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Diffstat (limited to 'Transceiver52M/itrq.h')
| -rw-r--r-- | Transceiver52M/itrq.h | 204 |
1 files changed, 204 insertions, 0 deletions
diff --git a/Transceiver52M/itrq.h b/Transceiver52M/itrq.h new file mode 100644 index 0000000..f086af3 --- /dev/null +++ b/Transceiver52M/itrq.h @@ -0,0 +1,204 @@ +#pragma once +/* + * (C) 2022 by sysmocom s.f.m.c. GmbH <info@sysmocom.de> + * All Rights Reserved + * + * Author: Eric Wild <ewild@sysmocom.de> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU Affero General Public License as published by + * the Free Software Foundation; either version 3 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU Affero General Public License for more details. + * + * You should have received a copy of the GNU Affero General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + * + */ + +#include <atomic> + +#include <condition_variable> +#include <mutex> +#include <sys/eventfd.h> +#include <unistd.h> + +#include <stdatomic.h> +#include <stdbool.h> +#include <stdlib.h> + +/* +classic lamport circular lockfree spsc queue: +every "side" only writes its own ptr, but may read the other sides ptr + +notify reader using eventfd as soon as element is added, reader then reads until +read fails +-> reader pops in a loop until FALSE and might get spurious events because it +read before it was notified, which is fine +-> writing pushes *the same data* in a loop until TRUE, blocks + +shutting this down requires +1) to stop reading and pushing +2) ONE side to take care of the eventfds +*/ + +namespace spsc_detail +{ +template <bool block_read, bool block_write> class spsc_cond_detail { + std::condition_variable cond_r, cond_w; + std::mutex l; + + public: + explicit spsc_cond_detail() + { + } + + ~spsc_cond_detail() + { + } + + ssize_t spsc_check_r() + { + std::unique_lock<std::mutex> lk(l); + cond_r.wait(lk); + return 1; + } + ssize_t spsc_check_w() + { + std::unique_lock<std::mutex> lk(l); + cond_w.wait(lk); + return 1; + } + void spsc_notify_r() + { + cond_r.notify_one(); + } + void spsc_notify_w() + { + cond_w.notify_one(); + } +}; + +// originally designed for select loop integration +template <bool block_read, bool block_write> class spsc_efd_detail { + int efd_r, efd_w; /* eventfds used to block/notify readers/writers */ + + public: + explicit spsc_efd_detail() + : efd_r(eventfd(0, block_read ? 0 : EFD_NONBLOCK)), efd_w(eventfd(1, block_write ? 0 : EFD_NONBLOCK)) + { + } + + ~spsc_efd_detail() + { + close(efd_r); + close(efd_w); + } + + ssize_t spsc_check_r() + { + uint64_t efdr; + return read(efd_r, &efdr, sizeof(uint64_t)); + } + ssize_t spsc_check_w() + { + uint64_t efdr; + return read(efd_w, &efdr, sizeof(uint64_t)); + } + void spsc_notify_r() + { + uint64_t efdu = 1; + write(efd_r, &efdu, sizeof(uint64_t)); + } + void spsc_notify_w() + { + uint64_t efdu = 1; + write(efd_w, &efdu, sizeof(uint64_t)); + } + int get_r_efd() + { + return efd_r; + } + int get_w_efd() + { + return efd_w; + } +}; + +template <unsigned int SZ, typename ELEM, bool block_read, bool block_write, template <bool, bool> class T> +class spsc : public T<block_read, block_write> { + static_assert(SZ > 0, "queues need a size..."); + std::atomic<unsigned int> readptr; + std::atomic<unsigned int> writeptr; + + ELEM buf[SZ]; + + public: + using base_t = T<block_read, block_write>; + using elem_t = ELEM; + explicit spsc() : readptr(0), writeptr(0) + { + } + + ~spsc() + { + } + + /*! Adds element to the queue by copying the data. + * \param[in] elem input buffer, must match the originally configured queue buffer size!. + * \returns true if queue was not full and element was successfully pushed */ + bool spsc_push(ELEM *elem) + { + size_t cur_wp, cur_rp; + cur_wp = writeptr.load(std::memory_order_relaxed); + cur_rp = readptr.load(std::memory_order_acquire); + if ((cur_wp + 1) % SZ == cur_rp) { + if (block_write) + base_t::spsc_check_w(); /* blocks, ensures next (!) call succeeds */ + return false; + } + buf[cur_wp] = *elem; + writeptr.store((cur_wp + 1) % SZ, std::memory_order_release); + if (block_read) + base_t::spsc_notify_r(); /* fine after release */ + return true; + } + + /*! Removes element from the queue by copying the data. + * \param[in] elem output buffer, must match the originally configured queue buffer size!. + * \returns true if queue was not empty and element was successfully removed */ + bool spsc_pop(ELEM *elem) + { + size_t cur_wp, cur_rp; + cur_wp = writeptr.load(std::memory_order_acquire); + cur_rp = readptr.load(std::memory_order_relaxed); + + if (cur_wp == cur_rp) /* blocks via prep_pop */ + return false; + + *elem = buf[cur_rp]; + readptr.store((cur_rp + 1) % SZ, std::memory_order_release); + if (block_write) + base_t::spsc_notify_w(); + return true; + } + + /*! Reads the read-fd of the queue, which, depending on settings passed on queue creation, blocks. + * This function can be used to deliberately wait for a non-empty queue on the read side. + * \returns result of reading the fd. */ + ssize_t spsc_prep_pop() + { + return base_t::spsc_check_r(); + } +}; + +} // namespace spsc_detail + +template <unsigned int SZ, typename ELEM, bool block_read, bool block_write> +class spsc_evfd : public spsc_detail::spsc<SZ, ELEM, block_read, block_write, spsc_detail::spsc_efd_detail> {}; +template <unsigned int SZ, typename ELEM, bool block_read, bool block_write> +class spsc_cond : public spsc_detail::spsc<SZ, ELEM, block_read, block_write, spsc_detail::spsc_cond_detail> {};
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