commit 991008dc460854b5f2f978a87946f9d90e3e5ee5
parent e3461920b100b12eaaca9664ce161519966b58a9
Author: Hiltjo Posthuma <hiltjo@codemadness.org>
Date: Mon, 9 Mar 2020 19:16:52 +0100
sfeed_plain: optimize utf8-decoding and column position calculation
Optimize for the common-case: assuming ASCII.
The input is assumed to be valid UTF-8 input (output of sfeed).
This saves 2 function calls for determining the width of a single ASCII
character, which of course is 1.
Ranges:
< 32 are control-characters and are skipped.
< 127 is typical ASCII and is 1 column wide.
>= 127 is the normal path (control-character and multi-byte UTF-8).
Tested on OpenBSD and Linux with various compilers (clang, gcc, pcc and tcc).
On OpenBSD and Linux glibc much improvement. On Linux musl (almost) no change.
In a common-case upto 40% performance improvement.
In the worst-case negligible performance degration (<1%).
Diffstat:
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/util.c b/util.c
@@ -247,10 +247,15 @@ printutf8pad(FILE *fp, const char *s, size_t len, int pad)
slen = strlen(s);
for (i = 0; i < slen; i += rl) {
- if ((rl = mbtowc(&wc, s + i, slen - i < 4 ? slen - i : 4)) <= 0)
- break;
- if ((w = wcwidth(wc)) == -1)
+ rl = w = 1;
+ if ((unsigned char)s[i] < 32)
continue;
+ if ((unsigned char)s[i] >= 127) {
+ if ((rl = mbtowc(&wc, s + i, slen - i < 4 ? slen - i : 4)) <= 0)
+ break;
+ if ((w = wcwidth(wc)) == -1)
+ continue;
+ }
if (col + w > len || (col + w == len && s[i + rl])) {
fputs("\xe2\x80\xa6", fp);
col++;