Add format benchmarks

src/format.hpp

@@ -254,6 +254,25 @@ inline constexpr int max_decimal_length_v = decltype(term(T{}))::kMaxLength;
 
 inline constexpr DoubleTerm term(double s) { return DoubleTerm(s); }
 
+// Runtime string term for std::string_view (works with std::string, const
+// char*, etc.)
+struct StringViewTerm {
+  explicit constexpr StringViewTerm(std::string_view s) : s(s) {}
+  static constexpr int kMaxLength =
+      512; // Conservative upper bound for runtime strings
+  void write(char *&buf) const {
+    std::memcpy(buf, s.data(), s.size());
+    buf += s.size();
+  }
+
+private:
+  std::string_view s;
+};
+
+inline constexpr StringViewTerm term(std::string_view s) {
+  return StringViewTerm(s);
+}
+
 } // namespace detail
 
 /**