Merge "strftime: format small positive integers ourselves." am: ad12582726
Original change: https://android-review.googlesource.com/c/platform/bionic/+/1897133
Change-Id: I3dab64aa9f5f94b17399b4a08d81ae847473a43a
diff --git a/benchmarks/time_benchmark.cpp b/benchmarks/time_benchmark.cpp
index 437dc78..a765e3e 100644
--- a/benchmarks/time_benchmark.cpp
+++ b/benchmarks/time_benchmark.cpp
@@ -187,3 +187,13 @@
}
}
BIONIC_BENCHMARK(BM_time_localtime_r);
+
+void BM_time_strftime(benchmark::State& state) {
+ char buf[128];
+ time_t t = 0;
+ struct tm* tm = gmtime(&t);
+ while (state.KeepRunning()) {
+ strftime(buf, sizeof(buf), "%Y-%m-%d %H:%M:%S", tm);
+ }
+}
+BIONIC_BENCHMARK(BM_time_strftime);
diff --git a/libc/tzcode/strftime.c b/libc/tzcode/strftime.c
index c05f6b5..7c4be49 100644
--- a/libc/tzcode/strftime.c
+++ b/libc/tzcode/strftime.c
@@ -252,8 +252,8 @@
pt = _fmt("%m/%d/%y", t, pt, ptlim, warnp);
continue;
case 'd':
- pt = _conv(t->tm_mday, getformat(modifier, "%02d", "%2d", "%d", "%02d"), pt, ptlim);
- continue;
+ pt = _conv(t->tm_mday, getformat(modifier, "02", " 2", " ", "02"), pt, ptlim);
+ continue;
case 'E':
case 'O':
/*
@@ -274,22 +274,21 @@
modifier = *format;
goto label;
case 'e':
- pt = _conv(t->tm_mday, getformat(modifier, "%2d", "%2d", "%d", "%02d"), pt, ptlim);
- continue;
+ pt = _conv(t->tm_mday, getformat(modifier, " 2", " 2", " ", "02"), pt, ptlim);
+ continue;
case 'F':
pt = _fmt("%Y-%m-%d", t, pt, ptlim, warnp);
continue;
case 'H':
- pt = _conv(t->tm_hour, getformat(modifier, "%02d", "%2d", "%d", "%02d"), pt, ptlim);
- continue;
+ pt = _conv(t->tm_hour, getformat(modifier, "02", " 2", " ", "02"), pt, ptlim);
+ continue;
case 'I':
- pt = _conv((t->tm_hour % 12) ?
- (t->tm_hour % 12) : 12,
- getformat(modifier, "%02d", "%2d", "%d", "%02d"), pt, ptlim);
- continue;
+ pt = _conv((t->tm_hour % 12) ? (t->tm_hour % 12) : 12,
+ getformat(modifier, "02", " 2", " ", "02"), pt, ptlim);
+ continue;
case 'j':
- pt = _conv(t->tm_yday + 1, getformat(modifier, "%03d", "%3d", "%d", "%03d"), pt, ptlim);
- continue;
+ pt = _conv(t->tm_yday + 1, getformat(modifier, "03", " 3", " ", "03"), pt, ptlim);
+ continue;
case 'k':
/*
** This used to be...
@@ -301,7 +300,7 @@
** "%l" have been swapped.
** (ado, 1993-05-24)
*/
- pt = _conv(t->tm_hour, getformat(modifier, "%2d", "%2d", "%d", "%02d"), pt, ptlim);
+ pt = _conv(t->tm_hour, getformat(modifier, " 2", " 2", " ", "02"), pt, ptlim);
continue;
#ifdef KITCHEN_SINK
case 'K':
@@ -321,16 +320,15 @@
** "%l" have been swapped.
** (ado, 1993-05-24)
*/
- pt = _conv((t->tm_hour % 12) ?
- (t->tm_hour % 12) : 12,
- getformat(modifier, "%2d", "%2d", "%d", "%02d"), pt, ptlim);
+ pt = _conv((t->tm_hour % 12) ? (t->tm_hour % 12) : 12,
+ getformat(modifier, " 2", " 2", " ", "02"), pt, ptlim);
continue;
case 'M':
- pt = _conv(t->tm_min, getformat(modifier, "%02d", "%2d", "%d", "%02d"), pt, ptlim);
- continue;
+ pt = _conv(t->tm_min, getformat(modifier, "02", " 2", " ", "02"), pt, ptlim);
+ continue;
case 'm':
- pt = _conv(t->tm_mon + 1, getformat(modifier, "%02d", "%2d", "%d", "%02d"), pt, ptlim);
- continue;
+ pt = _conv(t->tm_mon + 1, getformat(modifier, "02", " 2", " ", "02"), pt, ptlim);
+ continue;
case 'n':
pt = _add("\n", pt, ptlim, modifier);
continue;
@@ -348,13 +346,12 @@
pt = _fmt("%I:%M:%S %p", t, pt, ptlim, warnp);
continue;
case 'S':
- pt = _conv(t->tm_sec, getformat(modifier, "%02d", "%2d", "%d", "%02d"), pt, ptlim);
- continue;
+ pt = _conv(t->tm_sec, getformat(modifier, "02", " 2", " ", "02"), pt, ptlim);
+ continue;
case 's':
{
struct tm tm;
- char buf[INT_STRLEN_MAXIMUM(
- time64_t) + 1];
+ char buf[INT_STRLEN_MAXIMUM(time64_t) + 1] __attribute__((__uninitialized__));
time64_t mkt;
tm = *t;
@@ -374,10 +371,9 @@
pt = _add("\t", pt, ptlim, modifier);
continue;
case 'U':
- pt = _conv((t->tm_yday + DAYSPERWEEK -
- t->tm_wday) / DAYSPERWEEK,
- getformat(modifier, "%02d", "%2d", "%d", "%02d"), pt, ptlim);
- continue;
+ pt = _conv((t->tm_yday + DAYSPERWEEK - t->tm_wday) / DAYSPERWEEK,
+ getformat(modifier, "02", " 2", " ", "02"), pt, ptlim);
+ continue;
case 'u':
/*
** From Arnold Robbins' strftime version 3.0:
@@ -385,9 +381,7 @@
** [1 (Monday) - 7]"
** (ado, 1993-05-24)
*/
- pt = _conv((t->tm_wday == 0) ?
