Add support for cloning server-sockets.

runtime/bin/eventhandler_linux.h

Index: runtime/bin/eventhandler_linux.h
diff --git a/runtime/bin/eventhandler_linux.h b/runtime/bin/eventhandler_linux.h
index f6f3f9a2ac6f3885e76cbfee8c0f2b379778b8a6..1a8d968a3b218785e24eb886842756fbcc8120ae 100644
--- a/runtime/bin/eventhandler_linux.h
+++ b/runtime/bin/eventhandler_linux.h
@@ -28,13 +28,75 @@ class InterruptMessage {
   int64_t data;
 };
 
+template<typename T>
+class CircularLinkedList {
+ public:
+  CircularLinkedList() : head_(NULL) {}
+
+  // Returns true if the list was empty.
+  bool Add(T t) {
+    Entry* e = new Entry(t);
+    if (head_ == NULL) {
+      // Empty list, make e head, and point to itself.
+      e->next_ = e;
+      e->prev_ = e;
+      head_ = e;
+      return true;
+    } else {
+      // Insert e as the last element in the list.
+      e->prev_ = head_->prev_;
+      e->next_ = head_;
+      e->prev_->next_ = e;
+      head_->prev_ = e;
+      return false;
+    }
+  }
+
+  void RemoveHead() {
+    Entry* e = head_;
+    if (e->next_ == e) {
+      head_ = NULL;
+    } else {
+      e->prev_->next_ = e->next_;
+      e->next_->prev_ = e->prev_;
+      head_ = e->next_;
+    }
+    delete e;
+  }
+
+  T head() const { return head_->t; }
+
+  bool HasHead() {
+    return head_ != NULL;
+  }
+
+  void Rotate() {
+    head_ = head_->next_;
+  }
+
+ private:
+  struct Entry {
+    explicit Entry(const T& t) : t(t) {}
+    const T t;
+    Entry* next_;
+    Entry* prev_;
+  };
+
+  Entry* head_;
+};
+
 
+class ListeningSocketData;
 class SocketData {
  public:
-  explicit SocketData(intptr_t fd) : fd_(fd), port_(0), mask_(0), tokens_(16) {
+  explicit SocketData(intptr_t fd)
+      : fd_(fd), port_(0), mask_(0), tokens_(16) {
     ASSERT(fd_ != -1);
   }
 
+  virtual ~SocketData() {
+  }
+
   intptr_t GetPollEvents();
 
   void Close() {
@@ -44,32 +106,46 @@ class SocketData {
     fd_ = -1;
   }
 
-  void SetPortAndMask(Dart_Port port, intptr_t mask) {
+  void SetMask(intptr_t mask) {
     ASSERT(fd_ != -1);
-    port_ = port;
     mask_ = mask;
   }
 
   intptr_t fd() { return fd_; }
-  Dart_Port port() { return port_; }
+  virtual Dart_Port port() { return port_; }
 
-  bool IsListeningSocket() { return (mask_ & (1 << kListeningSocket)) != 0; }
+  virtual bool IsListeningSocket() const { return false; }
+
+  virtual bool AddPort(Dart_Port port) {
+    ASSERT(port_ == 0);
+    port_ = port;
+    return true;
+  }
+
+  virtual bool RemovePort(Dart_Port port) {
+    ASSERT(port_ == 0 || port_ == port);
+    return true;
+  }
 
   // Returns true if the last token was taken.
-  bool TakeToken() {
+  virtual bool TakeToken() {
     ASSERT(tokens_ > 0);
     tokens_--;
     return tokens_ == 0;
   }
 
   // Returns true if the tokens was 0 before adding.
-  bool ReturnToken() {
+  virtual bool ReturnToken(Dart_Port port, int count) {
+    ASSERT(port_ == port);
     ASSERT(tokens_ >= 0);
-    tokens_++;
-    return tokens_ == 1;
+    bool was_empty = tokens_ == 0;
+    tokens_ += count;
+    return was_empty;
   }
 
- private:
+  bool HasTokens() const { return tokens_ > 0; }
+
+ protected:
   intptr_t fd_;
   Dart_Port port_;
   intptr_t mask_;
@@ -77,6 +153,108 @@ class SocketData {
 };
 
