[unix-history] / lib / libc / db / hash / hash.h

/*-
 * Copyright (c) 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Margo Seltzer.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)hash.h	8.1 (Berkeley) 6/4/93
 */

/* Operations */
typedef enum {
	HASH_GET, HASH_PUT, HASH_PUTNEW, HASH_DELETE, HASH_FIRST, HASH_NEXT
} ACTION;

/* Buffer Management structures */
typedef struct _bufhead BUFHEAD;

struct _bufhead {
	BUFHEAD	*prev;		/* LRU links */
	BUFHEAD	*next;		/* LRU links */
	BUFHEAD	*ovfl;		/* Overflow page buffer header */
	u_int	 addr;		/* Address of this page */
	char	*page;		/* Actual page data */
	char	 flags;
#define	BUF_MOD		0x0001
#define BUF_DISK	0x0002
#define	BUF_BUCKET	0x0004
#define	BUF_PIN		0x0008
};

#define IS_BUCKET(X)	((X) & BUF_BUCKET)

typedef BUFHEAD **SEGMENT;

/* Hash Table Information */
typedef struct hashhdr {	/* Disk resident portion */
	int	magic;		/* Magic NO for hash tables */
	int	version;	/* Version ID */
	long	lorder;		/* Byte Order */
	int	bsize;		/* Bucket/Page Size */
	int	bshift;		/* Bucket shift */
	int	dsize;		/* Directory Size */
	int	ssize;		/* Segment Size */
	int	sshift;		/* Segment shift */
	int	ovfl_point;	/* Where overflow pages are being allocated */
	int	last_freed;	/* Last overflow page freed */
	int	max_bucket;	/* ID of Maximum bucket in use */
	int	high_mask;	/* Mask to modulo into entire table */
	int	low_mask;	/* Mask to modulo into lower half of table */
	int	ffactor;	/* Fill factor */
	int	nkeys;		/* Number of keys in hash table */
	int	hdrpages;	/* Size of table header */
	int	h_charkey;	/* value of hash(CHARKEY) */
#define NCACHED	32		/* number of bit maps and spare points */
	int	spares[NCACHED];/* spare pages for overflow */
	u_short	bitmaps[NCACHED];	/* address of overflow page bitmaps */
} HASHHDR;

typedef struct htab {		/* Memory resident data structure */
	HASHHDR hdr;		/* Header */
	int	nsegs;		/* Number of allocated segments */
	int	exsegs;		/* Number of extra allocated segments */
	int	(*hash) ();	/* Hash Function */
	int	flags;		/* Flag values */
	int	fp;		/* File pointer */
	char	*tmp_buf;	/* Temporary Buffer for BIG data */
	char	*tmp_key;	/* Temporary Buffer for BIG keys */
	BUFHEAD *cpage;		/* Current page */
	int	cbucket;	/* Current bucket */
	int	cndx;		/* Index of next item on cpage */
	int	errno;		/* Error Number -- for DBM compatability */
	int	new_file;	/* Indicates if fd is backing store or no */
	int	save_file;	/* Indicates whether we need to flush file at
				 * exit */
	u_long *mapp[NCACHED];	/* Pointers to page maps */
	int	nmaps;		/* Initial number of bitmaps */
	int	nbufs;		/* Number of buffers left to allocate */
	BUFHEAD bufhead;	/* Header of buffer lru list */
	SEGMENT *dir;		/* Hash Bucket directory */
} HTAB;

/*
 * Constants
 */
#define	MAX_BSIZE		65536		/* 2^16 */
#define MIN_BUFFERS		6
#define MINHDRSIZE		512
#define DEF_BUFSIZE		65536		/* 64 K */
#define DEF_BUCKET_SIZE		4096
#define DEF_BUCKET_SHIFT	12		/* log2(BUCKET) */
#define DEF_SEGSIZE		256
#define DEF_SEGSIZE_SHIFT	8		/* log2(SEGSIZE)	 */
#define DEF_DIRSIZE		256
#define DEF_FFACTOR		65536
#define MIN_FFACTOR		4
#define SPLTMAX			8
#define CHARKEY			"%$sniglet^&"
#define NUMKEY			1038583
#define BYTE_SHIFT		3
#define INT_TO_BYTE		2
#define INT_BYTE_SHIFT		5
#define ALL_SET			((u_int)0xFFFFFFFF)
#define ALL_CLEAR		0

