C语言 斯特伦：它是如何工作的？
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原文地址: http://stackoverflow.com/questions/4132849/
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strlen: how does it work?
提问by Manu
How does strlen()work internally?
strlen()内部如何运作？
回答by paxdiablo
strlenusually works by counting the characters in a string until a \0character is found. A canonical implementation would be:
strlen通常通过计算字符串中的字符直到\0找到一个字符来工作。规范的实现将是：
size_t strlen (char *str) {
size_t len = 0;
while (*str != '##代码##') {
str++;
len++;
}
return len;
}
There is no inherent bug in the function, it works exactly as documented.
该函数没有固有的错误，它完全按照文档工作。
That's not to say it doesn't have problems, to wit:
这并不是说它没有问题，即：
- if you pass it a "string" that doesn't have a
\0at the end, you may run into problems but technically, that's not a C string (a)and it's your own fault. - you can't put
\0characters in your string but, again, it wouldn't be a C string in that case. - it's not the most efficient way - you could store a length up front so you could get the length much quicker.
- 如果您传递给它一个末尾没有 a 的“字符串”
\0，您可能会遇到问题，但从技术上讲，这不是 C 字符串(a)，这是您自己的错。 - 您不能
\0在字符串中放入字符，但同样，在这种情况下它不会是 C 字符串。 - 这不是最有效的方法 - 您可以预先存储长度，以便更快地获得长度。
But none of those are bugs, they're just consequences of a design decision.
但这些都不是错误，它们只是设计决策的结果。
See also this excellent articleby Joel Spolsky where he discusses various string formats and their characteristics, including normal C strings, Pascal strings and the combination of the two, null terminated Pascal strings, though he has a more, shall we say, "colorful" term for them :-)
另请参阅Joel Spolsky撰写的这篇优秀文章，他在其中讨论了各种字符串格式及其特征，包括普通 C 字符串、Pascal 字符串以及两者的组合、空终止的 Pascal 字符串，尽管他还有更多，容我们说，“多彩”他们的术语:-)
(a)A C string is defined as a series of non-terminator characters (ie, any other than \0) followed by that terminator. Hence this definition disallows both embedded terminators within the sequence and sequences without such a terminator.
(a)AC 字符串定义为一系列非终止符（即，除 之外的任何字符\0）后跟该终止符。因此，该定义不允许在序列中嵌入终止符和没有这样的终止符的序列。
Or, putting it more succinctly (as per the ISO standard):
或者，更简洁地说（根据 ISO 标准）：
A string is a contiguous sequence of characters terminated by and including the first null character.
字符串是由第一个空字符终止并包括第一个空字符的连续字符序列。
