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- /*
- * Copyright 2016-present Facebook, Inc.
- *
- * 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 <folly/ClockGettimeWrappers.h>
- #include <folly/Likely.h>
- #include <folly/portability/Time.h>
- #include <chrono>
- #include <time.h>
- #ifndef _WIN32
- #define _GNU_SOURCE 1
- #include <dlfcn.h>
- #endif
- namespace folly {
- namespace chrono {
- static int64_t clock_gettime_ns_fallback(clockid_t clock) {
- struct timespec ts;
- int r = clock_gettime(clock, &ts);
- if (UNLIKELY(r != 0)) {
- // Mimic what __clock_gettime_ns does (even though this can be a legit
- // value).
- return -1;
- }
- std::chrono::nanoseconds result =
- std::chrono::seconds(ts.tv_sec) + std::chrono::nanoseconds(ts.tv_nsec);
- return result.count();
- }
- // Initialize with default behavior, which we might override on Linux hosts
- // with VDSO support.
- int (*clock_gettime)(clockid_t, timespec* ts) = &::clock_gettime;
- int64_t (*clock_gettime_ns)(clockid_t) = &clock_gettime_ns_fallback;
- #ifdef FOLLY_HAVE_LINUX_VDSO
- namespace {
- struct VdsoInitializer {
- VdsoInitializer() {
- m_handle = dlopen("linux-vdso.so.1", RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
- if (!m_handle) {
- return;
- }
- void* p = dlsym(m_handle, "__vdso_clock_gettime");
- if (p) {
- folly::chrono::clock_gettime = (int (*)(clockid_t, timespec*))p;
- }
- p = dlsym(m_handle, "__vdso_clock_gettime_ns");
- if (p) {
- folly::chrono::clock_gettime_ns = (int64_t(*)(clockid_t))p;
- }
- }
- ~VdsoInitializer() {
- if (m_handle) {
- clock_gettime = &::clock_gettime;
- clock_gettime_ns = &clock_gettime_ns_fallback;
- dlclose(m_handle);
- }
- }
- private:
- void* m_handle;
- };
- static const VdsoInitializer vdso_initializer;
- } // namespace
- #endif
- } // namespace chrono
- } // namespace folly
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