[Boost-users] Newbie question: block read inputs to regex

I'm using regex_grep() to search through file contents for matches. I want to read the file in blocks to keep memory use down for large files. What I want to know is whether there is some way of adding the next block of memory to the grep where the last one left off. The best solution I can come up with is using some sort of double-buffering scheme, but that would take an awful lot of memory copies and searching some text multiple times. Both things I would prefer to avoid. What can I do? --Brendan