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

2 files changed, 39 insertions, 0 deletions

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_src_files = \
     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