Calculating string length without using inbuilt function in c#

Question

 string str = "test";
 int counter = 0;
 for (int i = 0; str[i] != '\n'; i++)
 {
    counter++;
 }

Unable to handle error index out of bound and I don't want to use the str.length property and also don't want foreach loop approach.

Please help

Thanks in advance.

Strings are not terminated by any special symbol in C# so this approach will not work. — Andrey Korneyev
– Andrey Korneyev, Commented Jan 14, 2015 at 7:32
Actually it is possible in c that's why I am thinking would it be possible in c#?? — Archna Saini
– Archna Saini, Commented Jan 14, 2015 at 7:35

Sudhakar Tillapudi · Accepted Answer · 2015-01-14 08:05:10Z

3

strings does not end with any special character in c#.

the only way i can think as of now for your requirement(as you don't want to use Framework functions) is accessing the characters in the string untill it throws the IndexOutOfRangeException Exception.

Try This: (not recommended)

string str = "test";
int counter = 0;

try
{
    for (int i = 0; ; i++)
    {
        char temp = str[i];
        counter++;
    }
}
catch(IndexOutOfRangeException ex)
{
}

Console.WriteLine(counter);

edited Jan 14, 2015 at 8:05

user2160375

answered Jan 14, 2015 at 7:36

Sudhakar Tillapudi

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Comments

user2160375 · Accepted Answer · 2015-01-14 07:59:16Z

I've found some interesting function inside String.cs (disassembled):

private static unsafe int wcslen(char* ptr)
{
    char* end = ptr;
    while (((uint)end & 3) != 0 && *end != 0)
        end++;
    if (*end != 0)
    {
        while ((end[0] & end[1]) != 0 || (end[0] != 0 && end[1] != 0))
        {
            end += 2;
        }
    }
    for (; *end != 0; end++)
        ;

    int count = (int)(end - ptr);

    return count;
}

usage:

class Program
{
    private static void Main(string[] args)
    {
        var a = "asample";

        unsafe
        {
            fixed (char* str_char = a)
            {
                var count = wcslen(str_char);
            }
        }
    }

    private static unsafe int wcslen(char* ptr)
    {
      // impl
    }
}

Just curiosity. Not recommended in real code. The most interesting thing: Here is comment inside that wcslen function:

// The following code is (somewhat surprisingly!) significantly faster than a naive loop,
// at least on x86 and the current jit.

:)

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