ProtoThreads如何工作的.doc

ProtoThreads如何工作的 最近把手头的SD卡更新NK到NAND项目完成，总算抽空上网瞎逛游了。正好群里面有人推荐了一个系统，说是对小资源的单片机非常适合。这里我就推荐2篇网文： /bibis/moredata30_1234764_43130.shtml /t_larry/archive/2008/10/18/3097191.aspx 这2篇网文一个讲系统简介，一个是里面宏的说明。熟悉一下是很不错的。 然后就是官网了： http://www.sics.se/~adam/pt/index.html 我翻译了里面的under the hood?章节：How protothreads really work ? What goes on behind the magical macros in the C protothreads library? Why are they macros? How do the macros work? Read on for the explanation. 在C protothreads库里面的神奇宏到底发生了什么？他们为什么都是宏？这些宏是如何工作的？请接着读解释： ? In the C implementation of protothreads, all protothread operations are hidden behind C macros. The reason for building the protothread library on C macros rather than C functions is that protothreads alter the flow of control. This is typically difficult to do with C functions since such an implementation typically would require low-level assembly code to work. By implementing protothreads with macros, it is possible for them to alter the flow of control using only standard C constructs. 在Protothreads系统C的实现里，所有的protothread操作都被隐藏在C的宏里面。生成protothread库用C的宏而不是用C函数的原因是protothreads需要改变程序的跳转，这通常是很难用C函数做，因为这样的实现通常需要低级别的汇编代码的工作。通过protothreads宏的实施，它有可能只使用标准C结构为他们改变程序的跳转。 ? This page explains how protothreads work under the hood. We do this by taking a look at how the C preprocessor expands the protothread macros, and by looking at how the resulting C code is executed. 这页介绍了protothreads在这个hood下如何工作。我们来看看protothread C预处理宏如何工作，如何生成C代码被执行。 ? First, well introduce a simple example program written with protothreads. Since this is a simple program we can show the entire program, including the main() function from which the protothread is driven. The code, shown below, waits for a counter to reach a certain threshold, prints out a message, and resets the counter. This is done in a while() loop that runs forever. The counter is increased in the main() function. 首先，我们将介绍一个简单的用protothreads写的例子程序。由于这是一个简单的程序就可以显示整个程序，包括main（）函数启动protothreads。代码如下所示，等待计数器达到一定的阈值就打印出一条消息，并重置计数器。这是在一