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Diffstat (limited to 'library/std/src/io/buffered.rs')
| -rw-r--r-- | library/std/src/io/buffered.rs | 1703 |
1 files changed, 1703 insertions, 0 deletions
diff --git a/library/std/src/io/buffered.rs b/library/std/src/io/buffered.rs new file mode 100644 index 00000000000..b4c91cced43 --- /dev/null +++ b/library/std/src/io/buffered.rs @@ -0,0 +1,1703 @@ +//! Buffering wrappers for I/O traits + +use crate::io::prelude::*; + +use crate::cmp; +use crate::error; +use crate::fmt; +use crate::io::{ + self, Error, ErrorKind, Initializer, IoSlice, IoSliceMut, SeekFrom, DEFAULT_BUF_SIZE, +}; +use crate::memchr; + +/// The `BufReader<R>` struct adds buffering to any reader. +/// +/// It can be excessively inefficient to work directly with a [`Read`] instance. +/// For example, every call to [`read`][`TcpStream::read`] on [`TcpStream`] +/// results in a system call. A `BufReader<R>` performs large, infrequent reads on +/// the underlying [`Read`] and maintains an in-memory buffer of the results. +/// +/// `BufReader<R>` can improve the speed of programs that make *small* and +/// *repeated* read calls to the same file or network socket. It does not +/// help when reading very large amounts at once, or reading just one or a few +/// times. It also provides no advantage when reading from a source that is +/// already in memory, like a `Vec<u8>`. +/// +/// When the `BufReader<R>` is dropped, the contents of its buffer will be +/// discarded. Creating multiple instances of a `BufReader<R>` on the same +/// stream can cause data loss. Reading from the underlying reader after +/// unwrapping the `BufReader<R>` with `BufReader::into_inner` can also cause +/// data loss. +/// +/// [`Read`]: ../../std/io/trait.Read.html +/// [`TcpStream::read`]: ../../std/net/struct.TcpStream.html#method.read +/// [`TcpStream`]: ../../std/net/struct.TcpStream.html +/// +/// # Examples +/// +/// ```no_run +/// use std::io::prelude::*; +/// use std::io::BufReader; +/// use std::fs::File; +/// +/// fn main() -> std::io::Result<()> { +/// let f = File::open("log.txt")?; +/// let mut reader = BufReader::new(f); +/// +/// let mut line = String::new(); +/// let len = reader.read_line(&mut line)?; +/// println!("First line is {} bytes long", len); +/// Ok(()) +/// } +/// ``` +#[stable(feature = "rust1", since = "1.0.0")] +pub struct BufReader<R> { + inner: R, + buf: Box<[u8]>, + pos: usize, + cap: usize, +} + +impl<R: Read> BufReader<R> { + /// Creates a new `BufReader<R>` with a default buffer capacity. The default is currently 8 KB, + /// but may change in the future. + /// + /// # Examples + /// + /// ```no_run + /// use std::io::BufReader; + /// use std::fs::File; + /// + /// fn main() -> std::io::Result<()> { + /// let f = File::open("log.txt")?; + /// let reader = BufReader::new(f); + /// Ok(()) + /// } + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn new(inner: R) -> BufReader<R> { + BufReader::with_capacity(DEFAULT_BUF_SIZE, inner) + } + + /// Creates a new `BufReader<R>` with the specified buffer capacity. + /// + /// # Examples + /// + /// Creating a buffer with ten bytes of capacity: + /// + /// ```no_run + /// use std::io::BufReader; + /// use std::fs::File; + /// + /// fn main() -> std::io::Result<()> { + /// let f = File::open("log.txt")?; + /// let reader = BufReader::with_capacity(10, f); + /// Ok(()) + /// } + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn with_capacity(capacity: usize, inner: R) -> BufReader<R> { + unsafe { + let mut buffer = Vec::with_capacity(capacity); + buffer.set_len(capacity); + inner.initializer().initialize(&mut buffer); + BufReader { inner, buf: buffer.into_boxed_slice(), pos: 0, cap: 0 } + } + } +} + +impl<R> BufReader<R> { + /// Gets a reference to the underlying reader. + /// + /// It is inadvisable to directly read from the underlying reader. + /// + /// # Examples + /// + /// ```no_run + /// use std::io::BufReader; + /// use std::fs::File; + /// + /// fn main() -> std::io::Result<()> { + /// let f1 = File::open("log.txt")?; + /// let reader = BufReader::new(f1); + /// + /// let f2 = reader.get_ref(); + /// Ok(()) + /// } + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn get_ref(&self) -> &R { + &self.inner + } + + /// Gets a mutable reference to the underlying reader. + /// + /// It is inadvisable to directly read from the underlying reader. + /// + /// # Examples + /// + /// ```no_run + /// use std::io::BufReader; + /// use std::fs::File; + /// + /// fn main() -> std::io::Result<()> { + /// let f1 = File::open("log.txt")?; + /// let mut reader = BufReader::new(f1); + /// + /// let f2 = reader.get_mut(); + /// Ok(()) + /// } + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn get_mut(&mut self) -> &mut R { + &mut self.inner + } + + /// Returns a reference to the internally buffered data. + /// + /// Unlike `fill_buf`, this will not attempt to fill the buffer if it is empty. + /// + /// # Examples + /// + /// ```no_run + /// use std::io::{BufReader, BufRead}; + /// use std::fs::File; + /// + /// fn main() -> std::io::Result<()> { + /// let f = File::open("log.txt")?; + /// let mut reader = BufReader::new(f); + /// assert!(reader.buffer().is_empty()); + /// + /// if reader.fill_buf()?.len() > 0 { + /// assert!(!reader.buffer().is_empty()); + /// } + /// Ok(()) + /// } + /// ``` + #[stable(feature = "bufreader_buffer", since = "1.37.0")] + pub fn buffer(&self) -> &[u8] { + &self.buf[self.pos..self.cap] + } + + /// Returns the number of bytes the internal buffer can hold at once. + /// + /// # Examples + /// + /// ```no_run + /// use std::io::{BufReader, BufRead}; + /// use std::fs::File; + /// + /// fn main() -> std::io::Result<()> { + /// let f = File::open("log.txt")?; + /// let mut reader = BufReader::new(f); + /// + /// let capacity = reader.capacity(); + /// let buffer = reader.fill_buf()?; + /// assert!