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58 lines
1.5 KiB
C++
58 lines
1.5 KiB
C++
#pragma once
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#include "../object/queue.h"
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#include "../types.h"
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/*! \file
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* \brief \ref Semaphore for synchronization of threads.
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*/
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/*!
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* \defgroup ipc Inter-Process Communication
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* \brief Communication between threads
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*/
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// Forward declarations to break cyclic includes
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struct Vault;
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class Thread;
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/*! \brief Semaphore used for synchronization of threads.
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* \ingroup ipc
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*
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* The class Semaphore implements the concept of counting semaphores.
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* The waiting list is provided by the base class Waitingroom.
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*/
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class Semaphore {
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// Prevent copies and assignments
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Semaphore(const Semaphore&) = delete;
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Semaphore& operator=(const Semaphore&) = delete;
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static Thread** thread_link(Thread& obj, unsigned link_index);
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public:
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/*! \brief Constructor; initialized the counter with provided value `c`
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* \param c Initial counter value
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*
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* \todo(16) Implement Constructor
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*/
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explicit Semaphore(unsigned c = 0);
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/*! \brief Wait for access to the critical area.
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*
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* Enter/Wait operation: If the counter is greater than 0, then it is
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* decremented by one. Otherwise the calling thread will be enqueued
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* into the Waitingroom and marked as blocked.
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*
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* \todo(16) Implement Method
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*/
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void p(Vault& vault);
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/*! \brief Leave the critical area.
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*
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* Leave operation: If there are threads in the Waitingroom, wake the
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* first one; otherwise increment the counter by one.
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*
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* \todo(16) Implement Method
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*/
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void v(Vault& vault);
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};
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