string: correct the lower comparator for cstrings

string.hpp

@@ -312,7 +312,7 @@ namespace cruft::string {
     struct less {
         bool operator() (char const *a, char const *b) const noexcept
         {
-            for (; a && b; ++a, ++b) {
+            for (; *a && *b; ++a, ++b) {
                 auto const &a_val = TransformV (*a);
                 auto const &b_val = TransformV (*b);
 
@@ -322,7 +322,7 @@ namespace cruft::string {
                     return false;
             }
 
-            return a == nullptr && b != nullptr;
+            return *a == '\0' && *b != '\0';
         }
 
         bool operator() (std::string const &a, std::string const & b) const noexcept

test/string.cpp

@@ -226,7 +226,46 @@ void test_comparator_less (cruft::TAP::logger &tap)
 
 
 ///////////////////////////////////////////////////////////////////////////////
-void test_comparator_lower (cruft::TAP::logger &tap)
+void test_less_lower (cruft::TAP::logger &tap)
+{
+    struct {
+        char const *a;
+        char const *b;
+        bool expected;
+        char const *message;
+    } const TESTS[] = {
+        { "a", "b", true, "single letter lhs" },
+        { "b", "a", false, "single letter rhs" },
+
+        { "a", "a", false, "single lower equal" },
+        { "a", "A", false, "lower, upper singles" },
+        { "A", "a", false, "upper, lower singles" },
+
+        { "a", "aa", true, "shorter lhs" },
+        { "aa", "a", false, "shorter hhs" },
+
+        { "date", "User-Agent", true, "lower lhs, upper rhs" },
+    };
+
+    cruft::string::less_lower cmp;
+
+    for (auto const &t: TESTS) {
+        tap.expect_eq (cmp (t.a, t.b), t.expected, "less::lower, pointers, {}", t.message);
+        tap.expect_eq (
+            cmp (
+                std::string_view {t.a},
+                std::string_view {t.b}
+            ),
+            t.expected,
+            "less::lower, string_view, {}",
+            t.message
+        );
+    }
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+void test_equality_lower (cruft::TAP::logger &tap)
 {
     struct {
         char const *a;
@@ -243,9 +282,8 @@ void test_comparator_lower (cruft::TAP::logger &tap)
 
     cruft::string::equality::lower cmp;
 
-    for (auto const &t: TESTS) {
+    for (auto const &t: TESTS)
         tap.expect_eq (cmp (t.a, t.b), t.equal, "equality::lower, pointers, {}", t.message);
-    }
 }
 
 
@@ -261,7 +299,8 @@ main (int, char**)
     test_position (tap);
     test_contains (tap);
     test_comparator_less (tap);
-    test_comparator_lower (tap);
+    test_less_lower (tap);
+    test_equality_lower (tap);
 
     return tap.status ();
 }