Support formatv of TimePoint with strftime-style formats.

Summary:
Support formatv of TimePoint with strftime-style formats.

Extensions for millis/micros/nanos are added.
Inital use case is HH:MM:SS.MMM timestamps in clangd logs.

Reviewers: bkramer, ilya-biryukov

Subscribers: labath, llvm-commits

Differential Revision: https://reviews.llvm.org/D38992

llvm-svn: 316419

1 files changed, 40 insertions, 0 deletions

diff --git a/llvm/lib/Support/Chrono.cpp b/llvm/lib/Support/Chrono.cpp
index daccaf1fc10..a39b485bd13 100644
--- a/llvm/lib/Support/Chrono.cpp
+++ b/llvm/lib/Support/Chrono.cpp
@@ -51,4 +51,44 @@ raw_ostream &operator<<(raw_ostream &OS, TimePoint<> TP) {
                                .count()));
 }
 
+void format_provider<TimePoint<>>::format(const TimePoint<> &T, raw_ostream &OS,
+                                          StringRef Style) {
+  using namespace std::chrono;
+  TimePoint<seconds> Truncated = time_point_cast<seconds>(T);
+  auto Fractional = T - Truncated;
+  struct tm LT = getStructTM(Truncated);
+  // Handle extensions first. strftime mangles unknown %x on some platforms.
+  if (Style.empty()) Style = "%Y-%m-%d %H:%M:%S.%N";
+  std::string Format;
+  raw_string_ostream FStream(Format);
+  for (unsigned I = 0; I < Style.size(); ++I) {
+    if (Style[I] == '%' && Style.size() > I + 1) switch (Style[I + 1]) {
+        case 'L':  // Milliseconds, from Ruby.
+          FStream << llvm::format(
+              "%.3lu", duration_cast<milliseconds>(Fractional).count());
+          ++I;
+          continue;
+        case 'f':  // Microseconds, from Python.
+          FStream << llvm::format(
+              "%.6lu", duration_cast<microseconds>(Fractional).count());
+          ++I;
+          continue;
+        case 'N':  // Nanoseconds, from date(1).
+          FStream << llvm::format(
+              "%.6lu", duration_cast<nanoseconds>(Fractional).count());
+          ++I;
+          continue;
+        case '%':  // Consume %%, so %%f parses as (%%)f not %(%f)
+          FStream << "%%";
+          ++I;
+          continue;
+      }
+    FStream << Style[I];
+  }
+  FStream.flush();
+  char Buffer[256];  // Should be enough for anywhen.
+  size_t Len = strftime(Buffer, sizeof(Buffer), Format.c_str(), &LT);
+  OS << (Len ? Buffer : "BAD-DATE-FORMAT");
+}
+
 } // namespace llvm