shared.h

多线程库

#ifndef __THREAD_SHARED_H
#define __THREAD_SHARED_H

#include "thread.h"
#include "thread_list.h"

extern "C" {

#    include <sys/ipc.h>
#    include <sys/shm.h>

};

/**
 * This is a class that takes care of shared memory allocations
 * and access.
 *
 * By utilizing a malloc() like scheme, the class retrieves
 * shared pages from the kernel and installs them into a list
 * of free pages.  These pages are usually far larger, then
 * the amount of memory a user will need, thus they will
 * fragmented and saved in a used list, where they can be
 * checked against, when a user returns them to the pool
 *
 * Memory that doesn't belong to the pool of shared memory,
 * is not returned to it... but ignored.
 *
 * @author Orn Hansen <[e-mail]>
 * @short Maintain shared memory.
 */
class shared_mem {
 public:
  struct mem_entry {
    size_t    _size;
    void *    _data;
  };
  struct storage {
    int       _id;
    int       _mid;
    key_t     _key;
    char *    _file;
    int       _proj;
    void *    _ptr;
    size_t    _page;
  };

  typedef list<storage>::iterator   sto_iterator;
  typedef list<mem_entry>::iterator mem_iterator;

 private:
  int _perm;
  int _blocks;
  char *_key_root;
  mutex _key_lock;               // Exclusive access to keys.
  mutex _mem_lock;               // Exclusive access to memory lists.
  struct mem_entry  _mem_entry;
  struct storage    _work_area;
  list<storage>     _shared;
  list<mem_entry>   _free_list;
  list<mem_entry>   _used_list;

  mem_iterator getmem(sto_iterator,size_t);
  mem_iterator fillup(size_t,int);
  void fragment(mem_iterator,size_t);
 public:
  shared_mem();
  shared_mem(const char *);
  ~shared_mem();

  /**
   * Create a new branch from the main project tree.
   *
   * @param s The branch name.
   * @return An integer identifying the project.
   */
  int create_proj(const char *);
  /**
   * Create a key project, that is connected to the
   * branch tree obtain from @ref #create_proj
   *
   * @param p The project id.
   * @return A key identifier that can be used to get shared memory.
   */
  key_t make_key(int);
  /**
   * Obtain a key, which has alredy been created.  The key
   * is calculated, based on a branch and project identifier.
   *
   * @param s The branch name.
   * @param i The project identifier.
   * @return Calculated key, or -1 if error.
   */
  key_t get_key(const char *,int);
  /**
   * Allocate a selected sized memory, based on the given
   * key.
   *
   * @param k The key to allocate memory with.
   * @param s The size of memory to allocate.
   * @return A pointer to allocated memory, or 0 if error.
   */
  void *keyalloc(key_t,size_t);
  /**
   * Allocate memory, and associate it with a given project
   * identifier.  See @ref #create_proj
   * 
   * @param s The size of memory to allocate.
   * @param i The project identifier, 0 = main project.
   * @return Allocated memory, or 0 if error.
   */
  void *alloc(size_t,int);
  /**
   * Memory allocated should be returned to the memory pool.  This will
   * enable programs to reuse it in another context, if needed.  This is
   * not necessary though, as all shared memory mapped will be destroyed
   * on exit.
   *
   * @param p A pointer to the memory, that was allocated.
   */
  void dealloc(void *);

  /**
   * Change the name of the main project... root name.
   *
   * @param s The name to give the root project.
   */
  void change_proj(const char *);
  /**
   * Change the permissions, that are given to newly
   * allocated shared memory pages.
   *
   * @param p The permissions to give.
   */
  void change_perm(int);

  /**
   * Cleanup all memory, and lock the allocator to prohibit any
   * other access.
   */
  void cleanup();

  /**
   * This is the global allocator object.
   */
  static shared_mem share;

};

#endif /* __THREAD_SHARED_H */