Length of a string without using any built-in functions

Question

code that returns the length of a string without using any built-in functions.
thanks
Sam

Answer 1

A string is internally represented by a character array.  An array of characters will reside on the stack, not the heap.  Yes, we always learned that String is a reference type, but what goes on in your memory might still surprise you...
A struct is internally represented by only it's private properties, sequentially on the stack.
So basically, what I thought is happening by messing with the structlayout: is only tricking our programming a bit into thinking that the top X bytes on the stack represent a chararray, while actually we put them there as a string.
Wrong. True. And wrong.
A string is internally represented by, in that order, an array length, a string length, the chars. None of them resides on the stack.
An array is internally represented by, in that order, an array length and the chars. None of them resides on the stack.
When you use the FieldOffset attribute to handle the string as a char array, you don't get anything right:
- the Length returned is the "array length" of the string, which is equal to the string length + 1.
- the chars returned by the array indexer are shifted by 2 chars (the length of the "string length" field).
You can use the FieldOffset to make that work, but it needs a little bit more work.
unsafe static int Test()
string myString = "This string may contain many string inside this string";
string testString = "string";
int countResult = 0;
fixed (char* myChars = new StringToChar { str = myString }.chr, testChar = new StringToChar { str = testString }.chr)
// The 2 first chars of the array are actually the string length.
int myCharsLength = myChars[1] << 16 | myChars[0];
int testCharLength = testChar[1] << 16 | testChar[0];
for (int i = 0; i < myCharsLength - testCharLength + 1; i++)
if (myChars[i + 2] == testChar[2])
for (int j = 1; j < testCharLength; j++)
var c = testChar[7];
if (myChars[i + 2 + j] != testChar[j + 2])
goto endOfCharAnalyses;
countResult++;
endOfCharAnalyses:
continue;
return countResult;