Reference

ACE_Shared_Memory_Pool(3)

Make a memory pool that is based on System V shared memory (shmget(2) etc.). This implementation allows memory to be shared between processes.

NAME

ACE_Shared_Memory_Pool - Make a memory pool that is based on System V shared memory (shmget(2) etc.). This implementation allows memory to be shared between processes.

SYNOPSIS

#include <ace/ACE_Memory_Pool.h>
class ACE_Shared_Memory_Pool : public ACE_Event_Handler
{
  public:
    typedef ACE_Shared_Memory_Pool_Options OPTIONS;
    ACE_Shared_Memory_Pool (
        LPCTSTR backing_store_name = 0,
        const OPTIONS *options = 0
        );
    virtual ~ACE_Shared_Memory_Pool (void);
    virtual void *init_acquire (
        size_t nbytes,
        size_t &rounded_bytes,
        int &first_time
        );
    virtual void *acquire (size_t nbytes, size_t &rounded_bytes);
    virtual int release (void);
    virtual int sync (ssize_t len = -1, int flags = MS_SYNC);
    virtual int sync (void *addr, size_t len, int flags = MS_SYNC);
    virtual int protect (ssize_t len = -1, int prot = PROT_RDWR);
    virtual int protect (
        void *addr,
        size_t len,
        int prot = PROT_RDWR
        );
    virtual void dump (void) const;
    ACE_ALLOC_HOOK_DECLARE;
  protected:
    virtual size_t round_up (size_t nbytes);
    virtual int commit_backing_store_name (
        size_t rounded_bytes,
        off_t &offset
        );
    struct SHM_TABLE
    {
      public:
        key_t key_;
        int shmid_;
        int used_;
    };

void *base_addr_; size_t file_perms_; size_t max_segments_; off_t minimum_bytes_; size_t segment_size_; key_t base_shm_key_; virtual int find_seg (
const void *const searchPtr,
off_t &offset,
size_t &counter
); virtual int in_use (off_t &offset, size_t &counter); ACE_Sig_Handler signal_handler_; virtual int handle_signal (int signum, siginfo_t *, ucontext_t *); };

Keeps track of all the segments being used.

void *base_addr_;

Base address of the shared memory segment. If this has the value of 0 then the OS is free to select any address, otherwise this value is what the OS must try to use to map the shared memory segment.

size_t file_perms_;

File permissions to use when creating/opening a segment.

size_t max_segments_;

Number of shared memory segments in the SHM_TABLE table.

off_t minimum_bytes_;

What the minimim bytes of the initial segment should be.

size_t segment_size_;

Shared memory segment size.

key_t base_shm_key_;

Base shared memory key for the segment.

virtual int find_seg (
    const void *const searchPtr,
    off_t &offset,
    size_t &counter
    );

find the segment that contains the searchPtr

virtual int in_use (off_t &offset, size_t &counter);

Determine how much memory is currently in use.

ACE_Sig_Handler signal_handler_;

Handles SIGSEGV.

virtual int handle_signal (int signum, siginfo_t *, ucontext_t *);

Handle SIGSEGV and SIGBUS signals to remap shared memory properly.

AUTHOR

Doug Schmidt and Prashant Jain

LIBRARY

ace