1 files changed, 46 insertions, 0 deletions
diff --git a/pw_bluetooth/public/pw_bluetooth/internal/hex.h b/pw_bluetooth/public/pw_bluetooth/internal/hex.h
new file mode 100644
index 000000000..3140898fe
--- /dev/null
+++ b/pw_bluetooth/public/pw_bluetooth/internal/hex.h
@@ -0,0 +1,46 @@
+// Copyright 2022 The Pigweed Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+#pragma once
+
+#include <cstdint>
+
+namespace pw::bluetooth::internal {
+
+// Parse a hexadecimal character to a 0-15 number. If the hex char is invalid
+// returns 0x100.
+constexpr uint16_t HexToNibble(char hex) {
+  if (hex >= '0' && hex <= '9') {
+    return hex - '0';
+  }
+  if (hex >= 'A' && hex <= 'F') {
+    return hex - 'A' + 10;
+  }
+  if (hex >= 'a' && hex <= 'f') {
+    return hex - 'a' + 10;
+  }
+  return 0x100;
+}
+
+// Convert a nibble (0 to 15 value) to its lowercase hexadecimal representation.
+constexpr char NibbleToHex(uint8_t value) {
+  if (value < 10) {
+    return '0' + value;
+  }
+  if (value < 16) {
+    return 'a' + value - 10;
+  }
+  return '?';
+}
+
+}  // namespace pw::bluetooth::internal