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vi: add comments to Rob's algorithm of reading and matching ESC sequences

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(nice work btw!)
This commit is contained in:
Denis Vlasenko 2008-10-14 10:09:56 +00:00
parent 5e38cd910a
commit 5373fbcd11
1 changed files with 33 additions and 23 deletions
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56
editors/vi.c
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@ -2243,60 +2243,70 @@ static char readit(void) // read (maybe cursor) key from stdin
fflush(stdout);
// If no data, block waiting for input.
n = chars_to_parse;
while (!n) {
if (n == 0) {
// If no data, block waiting for input.
n = safe_read(0, readbuffer, 1);
if (n <= 0) {
error:
place_cursor(rows - 1, 0, FALSE); // go to bottom of screen
clear_to_eol(); // erase to end of line
cookmode(); // terminal to "cooked"
bb_error_msg_and_die("can't read user input");
}
// Returning NUL from this routine would be bad.
if (*readbuffer) break;
}
// Grab character to return from buffer
c = *readbuffer;
c = readbuffer[0];
// Returning NUL from this routine would be bad.
if (c == '\0')
c = ' ';
n--;
if (n) memmove(readbuffer, readbuffer+1, n);
if (n) memmove(readbuffer, readbuffer + 1, n);
// If it's an escape sequence, loop through known matches.
if (c == 27) {
const struct esc_cmds *eindex;
for (eindex = esccmds; eindex < esccmds+ARRAY_SIZE(esccmds); eindex++) {
int i=0, cnt = strnlen(eindex->seq, 4);
for (eindex = esccmds; eindex < esccmds + ARRAY_SIZE(esccmds); eindex++) {
// n - position in seq to read
int i = 0; // position in seq to compare
int cnt = strnlen(eindex->seq, 4);
// Loop through chars in this sequence.
for (;;) {
// If we've matched this escape sequence so far but need more
// chars, read another as long as it wouldn't block. (Note that
// escape sequences come in as a unit, so if we would block
// it's not really an escape sequence.)
// We've matched this escape sequence up to [i-1]
if (n <= i) {
// Need more chars, read another one if it wouldn't block.
// (Note that escape sequences come in as a unit,
// so if we would block it's not really an escape sequence.)
struct pollfd pfd;
pfd.fd = 0;
pfd.events = POLLIN;
if (0 < safe_poll(&pfd, 1, 300)
&& 0 < safe_read(0, readbuffer + n, 1))
n++;
// Since the array is sorted from shortest to longest, if
// we needed more data we can't match anything later, so
// break out of both loops.
else goto loop_out;
// TODO: what is a good timeout here? why?
if (safe_poll(&pfd, 1, /*timeout:*/ 0)) {
if (safe_read(0, readbuffer + n, 1) <= 0)
goto error;
n++;
} else {
// No more data!
// Array is sorted from shortest to longest,
// we can't match anything later in array,
// break out of both loops.
goto loop_out;
}
}
if (readbuffer[i] != eindex->seq[i]) break;
if (++i == cnt) {
if (readbuffer[i] != eindex->seq[i])
break; // try next seq
if (++i == cnt) { // entire seq matched
c = eindex->val;
n = 0;
goto loop_out;
}
}
}
// We did not find matching sequence, it was a bare ESC.
// We possibly read and stored more input in readbuffer by now.
}
loop_out: