[Boost-users] Reading key-value pairs from a string

Dear boost-users, I am currently working on a C++ project that includes reading and parsing some files. Given a string with certain file contents S, I would like to attempt to compare it against a certain pattern. In particular, the contents have the form key : value. Certain keys are obligatory, while others may or may not exist (my program then supplies the default values). Can you recommend me a boost facility that can help me reading this type of data? My problem is that between key, : and value there could be blank spaces, tabs etc. The type of value could be a string, an int, or double. Thanks in advance!