// filename: ndbm.h
// Author: Zunhe JIN, Liping Wang
// Date:   July, 1998
// Description:
// 	This is a substitute of the UNIX ndbm database engine. 
//	We would like to call TH ndbm, where TH stands for 
//	our mother school---Tsinghua University.
//  	The only difference is that our new database engine can
//	only handle predefined size data. If there are several kind
//	length of records, just fix it to the maximum and we can
//	deal the rest for you. The advantage over the UNIX ndbm 
//	is that TH can save more disk space, sometimes more than
//	10 times when the data length is bigger that 1k bytes.
//	We are now testing the performance and will publish it later.  
//	All the interfaces we provide here are the same with 
//	that of the ndbm database. So when you face a problem
//	or want to look up the detail of the interface description, 
//	just key in the following command on UNIX consol:
//	$ man ndbm
//	You will get the whole manual.



// char *       SCCS_VER="@(#)ndbm.h	1.1	04/15/02";

#ifndef _NDBM_H
#define	_NDBM_H

//#pragma ident	"@(#)ndbm.h	1.7	92/07/14 SMI"	/* SVr4.0 1.1	*/

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


#define	PBLKSIZ 1024
#define	DBLKSIZ 4096

typedef struct {
	int	dbm_pagf;		/* open page file */
	int	dbm_flags;		/* flags, see below */
	char	dbm_pagbuf[PBLKSIZ];	/* page file block buffer */
		//this buf contains the content,
		// its length should be longer than MAX_DATA_SIZE.
                //otherwise a read-disk operation will overwrite dbm_dirbuf.

	char	dbm_dirbuf[DBLKSIZ];	/* directory file block buffer */
		//this buf contains the key,
		// its length should be longer than MAX_KEY_SIZE.
                //otherwise a read-disk operation will overwrite following fields.

	char *dbm_table;          /* dbm table of location mapping */
	char	*dbm_holelist;		/* hole list in the page file */
	int 	dbm_maxslot;		/* the biggest slot number */		
	int	dbm_curslot;		/* current slot number */
	char	i_have_lock_on_file;	/* 1: I have write_lock, can wirte. */
	char	dbm_filename[32];		//as key in hash array/
} DBM;

#define	_DBM_RDONLY	0x1	/* data base open read-only */
#define	_DBM_IOERR	0x2	/* data base I/O error */

#define	dbm_rdonly(db)	((db)->dbm_flags & _DBM_RDONLY)

#define	dbm_error(db)	((db)->dbm_flags & _DBM_IOERR)
	/* use this one at your own risk! */
#define	dbm_clearerr(db)	((db)->dbm_flags &= ~_DBM_IOERR)

/* for fstat(2) */
#define	dbm_dirfno(db)	((db)->dbm_dirf)
#define	dbm_pagfno(db)	((db)->dbm_pagf)

typedef struct {
	char	*dptr;
	int	dsize;
} datum;

/*
 * flags to dbm_store()
 */
#define	DBM_INSERT	0
#define	DBM_REPLACE	1

DBM	*dbm_open(char *, int, int);
void	dbm_close(DBM *);
datum	dbm_fetch(DBM *, datum);
datum	dbm_firstkey(DBM *);
datum	dbm_nextkey(DBM *);
int	dbm_delete(DBM *, datum);
int	dbm_store(DBM *, datum, datum, int);
int	dbm_commit();

//#ifdef	__cplusplus
//}
//#endif

#endif	/* _NDBM_H */