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ash.c: speedup ${s:} substring (no quotes)

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This trivial patch makes ${s:...} at least as fast as ${s#??..}
in simple tests. It's probably faster for longer substrings,
but then one wouldn't use ${s#"1024???s"} anyway -
one would switch away from sh.

function                                             old     new   delta
subevalvar                                          1457    1503     +46

Signed-off-by: Alin Mr <almr.oss@outlook.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Alin Mr 2021-07-28 11:40:01 +03:00 committed by Denys Vlasenko
parent 94eb1c4dc6
commit 21e8dbfd9d
1 changed files with 11 additions and 6 deletions
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13
shell/ash.c
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@ -7185,15 +7185,20 @@ subevalvar(char *start, char *str, int strloc,
if ((unsigned)len > (orig_len - pos))
len = orig_len - pos;
for (vstr = startp; pos; vstr++, pos--) {
if (quotes && (unsigned char)*vstr == CTLESC)
if (!quotes) {
loc = mempcpy(startp, startp + pos, len);
} else {
for (vstr = startp; pos != 0; pos--) {
if ((unsigned char)*vstr == CTLESC)
vstr++;
vstr++;
}
for (loc = startp; len; len--) {
if (quotes && (unsigned char)*vstr == CTLESC)
for (loc = startp; len != 0; len--) {
if ((unsigned char)*vstr == CTLESC)
*loc++ = *vstr++;
*loc++ = *vstr++;
}
}
*loc = '\0';
goto out;
}