Arduino的F（）：这是什么实际上做

问题描述

我已经问过一个类似的问题，但我知道我可以' ŧ使磁头或赘言和templateness的尾巴。我是一个C（而不是C ++）程序员。

I have asked a similar question before, but I realize that I can't make heads or tails of the macrology and templateness. I'm a C (rather than C++) programmer.

什么是F（）实际上呢？当它的东西字符转换成pgmem？当它拉出来的字符的pgmem？是否缓存它们？它是怎样处理的低内存情况？

What does F() actually do? When does it stuff characters into pgmem? When does it pull characters out of pgmem? Does it cache them? How does it handle low-memory situations?

推荐答案

有没有涉及模板，只有函数重载。在 F（）宏做了两件事：

There are no templates involved, only function overloading. The F() macro does two things:

• 使用 PSTR 来确保文字字符串存储在Flash存储器（code空间而非数据空间）。然而， PSTR（一些字符串）无法打印，因为这样会得到一个简单的的char * 这再次presents存储在闪存字符串的基址。解引用该指针将在数据同一地址访问某些随机字符。这就是为什么 F（）也...

• uses PSTR to ensure that the literal string is stored in Flash memory (the code space rather than the data space). However, PSTR("some string") cannot be printed because it would receive a simple char * which represents a base address of the string stored in Flash. Dereferencing that pointer would access some random characters from the same address in data. Which is why F() also...

蒙上的结果PSTR（）到 __ FlashStringHelper * 。功能，如打印和的println 超载，这样，在接收到 __ FlashStringHelper * 的说法，他们正确地取消引用在闪存中的字符。

casts the result of PSTR() to __FlashStringHelper*. Functions such as print and println are overloaded so that, on receiving a __FlashStringHelper* argument, they correctly dereference the characters in the Flash memory.

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