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use crate::ctx::*;
use crate::ptr::*;
use std::collections::LinkedList;
struct ChannelInner<T> {
capacity: usize,
slots: Vec<Option<T>>,
waiting_producers: LinkedList<Ptr<Context>>,
waiting_consumers: LinkedList<Ptr<Context>>,
closed: bool,
cidx: usize,
pidx: usize,
}
impl<T> ChannelInner<T> {
fn is_full_(&self) -> bool {
self.cidx == ((self.pidx + 1) % self.capacity)
}
fn is_empty_(&self) -> bool {
self.cidx == self.pidx
}
pub fn is_closed(&self) -> bool {
self.closed
}
pub fn close(&mut self) {
//let active_ctx = Context::active();
if !self.closed {
self.closed = true;
while let Some(producer_ctx) = self.waiting_producers.pop_front() {
let expected = self as *const ChannelInner<T>;
let result = producer_ctx.get().twstatus.compare_exchange(
expected as *mut _,
-1i8 as *mut i8,
std::sync::atomic::Ordering::Acquire,
std::sync::atomic::Ordering::Relaxed,
);
match result {
Ok(_) => {
crate::yield_thread();
break;
}
Err(x) => {
if x.is_null() {
crate::yield_thread();
break;
}
}
}
}
while let Some(consumer_ctx) = self.waiting_consumers.pop_front() {
let expected = self as *const ChannelInner<T>;
let result = consumer_ctx.get().twstatus.compare_exchange(
expected as *mut _,
-1i8 as *mut i8,
std::sync::atomic::Ordering::Acquire,
std::sync::atomic::Ordering::Relaxed,
);
match result {
Ok(_) => {
crate::yield_thread();
break;
}
Err(x) => {
if x.is_null() {
crate::yield_thread();
break;
}
}
}
}
}
}
pub fn push(&mut self, value: T) -> ChannelStatus {
let active_ctx = Context::active();
loop {
if self.is_closed() {
return ChannelStatus::Closed;
} else if self.is_full_() {
// Full? Suspend until receiver will receive value from current channel.
self.waiting_producers.push_back(active_ctx);
active_ctx
.twstatus
.store(0 as *mut _, std::sync::atomic::Ordering::Release);
active_ctx.scheduler.get().suspend_thread(active_ctx);
} else {
self.slots[self.pidx] = Some(value);
self.pidx = (self.pidx + 1) % self.capacity;
while let Some(consumer_ctx) = self.waiting_consumers.pop_front() {
let expected = self as *const ChannelInner<T>;
let result = consumer_ctx.get().twstatus.compare_exchange(
expected as *mut _,
-1i8 as *mut i8,
std::sync::atomic::Ordering::Acquire,
std::sync::atomic::Ordering::Relaxed,
);
match result {
Ok(_) => {
crate::yield_thread();
break;
}
Err(x) => {
if x.is_null() {
crate::yield_thread();
break;
}
}
}
}
return ChannelStatus::Success;
}
}
}
pub fn try_push(&mut self, value: T) -> ChannelStatus {
loop {
if self.is_closed() {
return ChannelStatus::Closed;
} else if self.is_full_() {
return ChannelStatus::Full;
} else {
self.slots[self.pidx] = Some(value);
self.pidx = (self.pidx + 1) % self.capacity;
while let Some(consumer_ctx) = self.waiting_consumers.pop_front() {
let expected = self as *const ChannelInner<T>;
let result = consumer_ctx.get().twstatus.compare_exchange(
expected as *mut _,
-1i8 as *mut i8,
std::sync::atomic::Ordering::Acquire,
std::sync::atomic::Ordering::Relaxed,
);
match result {
Ok(_) => {
crate::yield_thread();
break;
}
Err(x) => {
if x.is_null() {
crate::yield_thread();
break;
}
}
}
}
return ChannelStatus::Success;
}
}
}
pub fn pop(&mut self) -> Result<T, ChannelStatus> {
let active_ctx = Context::active();
loop {
if self.is_empty_() {
if self.is_closed() {
return Err(ChannelStatus::Closed);
} else {
// Empty? Suspend until sender will send value.
