[1603] updated the behavior of setCompressMode(): now disallow it in rendering.

the new implementation doesn't allow such flexibility anymore (as the
hash value would change).  added comment about that, and updated the test
accordingly.

1 files changed, 10 insertions, 0 deletions

diff --git a/src/lib/dns/messagerenderer.h b/src/lib/dns/messagerenderer.h
index f7f2381dc0..4c1c92a34f 100644
--- a/src/lib/dns/messagerenderer.h
+++ b/src/lib/dns/messagerenderer.h
@@ -359,7 +359,17 @@ public:
     virtual CompressMode getCompressMode() const;
     virtual void setTruncated();
     virtual void setLengthLimit(size_t len);
+
+    /// This implementation does not allow this call in the middle of
+    /// rendering (i.e. after at least one name is rendered) due to
+    /// restriction specific to the internal implementation.  Such attempts
+    /// will result in an \c isc::InvalidParameter exception.
+    ///
+    /// This shouldn't be too restrictive in practice; there's no known
+    /// practical case for such a mixed compression policy in a single
+    /// message.
     virtual void setCompressMode(CompressMode mode);
+
     virtual void clear();
     virtual void writeName(const Name& name, bool compress = true);
 private: