shm.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

/*-------------------------------------------------------------------------
 *
 * shm.c
 *	  BeOS System V Shared Memory Emulation
 *
 * Copyright (c) 1999-2001, Cyril VELTER
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"
#include <OS.h>
#include <errno.h>

/* Emulating SYS shared memory with beos areas. WARNING : fork clone
areas in copy on write mode */


/* Detach from a shared mem area based on its address */
int
shmdt(char *shmaddr)
{
	/* Find area id for this address */
	area_id		s;

	s = area_for(shmaddr);

	/* Delete area */
	return delete_area(s);
}

/* Attach to an existing area */
int *
shmat(int memId, int m1, int m2)
{
	/* Get our team id */
	thread_info thinfo;
	team_info	teinfo;
	area_info	ainfo;

	get_thread_info(find_thread(NULL), &thinfo);
	get_team_info(thinfo.team, &teinfo);

	/* Get area teamid */
	if (get_area_info(memId, &ainfo) != B_OK)
		printf("AREA %d Invalide\n", memId);

	if (ainfo.team == teinfo.team)
	{
		/*
		 * the area is already in our address space, just return the address
		 */
		return (int *) ainfo.address;
	}
	else
	{
		/*
		 * the area is not in our address space, clone it before and return
		 * the address
		 */
		area_id		narea;

		narea = clone_area(ainfo.name, &(ainfo.address), B_CLONE_ADDRESS, B_READ_AREA | B_WRITE_AREA, memId);
		get_area_info(narea, &ainfo);
		return (int *) ainfo.address;
	}
}

/* Control a shared mem area */
int
shmctl(int shmid, int flag, struct shmid_ds * dummy)
{
	if (flag == IPC_RMID)
	{
		/* Delete the area */
		delete_area(shmid);
		return 0;
	}
	if (flag == IPC_STAT)
	{
		/* Find any SYSV area with the shmid in its name */

		area_info	inf;
		team_info	infteam;
		int32		cookteam = 0;
		char		name[50];

		sprintf(name, "SYSV_IPC %d", shmid);

		dummy->shm_nattch = 0;

		while (get_next_team_info(&cookteam, &infteam) == B_OK)
		{
			int32		cook = 0;

			while (get_next_area_info(infteam.team, &cook, &inf) == B_OK)
			{
				if (strcmp(name, inf.name) == 0)
					dummy->shm_nattch++;
			}
		}

		errno = 0;
		return 0;
	}
	errno = EINVAL;
	return -1;
}

/* Get an area based on the IPC key */
int
shmget(int memKey, int size, int flag)
{
	char		nom[50];
	void	   *Address;
	area_id		parea;

	/* Area name */
	sprintf(nom, "SYSV_IPC_SHM : %d", memKey);

	/* Find area */
	parea = find_area(nom);

	/* area exist, just return its id */
	if (parea != B_NAME_NOT_FOUND)
		return parea;

	/* area does not exist and no creation is requested : error */
	if (flag == 0)
		return -1;

	/*
	 * area does not exist and its creation is requested, create it (be sure
	 * to have a 4ko multiple size
	 */
	return create_area(nom, &Address, B_ANY_ADDRESS, ((size / 4096) + 1) * 4096, B_NO_LOCK, B_READ_AREA | B_WRITE_AREA);
}