src: add SocketAddressLRU Utility

Adds a LRU cache for information associated with a SocketAddress.

PR-URL: https://github.com/nodejs/node/pull/34618
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>

1 files changed, 67 insertions, 0 deletions

diff --git a/src/node_sockaddr-inl.h b/src/node_sockaddr-inl.h
index a9d0ed061a1..c8b985aedda 100644
--- a/src/node_sockaddr-inl.h
+++ b/src/node_sockaddr-inl.h
@@ -7,6 +7,7 @@
 #include "node_internals.h"
 #include "node_sockaddr.h"
 #include "util-inl.h"
+#include "memory_tracker-inl.h"
 
 #include <string>
 
@@ -164,6 +165,72 @@ bool SocketAddress::operator==(const SocketAddress& other) const {
 bool SocketAddress::operator!=(const SocketAddress& other) const {
   return !(*this == other);
 }
+
+template <typename T>
+SocketAddressLRU<T>::SocketAddressLRU(
+    size_t max_size)
+    : max_size_(max_size) {}
+
+template <typename T>
+typename T::Type* SocketAddressLRU<T>::Peek(
+    const SocketAddress& address) const {
+  auto it = map_.find(address);
+  return it == std::end(map_) ? nullptr : &it->second->second;
+}
+
+template <typename T>
+void SocketAddressLRU<T>::CheckExpired() {
+  auto it = list_.rbegin();
+  while (it != list_.rend()) {
+    if (T::CheckExpired(it->first, it->second)) {
+      map_.erase(it->first);
+      list_.pop_back();
+      it = list_.rbegin();
+      continue;
+    } else {
+      break;
+    }
+  }
+}
+
+template <typename T>
+void SocketAddressLRU<T>::MemoryInfo(MemoryTracker* tracker) const {
+  tracker->TrackFieldWithSize("list", size() * sizeof(Pair));
+}
+
+// If an item already exists for the given address, bump up it's
+// position in the LRU list and return it. If the item does not
+// exist, create it. If an item is created, check the size of the
+// cache and adjust if necessary. Whether the item exists or not,
+// purge expired items.
+template <typename T>
+typename T::Type* SocketAddressLRU<T>::Upsert(
+    const SocketAddress& address) {
+
+  auto on_exit = OnScopeLeave([&]() { CheckExpired(); });
+
+  auto it = map_.find(address);
+  if (it != std::end(map_)) {
+    list_.splice(list_.begin(), list_, it->second);
+    T::Touch(it->first, &it->second->second);
+    return &it->second->second;
+  }
+
+  list_.push_front(Pair(address, { }));
+  map_[address] = list_.begin();
+  T::Touch(list_.begin()->first, &list_.begin()->second);
+
+  // Drop the last item in the list if we are
+  // over the size limit...
+  if (map_.size() > max_size_) {
+    auto last = list_.end();
+    map_.erase((--last)->first);
+    list_.pop_back();
+  }
+
+  return &map_[address]->second;
+}
+
 }  // namespace node
 
 #endif  // NODE_WANT_INTERNALS