2 Jan
2015
2 Jan
'15
7:50 a.m.
Quoting Warner Losh <imp(a)bsdimp.com>:
BSD solved this problem that way: parse /etc/termcap and put all the
entries into termcap.db. :)
That's essentially what terminfo's binary files are: a parsed, cached
version of the source.
But the big motivator was performance. Reading
in a termcap entry from
/etc/termcap was terribly slow. First you had to scan all the way
through the (ever-growing) termcap file to find the correct entry. Once
you had it, every tgetstr (etc) had to scan from the beginning of the
entry, so starting up a program like vi involved quadratic performance
(time grew as the square of the length of the termcap entry.) The VAX
11/780 was a 1 MIPS processor (about the same as a 1 MHz Pentium) and
was shared among dozens of timesharing users, and some of the other
machines of the day (750 and 730 Vaxen, PDP-11, etc.) were even slower.
It took forever to start up vi or more or any of the termcap-based
programs people were using a lot.
Hum. That seems like it would be more of an implementation issue.
Why wouldn't you just cache all the entries for the terminal once
and for all? terminfo never came to 16-bit systems anyway, so we're
talking about systems with plenty of memory. Caching the terminal
information would not be a big memory cost.