Commit 90e3121a authored by JINMEI Tatuya's avatar JINMEI Tatuya
Browse files

[2091b] more documentation

parent b4067dc7
......@@ -50,7 +50,7 @@ class RBTree;
/// This is meant to be used only from RBTree. It is meaningless to inherit it
/// or create instances of it from elsewhere. For that reason, the constructor
/// is private.
/// (and the allocator, see below) is private.
/// It serves three roles. One is to keep structure of the \c RBTree as a
/// red-black tree. For that purpose, it has left, right and parent pointers
......@@ -65,6 +65,16 @@ class RBTree;
/// One special kind of node is non-terminal node. It has subdomains with
/// RRsets, but doesn't have any RRsets itself.
/// In order to keep memory footprint as small as possible, the node data
/// are heavily packed. Specifically, some internal node properties (such as
/// the node color) are encoded as part of "flags", some of the flag bits
/// can also be set by the user application. Each node is associated with
/// a sequence of domain name labels, which is essentially the search/insert
/// key for the noce (see also the description of RBTree). This is encoded
/// as opaque binary immediately followed by the main node object. The size
/// of the allocated space for the labels data is encoded by borrowing some
/// bits of the "flags" field.
template <typename T>
class RBNode : public boost::noncopyable {
......@@ -97,6 +107,20 @@ private:
/// \brief Accessor to the memory region for node labels.
/// The only valid usage of the returned pointer is to pass it to the
/// corresponding constructor of \c dns::LabelSequence.
const void* getLabelsData() const { return (this + 1); }
/// \brief Accessor to the memory region for node labels, mutable version.
/// The only valid usage of the returned pointer is to pass it to
/// \c LabelSequence::serialize() with the node's labels_capacity_ member
/// (which should be sufficiently large for the \c LabelSequence in that
/// context).
void* getLabelsData() { return (this + 1); }
/// \brief Allocate and construct \c RBNode
/// This static method allocates memory for a new \c RBNode object
......@@ -132,17 +156,14 @@ private:
mem_sgmt.deallocate(rbnode, sizeof(RBNode<T>) + labels_capacity);
/// TBD
/// \brief Reset node's label sequence to a new one.
/// The new labels must be a sub sequence of the current label sequence;
/// otherwise the serialize() method will throw an exception.
void resetLabels(const dns::LabelSequence& labels) {
labels.serialize(getLabelsData(), labels_capacity_);
/// TBD
const void* getLabelsData() const { return (this + 1); }
/// TBD
void* getLabelsData() { return (this + 1); }
/// \brief Alias for shared pointer to the data.
typedef boost::shared_ptr<T> NodeDataPtr;
......@@ -162,7 +183,8 @@ public:
FLAG_SUBTREE_ROOT = 4, ///< Set if the node is the root of a subtree
FLAG_USER1 = 0x400000U, ///< Application specific flag
FLAG_USER2 = 0x200000U, ///< Application specific flag
FLAG_USER3 = 0x100000U ///< Application specific flag
FLAG_USER3 = 0x100000U, ///< Application specific flag
FLAG_MAX = 0x400000U // for integrity check
// Some flag values are expected to be used for internal purposes
......@@ -184,12 +206,18 @@ public:
/// To get the absolute name of one node, the node path from the top node
/// to current node has to be recorded.
const isc::dns::Name getName() const {
assert(labels_capacity_ != 0);
assert(labels_capacity_ != 0); // shouldn't be called on a NULL node.
return (dns::Name(dns::LabelSequence(getLabelsData()).toText()));
/// \brief Return the label sequence of the node.
/// This method returns the label sequence corresponding to this node
/// in the form of \c dns::LabelSequence object. Any modification to
/// the tree can invalidate the returned \c LabelSequence object or copy
/// of it; in general, it's expected to be used in a very limited scope.
dns::LabelSequence getLabels() const {
assert(labels_capacity_ != 0);
assert(labels_capacity_ != 0); // shouldn't be called on a NULL node.
return (dns::LabelSequence(getLabelsData()));
......@@ -395,7 +423,6 @@ private:
const RBNode<T>* getRight() const {
return (right_.get());
RBNodeColor color_;
/// \brief Data stored here.
......@@ -420,13 +447,23 @@ private:
return (down_.get());
/// \brief If callback should be called when traversing this node in
/// RBTree::find().
/// \brief Internal or user-configurable flags of node's properties.
/// See the \c Flags enum for available flags.
/// \todo It might be needed to put it into more general attributes field.
/// For memory efficiency reasons, we only use a subset of the 32-bit
/// space, and use the rest to store the allocated size for the node's
/// label sequence data.
uint32_t flags_ : 23; // largest flag being 0x400000
const uint32_t labels_capacity_ : 9; // range is 0..511
/// TBD
BOOST_STATIC_ASSERT((1 << 23) > FLAG_MAX); // assumption check
const uint32_t labels_capacity_ : 9; // size for labelseq; range is 0..511
// Make sure the reserved space for labels_capacity_ is sufficiently
// large. In effect, we use the knowledge of the implementation of the
// serialization, but we still only use its public interface, and the
// public interface of this class doesn't rely on this assumption.
// So we can change this implementation without affecting its users if
// a future change to LabelSequence breaks this assumption.
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