1: # include   <ingres.h>
   2: # include   <access.h>
   3: # include   <aux.h>
   4: # include   <lock.h>
   5: # include   <opsys.h>
   6: # include   <sccs.h>
   7: 
   8: SCCSID(@(#)accbuf.c	8.1	12/31/84)
   9: 
  10: 
  11: /*
  12: **	access method buffers and other data areas for buffer maintenance
  13: */
  14: 
  15: struct accbuf   Acc_buf[NACCBUFS];  /* the buffers */
  16: struct accbuf   *Acc_head;      /* head of usage list */
  17: struct accbuf   *Acc_tail;      /* tail of usage list */
  18: struct lockreq  Lock;
  19: 
  20: /*
  21: **	structs for admin file data
  22: */
  23: 
  24: struct admin    Admin;
  25: 
  26: /*
  27: **	global flag indicating if access methods
  28: **	have been initialized.
  29: */
  30: 
  31: int     Acc_init    =   FALSE;
  32: 
  33: char        Acclock;        /* locks enabled flag */
  34: int     Alockdes;       /* file descriptor for lock device*/
  35: int     Lockrel;        /* lock relations flag*/
  36: /*
  37: **	Flush the indicated page and reset all
  38: **	important information including the name
  39: **
  40: **	Trace Flags:
  41: **		20.0,1
  42: */
  43: 
  44: resetacc(buf)
  45: struct accbuf   *buf;
  46: {
  47:     register struct accbuf  *b;
  48:     register int        i;
  49: 
  50:     b = buf;
  51:     if (b == 0)
  52:         b = Acc_head;
  53: #	ifdef xATR3
  54:     if (tTf(20, 0))
  55:     {
  56:         printf("RESETACC: %x=", b);
  57:         dumptid((TID *) &b->rel_tupid);
  58:     }
  59: #	endif
  60: 
  61:     i = pageflush(b);   /* write the page if necessary */
  62:     b->rel_tupid = -1;
  63:     b->filedesc = -1;
  64:     b->thispage = -1;
  65:     b->bufstatus = 0;
  66:     return (i);
  67: }
  68: /*
  69: **	initialize access method data areas
  70: **
  71: **	Trace Flags:
  72: **		20.2,3
  73: */
  74: 
  75: acc_init()
  76: {
  77:     register struct accbuf  *last;
  78:     register struct accbuf  *b;
  79:     struct stat     stbuf;
  80:     extern int      errno;
  81: 
  82: #	ifdef xATR3
  83:     if (tTf(20, 2))
  84:         printf("ACC_INIT=%d\n", Acc_init);
  85: #	endif
  86: 
  87:     if (Acc_init)
  88:         return;     /* already initialized */
  89:     last = 0;
  90:     for (b = Acc_buf; b < &Acc_buf[NACCBUFS]; )
  91:     {
  92:         resetacc(b);
  93:         b->modb = last;
  94:         last = b;
  95:         b++;
  96:         last->modf = b;
  97:     }
  98:     last->modf = 0;
  99:     Acc_head = Acc_buf;
 100:     Acc_tail = last;
 101: 
 102:     /* get the admin file */
 103:     readadmin();
 104: 
 105:     /*
 106: 	** Set up locking information. If the database has concurrency
 107: 	** control then Lockrel = TRUE and the concurrency device will
 108: 	** be opened for writing. If there is no concurrency for the
 109: 	** data base or if the lock device isn't installed, then Alockdes
 110: 	** = -1 and no locking will (or can) occure.
 111: 	*/
 112:     Lockrel = (Admin.adhdr.adflags & A_DBCONCUR) != 0;
 113:     if (Lockrel && Alockdes < 0)
 114:         Alockdes = start_up_lock_driver();
 115:     errno = 0;  /* clear in case /dev/lock isn't available */
 116:     Acclock = TRUE;
 117:     stat(".", &stbuf);
 118:     bmove((char *) &stbuf, (char *) Lock.dbnode, 4);
 119: 
 120:     Acc_init = TRUE;
 121: }
 122: /*
 123: **	place buffer at top of LRU list
 124: */
 125: 
 126: top_acc(buf)
 127: struct accbuf   *buf;
 128: {
 129:     register struct accbuf  *b;
 130: 
 131:     b = buf;
 132: 
 133:     if (b == Acc_head)
 134:         return (0);
 135:     if (b == Acc_tail)
 136:         Acc_tail = b->modb;
 137:     else
 138:         b->modf->modb = b->modb;
 139:     b->modb->modf = b->modf;
 140:     Acc_head->modb = b;
 141:     b->modf = Acc_head;
 142:     Acc_head = b;
 143:     b->modb = 0;
 144:     return (0);
 145: }
 146: /*
 147: ** Flush_rel -- flush all pages associated with the relation
 148: **	described by the descriptor. If resetflag is TRUE,
 149: **	then the buffers are reset so the pages will not be
 150: **	found on subsequent calls to find_page().
