text: /*
   * Copyright 2014 Facebook, Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  #pragma once
  
  #include <sys/types.h>
  #include <sys/socket.h>
  #include <glog/logging.h>
  #include <folly/SocketAddress.h>
  #include <folly/io/ShutdownSocketSet.h>
  #include <folly/io/IOBuf.h>
  #include <folly/io/async/AsyncTimeout.h>
  #include <folly/io/async/AsyncSocketException.h>
  #include <folly/io/async/AsyncTransport.h>
  #include <folly/io/async/EventHandler.h>
  #include <folly/io/async/DelayedDestruction.h>
  
  #include <memory>
  #include <map>
  
  namespace folly {
  
  /**
   * A class for performing asynchronous I/O on a socket.
   *
   * AsyncSocket allows users to asynchronously wait for data on a socket, and
   * to asynchronously send data.
   *
   * The APIs for reading and writing are intentionally asymmetric.  Waiting for
   * data to read is a persistent API: a callback is installed, and is notified
   * whenever new data is available.  It continues to be notified of new events
   * until it is uninstalled.
   *
   * AsyncSocket does not provide read timeout functionality, because it
   * typically cannot determine when the timeout should be active.  Generally, a
   * timeout should only be enabled when processing is blocked waiting on data
   * from the remote endpoint.  For server sockets, the timeout should not be
   * active if the server is currently processing one or more outstanding
   * requests for this socket.  For client sockets, the timeout should not be
   * active if there are no requests pending on the socket.  Additionally, if a
   * client has multiple pending requests, it will ususally want a separate
   * timeout for each request, rather than a single read timeout.
   *
   * The write API is fairly intuitive: a user can request to send a block of
   * data, and a callback will be informed once the entire block has been
   * transferred to the kernel, or on error.  AsyncSocket does provide a send
   * timeout, since most callers want to give up if the remote end stops
   * responding and no further progress can be made sending the data.
   */
  
  class AsyncSocket : virtual public AsyncTransportWrapper {
   public:
    typedef std::unique_ptr<AsyncSocket, Destructor> UniquePtr;
  
    class ConnectCallback {
     public:
      virtual ~ConnectCallback() {}
  
      /**
       * connectSuccess() will be invoked when the connection has been
       * successfully established.
       */
      virtual void connectSuccess() noexcept = 0;
  
      /**
       * connectErr() will be invoked if the connection attempt fails.
       *
       * @param ex        An exception describing the error that occurred.
       */
      virtual void connectErr(const AsyncSocketException& ex)
        noexcept = 0;
    };
  
    explicit AsyncSocket();
    /**
     * Create a new unconnected AsyncSocket.
     *
     * connect() must later be called on this socket to establish a connection.
     */
    explicit AsyncSocket(EventBase* evb);
  
    void setShutdownSocketSet(ShutdownSocketSet* ss);
  
    /**
     * Create a new AsyncSocket and begin the connection process.
     *
     * @param evb             EventBase that will manage this socket.
     * @param address         The address to connect to.
     * @param connectTimeout  Optional timeout in milliseconds for the connection
     *                        attempt.
     */
    AsyncSocket(EventBase* evb,
                 const folly::SocketAddress& address,
                 uint32_t connectTimeout = 0);
  
    /**
     * Create a new AsyncSocket and begin the connection process.
     *
     * @param evb             EventBase that will manage this socket.
     * @param ip              IP address to connect to (dotted-quad).
     * @param port            Destination port in host byte order.
     * @param connectTimeout  Optional timeout in milliseconds for the connection
     *                        attempt.
     */
    AsyncSocket(EventBase* evb,
                 const std::string& ip,
                 uint16_t port,
                 uint32_t connectTimeout = 0);
  
    /**
     * Create a AsyncSocket from an already connected socket file descriptor.
     *
     * Note that while AsyncSocket enables TCP_NODELAY for sockets it creates
     * when connecting, it does not change the socket options when given an
     * existing file descriptor.  If callers want TCP_NODELAY enabled when using
     * this version of the constructor, they need to explicitly call
     * setNoDelay(true) after the constructor returns.
     *
     * @param evb EventBase that will manage this socket.
     * @param fd  File descriptor to take over (should be a connected socket).
     */
    AsyncSocket(EventBase* evb, int fd);
  
    /**
     * Helper function to create a shared_ptr<AsyncSocket>.
     *
     * This passes in the correct destructor object, since AsyncSocket's
     * destructor is protected and cannot be invoked directly.
     */
    static std::shared_ptr<AsyncSocket> newSocket(EventBase* evb) {
      return std::shared_ptr<AsyncSocket>(new AsyncSocket(evb),
                                             Destructor());
    }
  
