Add test for std::bitset

Closes #9

Author: hahnjo

types/README.md

@@ -2,6 +2,7 @@
 
  * [`array`](array): `std::array`
  * [`atomic`](atomic): `std::atomic`
+ * [`bitset`](bitset): `std::bitset`
  * [`fundamental`](fundamental): fundamental column types
  * [`multiset`](multiset): `std::multiset` with all `[Split]Index{32,64}` column types
  * [`optional`](optional): `std::optional` with different element types

types/bitset/README.md

@@ -0,0 +1,15 @@
+# `std::bitset`
+
+## Fields
+
+ * `Bitset1`: `std::bitset<1>`
+ * `Bitset64`: `std::bitset<64>`
+ * `Bitset65`: `std::bitset<65>`
+
+with the default column types.
+
+## Entries
+
+1. Ascending bits set
+2. All bits set
+3. All bits unset

types/bitset/read.C

@@ -0,0 +1,53 @@
+#include <ROOT/REntry.hxx>
+#include <ROOT/RNTupleReader.hxx>
+
+using ROOT::Experimental::REntry;
+using ROOT::Experimental::RNTupleReader;
+
+#include <bitset>
+#include <cstddef>
+#include <fstream>
+#include <ostream>
+#include <string>
+#include <string_view>
+
+template <std::size_t N>
+static void PrintBitsetValue(const REntry &entry, std::string_view name,
+                             std::ostream &os, bool last = false) {
+  auto &value = *entry.GetPtr<std::bitset<N>>(name);
+  os << "    \"" << name << "\": \"" << value.to_string() << "\"";
+  if (!last) {
+    os << ",";
+  }
+  os << "\n";
+}
+
+void read(std::string_view input = "types.bitset.root",
+          std::string_view output = "types.bitset.json") {
+  std::ofstream os(std::string{output});
+  os << "[\n";
+
+  auto reader = RNTupleReader::Open("ntpl", input);
+  auto &entry = reader->GetModel().GetDefaultEntry();
+  bool first = true;
+  for (auto index : *reader) {
+    reader->LoadEntry(index);
+
+    if (first) {
+      first = false;
+    } else {
+      os << ",\n";
+    }
+    os << "  {\n";
+
+    PrintBitsetValue<1>(entry, "Bitset1", os);
+    PrintBitsetValue<64>(entry, "Bitset64", os);
+    PrintBitsetValue<65>(entry, "Bitset65", os, /*last=*/true);
+
+    os << "  }";
+    // Newline is intentionally missing, may need to print a comma before the
+    // next entry.
+  }
+  os << "\n";
+  os << "]\n";
+}

types/bitset/write.C

@@ -0,0 +1,42 @@
+#include <ROOT/RNTupleModel.hxx>
+#include <ROOT/RNTupleWriteOptions.hxx>
+#include <ROOT/RNTupleWriter.hxx>
+
+using ROOT::Experimental::RNTupleModel;
+using ROOT::Experimental::RNTupleWriteOptions;
+using ROOT::Experimental::RNTupleWriter;
+
+#include <bitset>
+#include <memory>
+#include <string_view>
+
+void write(std::string_view filename = "types.bitset.root") {
+  auto model = RNTupleModel::Create();
+
+  auto Bitset1 = model->MakeField<std::bitset<1>>("Bitset1");
+  auto Bitset64 = model->MakeField<std::bitset<64>>("Bitset64");
+  auto Bitset65 = model->MakeField<std::bitset<65>>("Bitset65");
+
+  RNTupleWriteOptions options;
+  options.SetCompression(0);
+  auto writer =
+      RNTupleWriter::Recreate(std::move(model), "ntpl", filename, options);
+
+  // First entry: ascending bits set
+  Bitset1->set(0);
+  Bitset64->set(1);
+  Bitset65->set(2);
+  writer->Fill();
+
+  // Second entry: all bits set
+  Bitset1->set();
+  Bitset64->set();
+  Bitset65->set();
+  writer->Fill();
+
+  // Third entry: no bits set
+  Bitset1->reset();
+  Bitset64->reset();
+  Bitset65->reset();
+  writer->Fill();
+}