CODEWITHSUNDEEP
c++visual-studio-2005iostream
Joe M
Joe M

Reputation: 3420

How does fstream work? Memory or file?

I'm not finding a clear answer to one aspect of the fstream object necessary to determine whether it is worth using. Does fstream store its contents in memory, or is it more like a pointer to a location in a file? I was originally using CFile and reading the text into a CString, but I'd rather not have the entire file in memory if I can avoid it.

Upvotes: 8

Views: 2761

Answers (1)

Jerry Coffin
Jerry Coffin

Reputation: 490128

fstream is short for file stream -- it's normally a connection to a file in the host OS's file system. (§27.9.1.1/1: "The class basic_filebuf<charT,traits> associates both the input sequence and the output sequence with a file.")

It does (normally) buffer some information from that file, and if you happen to be working with a tiny file, it might all happen to fit in the buffer. In a typical case, however, most of the data will be in a file on disk (or at least in the OS's file cache) with some relatively small portion of it (typically a few kilobytes) in the fstream's buffer.

If you did want to use a buffer in memory and have it act like a file, you'd normally use a std::stringstream (or a variant like std::istringstream or std::ostringstream).

Upvotes: 7

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