optimization

Author: pfeatherstone

README.md

@@ -44,14 +44,14 @@ Note, the example server is single threaded, uses C++20 coroutines and basic aut
 
 | Transport | Connections | Requests / s |
 | --------- | ----------- | -------------|
-| TCP       | 1           | 29268.81     |
-| TCP       | 2           | 41123.15     |
-| TCP       | 5           | 42906.12     |
-| TCP       | 10          | 43582.05     |
-| TLS       | 1           | 20317.42     |
-| TLS       | 2           | 32633.12     |
-| TLS       | 5           | 35227.99     |
-| TLS       | 10          | 36615.81     |
+| TCP       | 1           | 42654.66     |
+| TCP       | 2           | 74901.81     |
+| TCP       | 5           | 88949.07     |
+| TCP       | 10          | 94381.10     |
+| TLS       | 1           | 30400.27     |
+| TLS       | 2           | 50593.61     |
+| TLS       | 5           | 57112.41     |
+| TLS       | 10          | 62193.85     |
 
 Not bad.
 

src/http.cpp

@@ -428,11 +428,17 @@ namespace http
 
 //----------------------------------------------------------------------------------------------------------------
 
-    std::string to_lower(std::string_view s)
+    constexpr char fast_ascii_tolower(const char c) 
     {
-        std::string out(s.length(), '\0');
-        std::transform(s.begin(), s.end(), out.begin(), [](unsigned char c) { return std::tolower(c); });
-        return out;
+        // The following is a tad faster than std::tolower(c)
+        return (c >= 'A' && c <= 'Z') ? (c | 0x20) : c;
+    }
+
+    constexpr bool case_insenstive_equals(std::string_view a, std::string_view b)
+    {
+        return a.size() == b.size() && std::equal(begin(a), end(a), begin(b), [](char ac, char bc) {
+            return fast_ascii_tolower(ac) == fast_ascii_tolower(bc);
+        });
     }
 
     std::string_view field_label(field f)
@@ -443,7 +449,7 @@ namespace http
     field field_enum(std::string_view f)
     {
         for (unsigned int i = 0 ; i < std::size(FIELDS) ; ++i)
-            if (FIELDS[i] == to_lower(f))
+            if (case_insenstive_equals(FIELDS[i], f))
                 return (field)i;
         return unknown_field;
     }