character string find replace, grep, strpos, or concat new one c/c++ efficiency

im interested in your experience with c/c++ find, find_first_of, replace, strpos, grep and concat. what is the most efficient method for replacing content in strings.

• no string replaces appear more than once per string
• the resulting string will not be the same length as the original.
• the original and final string will be less thn 2000 chars
• approximately 25 string replaces
• the needle remains consistent per haystack

ill test them, simply gathering options at this point.

here is the application at hand: a url string that needs extensive massaging. ie. almost all parameters will change, although the value will remain the same. from

param1=this&param2=string&param3=needs&param4=a&param5=lot ... &param25=work 

to

what=this&method=string&will=needs&work=a&the=lot ... &best=work 

i currently use a needle/haystack function that works on the existing string.

void findAndReplace(string& haystack, const string& needle, const string& replace) { size_t len = needle.size(); if (haystack.size() < len) return; size_t pos = haystack.find(needle); if (pos != string::npos) haystack.replace(pos, len, replace); } 

i dont mind using char*, string, streams, grep or other. and building a new string is also an option.

thanks