C語言封裝的輕量線程環境 Protothreads

Protothreads是一種針對C語言封裝后的宏函數庫，為C語言模擬了一種無堆棧的輕量線程環境，能夠實現模擬線程的條件阻塞、信號量操作等操作系統中特有的機制，從而使程序實現多線程操作。每個Protothreads線程僅增加10行代碼和2字節RAM的額外硬件資源消耗。對于資源緊缺而不能移植嵌入式操作系統的嵌入式系統，使用Protothreads能夠方便直觀地設計多任務程序，能夠實現用線性程序結構處理事件驅動型程序和狀態機程序，簡化了該類程序的設計。

主要特性：

• Very small RAM overhead - only two bytes per protothread and no extra stacks
• Highly portable - the protothreads library is 100% pure C and no architecture specific assembly code
• Can be used with or without an OS
• Provides blocking wait without full multi-threading or stack-switching
• Freely available under a BSD-like open source license

示例程序：

• Memory constrained systems
• Event-driven protocol stacks
• Small embedded systems
• Sensor network nodes
• Portable C applications

示例代碼：

#include "pt.h"

struct pt pt;
struct timer timer;

PT_THREAD(example(struct pt *pt))
{
  PT_BEGIN(pt);

  while(1) {
    if(initiate_io()) {
      timer_start(&timer);
      PT_WAIT_UNTIL(pt,
         io_completed() ||
         timer_expired(&timer));
      read_data();
    }
  }
  PT_END(pt);
}

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