[libc] Add strspn implementation and std::bitset

Reviewed By: sivachandra, abrachet

Differential Revision: https://reviews.llvm.org/D85103

2 files changed, 40 insertions, 0 deletions

diff --git a/libc/utils/CPP/Bitset.h b/libc/utils/CPP/Bitset.h
new file mode 100644
index 0000000..304a6fe
--- /dev/null
+++ b/libc/utils/CPP/Bitset.h
@@ -0,0 +1,39 @@
+//===-- A self contained equivalent of std::bitset --------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_UTILS_CPP_BITSET_H
+#define LLVM_LIBC_UTILS_CPP_BITSET_H
+
+#include <stddef.h> // For size_t.
+#include <stdint.h> // For uintptr_t.
+
+namespace __llvm_libc {
+namespace cpp {
+
+template <size_t NumberOfBits> struct Bitset {
+  static_assert(NumberOfBits != 0,
+                "Cannot create a __llvm_libc::cpp::Bitset of size 0.");
+
+  constexpr void set(size_t Index) {
+    Data[Index / BitsPerUnit] |= (uintptr_t{1} << (Index % BitsPerUnit));
+  }
+
+  constexpr bool test(size_t Index) const {
+    return Data[Index / BitsPerUnit] & (uintptr_t{1} << (Index % BitsPerUnit));
+  }
+
+private:
+  static constexpr size_t BitsPerByte = 8;
+  static constexpr size_t BitsPerUnit = BitsPerByte * sizeof(uintptr_t);
+  uintptr_t Data[(NumberOfBits + BitsPerUnit - 1) / BitsPerUnit] = {0};
+};
+
+} // namespace cpp
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_UTILS_CPP_BITSET_H
diff --git a/libc/utils/CPP/CMakeLists.txt b/libc/utils/CPP/CMakeLists.txt
index 4c7f5e9..60975fe 100644
--- a/libc/utils/CPP/CMakeLists.txt
+++ b/libc/utils/CPP/CMakeLists.txt
@@ -3,6 +3,7 @@ add_header_library(
   HDRS
     Array.h
     ArrayRef.h
+    Bitset.h
     Functional.h
     StringRef.h
     TypeTraits.h