Extract common Mask/Dart_Port settings of linux event handler implementation to eventhandler.h

dart/runtime/bin/eventhandler.h

Index: dart/runtime/bin/eventhandler.h
diff --git a/dart/runtime/bin/eventhandler.h b/dart/runtime/bin/eventhandler.h
index 70636bf80df43dd5128bacba69f7ed6ad7392b5d..34c5e750899c721c0fb7272cd62254469d004e25 100644
--- a/dart/runtime/bin/eventhandler.h
+++ b/dart/runtime/bin/eventhandler.h
@@ -6,8 +6,11 @@
 #define BIN_EVENTHANDLER_H_
 
 #include "bin/builtin.h"
+#include "bin/dartutils.h"
 #include "bin/isolate_data.h"
 
+#include "platform/hashmap.h"
+
 namespace dart {
 namespace bin {
 
@@ -44,6 +47,9 @@ enum MessageFlags {
     ((data & COMMAND_MASK) == (1 << command_bit))  // NOLINT
 #define IS_EVENT(data, event_bit) \
     ((data & EVENT_MASK) == (1 << event_bit))  // NOLINT
+#define IS_IO_EVENT(data) \
+    ((data & (1 << kInEvent | 1 << kOutEvent | 1 << kCloseEvent)) != 0 && \
+     (data & ~(1 << kInEvent | 1 << kOutEvent | 1 << kCloseEvent)) == 0)
 #define IS_LISTENING_SOCKET(data) \
     ((data & (1 << kListeningSocket)) != 0)  // NOLINT
 #define TOKEN_COUNT(data) (data & ((1 << kCloseCommand) - 1))
@@ -155,14 +161,43 @@ class CircularLinkedList {
     delete e;
   }
 
+  void Remove(T item) {
+    if (head_ == NULL) {
+      return;
+    } else if (head_ == head_->next_) {
+      if (head_->t == item) {
+        delete head_;
+        head_ = NULL;
+        return;
+      }
+    } else {
+      Entry *current = head_;
+      do {
+        if (current->t == item) {
+          Entry *next = current->next_;
+          Entry *prev = current->prev_;
+          prev->next_ = next;
+          next->prev_ = prev;
+          delete current;
+          return;
+        }
+        current = current->next_;
+      } while (current != head_);
+    }
+  }
+
+
   T head() const { return head_->t; }
 
-  bool HasHead() {
+  bool HasHead() const {
     return head_ != NULL;
   }
 
   void Rotate() {
-    head_ = head_->next_;
+    if (head_ != NULL) {
+      ASSERT(head_->next_ != NULL);
+      head_ = head_->next_;
+    }
   }
 
  private:
@@ -176,6 +211,335 @@ class CircularLinkedList {
   Entry* head_;
 };
 