#define PTROF(X)	((BUFHEAD *)((u_int)(X)&~0x3))
#define ISMOD(X)	((u_int)(X)&0x1)
#define DOMOD(X)	((X) = (char *)((u_int)(X)|0x1))
#define ISDISK(X)	((u_int)(X)&0x2)
#define DODISK(X)	((X) = (char *)((u_int)(X)|0x2))

#define BITS_PER_MAP	32

/* Given the address of the beginning of a big map, clear/set the nth bit */
#define CLRBIT(A, N)	((A)[(N)/BITS_PER_MAP] &= ~(1<<((N)%BITS_PER_MAP)))
#define SETBIT(A, N)	((A)[(N)/BITS_PER_MAP] |= (1<<((N)%BITS_PER_MAP)))
#define ISSET(A, N)	((A)[(N)/BITS_PER_MAP] & (1<<((N)%BITS_PER_MAP)))

/* Overflow management */
/*
 * Overflow page numbers are allocated per split point.  At each doubling of
 * the table, we can allocate extra pages.  So, an overflow page number has
 * the top 5 bits indicate which split point and the lower 11 bits indicate
 * which page at that split point is indicated (pages within split points are
 * numberered starting with 1).
 */

#define SPLITSHIFT	11
#define SPLITMASK	0x7FF
#define SPLITNUM(N)	(((u_int)(N)) >> SPLITSHIFT)
#define OPAGENUM(N)	((N) & SPLITMASK)
#define	OADDR_OF(S,O)	((u_int)((u_int)(S) << SPLITSHIFT) + (O))

#define BUCKET_TO_PAGE(B) \
	(B) + hashp->HDRPAGES + ((B) ? hashp->SPARES[__log2((B)+1)-1] : 0)
#define OADDR_TO_PAGE(B) 	\
	BUCKET_TO_PAGE ( (1 << SPLITNUM((B))) -1 ) + OPAGENUM((B));

/*
 * page.h contains a detailed description of the page format.
 *
 * Normally, keys and data are accessed from offset tables in the top of
 * each page which point to the beginning of the key and data.  There are
 * four flag values which may be stored in these offset tables which indicate
 * the following:
 *
 *
 * OVFLPAGE	Rather than a key data pair, this pair contains
 *		the address of an overflow page.  The format of
 *		the pair is:
 *		    OVERFLOW_PAGE_NUMBER OVFLPAGE
 *
 * PARTIAL_KEY	This must be the first key/data pair on a page
 *		and implies that page contains only a partial key.
 *		That is, the key is too big to fit on a single page
 *		so it starts on this page and continues on the next.
 *		The format of the page is:
 *		    KEY_OFF PARTIAL_KEY OVFL_PAGENO OVFLPAGE
 *		
 *		    KEY_OFF -- offset of the beginning of the key
 *		    PARTIAL_KEY -- 1
 *		    OVFL_PAGENO - page number of the next overflow page
 *		    OVFLPAGE -- 0
 *
 * FULL_KEY	This must be the first key/data pair on the page.  It
 *		is used in two cases.
 *
 *		Case 1:
 *		    There is a complete key on the page but no data
 *		    (because it wouldn't fit).  The next page contains
 *		    the data.
 *
 *		    Page format it:
 *		    KEY_OFF FULL_KEY OVFL_PAGENO OVFL_PAGE
 *
 *		    KEY_OFF -- offset of the beginning of the key
 *		    FULL_KEY -- 2
 *		    OVFL_PAGENO - page number of the next overflow page
 *		    OVFLPAGE -- 0
 *
 *		Case 2:
 *		    This page contains no key, but part of a large
 *		    data field, which is continued on the next page.
 *
 *		    Page format it:
 *		    DATA_OFF FULL_KEY OVFL_PAGENO OVFL_PAGE
 *
 *		    KEY_OFF -- offset of the beginning of the data on
 *				this page
 *		    FULL_KEY -- 2
 *		    OVFL_PAGENO - page number of the next overflow page
 *		    OVFLPAGE -- 0
 *
 * FULL_KEY_DATA 
 *		This must be the first key/data pair on the page.
 *		There are two cases:
 *
 *		Case 1:
 *		    This page contains a key and the beginning of the
 *		    data field, but the data field is continued on the
 *		    next page.
 *
 *		    Page format is:
 *		    KEY_OFF FULL_KEY_DATA OVFL_PAGENO DATA_OFF
 *
 *		    KEY_OFF -- offset of the beginning of the key
 *		    FULL_KEY_DATA -- 3
 *		    OVFL_PAGENO - page number of the next overflow page
 *		    DATA_OFF -- offset of the beginning of the data
 *
 *		Case 2:
 *		    This page contains the last page of a big data pair.
 *		    There is no key, only the  tail end of the data
 *		    on this page.
 *
 *		    Page format is:
 *		    DATA_OFF FULL_KEY_DATA <OVFL_PAGENO> <OVFLPAGE>
 *
 *		    DATA_OFF -- offset of the beginning of the data on
 *				this page
 *		    FULL_KEY_DATA -- 3
 *		    OVFL_PAGENO - page number of the next overflow page
 *		    OVFLPAGE -- 0
 *
 *		    OVFL_PAGENO and OVFLPAGE are optional (they are
 *		    not present if there is no next page).
 */