self.waiting_consumers.push_back(active_ctx);
active_ctx
.twstatus
.store(0 as *mut _, std::sync::atomic::Ordering::Release);
active_ctx.scheduler.get().suspend_thread(active_ctx);
}
} else {
let mut value = None;
std::mem::swap(&mut self.slots[self.cidx], &mut value);
self.cidx = (self.cidx + 1) % self.capacity;
while let Some(producer_ctx) = self.waiting_producers.pop_front() {
let expected = self as *const ChannelInner<T>;
let result = producer_ctx.get().twstatus.compare_exchange(
expected as *mut _,
-1i8 as *mut i8,
std::sync::atomic::Ordering::Acquire,
std::sync::atomic::Ordering::Relaxed,
);
match result {
Ok(_) => {
crate::yield_thread();
break;
}
_ => {
crate::yield_thread();
break;
}
}
}
return Ok(value.unwrap());
}
}
}
pub fn try_pop(&mut self) -> Result<T, ChannelStatus> {
loop {
if self.is_empty_() {
if self.is_closed() {
return Err(ChannelStatus::Closed);
} else {
return Err(ChannelStatus::Empty);
}
} else {
let mut value = None;
std::mem::swap(&mut self.slots[self.cidx], &mut value);
self.cidx = (self.cidx + 1) % self.capacity;
while let Some(producer_ctx) = self.waiting_producers.pop_front() {
let expected = self as *const ChannelInner<T>;
let result = producer_ctx.get().twstatus.compare_exchange(
expected as *mut _,
-1i8 as *mut i8,
std::sync::atomic::Ordering::Acquire,
std::sync::atomic::Ordering::Relaxed,
);
match result {
Ok(_) => {
crate::yield_thread();
break;
}
_ => {
crate::yield_thread();
break;
}
}
}
return Ok(value.unwrap());
}
}
}
}
#[derive(Copy, Clone, Debug, PartialEq)]
pub enum ChannelStatus {
Success,
Empty,
Full,
Closed,
Timeout,
}
/// A channel is a communication object using which fibers can communicate with each other.
/// Technically, a channel is a data transfer pipe where data can be passed into or read from.
/// Hence one fiber can send data into a channel, while other fibers can read that data
/// from the same channel.
pub struct Channel<T> {
inner: Ptr<ChannelInner<T>>,
}
use std::rc::Rc;
impl<T> Channel<T> {
pub fn new(size: usize) -> Rc<Self> {
Rc::new(Self {
inner: Ptr::new(ChannelInner {
capacity: size,
slots: {
let mut v = Vec::with_capacity(size);
for _ in 0..size {
v.push(None);
}
v
},
waiting_producers: LinkedList::new(),
waiting_consumers: LinkedList::new(),
closed: false,
cidx: 0,
pidx: 0,
}),
})
}
/// Blocks the current thread until a message is send or the channel is closed.
///
/// If the channel if sull and not closed, this call will block until send operation can proceed. If the channel becomes
/// closed, this call will wake up and return `ChannelStatus::Closed`.
pub fn send(&self, value: T) -> ChannelStatus {
self.inner.get().push(value)
}
/// Blocks the current thread until a mesasge is received or the channel is empty and closed.
///
/// If the channel is empty and not closed, this call will block until the receive can proceed. If the channel is empty and becomes
/// closed, this call will wake up and return an `Err(ChannelStatus::Closed)`
pub fn recv(&self) -> Result<T, ChannelStatus> {
self.inner.get().pop()
}
/// Attempts to send a message into the channel without blocking.
///
/// This method will either send a message into the channel immediately or return an error if the channel is full or disconnected. The
/// returned error contains the original message.
pub fn try_send(&self, value: T) -> ChannelStatus {
self.inner.get().try_push(value)
}
/// Attempts to receive a message from the channel without blocking.
///
/// This method will either receive a message from the channel immediately or return an error if the channel is empty.
pub fn try_recv(&self) -> Result<T, ChannelStatus> {
self.inner.get().try_pop()
}
pub fn is_closed(&self) -> bool {
self.inner.closed
}
pub fn close(&self) {
self.inner.get().close()
}
}
impl<T> Drop for ChannelInner<T> {
fn drop(&mut self) {
self.slots.clear();
self.close();
}
}
impl<T> Drop for Channel<T> {
fn drop(&mut self) {
let _ = unsafe { Box::from_raw(self.inner.0) };
}
}