+
+class DescriptorInfoBase {
+ public:
+  explicit DescriptorInfoBase(intptr_t fd) : fd_(fd) {
+    ASSERT(fd_ != -1);
+  }
+
+  virtual ~DescriptorInfoBase() {}
+
+  // The OS descriptor.
+  intptr_t fd() { return fd_; }
+
+  // Whether this descriptor refers to an underlying listening OS socket.
+  virtual bool IsListeningSocket() const = 0;
+
+  // Inserts or updates a new Dart_Port which is interested in events specified
+  // in `mask`.
+  virtual void SetPortAndMask(Dart_Port port, intptr_t mask) = 0;
+
+  // Removes a port from the interested listeners.
+  virtual void RemovePort(Dart_Port port) = 0;
+
+  // Returns a port to which `events_ready` can be sent to. It will also
+  // decrease the token count by 1 for this port.
+  virtual Dart_Port NextNotifyDartPort(intptr_t events_ready) = 0;
+
+  // Will post `data` to all known Dart_Ports. It will also decrease the token
+  // count by 1 for all ports.
+  virtual void NotifyAllDartPorts(uintptr_t events) = 0;
+
+  // Returns `count` tokens for the given port.
+  virtual void ReturnTokens(Dart_Port port, int count) = 0;
+
+  // Returns the union of event masks of all ports. If a port has a non-positive
+  // token count it's mask is assumed to be 0.
+  virtual intptr_t Mask() = 0;
+
+  // Closes this descriptor.
+  virtual void Close() = 0;
+
+ protected:
+  intptr_t fd_;
+};
+
+
+// Describes a OS descriptor (e.g. file descriptor on linux or HANDLE on
+// windows) which is connected to a single Dart_Port.
+//
+// Subclasses of this class can be e.g. connected tcp sockets.
+template<typename DI>
+class DescriptorInfoSingleMixin : public DI {
+ private:
+  static const int kTokenCount = 16;
+
+ public:
+  explicit DescriptorInfoSingleMixin(intptr_t fd)
+      : DI(fd), port_(0), tokens_(kTokenCount), mask_(0) {}
+
+  virtual ~DescriptorInfoSingleMixin() { }
+
+  virtual bool IsListeningSocket() const { return false; }
+
+  virtual void SetPortAndMask(Dart_Port port, intptr_t mask) {
+    ASSERT(port_ == 0 || port == port_);
+    port_ = port;
+    mask_ = mask;
+  }
+
+  virtual void RemovePort(Dart_Port port) {
+    // TODO(dart:io): Find out where we call RemovePort() with the invalid
+    // port. Afterwards remove the part in the ASSERT here.
+    ASSERT(port_ == 0 || port_ == port);
+    port_ = 0;
+    mask_ = 0;
+  }
+
+  virtual Dart_Port NextNotifyDartPort(intptr_t events_ready) {
+    ASSERT(IS_IO_EVENT(events_ready) ||
+           IS_EVENT(events_ready, kDestroyedEvent));
+    tokens_--;
+    return port_;
+  }
+
+  virtual void NotifyAllDartPorts(uintptr_t events) {
+    // Unexpected close or error events are the only ones we broadcast to all
+    // listeners and are the only ones where we do not count tokens.
+    ASSERT(IS_EVENT(events, kCloseEvent) ||
+           IS_EVENT(events, kErrorEvent));
+
+    if (port_ != 0) {
+      DartUtils::PostInt32(port_, events);
+    }
+    tokens_--;
+  }
+
+  virtual void ReturnTokens(Dart_Port port, int count) {
+    ASSERT(port_ == port);
+    ASSERT(tokens_ >= 0);
+    tokens_ += count;
+    ASSERT(tokens_ <= kTokenCount);
+  }
+
+  virtual intptr_t Mask() {
+    if (tokens_ <= 0) {
+      return 0;
+    }
+    return mask_;
+  }
+
+  virtual void Close() {
+    DI::Close();
+  }
+
+ private:
+  Dart_Port port_;
+  int tokens_;
+  intptr_t mask_;
+};
+
+
+// Describes a OS descriptor (e.g. file descriptor on linux or HANDLE on
+// windows) which is connected to multiple Dart_Port's.
+//
+// Subclasses of this class can be e.g. a listening socket which multiple
+// isolates are listening on.
+template<typename DI>
+class DescriptorInfoMultipleMixin : public DI {
+ 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);
+  }
+
+  static bool IsReadingMask(intptr_t mask) {
+    if (mask == (1 << kInEvent)) {
+      return true;
+    } else {
+      ASSERT(mask == 0);
+      return false;
+    }
+  }
+
+  struct PortEntry {
+    Dart_Port dart_port;
+    intptr_t is_reading;
+    intptr_t token_count;
+
+    bool IsReady() { return token_count > 0 && is_reading; }
+  };
+
+ public:
+  explicit DescriptorInfoMultipleMixin(intptr_t fd)
+      : DI(fd), tokens_map_(&SamePortValue, kTokenCount) {}
+
+  virtual ~DescriptorInfoMultipleMixin() {}
+
+  virtual bool IsListeningSocket() const { return true; }
+
+  virtual void SetPortAndMask(Dart_Port port, intptr_t mask) {
+    HashMap::Entry* entry = tokens_map_.Lookup(
+        GetHashmapKeyFromPort(port), GetHashmapHashFromPort(port), true);
+    PortEntry* pentry;
+    if (entry->value == NULL) {
+      pentry = new PortEntry();
+      pentry->dart_port = port;
+      pentry->token_count = kTokenCount;
+      pentry->is_reading = IsReadingMask(mask);
+      entry->value = reinterpret_cast<void*>(pentry);
+
+      if (pentry->IsReady()) {
