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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,103 @@ | ||
| //! This module contains types for I/O functionality. | ||
| // This module should remain private until impl trait type alias becomes available so | ||
| // `BufReader` can be produced with an existential type. | ||
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| use std::borrow::Cow; | ||
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| use futures::stream::Stream; | ||
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| use crate::platform::sync::mpsc::{self, UnboundedReceiverStream, UnboundedSender}; | ||
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| // Same as std::io::BufWriter and futures::io::BufWriter. | ||
| pub(crate) const DEFAULT_BUF_SIZE: usize = 8 * 1024; | ||
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| /// A [`futures::io::BufWriter`], but operates over string and yields into a Stream. | ||
| pub(crate) struct BufWriter { | ||
| buf: String, | ||
| tx: UnboundedSender<String>, | ||
| capacity: usize, | ||
| } | ||
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| /// Creates a Buffer pair. | ||
| pub(crate) fn buffer(capacity: usize) -> (BufWriter, impl Stream<Item = String>) { | ||
| let (tx, rx) = mpsc::unbounded_channel::<String>(); | ||
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| let tx = BufWriter { | ||
| buf: String::with_capacity(capacity), | ||
| tx, | ||
| capacity, | ||
| }; | ||
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| (tx, UnboundedReceiverStream::new(rx)) | ||
| } | ||
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| // Implementation Notes: | ||
| // | ||
| // When jemalloc is used and a reasonable buffer length is chosen, | ||
| // performance of this buffer is related to the number of allocations | ||
| // instead of the amount of memory that is allocated. | ||
| // | ||
| // A Bytes-based implementation is also tested, and yielded a similar performance to String-based | ||
| // buffer. | ||
| // | ||
| // Having a String-based buffer avoids unsafe / cost of conversion between String and Bytes | ||
| // when text based content is needed (e.g.: post-processing). | ||
| // | ||
| // `Bytes::from` can be used to convert a `String` to `Bytes` if web server asks for an | ||
| // `impl Stream<Item = Bytes>`. This conversion incurs no memory allocation. | ||
| // | ||
| // Yielding the output with a Stream provides a couple advantages: | ||
| // | ||
| // 1. All child components of a VList can have their own buffer and be rendered concurrently. | ||
| // 2. If a fixed buffer is used, the rendering process can become blocked if the buffer is filled. | ||
| // Using a stream avoids this side effect and allows the renderer to finish rendering | ||
| // without being actively polled. | ||
| impl BufWriter { | ||
| #[inline] | ||
| pub fn capacity(&self) -> usize { | ||
| self.capacity | ||
| } | ||
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| fn drain(&mut self) { | ||
| let _ = self.tx.send(self.buf.drain(..).collect()); | ||
| self.buf.reserve(self.capacity); | ||
| } | ||
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| /// Returns `True` if the internal buffer has capacity to fit a string of certain length. | ||
| #[inline] | ||
| fn has_capacity_of(&self, next_part_len: usize) -> bool { | ||
| self.buf.capacity() >= self.buf.len() + next_part_len | ||
| } | ||
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| /// Writes a string into the buffer, optionally drains the buffer. | ||
| pub fn write(&mut self, s: Cow<'_, str>) { | ||
| if !self.has_capacity_of(s.len()) { | ||
| // There isn't enough capacity, we drain the buffer. | ||
| self.drain(); | ||
| } | ||
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| if self.has_capacity_of(s.len()) { | ||
| // The next part is going to fit into the buffer, we push it onto the buffer. | ||
| self.buf.push_str(&s); | ||
| } else { | ||
| // if the next part is more than buffer size, we send the next part. | ||
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| // We don't need to drain the buffer here as the result of self.has_capacity_of() only | ||
| // changes if the buffer was drained. If the buffer capacity didn't change, | ||
| // then it means self.has_capacity_of() has returned true the first time which will be | ||
| // guaranteed to be matched by the left hand side of this implementation. | ||
| let _ = self.tx.send(s.into_owned()); | ||
| } | ||
| } | ||
| } | ||
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| impl Drop for BufWriter { | ||
| fn drop(&mut self) { | ||
| if !self.buf.is_empty() { | ||
| let mut buf = String::new(); | ||
| std::mem::swap(&mut buf, &mut self.buf); | ||
| let _ = self.tx.send(buf); | ||
| } | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,5 @@ | ||
| //! A module that provides task synchronisation primitives. | ||
| #[doc(inline)] | ||
| pub use tokio::sync::oneshot; | ||
| pub mod mpsc; |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,6 @@ | ||
| //! A multi-producer, single-receiver channel. | ||
| #[doc(inline)] | ||
| pub use tokio::sync::mpsc::*; | ||
| #[doc(inline)] | ||
| pub use tokio_stream::wrappers::{ReceiverStream, UnboundedReceiverStream}; |
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