1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
//! `UnixStream` split support.
//!
//! A `UnixStream` can be split into a read half and a write half with
//! `UnixStream::split`. The read half implements `AsyncRead` while the write
//! half implements `AsyncWrite`.
//!
//! Compared to the generic split of `AsyncRead + AsyncWrite`, this specialized
//! split has no associated overhead and enforces all invariants at the type
//! level.

use crate::io::{AsyncRead, AsyncWrite, Interest, ReadBuf, Ready};
use crate::net::UnixStream;

use crate::net::unix::SocketAddr;
use std::io;
use std::net::Shutdown;
use std::pin::Pin;
use std::task::{Context, Poll};

cfg_io_util! {
    use bytes::BufMut;
}

/// Borrowed read half of a [`UnixStream`], created by [`split`].
///
/// Reading from a `ReadHalf` is usually done using the convenience methods found on the
/// [`AsyncReadExt`] trait.
///
/// [`UnixStream`]: UnixStream
/// [`split`]: UnixStream::split()
/// [`AsyncReadExt`]: trait@crate::io::AsyncReadExt
#[derive(Debug)]
pub struct ReadHalf<'a>(&'a UnixStream);

/// Borrowed write half of a [`UnixStream`], created by [`split`].
///
/// Note that in the [`AsyncWrite`] implementation of this type, [`poll_shutdown`] will
/// shut down the UnixStream stream in the write direction.
///
/// Writing to an `WriteHalf` is usually done using the convenience methods found
/// on the [`AsyncWriteExt`] trait.
///
/// [`UnixStream`]: UnixStream
/// [`split`]: UnixStream::split()
/// [`AsyncWrite`]: trait@crate::io::AsyncWrite
/// [`poll_shutdown`]: fn@crate::io::AsyncWrite::poll_shutdown
/// [`AsyncWriteExt`]: trait@crate::io::AsyncWriteExt
#[derive(Debug)]
pub struct WriteHalf<'a>(&'a UnixStream);

pub(crate) fn split(stream: &mut UnixStream) -> (ReadHalf<'_>, WriteHalf<'_>) {
    (ReadHalf(stream), WriteHalf(stream))
}

impl ReadHalf<'_> {
    /// Wait for any of the requested ready states.
    ///
    /// This function is usually paired with `try_read()` or `try_write()`. It
    /// can be used to concurrently read / write to the same socket on a single
    /// task without splitting the socket.
    ///
    /// # Cancel safety
    ///
    /// This method is cancel safe. Once a readiness event occurs, the method
    /// will continue to return immediately until the readiness event is
    /// consumed by an attempt to read or write that fails with `WouldBlock` or
    /// `Poll::Pending`.
    pub async fn ready(&self, interest: Interest) -> io::Result<Ready> {
        self.0.ready(interest).await
    }

    /// Waits for the socket to become readable.
    ///
    /// This function is equivalent to `ready(Interest::READABLE)` and is usually
    /// paired with `try_read()`.
    ///
    /// # Cancel safety
    ///
    /// This method is cancel safe. Once a readiness event occurs, the method
    /// will continue to return immediately until the readiness event is
    /// consumed by an attempt to read that fails with `WouldBlock` or
    /// `Poll::Pending`.
    pub async fn readable(&self) -> io::Result<()> {
        self.0.readable().await
    }

    /// Tries to read data from the stream into the provided buffer, returning how
    /// many bytes were read.
    ///
    /// Receives any pending data from the socket but does not wait for new data
    /// to arrive. On success, returns the number of bytes read. Because
    /// `try_read()` is non-blocking, the buffer does not have to be stored by
    /// the async task and can exist entirely on the stack.
    ///
    /// Usually, [`readable()`] or [`ready()`] is used with this function.
    ///
    /// [`readable()`]: Self::readable()
    /// [`ready()`]: Self::ready()
    ///
    /// # Return
    ///
    /// If data is successfully read, `Ok(n)` is returned, where `n` is the
    /// number of bytes read. If `n` is `0`, then it can indicate one of two scenarios:
    ///
    /// 1. The stream's read half is closed and will no longer yield data.
    /// 2. The specified buffer was 0 bytes in length.
    ///
    /// If the stream is not ready to read data,
    /// `Err(io::ErrorKind::WouldBlock)` is returned.
    pub fn try_read(&self, buf: &mut [u8]) -> io::Result<usize> {
        self.0.try_read(buf)
    }

    cfg_io_util! {
        /// Tries to read data from the stream into the provided buffer, advancing the
        /// buffer's internal cursor, returning how many bytes were read.
        ///
        /// Receives any pending data from the socket but does not wait for new data
        /// to arrive. On success, returns the number of bytes read. Because
        /// `try_read_buf()` is non-blocking, the buffer does not have to be stored by
        /// the async task and can exist entirely on the stack.
        ///
        /// Usually, [`readable()`] or [`ready()`] is used with this function.
        ///
        /// [`readable()`]: Self::readable()
        /// [`ready()`]: Self::ready()
        ///
        /// # Return
        ///
        /// If data is successfully read, `Ok(n)` is returned, where `n` is the
        /// number of bytes read. `Ok(0)` indicates the stream's read half is closed
        /// and will no longer yield data. If the stream is not ready to read data
        pub fn try_read_buf<B: BufMut>(&self, buf: &mut B) -> io::Result<usize> {
            self.0.try_read_buf(buf)
        }
    }

