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authorRob Landley <rob@landley.net>2020-12-12 05:53:16 -0600
committerRob Landley <rob@landley.net>2020-12-12 05:53:16 -0600
commit769b8a1c42a1c44fec930795fd3ce8799ec39537 (patch)
tree6bcce118c15233b963e6edd95ecb9a964926a8ea
parent67476b1b3d9462c0fddb4b95c173dc76ea1c933c (diff)
downloadtoybox-769b8a1c42a1c44fec930795fd3ce8799ec39537.tar.gz
Speed up seq: use toybuf for block writes and add an integer fast path.
-rwxr-xr-xtests/seq.test2
-rw-r--r--toys/lsb/seq.c88
2 files changed, 65 insertions, 25 deletions
diff --git a/tests/seq.test b/tests/seq.test
index 15a208bb..4284617d 100755
--- a/tests/seq.test
+++ b/tests/seq.test
@@ -69,3 +69,5 @@ testing "invalid increment" "seq 1 1f 1 2>/dev/null || echo y" "y\n" "" ""
# TODO: busybox fails this too, but GNU seems to not use double for large ints.
#testing "too large for double" "seq -s, 9007199254740991 1 9007199254740992" "9007199254740992\n" "" ""
+
+testing "fast path" "timeout 10 seq 10000000 > /dev/null" "" "" ""
diff --git a/toys/lsb/seq.c b/toys/lsb/seq.c
index 988466b7..45c82d51 100644
--- a/toys/lsb/seq.c
+++ b/toys/lsb/seq.c
@@ -28,7 +28,7 @@ config SEQ
GLOBALS(
char *s, *f;
- int precision;
+ int precision, buflen;
)
// Ensure there's one %f escape with correct attributes
@@ -37,10 +37,8 @@ static void insanitize(char *f)
char *s = next_printf(f, 0);
if (!s) error_exit("bad -f no %%f");
- if (-1 == stridx("aAeEfFgG", *s) || (s = next_printf(s, 0))) {
- // The @ is a byte offset, not utf8 chars. Waiting for somebody to complain.
+ if (-1 == stridx("aAeEfFgG", *s) || (s = next_printf(s, 0)))
error_exit("bad -f '%s'@%d", f, (int)(s-f+1));
- }
}
// Parse a numeric argument setting *prec to the precision of this argument.
@@ -54,11 +52,38 @@ static double parsef(char *s)
return xstrtod(s);
}
+// fast integer conversion to decimal string
+char *itoa(char *s, int i)
+{
+ char buf[16], *ff = buf;
+
+ if (i<0) {
+ *s++ = '-';
+ i = -i;
+ }
+ do *ff++ = '0'+i%10; while ((i /= 10));
+ do *s++ = *--ff; while (ff>buf);
+ *s++ = '\n';
+
+ return s;
+}
+
+char *flush_toybuf(char *ss)
+{
+ if (ss-toybuf<TT.buflen) return ss;
+
+ xwrite(1, toybuf, ss-toybuf);
+
+ return toybuf;
+}
+
void seq_main(void)
{
+ char fbuf[32], *ss;
double first = 1, increment = 1, last, dd;
- int i;
+ int ii, inc = 1, len, slen;
+ // parse arguments
if (!TT.s) TT.s = "\n";
switch (toys.optc) {
case 3: increment = parsef(toys.optargs[1]);
@@ -66,19 +91,32 @@ void seq_main(void)
default: last = parsef(toys.optargs[toys.optc-1]);
}
- // Prepare format string with appropriate precision. Can't use %g because 1e6
- if (toys.optflags & FLAG_f) insanitize(TT.f);
- else sprintf(TT.f = toybuf, "%%.%df", TT.precision);
-
- // Pad to largest width
- if (toys.optflags & FLAG_w) {
- int len = 0;
-
- for (i=0; i<3; i++) {
- dd = (double []){first, increment, last}[i];
- len = maxof(len, snprintf(0, 0, TT.f, dd));
- }
- sprintf(TT.f = toybuf, "%%0%d.%df", len, TT.precision);
+ // measure arguments
+ if (FLAG(f)) insanitize(TT.f);
+ for (ii = len = 0; ii<3; ii++) {
+ dd = (double []){first, increment, last}[ii];
+ len = maxof(len, snprintf(0, 0, "%.*f", TT.precision, fabs(dd)));
+ if (ii == 2) dd += increment;
+ slen = dd;
+ if (dd != slen) inc = 0;
+ }
+ if (!FLAG(f)) sprintf(TT.f = fbuf, "%%0%d.%df", len, TT.precision);
+ TT.buflen = sizeof(toybuf) - 32 - len - TT.precision - strlen(TT.s);
+ if (TT.buflen<0) error_exit("bad -s");
+
+ // fast path: when everything fits in an int with no flags.
+ if (!toys.optflags && inc) {
+ ii = first;
+ len = last;
+ inc = increment;
+ ss = toybuf;
+ if (inc>0) for (; ii<=len; ii += inc)
+ ss = flush_toybuf(itoa(ss, ii));
+ else if (inc<0) for (; ii>=len; ii += inc)
+ ss = flush_toybuf(itoa(ss, ii));
+ if (ss != toybuf) write(1, toybuf, ss-toybuf);
+
+ return;
}
// Other implementations output nothing if increment is 0 and first > last,
@@ -86,14 +124,14 @@ void seq_main(void)
// nothing for all three, if you want endless output use "yes".
if (!increment) return;
- i = 0;
- for (;;) {
+ // Slow path, floating point and fancy sprintf() patterns
+ for (ii = 0, ss = toybuf;; ii++) {
// Multiply to avoid accumulating rounding errors from increment.
- dd = first+i*increment;
+ dd = first+ii*increment;
if ((increment<0 && dd<last) || (increment>0 && dd>last)) break;
- if (i++) printf("%s", TT.s);
- printf(TT.f, dd);
+ if (ii) ss = flush_toybuf(stpcpy(ss, TT.s));
+ ss += sprintf(ss, TT.f, dd);
}
-
- if (i) printf("\n");
+ *ss++ = '\n';
+ xwrite(1, toybuf, ss-toybuf);
}