(buffer.len() <= capacity); + /// Ok(()) + /// } + /// ``` + #[stable(feature = "buffered_io_capacity", since = "1.46.0")] + pub fn capacity(&self) -> usize { + self.buf.len() + } + + /// Unwraps this `BufReader<R>`, returning the underlying reader. + /// + /// Note that any leftover data in the internal buffer is lost. Therefore, + /// a following read from the underlying reader may lead to data loss. + /// + /// # Examples + /// + /// ```no_run + /// use std::io::BufReader; + /// use std::fs::File; + /// + /// fn main() -> std::io::Result<()> { + /// let f1 = File::open("log.txt")?; + /// let reader = BufReader::new(f1); + /// + /// let f2 = reader.into_inner(); + /// Ok(()) + /// } + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn into_inner(self) -> R { + self.inner + } + + /// Invalidates all data in the internal buffer. + #[inline] + fn discard_buffer(&mut self) { + self.pos = 0; + self.cap = 0; + } +} + +impl<R: Seek> BufReader<R> { + /// Seeks relative to the current position. If the new position lies within the buffer, + /// the buffer will not be flushed, allowing for more efficient seeks. + /// This method does not return the location of the underlying reader, so the caller + /// must track this information themselves if it is required. + #[unstable(feature = "bufreader_seek_relative", issue = "31100")] + pub fn seek_relative(&mut self, offset: i64) -> io::Result<()> { + let pos = self.pos as u64; + if offset < 0 { + if let Some(new_pos) = pos.checked_sub((-offset) as u64) { + self.pos = new_pos as usize; + return Ok(()); + } + } else { + if let Some(new_pos) = pos.checked_add(offset as u64) { + if new_pos <= self.cap as u64 { + self.pos = new_pos as usize; + return Ok(()); + } + } + } + self.seek(SeekFrom::Current(offset)).map(drop) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<R: Read> Read for BufReader<R> { + fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> { + // If we don't have any buffered data and we're doing a massive read + // (larger than our internal buffer), bypass our internal buffer + // entirely. + if self.pos == self.cap && buf.len() >= self.buf.len() { + self.discard_buffer(); + return self.inner.read(buf); + } + let nread = { + let mut rem = self.fill_buf()?; + rem.read(buf)? + }; + self.consume(nread); + Ok(nread) + } + + fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> { + let total_len = bufs.iter().map(|b| b.len()).sum::<usize>(); + if self.pos == self.cap && total_len >= self.buf.len() { + self.discard_buffer(); + return self.inner.read_vectored(bufs); + } + let nread = { + let mut rem = self.fill_buf()?; + rem.read_vectored(bufs)? + }; + self.consume(nread); + Ok(nread) + } + + fn is_read_vectored(&self) -> bool { + self.inner.is_read_vectored() + } + + // we can't skip unconditionally because of the large buffer case in read. + unsafe fn initializer(&self) -> Initializer { + self.inner.initializer() + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<R: Read> BufRead for BufReader<R> { + fn fill_buf(&mut self) -> io::Result<&[u8]> { + // If we've reached the end of our internal buffer then we need to fetch + // some more data from the underlying reader. + // Branch using `>=` instead of the more correct `==` + // to tell the compiler that the pos..cap slice is always valid. + if self.pos >= self.cap { + debug_assert!(self.pos == self.cap); + self.cap = self.inner.read(&mut self.buf)?; + self.pos = 0; + } + Ok(&self.buf[self.pos..self.cap]) + } + + fn consume(&mut self, amt: usize) { + self.pos = cmp::min(self.pos + amt, self.cap); + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<R> fmt::Debug for BufReader<R> +where + R: fmt::Debug, +{ + fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { + fmt.debug_struct("BufReader") + .field("reader", &self.inner) + .field("buffer", &format_args!("{}/{}", self.cap - self.pos, self.buf.len())) + .finish() + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<R: Seek> Seek for BufReader<R> { + /// Seek to an offset, in bytes, in the underlying reader. + /// + /// The position used for seeking with `SeekFrom::Current(_)` is the + /// position the underlying reader would be at if the `BufReader<R>` had no + /// internal buffer. + /// + /// Seeking always discards the internal buffer, even if the seek position + /// would otherwise fall within it. This guarantees that calling + /// `.into_inner()` immediately after a seek yields the underlying reader + /// at the same position. + /// + /// To seek without discarding the internal buffer, use [`BufReader::seek_relative`]. + /// + /// See [`std::io::Seek`] for more details. + /// + /// Note: In the edge case where you're seeking with `SeekFrom::Current(n)` + /// where `n` minus the internal buffer length overflows an `i64`, two + /// seeks will be performed instead of one. If the second seek returns + /// `Err`, the underlying reader will be left at the same position it would + /// have if you called `seek` with `SeekFrom::Current(0)`. + /// + /// [`BufReader::seek_relative`]: struct.BufReader.html#method.seek_relative + /// [`std::io::Seek`]: trait.Seek.html + fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> { + let result: u64; + if let SeekFrom::Current(n) = pos { + let remainder = (self.cap - self.pos) as i64; + // it should be safe to assume that remainder fits within an i64 as the alternative + // means we managed to allocate 8 exbibytes and that's absurd. + // But it's not out of the realm of possibility for some weird underlying reader to + // support seeking by i64::MIN so we need to handle underflow when subtracting + // remainder. + if let Some(offset) = n.checked_sub(remainder) { + result = self.inner.seek(SeekFrom::Current(offset))?; + } else { + // seek backwards by our remainder, and then by the offset + self.inner.seek(SeekFrom::Current(-remainder))?; + self.discard_buffer(); + result = self.inner.seek(SeekFrom::Current(n))?; + } + } else { + // Seeking with Start/End doesn't care about our buffer length. + result = self.inner.seek(pos)?; + } + self.discard_buffer(); + Ok(result) + } +} + +/// Wraps a writer and buffers its output. +/// +/// It can be excessively inefficient to work directly with something that +/// implements [`Write`]. For example, every call to +/// [`write`][`TcpStream::write`] on [`TcpStream`] results in a system call. A +/// `BufWriter<W>` keeps an in-memory buffer of data and writes it to an underlying +/// writer in large, infrequent batches. +/// +/// `BufWriter<W>` can improve the speed of