jack1/include/shm.h

#ifndef __jack_shm_h__
#define __jack_shm_h__

#include <limits.h>
#include <sys/types.h>
#include <jack/types.h>

#define MAX_SERVERS 8                   /* maximum concurrent servers */
#define MAX_SHM_ID 256                  /* generally about 16 per server */
#define JACK_SERVER_NAME_SIZE 256       /* maximum length of server name */
#define JACK_SHM_MAGIC 0x4a41434b       /* shm magic number: "JACK" */
#define JACK_SHM_NULL_INDEX -1          /* NULL SHM index */
#define JACK_SHM_REGISTRY_INDEX -2      /* pseudo SHM index for registry */


/* On Mac OS X, SHM_NAME_MAX is the maximum length of a shared memory
 * segment name (instead of NAME_MAX or PATH_MAX as defined by the
 * standard).
 */
#ifdef USE_POSIX_SHM
#ifndef SHM_NAME_MAX
#define SHM_NAME_MAX NAME_MAX
#endif
typedef char shm_name_t[SHM_NAME_MAX];
typedef shm_name_t jack_shm_id_t;
#else /* System V SHM */
typedef int jack_shm_id_t;
#endif /* SHM type */

/* shared memory type */
typedef enum {
	shm_POSIX = 1,                  /* POSIX shared memory */
	shm_SYSV = 2                    /* System V shared memory */
} jack_shmtype_t;

typedef int16_t jack_shm_registry_index_t;

/**
 * A structure holding information about shared memory allocated by
 * JACK. this persists across invocations of JACK, and can be used by
 * multiple JACK servers.  It contains no pointers and is valid across
 * address spaces.
 *
 * The registry consists of two parts: a header including an array of
 * server names, followed by an array of segment registry entries.
 */
typedef struct _jack_shm_server {
	pid_t pid;                      /* process ID */
	char name[JACK_SERVER_NAME_SIZE];
} jack_shm_server_t;

typedef struct _jack_shm_header {
	uint32_t magic;                         /* magic number */
	uint16_t protocol;                      /* JACK protocol version */
	jack_shmtype_t type;                    /* shm type */
	jack_shmsize_t size;                    /* total registry segment size */
	jack_shmsize_t hdr_len;                 /* size of header */
	jack_shmsize_t entry_len;               /* size of registry entry */
	jack_shm_server_t server[MAX_SERVERS];  /* current server array */
} jack_shm_header_t;

typedef struct _jack_shm_registry {
	jack_shm_registry_index_t index;        /* offset into the registry */
	pid_t allocator;                        /* PID that created shm segment */
	jack_shmsize_t size;                    /* for POSIX unattach */
	jack_shm_id_t id;                       /* API specific, see above */
} jack_shm_registry_t;

#define JACK_SHM_REGISTRY_SIZE (sizeof(jack_shm_header_t) \
				+ sizeof(jack_shm_registry_t) * MAX_SHM_ID)

/**
 * a structure holding information about shared memory
 * allocated by JACK. this version is valid only
 * for a given address space. It contains a pointer
 * indicating where the shared memory has been
 * attached to the address space.
 */
typedef struct _jack_shm_info {
	jack_shm_registry_index_t index;        /* offset into the registry */
	void                     *attached_at;  /* address where attached */
} jack_shm_info_t;

/* utility functions used only within JACK */

extern void jack_shm_copy_from_registry (jack_shm_info_t *,
					 jack_shm_registry_index_t);
extern void jack_shm_copy_to_registry(jack_shm_info_t*,
				      jack_shm_registry_index_t*);
extern void jack_release_shm_info (jack_shm_registry_index_t);

static inline char* jack_shm_addr (jack_shm_info_t* si)
{
	return si->attached_at;
}

/* here beginneth the API */

extern int  jack_register_server(const char *server_name, int new_registry);
extern void jack_unregister_server(const char *server_name);

extern int  jack_initialize_shm(const char *server_name);
extern int  jack_cleanup_shm(void);

extern int  jack_shmalloc(jack_shmsize_t size, jack_shm_info_t* result);
extern void jack_release_shm(jack_shm_info_t*);
extern void jack_destroy_shm(jack_shm_info_t*);
extern int  jack_attach_shm(jack_shm_info_t*);
extern int  jack_resize_shm(jack_shm_info_t*, jack_shmsize_t size);

#endif /* __jack_shm_h__ */