Add Chrono.h - std::chrono support header

Summary:
std::chrono mostly covers the functionality of llvm::sys::TimeValue and
lldb_private::TimeValue. This header adds a bit of utility functions and
typedefs, which make the usage of the library and porting code from TimeValues
easier.

Rationale:
- TimePoint typedef - precision of system_clock is implementation defined -
  using a well-defined precision helps maintain consistency between platforms,
  makes it interact better with existing TimeValue classes, and avoids cases
  there a time point is implicitly convertible to a specific precision on some
  platforms but not on others.
- system_clock::to_time_t only accepts time_points with the default system
  precision (even though time_t has only second precision on all platforms we
  support). To avoid the need for explicit casts, I have added a toTimeT()
  wrapper function. toTimePoint(time_t) was not strictly necessary, but I have
  added it for symmetry.

Reviewers: zturner, mehdi_amini

Subscribers: beanz, mgorny, llvm-commits, modocache

Differential Revision: https://reviews.llvm.org/D25416

llvm-svn: 284590

1 files changed, 79 insertions, 0 deletions

diff --git a/llvm/unittests/Support/Chrono.cpp b/llvm/unittests/Support/Chrono.cpp
new file mode 100644
index 00000000000..3d578780756
--- /dev/null
+++ b/llvm/unittests/Support/Chrono.cpp
@@ -0,0 +1,79 @@
+//===- llvm/unittest/Support/Chrono.cpp - Time utilities tests ------------===//
+//
+//           The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/Chrono.h"
+#include "llvm/ADT/SmallVector.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+using namespace llvm::sys;
+using namespace std::chrono;
+
+namespace {
+
+TEST(Chrono, TimeTConversion) {
+  EXPECT_EQ(time_t(0), toTimeT(toTimePoint(time_t(0))));
+  EXPECT_EQ(time_t(1), toTimeT(toTimePoint(time_t(1))));
+  EXPECT_EQ(time_t(47), toTimeT(toTimePoint(time_t(47))));
+
+  TimePoint<> TP;
+  EXPECT_EQ(TP, toTimePoint(toTimeT(TP)));
+  TP += seconds(1);
+  EXPECT_EQ(TP, toTimePoint(toTimeT(TP)));
+  TP += hours(47);
+  EXPECT_EQ(TP, toTimePoint(toTimeT(TP)));
+}
+
+TEST(Chrono, StringConversion) {
+  std::string S;
+  raw_string_ostream OS(S);
+  OS << system_clock::now();
+
+  // Do a basic sanity check on the output.
+  // The format we expect is YYYY-MM-DD HH:MM:SS.MMMUUUNNN
+  StringRef Date, Time;
+  std::tie(Date, Time) = StringRef(OS.str()).split(' ');
+
+  SmallVector<StringRef, 3> Components;
+  Date.split(Components, '-');
+  ASSERT_EQ(3u, Components.size());
+  EXPECT_EQ(4u, Components[0].size());
+  EXPECT_EQ(2u, Components[1].size());
+  EXPECT_EQ(2u, Components[2].size());
+
+  StringRef Sec, Nano;
+  std::tie(Sec, Nano) = Time.split('.');
+
+  Components.clear();
+  Sec.split(Components, ':');
+  ASSERT_EQ(3u, Components.size());
+  EXPECT_EQ(2u, Components[0].size());
+  EXPECT_EQ(2u, Components[1].size());
+  EXPECT_EQ(2u, Components[2].size());
+  EXPECT_EQ(9u, Nano.size());
+}
+
+// Test that toTimePoint and toTimeT can be called with a arguments with varying
+// precisions.
+TEST(Chrono, ImplicitConversions) {
+  std::time_t TimeT = 47;
+  TimePoint<seconds> Sec = toTimePoint(TimeT);
+  TimePoint<milliseconds> Milli = toTimePoint(TimeT);
+  TimePoint<microseconds> Micro = toTimePoint(TimeT);
+  TimePoint<nanoseconds> Nano = toTimePoint(TimeT);
+  EXPECT_EQ(Sec, Milli);
+  EXPECT_EQ(Sec, Micro);
+  EXPECT_EQ(Sec, Nano);
+  EXPECT_EQ(TimeT, toTimeT(Sec));
+  EXPECT_EQ(TimeT, toTimeT(Milli));
+  EXPECT_EQ(TimeT, toTimeT(Micro));
+  EXPECT_EQ(TimeT, toTimeT(Nano));
+}
+
+} // anonymous namespace