What is IO Stream Buffering?

Question

I am unable to find the underlying concept of IO Stream Buffering and what does it mean. Any tutorials and links will be helpful.

Answer 1

Buffering is a fundamental part of software that handles input and output. The buffer holds data that is in between the software interface and the hardware interface, since hardware and software run at different speeds.

A component which produces data can put it into a buffer, and later the buffer is "flushed" by sending the collected data to the next component. Likewise the other component may be "waiting on the buffer" until a complete piece of data, or enough data to be efficiently processed, is available for input.

In C++, std::basic_filebuf implements a buffer over a filesystem file. It stores up to a fixed number of bytes so the operating system always works with a minimum transaction size, while the program can access individual characters if desired.

See Wikipedia.

Answer 2

Buffering is using memory (users memory) instead of sending the data straight to the OS (i.e. disk). Saves on a context switch.

Answer 3

Here's the concept. Imagine you have an application that needs to write it's data onto the hard drive. Let's say it wants to write something (e.g. update a log file) every half of a second. Is this good? No, and here is the reason.

Software can be very fast, but the speed on which the HDD can operate is limited, and it's much slower than the memory, and your application. To write something, the HDD needs to reposition it's magnetic heads to a specific sector (which probably involves slowing the disc rotation speed), write the data, and reposition back to where it was. So your application could operate very slowly (well, that's a theoretical example of course).

Buffering helps to deal with this. Instead of writing to the disc each time, the data is being accumulated in the buffer somewhere in the memory. Once a sufficient amount of data is gathered, the buffer is flushed: the data from it gets written on the disk. Such approach helps to minimize HDD operations and improve overall speed.