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zynq-rs/libcoreio/src/io/buffered.rs

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add libconfig, libcoreio, szl from artiq-zynq a277e89b3ad; update dependencies
2020-09-09 17:56:50 +08:00
//! Buffering wrappers for I/O traits
use core::prelude::v1::*;
use crate::io::prelude::*;
use collections::vec::Vec;
use alloc::boxed::Box;
use core::cmp;
use core::fmt;
use crate::io::{
self, Error, ErrorKind, Initializer, SeekFrom, DEFAULT_BUF_SIZE,
};
/// 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(())
/// }
/// ```
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(())
/// }
/// ```
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(())
/// }
/// ```
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(())
/// }
/// ```
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(())
/// }
/// ```
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(())
/// }
/// ```
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
/// #![feature(buffered_io_capacity)]
/// 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(())
/// }
/// ```
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(())
/// }
/// ```
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.
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)
}
}
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)
}
// we can't skip unconditionally because of the large buffer case in read.
unsafe fn initializer(&self) -> Initializer {
self.inner.initializer()
}
}
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);
}
}
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()
}
}
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_value() 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 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
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)]
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());
/// ```
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);
/// ```
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();
/// ```
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();
/// ```
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();
/// ```
pub fn buffer(&self) -> &[u8] {
&self.buf
}
/// Returns the number of bytes the internal buffer can hold without flushing.
///
/// # Examples
///
/// ```no_run
/// #![feature(buffered_io_capacity)]
/// 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();
/// ```
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();
/// ```
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()),
}
}
}
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 flush(&mut self) -> io::Result<()> {
self.flush_buf().and_then(|()| self.get_mut().flush())
}
}
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()
}
}
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))
}
}
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.");
/// }
/// };
/// ```
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()
/// }
/// };
/// ```
pub fn into_inner(self) -> W {
self.0
}
}
impl<W> From<IntoInnerError<W>> for Error {
fn from(iie: IntoInnerError<W>) -> Error {
iie.1
}
}
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(())
/// }
/// ```
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(())
/// }
/// ```
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(())
/// }
/// ```
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(())
/// }
/// ```
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(())
/// }
/// ```
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(())
/// }
/// ```
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)
})
}
}
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),
}
}
fn flush(&mut self) -> io::Result<()> {
self.inner.flush()?;
self.need_flush = false;
Ok(())
}
}
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_value().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_value() - 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_value())).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_value())).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")
}
}
#[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")
}
}
}