What algorithm used for searching substring

[Habibutsu]

Hi all. Please explain me or give a link where I can read (or to see in 
sources) about algorithms that used in libstdc++ for searching. In 
particular I have interest what method used to find substring in string.

When i use "std::string::find" it's mean that in actually will be used 
"std::search" or will be used more effective algorithm (for example 
Knuth–Morris–Pratt)

Thank you