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Stop using a local buffer in term_out.

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There's no actual need to copy the data from term->inbuf into a local
variable inside term_out(). We can simply store a pointer and length,
and use the data _in situ_ - as long as we remember how much of it
we've used, and bufchain_consume() it when the routine exits.

Getting rid of that awkward and size-limited local array should
marginally improve performance. But also, it opens up the possibility
to suddenly suspend handling of terminal data and leave everything not
yet processed in the bufchain, because now we never remove anything
from the bufchain until _after_ it's been processed, so there's no
need to awkwardly push the unused segment of localbuf[] back on to the
front of the bufchain if we need to do that.

NFC, but as usual, I have a plan to use the new capability in a
followup commit.
This commit is contained in:
Simon Tatham 2021-12-18 15:07:41 +00:00
parent 5a54b3bf17
commit be0cea7130
1 changed files with 31 additions and 17 deletions
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48
terminal/terminal.c
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@ -3626,8 +3626,8 @@ static void term_out(Terminal *term)
{
unsigned long c;
int unget;
unsigned char localbuf[256], *chars;
size_t nchars = 0;
const unsigned char *chars;
size_t nchars_got = 0, nchars_used = 0;
/*
* During drag-selects, we do not process terminal input, because
@ -3639,21 +3639,36 @@ static void term_out(Terminal *term)
unget = -1;
chars = NULL; /* placate compiler warnings */
while (nchars > 0 || unget != -1 || bufchain_size(&term->inbuf) > 0) {
if (unget == -1) {
if (nchars == 0) {
while (nchars_got < nchars_used ||
unget != -1 ||
bufchain_size(&term->inbuf) > 0) {
if (unget != -1) {
/*
* Handle a character we left in 'unget' the last time
* round this loop. This happens if a UTF-8 sequence is
* aborted early, by containing fewer continuation bytes
* than its introducer expected: the non-continuation byte
* that interrupted the sequence must now be processed
* as a fresh piece of input in its own right.
*/
c = unget;
unget = -1;
} else {
if (nchars_got == nchars_used) {
/* Delete the previous chunk from the bufchain */
bufchain_consume(&term->inbuf, nchars_used);
nchars_used = 0;
if (bufchain_size(&term->inbuf) == 0)
break; /* no more data */
ptrlen data = bufchain_prefix(&term->inbuf);
if (data.len > sizeof(localbuf))
data.len = sizeof(localbuf);
memcpy(localbuf, data.ptr, data.len);
bufchain_consume(&term->inbuf, data.len);
nchars = data.len;
chars = localbuf;
chars = data.ptr;
nchars_got = data.len;
assert(chars != NULL);
assert(nchars > 0);
assert(nchars_used < nchars_got);
}
c = *chars++;
nchars--;
c = chars[nchars_used++];
/*
* Optionally log the session traffic to a file. Useful for
@ -3661,9 +3676,6 @@ static void term_out(Terminal *term)
*/
if (term->logtype == LGTYP_DEBUG && term->logctx)
logtraffic(term->logctx, (unsigned char) c, LGTYP_DEBUG);
} else {
c = unget;
unget = -1;
}
/* Note only VT220+ are 8-bit VT102 is seven bit, it shouldn't even
@ -5535,6 +5547,8 @@ static void term_out(Terminal *term)
}
}
bufchain_consume(&term->inbuf, nchars_used);
term_print_flush(term);
if (term->logflush && term->logctx)
logflush(term->logctx);