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1 #pragma once
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2
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3
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4 namespace fb2k {
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5 //! fb2k::readWriteLock: abortable readWriteLock, allowing multiple concurrent readers while not writing, or one writer while not reading. \n
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6 //! Safe to release locks in different threads than obtained, contrary to system object such as SRW locks.
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7 class readWriteLock {
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8 pfc::mutex m_guard;
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9 size_t m_readers = 0, m_writers = 0;
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10 typedef std::shared_ptr < pfc::event> eventRef_t;
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11 eventRef_t m_currentEvent;
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12 public:
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13
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14 void shutdown() {
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15 for (;;) {
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16 eventRef_t waitFor;
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17 {
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18 PFC_INSYNC(m_guard);
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19 if (m_readers == 0 && m_writers == 0) return;
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20 PFC_ASSERT(m_currentEvent);
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21 waitFor = m_currentEvent;
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22 }
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23 waitFor->wait_for(-1);
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24 }
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25 }
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26
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27 service_ptr beginRead(abort_callback& a) {
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28 for (;;) {
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29 a.check();
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30 eventRef_t waitFor;
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31 {
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32 PFC_INSYNC(m_guard);
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33 if (m_writers == 0) {
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34 if (!m_currentEvent) m_currentEvent = std::make_shared<pfc::event>();
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35 ++m_readers;
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36 return fb2k::callOnRelease([this] {
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37 PFC_INSYNC(m_guard);
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38 PFC_ASSERT(m_currentEvent);
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39 PFC_ASSERT(m_readers > 0 && m_writers == 0);
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40 if (--m_readers == 0) {
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41 m_currentEvent->set_state(true); m_currentEvent = nullptr;
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42 }
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43 });
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44 }
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45 PFC_ASSERT(m_currentEvent);
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46 waitFor = m_currentEvent;
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47 }
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48 a.waitForEvent(*waitFor);
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49 }
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50 }
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51 service_ptr beginWrite(abort_callback& a) {
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52 for (;;) {
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53 a.check();
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54 eventRef_t waitFor;
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55 {
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56 PFC_INSYNC(m_guard);
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57 if (m_readers == 0 && m_writers == 0) {
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58 m_currentEvent = std::make_shared<pfc::event>();
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59 ++m_writers;
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60 return fb2k::callOnRelease([this] {
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61 PFC_INSYNC(m_guard);
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62 PFC_ASSERT(m_currentEvent);
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63 PFC_ASSERT(m_readers == 0 && m_writers > 0);
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64 if (--m_writers == 0) {
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65 m_currentEvent->set_state(true); m_currentEvent = nullptr;
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66 }
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67 });
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68 }
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69 PFC_ASSERT(m_currentEvent);
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70 waitFor = m_currentEvent;
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71 }
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72 a.waitForEvent(*waitFor);
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73 }
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74 }
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75
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76 };
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77 }
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