[2428] Generic $DIRECTIVE handler

Decide which directive it is and call corresponding call based on that.
This currently throws NotImplemented for everything except for the
INCLUDE, which will get implemented in the next few commits in this
branch.

src/lib/dns/master_loader.cc

@@ -22,6 +22,7 @@
 
 #include <string>
 #include <memory>
+#include <strings.h>
 
 using std::string;
 using std::auto_ptr;
@@ -29,6 +30,16 @@ using std::auto_ptr;
 namespace isc {
 namespace dns {
 
+// An internal exception, used to control the code flow in case of errors.
+// It is thrown during the loading and caught later, not to be propagated
+// outside of the file.
+class InternalException : public isc::Exception {
+public:
+    InternalException(const char* filename, size_t line, const char* what) :
+        Exception(filename, line, what)
+    {}
+};
+
 class MasterLoader::MasterLoaderImpl {
 public:
     MasterLoaderImpl(const char* master_file,
@@ -94,6 +105,28 @@ public:
 
     bool loadIncremental(size_t count_limit);
 
+    void handleDirective(const char* directive, size_t length) {
+        // We use strncasecmp, because there seems to be no reasonable
+        // way to compare strings case-insensitive in C++
+
+        // Warning: The order of compared strings does matter. The length
+        // parameter applies to the first one only.
+        if (strncasecmp(directive, "INCLUDE", length)) {
+
+        } else if (strncasecmp(directive, "ORIGIN", length)) {
+            // TODO: Implement
+            isc_throw(isc::NotImplemented,
+                      "Origin directive not implemented yet");
+        } else if (strncasecmp(directive, "TTL", length)) {
+            // TODO: Implement
+            isc_throw(isc::NotImplemented,
+                      "TTL directive not implemented yet");
+        } else {
+            isc_throw(InternalException, "Unknown directive '" <<
+                      string(directive, directive + length) << "'");
+        }
+    }
+
 private:
     MasterLexer lexer_;
     const Name zone_origin_;
@@ -144,7 +177,19 @@ MasterLoader::MasterLoaderImpl::loadIncremental(size_t count_limit) {
             const MasterToken::StringRegion&
                 name_string(lexer_.getNextToken(MasterToken::QSTRING).
                             getStringRegion());
-            // TODO $ handling
+
+            if (name_string.len > 0 && name_string.beg[0] == '$') {
+                // This should have either thrown (and the error handler
+                // will read up until the end of line) or read until the
+                // end of line.
+
+                // Exclude the $ from the string on this point.
+                handleDirective(name_string.beg + 1, name_string.len - 1);
+                // So, get to the next line, there's nothing more interesting
+                // in this one.
+                continue;
+            }
+
             const Name name(name_string.beg, name_string.len,
                             &zone_origin_);
             // TODO: Some more flexibility. We don't allow omitting