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