programs that make *small* and +/// *repeated* write calls to the same file or network socket. It does not +/// help when writing very large amounts at once, or writing just one or a few +/// times. It also provides no advantage when writing to a destination that is +/// in memory, like a `Vec<u8>`. +/// +/// It is critical to call [`flush`] before `BufWriter<W>` is dropped. Though +/// dropping will attempt to flush the contents of the buffer, any errors +/// that happen in the process of dropping will be ignored. Calling [`flush`] +/// ensures that the buffer is empty and thus dropping will not even attempt +/// file operations. +/// +/// # Examples +/// +/// Let's write the numbers one through ten to a [`TcpStream`]: +/// +/// ```no_run +/// use std::io::prelude::*; +/// use std::net::TcpStream; +/// +/// let mut stream = TcpStream::connect("127.0.0.1:34254").unwrap(); +/// +/// for i in 0..10 { +/// stream.write(&[i+1]).unwrap(); +/// } +/// ``` +/// +/// Because we're not buffering, we write each one in turn, incurring the +/// overhead of a system call per byte written. We can fix this with a +/// `BufWriter<W>`: +/// +/// ```no_run +/// use std::io::prelude::*; +/// use std::io::BufWriter; +/// use std::net::TcpStream; +/// +/// let mut stream = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap()); +/// +/// for i in 0..10 { +/// stream.write(&[i+1]).unwrap(); +/// } +/// stream.flush().unwrap(); +/// ``` +/// +/// By wrapping the stream with a `BufWriter<W>`, these ten writes are all grouped +/// together by the buffer and will all be written out in one system call when +/// the `stream` is flushed. +/// +/// [`Write`]: ../../std/io/trait.Write.html +/// [`TcpStream::write`]: ../../std/net/struct.TcpStream.html#method.write +/// [`TcpStream`]: ../../std/net/struct.TcpStream.html +/// [`flush`]: #method.flush +#[stable(feature = "rust1", since = "1.0.0")] +pub struct BufWriter<W: Write> { + inner: Option<W>, + buf: Vec<u8>, + // #30888: If the inner writer panics in a call to write, we don't want to + // write the buffered data a second time in BufWriter's destructor. This + // flag tells the Drop impl if it should skip the flush. + panicked: bool, +} + +/// An error returned by `into_inner` which combines an error that +/// happened while writing out the buffer, and the buffered writer object +/// which may be used to recover from the condition. +/// +/// # Examples +/// +/// ```no_run +/// use std::io::BufWriter; +/// use std::net::TcpStream; +/// +/// let mut stream = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap()); +/// +/// // do stuff with the stream +/// +/// // we want to get our `TcpStream` back, so let's try: +/// +/// let stream = match stream.into_inner() { +/// Ok(s) => s, +/// Err(e) => { +/// // Here, e is an IntoInnerError +/// panic!("An error occurred"); +/// } +/// }; +/// ``` +#[derive(Debug)] +#[stable(feature = "rust1", since = "1.0.0")] +pub struct IntoInnerError<W>(W, Error); + +impl<W: Write> BufWriter<W> { + /// Creates a new `BufWriter<W>` with a default buffer capacity. The default is currently 8 KB, + /// but may change in the future. + /// + /// # Examples + /// + /// ```no_run + /// use std::io::BufWriter; + /// use std::net::TcpStream; + /// + /// let mut buffer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap()); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn new(inner: W) -> BufWriter<W> { + BufWriter::with_capacity(DEFAULT_BUF_SIZE, inner) + } + + /// Creates a new `BufWriter<W>` with the specified buffer capacity. + /// + /// # Examples + /// + /// Creating a buffer with a buffer of a hundred bytes. + /// + /// ```no_run + /// use std::io::BufWriter; + /// use std::net::TcpStream; + /// + /// let stream = TcpStream::connect("127.0.0.1:34254").unwrap(); + /// let mut buffer = BufWriter::with_capacity(100, stream); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn with_capacity(capacity: usize, inner: W) -> BufWriter<W> { + BufWriter { inner: Some(inner), buf: Vec::with_capacity(capacity), panicked: false } + } + + fn flush_buf(&mut self) -> io::Result<()> { + let mut written = 0; + let len = self.buf.len(); + let mut ret = Ok(()); + while written < len { + self.panicked = true; + let r = self.inner.as_mut().unwrap().write(&self.buf[written..]); + self.panicked = false; + + match r { + Ok(0) => { + ret = + Err(Error::new(ErrorKind::WriteZero, "failed to write the buffered data")); + break; + } + Ok(n) => written += n, + Err(ref e) if e.kind() == io::ErrorKind::Interrupted => {} + Err(e) => { + ret = Err(e); + break; + } + } + } + if written > 0 { + self.buf.drain(..written); + } + ret + } + + /// Gets a reference to the underlying writer. + /// + /// # Examples + /// + /// ```no_run + /// use std::io::BufWriter; + /// use std::net::TcpStream; + /// + /// let mut buffer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap()); + /// + /// // we can use reference just like buffer + /// let reference = buffer.get_ref(); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn get_ref(&self) -> &W { + self.inner.as_ref().unwrap() + } + + /// Gets a mutable reference to the underlying writer. + /// + /// It is inadvisable to directly write to the underlying writer. + /// + /// # Examples + /// + /// ```no_run + /// use std::io::BufWriter; + /// use std::net::TcpStream; + /// + /// let mut buffer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap()); + /// + /// // we can use reference just like buffer + /// let reference = buffer.get_mut(); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn get_mut(&mut self) -> &mut W { + self.inner.as_mut().unwrap() + } + + /// Returns a reference to the internally buffered data. + /// + /// # Examples + /// + /// ```no_run + /// use std::io::BufWriter; + /// use std::net::TcpStream; + /// + /// let buf_writer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap()); + /// + /// // See how many bytes are currently buffered + /// let bytes_buffered = buf_writer.buffer().len(); + /// ``` + #[stable(feature = "bufreader_buffer", since = "1.37.0")] + pub fn buffer(&self) -> &[u8] { + &self.buf + } + + /// Returns the number of bytes the internal buffer can hold without