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

include/llvm/Support/Chrono.h

@@ -0,0 +1,55 @@
+//===- llvm/Support/Chrono.h - Utilities for Timing Manipulation-*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_CHRONO_H
+#define LLVM_SUPPORT_CHRONO_H
+
+#include "llvm/Support/Compiler.h"
+
+#include <chrono>
+#include <ctime>
+
+namespace llvm {
+
+class raw_ostream;
+
+namespace sys {
+
+/// A time point on the system clock. This is provided for two reasons:
+/// - to insulate us agains subtle differences in behavoir to differences in
+///   system clock precision (which is implementation-defined and differs between
+///   platforms).
+/// - to shorten the type name
+/// The default precision is nanoseconds. If need a specific precision specify
+/// it explicitly. If unsure, use the default. If you need a time point on a
+/// clock other than the system_clock, use std::chrono directly.
+template <typename D = std::chrono::nanoseconds>
+using TimePoint = std::chrono::time_point<std::chrono::system_clock, D>;
+
+/// Convert a TimePoint to std::time_t
+LLVM_ATTRIBUTE_ALWAYS_INLINE inline std::time_t toTimeT(TimePoint<> TP) {
+  using namespace std::chrono;
+  return system_clock::to_time_t(
+      time_point_cast<system_clock::time_point::duration>(TP));
+}
+
+/// Convert a std::time_t to a TimePoint
+LLVM_ATTRIBUTE_ALWAYS_INLINE inline TimePoint<std::chrono::seconds>
+toTimePoint(std::time_t T) {
+  using namespace std::chrono;
+  return time_point_cast<seconds>(system_clock::from_time_t(T));
+}
+
+} // namespace sys
+
+raw_ostream &operator<<(raw_ostream &OS, sys::TimePoint<> TP);
+
+} // namespace llvm
+
+#endif // LLVM_SUPPORT_CHRONO_H

include/llvm/Support/TimeValue.h

@@ -14,6 +14,7 @@
 #ifndef LLVM_SUPPORT_TIMEVALUE_H
 #define LLVM_SUPPORT_TIMEVALUE_H
 
+#include "llvm/Support/Chrono.h"
 #include "llvm/Support/DataTypes.h"
 #include <string>
 
@@ -112,6 +113,11 @@ namespace sys {
       this->normalize();
     }
 
+    template<typename D>
+    TimeValue(TimePoint<D> TP)
+        : seconds_(sys::toTimeT(TP) + PosixZeroTimeSeconds),
+          nanos_((TimePoint<>(TP).time_since_epoch() % std::chrono::seconds(1)).count()) {}
+
     /// This is a static constructor that returns a TimeValue that represents
     /// the current time.
     /// @brief Creates a TimeValue with the current time (UTC).
@@ -121,6 +127,11 @@ namespace sys {
   /// @name Operators
   /// @{
   public:
+    operator TimePoint<>() const {
+      return toTimePoint(seconds_ - PosixZeroTimeSeconds) +
+             std::chrono::nanoseconds(nanos_);
+    }
+
     /// Add \p that to \p this.
     /// @returns this
     /// @brief Incrementing assignment operator.

lib/Support/CMakeLists.txt

@@ -37,6 +37,7 @@ add_llvm_library(LLVMSupport
   BranchProbability.cpp
   CachePruning.cpp
   circular_raw_ostream.cpp
+  Chrono.cpp
   COM.cpp
   CommandLine.cpp
   Compression.cpp

lib/Support/Chrono.cpp

@@ -0,0 +1,47 @@
+//===- Support/Chrono.cpp - Utilities for Timing Manipulation ---*- C++ -*-===//
+//
+//                     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/Config/config.h"
+#include "llvm/Support/Format.h"
+#include "llvm/Support/raw_ostream.h"
+
+namespace llvm {
+
+using namespace sys;
+
+static inline struct tm getStructTM(TimePoint<> TP) {
+  struct tm Storage;
+  std::time_t OurTime = toTimeT(TP);
+
+#if defined(LLVM_ON_UNIX)
+  struct tm *LT = ::localtime_r(&OurTime, &Storage);
+  assert(LT);
+  (void)LT;
+#endif
+#if defined(LLVM_ON_WIN32)
+  int Error = ::_localtime64_s(&Storage, &OurTime);
+  assert(!Error);
+  (void)Error;
+#endif
+
+  return Storage;
+}
+
+raw_ostream &operator<<(raw_ostream &OS, TimePoint<> TP) {
+  struct tm LT = getStructTM(TP);
+  char Buffer[sizeof("YYYY-MM-DD HH:MM:SS")];
+  strftime(Buffer, sizeof(Buffer), "%Y-%m-%d %H:%M:%S", &LT);
+  return OS << Buffer << '.'
+            << format("%.9lu",
+                      long((TP.time_since_epoch() % std::chrono::seconds(1))
+                               .count()));
+}
+
+} // namespace llvm

lib/Support/TimeValue.cpp

@@ -12,7 +12,8 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Support/TimeValue.h"
-#include "llvm/Config/config.h"
+#include "llvm/Support/Chrono.h"
+#include "llvm/Support/ScopedPrinter.h"
 
 namespace llvm {
 
@@ -45,12 +46,10 @@ void TimeValue::normalize() {
   }
 }
 
-} // namespace llvm
+std::string TimeValue::str() const { return to_string(TimePoint<>(*this)); }
 