    /**
     * Helper function to create a shared_ptr<AsyncSocket>.
     */
    static std::shared_ptr<AsyncSocket> newSocket(
        EventBase* evb,
        const folly::SocketAddress& address,
        uint32_t connectTimeout = 0) {
      return std::shared_ptr<AsyncSocket>(
          new AsyncSocket(evb, address, connectTimeout),
          Destructor());
    }
  
    /**
     * Helper function to create a shared_ptr<AsyncSocket>.
     */
    static std::shared_ptr<AsyncSocket> newSocket(
        EventBase* evb,
        const std::string& ip,
        uint16_t port,
        uint32_t connectTimeout = 0) {
      return std::shared_ptr<AsyncSocket>(
          new AsyncSocket(evb, ip, port, connectTimeout),
          Destructor());
    }
  
    /**
     * Helper function to create a shared_ptr<AsyncSocket>.
     */
    static std::shared_ptr<AsyncSocket> newSocket(EventBase* evb, int fd) {
      return std::shared_ptr<AsyncSocket>(new AsyncSocket(evb, fd),
                                             Destructor());
    }
  
    /**
     * Destroy the socket.
     *
     * AsyncSocket::destroy() must be called to destroy the socket.
     * The normal destructor is private, and should not be invoked directly.
     * This prevents callers from deleting a AsyncSocket while it is invoking a
     * callback.
     */
    virtual void destroy();
  
    /**
     * Get the EventBase used by this socket.
     */
    EventBase* getEventBase() const override {
      return eventBase_;
    }
  
    /**
     * Get the file descriptor used by the AsyncSocket.
     */
    virtual int getFd() const {
      return fd_;
    }
  
    /**
     * Extract the file descriptor from the AsyncSocket.
     *
     * This will immediately cause any installed callbacks to be invoked with an
     * error.  The AsyncSocket may no longer be used after the file descriptor
     * has been extracted.
     *
     * Returns the file descriptor.  The caller assumes ownership of the
     * descriptor, and it will not be closed when the AsyncSocket is destroyed.
     */
    virtual int detachFd();
  
    /**
     * Uniquely identifies a handle to a socket option value. Each
     * combination of level and option name corresponds to one socket
     * option value.
     */
    class OptionKey {
     public:
      bool operator<(const OptionKey& other) const {
        if (level == other.level) {
          return optname < other.optname;
        }
        return level < other.level;
      }
      int apply(int fd, int val) const {
        return setsockopt(fd, level, optname, &val, sizeof(val));
      }
      int level;
      int optname;
    };
  
    // Maps from a socket option key to its value
    typedef std::map<OptionKey, int> OptionMap;
  
    static const OptionMap emptyOptionMap;
    static const folly::SocketAddress anyAddress;
  
    /**
     * Initiate a connection.
     *
     * @param callback  The callback to inform when the connection attempt
     *                  completes.
     * @param address   The address to connect to.
     * @param timeout   A timeout value, in milliseconds.  If the connection
     *                  does not succeed within this period,
     *                  callback->connectError() will be invoked.
     */
    virtual void connect(ConnectCallback* callback,
                 const folly::SocketAddress& address,
                 int timeout = 0,
                 const OptionMap &options = emptyOptionMap,
                 const folly::SocketAddress& bindAddr = anyAddress
                 ) noexcept;
    void connect(ConnectCallback* callback, const std::string& ip, uint16_t port,
                 int timeout = 00,
                 const OptionMap &options = emptyOptionMap) noexcept;
  
    /**
     * If a connect request is in-flight, cancels it and closes the socket
     * immediately. Otherwise, this is a no-op.
     *
     * This does not invoke any connection related callbacks. Call this to
     * prevent any connect callback while cleaning up, etc.
     */
    void cancelConnect();
  
    /**
     * Set the send timeout.
     *
     * If write requests do not make any progress for more than the specified
     * number of milliseconds, fail all pending writes and close the socket.
     *
     * If write requests are currently pending when setSendTimeout() is called,
     * the timeout interval is immediately restarted using the new value.
     *
     * (See the comments for AsyncSocket for an explanation of why AsyncSocket
     * provides setSendTimeout() but not setRecvTimeout().)
     *
     * @param milliseconds  The timeout duration, in milliseconds.  If 0, no
     *                      timeout will be used.
     */
    void setSendTimeout(uint32_t milliseconds) override;
  
