Cache the most-recently used timezone for mktime_tz and localtime_tz.
Normally, the C library implicitly caches your timezone by virtue
of the fact that the prehistoric API assumes a single timezone for
the entire process.
The unfortunate mktime_tz and localtime_tz extensions work around
this, but represent timezones as strings to their callers, so code
that makes heavy use of these needs a cache to be able to perform
acceptably until it can hopefully one day be rewritten to use
java.util.Calendar or icu4c.
Bug: 8270865
Change-Id: I92e3964e86dc33ceac925f819cc5e26ff4203f50
diff --git a/libc/tzcode/localtime.c b/libc/tzcode/localtime.c
index 447907e..689bbd3 100644
--- a/libc/tzcode/localtime.c
+++ b/libc/tzcode/localtime.c
@@ -404,10 +404,7 @@
}
static int
-tzload(name, sp, doextend)
-register const char * name;
-register struct state * const sp;
-register const int doextend;
+tzload(const char* name, struct state* const sp, const int doextend)
{
register const char * p;
register int i;
@@ -2068,32 +2065,55 @@
}
// BEGIN android-added
-time_t
-mktime_tz(tmp, tz)
-struct tm * const tmp;
-char const * tz;
-{
- struct state st;
- if (tzload(tz, &st, TRUE) != 0) {
- // TODO: not sure what's best here, but for now, we fall back to gmt.
- gmtload(&st);
- }
- return time1(tmp, localsub, 0L, &st);
+
+// Caches the most recent timezone (http://b/8270865).
+static int __bionic_tzload_cached(const char* name, struct state* const sp, const int doextend) {
+ _tzLock();
+
+ // Our single-item cache.
+ static char* gCachedTimeZoneName;
+ static struct state gCachedTimeZone;
+
+ // Do we already have this timezone cached?
+ if (gCachedTimeZoneName != NULL && strcmp(name, gCachedTimeZoneName) == 0) {
+ *sp = gCachedTimeZone;
+ _tzUnlock();
+ return 0;
+ }
+
+ // Can we load it?
+ int rc = tzload(name, sp, doextend);
+ if (rc == 0) {
+ // Update the cache.
+ free(gCachedTimeZoneName);
+ gCachedTimeZoneName = strdup(name);
+ gCachedTimeZone = *sp;
+ }
+
+ _tzUnlock();
+ return rc;
}
-void
-localtime_tz(timep, tmp, tz)
-const time_t * const timep;
-struct tm * tmp;
-const char* tz;
-{
- struct state st;
- if (tzload(tz, &st, TRUE) != 0) {
- // TODO: not sure what's best here, but for now, we fall back to gmt.
- gmtload(&st);
- }
- localsub(timep, 0L, tmp, &st);
+// Non-standard API: mktime(3) but with an explicit timezone parameter.
+time_t mktime_tz(struct tm* const tmp, const char* tz) {
+ struct state st;
+ if (__bionic_tzload_cached(tz, &st, TRUE) != 0) {
+ // TODO: not sure what's best here, but for now, we fall back to gmt.
+ gmtload(&st);
+ }
+ return time1(tmp, localsub, 0L, &st);
}
+
+// Non-standard API: localtime(3) but with an explicit timezone parameter.
+void localtime_tz(const time_t* const timep, struct tm* tmp, const char* tz) {
+ struct state st;
+ if (__bionic_tzload_cached(tz, &st, TRUE) != 0) {
+ // TODO: not sure what's best here, but for now, we fall back to gmt.
+ gmtload(&st);
+ }
+ localsub(timep, 0L, tmp, &st);
+}
+
// END android-added
#ifdef STD_INSPIRED
diff --git a/tests/Android.mk b/tests/Android.mk
index 1e4ef59..633a6a9 100644
--- a/tests/Android.mk
+++ b/tests/Android.mk
@@ -32,6 +32,7 @@
benchmark_main.cpp \
math_benchmark.cpp \
string_benchmark.cpp \
+ time_benchmark.cpp \
# Build benchmarks for the device (with bionic's .so). Run with:
# adb shell bionic-benchmarks
diff --git a/tests/time_benchmark.cpp b/tests/time_benchmark.cpp
new file mode 100644
index 0000000..75132e5
--- /dev/null
+++ b/tests/time_benchmark.cpp
@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "benchmark.h"
+
+#include <time.h>
+
+#if defined(__BIONIC__)
+
+// Used by the horrible android.text.format.Time class, which is used by Calendar. http://b/8270865.
+extern "C" void localtime_tz(const time_t* const timep, struct tm* tmp, const char* tz);
+
+static void BM_time_localtime_tz(int iters) {
+ StartBenchmarkTiming();
+
+ time_t now(time(NULL));
+ tm broken_down_time;
+ for (int i = 0; i < iters; ++i) {
+ localtime_tz(&now, &broken_down_time, "Europe/Berlin");
+ }
+
+ StopBenchmarkTiming();
+}
+BENCHMARK(BM_time_localtime_tz);
+#endif
