unbuffered_channel.hpp
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// Copyright Oliver Kowalke 2016.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
#ifndef BOOST_FIBERS_UNBUFFERED_CHANNEL_H
#define BOOST_FIBERS_UNBUFFERED_CHANNEL_H
#include <atomic>
#include <chrono>
#include <cstddef>
#include <cstdint>
#include <memory>
#include <vector>
#include <boost/config.hpp>
#include <boost/fiber/channel_op_status.hpp>
#include <boost/fiber/context.hpp>
#include <boost/fiber/detail/config.hpp>
#include <boost/fiber/detail/convert.hpp>
#if defined(BOOST_NO_CXX14_STD_EXCHANGE)
#include <boost/fiber/detail/exchange.hpp>
#endif
#include <boost/fiber/detail/spinlock.hpp>
#include <boost/fiber/exceptions.hpp>
#include <boost/fiber/waker.hpp>
#ifdef BOOST_HAS_ABI_HEADERS
# include BOOST_ABI_PREFIX
#endif
namespace boost {
namespace fibers {
template< typename T >
class unbuffered_channel {
public:
using value_type = typename std::remove_reference<T>::type;
private:
struct slot {
value_type value;
waker w;
slot( value_type const& value_, waker && w) :
value{ value_ },
w{ std::move(w) } {
}
slot( value_type && value_, waker && w) :
value{ std::move( value_) },
w{ std::move(w) } {
}
};
// shared cacheline
std::atomic< slot * > slot_{ nullptr };
// shared cacheline
std::atomic_bool closed_{ false };
mutable detail::spinlock splk_producers_{};
wait_queue waiting_producers_{};
mutable detail::spinlock splk_consumers_{};
wait_queue waiting_consumers_{};
char pad_[cacheline_length];
bool is_empty_() {
return nullptr == slot_.load( std::memory_order_acquire);
}
bool try_push_( slot * own_slot) {
for (;;) {
slot * s = slot_.load( std::memory_order_acquire);
if ( nullptr == s) {
if ( ! slot_.compare_exchange_strong( s, own_slot, std::memory_order_acq_rel) ) {
continue;
}
return true;
}
return false;
}
}
slot * try_pop_() {
slot * nil_slot = nullptr;
for (;;) {
slot * s = slot_.load( std::memory_order_acquire);
if ( nullptr != s) {
if ( ! slot_.compare_exchange_strong( s, nil_slot, std::memory_order_acq_rel) ) {
continue;}
}
return s;
}
}
public:
unbuffered_channel() = default;
~unbuffered_channel() {
close();
}
unbuffered_channel( unbuffered_channel const&) = delete;
unbuffered_channel & operator=( unbuffered_channel const&) = delete;
bool is_closed() const noexcept {
return closed_.load( std::memory_order_acquire);
}
void close() noexcept {
// set flag
if ( ! closed_.exchange( true, std::memory_order_acquire) ) {
// notify current waiting
slot * s = slot_.load( std::memory_order_acquire);
if ( nullptr != s) {
// notify context
s->w.wake();
}
detail::spinlock_lock lk1{ splk_producers_ };
waiting_producers_.notify_all();
detail::spinlock_lock lk2{ splk_consumers_ };
waiting_consumers_.notify_all();
}
}
channel_op_status push( value_type const& value) {
context * active_ctx = context::active();
slot s{ value, {} };
for (;;) {
if ( BOOST_UNLIKELY( is_closed() ) ) {
return channel_op_status::closed;
}
s.w = active_ctx->create_waker();
if ( try_push_( & s) ) {
detail::spinlock_lock lk{ splk_consumers_ };
waiting_consumers_.notify_one();
// suspend till value has been consumed
active_ctx->suspend( lk);
// resumed
if ( BOOST_UNLIKELY( is_closed() ) ) {
// channel was closed before value was consumed
return channel_op_status::closed;
}
// value has been consumed
return channel_op_status::success;
}
detail::spinlock_lock lk{ splk_producers_ };
if ( BOOST_UNLIKELY( is_closed() ) ) {
return channel_op_status::closed;
}
if ( is_empty_() ) {
continue;
}
waiting_producers_.suspend_and_wait( lk, active_ctx);
// resumed, slot mabye free
}
}
channel_op_status push( value_type && value) {
context * active_ctx = context::active();
slot s{ std::move( value), {} };
for (;;) {
if ( BOOST_UNLIKELY( is_closed() ) ) {
return channel_op_status::closed;
}
s.w = active_ctx->create_waker();
if ( try_push_( & s) ) {
detail::spinlock_lock lk{ splk_consumers_ };
waiting_consumers_.notify_one();
// suspend till value has been consumed
active_ctx->suspend( lk);
// resumed
if ( BOOST_UNLIKELY( is_closed() ) ) {