 
+class ListeningSocketData : public SocketData {
+ private:
+  static const int kTokenCount = 4;
+
+  static bool SamePortValue(void* key1, void* key2) {
+    return reinterpret_cast<Dart_Port>(key1) ==
+        reinterpret_cast<Dart_Port>(key2);
+  }
+
+  static uint32_t GetHashmapHashFromPort(Dart_Port port) {
+    return static_cast<uint32_t>(port & 0xFFFFFFFF);
+  }
+
+  static void* GetHashmapKeyFromPort(Dart_Port port) {
+    return reinterpret_cast<void*>(port);
+  }
+
+ public:
+  explicit ListeningSocketData(intptr_t fd)
+      : SocketData(fd),
+        tokens_map_(&SamePortValue, 4) {}
+
+  bool IsListeningSocket() const { return true; }
+
+  bool AddPort(Dart_Port port) {
+    HashMap::Entry* entry = tokens_map_.Lookup(
+        GetHashmapKeyFromPort(port), GetHashmapHashFromPort(port), true);
+    entry->value = reinterpret_cast<void*>(kTokenCount);
+    return live_ports_.Add(port);
+  }
+
+  virtual bool RemovePort(Dart_Port port) {
+    HashMap::Entry* entry = tokens_map_.Lookup(
+        GetHashmapKeyFromPort(port), GetHashmapHashFromPort(port), false);
+    ASSERT(entry != NULL);
+    intptr_t tokens = reinterpret_cast<intptr_t>(entry->value);
+    if (tokens == 0) {
+      while (idle_ports_.head() != port) {
+        idle_ports_.Rotate();
+      }
+      idle_ports_.RemoveHead();
+    } else {
+      while (live_ports_.head() != port) {
+        live_ports_.Rotate();
+      }
+      live_ports_.RemoveHead();
+    }
+    tokens_map_.Remove(
+        GetHashmapKeyFromPort(port), GetHashmapHashFromPort(port));
+    return !live_ports_.HasHead();
+  }
+
+  bool TakeToken() {
+    ASSERT(live_ports_.HasHead());
+    Dart_Port port = live_ports_.head();
+    HashMap::Entry* entry = tokens_map_.Lookup(
+        GetHashmapKeyFromPort(port), GetHashmapHashFromPort(port), false);
+    ASSERT(entry != NULL);
+    intptr_t tokens = reinterpret_cast<intptr_t>(entry->value);
+    tokens--;
+    entry->value = reinterpret_cast<void*>(tokens);
+    if (tokens == 0) {
+      live_ports_.RemoveHead();
+      idle_ports_.Add(port);
+      if (!live_ports_.HasHead()) {
+        return true;
+      }
+    } else {
+      live_ports_.Rotate();
+    }
+    return false;
+  }
+
+  Dart_Port port() { return live_ports_.head(); }
+
+  bool ReturnToken(Dart_Port port, int count) {
+    HashMap::Entry* entry = tokens_map_.Lookup(
+        GetHashmapKeyFromPort(port), GetHashmapHashFromPort(port), false);
+    ASSERT(entry != NULL);
+    intptr_t tokens = reinterpret_cast<intptr_t>(entry->value);
+    tokens += count;
+    entry->value = reinterpret_cast<void*>(tokens);
+    if (tokens == count) {
+      // Return to live_ports_.
+      while (idle_ports_.head() != port) {
+        idle_ports_.Rotate();
+      }
+      idle_ports_.RemoveHead();
+      bool was_empty = !live_ports_.HasHead();
+      live_ports_.Add(port);
+      return was_empty;
+    }
+    return false;
+  }
+
+ private:
+  CircularLinkedList<Dart_Port> live_ports_;
+  CircularLinkedList<Dart_Port> idle_ports_;
+  HashMap tokens_map_;
+};
+
+
 class EventHandlerImplementation {
  public:
   EventHandlerImplementation();
@@ -84,7 +262,7 @@ class EventHandlerImplementation {
 
   // Gets the socket data structure for a given file
   // descriptor. Creates a new one if one is not found.
-  SocketData* GetSocketData(intptr_t fd);
+  SocketData* GetSocketData(intptr_t fd, bool is_listening);
   void SendData(intptr_t id, Dart_Port dart_port, int64_t data);
   void Start(EventHandler* handler);
   void Shutdown();