    /**
     * Get the send timeout.
     *
     * @return Returns the current send timeout, in milliseconds.  A return value
     *         of 0 indicates that no timeout is set.
     */
    uint32_t getSendTimeout() const override {
      return sendTimeout_;
    }
  
    /**
     * Set the maximum number of reads to execute from the underlying
     * socket each time the EventBase detects that new ingress data is
     * available. The default is unlimited, but callers can use this method
     * to limit the amount of data read from the socket per event loop
     * iteration.
     *
     * @param maxReads  Maximum number of reads per data-available event;
     *                  a value of zero means unlimited.
     */
    void setMaxReadsPerEvent(uint16_t maxReads) {
      maxReadsPerEvent_ = maxReads;
    }
  
    /**
     * Get the maximum number of reads this object will execute from
     * the underlying socket each time the EventBase detects that new
     * ingress data is available.
     *
     * @returns Maximum number of reads per data-available event; a value
     *          of zero means unlimited.
     */
    uint16_t getMaxReadsPerEvent() const {
      return maxReadsPerEvent_;
    }
  
    // Read and write methods
    void setReadCB(ReadCallback* callback) override;
    ReadCallback* getReadCallback() const override;
  
    void write(WriteCallback* callback, const void* buf, size_t bytes,
               WriteFlags flags = WriteFlags::NONE) override;
    void writev(WriteCallback* callback, const iovec* vec, size_t count,
                WriteFlags flags = WriteFlags::NONE) override;
    void writeChain(WriteCallback* callback,
                    std::unique_ptr<folly::IOBuf>&& buf,
                    WriteFlags flags = WriteFlags::NONE) override;
  
    // Methods inherited from AsyncTransport
    void close() override;
    void closeNow() override;
    void closeWithReset() override;
    void shutdownWrite() override;
    void shutdownWriteNow() override;
  
    bool readable() const override;
    bool isPending() const override;
    virtual bool hangup() const;
    bool good() const override;
    bool error() const override;
    void attachEventBase(EventBase* eventBase) override;
    void detachEventBase() override;
    bool isDetachable() const override;
  
    void getLocalAddress(
      folly::SocketAddress* address) const override;
    void getPeerAddress(
      folly::SocketAddress* address) const override;
  
    bool isEorTrackingEnabled() const override { return false; }
  
    void setEorTracking(bool track) override {}
  
    bool connecting() const override {
      return (state_ == StateEnum::CONNECTING);
    }
  
    size_t getAppBytesWritten() const override {
      return appBytesWritten_;
    }
  
    size_t getRawBytesWritten() const override {
      return getAppBytesWritten();
    }
  
    size_t getAppBytesReceived() const override {
      return appBytesReceived_;
    }
  
    size_t getRawBytesReceived() const override {
      return getAppBytesReceived();
    }
  
    // Methods controlling socket options
  
    /**
     * Force writes to be transmitted immediately.
     *
     * This controls the TCP_NODELAY socket option.  When enabled, TCP segments
     * are sent as soon as possible, even if it is not a full frame of data.
     * When disabled, the data may be buffered briefly to try and wait for a full
     * frame of data.
     *
     * By default, TCP_NODELAY is enabled for AsyncSocket objects.
     *
     * This method will fail if the socket is not currently open.
     *
     * @return Returns 0 if the TCP_NODELAY flag was successfully updated,
     *         or a non-zero errno value on error.
     */
    int setNoDelay(bool noDelay);
  
    /*
     * Set the Flavor of Congestion Control to be used for this Socket
     * Please check '/lib/modules/<kernel>/kernel/net/ipv4' for tcp_*.ko
     * first to make sure the module is available for plugging in
     * Alternatively you can choose from net.ipv4.tcp_allowed_congestion_control
     */
    int setCongestionFlavor(const std::string &cname);
  
    /*
     * Forces ACKs to be sent immediately
     *
     * @return Returns 0 if the TCP_QUICKACK flag was successfully updated,
     *         or a non-zero errno value on error.
     */
    int setQuickAck(bool quickack);
  
    /**
     * Set the send bufsize
     */
    int setSendBufSize(size_t bufsize);
  
    /**
     * Set the recv bufsize
     */
    int setRecvBufSize(size_t bufsize);
  
    /**
     * Sets a specific tcp personality
     * Available only on kernels 3.2 and greater
     */
    #define SO_SET_NAMESPACE        41
    int setTCPProfile(int profd);
  
