Move some stuff out of LuaStack

luprex/cpp/core/util.hpp

@@ -497,6 +497,45 @@ constexpr auto hex32 = FormattedNumber<int>(0, true, 8, '0', 6);
 constexpr auto hex64 = FormattedNumber<int>(0, true, 16, '0', 6);
 constexpr auto dec = FormattedNumber<int>(0, false, 0, ' ', 6);
 
+// Encode a string as a token (fixed-width base38 number).
+// Each character is mapped to a digit 1-37 (0 means "no character"),
+// and the result is: CH0*38^11 + CH1*38^10 + ... + CH11*38^0.
+// Digit mapping: _ → 1, 0-9 → 2-11, a-z → 12-37.
+// Returns zero if the string is empty, too long, or contains
+// invalid characters.
+//
+static constexpr uint64_t encode_token(std::string_view str) {
+    if (str.size() > 12) return 0;
+    if (str.empty()) return 0;
+
+    uint64_t result = 0;
+    for (int i = 0; i < int(str.size()); i++) {
+        char c = str[i];
+        uint64_t digit = 0;
+        if (c == '_') {
+            digit = 1;
+        } else if ((c >= '0') && (c <= '9')) {
+            digit = uint64_t(c - '0') + 2;
+        } else if ((c >= 'a') && (c <= 'z')) {
+            digit = uint64_t(c - 'a') + 12;
+        } else if ((c >= 'A') && (c <= 'Z')) {
+            digit = uint64_t(c - 'A') + 12;
+        } else {
+            return 0;
+        }
+        result = result * 38 + digit;
+    }
+    // Pad remaining positions with zeros (no character).
+    for (int i = int(str.size()); i < 12; i++) {
+        result = result * 38;
+    }
+    return result;
+}
+
+// Decode a token (base38 number) back to a string.
+//
+eng::string decode_token(uint64_t value);
+
 } // namespace util
 
 template<class VALUE>