diff --git a/include/opendht/indexation/pht.h b/include/opendht/indexation/pht.h
index 5e91ac9cdb35628e2cc38d23b4d97993724140da..45e7d9cc8098bf4c8f9e95e9555551328fd4d71c 100644
--- a/include/opendht/indexation/pht.h
+++ b/include/opendht/indexation/pht.h
@@ -15,6 +15,15 @@
namespace dht {
namespace indexation {
+/*!
+ * @class Prefix
+ * @brief A blob structure which prefixes a Key in the PHT.
+ * @details
+ * Since the PHT structure is a "trie", every node in this structure have a
+ * label which is defined by the path from the root of the trie to the node. If
+ * the node in question is a leaf, *the label is a prefix of all the keys
+ * contained in the leaf*.
+ */
struct Prefix {
Prefix() {}
Prefix(InfoHash h) : size_(h.size() * 8), content_(h.begin(), h.end()) {}
@@ -32,6 +41,12 @@ struct Prefix {
len += size_;
return Prefix(*this, len);
}
+
+ /**
+ * This methods gets the prefix of its sibling in the PHT structure.
+ *
+ * @return The prefix of this sibling.
+ */
Prefix getSibling() const {
Prefix copy = *this;
if (size_) {
@@ -59,6 +74,30 @@ struct Prefix {
return ss.str();
}
+ static inline unsigned commonBits(const Prefix& p1, const Prefix& p2) {
+ unsigned i, j;
+ uint8_t x;
+ auto longest_prefix_size = std::min(p1.size_, p2.size_);
+
+ for (i = 0; i < longest_prefix_size; i++) {
+ if (p1.content_.data()[i] != p2.content_.data()[i])
+ break;
+ }
+
+ if (i == longest_prefix_size)
+ return 8*longest_prefix_size;
+
+ x = p1.content_.data()[i] ^ p2.content_.data()[i];
+
+ j = 0;
+ while ((x & 0x80) == 0) {
+ x <<= 1;
+ j++;
+ }
+
+ return 8 * i + j;
+ }
+
size_t size_ {0};
Blob content_ {};
};
@@ -111,7 +150,7 @@ public:
/**
* Lookup a key for a value.
*/
- void lookup(Key k, LookupCallback cb = {}, Dht::DoneCallbackSimple doneCb = {});
+ void lookup(Key k, LookupCallback cb = {}, Dht::DoneCallbackSimple doneCb = {}, bool exact_match = true);
/**
* Adds an entry into the index.
*/
@@ -135,10 +174,10 @@ private:
* Performs a step in the lookup operation. Each steps are performed
* asynchronously.
*/
- void lookupStep(Prefix k, std::shared_ptr<int> lo,
- std::shared_ptr<int> hi,
- std::shared_ptr<std::vector<std::shared_ptr<Value>>> vals,
- LookupCallback cb, Dht::DoneCallbackSimple done_cb);
+ void lookupStep(Prefix k, std::shared_ptr<int> lo, std::shared_ptr<int> hi,
+ std::shared_ptr<std::vector<std::shared_ptr<Value>>> vals,
+ LookupCallback cb, Dht::DoneCallbackSimple done_cb,
+ std::shared_ptr<unsigned> max_common_prefix_len);
/**
* Updates the canary token on the node responsible for the specified
diff --git a/src/indexation/pht.cpp b/src/indexation/pht.cpp
index 07442a6781ac72cb7e5a70aba515c5ecd88c8df1..1b2e2636a95a6311487d780621213f22742ffedf 100644
--- a/src/indexation/pht.cpp
+++ b/src/indexation/pht.cpp
@@ -4,10 +4,12 @@
namespace dht {
namespace indexation {
-void Pht::lookupStep(Prefix p, std::shared_ptr<int> lo,
- std::shared_ptr<int> hi,
- std::shared_ptr<std::vector<std::shared_ptr<Value>>> vals,
- LookupCallback cb, Dht::DoneCallbackSimple done_cb)
+const ValueType IndexEntry::TYPE = ValueType::USER_DATA;
+
+void Pht::lookupStep(Prefix p, std::shared_ptr<int> lo, std::shared_ptr<int> hi,
+ std::shared_ptr<std::vector<std::shared_ptr<Value>>> vals,
+ LookupCallback cb, Dht::DoneCallbackSimple done_cb,
+ std::shared_ptr<unsigned> max_common_prefix_len)
{
struct node_lookup_result {
bool done {false};
@@ -28,7 +30,7 @@ void Pht::lookupStep(Prefix p, std::shared_ptr<int> lo,
} else {
// internal node
*lo = mid+1;
- lookupStep(p, lo, hi, vals, cb, done_cb);
+ lookupStep(p, lo, hi, vals, cb, done_cb, max_common_prefix_len);
}
};
if (*lo <= *hi) {
@@ -42,8 +44,27 @@ void Pht::lookupStep(Prefix p, std::shared_ptr<int> lo,
else {
IndexEntry entry;
entry.unpackValue(*value);
- if (entry.prefix == p.content_)
+
+ auto add_value = [&](bool better = true) {
vals->emplace_back(std::make_shared<Value>(entry.value));
+ if (better and max_common_prefix_len)
+ *max_common_prefix_len = Prefix::commonBits(p, vals->front()->first);
+ };
+ if (max_common_prefix_len) {
+ if (vals->empty()) {
+ add_value();
+ } else {
+ auto common_bits = Prefix::commonBits(vals->front()->first, p.getPrefix(mid));
+ if (common_bits == *max_common_prefix_len)
+ add_value(false);
+ else if (common_bits > *max_common_prefix_len) {
+ vals->clear();
+ add_value();
+ }
+ }
+ }
+ else if (entry.prefix == p.content_)
+ add_value(false);
}
return true;
};
@@ -59,7 +80,7 @@ void Pht::lookupStep(Prefix p, std::shared_ptr<int> lo,
if (not first_res->is_pht) {
// Not a PHT node.
*hi = mid-1;
- lookupStep(p, lo, hi, vals, cb, done_cb);
+ lookupStep(p, lo, hi, vals, cb, done_cb, max_common_prefix_len);
} else {
first_res->done = true;
if (second_res->done)
@@ -88,12 +109,13 @@ void Pht::lookupStep(Prefix p, std::shared_ptr<int> lo,
}
}
-void Pht::lookup(Key k, Pht::LookupCallback cb, Dht::DoneCallbackSimple done_cb) {
+void Pht::lookup(Key k, Pht::LookupCallback cb, Dht::DoneCallbackSimple done_cb, bool exact_match) {
auto values = std::make_shared<std::vector<std::shared_ptr<Value>>>();
auto prefix = linearize(k);
auto lo = std::make_shared<int>(0);
auto hi = std::make_shared<int>(prefix.size_);
- lookupStep(prefix, lo, hi, values, cb, done_cb);
+ std::shared_ptr<unsigned> max_common_prefix_len = not exact_match ? std::make_shared<unsigned>(0) : nullptr;
+ lookupStep(prefix, lo, hi, values, cb, done_cb, max_common_prefix_len);
}
void Pht::updateCanary(Prefix p) {
@@ -145,7 +167,7 @@ void Pht::insert(Key k, Value v, Dht::DoneCallbackSimple done_cb) {
updateCanary(*final_prefix);
dht_->put(final_prefix->hash(), std::move(entry), done_cb);
}
- }
+ }, nullptr
);
}