flushing. + /// + /// # Examples + /// + /// ```no_run + /// use std::io::BufWriter; + /// use std::net::TcpStream; + /// + /// let buf_writer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap()); + /// + /// // Check the capacity of the inner buffer + /// let capacity = buf_writer.capacity(); + /// // Calculate how many bytes can be written without flushing + /// let without_flush = capacity - buf_writer.buffer().len(); + /// ``` + #[stable(feature = "buffered_io_capacity", since = "1.46.0")] + pub fn capacity(&self) -> usize { + self.buf.capacity() + } + + /// Unwraps this `BufWriter<W>`, returning the underlying writer. + /// + /// The buffer is written out before returning the writer. + /// + /// # Errors + /// + /// An `Err` will be returned if an error occurs while flushing the buffer. + /// + /// # Examples + /// + /// ```no_run + /// use std::io::BufWriter; + /// use std::net::TcpStream; + /// + /// let mut buffer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap()); + /// + /// // unwrap the TcpStream and flush the buffer + /// let stream = buffer.into_inner().unwrap(); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn into_inner(mut self) -> Result<W, IntoInnerError<BufWriter<W>>> { + match self.flush_buf() { + Err(e) => Err(IntoInnerError(self, e)), + Ok(()) => Ok(self.inner.take().unwrap()), + } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<W: Write> Write for BufWriter<W> { + fn write(&mut self, buf: &[u8]) -> io::Result<usize> { + if self.buf.len() + buf.len() > self.buf.capacity() { + self.flush_buf()?; + } + if buf.len() >= self.buf.capacity() { + self.panicked = true; + let r = self.get_mut().write(buf); + self.panicked = false; + r + } else { + self.buf.write(buf) + } + } + + fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> { + let total_len = bufs.iter().map(|b| b.len()).sum::<usize>(); + if self.buf.len() + total_len > self.buf.capacity() { + self.flush_buf()?; + } + if total_len >= self.buf.capacity() { + self.panicked = true; + let r = self.get_mut().write_vectored(bufs); + self.panicked = false; + r + } else { + self.buf.write_vectored(bufs) + } + } + + fn is_write_vectored(&self) -> bool { + self.get_ref().is_write_vectored() + } + + fn flush(&mut self) -> io::Result<()> { + self.flush_buf().and_then(|()| self.get_mut().flush()) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<W: Write> fmt::Debug for BufWriter<W> +where + W: fmt::Debug, +{ + fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { + fmt.debug_struct("BufWriter") + .field("writer", &self.inner.as_ref().unwrap()) + .field("buffer", &format_args!("{}/{}", self.buf.len(), self.buf.capacity())) + .finish() + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<W: Write + Seek> Seek for BufWriter<W> { + /// Seek to the offset, in bytes, in the underlying writer. + /// + /// Seeking always writes out the internal buffer before seeking. + fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> { + self.flush_buf().and_then(|_| self.get_mut().seek(pos)) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<W: Write> Drop for BufWriter<W> { + fn drop(&mut self) { + if self.inner.is_some() && !self.panicked { + // dtors should not panic, so we ignore a failed flush + let _r = self.flush_buf(); + } + } +} + +impl<W> IntoInnerError<W> { + /// Returns the error which caused the call to `into_inner()` to fail. + /// + /// This error was returned when attempting to write the internal buffer. + /// + /// # Examples + /// + /// ```no_run + /// use std::io::BufWriter; + /// use std::net::TcpStream; + /// + /// let mut stream = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap()); + /// + /// // do stuff with the stream + /// + /// // we want to get our `TcpStream` back, so let's try: + /// + /// let stream = match stream.into_inner() { + /// Ok(s) => s, + /// Err(e) => { + /// // Here, e is an IntoInnerError, let's log the inner error. + /// // + /// // We'll just 'log' to stdout for this example. + /// println!("{}", e.error()); + /// + /// panic!("An unexpected error occurred."); + /// } + /// }; + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn error(&self) -> &Error { + &self.1 + } + + /// Returns the buffered writer instance which generated the error. + /// + /// The returned object can be used for error recovery, such as + /// re-inspecting the buffer. + /// + /// # Examples + /// + /// ```no_run + /// use std::io::BufWriter; + /// use std::net::TcpStream; + /// + /// let mut stream = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap()); + /// + /// // do stuff with the stream + /// + /// // we want to get our `TcpStream` back, so let's try: + /// + /// let stream = match stream.into_inner() { + /// Ok(s) => s, + /// Err(e) => { + /// // Here, e is an IntoInnerError, let's re-examine the buffer: + /// let buffer = e.into_inner(); + /// + /// // do stuff to try to recover + /// + /// // afterwards, let's just return the stream + /// buffer.into_inner().unwrap() + /// } + /// }; + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn into_inner(self) -> W { + self.0 + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<W> From<IntoInnerError<W>> for Error { + fn from(iie: IntoInnerError<W>) -> Error { + iie.1 + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<W: Send + fmt::Debug> error::Error for IntoInnerError<W> { + #[allow(deprecated, deprecated_in_future)] + fn description(&self) -> &str { + error::Error::description(self.error()) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<W> fmt::Display for IntoInnerError<W> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + self.error().fmt(f) + } +} + +/// Wraps a writer and buffers output to it, flushing whenever a newline +/// (`0x0a`, `'\n'`) is detected. +/// +/// The [`BufWriter`][bufwriter] struct wraps a writer and buffers its output. +/// But it only does this batched write when it goes out of scope, or when the +/// internal buffer is full. Sometimes, you'd prefer to write each line as it's +/// completed, rather than the entire buffer at once. Enter `LineWriter`. It +/// does exactly that. +/// +/// Like [`BufWriter`][bufwriter], a `LineWriter`’s buffer will also be flushed when the +/// `LineWriter` goes out of