-/// Include the platform-specific portion of TimeValue class
-#ifdef LLVM_ON_UNIX
-#include "Unix/TimeValue.inc"
-#endif
-#ifdef LLVM_ON_WIN32
-#include "Windows/TimeValue.inc"
-#endif
+TimeValue TimeValue::now() {
+  return TimePoint<>(std::chrono::system_clock::now());
+}
+
+} // namespace llvm

lib/Support/Unix/TimeValue.inc

@@ -1,54 +0,0 @@
-//===- Unix/TimeValue.cpp - Unix TimeValue Implementation -------*- C++ -*-===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This file implements the Unix specific portion of the TimeValue class.
-//
-//===----------------------------------------------------------------------===//
-
-//===----------------------------------------------------------------------===//
-//=== WARNING: Implementation here must contain only generic UNIX code that
-//===          is guaranteed to work on *all* UNIX variants.
-//===----------------------------------------------------------------------===//
-
-#include "Unix.h"
-
-namespace llvm {
-  using namespace sys;
-
-std::string TimeValue::str() const {
-  time_t OurTime = time_t(this->toEpochTime());
-  struct tm Storage;
-  struct tm *LT = ::localtime_r(&OurTime, &Storage);
-  assert(LT);
-  char Buffer1[sizeof("YYYY-MM-DD HH:MM:SS")];
-  strftime(Buffer1, sizeof(Buffer1), "%Y-%m-%d %H:%M:%S", LT);
-  char Buffer2[sizeof("YYYY-MM-DD HH:MM:SS.MMMUUUNNN")];
-  snprintf(Buffer2, sizeof(Buffer2), "%s.%.9u", Buffer1, this->nanoseconds());
-  return std::string(Buffer2);
-}
-
-TimeValue TimeValue::now() {
-  struct timeval the_time;
-  timerclear(&the_time);
-  if (0 != ::gettimeofday(&the_time,nullptr)) {
-    // This is *really* unlikely to occur because the only gettimeofday
-    // errors concern the timezone parameter which we're passing in as 0.
-    // In the unlikely case it does happen, just return MinTime, no error
-    // message needed.
-    return MinTime();
-  }
-
-  return TimeValue(
-    static_cast<TimeValue::SecondsType>( the_time.tv_sec +
-      PosixZeroTimeSeconds ),
-    static_cast<TimeValue::NanoSecondsType>( the_time.tv_usec *
-      NANOSECONDS_PER_MICROSECOND ) );
-}
-
-}

lib/Support/Windows/TimeValue.inc

@@ -1,61 +0,0 @@
-//===- Win32/TimeValue.cpp - Win32 TimeValue Implementation -----*- C++ -*-===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This file provides the Win32 implementation of the TimeValue class.
-//
-//===----------------------------------------------------------------------===//
-
-#include "WindowsSupport.h"
-#include "llvm/Support/Format.h"
-#include "llvm/Support/raw_ostream.h"
-#include <cctype>
-#include <time.h>
-
-using namespace llvm;
-using namespace llvm::sys;
-
-//===----------------------------------------------------------------------===//
-//=== WARNING: Implementation here must contain only Win32 specific code.
-//===----------------------------------------------------------------------===//
-
-TimeValue TimeValue::now() {
-  uint64_t ft;
-  GetSystemTimeAsFileTime(reinterpret_cast<FILETIME *>(&ft));
-
-  TimeValue t(0, 0);
-  t.fromWin32Time(ft);
-  return t;
-}
-
-std::string TimeValue::str() const {
-  std::string S;
-  struct tm *LT;
-#ifdef __MINGW32__
-  // Old versions of mingw don't have _localtime64_s. Remove this once we drop support
-  // for them.
-  time_t OurTime = time_t(this->toEpochTime());
-  LT = ::localtime(&OurTime);
-  assert(LT);
-#else
-  struct tm Storage;
-  __time64_t OurTime = this->toEpochTime();
-  int Error = ::_localtime64_s(&Storage, &OurTime);
-  assert(!Error);
-  (void)Error;
-  LT = &Storage;
-#endif
-
-  char Buffer[sizeof("YYYY-MM-DD HH:MM:SS")];
-  strftime(Buffer, sizeof(Buffer), "%Y-%m-%d %H:%M:%S", LT);
-  raw_string_ostream OS(S);
-  OS << format("%s.%.9u", static_cast<const char *>(Buffer),
-               this->nanoseconds());
-  OS.flush();
-  return S;
-}

unittests/Support/CMakeLists.txt

@@ -9,6 +9,7 @@ add_llvm_unittest(SupportTests
   BlockFrequencyTest.cpp
   BranchProbabilityTest.cpp
   Casting.cpp
+  Chrono.cpp
   CommandLineTest.cpp
   CompressionTest.cpp
   ConvertUTFTest.cpp

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

unittests/Support/TimeValueTest.cpp

@@ -37,4 +37,14 @@ TEST(TimeValue, Win32FILETIME) {
   EXPECT_EQ(ft1970, epoch.toWin32Time());
 }
 
+TEST(TimeValue, Chrono) {
+  sys::TimeValue TV;
+  TV.fromEpochTime(0);
+  sys::TimePoint<> TP = TV;
+  EXPECT_EQ(0u, sys::toTimeT(TP));
+
+  TP += std::chrono::seconds(47);
+  TV = TP;
+  EXPECT_EQ(47u, TV.toEpochTime());
+}
 }