// channel was closed before value was consumed
return channel_op_status::closed;
}
// value has been consumed
return channel_op_status::success;
}
detail::spinlock_lock lk{ splk_producers_ };
if ( BOOST_UNLIKELY( is_closed() ) ) {
return channel_op_status::closed;
}
if ( is_empty_() ) {
continue;
}
waiting_producers_.suspend_and_wait( lk, active_ctx);
// resumed, slot mabye free
}
}
template< typename Rep, typename Period >
channel_op_status push_wait_for( value_type const& value,
std::chrono::duration< Rep, Period > const& timeout_duration) {
return push_wait_until( value,
std::chrono::steady_clock::now() + timeout_duration);
}
template< typename Rep, typename Period >
channel_op_status push_wait_for( value_type && value,
std::chrono::duration< Rep, Period > const& timeout_duration) {
return push_wait_until( std::forward< value_type >( value),
std::chrono::steady_clock::now() + timeout_duration);
}
template< typename Clock, typename Duration >
channel_op_status push_wait_until( value_type const& value,
std::chrono::time_point< Clock, Duration > const& timeout_time_) {
context * active_ctx = context::active();
slot s{ value, {} };
std::chrono::steady_clock::time_point timeout_time = detail::convert( timeout_time_);
for (;;) {
if ( BOOST_UNLIKELY( is_closed() ) ) {
return channel_op_status::closed;
}
s.w = active_ctx->create_waker();
if ( try_push_( & s) ) {
detail::spinlock_lock lk{ splk_consumers_ };
waiting_consumers_.notify_one();
// suspend this producer
if ( ! active_ctx->wait_until(timeout_time, lk, waker(s.w))) {
// clear slot
slot * nil_slot = nullptr, * own_slot = & s;
slot_.compare_exchange_strong( own_slot, nil_slot, std::memory_order_acq_rel);
// resumed, value has not been consumed
return channel_op_status::timeout;
}
// resumed
if ( BOOST_UNLIKELY( is_closed() ) ) {
// channel was closed before value was consumed
return channel_op_status::closed;
}
// value has been consumed
return channel_op_status::success;
}
detail::spinlock_lock lk{ splk_producers_ };
if ( BOOST_UNLIKELY( is_closed() ) ) {
return channel_op_status::closed;
}
if ( is_empty_() ) {
continue;
}
if (! waiting_producers_.suspend_and_wait_until( lk, active_ctx, timeout_time))
{
return channel_op_status::timeout;
}
// resumed, slot maybe free
}
}
template< typename Clock, typename Duration >
channel_op_status push_wait_until( value_type && value,
std::chrono::time_point< Clock, Duration > const& timeout_time_) {
context * active_ctx = context::active();
slot s{ std::move( value), {} };
std::chrono::steady_clock::time_point timeout_time = detail::convert( timeout_time_);
for (;;) {
if ( BOOST_UNLIKELY( is_closed() ) ) {
return channel_op_status::closed;
}
s.w = active_ctx->create_waker();
if ( try_push_( & s) ) {
detail::spinlock_lock lk{ splk_consumers_ };
waiting_consumers_.notify_one();
// suspend this producer
if ( ! active_ctx->wait_until(timeout_time, lk, waker(s.w))) {
// clear slot
slot * nil_slot = nullptr, * own_slot = & s;
slot_.compare_exchange_strong( own_slot, nil_slot, std::memory_order_acq_rel);
// resumed, value has not been consumed
return channel_op_status::timeout;
}
// resumed
if ( BOOST_UNLIKELY( is_closed() ) ) {
// channel was closed before value was consumed
return channel_op_status::closed;
}
// value has been consumed
return channel_op_status::success;
}
detail::spinlock_lock lk{ splk_producers_ };
if ( BOOST_UNLIKELY( is_closed() ) ) {
return channel_op_status::closed;
}
if ( is_empty_() ) {
continue;
}
if (! waiting_producers_.suspend_and_wait_until( lk, active_ctx, timeout_time))
{
return channel_op_status::timeout;
}
// resumed, slot maybe free
}
}
channel_op_status pop( value_type & value) {
context * active_ctx = context::active();
slot * s = nullptr;
for (;;) {
if ( nullptr != ( s = try_pop_() ) ) {
{
detail::spinlock_lock lk{ splk_producers_ };
waiting_producers_.notify_one();
}
value = std::move( s->value);
// notify context
s->w.wake();
return channel_op_status::success;
}
detail::spinlock_lock lk{ splk_consumers_ };
