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
 * numbered 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