  
    /**
     * Generic API for reading a socket option.
     *
     * @param level     same as the "level" parameter in getsockopt().
     * @param optname   same as the "optname" parameter in getsockopt().
     * @param optval    pointer to the variable in which the option value should
     *                  be returned.
     * @param optlen    value-result argument, initially containing the size of
     *                  the buffer pointed to by optval, and modified on return
     *                  to indicate the actual size of the value returned.
     * @return          same as the return value of getsockopt().
     */
    template <typename T>
    int getSockOpt(int level, int optname, T* optval, socklen_t* optlen) {
      return getsockopt(fd_, level, optname, (void*) optval, optlen);
    }
  
    /**
     * Generic API for setting a socket option.
     *
     * @param level     same as the "level" parameter in getsockopt().
     * @param optname   same as the "optname" parameter in getsockopt().
     * @param optval    the option value to set.
     * @return          same as the return value of setsockopt().
     */
    template <typename T>
    int setSockOpt(int  level,  int  optname,  const T *optval) {
      return setsockopt(fd_, level, optname, optval, sizeof(T));
    }
  
    enum class StateEnum : uint8_t {
      UNINIT,
      CONNECTING,
      ESTABLISHED,
      CLOSED,
      ERROR
    };
  
   protected:
    enum ReadResultEnum {
      READ_EOF = 0,
      READ_ERROR = -1,
      READ_BLOCKING = -2,
    };
  
    /**
     * Protected destructor.
     *
     * Users of AsyncSocket must never delete it directly.  Instead, invoke
     * destroy() instead.  (See the documentation in DelayedDestruction.h for
     * more details.)
     */
    ~AsyncSocket();
  
    friend std::ostream& operator << (std::ostream& os, const StateEnum& state);
  
    enum ShutdownFlags {
      /// shutdownWrite() called, but we are still waiting on writes to drain
      SHUT_WRITE_PENDING = 0x01,
      /// writes have been completely shut down
      SHUT_WRITE = 0x02,
      /**
       * Reads have been shutdown.
       *
       * At the moment we don't distinguish between remote read shutdown
       * (received EOF from the remote end) and local read shutdown.  We can
       * only receive EOF when a read callback is set, and we immediately inform
       * it of the EOF.  Therefore there doesn't seem to be any reason to have a
       * separate state of "received EOF but the local side may still want to
       * read".
       *
       * We also don't currently provide any API for only shutting down the read
       * side of a socket.  (This is a no-op as far as TCP is concerned, anyway.)
       */
      SHUT_READ = 0x04,
    };
  
    class WriteRequest;
  
    class WriteTimeout : public AsyncTimeout {
     public:
      WriteTimeout(AsyncSocket* socket, EventBase* eventBase)
        : AsyncTimeout(eventBase)
        , socket_(socket) {}
  
      virtual void timeoutExpired() noexcept {
        socket_->timeoutExpired();
      }
  
     private:
      AsyncSocket* socket_;
    };
  
    class IoHandler : public EventHandler {
     public:
      IoHandler(AsyncSocket* socket, EventBase* eventBase)
        : EventHandler(eventBase, -1)
        , socket_(socket) {}
      IoHandler(AsyncSocket* socket, EventBase* eventBase, int fd)
        : EventHandler(eventBase, fd)
        , socket_(socket) {}
  
      virtual void handlerReady(uint16_t events) noexcept {
        socket_->ioReady(events);
      }
  
     private:
      AsyncSocket* socket_;
    };
  
    void init();
  
    // event notification methods
    void ioReady(uint16_t events) noexcept;
    virtual void checkForImmediateRead() noexcept;
    virtual void handleInitialReadWrite() noexcept;
    virtual void handleRead() noexcept;
    virtual void handleWrite() noexcept;
    virtual void handleConnect() noexcept;
    void timeoutExpired() noexcept;
  
    /**
     * Attempt to read from the socket.
     *
     * @param buf      The buffer to read data into.
     * @param buflen   The length of the buffer.
     *
     * @return Returns the number of bytes read, or READ_EOF on EOF, or
     * READ_ERROR on error, or READ_BLOCKING if the operation will
     * block.
     */
    virtual ssize_t performRead(void* buf, size_t buflen);
  
