logo
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
//! Potentially infinite async [`Stream`] response types.
//!
//! A [`Stream<Item = T>`] is the async analog of an `Iterator<Item = T>`: it
//! generates a sequence of values asynchronously, otherwise known as an async
//! _generator_. Types in this module allow for returning responses that are
//! streams.
//!
//! [`Stream<Item = T>`]: https://docs.rs/futures/0.3/futures/stream/trait.Stream.html
//! [`Stream`]: https://docs.rs/futures/0.3/futures/stream/trait.Stream.html
//!
//! # Raw Streams
//!
//! Rust does not yet natively support syntax for creating arbitrary generators,
//! and as such, for creating streams. To ameliorate this, Rocket exports
//! [`stream!`], which retrofit generator syntax, allowing raw `impl Stream`s to
//! be defined using `yield` and `for await` syntax:
//!
//! ```rust
//! use rocket::futures::stream::Stream;
//! use rocket::response::stream::stream;
//!
//! fn make_stream() -> impl Stream<Item = u8> {
//!     stream! {
//!         for i in 0..3 {
//!             yield i;
//!         }
//!     }
//! }
//! ```
//!
//! See [`stream!`] for full usage details.
//!
//! # Typed Streams
//!
//! A raw stream is not a `Responder`, so it cannot be directly returned from a
//! route handler. Instead, one of three _typed_ streams may be used. Each typed
//! stream places type bounds on the `Item` of the stream, allowing for
//! `Responder` implementation on the stream itself.
//!
//! Each typed stream exists both as a type and as a macro. They are:
//!
//!   * [`struct@ReaderStream`] ([`ReaderStream!`]) - streams of `T: AsyncRead`
//!   * [`struct@ByteStream`] ([`ByteStream!`]) - streams of `T: AsRef<[u8]>`
//!   * [`struct@TextStream`] ([`TextStream!`]) - streams of `T: AsRef<str>`
//!   * [`struct@EventStream`] ([`EventStream!`]) - Server-Sent [`Event`] stream
//!
//! Each type implements `Responder`; each macro can be invoked to generate a
//! typed stream, exactly like [`stream!`] above. Additionally, each macro is
//! also a _type_ macro, expanding to a wrapped `impl Stream<Item = $T>`, where
//! `$T` is the input to the macro.
//!
//! As a concrete example, the route below produces an infinite series of
//! `"hello"`s, one per second:
//!
//! ```rust
//! # use rocket::get;
//! use rocket::tokio::time::{self, Duration};
//! use rocket::response::stream::TextStream;
//!
//! /// Produce an infinite series of `"hello"`s, one per second.
//! #[get("/infinite-hellos")]
//! fn hello() -> TextStream![&'static str] {
//!     TextStream! {
//!         let mut interval = time::interval(Duration::from_secs(1));
//!         loop {
//!             yield "hello";
//!             interval.tick().await;
//!         }
//!     }
//! }
//! ```
//!
//! The `TextStream![&'static str]` invocation expands to:
//!
//! ```rust
//! # use rocket::response::stream::TextStream;
//! # use rocket::futures::stream::Stream;
//! # use rocket::response::stream::stream;
//! # fn f() ->
//! TextStream<impl Stream<Item = &'static str>>
//! # { TextStream::from(stream! { yield "hi" }) }
//! ```
//!
//! While the inner `TextStream! { .. }` invocation expands to:
//!
//! ```rust
//! # use rocket::response::stream::{TextStream, stream};
//! TextStream::from(stream! { /* .. */ })
//! # ;
//! ```
//!
//! The expansions are identical for `ReaderStream` and `ByteStream`, with
//! `TextStream` replaced with `ReaderStream` and `ByteStream`, respectively.
//!
//! ## Borrowing
//!
//! A stream can _yield_ borrowed values with no extra effort:
//!
//! ```rust
//! # use rocket::get;
//! use rocket::State;
//! use rocket::response::stream::TextStream;
//!
//! /// Produce a single string borrowed from the request.
//! #[get("/infinite-hellos")]
//! fn hello(string: &State<String>) -> TextStream![&str] {
//!     TextStream! {
//!         yield string.as_str();
//!     }
//! }
//! ```
//!
//! If the stream _contains_ a borrowed value or uses one internally, Rust
//! requires this fact be explicit with a lifetime annotation:
//!
//! ```rust
//! # use rocket::get;
//! use rocket::State;
//! use rocket::response::stream::TextStream;
//!
//! #[get("/")]
//! fn borrow1(ctxt: &State<bool>) -> TextStream![&'static str + '_] {
//!     TextStream! {
//!         // By using `ctxt` in the stream, the borrow is moved into it. Thus,
//!         // the stream object contains a borrow, prompting the '_ annotation.
//!         if *ctxt.inner() {
//!             yield "hello";
//!         }
//!     }
//! }
//!
//! // Just as before but yielding an owned yield value.
//! #[get("/")]
//! fn borrow2(ctxt: &State<bool>) -> TextStream![String + '_] {
//!     TextStream! {
//!         if *ctxt.inner() {
//!             yield "hello".to_string();
//!         }
//!     }
//! }
//!
//! // As before but _also_ return a borrowed value. Without it, Rust gives:
//! // - lifetime `'r` is missing in item created through this procedural macro
//! #[get("/")]
//! fn borrow3<'r>(ctxt: &'r State<bool>, s: &'r State<String>) -> TextStream![&'r str + 'r] {
//!     TextStream! {
//!         if *ctxt.inner() {
//!             yield s.as_str();
//!         }
//!     }
//! }
//! ```
//!
//! # Graceful Shutdown
//!
//! Infinite responders, like the one defined in `hello` above, will prolong
//! shutdown initiated via [`Shutdown::notify()`](crate::Shutdown::notify()) for
//! the defined grace period. After the grace period has elapsed, Rocket will
//! abruptly terminate the responder.
//!
//! To avoid abrupt termination, graceful shutdown can be detected via the
//! [`Shutdown`](crate::Shutdown) future, allowing the infinite responder to
//! gracefully shut itself down. The following example modifies the previous
//! `hello` with shutdown detection:
//!
//! ```rust
//! # use rocket::get;
//! use rocket::Shutdown;
//! use rocket::response::stream::TextStream;
//! use rocket::tokio::select;
//! use rocket::tokio::time::{self, Duration};
//!
//! /// Produce an infinite series of `"hello"`s, 1/second, until shutdown.
//! #[get("/infinite-hellos")]
//! fn hello(mut shutdown: Shutdown) -> TextStream![&'static str] {
//!     TextStream! {
//!         let mut interval = time::interval(Duration::from_secs(1));
//!         loop {
//!             select! {
//!                 _ = interval.tick() => yield "hello",
//!                 _ = &mut shutdown => {
//!                     yield "goodbye";
//!                     break;
//!                 }
//!             };
//!         }
//!     }
//! }
//! ```

