tree aa9a1d6c98a8a2090ec035181e6b4bf5c01c8c9d
parent 329f74d463598731ea3ed2fa6b8730133ec93055
author Willy Tarreau <w@1wt.eu> 1267138471 +0100
committer Willy Tarreau <w@1wt.eu> 1267138471 +0100
encoding latin1

[MEDIUM] http: don't use trash to realign large buffers

The trash buffer may now be smaller than a buffer because we can tune
it at run time. This causes a risk when we're trying to use it as a
temporary buffer to realign unaligned requests, because we may have to
put up to a full buffer into it.

Instead of doing a double copy, we're now relying on an open-coded
bouncing copy algorithm. The principle is that we move one byte at
a time to its final place, and if that place also holds a byte, then
we move it too, and so on. We finish when we've moved all the buffer.
It limits the number of memory accesses, but since it proceeds one
byte at a time and with random walk, it's not cache friendly and
should be slower than a double copy. However, it's only used in
extreme situations and the difference will not be noticeable.

It has been extensively tested and works reliably.