Faster implementation of startsWith() for strings

halfgaar · Mar 23, 2024 · 82a1600 · 82a1600
1 parent e28e8ca
commit 82a1600
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Showing 4 changed files with 26 additions and 2 deletions.
diff --git a/FlashMQTests/maintests.cpp b/FlashMQTests/maintests.cpp
@@ -283,6 +283,8 @@ MainTests::MainTests()
     REGISTER_FUNCTION(testWebsocketHugePing);
     REGISTER_FUNCTION(testWebsocketManyBigPingFrames);
     REGISTER_FUNCTION(testWebsocketClose);
+    REGISTER_FUNCTION(testStartsWith);
+
 }
 
 bool MainTests::test(const std::vector<std::string> &tests)

diff --git a/FlashMQTests/maintests.h b/FlashMQTests/maintests.h
@@ -203,6 +203,8 @@ class MainTests
     void testWebsocketManyBigPingFrames();
     void testWebsocketClose();
 
+    void testStartsWith();
+
 
 public:
     MainTests();

diff --git a/FlashMQTests/tst_maintests.cpp b/FlashMQTests/tst_maintests.cpp
@@ -2831,6 +2831,16 @@ void MainTests::testTopicMatchingInSubscriptionTree()
     testTopicMatchingInSubscriptionTreeHelper("+/one/+/+/", "/one/two/asdf/a", 0);
 }
 
-
+void MainTests::testStartsWith()
+{
+    FMQ_VERIFY(startsWith("", ""));
+    FMQ_VERIFY(startsWith("a", ""));
+    FMQ_VERIFY(startsWith("abcd", "abc"));
+    FMQ_VERIFY(startsWith("a", ""));
+
+    FMQ_VERIFY(!startsWith("abc", "abcd"));
+    FMQ_VERIFY(!startsWith("abcd", "bcd"));
+    FMQ_VERIFY(!startsWith("", "a"));
+}
 
 
diff --git a/utils.cpp b/utils.cpp
@@ -295,7 +295,17 @@ std::string &rtrim(std::string &s, unsigned char c)
 
 bool startsWith(const std::string &s, const std::string &needle)
 {
-    return s.find(needle) == 0;
+    if (s.length() < needle.length())
+        return false;
+
+    size_t i;
+    for (i = 0; i < needle.length(); i++)
+    {
+        if (s[i] != needle[i])
+            return false;
+    }
+
+    return i == needle.length();
 }
 
 std::string getSecureRandomString(const ssize_t len)