#define OVFLPAGE	0
#define PARTIAL_KEY	1
#define FULL_KEY	2
#define FULL_KEY_DATA	3
#define	REAL_KEY	4

/* Short hands for accessing structure */
#define BSIZE		hdr.bsize
#define BSHIFT		hdr.bshift
#define DSIZE		hdr.dsize
#define SGSIZE		hdr.ssize
#define SSHIFT		hdr.sshift
#define LORDER		hdr.lorder
#define OVFL_POINT	hdr.ovfl_point
#define	LAST_FREED	hdr.last_freed
#define MAX_BUCKET	hdr.max_bucket
#define FFACTOR		hdr.ffactor
#define HIGH_MASK	hdr.high_mask
#define LOW_MASK	hdr.low_mask
#define NKEYS		hdr.nkeys
#define HDRPAGES	hdr.hdrpages
#define SPARES		hdr.spares
#define BITMAPS		hdr.bitmaps
#define VERSION		hdr.version
#define MAGIC		hdr.magic
#define NEXT_FREE	hdr.next_free
#define H_CHARKEY	hdr.h_charkey
Commit	Line	Data
15637ed4	1	/*-
78ed81a3	2	* Copyright (c) 1990, 1993
78ed81a3	3	* The Regents of the University of California. All rights reserved.
15637ed4 RG	4	*
	5	* This code is derived from software contributed to Berkeley by
	6	* Margo Seltzer.
	7	*
	8	* Redistribution and use in source and binary forms, with or without
	9	* modification, are permitted provided that the following conditions
	10	* are met:
	11	* 1. Redistributions of source code must retain the above copyright
	12	* notice, this list of conditions and the following disclaimer.
	13	* 2. Redistributions in binary form must reproduce the above copyright
	14	* notice, this list of conditions and the following disclaimer in the
	15	* documentation and/or other materials provided with the distribution.
	16	* 3. All advertising materials mentioning features or use of this software
	17	* must display the following acknowledgement:
	18	* This product includes software developed by the University of
	19	* California, Berkeley and its contributors.
	20	* 4. Neither the name of the University nor the names of its contributors
	21	* may be used to endorse or promote products derived from this software
	22	* without specific prior written permission.
	23	*
	24	* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	25	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	26	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	27	* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	28	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	29	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	30	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	31	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	32	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	33	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	34	* SUCH DAMAGE.
	35	*
78ed81a3	36	* @(#)hash.h 8.1 (Berkeley) 6/4/93
15637ed4 RG	37	*/
	38
	39	/* Operations */
78ed81a3	40	typedef enum {
	41	HASH_GET, HASH_PUT, HASH_PUTNEW, HASH_DELETE, HASH_FIRST, HASH_NEXT
	42	} ACTION;
15637ed4 RG	43
	44	/* Buffer Management structures */
	45	typedef struct _bufhead BUFHEAD;
	46
	47	struct _bufhead {
78ed81a3	48	BUFHEAD prev; / LRU links */
	49	BUFHEAD next; / LRU links */
