hash.h

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/*-
 * Copyright (c) 1990, 1993, 1994
 * 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 8.3 (Berkeley) 5/31/94
 */

/* 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_int32_t 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 */
 u_int32_t 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_int16_t 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 */
 u_int32_t /* Hash function */
 (*hash)__P((const void *, size_t));
 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 errnum; /* Error Number -- for DBM
 * compatibility */
 int new_file; /* Indicates if fd is backing store
 * or no */
 int save_file; /* Indicates whether we need to flush
 * file at
 * exit */
 u_int32_t *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_int32_t)0xFFFFFFFF)
#define ALL_CLEAR 0

#define PTROF(X) ((BUFHEAD *)((ptrdiff_t)(X)&~0x3))
#define ISMOD(X) ((u_int32_t)(ptrdiff_t)(X)&0x1)
#define DOMOD(X) ((X) = (char *)((ptrdiff_t)(X)|0x1))
#define ISDISK(X) ((u_int32_t)(ptrdiff_t)(X)&0x2)
#define DODISK(X) ((X) = (char *)((ptrdiff_t)(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_int32_t)(N)) >> SPLITSHIFT)
#define OPAGENUM(N) ((N) & SPLITMASK)
#define OADDR_OF(S,O) ((u_int32_t)((u_int32_t)(S) << SPLITSHIFT) + (O))

#define BUCKET_TO_PAGE(B) \
 (B) + hashp->HDRPAGES + ((B) ? hashp->SPARES[__hash_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