if ( BOOST_UNLIKELY( is_closed() ) ) {
return channel_op_status::closed;
}
if ( ! is_empty_() ) {
continue;
}
waiting_consumers_.suspend_and_wait( lk, active_ctx);
// resumed, slot mabye set
}
}
value_type value_pop() {
context * active_ctx = context::active();
slot * s = nullptr;
for (;;) {
if ( nullptr != ( s = try_pop_() ) ) {
{
detail::spinlock_lock lk{ splk_producers_ };
waiting_producers_.notify_one();
}
// consume value
value_type value = std::move( s->value);
// notify context
s->w.wake();
return std::move( value);
}
detail::spinlock_lock lk{ splk_consumers_ };
if ( BOOST_UNLIKELY( is_closed() ) ) {
throw fiber_error{
std::make_error_code( std::errc::operation_not_permitted),
"boost fiber: channel is closed" };
}
if ( ! is_empty_() ) {
continue;
}
waiting_consumers_.suspend_and_wait( lk, active_ctx);
// resumed, slot mabye set
}
}
template< typename Rep, typename Period >
channel_op_status pop_wait_for( value_type & value,
std::chrono::duration< Rep, Period > const& timeout_duration) {
return pop_wait_until( value,
std::chrono::steady_clock::now() + timeout_duration);
}
template< typename Clock, typename Duration >
channel_op_status pop_wait_until( value_type & value,
std::chrono::time_point< Clock, Duration > const& timeout_time_) {
context * active_ctx = context::active();
slot * s = nullptr;
std::chrono::steady_clock::time_point timeout_time = detail::convert( timeout_time_);
for (;;) {
if ( nullptr != ( s = try_pop_() ) ) {
{
detail::spinlock_lock lk{ splk_producers_ };
waiting_producers_.notify_one();
}
// consume value
value = std::move( s->value);
// notify context
s->w.wake();
return channel_op_status::success;
}
detail::spinlock_lock lk{ splk_consumers_ };
if ( BOOST_UNLIKELY( is_closed() ) ) {
return channel_op_status::closed;
}
if ( ! is_empty_() ) {
continue;
}
if ( ! waiting_consumers_.suspend_and_wait_until( lk, active_ctx, timeout_time)) {
return channel_op_status::timeout;
}
}
}
class iterator {
private:
typedef typename std::aligned_storage< sizeof( value_type), alignof( value_type) >::type storage_type;
unbuffered_channel * chan_{ nullptr };
storage_type storage_;
void increment_( bool initial = false) {
BOOST_ASSERT( nullptr != chan_);
try {
if ( ! initial) {
reinterpret_cast< value_type * >( std::addressof( storage_) )->~value_type();
}
::new ( static_cast< void * >( std::addressof( storage_) ) ) value_type{ chan_->value_pop() };
} catch ( fiber_error const&) {
chan_ = nullptr;
}
}
public:
using iterator_category = std::input_iterator_tag;
using difference_type = std::ptrdiff_t;
using pointer = value_type *;
using reference = value_type &;
using pointer_t = pointer;
using reference_t = reference;
iterator() = default;
explicit iterator( unbuffered_channel< T > * chan) noexcept :
chan_{ chan } {
increment_( true);
}
iterator( iterator const& other) noexcept :
chan_{ other.chan_ } {
}
iterator & operator=( iterator const& other) noexcept {
if ( this == & other) return * this;
chan_ = other.chan_;
return * this;
}
bool operator==( iterator const& other) const noexcept {
return other.chan_ == chan_;
}
bool operator!=( iterator const& other) const noexcept {
return other.chan_ != chan_;
}
iterator & operator++() {
reinterpret_cast< value_type * >( std::addressof( storage_) )->~value_type();
increment_();
return * this;
}
const iterator operator++( int) = delete;
reference_t operator*() noexcept {
return * reinterpret_cast< value_type * >( std::addressof( storage_) );
}
pointer_t operator->() noexcept {
return reinterpret_cast< value_type * >( std::addressof( storage_) );
}
};
friend class iterator;
};
template< typename T >
typename unbuffered_channel< T >::iterator
begin( unbuffered_channel< T > & chan) {
return typename unbuffered_channel< T >::iterator( & chan);
}
template< typename T >
typename unbuffered_channel< T >::iterator
end( unbuffered_channel< T > &) {
return typename unbuffered_channel< T >::iterator();
}
}}
#ifdef BOOST_HAS_ABI_HEADERS
# include BOOST_ABI_SUFFIX
#endif
#endif // BOOST_FIBERS_UNBUFFERED_CHANNEL_H