From: jnc@mercury.lcs.mit.edu (Noel Chiappa)
Subject: stty erase '^?' in v7
Date: Sun, 15 Oct 2017 10:39:54 -0400 (EDT) [thread overview]
Message-ID: <20171015143954.C507218C0BB@mercury.lcs.mit.edu> (raw)
> From: Will Senn
> All that cooked and raw stuff is gobbledegook that I'll have to read up
> on.
The raw/cooked stuff isn't the source of the worst hair in the TTY driver;
that would be delays (on the output side), and delimiter processing (on the
input side).
The delays are for mechanical terminals, because they need delays after a
motion command (e.g. NL, CR, etc) before the next printing character is sent;
differing for different motion control commands, further complexified by the
current print head position - a Carriage Return from column 70 taking a lot
longer than one from column 10. The driver keeps track of the current column,
so it can calculate this! It does the delays by putting in the output queue a
chacter with the high bit set, and the delay in the low bits; the output start
routine looks for these, and does the delay.
On the input side, every time it sees a delimiter (NL, EOF), it inserts a 0xFF
byte in the input queue, and increments a counter to keep track of how many it
has inserted. I _think_ this is so that any given read call on a 'cooked'
terminal will return at most one line of input (although I don't know why they
don't just parse the buffer contents at read time - although I guess they need
the delimiter count so the read call will wait if there is not a complete line
there yet).
I should look and see how the MIT TTY driver (which also supported 8-bit input
and output) dealt with these...
Noel
next reply other threads:[~2017-10-15 14:39 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-15 14:39 Noel Chiappa [this message]
-- strict thread matches above, loose matches on Subject: below --
2017-10-14 12:52 Noel Chiappa
2017-10-14 14:40 ` Clem Cole
2017-10-14 14:44 ` Ronald Natalie
2017-10-15 13:10 ` Don Hopkins
2017-10-14 4:25 Noel Chiappa
2017-10-14 4:48 ` Will Senn
2017-10-14 6:31 ` Dave Horsfall
2017-10-14 14:03 ` Will Senn
2017-10-14 22:01 ` Dave Horsfall
2017-10-14 2:59 Will Senn
2017-10-14 4:08 ` Grant Taylor
2017-10-14 4:39 ` Random832
2017-10-14 5:03 ` Will Senn
2017-10-16 14:46 ` Random832
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