jk_shm.h

Tomcat 4.1与WebServer集成组件的源代码包.

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#ifndef JK_SHM_H
#define JK_SHM_H

#include "jk_global.h"
#include "jk_env.h"
#include "jk_logger.h"
#include "jk_pool.h"
#include "jk_msg.h"
#include "jk_service.h"

#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */

struct jk_env;
struct jk_shm;
    
typedef struct jk_shm jk_shm_t;
typedef struct jk_shm_slot jk_shm_slot_t;
typedef struct jk_shm_head jk_shm_head_t;


/* That's the default - should be enough for most cases.
   8k is what we use as the default packet size in ajp13, and 256
   slots should be enough for now ( == 256 workers )
   XXX implement the setters to override this
*/
#define DEFAULT_SLOT_SIZE 1024 * 8
#define DEFAULT_SLOT_COUNT 256


    
/** Each shared memory slot has at least the following components.
 */
struct jk_shm_slot {
    /** Version of the segment. Whoever writes it must change the
        version after writing. Various components will check the version
        and refresh if needed
    */
    int ver;

    /** Size of the segment */
    int size;

    int structSize;
    int structCnt;
    
    /** Full name of the segment. type:localName convention.
     */
    char name[64];

    char data[1];
};

    
struct jk_shm_head {
    struct jk_shm_slot slot;
    
    int slotSize;
    
    int slotMaxCount;
    
    /* Last used position. Increase ( at least atomically, eventually with mutexes )
       each time a slot is created */
    int lastSlot;

    /* XXX Need a more generic mechanism */
    int lbVer;
};


/**
 *  Shared memory support. This is similar with the scoreboard or jserv's worker shm, but
 *  organized a bit more generic to support use of shm as a channel and to support config
 *  changes.
 * 
 *  The structure is organized as an array of 'slots'. Each slot has a name and data. Slots are long lived -
 *  they are never destroyed.
 *  Each slot has it's own rules for content and synchronization - but typically they are 'owned'
 *  by a process or thread and use various conventions to avoid the need for sync.
  *
 * @author Costin Manolache
 */
struct jk_shm {
    struct jk_bean *mbean;

    struct jk_pool *pool;

    char *fname;

    /** Initialize the shared memory area. It'll map the shared memory 
     *  segment if it exists, or create and init it if not.
     */
    int (JK_METHOD *init)(struct jk_env *env, struct jk_shm *shm);

    /** Reset the shm area
     */
    int (JK_METHOD *reset)(struct jk_env *env, struct jk_shm *shm);

    
    /** Detach from the shared memory segment
     */
    int (JK_METHOD *destroy)(struct jk_env *env, struct jk_shm *shm);

    /** Get a shm slot. Each slot has different rules for synchronization, based on type. 
     */
    struct jk_shm_slot *(JK_METHOD *getSlot)(struct jk_env *env, struct jk_shm *shm, int pos);

    /** Create a slot. This typically involves inter-process synchronization.
     */
    struct jk_shm_slot *(JK_METHOD *createSlot)(struct jk_env *env, struct jk_shm *shm, char *name, int size);

    int size;

    int slotSize;
    
    int slotMaxCount;
    
    void *image;

    struct jk_shm_head *head;

    /* Private data */
    void *privateData;
};
    
#ifdef __cplusplus
}
#endif /* __cplusplus */

#endif