mod reader;
mod bytes;
mod text;
mod one;
mod sse;
mod raw_sse;

pub(crate) use self::raw_sse::*;

pub use self::one::One;
pub use self::text::TextStream;
pub use self::bytes::ByteStream;
pub use self::reader::ReaderStream;
pub use self::sse::{Event, EventStream};

crate::export! {
    /// Retrofitted support for [`Stream`]s with `yield`, `for await` syntax.
    ///
    /// [`Stream`]: https://docs.rs/futures/0.3/futures/stream/trait.Stream.html
    ///
    /// This macro takes any series of statements and expands them into an
    /// expression of type `impl Stream<Item = T>`, a stream that `yield`s
    /// elements of type `T`. It supports any Rust statement syntax with the
    /// following extensions:
    ///
    ///   * `yield expr`
    ///
    ///      Yields the result of evaluating `expr` to the caller (the stream
    ///      consumer). `expr` must be of type `T`.
    ///
    ///   * `for await x in stream { .. }`
    ///
    ///      `await`s the next element in `stream`, binds it to `x`, and
    ///      executes the block with the binding. `stream` must implement
    ///      `Stream<Item = T>`; the type of `x` is `T`.
    ///
    ///   * `?` short-cicuits stream termination on `Err`
    ///
    /// # Examples
    ///
    /// ```rust
    /// use rocket::response::stream::stream;
    /// use rocket::futures::stream::Stream;
    ///
    /// fn f(stream: impl Stream<Item = u8>) -> impl Stream<Item = String> {
    ///     stream! {
    ///         for s in &["hi", "there"]{
    ///             yield s.to_string();
    ///         }
    ///
    ///         for await n in stream {
    ///             yield format!("n: {}", n);
    ///         }
    ///     }
    /// }
    ///
    /// # rocket::async_test(async {
    /// use rocket::futures::stream::{self, StreamExt};
    ///
    /// let stream = f(stream::iter(vec![3, 7, 11]));
    /// let strings: Vec<_> = stream.collect().await;
    /// assert_eq!(strings, ["hi", "there", "n: 3", "n: 7", "n: 11"]);
    /// # });
    /// ```
    ///
    /// Using `?` on an `Err` short-cicuits stream termination:
    ///
    /// ```rust
    /// use std::io;
    ///
    /// use rocket::response::stream::stream;
    /// use rocket::futures::stream::Stream;
    ///
    /// fn g<S>(stream: S) -> impl Stream<Item = io::Result<u8>>
    ///     where S: Stream<Item = io::Result<&'static str>>
    /// {
    ///     stream! {
    ///         for await s in stream {
    ///             let num = s?.parse();
    ///             let num = num.map_err(|e| io::Error::new(io::ErrorKind::Other, e))?;
    ///             yield Ok(num);
    ///         }
    ///     }
    /// }
    ///
    /// # rocket::async_test(async {
    /// use rocket::futures::stream::{self, StreamExt};
    ///
    /// let e = io::Error::last_os_error();
    /// let stream = g(stream::iter(vec![Ok("3"), Ok("four"), Err(e), Ok("2")]));
    /// let results: Vec<_> = stream.collect().await;
    /// assert!(matches!(results.as_slice(), &[Ok(3), Err(_)]));
    /// # });
    /// ```
    macro_rules! stream {
        ($($t:tt)*) => ($crate::async_stream::stream!($($t)*));
    }
}

#[doc(hidden)]
#[macro_export]
macro_rules! _typed_stream {
    ($S:ident, $($t:tt)*) => (
        $crate::__typed_stream! {
            $crate::response::stream::$S,
            $crate::response::stream::stream,
            $crate::futures::stream::Stream,
            $($t)*
        }
    )
}