rename PIBlockingDequeue -> PIBlockingQueue
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218
lib/main/thread/piblockingqueue.h
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218
lib/main/thread/piblockingqueue.h
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/*
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PIP - Platform Independent Primitives
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Stephan Fomenko
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef PIBLOCKINGQUEUE_H
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#define PIBLOCKINGQUEUE_H
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#include "pideque.h"
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#include "piconditionvar.h"
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/**
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* @brief A Queue that supports operations that wait for the queue to become non-empty when retrieving an element, and
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* wait for space to become available in the queue when storing an element.
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*/
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template <typename T>
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class PIBlockingQueue: private PIQueue<T> {
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public:
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/**
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* @brief Constructor
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*/
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explicit inline PIBlockingQueue(size_t capacity = SIZE_MAX,
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PIConditionVariable* cond_var_add = new PIConditionVariable(),
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PIConditionVariable* cond_var_rem = new PIConditionVariable())
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: cond_var_add(cond_var_add), cond_var_rem(cond_var_rem), max_size(capacity) { }
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/**
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* @brief Copy constructor. Initialize queue with copy of other queue elements. Not thread-safe for other queue.
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*/
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explicit inline PIBlockingQueue(const PIDeque<T>& other) : cond_var_add(new PIConditionVariable()), cond_var_rem(new PIConditionVariable()) {
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mutex.lock();
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max_size = SIZE_MAX;
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PIDeque<T>::append(other);
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mutex.unlock();
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}
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/**
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* @brief Thread-safe copy constructor. Initialize queue with copy of other queue elements.
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*/
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inline PIBlockingQueue(PIBlockingQueue<T> & other) : cond_var_add(new PIConditionVariable()), cond_var_rem(new PIConditionVariable()) {
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other.mutex.lock();
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mutex.lock();
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max_size = other.max_size;
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PIDeque<T>::append(static_cast<PIDeque<T>&>(other));
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mutex.unlock();
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other.mutex.unlock();
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}
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~PIBlockingQueue() {
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delete cond_var_add;
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delete cond_var_rem;
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}
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/**
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* @brief Inserts the specified element into this queue, waiting if necessary for space to become available.
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*
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* @param v the element to add
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*/
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PIBlockingQueue<T> & put(const T & v) {
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mutex.lock();
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cond_var_rem->wait(mutex, [&]() { return PIDeque<T>::size() < max_size; });
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PIDeque<T>::push_back(v);
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mutex.unlock();
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cond_var_add->notifyOne();
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return *this;
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}
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PIBlockingQueue<T> & enqueue(const T & v) {return put(v);}
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/**
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* @brief Inserts the specified element at the end of this queue if it is possible to do so immediately without
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* exceeding the queue's capacity, returning true upon success and false if this queue is full.
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*
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* @param v the element to add
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* @return true if the element was added to this queue, else false
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*/
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bool offer(const T & v, int timeoutMs = 0) {
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bool isOk;
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mutex.lock();
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if (timeoutMs == 0)
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isOk = PIDeque<T>::size() < max_size;
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else
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isOk = cond_var_rem->waitFor(mutex, timeoutMs, [&]() { return PIDeque<T>::size() < max_size; } );
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if (isOk) PIDeque<T>::push_back(v);
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mutex.unlock();
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if (isOk) cond_var_add->notifyOne();
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return isOk;
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}
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/**
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* @brief Retrieves and removes the head of this queue, waiting if necessary until an element becomes available.
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*
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* @return the head of this queue
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*/
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T take() {
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T t;
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mutex.lock();
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cond_var_add->wait(mutex, [&]() { return !PIDeque<T>::isEmpty(); });
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t = T(PIDeque<T>::take_front());
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mutex.unlock();
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cond_var_rem->notifyOne();
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return t;
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}
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T dequeue() {return take();}
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/**
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* @brief Retrieves and removes the head of this queue, waiting up to the specified wait time if necessary for an
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* element to become available.
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*
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* @param timeoutMs how long to wait before giving up, in milliseconds
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* @param defaultVal value, which returns if the specified waiting time elapses before an element is available
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* @param isOk flag, which indicates result of method execution. It will be set to false if timeout, or true if
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* return value is retrieved value
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* @return the head of this queue, or defaultVal if the specified waiting time elapses before an element is available
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*/
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T poll(int timeoutMs = 0, const T & defaultVal = T(), bool * isOk = nullptr) {
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T t = defaultVal;
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bool isNotEmpty;
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mutex.lock();
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if (timeoutMs == 0)
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isNotEmpty = !PIDeque<T>::isEmpty();
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else
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isNotEmpty = cond_var_add->waitFor(mutex, timeoutMs, [&]() { return !PIDeque<T>::isEmpty(); });
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if (isNotEmpty) t = PIDeque<T>::take_front();
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mutex.unlock();
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if (isNotEmpty) cond_var_rem->notifyOne();
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if (isOk) *isOk = isNotEmpty;
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return t;
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}
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/**
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* @brief Returns the number of elements that this queue can ideally (in the absence of memory or resource
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* constraints) contains. This is always equal to the initial capacity of this queue less the current size of this queue.
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*
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* @return the capacity
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*/
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size_t capacity() {
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size_t c;
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mutex.lock();
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c = max_size;
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mutex.unlock();
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return c;
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}
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/**
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* @brief Returns the number of additional elements that this queue can ideally (in the absence of memory or resource
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* constraints) accept. This is always equal to the initial capacity of this queue less the current size of this queue.
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*
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* @return the remaining capacity
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*/
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size_t remainingCapacity() {
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mutex.lock();
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size_t c = max_size - PIDeque<T>::size();
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mutex.unlock();
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return c;
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}
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/**
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* @brief Returns the number of elements in this collection.
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*/
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size_t size() {
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mutex.lock();
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size_t s = PIDeque<T>::size();
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mutex.unlock();
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return s;
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}
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/**
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* @brief Removes all available elements from this queue and adds them to other given queue.
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*/
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size_t drainTo(PIDeque<T>& other, size_t maxCount = SIZE_MAX) {
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mutex.lock();
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size_t count = ((maxCount > PIDeque<T>::size()) ? PIDeque<T>::size() : maxCount);
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for (size_t i = 0; i < count; ++i) other.push_back(PIDeque<T>::take_front());
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mutex.unlock();
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return count;
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}
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/**
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* @brief Removes all available elements from this queue and adds them to other given queue.
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*/
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size_t drainTo(PIBlockingQueue<T>& other, size_t maxCount = SIZE_MAX) {
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mutex.lock();
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other.mutex.lock();
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size_t count = maxCount > PIDeque<T>::size() ? PIDeque<T>::size() : maxCount;
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size_t otherRemainingCapacity = other.max_size - static_cast<PIDeque<T> >(other).size();
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if (count > otherRemainingCapacity) count = otherRemainingCapacity;
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for (size_t i = 0; i < count; ++i) other.push_back(PIDeque<T>::take_front());
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other.mutex.unlock();
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mutex.unlock();
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return count;
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}
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private:
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PIMutex mutex;
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PIConditionVariable * cond_var_add, * cond_var_rem;
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size_t max_size;
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};
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#endif // PIBLOCKINGQUEUE_H
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