(&[0, 1, 2, 3], writer.get_ref().get_ref());
458 writer.write([6]).unwrap();
459 assert_eq!(&[0, 1, 2, 3, 4, 5],
460 writer.get_ref().get_ref());
462 writer.write([7, 8]).unwrap();
463 assert_eq!(&[0, 1, 2, 3, 4, 5, 6],
464 writer.get_ref().get_ref());
466 writer.write([9, 10, 11]).unwrap();
467 assert_eq!(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11],
468 writer.get_ref().get_ref());
470 writer.flush().unwrap();
471 assert_eq!(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11],
472 writer.get_ref().get_ref());
476 fn test_buffered_writer_inner_flushes() {
477 let mut w = BufferedWriter::with_capacity(3, MemWriter::new());
478 w.write([0, 1]).unwrap();
479 assert_eq!(&[], w.get_ref().get_ref());
481 assert_eq!(&[0, 1], w.get_ref());
484 // This is just here to make sure that we don't infinite loop in the
485 // newtype struct autoderef weirdness
487 fn test_buffered_stream() {
490 impl io::Writer for S {
491 fn write(&mut self, _: &[u8]) -> io::IoResult<()> { Ok(()) }
494 impl io::Reader for S {
495 fn read(&mut self, _: &mut [u8]) -> io::IoResult<uint> {
496 Err(io::standard_error(io::EndOfFile))
500 let mut stream = BufferedStream::new(S);
502 assert!(stream.read(buf).is_err());
503 stream.write(buf).unwrap();
504 stream.flush().unwrap();
508 fn test_read_until() {
509 let inner = MemReader::new(vec!(0, 1, 2, 1, 0));
510 let mut reader = BufferedReader::with_capacity(2, inner);
511 assert_eq!(reader.read_until(0), Ok(vec!(0)));
512 assert_eq!(reader.read_until(2), Ok(vec!(1, 2)));
513 assert_eq!(reader.read_until(1), Ok(vec!(1)));
514 assert_eq!(reader.read_until(8), Ok(vec!(0)));
515 assert!(reader.read_until(9).is_err());
519 fn test_line_buffer() {
520 let mut writer = LineBufferedWriter::new(MemWriter::new());
521 writer.write([0]).unwrap();
522 assert_eq!(writer.get_ref().get_ref(), &[]);
523 writer.write([1]).unwrap();
524 assert_eq!(writer.get_ref().get_ref(), &[]);
525 writer.flush().unwrap();
526 assert_eq!(writer.get_ref().get_ref(), &[0, 1]);
527 writer.write([0, b'\n', 1, b'\n', 2]).unwrap();
528 assert_eq!(writer.get_ref().get_ref(),
529 &[0, 1, 0, b'\n', 1, b'\n']);
530 writer.flush().unwrap();
531 assert_eq!(writer.get_ref().get_ref(),
532 &[0, 1, 0, b'\n', 1, b'\n', 2]);
533 writer.write([3, b'\n']).unwrap();
534 assert_eq!(writer.get_ref().get_ref(),
535 &[0, 1, 0, b'\n', 1, b'\n', 2, 3, b'\n']);
539 fn test_read_line() {
540 let in_buf = MemReader::new(Vec::from_slice(b"a\nb\nc"));
541 let mut reader = BufferedReader::with_capacity(2, in_buf);
542 assert_eq!(reader.read_line(), Ok("a\n".to_string()));
543 assert_eq!(reader.read_line(), Ok("b\n".to_string()));
544 assert_eq!(reader.read_line(), Ok("c".to_string()));
545 assert!(reader.read_line().is_err());
550 let in_buf = MemReader::new(Vec::from_slice(b"a\nb\nc"));
551 let mut reader = BufferedReader::with_capacity(2, in_buf);
552 let mut it = reader.lines();
553 assert_eq!(it.next(), Some(Ok("a\n".to_string())));
554 assert_eq!(it.next(), Some(Ok("b\n".to_string())));
555 assert_eq!(it.next(), Some(Ok("c".to_string())));
556 assert_eq!(it.next(), None);
560 fn test_short_reads() {
561 let inner = ShortReader{lengths: vec![0, 1, 2, 0, 1, 0]};
562 let mut reader = BufferedReader::new(inner);
563 let mut buf = [0, 0];
564 assert_eq!(reader.read(buf), Ok(0));
565 assert_eq!(reader.read(buf), Ok(1));
566 assert_eq!(reader.read(buf), Ok(2));
567 assert_eq!(reader.read(buf), Ok(0));
568 assert_eq!(reader.read(buf), Ok(1));
569 assert_eq!(reader.read(buf), Ok(0));
570 assert!(reader.read(buf).is_err());
574 fn read_char_buffered() {
575 let buf = [195u8, 159u8];
576 let mut reader = BufferedReader::with_capacity(1, BufReader::new(buf));
577 assert_eq!(reader.read_char(), Ok('ß'));
582 let buf = [195u8, 159u8, b'a'];
583 let mut reader = BufferedReader::with_capacity(1, BufReader::new(buf));
584 let mut it = reader.chars();
585 assert_eq!(it.next(), Some(Ok('ß')));
586 assert_eq!(it.next(), Some(Ok('a')));
587 assert_eq!(it.next(), None);
592 fn dont_fail_in_drop_on_failed_flush() {
593 struct FailFlushWriter;
595 impl Writer for FailFlushWriter {
596 fn write(&mut self, _buf: &[u8]) -> IoResult<()> { Ok(()) }
597 fn flush(&mut self) -> IoResult<()> { Err(io::standard_error(EndOfFile)) }
600 let writer = FailFlushWriter;
601 let _writer = BufferedWriter::new(writer);
603 // Trigger failure. If writer fails *again* due to the flush
604 // error then the process will abort.
609 fn bench_buffered_reader(b: &mut Bencher) {
611 BufferedReader::new(NullStream)
616 fn bench_buffered_writer(b: &mut Bencher) {
618 BufferedWriter::new(NullStream)
623 fn bench_buffered_stream(b: &mut Bencher) {
625 BufferedStream::new(NullStream);