PyCoverage: avoid repeated string splitting, especially for uncovered lines

Source/CTest/cmCTestCoverageHandler.cxx

@@ -1709,29 +1709,26 @@ int cmCTestCoverageHandler::HandleTracePyCoverage(
 
         // Read the coverage count from the beginning of the Trace.py output
         // line
-        std::string prefix = nl.substr(0, 6);
-        if (prefix[5] != ' ' && prefix[5] != ':') {
-          // This is a hack. We should really do something more elaborate
-          prefix = nl.substr(0, 7);
-          if (prefix[6] != ' ' && prefix[6] != ':') {
-            prefix = nl.substr(0, 8);
-            if (prefix[7] != ' ' && prefix[7] != ':') {
-              cmCTestLog(this->CTest, ERROR_MESSAGE,
-                         "Currently the limit is maximum coverage of 999999"
-                           << std::endl);
-            }
+        std::string::size_type pos;
+        int cov = 0;
+        // This is a hack. We should really do something more elaborate
+        for (pos = 5; pos < 8; pos++) {
+          if (nl[pos] == ' ') {
+            // This line does not have ':' so no coverage here. That said,
+            // Trace.py does not handle not covered lines versus comments etc.
+            // So, this will be set to 0.
+            break;
+          }
+          if (nl[pos] == ':') {
+            cov = atoi(nl.substr(0, pos - 1).c_str());
+            break;
           }
         }
-        int cov = atoi(prefix.c_str());
-        if (prefix[prefix.size() - 1] != ':') {
-          // This line does not have ':' so no coverage here. That said,
-          // Trace.py does not handle not covered lines versus comments etc.
-          // So, this will be set to 0.
-          cov = 0;
+        if (pos == 8) {
+          cmCTestLog(this->CTest, ERROR_MESSAGE,
+                     "Currently the limit is maximum coverage of 999999"
+                       << std::endl);
         }
-        cmCTestOptionalLog(
-          this->CTest, DEBUG,
-          "Prefix: " << prefix << " cov: " << cov << std::endl, this->Quiet);
         // Read the line number starting at the 10th character of the gcov
         // output line
         long lineIdx = cnt;