src/ipc/mem/Segment.h

   1 /*
   2  * Copyright (C) 1996-2014 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 #ifndef SQUID_IPC_MEM_SEGMENT_H
  10 #define SQUID_IPC_MEM_SEGMENT_H
  11
  12 #include "base/RunnersRegistry.h"
  13 #include "SquidString.h"
  14
  15 class SBuf;
  16
  17 namespace Ipc
  18 {
  19
  20 namespace Mem
  21 {
  22
  23 /// POSIX shared memory segment
  24 class Segment
  25 {
  26 public:
  27     /// Create a shared memory segment.
  28     Segment(const char *const id);
  29     ~Segment();
  30
  31     /// Whether shared memory support is available
  32     static bool Enabled();
  33
  34     /// Create a new shared memory segment. Unlinks the segment on destruction.
  35     void create(const off_t aSize);
  36     void open(); ///< Open an existing shared memory segment.
  37
  38     const String &name() { return theName; } ///< shared memory segment name
  39     off_t size() { return theSize; } ///< shared memory segment size
  40     void *mem() { return reserve(0); } ///< pointer to the next chunk
  41     void *reserve(size_t chunkSize); ///< reserve and return the next chunk
  42
  43     /// common path of all segment names in path-based environments
  44     static const char *BasePath;
  45
  46     /// concatenates parts of a name to form a complete name (or its prefix)
  47     static SBuf Name(const SBuf &prefix, const char *suffix);
  48
  49 private:
  50
  51     // not implemented
  52     Segment(const Segment &);
  53     Segment &operator =(const Segment &);
  54
  55 #if HAVE_SHM
  56
  57     void attach();
  58     void detach();
  59     void unlink(); ///< unlink the segment
  60     off_t statSize(const char *context) const;
  61
  62     static String GenerateName(const char *id);
  63
  64     int theFD; ///< shared memory segment file descriptor
  65
  66 #else // HAVE_SHM
  67
  68     void checkSupport(const char *const context);
  69
  70 #endif // HAVE_SHM
  71
  72     const String theName; ///< shared memory segment file name
  73     void *theMem; ///< pointer to mmapped shared memory segment
  74     off_t theSize; ///< shared memory segment size
  75     off_t theReserved; ///< the total number of reserve()d bytes
  76     bool doUnlink; ///< whether the segment should be unlinked on destruction
  77 };
  78
  79 /// Base class for runners that create and open shared memory segments.
  80 /// First may run create() method and then open().
  81 class RegisteredRunner: public ::RegisteredRunner
  82 {
  83 public:
  84     /* RegisteredRunner API */
  85     virtual void useConfig();
  86
  87 protected:
  88     /// called when the runner should create a new memory segment
  89     virtual void create() = 0;
  90     /// called when the runner should open a previously created segment,
  91     /// not needed if segments are opened in constructor or init methods
  92     virtual void open() {}
  93 };
  94
  95 } // namespace Mem
  96
  97 } // namespace Ipc
  98
  99 #endif /* SQUID_IPC_MEM_SEGMENT_H */