Fixed the inefficient isTrue function

Author: mikael-s-persson

cpr/util.cpp

@@ -11,6 +11,7 @@
 #include <curl/curl.h>
 #include <fstream>
 #include <ios>
+#include <iterator>
 #include <sstream>
 #include <string>
 #include <type_traits>
@@ -187,9 +188,10 @@ util::SecureString urlDecode(std::string_view s) {
 }
 
 bool isTrue(const std::string& s) {
-    std::string temp_string{s};
-    std::transform(temp_string.begin(), temp_string.end(), temp_string.begin(), [](unsigned char c) { return static_cast<unsigned char>(std::tolower(c)); });
-    return temp_string == "true";
+    constexpr std::string_view tmp = "true";
+    auto [s_it, tmp_it] = std::mismatch(s.begin(), s.end(), tmp.begin(), tmp.end(),
+        [](auto s_c, auto t_c) { return std::tolower(s_c) == t_c; });
+    return s_it == s.end() && tmp_it == tmp.end();
 }
 
 time_t sTimestampToT(const std::string& st) {