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

use std::fmt;
use std::hash::{Hash, Hasher};
use std::ops::Deref;
use std::pin::Pin;
use std::task::{Context, Poll};

use futures::io::{self, AsyncRead, AsyncWrite};

/// A reference-counted pointer that implements async I/O traits.
///
/// This is just a wrapper around [`std::sync::Arc`] that adds the following impls:
///
/// - `impl<T> AsyncRead for Arc<T> where &T: AsyncRead {}`
/// - `impl<T> AsyncWrite for Arc<T> where &T: AsyncWrite {}`
///
/// # Examples
///
/// ```no_run
/// use futures::io;
/// use piper::Arc;
/// use smol::Async;
/// use std::net::TcpStream;
///
/// # fn main() -> std::io::Result<()> { smol::run(async {
/// // A client that echoes messages back to the server.
/// let stream = Async::<TcpStream>::connect("127.0.0.1:8000").await?;
///
/// // Create two handles to the stream.
/// let reader = Arc::new(stream);
/// let mut writer = reader.clone();
///
/// // Echo data received from the reader back into the writer.
/// io::copy(reader, &mut writer).await?;
/// # Ok(()) }) }
/// ```
pub struct Arc<T>(std::sync::Arc<T>);

impl<T> Unpin for Arc<T> {}

impl<T> Arc<T> {
    /// Constructs a new `Arc<T>`.
    ///
    /// # Examples
    ///
    /// ```
    /// use piper::Arc;
    /// use std::sync;
    ///
    /// // These two lines are equivalent:
    /// let a = Arc::new(7);
    /// let a = Arc(sync::Arc::new(7));
    /// ```
    pub fn new(data: T) -> Arc<T> {
        Arc(std::sync::Arc::new(data))
    }
}

impl<T> Clone for Arc<T> {
    fn clone(&self) -> Arc<T> {
        Arc(self.0.clone())
    }
}

impl<T> Deref for Arc<T> {
    type Target = T;

    #[inline]
    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl<T: fmt::Debug> fmt::Debug for Arc<T> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Debug::fmt(&**self, f)
    }
}

impl<T: fmt::Display> fmt::Display for Arc<T> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Display::fmt(&**self, f)
    }
}

impl<T: Hash> Hash for Arc<T> {
    fn hash<H: Hasher>(&self, state: &mut H) {
        (**self).hash(state)
    }
}

impl<T> fmt::Pointer for Arc<T> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Pointer::fmt(&(&**self as *const T), f)
    }
}

impl<T: Default> Default for Arc<T> {
    fn default() -> Arc<T> {
        Arc::new(Default::default())
    }
}

impl<T> From<T> for Arc<T> {
    fn from(t: T) -> Arc<T> {
        Arc::new(t)
    }
}

// NOTE(stjepang): It would also make sense to have the following impls:
//
// - `impl<T> AsyncRead for &Arc<T> where &T: AsyncRead {}`
// - `impl<T> AsyncWrite for &Arc<T> where &T: AsyncWrite {}`
//
// However, those impls sometimes make Rust's type inference try too hard when types cannot be
// inferred. In the end, instead of complaining with a nice error message, the Rust compiler ends
// up overflowing and dumping a very long error message spanning multiple screens.
//
// Since those impls are not essential, I decided to err on the safe side and not include them.

impl<T> AsyncRead for Arc<T>
where
    for<'a> &'a T: AsyncRead,
{
    fn poll_read(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        buf: &mut [u8],
    ) -> Poll<io::Result<usize>> {
        Pin::new(&mut &*self.0).poll_read(cx, buf)
    }
}

impl<T> AsyncWrite for Arc<T>
where
    for<'a> &'a T: AsyncWrite,
{
    fn poll_write(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        buf: &[u8],
    ) -> Poll<io::Result<usize>> {
        Pin::new(&mut &*self.0).poll_write(cx, buf)
    }

    fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
        Pin::new(&mut &*self.0).poll_flush(cx)
    }

    fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
        Pin::new(&mut &*self.0).poll_close(cx)
    }
}