scope or when its internal buffer is full. +/// +/// [bufwriter]: struct.BufWriter.html +/// +/// If there's still a partial line in the buffer when the `LineWriter` is +/// dropped, it will flush those contents. +/// +/// # Examples +/// +/// We can use `LineWriter` to write one line at a time, significantly +/// reducing the number of actual writes to the file. +/// +/// ```no_run +/// use std::fs::{self, File}; +/// use std::io::prelude::*; +/// use std::io::LineWriter; +/// +/// fn main() -> std::io::Result<()> { +/// let road_not_taken = b"I shall be telling this with a sigh +/// Somewhere ages and ages hence: +/// Two roads diverged in a wood, and I - +/// I took the one less traveled by, +/// And that has made all the difference."; +/// +/// let file = File::create("poem.txt")?; +/// let mut file = LineWriter::new(file); +/// +/// file.write_all(b"I shall be telling this with a sigh")?; +/// +/// // No bytes are written until a newline is encountered (or +/// // the internal buffer is filled). +/// assert_eq!(fs::read_to_string("poem.txt")?, ""); +/// file.write_all(b"\n")?; +/// assert_eq!( +/// fs::read_to_string("poem.txt")?, +/// "I shall be telling this with a sigh\n", +/// ); +/// +/// // Write the rest of the poem. +/// file.write_all(b"Somewhere ages and ages hence: +/// Two roads diverged in a wood, and I - +/// I took the one less traveled by, +/// And that has made all the difference.")?; +/// +/// // The last line of the poem doesn't end in a newline, so +/// // we have to flush or drop the `LineWriter` to finish +/// // writing. +/// file.flush()?; +/// +/// // Confirm the whole poem was written. +/// assert_eq!(fs::read("poem.txt")?, &road_not_taken[..]); +/// Ok(()) +/// } +/// ``` +#[stable(feature = "rust1", since = "1.0.0")] +pub struct LineWriter<W: Write> { + inner: BufWriter<W>, + need_flush: bool, +} + +impl<W: Write> LineWriter<W> { + /// Creates a new `LineWriter`. + /// + /// # Examples + /// + /// ```no_run + /// use std::fs::File; + /// use std::io::LineWriter; + /// + /// fn main() -> std::io::Result<()> { + /// let file = File::create("poem.txt")?; + /// let file = LineWriter::new(file); + /// Ok(()) + /// } + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn new(inner: W) -> LineWriter<W> { + // Lines typically aren't that long, don't use a giant buffer + LineWriter::with_capacity(1024, inner) + } + + /// Creates a new `LineWriter` with a specified capacity for the internal + /// buffer. + /// + /// # Examples + /// + /// ```no_run + /// use std::fs::File; + /// use std::io::LineWriter; + /// + /// fn main() -> std::io::Result<()> { + /// let file = File::create("poem.txt")?; + /// let file = LineWriter::with_capacity(100, file); + /// Ok(()) + /// } + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn with_capacity(capacity: usize, inner: W) -> LineWriter<W> { + LineWriter { inner: BufWriter::with_capacity(capacity, inner), need_flush: false } + } + + /// Gets a reference to the underlying writer. + /// + /// # Examples + /// + /// ```no_run + /// use std::fs::File; + /// use std::io::LineWriter; + /// + /// fn main() -> std::io::Result<()> { + /// let file = File::create("poem.txt")?; + /// let file = LineWriter::new(file); + /// + /// let reference = file.get_ref(); + /// Ok(()) + /// } + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn get_ref(&self) -> &W { + self.inner.get_ref() + } + + /// Gets a mutable reference to the underlying writer. + /// + /// Caution must be taken when calling methods on the mutable reference + /// returned as extra writes could corrupt the output stream. + /// + /// # Examples + /// + /// ```no_run + /// use std::fs::File; + /// use std::io::LineWriter; + /// + /// fn main() -> std::io::Result<()> { + /// let file = File::create("poem.txt")?; + /// let mut file = LineWriter::new(file); + /// + /// // we can use reference just like file + /// let reference = file.get_mut(); + /// Ok(()) + /// } + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn get_mut(&mut self) -> &mut W { + self.inner.get_mut() + } + + /// Unwraps this `LineWriter`, returning the underlying writer. + /// + /// The internal buffer is written out before returning the writer. + /// + /// # Errors + /// + /// An `Err` will be returned if an error occurs while flushing the buffer. + /// + /// # Examples + /// + /// ```no_run + /// use std::fs::File; + /// use std::io::LineWriter; + /// + /// fn main() -> std::io::Result<()> { + /// let file = File::create("poem.txt")?; + /// + /// let writer: LineWriter<File> = LineWriter::new(file); + /// + /// let file: File = writer.into_inner()?; + /// Ok(()) + /// } + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn into_inner(self) -> Result<W, IntoInnerError<LineWriter<W>>> { + self.inner.into_inner().map_err(|IntoInnerError(buf, e)| { + IntoInnerError(LineWriter { inner: buf, need_flush: false }, e) + }) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<W: Write> Write for LineWriter<W> { + fn write(&mut self, buf: &[u8]) -> io::Result<usize> { + if self.need_flush { + self.flush()?; + } + + // Find the last newline character in the buffer provided. If found then + // we're going to write all the data up to that point and then flush, + // otherwise we just write the whole block to the underlying writer. + let i = match memchr::memrchr(b'\n', buf) { + Some(i) => i, + None => return self.inner.write(buf), + }; + + // Ok, we're going to write a partial amount of the data given first + // followed by flushing the newline. After we've successfully written + // some data then we *must* report that we wrote that data, so future + // errors are ignored. We set our internal `need_flush` flag, though, in + // case flushing fails and we need to try it first next time. + let n = self.inner.write(&buf[..