- DAYSPERWEEK : t->tm_wday,
- "%d", pt, ptlim);
+ pt = _conv((t->tm_wday == 0) ? DAYSPERWEEK : t->tm_wday, " ", pt, ptlim);
continue;
case 'V': /* ISO 8601 week number */
case 'G': /* ISO 8601 year (four digits) */
@@ -467,8 +461,7 @@
w = 53;
#endif /* defined XPG4_1994_04_09 */
if (*format == 'V')
- pt = _conv(w, getformat(modifier, "%02d", "%2d", "%d", "%02d"),
- pt, ptlim);
+ pt = _conv(w, getformat(modifier, "02", " 2", " ", "02"), pt, ptlim);
else if (*format == 'g') {
*warnp = IN_ALL;
pt = _yconv(year, base,
@@ -488,15 +481,14 @@
pt = _fmt("%e-%b-%Y", t, pt, ptlim, warnp);
continue;
case 'W':
- pt = _conv((t->tm_yday + DAYSPERWEEK -
- (t->tm_wday ?
- (t->tm_wday - 1) :
- (DAYSPERWEEK - 1))) / DAYSPERWEEK,
- getformat(modifier, "%02d", "%2d", "%d", "%02d"), pt, ptlim);
- continue;
+ pt = _conv(
+ (t->tm_yday + DAYSPERWEEK - (t->tm_wday ? (t->tm_wday - 1) : (DAYSPERWEEK - 1))) /
+ DAYSPERWEEK,
+ getformat(modifier, "02", " 2", " ", "02"), pt, ptlim);
+ continue;
case 'w':
- pt = _conv(t->tm_wday, "%d", pt, ptlim);
- continue;
+ pt = _conv(t->tm_wday, " ", pt, ptlim);
+ continue;
case 'X':
pt = _fmt(Locale->X_fmt, t, pt, ptlim, warnp);
continue;
@@ -602,7 +594,7 @@
diff /= SECSPERMIN;
diff = (diff / MINSPERHOUR) * 100 +
(diff % MINSPERHOUR);
- pt = _conv(diff, getformat(modifier, "%04d", "%4d", "%d", "%04d"), pt, ptlim);
+ pt = _conv(diff, getformat(modifier, "04", " 4", " ", "04"), pt, ptlim);
}
continue;
case '+':
@@ -629,10 +621,40 @@
static char *
_conv(int n, const char *format, char *pt, const char *ptlim)
{
- char buf[INT_STRLEN_MAXIMUM(int) + 1];
+ // The original implementation used snprintf(3) here, but rolling our own is
+ // about 5x faster. Seems like a good trade-off for so little code, especially
+ // for users like logcat that have a habit of formatting 10k times all at
+ // once...
- snprintf(buf, sizeof(buf), format, n);
- return _add(buf, pt, ptlim, 0);
+ // Format is '0' or ' ' for the fill character, followed by a single-digit
+ // width or ' ' for "whatever".
+ // %d -> " "
+ // %2d -> " 2"
+ // %02d -> "02"
+ char fill = format[0];
+ int width = format[1] == ' ' ? 0 : format[1] - '0';
+
+ char buf[32] __attribute__((__uninitialized__));
+
+ // Terminate first, so we can walk backwards from the least-significant digit
+ // without having to later reverse the result.
+ char* p = &buf[31];
+ *--p = '\0';
+ char* end = p;
+
+ // Output digits backwards, from least-significant to most.
+ while (n >= 10) {
+ *--p = '0' + (n % 10);
+ n /= 10;
+ }
+ *--p = '0' + n;
+
+ // Fill if more digits are required by the format.
+ while ((end - p) < width) {
+ *--p = fill;
+ }
+
+ return _add(p, pt, ptlim, 0);
}
static char *
@@ -704,9 +726,11 @@
if (convert_top) {
if (lead == 0 && trail < 0)
pt = _add("-0", pt, ptlim, modifier);
- else pt = _conv(lead, getformat(modifier, "%02d", "%2d", "%d", "%02d"), pt, ptlim);
+ else
+ pt = _conv(lead, getformat(modifier, "02", " 2", " ", "02"), pt, ptlim);
}
if (convert_yy)
- pt = _conv(((trail < 0) ? -trail : trail), getformat(modifier, "%02d", "%2d", "%d", "%02d"), pt, ptlim);
+ pt = _conv(((trail < 0) ? -trail : trail), getformat(modifier, "02", " 2", " ", "02"), pt,
+ ptlim);
return pt;
}