From 037e8307cfe1c057eb00c6179b171400a69db405 Mon Sep 17 00:00:00 2001
From: Steven Lee <slee@mozilla.com>
Date: Thu, 8 Nov 2012 14:35:02 -0500
Subject: [PATCH] Bug 805478 - Implement MessageLoopForIO::LineWatcher.
 r=dhylands

---
 ipc/chromium/src/base/message_loop.h          |  1 +
 .../src/base/message_pump_libevent.cc         | 43 +++++++++++++++++++
 ipc/chromium/src/base/message_pump_libevent.h | 35 +++++++++++++++
 3 files changed, 79 insertions(+)

diff --git a/ipc/chromium/src/base/message_loop.h b/ipc/chromium/src/base/message_loop.h
index 0dc02dafc529..fb954b037c35 100644
--- a/ipc/chromium/src/base/message_loop.h
+++ b/ipc/chromium/src/base/message_loop.h
@@ -509,6 +509,7 @@ class MessageLoopForIO : public MessageLoop {
   typedef base::MessagePumpLibevent::Watcher Watcher;
   typedef base::MessagePumpLibevent::FileDescriptorWatcher
       FileDescriptorWatcher;
+  typedef base::LineWatcher LineWatcher;
 
   enum Mode {
     WATCH_READ = base::MessagePumpLibevent::WATCH_READ,
diff --git a/ipc/chromium/src/base/message_pump_libevent.cc b/ipc/chromium/src/base/message_pump_libevent.cc
index 9f31dbbfbde9..b4670ed2a759 100644
--- a/ipc/chromium/src/base/message_pump_libevent.cc
+++ b/ipc/chromium/src/base/message_pump_libevent.cc
@@ -15,6 +15,7 @@
 #include "base/scoped_nsautorelease_pool.h"
 #include "base/scoped_ptr.h"
 #include "base/time.h"
+#include "nsDependentSubstring.h"
 #include "third_party/libevent/event.h"
 
 // Lifecycle of struct event
@@ -371,4 +372,46 @@ void MessagePumpLibevent::ScheduleDelayedWork(const Time& delayed_work_time) {
   delayed_work_time_ = delayed_work_time;
 }
 
+void LineWatcher::OnFileCanReadWithoutBlocking(int aFd)
+{
+  ssize_t length = 0;
+
+  while (true) {
+    length = read(aFd, mReceiveBuffer.get(), mBufferSize - mReceivedIndex);
+    DCHECK(length <= ssize_t(mBufferSize - mReceivedIndex));
+    if (length <= 0) {
+      if (length < 0) {
+        if (errno == EINTR) {
+          continue; // retry system call when interrupted
+        }
+        if (errno == EAGAIN || errno == EWOULDBLOCK) {
+          return; // no data available: return and re-poll
+        }
+        DLOG(ERROR) << "Can't read from fd, error " << errno;
+      } else {
+        DLOG(ERROR) << "End of file";
+      }
+      // At this point, assume that we can't actually access
+      // the socket anymore, and indicate an error.
+      OnError();
+      mReceivedIndex = 0;
+      return;
+    }
+
+    while (length-- > 0) {
+      DCHECK(mReceivedIndex < mBufferSize);
+      if (mReceiveBuffer[mReceivedIndex] == mTerminator) {
+        nsDependentCSubstring message(mReceiveBuffer.get(), mReceivedIndex);
+        OnLineRead(aFd, message);
+        if (length > 0) {
+          DCHECK(mReceivedIndex < (mBufferSize - 1));
+          memmove(&mReceiveBuffer[0], &mReceiveBuffer[mReceivedIndex + 1], length);
+        }
+        mReceivedIndex = 0;
+      } else {
+        mReceivedIndex++;
+      }
+    }
+  }
+}
 }  // namespace base
diff --git a/ipc/chromium/src/base/message_pump_libevent.h b/ipc/chromium/src/base/message_pump_libevent.h
index 6b1084499304..04ecb832df59 100644
--- a/ipc/chromium/src/base/message_pump_libevent.h
+++ b/ipc/chromium/src/base/message_pump_libevent.h
@@ -7,11 +7,14 @@
 
 #include "base/message_pump.h"
 #include "base/time.h"
+#include "nsAutoPtr.h"
 
 // Declare structs we need from libevent.h rather than including it
 struct event_base;
 struct event;
 
+class nsDependentCSubstring;
+
 namespace base {
 
 // Class to monitor sockets and issue callbacks when sockets are ready for I/O
@@ -175,6 +178,38 @@ class MessagePumpLibevent : public MessagePump {
   DISALLOW_COPY_AND_ASSIGN(MessagePumpLibevent);
 };
 
+/**
+ *  LineWatcher overrides OnFileCanReadWithoutBlocking. It separates the read
+ *  data by mTerminator and passes each line to OnLineRead.
+ */
+class LineWatcher : public MessagePumpLibevent::Watcher
+{
+public:
+  LineWatcher(char aTerminator, int aBufferSize) : mReceivedIndex(0),
+    mBufferSize(aBufferSize),
+    mTerminator(aTerminator)
+  {
+    mReceiveBuffer = new char[mBufferSize];
+  }
+
+  ~LineWatcher() {}
+
+protected:
+  /**
+   * OnError will be called when |read| returns error. Derived class should
+   * implement this function to handle error cases when needed.
+   */
+  virtual void OnError() {}
+  virtual void OnLineRead(int aFd, nsDependentCSubstring& aMessage) = 0;
+  virtual void OnFileCanWriteWithoutBlocking(int /* aFd */) {}
+private:
+  virtual void OnFileCanReadWithoutBlocking(int aFd) MOZ_FINAL;
+
+  nsAutoPtr<char> mReceiveBuffer;
+  int mReceivedIndex;
+  int mBufferSize;
+  char mTerminator;
+};
 }  // namespace base
 
 #endif  // BASE_MESSAGE_PUMP_LIBEVENT_H_