+        active_readers_.Add(pentry);
+      }
+    } else {
+      pentry = reinterpret_cast<PortEntry*>(entry->value);
+      bool was_ready = pentry->IsReady();
+      pentry->is_reading = IsReadingMask(mask);
+      bool is_ready = pentry->IsReady();
+
+      if (was_ready && !is_ready) {
+        active_readers_.Remove(pentry);
+      } else if (!was_ready && is_ready) {
+        active_readers_.Add(pentry);
+      }
+    }
+
+#ifdef DEBUG
+    // To ensure that all readers are ready.
+    PortEntry* root = reinterpret_cast<PortEntry*>(active_readers_.head());
+
+    int ready_count = 0;
+    if (root != NULL) {
+      PortEntry* current = root;
+      do {
+        ASSERT(current->IsReady());
+        ready_count++;
+        active_readers_.Rotate();
+        current = active_readers_.head();
+      } while (current != root);
+    }
+    for (HashMap::Entry *entry = tokens_map_.Start();
+         entry != NULL;
+         entry = tokens_map_.Next(entry)) {
+      PortEntry* pentry = reinterpret_cast<PortEntry*>(entry->value);
+      if (pentry->IsReady()) {
+        ready_count--;
+      }
+    }
+    // Ensure all ready items are in `active_readers_`.
+    ASSERT(ready_count == 0);
+#endif
+  }
+
+  virtual void RemovePort(Dart_Port port) {
+    HashMap::Entry* entry = tokens_map_.Lookup(
+        GetHashmapKeyFromPort(port), GetHashmapHashFromPort(port), false);
+    if (entry != NULL) {
+      PortEntry* pentry = reinterpret_cast<PortEntry*>(entry->value);
+      if (pentry->IsReady()) {
+        active_readers_.Remove(pentry);
+      }
+      tokens_map_.Remove(
+          GetHashmapKeyFromPort(port), GetHashmapHashFromPort(port));
+      delete pentry;
+    } else {
+      // NOTE: This is a listening socket which has been immediately closed.
+      //
+      // If a listening socket is not listened on, the event handler does not
+      // know about it beforehand. So the first time the event handler knows
+      // about it, is when it is supposed to be closed. We therefore do nothing
+      // here.
+      //
+      // But whether to close it, depends on whether other isolates have it open
+      // as well or not.
+    }
+  }
+
+  virtual Dart_Port NextNotifyDartPort(intptr_t events_ready) {
+    // We're only sending `kInEvents` if there are multiple listeners (which is
+    // listening socktes).
+    ASSERT(IS_EVENT(events_ready, kInEvent) ||
+           IS_EVENT(events_ready, kDestroyedEvent));
+
+    if (active_readers_.HasHead()) {
+      PortEntry* pentry = reinterpret_cast<PortEntry*>(active_readers_.head());
+
+      // Update token count.
+      pentry->token_count--;
+      if (pentry->token_count <= 0) {
+        active_readers_.RemoveHead();
+      } else {
+        active_readers_.Rotate();
+      }
+
+      return pentry->dart_port;
+    }
+    return 0;
+  }
+
+  virtual void NotifyAllDartPorts(uintptr_t events) {
+    // Unexpected close or error events are the only ones we broadcast to all
+    // listeners and are the only ones where we do not count tokens.
+    ASSERT(IS_EVENT(events, kCloseEvent) ||
+           IS_EVENT(events, kErrorEvent));
+
+    for (HashMap::Entry *entry = tokens_map_.Start();
+         entry != NULL;
+         entry = tokens_map_.Next(entry)) {
+      PortEntry* pentry = reinterpret_cast<PortEntry*>(entry->value);
+      DartUtils::PostInt32(pentry->dart_port, events);
+
+      // Update token count.
+      bool was_ready = pentry->IsReady();
+      pentry->token_count--;
+
+      if (was_ready && pentry->token_count <= 0) {
+        active_readers_.Remove(pentry);
+      }
+    }
+  }
+
+  virtual void ReturnTokens(Dart_Port port, int count) {
+    HashMap::Entry* entry = tokens_map_.Lookup(
+        GetHashmapKeyFromPort(port), GetHashmapHashFromPort(port), false);
+    ASSERT(entry != NULL);
+
+    PortEntry* pentry = reinterpret_cast<PortEntry*>(entry->value);
+    bool was_ready = pentry->IsReady();
+    ASSERT(pentry->token_count >= 0);
+    pentry->token_count += count;
+    ASSERT(pentry->token_count <= kTokenCount);
+    bool is_ready = pentry->token_count > 0 && pentry->IsReady();
+    if (!was_ready && is_ready) {
+      active_readers_.Add(pentry);
+    }
+  }
+
+  virtual intptr_t Mask() {
+    if (active_readers_.HasHead()) {
+      return 1 << kInEvent;
+    }
+    return 0;
+  }
+
+  virtual void Close() {
+    DI::Close();
+  }
+
+ private:
+  // The [Dart_Port]s which are not paused (i.e. are interested in read events,
+  // i.e. `mask == (1 << kInEvent)`) and we have enough tokens to communicate
+  // with them.
+  CircularLinkedList<PortEntry *> active_readers_;
+
+  // A convenience mapping:
+  //   Dart_Port -> struct PortEntry { dart_port, mask, token_count }
+  HashMap tokens_map_;
+};
+
+
 }  // namespace bin
 }  // namespace dart