=i])?; + self.need_flush = true; + if self.flush().is_err() || n != i + 1 { + return Ok(n); + } + + // At this point we successfully wrote `i + 1` bytes and flushed it out, + // meaning that the entire line is now flushed out on the screen. While + // we can attempt to finish writing the rest of the data provided. + // Remember though that we ignore errors here as we've successfully + // written data, so we need to report that. + match self.inner.write(&buf[i + 1..]) { + Ok(i) => Ok(n + i), + Err(_) => Ok(n), + } + } + + // Vectored writes are very similar to the writes above, but adjusted for + // the list of buffers that we have to write. + fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> { + if self.need_flush { + self.flush()?; + } + + // Find the last newline, and failing that write the whole buffer + let last_newline = bufs.iter().enumerate().rev().find_map(|(i, buf)| { + let pos = memchr::memrchr(b'\n', buf)?; + Some((i, pos)) + }); + let (i, j) = match last_newline { + Some(pair) => pair, + None => return self.inner.write_vectored(bufs), + }; + let (prefix, suffix) = bufs.split_at(i); + let (buf, suffix) = suffix.split_at(1); + let buf = &buf[0]; + + // Write everything up to the last newline, flushing afterwards. Note + // that only if we finished our entire `write_vectored` do we try the + // subsequent + // `write` + let mut n = 0; + let prefix_amt = prefix.iter().map(|i| i.len()).sum(); + if prefix_amt > 0 { + n += self.inner.write_vectored(prefix)?; + self.need_flush = true; + } + if n == prefix_amt { + match self.inner.write(&buf[..=j]) { + Ok(m) => n += m, + Err(e) if n == 0 => return Err(e), + Err(_) => return Ok(n), + } + self.need_flush = true; + } + if self.flush().is_err() || n != j + 1 + prefix_amt { + return Ok(n); + } + + // ... and now write out everything remaining + match self.inner.write(&buf[j + 1..]) { + Ok(i) => n += i, + Err(_) => return Ok(n), + } + + if suffix.iter().map(|s| s.len()).sum::<usize>() == 0 { + return Ok(n); + } + match self.inner.write_vectored(suffix) { + Ok(i) => Ok(n + i), + Err(_) => Ok(n), + } + } + + fn flush(&mut self) -> io::Result<()> { + self.inner.flush()?; + self.need_flush = false; + Ok(()) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<W: Write> fmt::Debug for LineWriter<W> +where + W: fmt::Debug, +{ + fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { + fmt.debug_struct("LineWriter") + .field("writer", &self.inner.inner) + .field( + "buffer", + &format_args!("{}/{}", self.inner.buf.len(), self.inner.buf.capacity()), + ) + .finish() + } +} + +#[cfg(test)] +mod tests { + use crate::io::prelude::*; + use crate::io::{self, BufReader, BufWriter, IoSlice, LineWriter, SeekFrom}; + use crate::sync::atomic::{AtomicUsize, Ordering}; + use crate::thread; + + /// A dummy reader intended at testing short-reads propagation. + pub struct ShortReader { + lengths: Vec<usize>, + } + + impl Read for ShortReader { + fn read(&mut self, _: &mut [u8]) -> io::Result<usize> { + if self.lengths.is_empty() { Ok(0) } else { Ok(self.lengths.remove(0)) } + } + } + + #[test] + fn test_buffered_reader() { + let inner: &[u8] = &[5, 6, 7, 0, 1, 2, 3, 4]; + let mut reader = BufReader::with_capacity(2, inner); + + let mut buf = [0, 0, 0]; + let nread = reader.read(&mut buf); + assert_eq!(nread.unwrap(), 3); + assert_eq!(buf, [5, 6, 7]); + assert_eq!(reader.buffer(), []); + + let mut buf = [0, 0]; + let nread = reader.read(&mut buf); + assert_eq!(nread.unwrap(), 2); + assert_eq!(buf, [0, 1]); + assert_eq!(reader.buffer(), []); + + let mut buf = [0]; + let nread = reader.read(&mut buf); + assert_eq!(nread.unwrap(), 1); + assert_eq!(buf, [2]); + assert_eq!(reader.buffer(), [3]); + + let mut buf = [0, 0, 0]; + let nread = reader.read(&mut buf); + assert_eq!(nread.unwrap(), 1); + assert_eq!(buf, [3, 0, 0]); + assert_eq!(reader.buffer(), []); + + let nread = reader.read(&mut buf); + assert_eq!(nread.unwrap(), 1); + assert_eq!(buf, [4, 0, 0]); + assert_eq!(reader.buffer(), []); + + assert_eq!(reader.read(&mut buf).unwrap(), 0); + } + + #[test] + fn test_buffered_reader_seek() { + let inner: &[u8] = &[5, 6, 7, 0, 1, 2, 3, 4]; + let mut reader = BufReader::with_capacity(2, io::Cursor::new(inner)); + + assert_eq!(reader.seek(SeekFrom::Start(3)).ok(), Some(3)); + assert_eq!(reader.fill_buf().ok(), Some(&[0, 1][..])); + assert_eq!(reader.seek(SeekFrom::Current(0)).ok(), Some(3)); + assert_eq!(reader.fill_buf().ok(), Some(&[0, 1][..])); + assert_eq!(reader.seek(SeekFrom::Current(1)).ok(), Some(4)); + assert_eq!(reader.fill_buf().ok(), Some(&[1, 2][..])); + reader.consume(1); + assert_eq!(reader.seek(SeekFrom::Current(-2)).ok(), Some(3)); + } + + #[test] + fn test_buffered_reader_seek_relative() { + let inner: &[u8] = &[5, 6, 7, 0, 1, 2, 3, 4]; + let mut reader = BufReader::with_capacity(2, io::Cursor::new(inner)); + + assert!(reader.seek_relative(3).is_ok()); + assert_eq!(reader.fill_buf().ok(), Some(&[0, 1][..])); + assert!(reader.seek_relative(0).is_ok()); + assert_eq!(reader.fill_buf().ok(), Some(&[0, 1][..])); + assert!(reader.seek_relative(1).is_ok()); + assert_eq!(reader.fill_buf().ok(), Some(&[1][..])); + assert!(reader.seek_relative(-1).is_ok()); + assert_eq!(reader.fill_buf().ok(), Some(&[0, 1][..])); + assert!(reader.seek_relative(2).is_ok()); + assert_eq!(reader.fill_buf().ok(), Some(&[2, 3][..])); + } + + #[test] + fn test_buffered_reader_invalidated_after_read() { + let inner: &[u8] = &[5, 6, 7, 0, 1, 2, 3, 4]; + let mut reader = BufReader::with_capacity(3, io::Cursor::new(inner)); + + assert_eq!(reader.fill_buf().ok(), Some(&[5, 6, 7][..])); + reader.consume(3); + + let mut buffer = [0, 0, 0, 0, 0]; + assert_eq!(reader.read(&mut buffer).ok(), Some(5)); + assert_eq!(buffer, [0, 1, 2, 3, 4]); + + assert!(reader.seek_relative(-2).is_ok()); + let mut buffer = [0, 0]; + assert_eq!(reader.read(&mut buffer).ok(), Some(2)); + assert_eq!(buffer, [3, 4]); + } + + #[test] + fn test_buffered_reader_invalidated_after_seek() { + let inner: &[u8] = &[5, 6, 7, 0, 1, 2, 3, 4]; + let mut reader = BufReader::with_capacity(3, io::Cursor::new(inner)); + + assert_eq!(reader.fill_buf().ok(), Some(&[5, 6, 7][..])); + reader.consume(3); + + assert!(reader.seek(SeekFrom::Current(5)).is_ok()); + + assert!(reader.seek_relative(-2).is_ok()); + let mut buffer = [0, 0]; + assert_eq!(reader.read(&mut buffer).ok(), Some(2)); + assert_eq!