Efficient string trim?

Copying strings around is not efficient and since LSL does provide any kind of

string newString = llTrimString(string oldString);

I was wondering if anyone has a memory efficient method of trimming leading and trailing spaces from a string.

TIA,
Illy

not sure how efficient, but looks good

/15/fd/24496/1.html

string trim_spaces( string Text ) {

    integer prefix = 0; while( llGetSubString( Text, prefix, prefix ) == " " ) ++prefix;
    if( prefix == llStringLength( Text ) ) return ""; // sanity check if string happens to be all spaces.
    integer suffix = -1; while( llGetSubString( Text, suffix, suffix ) == " " ) --suffix;
    
    return llGetSubString( Text, prefix, suffix );
}

This uses ~1/3rd less memory than the list approach, but the code itself takes some ~190 bytes more when compiled and is way *way* slower (250 iterations took some 23 seconds while the list did the same task in ~4 secs) ... so use only for handling long strings in memory-tight environment when speed isn't crucial, i guess o.O;

Memory is a major issue; i had to replace a trim function in one of my scripts from using a list method to a string method. Fortunately I only needed to trim leading spaces.

We use 0x8000 so it can return a null string the number could be made larger without a proformance hit; just didn't feel the need with the 16k memory space.

The 'do-while' loop is faster then the 'while' because of how the bytecode is writen (i've talked to LL about changing how the 'while' is writen so it would be just as fast; they weren't keen).

string TrimLead(string a)
{//Trims leading spaces
	integer b = -1;
	do ++b;while(llGetSubString(a,b,b) == " ");
	return llGetSubString(a, b, 0x8000);
}

Would be nice if there was a string trim call in LSL which basically just passed the string to the C string trim function (which I can't recall at present).

Interesting Strife, thank you for that! How does a for loop compare in performance?

a 'for' loop is basicly

for(a;b;c)
{
    d;
}
//
a;
while(b)
{
    d;
    c;
}