Qt Code: 
  1. #include <QtCore>
  2. #include <iostream>
  3.  
  4. const int DataSize = 20;
  5. const int BufferSize = 10;
  6. char buffer[BufferSize];
  7.  
  8. QSemaphore freeSpace(BufferSize);     // for producer
  9. QSemaphore usedSpace(0);                // for consumer
  10.  
  11. class Producer : public QThread
  12. {
  13. public:
  14.     void run();
  15. };
  16.  
  17. void Producer::run()
  18. {
  19.     for (int i = 0; i < DataSize; ++i) {
  20.         freeSpace.acquire();
  21.         buffer[i % BufferSize] = "ACGT"[uint(std::rand()) % 4];
  22.         std::cerr <<"Producer: buffer["<<i % BufferSize<<"]"<<buffer[i % BufferSize]<<std::endl;
  23.         usedSpace.release();
  24.     }
  25. }
  26.  
  27. class Consumer : public QThread
  28. {
  29. public:
  30.     void run();
  31. };
  32.  
  33. void Consumer::run()
  34. {
  35.     for (int i = 0; i < DataSize; ++i) {
  36.         usedSpace.acquire();
  37.          buffer[i % BufferSize] = "ACGT"[uint(std::rand()) % 4];
  38.          std::cerr <<"Consumer: buffer["<<i % BufferSize<<"]"<<buffer[i % BufferSize]<<std::endl;
  39.         freeSpace.release();
  40.     }
  41.     //std::cerr << std::endl;
  42. }
  43.  
  44. int main()
  45. {
  46.     Producer producer;
  47.     Consumer consumer;
  48.     producer.start();
  49.     consumer.start();
  50.     producer.wait();
  51.     consumer.wait();
  52.     return 0;
  53. }
  54.  
  55.  
  56. //pro file
  57. TEMPLATE      = app
  58. CONFIG       += console thread
  59. CONFIG       -= app_bundle
  60. SOURCES       = semaphores.cpp
  61.  
  62. // one output is showed here
  63. Producer: buffer[0]C
  64. Producer: buffer[Consumer: buffer[01]]CT
  65.  
  66. Producer: buffer[Consumer: buffer[12]G]T
  67.  
  68. Producer: buffer[3]Consumer: buffer[2A
  69. ]G
  70. Producer: buffer[4Consumer: buffer[3]C
  71. ]AProducer: buffer[
  72. 5]Consumer: buffer[4A
  73. ]C
  74. Producer: buffer[6Consumer: buffer[]G5]
  75. A
  76. Producer: buffer[7Consumer: buffer[6]G
  77. ]G
  78. Producer: buffer[8Consumer: buffer[]G7]
  79. G
  80. Producer: buffer[Consumer: buffer[89]A
  81. ]GProducer: buffer[0
  82. Consumer: buffer[]C
  83. 9]Producer: buffer[A1]C
  84. Consumer: buffer[
  85. 0]Producer: buffer[2C
  86. ]C
  87. Consumer: buffer[1Producer: buffer[]3C]T
  88.  
  89. Consumer: buffer[2Producer: buffer[4]C]C
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In this example,why would comes the output like this: Producer: buffer[Consumer: buffer[01]]CT. Isn't it should be all like this:Producer: buffer[0]C

Thanks!