* Copyright (c) 1990 The Regents of the University of California.
* This code is derived from software contributed to Berkeley by
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* 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
* @(#)hash.h 5.4 (Berkeley) 3/12/91
typedef enum { HASH_GET
, HASH_PUT
, HASH_PUTNEW
, HASH_DELETE
,
HASH_FIRST
, HASH_NEXT
} ACTION
;/* Buffer Management structures */
typedef struct _bufhead 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 */
#define BUF_BUCKET 0x0004
#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 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 */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 whether 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 */#define MAX_BSIZE 65536 /* 2^16 */
#define DEF_BUFSIZE 65536 /* 64 K */
#define DEF_BUCKET_SIZE 256
#define DEF_BUCKET_SHIFT 8 /* log2(BUCKET) */
#define DEF_SEGSIZE_SHIFT 8 /* log2(SEGSIZE) */
#define CHARKEY "%$sniglet^&"
#define ALL_SET ((unsigned)0xFFFFFFFF)
#define PTROF(X) ((BUFHEAD *)((unsigned)(X)&~0x3))
#define ISMOD(X) ((unsigned)(X)&0x1)
#define DOMOD(X) (X = (char *)( (unsigned)X | 0x1))
#define ISDISK(X) ((unsigned)(X)&0x2)
#define DODISK(X) (X = (char *)( (unsigned)X | 0x2))
/* 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 SPLITNUM(N) (((unsigned)N) >> SPLITSHIFT)
#define OPAGENUM(N) (N & SPLITMASK)
#define OADDR_OF(S,O) ((unsigned)((unsigned)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
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
OVFL_PAGENO - page number of the next overflow page
FULL_KEY This must be the first key/data pair on the page. It
There is a complete key on the page but no data
(because it wouldn't fit). The next page contains
KEY_OFF FULL_KEY OVFL_PAGENO OVFL_PAGE
KEY_OFF -- offset of the beginning of the key
OVFL_PAGENO - page number of the next overflow page
This page contains no key, but part of a large
data field, which is continued on the next page.
DATA_OFF FULL_KEY OVFL_PAGENO OVFL_PAGE
KEY_OFF -- offset of the beginning of the data on
OVFL_PAGENO - page number of the next overflow page
FULL_KEY_DATA This must be the first key/data pair on the page.
This page contains a key and the beginning of the
data field, but the data field is continued on the
KEY_OFF FULL_KEY_DATA OVFL_PAGENO DATA_OFF
KEY_OFF -- offset of the beginning of the key
OVFL_PAGENO - page number of the next overflow page
DATA_OFF -- offset of the beginning of the data
This page contains the last page of a big data pair.
There is no key, only the tail end of the data
DATA_OFF FULL_KEY_DATA <OVFL_PAGENO> <OVFLPAGE>
DATA_OFF -- offset of the beginning of the data on
OVFL_PAGENO - page number of the next overflow page
OVFL_PAGENO and OVFLPAGE are optional (they are
not present if there is no next page).
/* Short hands for accessing structure */
#define BSHIFT hdr.bshift
#define SSHIFT hdr.sshift
#define LORDER hdr.lorder
#define MAX_BUCKET hdr.max_bucket
#define FFACTOR hdr.ffactor
#define HIGH_MASK hdr.high_mask
#define LOW_MASK hdr.low_mask
#define HDRPAGES hdr.hdrpages
#define SPARES hdr.spares
#define BITMAPS hdr.bitmaps
#define VERSION hdr.version
#define NEXT_FREE hdr.next_free
#define H_CHARKEY hdr.h_charkey
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