	50	BUFHEAD ovfl; / Overflow page buffer header */
	51	u_int addr; /* Address of this page */
	52	char page; / Actual page data */
	53	char flags;
15637ed4 RG	54	#define BUF_MOD 0x0001
	55	#define BUF_DISK 0x0002
	56	#define BUF_BUCKET 0x0004
	57	#define BUF_PIN 0x0008
	58	};
	59
78ed81a3	60	#define IS_BUCKET(X) ((X) & BUF_BUCKET)
15637ed4	61
78ed81a3	62	typedef BUFHEAD **SEGMENT;
15637ed4 RG	63
	64	/* Hash Table Information */
	65	typedef struct hashhdr { /* Disk resident portion */
78ed81a3	66	int magic; /* Magic NO for hash tables */
	67	int version; /* Version ID */
	68	long lorder; /* Byte Order */
	69	int bsize; /* Bucket/Page Size */
	70	int bshift; /* Bucket shift */
	71	int dsize; /* Directory Size */
	72	int ssize; /* Segment Size */
	73	int sshift; /* Segment shift */
	74	int ovfl_point; /* Where overflow pages are being allocated */
	75	int last_freed; /* Last overflow page freed */
	76	int max_bucket; /* ID of Maximum bucket in use */
	77	int high_mask; /* Mask to modulo into entire table */
	78	int low_mask; /* Mask to modulo into lower half of table */
	79	int ffactor; /* Fill factor */
	80	int nkeys; /* Number of keys in hash table */
	81	int hdrpages; /* Size of table header */
	82	int h_charkey; /* value of hash(CHARKEY) */
	83	#define NCACHED 32 /* number of bit maps and spare points */
	84	int spares[NCACHED];/* spare pages for overflow */
	85	u_short bitmaps[NCACHED]; /* address of overflow page bitmaps */
15637ed4 RG	86	} HASHHDR;
15637ed4 RG	87
78ed81a3	88	typedef struct htab { /* Memory resident data structure */
	89	HASHHDR hdr; /* Header */
	90	int nsegs; /* Number of allocated segments */
	91	int exsegs; /* Number of extra allocated segments */
	92	int (hash) (); / Hash Function */
	93	int flags; /* Flag values */
	94	int fp; /* File pointer */
	95	char tmp_buf; / Temporary Buffer for BIG data */
	96	char tmp_key; / Temporary Buffer for BIG keys */
	97	BUFHEAD cpage; / Current page */
	98	int cbucket; /* Current bucket */
	99	int cndx; /* Index of next item on cpage */
	100	int errno; /* Error Number -- for DBM compatability */
	101	int new_file; /* Indicates if fd is backing store or no */
	102	int save_file; /* Indicates whether we need to flush file at
	103	* exit */
15637ed4	104	u_long mapp[NCACHED]; / Pointers to page maps */
78ed81a3	105	int nmaps; /* Initial number of bitmaps */
	106	int nbufs; /* Number of buffers left to allocate */
	107	BUFHEAD bufhead; /* Header of buffer lru list */
	108	SEGMENT dir; / Hash Bucket directory */
15637ed4 RG	109	} HTAB;
15637ed4 RG	110
15637ed4 RG	111	/*
	112	* Constants
	113	*/
78ed81a3	114	#define MAX_BSIZE 65536 /* 2^16 */
15637ed4 RG	115	#define MIN_BUFFERS 6
15637ed4 RG	116	#define MINHDRSIZE 512
78ed81a3	117	#define DEF_BUFSIZE 65536 /* 64 K */
	118	#define DEF_BUCKET_SIZE 4096
	119	#define DEF_BUCKET_SHIFT 12 /* log2(BUCKET) */
15637ed4	120	#define DEF_SEGSIZE 256
78ed81a3	121	#define DEF_SEGSIZE_SHIFT 8 /* log2(SEGSIZE) */
