feat: add hex

include/cpputils/hex.h

@@ -0,0 +1,58 @@
+#pragma once
+
+#include <string>
+
+namespace cpputils {
+
+namespace hex {
+
+std::string toHex(std::string const& input);
+std::string fromHex(std::string const& input);
+
+constexpr int hexVal(char c) {
+  switch (c) {
+    case '0':
+      return 0;
+    case '1':
+      return 1;
+    case '2':
+      return 2;
+    case '3':
+      return 3;
+    case '4':
+      return 4;
+    case '5':
+      return 5;
+    case '6':
+      return 6;
+    case '7':
+      return 7;
+    case '8':
+      return 8;
+    case '9':
+      return 9;
+    case 'a':
+    case 'A':
+      return 10;
+    case 'b':
+    case 'B':
+      return 11;
+    case 'c':
+    case 'C':
+      return 12;
+    case 'd':
+    case 'D':
+      return 13;
+    case 'e':
+    case 'E':
+      return 14;
+    case 'f':
+    case 'F':
+      return 15;
+    default:
+      return -1;
+  }
+}
+
+}  // namespace hex
+}  // namespace cpputils