Fix threads

CMakeLists.txt

@@ -26,3 +26,4 @@ add_subdirectory(third-party/fmt)
 
 # Include CMakeLists files from subdirs for specific tasks
 add_subdirectory(task1)
+add_subdirectory(task3)

CMakePresets.json

@@ -7,14 +7,24 @@
   },
   "configurePresets": [
     {
-      "name": "task1@release",
+      "name": "task@release",
-      "displayName": "Task1 Release build",
+      "displayName": "Task Release build",
-      "description": "Builds the targets of task1 as release",
+      "description": "Builds the target as release",
       "generator": "Ninja",
-      "binaryDir": "${sourceDir}/.out/task1-release",
+      "binaryDir": "${sourceDir}/.out/task-release",
       "cacheVariables": {
         "CMAKE_BUILD_TYPE": "Release"
       }
+    },
+    {
+      "name": "task@debug",
+      "displayName": "Task Debug build",
+      "description": "Builds the target as debug",
+      "generator": "Ninja",
+      "binaryDir": "${sourceDir}/.out/task-debug",
+      "cacheVariables": {
+        "CMAKE_BUILD_TYPE": "Debug"
+      }
     }
   ]
 }

task3/CMakeLists.txt

@@ -0,0 +1,8 @@
+
+find_package(Qt6 COMPONENTS Core REQUIRED)
+
+add_executable(task3-chpt3ex12)
+target_sources(task3-chpt3ex12 PRIVATE
+        main.cpp)
+target_link_libraries(task3-chpt3ex12 PRIVATE
+Qt6::Core)

task3/main.cpp

@@ -0,0 +1,90 @@
+#include <iostream>
+#include <QSemaphore>
+#include <QThread>
+#include <QCoreApplication>
+
+/*
+ * Barlas Chpt 3 Ex 12:
+    Create three threads, each printing out the letters A, B, and C.
+    The printing must adhere to these rules:
+        • The total number of Bs and Cs that have been output at any
+          point in the output string cannot exceed the total number
+          of As that have been output at that point.
+        • After a C has been output, another C cannot be output until
+          one or more Bs have been output.
+    Use semaphores to solve the problem.
+*/
+
+class Printer {
+private:
+    QSemaphore &lockBC;
+    QSemaphore &lockC;
+
+public:
+    explicit Printer(QSemaphore &lockBC, QSemaphore &lockC) : lockBC(lockBC), lockC(lockC) {};
+
+    void printA() {
+        this->lockBC.release(1);
+        std::cout << "A\n";
+    }
+
+    void printB() {
+        if (this->lockBC.tryAcquire(1, 10000)) {
+            if (this->lockC.available() == 0) {
+                this->lockC.release(1);
+            }
+            std::cout << "B\n";
+        }
+    }
+
+    void printC() {
+        if (this->lockBC.tryAcquire(1, 10000)) {
+            if (this->lockC.tryAcquire(1, 10000)) {
+                std::cout << "C\n";
+            } else {
+                this->lockBC.release(1);
+            }
+        }
+    }
+};
+
+class Worker : public QThread {
+private:
+    QSemaphore &lockBC;
+    QSemaphore &lockC;
+
+public:
+    Worker(QSemaphore &lockBC, QSemaphore &lockC) : lockBC(lockBC), lockC(lockC) {};
+
+protected:
+    void run() {
+        Printer print = Printer(this->lockBC, this->lockC);
+        print.printA();
+        print.printB();
+        print.printC();
+    }
+};
+
+
+int main(int argc, char *argv[]) {
+    QCoreApplication app(argc, argv);
+    QSemaphore lockC(1);
+    QSemaphore lockBC(0);
+
+    Worker trd1(lockBC, lockC);
+    Worker trd2(lockBC, lockC);
+    Worker trd3(lockBC, lockC);
+
+    trd1.start();
+    trd2.start();
+    trd3.start();
+
+//    int N = 3;
+//    Worker *workers[N];
+//    for (int i = 0; i < N; i++) {
+//        workers[i] = new Worker(lockBC, lockC);
+//        workers[i]->run();
+//    }
+
+    return app.exec();
+}