On Thu, Jan 24 2019 13:58:04 +0200, Lauri Tirkkonen wrote:
> And even then I think the cost is negligible: getline grows
> the buffer in powers of 2, so only lines that happen to be twice as long
> as any previously encountered line pay the price.
Actually, I went to skim the fgetln() implementation and it might very
well be that fgetln() does *more* reallocations than getline. The
storage that fgetln() uses is hidden from the user, but obviously it has
to store its buffer somewhere. It's a member of struct FILE:
125 /* separate buffer for fgetln() when line crosses buffer
boundary */
126 struct __sbuf _lb; /* buffer for fgetln() */
and it is expanded by __slbexpand() in stdio/fgetln.c, which just does
recallocarray(). To me it looks like the buffer is either incremented by
OPTIMISTIC (#define'd to be 80 bytes), or again by exactly as much as is
required by the current line if that wasn't enough.
I haven't done any actual measurements though, so it's possible my
reading is wrong.
--
Lauri Tirkkonen | lotheac @ IRCnet