15637ed4	122	#define DEF_DIRSIZE 256
78ed81a3	123	#define DEF_FFACTOR 65536
	124	#define MIN_FFACTOR 4
	125	#define SPLTMAX 8
	126	#define CHARKEY "%$sniglet^&"
15637ed4	127	#define NUMKEY 1038583
15637ed4 RG	128	#define BYTE_SHIFT 3
	129	#define INT_TO_BYTE 2
	130	#define INT_BYTE_SHIFT 5
78ed81a3	131	#define ALL_SET ((u_int)0xFFFFFFFF)
15637ed4 RG	132	#define ALL_CLEAR 0
15637ed4 RG	133
78ed81a3	134	#define PTROF(X) ((BUFHEAD *)((u_int)(X)&~0x3))
	135	#define ISMOD(X) ((u_int)(X)&0x1)
	136	#define DOMOD(X) ((X) = (char *)((u_int)(X)\|0x1))
	137	#define ISDISK(X) ((u_int)(X)&0x2)
	138	#define DODISK(X) ((X) = (char *)((u_int)(X)\|0x2))
15637ed4	139
78ed81a3	140	#define BITS_PER_MAP 32
15637ed4 RG	141
15637ed4 RG	142	/* Given the address of the beginning of a big map, clear/set the nth bit */
78ed81a3	143	#define CLRBIT(A, N) ((A)[(N)/BITS_PER_MAP] &= ~(1<<((N)%BITS_PER_MAP)))
	144	#define SETBIT(A, N) ((A)[(N)/BITS_PER_MAP] \|= (1<<((N)%BITS_PER_MAP)))
	145	#define ISSET(A, N) ((A)[(N)/BITS_PER_MAP] & (1<<((N)%BITS_PER_MAP)))
15637ed4 RG	146
	147	/* Overflow management */
	148	/*
78ed81a3	149	* Overflow page numbers are allocated per split point. At each doubling of
	150	* the table, we can allocate extra pages. So, an overflow page number has
	151	* the top 5 bits indicate which split point and the lower 11 bits indicate
	152	* which page at that split point is indicated (pages within split points are
	153	* numberered starting with 1).
	154	*/
15637ed4 RG	155
	156	#define SPLITSHIFT 11
	157	#define SPLITMASK 0x7FF
78ed81a3	158	#define SPLITNUM(N) (((u_int)(N)) >> SPLITSHIFT)
	159	#define OPAGENUM(N) ((N) & SPLITMASK)
	160	#define OADDR_OF(S,O) ((u_int)((u_int)(S) << SPLITSHIFT) + (O))
15637ed4 RG	161
15637ed4 RG	162	#define BUCKET_TO_PAGE(B) \
78ed81a3	163	(B) + hashp->HDRPAGES + ((B) ? hashp->SPARES[__log2((B)+1)-1] : 0)
15637ed4	164	#define OADDR_TO_PAGE(B) \
78ed81a3	165	BUCKET_TO_PAGE ( (1 << SPLITNUM((B))) -1 ) + OPAGENUM((B));
15637ed4 RG	166
15637ed4 RG	167	/*
78ed81a3	168	* page.h contains a detailed description of the page format.
	169	*
	170	* Normally, keys and data are accessed from offset tables in the top of
	171	* each page which point to the beginning of the key and data. There are
	172	* four flag values which may be stored in these offset tables which indicate
	173	* the following:
	174	*
	175	*
	176	* OVFLPAGE Rather than a key data pair, this pair contains
	177	* the address of an overflow page. The format of
	178	* the pair is:
	179	* OVERFLOW_PAGE_NUMBER OVFLPAGE
	180	*
	181	* PARTIAL_KEY This must be the first key/data pair on a page
	182	* and implies that page contains only a partial key.
	183	* That is, the key is too big to fit on a single page
	184	* so it starts on this page and continues on the next.
	185	* The format of the page is:
	186	* KEY_OFF PARTIAL_KEY OVFL_PAGENO OVFLPAGE
	187	*
	188	* KEY_OFF -- offset of the beginning of the key
