ipc/glue/MiniTransceiver.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
   2 /* vim: set ts=8 sts=4 et sw=4 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6 #ifndef __MINITRANSCEIVER_H_
   7 #define __MINITRANSCEIVER_H_
   8
   9 #include "chrome/common/ipc_message.h"
  10 #include "mozilla/Assertions.h"
  11
  12 struct msghdr;
  13
  14 namespace mozilla {
  15 namespace ipc {
  16
  17 enum class DataBufferClear { None, AfterReceiving };
  18
  19 /**
  20  * This simple implementation handles the transmissions of IPC
  21  * messages.
  22  *
  23  * It works according to a strict request-response paradigm, no
  24  * concurrent messaging is allowed. Sending a message from A to B must
  25  * be followed by another one from B to A. Because of this we don't
  26  * need to handle data crossing the boundaries of a
  27  * message. Transmission is done via blocking I/O to avoid the
  28  * complexity of asynchronous I/O.
  29  */
  30 class MiniTransceiver {
  31  public:
  32   /**
  33    * \param aFd should be a blocking, no O_NONBLOCK, fd.
  34    * \param aClearDataBuf is true to clear data buffers after
  35    *                      receiving a message.
  36    */
  37   explicit MiniTransceiver(
  38       int aFd, DataBufferClear aDataBufClear = DataBufferClear::None);
  39
  40   bool Send(IPC::Message& aMsg);
  41   inline bool SendInfallible(IPC::Message& aMsg, const char* aCrashMessage) {
  42     bool Ok = Send(aMsg);
  43     if (!Ok) {
  44       MOZ_CRASH_UNSAFE(aCrashMessage);
  45     }
  46     return Ok;
  47   }
  48
  49   /**
  50    * \param aMsg will hold the content of the received message.
  51    * \return false if the fd is closed or with an error.
  52    */
  53   bool Recv(IPC::Message& aMsg);
  54   inline bool RecvInfallible(IPC::Message& aMsg, const char* aCrashMessage) {
  55     bool Ok = Recv(aMsg);
  56     if (!Ok) {
  57       MOZ_CRASH_UNSAFE(aCrashMessage);
  58     }
  59     return Ok;
  60   }
  61
  62   int GetFD() { return mFd; }
  63
  64  private:
  65   /**
  66    * Set control buffer to make file descriptors ready to be sent
  67    * through a socket.
  68    */
  69   void PrepareFDs(msghdr* aHdr, IPC::Message& aMsg);
  70   /**
  71    * Collect buffers of the message and make them ready to be sent.
  72    *
  73    * \param aHdr is the structure going to be passed to sendmsg().
  74    * \param aMsg is the Message to send.
  75    */
  76   size_t PrepareBuffers(msghdr* aHdr, IPC::Message& aMsg);
  77   /**
  78    * Collect file descriptors received.
  79    *
  80    * \param aAllFds is where to store file descriptors.
  81    * \param aMaxFds is how many file descriptors can be stored in aAllFds.
  82    * \return the number of received file descriptors.
  83    */
  84   unsigned RecvFDs(msghdr* aHdr, int* aAllFds, unsigned aMaxFds);
  85   /**
  86    * Received data from the socket.
  87    *
  88    * \param aDataBuf is where to store the data from the socket.
  89    * \param aBufSize is the size of the buffer.
  90    * \param aMsgSize returns how many bytes were readed from the socket.
  91    * \param aFdsBuf is the buffer to return file desriptors received.
  92    * \param aMaxFds is the number of file descriptors that can be held.
  93    * \param aNumFds returns the number of file descriptors received.
  94    * \return true if sucess, or false for error.
  95    */
  96   bool RecvData(char* aDataBuf, size_t aBufSize, uint32_t* aMsgSize,
  97                 int* aFdsBuf, unsigned aMaxFds, unsigned* aNumFds);
  98
  99   int mFd;  // The file descriptor of the socket for IPC.
 100
 101 #ifdef DEBUG
 102   enum State {
 103     STATE_NONE,
 104     STATE_SENDING,
 105     STATE_RECEIVING,
 106   };
 107   State mState;
 108 #endif
 109
 110   // Clear all received data in temp buffers to avoid data leaking.
 111   DataBufferClear mDataBufClear;
 112 };
 113
 114 }  // namespace ipc
 115 }  // namespace mozilla
 116
 117 #endif  // __MINITRANSCEIVER_H_