src/ipc/mem/Segment.h

   1 /*
   2  * Copyright (C) 1996-2016 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 "sbuf/forward.h"
  14 #include "SquidString.h"
  15
  16 namespace Ipc
  17 {
  18
  19 namespace Mem
  20 {
  21
  22 /// POSIX shared memory segment
  23 class Segment
  24 {
  25 public:
  26     /// Create a shared memory segment.
  27     Segment(const char *const id);
  28     ~Segment();
  29
  30     /// Whether shared memory support is available
  31     static bool Enabled();
  32
  33     /// Create a new shared memory segment. Unlinks the segment on destruction.
  34     void create(const off_t aSize);
  35     void open(); ///< Open an existing shared memory segment.
  36
  37     const String &name() { return theName; } ///< shared memory segment name
  38     off_t size() { return theSize; } ///< shared memory segment size
  39     void *mem() { return reserve(0); } ///< pointer to the next chunk
  40     void *reserve(size_t chunkSize); ///< reserve and return the next chunk
  41
  42     /// common path of all segment names in path-based environments
  43     static const char *BasePath;
  44
  45     /// concatenates parts of a name to form a complete name (or its prefix)
  46     static SBuf Name(const SBuf &prefix, const char *suffix);
  47
  48 private:
  49
  50     // not implemented
  51     Segment(const Segment &);
  52     Segment &operator =(const Segment &);
  53
  54 #if HAVE_SHM
  55
  56     bool createFresh(int &err);
  57     void attach();
  58     void detach();
  59     void lock();
  60     void unlink(); ///< unlink the segment
  61     off_t statSize(const char *context) const;
  62
  63     static String GenerateName(const char *id);
  64
  65     int theFD; ///< shared memory segment file descriptor
  66
  67 #else // HAVE_SHM
  68
  69     void checkSupport(const char *const context);
  70
  71 #endif // HAVE_SHM
  72
  73     const String theName; ///< shared memory segment file name
  74     void *theMem; ///< pointer to mmapped shared memory segment
  75     off_t theSize; ///< shared memory segment size
  76     off_t theReserved; ///< the total number of reserve()d bytes
  77     bool doUnlink; ///< whether the segment should be unlinked on destruction
  78 };
  79
  80 /// Base class for runners that create and open shared memory segments.
  81 /// First may run create() method and then open().
  82 class RegisteredRunner: public ::RegisteredRunner
  83 {
  84 public:
  85     /* RegisteredRunner API */
  86     virtual void useConfig();
  87
  88 protected:
  89     /// called when the runner should create a new memory segment
  90     virtual void create() = 0;
  91     /// called when the runner should open a previously created segment,
  92     /// not needed if segments are opened in constructor or init methods
  93     virtual void open() {}
  94 };
  95
  96 } // namespace Mem
  97
  98 } // namespace Ipc
  99
 100 #endif /* SQUID_IPC_MEM_SEGMENT_H */
 101