    /// Tries to read data from the stream into the provided buffers, returning
    /// how many bytes were read.
    ///
    /// Data is copied to fill each buffer in order, with the final buffer
    /// written to possibly being only partially filled. This method behaves
    /// equivalently to a single call to [`try_read()`] with concatenated
    /// buffers.
    ///
    /// Receives any pending data from the socket but does not wait for new data
    /// to arrive. On success, returns the number of bytes read. Because
    /// `try_read_vectored()` is non-blocking, the buffer does not have to be
    /// stored by the async task and can exist entirely on the stack.
    ///
    /// Usually, [`readable()`] or [`ready()`] is used with this function.
    ///
    /// [`try_read()`]: Self::try_read()
    /// [`readable()`]: Self::readable()
    /// [`ready()`]: Self::ready()
    ///
    /// # Return
    ///
    /// If data is successfully read, `Ok(n)` is returned, where `n` is the
    /// number of bytes read. `Ok(0)` indicates the stream's read half is closed
    /// and will no longer yield data. If the stream is not ready to read data
    /// `Err(io::ErrorKind::WouldBlock)` is returned.
    pub fn try_read_vectored(&self, bufs: &mut [io::IoSliceMut<'_>]) -> io::Result<usize> {
        self.0.try_read_vectored(bufs)
    }

    /// Returns the socket address of the remote half of this connection.
    pub fn peer_addr(&self) -> io::Result<SocketAddr> {
        self.0.peer_addr()
    }

    /// Returns the socket address of the local half of this connection.
    pub fn local_addr(&self) -> io::Result<SocketAddr> {
        self.0.local_addr()
    }
}

impl WriteHalf<'_> {
    /// Waits for any of the requested ready states.
    ///
    /// This function is usually paired with `try_read()` or `try_write()`. It
    /// can be used to concurrently read / write to the same socket on a single
    /// task without splitting the socket.
    ///
    /// The function may complete without the socket being ready. This is a
    /// false-positive and attempting an operation will return with
    /// `io::ErrorKind::WouldBlock`. The function can also return with an empty
    /// [`Ready`] set, so you should always check the returned value and possibly
    /// wait again if the requested states are not set.
    ///
    /// # Cancel safety
    ///
    /// This method is cancel safe. Once a readiness event occurs, the method
    /// will continue to return immediately until the readiness event is
    /// consumed by an attempt to read or write that fails with `WouldBlock` or
    /// `Poll::Pending`.
    pub async fn ready(&self, interest: Interest) -> io::Result<Ready> {
        self.0.ready(interest).await
    }

    /// Waits for the socket to become writable.
    ///
    /// This function is equivalent to `ready(Interest::WRITABLE)` and is usually
    /// paired with `try_write()`.
    ///
    /// # Cancel safety
    ///
    /// This method is cancel safe. Once a readiness event occurs, the method
    /// will continue to return immediately until the readiness event is
    /// consumed by an attempt to write that fails with `WouldBlock` or
    /// `Poll::Pending`.
    pub async fn writable(&self) -> io::Result<()> {
        self.0.writable().await
    }

    /// Tries to write a buffer to the stream, returning how many bytes were
    /// written.
    ///
    /// The function will attempt to write the entire contents of `buf`, but
    /// only part of the buffer may be written.
    ///
    /// This function is usually paired with `writable()`.
    ///
    /// # Return
    ///
    /// If data is successfully written, `Ok(n)` is returned, where `n` is the
    /// number of bytes written. If the stream is not ready to write data,
    /// `Err(io::ErrorKind::WouldBlock)` is returned.
    pub fn try_write(&self, buf: &[u8]) -> io::Result<usize> {
        self.0.try_write(buf)
    }

    /// Tries to write several buffers to the stream, returning how many bytes
    /// were written.
    ///
    /// Data is written from each buffer in order, with the final buffer read
    /// from possible being only partially consumed. This method behaves
    /// equivalently to a single call to [`try_write()`] with concatenated
    /// buffers.
    ///
    /// This function is usually paired with `writable()`.
    ///
    /// [`try_write()`]: Self::try_write()
    ///
    /// # Return
    ///
    /// If data is successfully written, `Ok(n)` is returned, where `n` is the
    /// number of bytes written. If the stream is not ready to write data,
    /// `Err(io::ErrorKind::WouldBlock)` is returned.
    pub fn try_write_vectored(&self, buf: &[io::IoSlice<'_>]) -> io::Result<usize> {
        self.0.try_write_vectored(buf)
    }

    /// Returns the socket address of the remote half of this connection.
    pub fn peer_addr(&self) -> io::Result<SocketAddr> {
        self.0.peer_addr()
    }

    /// Returns the socket address of the local half of this connection.
    pub fn local_addr(&self) -> io::Result<SocketAddr> {
        self.0.local_addr()
    }
}

impl AsyncRead for ReadHalf<'_> {
    fn poll_read(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        buf: &mut ReadBuf<'_>,
    ) -> Poll<io::Result<()>> {
        self.0.poll_read_priv(cx, buf)
    }
}

impl AsyncWrite for WriteHalf<'_> {
    fn poll_write(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        buf: &[u8],
    ) -> Poll<io::Result<usize>> {
        self.0.poll_write_priv(cx, buf)
    }

    fn poll_write_vectored(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        bufs: &[io::IoSlice<'_>],
    ) -> Poll<io::Result<usize>> {
        self.0.poll_write_vectored_priv(cx, bufs)
    }

    fn is_write_vectored(&self) -> bool {
        self.0.is_write_vectored()
    }

    fn poll_flush(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<io::Result<()>> {
        Poll::Ready(Ok(()))
    }

    fn poll_shutdown(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<io::Result<()>> {
        self.0.shutdown_std(Shutdown::Write).into()
    }
}

impl AsRef<UnixStream> for ReadHalf<'_> {
    fn as_ref(&self) -> &UnixStream {
        self.0
    }
}

impl AsRef<UnixStream> for WriteHalf<'_> {
    fn as_ref(&self) -> &UnixStream {
        self.0
    }
}