如何在c#中实现strlen()？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/1083550/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
how to implement strlen() in c#?
提问by Learner
I was thinking to a solution to calculate length of string in c# without using Lengthproperty.
我正在考虑一种在不使用Length属性的情况下计算 c# 中字符串长度的解决方案。
I thing which I can think of is getting this done is
我能想到的就是完成这件事
Program is in C#
程序在 C# 中
public static int strlen (string s)
{
string temp = s + '/0';
char [] c = temp.ToCharArray();
int length = 0;
while (c[length]!='/0') length++;
length--;
return length;
}
but this is very naive programming, it also uses 1 extra temp variable Can you guys think of better solution than this?
但这是非常幼稚的编程，它还使用了 1 个额外的临时变量 你们能想到比这更好的解决方案吗？
回答by leiz
public static int strlen2 (string s) {
int length = 0;
foreach (char c in s) length++;
return length
}
I am not sure what is the point of doing that though.
我不确定这样做有什么意义。
回答by John T
If you want the most efficient way you could try to mimic Microsoft's own String.Length function. Fire up .NET Reflectorand load a small sample solution in that calls String.Length. Then you can simply burrow down into the dependencies and even do some disassembling.
如果你想要最有效的方式，你可以尝试模仿微软自己的 String.Length 函数。启动.NET Reflector并加载一个小示例解决方案，其中调用 String.Length。然后，您可以简单地深入了解依赖项，甚至进行一些反汇编。
回答by Jeremy Salwen
The issue is the way strings are stored in C#. While in some languages it takes computation to figure out how long a string is, in C#, the onlyway to figure out the length of a string is through its Length property. If you thing about how strings are stored, there is an array of character, and a Length. Now, the strings are notnull-terminated, so you needthe Length field to know how much of the array you can access before you start reading memory that isn't part of the array. You can hidewhat you are doing through abstraction though. For example you can call the ToCharArray function, but in order to generate the null-terminated string which you use, it first has to access the Length value to allocated the right amount of memory for the char[] array and copy the right amount of characters. Or you could use a for each (char c in s) length++;
问题是字符串在 C# 中的存储方式。虽然在某些语言中需要计算才能确定字符串的长度，但在 C# 中，确定字符串长度的唯一方法是通过其 Length 属性。如果您关心字符串的存储方式，则有一个字符数组和一个长度。现在，字符串不是以空值结尾的，因此在开始读取不属于数组的内存之前，您需要Length 字段来了解您可以访问多少数组。你可以隐藏你正在通过抽象做什么。例如，您可以调用 ToCharArray 函数，但为了生成您使用的以空字符结尾的字符串，它首先必须访问 Length 值以为 char[] 数组分配适量的内存并复制适量的人物。或者你可以使用 a for each (char c in s) length++;
as somebody else suggested. This is another way to hide the fact you are accessing the Length value. In order to iterate over the characters in this way, you must first access the Length value to see how many characters you are iterating over. Whether it does this in a library call, or it compiles it away to a different construct, I am not sure, but the end result is the same.
正如其他人所建议的那样。这是隐藏您正在访问 Length 值这一事实的另一种方法。为了以这种方式迭代字符，您必须首先访问 Length 值以查看您要迭代多少个字符。无论是在库调用中执行此操作，还是将其编译为不同的构造，我都不确定，但最终结果是相同的。
回答by Nadewad
I think to optimize a bit on Leiz's answer, I would use pre-increment instead of post increment on line 3 to read:
我认为要优化 Leiz 的答案，我会在第 3 行使用预增量而不是后增量来阅读：
foreach(char c in s) ++length
Which would squeeze a tiny bit of performance out of it.
这会从中挤出一点点性能。
回答by arul
You can get the length at O(1) speed using unsafe code, since C# strings are prefixed with their length - this is probably what the get_Length function does internally (and thats why you should use the built-in way instead of writing your own):
您可以使用不安全代码以 O(1) 速度获取长度，因为 C# 字符串以其长度为前缀 - 这可能是 get_Length 函数在内部执行的操作（这就是为什么您应该使用内置方式而不是编写自己的方式） )：
public static unsafe int strlen(string s)
{
if(s == null) {
// Handle the error here
}
int length = 0;
fixed(char *pStr = s) {
length = *(((int *)pStr) - 1);
}
return length;
}
Or if you prefer more old schoolish approach:
或者，如果您更喜欢更老派的方法：
public static unsafe int strlen(string s)
{
if(s == null) {
// Handle the error here
}
int length = 0;
fixed(char *pStr = s) {
char *pEnd = pStr;
while(*pEnd++ != '##代码##');
length = (int)((pEnd - pStr) - 1);
}
return length;
}