(buffer, [3, 4]); + } + + #[test] + fn test_buffered_reader_seek_underflow() { + // gimmick reader that yields its position modulo 256 for each byte + struct PositionReader { + pos: u64, + } + impl Read for PositionReader { + fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> { + let len = buf.len(); + for x in buf { + *x = self.pos as u8; + self.pos = self.pos.wrapping_add(1); + } + Ok(len) + } + } + impl Seek for PositionReader { + fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> { + match pos { + SeekFrom::Start(n) => { + self.pos = n; + } + SeekFrom::Current(n) => { + self.pos = self.pos.wrapping_add(n as u64); + } + SeekFrom::End(n) => { + self.pos = u64::MAX.wrapping_add(n as u64); + } + } + Ok(self.pos) + } + } + + let mut reader = BufReader::with_capacity(5, PositionReader { pos: 0 }); + assert_eq!(reader.fill_buf().ok(), Some(&[0, 1, 2, 3, 4][..])); + assert_eq!(reader.seek(SeekFrom::End(-5)).ok(), Some(u64::MAX - 5)); + assert_eq!(reader.fill_buf().ok().map(|s| s.len()), Some(5)); + // the following seek will require two underlying seeks + let expected = 9223372036854775802; + assert_eq!(reader.seek(SeekFrom::Current(i64::MIN)).ok(), Some(expected)); + assert_eq!(reader.fill_buf().ok().map(|s| s.len()), Some(5)); + // seeking to 0 should empty the buffer. + assert_eq!(reader.seek(SeekFrom::Current(0)).ok(), Some(expected)); + assert_eq!(reader.get_ref().pos, expected); + } + + #[test] + fn test_buffered_reader_seek_underflow_discard_buffer_between_seeks() { + // gimmick reader that returns Err after first seek + struct ErrAfterFirstSeekReader { + first_seek: bool, + } + impl Read for ErrAfterFirstSeekReader { + fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> { + for x in &mut *buf { + *x = 0; + } + Ok(buf.len()) + } + } + impl Seek for ErrAfterFirstSeekReader { + fn seek(&mut self, _: SeekFrom) -> io::Result<u64> { + if self.first_seek { + self.first_seek = false; + Ok(0) + } else { + Err(io::Error::new(io::ErrorKind::Other, "oh no!")) + } + } + } + + let mut reader = BufReader::with_capacity(5, ErrAfterFirstSeekReader { first_seek: true }); + assert_eq!(reader.fill_buf().ok(), Some(&[0, 0, 0, 0, 0][..])); + + // The following seek will require two underlying seeks. The first will + // succeed but the second will fail. This should still invalidate the + // buffer. + assert!(reader.seek(SeekFrom::Current(i64::MIN)).is_err()); + assert_eq!(reader.buffer().len(), 0); + } + + #[test] + fn test_buffered_writer() { + let inner = Vec::new(); + let mut writer = BufWriter::with_capacity(2, inner); + + writer.write(&[0, 1]).unwrap(); + assert_eq!(writer.buffer(), []); + assert_eq!(*writer.get_ref(), [0, 1]); + + writer.write(&[2]).unwrap(); + assert_eq!(writer.buffer(), [2]); + assert_eq!(*writer.get_ref(), [0, 1]); + + writer.write(&[3]).unwrap(); + assert_eq!(writer.buffer(), [2, 3]); + assert_eq!(*writer.get_ref(), [0, 1]); + + writer.flush().unwrap(); + assert_eq!(writer.buffer(), []); + assert_eq!(*writer.get_ref(), [0, 1, 2, 3]); + + writer.write(&[4]).unwrap(); + writer.write(&[5]).unwrap(); + assert_eq!(writer.buffer(), [4, 5]); + assert_eq!(*writer.get_ref(), [0, 1, 2, 3]); + + writer.write(&[6]).unwrap(); + assert_eq!(writer.buffer(), [6]); + assert_eq!(*writer.get_ref(), [0, 1, 2, 3, 4, 5]); + + writer.write(&[7, 8]).unwrap(); + assert_eq!(writer.buffer(), []); + assert_eq!(*writer.get_ref(), [0, 1, 2, 3, 4, 5, 6, 7, 8]); + + writer.write(&[9, 10, 11]).unwrap(); + assert_eq!(writer.buffer(), []); + assert_eq!(*writer.get_ref(), [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]); + + writer.flush().unwrap(); + assert_eq!(writer.buffer(), []); + assert_eq!(*writer.get_ref(), [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]); + } + + #[test] + fn test_buffered_writer_inner_flushes() { + let mut w = BufWriter::with_capacity(3, Vec::new()); + w.write(&[0, 1]).unwrap(); + assert_eq!(*w.get_ref(), []); + let w = w.into_inner().unwrap(); + assert_eq!(w, [0, 1]); + } + + #[test] + fn test_buffered_writer_seek() { + let mut w = BufWriter::with_capacity(3, io::Cursor::new(Vec::new())); + w.write_all(&[0, 1, 2, 3, 4, 5]).unwrap(); + w.write_all(&[6, 7]).unwrap(); + assert_eq!(w.seek(SeekFrom::Current(0)).ok(), Some(8)); + assert_eq!(&w.get_ref().get_ref()[..], &[0, 1, 2, 3, 4, 5, 6, 7][..]); + assert_eq!(w.seek(SeekFrom::Start(2)).ok(), Some(2)); + w.write_all(&[8, 9]).unwrap(); + assert_eq!(&w.into_inner().unwrap().into_inner()[..], &[0, 1, 8, 9, 4, 5, 6, 7]); + } + + #[test] + fn test_read_until() { + let inner: &[u8] = &[0, 1, 2, 1, 0]; + let mut reader = BufReader::with_capacity(2, inner); + let mut v = Vec::new(); + reader.read_until(0, &mut v).unwrap(); + assert_eq!(v, [0]); + v.truncate(0); + reader.read_until(2, &mut v).unwrap(); + assert_eq!(v, [1, 2]); + v.truncate(0); + reader.read_until(1, &mut v).unwrap(); + assert_eq!(v, [1]); + v.truncate(0); + reader.read_until(8, &mut v).unwrap(); + assert_eq!(v, [0]); + v.truncate(0); + reader.read_until(9, &mut v).unwrap(); + assert_eq!(v, []); + } + + #[test] + fn test_line_buffer_fail_flush() { + // Issue #32085 + struct FailFlushWriter<'a>(&'a mut Vec<u8>); + + impl Write for FailFlushWriter<'_> { + fn write(&mut self, buf: &[u8]) -> io::Result<usize> { + self.0.extend_from_slice(buf); + Ok(buf.len()) + } + fn flush(&mut self) -> io::Result<()> { + Err(io::Error::new(io::ErrorKind::Other, "flush failed")) + } + } + + let mut buf = Vec::new(); + { + let mut writer = LineWriter::new(FailFlushWriter(&mut buf)); + let to_write = b"abc\ndef"; + if let Ok(written) = writer.write(to_write) { + assert!(written < to_write.len(), "didn't flush on new line"); + // PASS + return; + } + } + assert!(buf.is_empty(), "write returned an error but wrote data"); + } + + #[test] + fn test_line_buffer() { + let mut writer = LineWriter::new(Vec::new()); + writer.write(&[0]).unwrap(); + assert_eq!(*writer.get_ref(), []); + writer.write(&[1]).unwrap(); + assert_eq!(*writer.get_ref(), []); + writer.flush().unwrap(); + assert_eq!(*writer.get_ref(), [0, 1]); + writer.write(&[0, b'\n', 1, b'\n', 2]).unwrap(); + assert_eq!(*writer.get_ref(), [0, 1, 0, b'\n', 1, b'\n']); + writer.flush().unwrap(); + assert_eq!(*writer.get_ref(), [0, 1, 0, b'\n', 1, b'\n', 2]); + writer.write(&[3, b'\n']).unwrap(); + assert_eq!(*writer.get_ref(), [0, 1, 0, b'\n', 1, b'\n', 2, 3, b'\n']); + } + + #[test] + fn test_read_line() { + let in_buf: &[u8] = b"a\nb\nc"; + let mut reader = BufReader::with_capacity(2, in_buf); + let mut s = String::new(); + reader.read_line(&mut s).unwrap(); + assert_eq!