	189	* PARTIAL_KEY -- 1
	190	* OVFL_PAGENO - page number of the next overflow page
	191	* OVFLPAGE -- 0
	192	*
	193	* FULL_KEY This must be the first key/data pair on the page. It
	194	* is used in two cases.
	195	*
	196	* Case 1:
	197	* There is a complete key on the page but no data
	198	* (because it wouldn't fit). The next page contains
	199	* the data.
	200	*
	201	* Page format it:
	202	* KEY_OFF FULL_KEY OVFL_PAGENO OVFL_PAGE
	203	*
	204	* KEY_OFF -- offset of the beginning of the key
	205	* FULL_KEY -- 2
	206	* OVFL_PAGENO - page number of the next overflow page
	207	* OVFLPAGE -- 0
	208	*
	209	* Case 2:
	210	* This page contains no key, but part of a large
	211	* data field, which is continued on the next page.
	212	*
	213	* Page format it:
	214	* DATA_OFF FULL_KEY OVFL_PAGENO OVFL_PAGE
	215	*
	216	* KEY_OFF -- offset of the beginning of the data on
	217	* this page
	218	* FULL_KEY -- 2
	219	* OVFL_PAGENO - page number of the next overflow page
	220	* OVFLPAGE -- 0
	221	*
	222	* FULL_KEY_DATA
	223	* This must be the first key/data pair on the page.
	224	* There are two cases:
	225	*
	226	* Case 1:
	227	* This page contains a key and the beginning of the
	228	* data field, but the data field is continued on the
	229	* next page.
	230	*
	231	* Page format is:
232	* KEY_OFF FULL_KEY_DATA OVFL_PAGENO DATA_OFF
233	*
234	* KEY_OFF -- offset of the beginning of the key
235	* FULL_KEY_DATA -- 3
236	* OVFL_PAGENO - page number of the next overflow page
237	* DATA_OFF -- offset of the beginning of the data
238	*
239	* Case 2:
240	* This page contains the last page of a big data pair.
241	* There is no key, only the tail end of the data
242	* on this page.
243	*
244	* Page format is:
245	* DATA_OFF FULL_KEY_DATA <OVFL_PAGENO> <OVFLPAGE>
246	*
247	* DATA_OFF -- offset of the beginning of the data on
248	* this page
249	* FULL_KEY_DATA -- 3
250	* OVFL_PAGENO - page number of the next overflow page
251	* OVFLPAGE -- 0
252	*
253	* OVFL_PAGENO and OVFLPAGE are optional (they are
254	* not present if there is no next page).
255	*/
15637ed4 RG	256
	257	#define OVFLPAGE 0
	258	#define PARTIAL_KEY 1
	259	#define FULL_KEY 2
	260	#define FULL_KEY_DATA 3
	261	#define REAL_KEY 4
78ed81a3	262
15637ed4	263	/* Short hands for accessing structure */
78ed81a3	264	#define BSIZE hdr.bsize
	265	#define BSHIFT hdr.bshift
	266	#define DSIZE hdr.dsize
	267	#define SGSIZE hdr.ssize
	268	#define SSHIFT hdr.sshift
	269	#define LORDER hdr.lorder
	270	#define OVFL_POINT hdr.ovfl_point
	271	#define LAST_FREED hdr.last_freed
15637ed4 RG	272	#define MAX_BUCKET hdr.max_bucket
	273	#define FFACTOR hdr.ffactor
	274	#define HIGH_MASK hdr.high_mask
	275	#define LOW_MASK hdr.low_mask
	276	#define NKEYS hdr.nkeys
	277	#define HDRPAGES hdr.hdrpages
	278	#define SPARES hdr.spares
	279	#define BITMAPS hdr.bitmaps
	280	#define VERSION hdr.version
	281	#define MAGIC hdr.magic
	282	#define NEXT_FREE hdr.next_free
	283	#define H_CHARKEY hdr.h_charkey