src/ipc/TypedMsgHdr.h

   1 /*
   2  * Copyright (C) 1996-2017 The Squid Software Foundation and contributors
   3  *
   4  * Squid software is distributed under GPLv2+ license and includes
   5  * contributions from numerous individuals and organizations.
   6  * Please see the COPYING and CONTRIBUTORS files for details.
   7  */
   8
   9 /* DEBUG: section 54    Interprocess Communication */
  10
  11 #ifndef SQUID_IPC_TYPED_MSG_HDR_H
  12 #define SQUID_IPC_TYPED_MSG_HDR_H
  13
  14 #include "compat/cmsg.h"
  15 #if HAVE_SYS_SOCKET_H
  16 #include <sys/socket.h>
  17 #endif
  18 #if HAVE_SYS_UIO_H
  19 #include <sys/uio.h>
  20 #endif
  21 #if HAVE_SYS_UN_H
  22 #include <sys/un.h>
  23 #endif
  24
  25 class String;
  26
  27 namespace Ipc
  28 {
  29
  30 /// struct msghdr with a known type, fixed-size I/O and control buffers
  31 class TypedMsgHdr: public msghdr
  32 {
  33 public:
  34     enum {maxSize = 4096};
  35
  36 public:
  37     TypedMsgHdr();
  38     TypedMsgHdr(const TypedMsgHdr &tmh);
  39     TypedMsgHdr &operator =(const TypedMsgHdr &tmh);
  40
  41     void address(const struct sockaddr_un &addr); ///< sets [dest.] address
  42
  43     /* message type manipulation; these must be called before put/get*() */
  44     void setType(int aType); ///< sets message type; use MessageType enum
  45     void checkType(int aType) const; ///< throws if stored type is not aType
  46     int type() const; ///< returns stored type or zero if none
  47
  48     /* access for Plain Old Data (POD)-based message parts */
  49     template <class Pod>
  50     void getPod(Pod &pod) const { getFixed(&pod, sizeof(pod)); } ///< load POD
  51     template <class Pod>
  52     void putPod(const Pod &pod) { putFixed(&pod, sizeof(pod)); } ///< store POD
  53
  54     /* access to message parts for selected commonly-used part types */
  55     void getString(String &s) const; ///< load variable-length string
  56     void putString(const String &s); ///< store variable-length string
  57     int getInt() const; ///< load an integer
  58     void putInt(int n); ///< store an integer
  59     void getFixed(void *raw, size_t size) const; ///< always load size bytes
  60     void putFixed(const void *raw, size_t size); ///< always store size bytes
  61
  62     /// returns true if there is data to extract; handy for optional parts
  63     bool hasMoreData() const { return offset < data.size; }
  64
  65     /* access to a "file" descriptor that can be passed between processes */
  66     void putFd(int aFd); ///< stores descriptor
  67     int getFd() const; ///< returns stored descriptor
  68     bool hasFd() const; ///< whether the message has a descriptor stored
  69
  70     /* raw, type-independent access for I/O */
  71     void prepForReading(); ///< reset and provide all buffers
  72     char *raw() { return reinterpret_cast<char*>(this); }
  73     const char *raw() const { return reinterpret_cast<const char*>(this); }
  74     size_t size() const { return sizeof(*this); } ///< not true message size
  75
  76 private:
  77     void sync();
  78     void allocData();
  79     void allocName();
  80     void allocControl();
  81
  82     /* raw, type-independent manipulation used by type-specific methods */
  83     void getRaw(void *raw, size_t size) const;
  84     void putRaw(const void *raw, size_t size);
  85
  86 private:
  87     struct sockaddr_un name; ///< same as .msg_name
  88
  89     struct iovec ios[1]; ///< same as .msg_iov[]
  90
  91     struct DataBuffer {
  92         int type_; ///< Message kind, uses MessageType values
  93         size_t size; ///< actual raw data size (for sanity checks)
  94         char raw[maxSize]; ///< buffer with type-specific data
  95     } data; ///< same as .msg_iov[0].iov_base
  96
  97     struct CtrlBuffer {
  98         /// control buffer space for one fd
  99         char raw[SQUID_CMSG_SPACE(sizeof(int))];
 100     } ctrl; ///< same as .msg_control
 101
 102     /// data offset for the next get/put*() to start with
 103     mutable unsigned int offset;
 104 };
 105
 106 } // namespace Ipc
 107
 108 #endif /* SQUID_IPC_TYPED_MSG_HDR_H */
 109