(s, "a\n"); + s.truncate(0); + reader.read_line(&mut s).unwrap(); + assert_eq!(s, "b\n"); + s.truncate(0); + reader.read_line(&mut s).unwrap(); + assert_eq!(s, "c"); + s.truncate(0); + reader.read_line(&mut s).unwrap(); + assert_eq!(s, ""); + } + + #[test] + fn test_lines() { + let in_buf: &[u8] = b"a\nb\nc"; + let reader = BufReader::with_capacity(2, in_buf); + let mut it = reader.lines(); + assert_eq!(it.next().unwrap().unwrap(), "a".to_string()); + assert_eq!(it.next().unwrap().unwrap(), "b".to_string()); + assert_eq!(it.next().unwrap().unwrap(), "c".to_string()); + assert!(it.next().is_none()); + } + + #[test] + fn test_short_reads() { + let inner = ShortReader { lengths: vec![0, 1, 2, 0, 1, 0] }; + let mut reader = BufReader::new(inner); + let mut buf = [0, 0]; + assert_eq!(reader.read(&mut buf).unwrap(), 0); + assert_eq!(reader.read(&mut buf).unwrap(), 1); + assert_eq!(reader.read(&mut buf).unwrap(), 2); + assert_eq!(reader.read(&mut buf).unwrap(), 0); + assert_eq!(reader.read(&mut buf).unwrap(), 1); + assert_eq!(reader.read(&mut buf).unwrap(), 0); + assert_eq!(reader.read(&mut buf).unwrap(), 0); + } + + #[test] + #[should_panic] + fn dont_panic_in_drop_on_panicked_flush() { + struct FailFlushWriter; + + impl Write for FailFlushWriter { + fn write(&mut self, buf: &[u8]) -> io::Result<usize> { + Ok(buf.len()) + } + fn flush(&mut self) -> io::Result<()> { + Err(io::Error::last_os_error()) + } + } + + let writer = FailFlushWriter; + let _writer = BufWriter::new(writer); + + // If writer panics *again* due to the flush error then the process will + // abort. + panic!(); + } + + #[test] + #[cfg_attr(target_os = "emscripten", ignore)] + fn panic_in_write_doesnt_flush_in_drop() { + static WRITES: AtomicUsize = AtomicUsize::new(0); + + struct PanicWriter; + + impl Write for PanicWriter { + fn write(&mut self, _: &[u8]) -> io::Result<usize> { + WRITES.fetch_add(1, Ordering::SeqCst); + panic!(); + } + fn flush(&mut self) -> io::Result<()> { + Ok(()) + } + } + + thread::spawn(|| { + let mut writer = BufWriter::new(PanicWriter); + let _ = writer.write(b"hello world"); + let _ = writer.flush(); + }) + .join() + .unwrap_err(); + + assert_eq!(WRITES.load(Ordering::SeqCst), 1); + } + + #[bench] + fn bench_buffered_reader(b: &mut test::Bencher) { + b.iter(|| BufReader::new(io::empty())); + } + + #[bench] + fn bench_buffered_writer(b: &mut test::Bencher) { + b.iter(|| BufWriter::new(io::sink())); + } + + struct AcceptOneThenFail { + written: bool, + flushed: bool, + } + + impl Write for AcceptOneThenFail { + fn write(&mut self, data: &[u8]) -> io::Result<usize> { + if !self.written { + assert_eq!(data, b"a\nb\n"); + self.written = true; + Ok(data.len()) + } else { + Err(io::Error::new(io::ErrorKind::NotFound, "test")) + } + } + + fn flush(&mut self) -> io::Result<()> { + assert!(self.written); + assert!(!self.flushed); + self.flushed = true; + Err(io::Error::new(io::ErrorKind::Other, "test")) + } + } + + #[test] + fn erroneous_flush_retried() { + let a = AcceptOneThenFail { written: false, flushed: false }; + + let mut l = LineWriter::new(a); + assert_eq!(l.write(b"a\nb\na").unwrap(), 4); + assert!(l.get_ref().written); + assert!(l.get_ref().flushed); + l.get_mut().flushed = false; + + assert_eq!(l.write(b"a").unwrap_err().kind(), io::ErrorKind::Other) + } + + #[test] + fn line_vectored() { + let mut a = LineWriter::new(Vec::new()); + assert_eq!( + a.write_vectored(&[ + IoSlice::new(&[]), + IoSlice::new(b"\n"), + IoSlice::new(&[]), + IoSlice::new(b"a"), + ]) + .unwrap(), + 2, + ); + assert_eq!(a.get_ref(), b"\n"); + + assert_eq!( + a.write_vectored(&[ + IoSlice::new(&[]), + IoSlice::new(b"b"), + IoSlice::new(&[]), + IoSlice::new(b"a"), + IoSlice::new(&[]), + IoSlice::new(b"c"), + ]) + .unwrap(), + 3, + ); + assert_eq!(a.get_ref(), b"\n"); + a.flush().unwrap(); + assert_eq!(a.get_ref(), b"\nabac"); + assert_eq!(a.write_vectored(&[]).unwrap(), 0); + assert_eq!( + a.write_vectored(&[ + IoSlice::new(&[]), + IoSlice::new(&[]), + IoSlice::new(&[]), + IoSlice::new(&[]), + ]) + .unwrap(), + 0, + ); + assert_eq!(a.write_vectored(&[IoSlice::new(b"a\nb"),]).unwrap(), 3); + assert_eq!(a.get_ref(), b"\nabaca\n"); + } + + #[test] + fn line_vectored_partial_and_errors() { + enum Call { + Write { inputs: Vec<&'static [u8]>, output: io::Result<usize> }, + Flush { output: io::Result<()> }, + } + struct Writer { + calls: Vec<Call>, + } + + impl Write for Writer { + fn write(&mut self, buf: &[u8]) -> io::Result<usize> { + self.write_vectored(&[IoSlice::new(buf)]) + } + + fn write_vectored(&mut self, buf: &[IoSlice<'_>]) -> io::Result<usize> { + match self.calls.pop().unwrap() { + Call::Write { inputs, output } => { + assert_eq!(inputs, buf.iter().map(|b| &**b).collect::<Vec<_>>()); + output + } + _ => panic!("unexpected call to write"), + } + } + + fn flush(&mut self) -> io::Result<()> { + match self.calls.pop().unwrap() { + Call::Flush { output } => output, + _ => panic!("unexpected call to flush"), + } + } + } + + impl Drop for Writer { + fn drop(&mut self) { + if !thread::panicking() { + assert_eq!(self.calls.len(), 0); + } + } + } + + // partial writes keep going + let mut a = LineWriter::new(Writer { calls: Vec::new() }); + a.write_vectored(&[IoSlice::new(&[]), IoSlice::new(b"abc")]).unwrap(); + a.get_mut().calls.push(Call::Flush { output: Ok(()) }); + a.get_mut().calls.push(Call::Write { inputs: vec![b"bcx\n"], output: Ok(4) }); + a.get_mut().calls.push(Call::Write { inputs: vec![b"abcx\n"], output: Ok(1) }); + a.write_vectored(&[IoSlice::new(b"x"), IoSlice::new(b"\n")]).unwrap(); + a.get_mut().calls.push(Call::Flush { output: Ok(()) }); + a.flush().unwrap(); + + // erroneous writes stop and don't write more + a.get_mut().calls.push(Call::Write { inputs: vec![b"x\n"], output: Err(err()) }); + assert_eq!(a.write_vectored(&[IoSlice::new(b"x"), IoSlice::new(b"\na")]).unwrap(), 2); + a.get_mut().calls.push(Call::Flush { output: Ok(()) }); + a.get_mut().calls.push(Call::Write { inputs: vec![b"x\n"], output: Ok(2) }); + a.flush().unwrap(); + + fn err() -> io::Error { + io::Error::new(io::ErrorKind::Other, "x") + } + } +} |