Thread: data from a file instead of memory

I am sure there is a simple answer to this, but I sure can't find it. I have found myself practicly writing a database, but its all in memory.

I am using MSVC 6 MFC template class CMap. It works great, does what I need and its fast. However, my dataset is large, say 20MB or so and I don't want to clog up the memory.

I store the data on disk, but when I serialize in my CMap it sucks the whole file into memory.

Is there a way to get the benefits of CMap functionality with the data being accessed directly from the file?

Look up on MSDN for Memory Mapped Files.....

File Mapping Functions
The following functions are used with file mapping.



CreateFileMapping
FlushViewOfFile
MapViewOfFile
MapViewOfFileEx
MapViewOfFileVlm
OpenFileMapping
UnmapViewOfFile
UnmapViewOfFileVlm

With them you can create a map of a peart of a big file, work on it, close the mapping (dont get confused withthe map you are using as a data struct ) and that segment will be saved to disk

Thanks. That looks like it may do the trick. I'll let you know.

Thanks for the info, but I found a different way to go. Use a database file without a database.

http://www.codeguru.com/mfc_database/daoarticle.html

That's a good link