Using string's char* based constructor

AceInfinity · Jun 19, 2012

I'm fooling around in VS this morning after had no sleep:

Code:

private static unsafe string CToString(char[] charPtr, int startIndex)
{
    fixed (char* c = &charPtr[startIndex]) return new string(c);
}

This takes the char array and an integer as parameters, and with that char array, converts it to a char* based on a start index specified by the second param, in order to take the address of a char[] which is considered an unfixed expression, you'll notice that I've put it into the fixed statement (this would be required otherwise you get a compiler error). From there we use the string constructor which requests a char* and return it.

This returns the string value of each char afterwards from then on based on the specified startIndex.

Note: If this char value is a value of 0, it will terminate itself at that point when returning the string. (I'll show an example to show you what I mean.)

To test my function, here's a test snippet inside of a button click:

Code:

private void button1_Click(object sender, EventArgs e)
{
	char[] vals = new char[] { 'h', 'e', 'l', 'l', 'o' };
	string s = CToString(vals, 0);
	Console.WriteLine(s);
}

If you did this:

Code:

private void button1_Click(object sender, EventArgs e)
{
	char[] vals = new char[] { 'h', 'e', 'l', 'l', 'o', (char)0, 't', 'e', 's', 't' };
	string s = CToString(vals, 0);
	Console.WriteLine(s);
}

You would notice that none of the values after '(char)0' would show...

Notes:
-Must compile with unsafe context on
-Must declare unsafe code in the method header or in it's own little statement/wrapper.

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Using string's char* based constructor

AceInfinity

Emeritus, Contributor