    /**
     * Populate an iovec array from an IOBuf and attempt to write it.
     *
     * @param callback Write completion/error callback.
     * @param vec      Target iovec array; caller retains ownership.
     * @param count    Number of IOBufs to write, beginning at start of buf.
     * @param buf      Chain of iovecs.
     * @param flags    set of flags for the underlying write calls, like cork
     */
    void writeChainImpl(WriteCallback* callback, iovec* vec,
                        size_t count, std::unique_ptr<folly::IOBuf>&& buf,
                        WriteFlags flags);
  
    /**
     * Write as much data as possible to the socket without blocking,
     * and queue up any leftover data to send when the socket can
     * handle writes again.
     *
     * @param callback The callback to invoke when the write is completed.
     * @param vec      Array of buffers to write; this method will make a
     *                 copy of the vector (but not the buffers themselves)
     *                 if the write has to be completed asynchronously.
     * @param count    Number of elements in vec.
     * @param buf      The IOBuf that manages the buffers referenced by
     *                 vec, or a pointer to nullptr if the buffers are not
     *                 associated with an IOBuf.  Note that ownership of
     *                 the IOBuf is transferred here; upon completion of
     *                 the write, the AsyncSocket deletes the IOBuf.
     * @param flags    Set of write flags.
     */
    void writeImpl(WriteCallback* callback, const iovec* vec, size_t count,
                   std::unique_ptr<folly::IOBuf>&& buf,
                   WriteFlags flags = WriteFlags::NONE);
  
    /**
     * Attempt to write to the socket.
     *
     * @param vec             The iovec array pointing to the buffers to write.
     * @param count           The length of the iovec array.
     * @param flags           Set of write flags.
     * @param countWritten    On return, the value pointed to by this parameter
     *                          will contain the number of iovec entries that were
     *                          fully written.
     * @param partialWritten  On return, the value pointed to by this parameter
     *                          will contain the number of bytes written in the
     *                          partially written iovec entry.
     *
     * @return Returns the total number of bytes written, or -1 on error.  If no
     *     data can be written immediately, 0 is returned.
     */
    virtual ssize_t performWrite(const iovec* vec, uint32_t count,
                                 WriteFlags flags, uint32_t* countWritten,
                                 uint32_t* partialWritten);
  
    bool updateEventRegistration();
  
    /**
     * Update event registration.
     *
     * @param enable Flags of events to enable. Set it to 0 if no events
     * need to be enabled in this call.
     * @param disable Flags of events
     * to disable. Set it to 0 if no events need to be disabled in this
     * call.
     *
     * @return true iff the update is successful.
     */
    bool updateEventRegistration(uint16_t enable, uint16_t disable);
  
    // Actually close the file descriptor and set it to -1 so we don't
    // accidentally close it again.
    void doClose();
  
    // error handling methods
    void startFail();
    void finishFail();
    void fail(const char* fn, const AsyncSocketException& ex);
    void failConnect(const char* fn, const AsyncSocketException& ex);
    void failRead(const char* fn, const AsyncSocketException& ex);
    void failWrite(const char* fn, WriteCallback* callback, size_t bytesWritten,
                   const AsyncSocketException& ex);
    void failWrite(const char* fn, const AsyncSocketException& ex);
    void failAllWrites(const AsyncSocketException& ex);
    void invalidState(ConnectCallback* callback);
    void invalidState(ReadCallback* callback);
    void invalidState(WriteCallback* callback);
  
    std::string withAddr(const std::string& s);
  
    StateEnum state_;                     ///< StateEnum describing current state
    uint8_t shutdownFlags_;               ///< Shutdown state (ShutdownFlags)
    uint16_t eventFlags_;                 ///< EventBase::HandlerFlags settings
    int fd_;                              ///< The socket file descriptor
    mutable
      folly::SocketAddress addr_;    ///< The address we tried to connect to
    uint32_t sendTimeout_;                ///< The send timeout, in milliseconds
    uint16_t maxReadsPerEvent_;           ///< Max reads per event loop iteration
    EventBase* eventBase_;               ///< The EventBase
    WriteTimeout writeTimeout_;           ///< A timeout for connect and write
    IoHandler ioHandler_;                 ///< A EventHandler to monitor the fd
  
    ConnectCallback* connectCallback_;    ///< ConnectCallback
    ReadCallback* readCallback_;          ///< ReadCallback
    WriteRequest* writeReqHead_;          ///< Chain of WriteRequests
    WriteRequest* writeReqTail_;          ///< End of WriteRequest chain
    ShutdownSocketSet* shutdownSocketSet_;
    size_t appBytesReceived_;             ///< Num of bytes received from socket
    size_t appBytesWritten_;              ///< Num of bytes written to socket
  };
  
  
  } // folly
  