 151: **
 152: **	Returns "or'ed" result from calls to pageflush.
 153: **
 154: **	Trace Flags:
 155: **		20.4-5
 156: */
 157: 
 158: flush_rel(d, resetflag)
 159: register DESC   *d;
 160: int     resetflag;
 161: {
 162:     register struct accbuf  *b;
 163:     register int        i;
 164: 
 165: #	ifdef xATR3
 166:     if (tTf(20, 4))
 167:         printf("flush_rel: rel=%.14s, reset=%d\n", d->reldum.relid, resetflag);
 168: #	endif
 169: 
 170:     i = 0;
 171:     for (b = Acc_head; b != NULL; b = b->modf)
 172:     {
 173:         if (d->reltid.ltid == b->rel_tupid)
 174:         {
 175:             if (resetflag)
 176:                 i |= resetacc(b);
 177:             else
 178:                 i |= pageflush(b);
 179:         }
 180:     }
 181: 
 182:     return (i);
 183: }
 184: /*
 185: **	CHOOSE_BUF -- Try to find an empty buffer for assignment.
 186: **		If there is no empty buffer, pick the last buffer
 187: **		in the LRU queue and make sure it is flushed.
 188: **
 189: **		Choose_buf guarantees that the buffer will be reset
 190: **		if it was used previously for a different relation.
 191: **
 192: **	Choose_buf -- choose a buffer for use with the given relation on
 193: **	the given page. The current algorithm is to allow only one buffer
 194: **	per relation. If a relation does not have a buffer, it is given a
 195: **	free one (if any) or else the Least Recently Used.
 196: **
 197: **	Trace Flags:
 198: **		29.0,1
 199: */
 200: 
 201: struct accbuf *
 202: choose_buf(dx, pageid)
 203: DESC    *dx;
 204: long    pageid;
 205: {
 206:     register struct accbuf  *b, *free;
 207:     register DESC       *d;
 208:     struct accbuf       *mine;
 209: 
 210:     d = dx;
 211:     free = mine = NULL;
 212: 
 213:     for (b = Acc_head; b != 0; b = b->modf)
 214:     {
 215:         if (b->rel_tupid == -1)
 216:             free = b;
 217:         else
 218:             if (d->reltid.ltid == b->rel_tupid)
 219:             {
 220:                 if (pageid == b->thispage)
 221:                 {
 222:                     if (d->relopn < 0)
 223:                         b->filedesc = d->relfp;
 224:                     return (b);
 225:                 }
 226:                 mine = b;
 227:             }
 228:     }
 229: 
 230:     /*
 231: 	** "Free" and "Mine" now reflect the current state of the buffers.
 232: 	** There is no buffer with the currently requested page
 233: 	*/
 234: 
 235: #	ifdef xATR3
 236:     if (tTf(29, 1))
 237:         printf("choosebuf free %x,mine %x\n", free, mine);
 238: #	endif
 239: 
 240:     /* no current buffer. Choose a free one or LRU */
 241:     if (free == NULL)
 242:         free = resetacc(Acc_tail) ? NULL : Acc_tail;    /* error if can't reset the LRU */
 243:     if (free)
 244:     {
 245:         /* copy relevant material (in this order in case of rubout) */
 246:         free->filedesc = d->relfp;
 247:         free->rel_tupid = d->reltid.ltid;
 248:     }
 249: 
 250: #	ifdef xATR1
 251:     if (tTf(29, 0))
 252:         printf("choosebuf:rets %x\n", free);
 253: #	endif
 254:     return (free);
 255: }
 256: /*
 257: **	ACC_CLOSE -- flush any buffers left around
 258: **		and then close the files for relation & attribute.
 259: **		The relation and attribute relation are normally left open
 260: **		until the end of an INGRES session but must be closed
 261: **		and re-opened in the dbu's whenever a new overlay is loaded.
 262: */
 263: 
 264: acc_close()
 265: {
 266:     register int    i;
 267: 
 268:     if (i = pageflush((struct accbuf *) NULL))
 269:         syserr("acc_close: pageflush %d", i);
 270:     close(Admin.adreld.relfp);
 271:     close(Admin.adattd.relfp);
 272:     Admin.adreld.relopn = Admin.adattd.relopn = 0;
 273:     if (Alockdes >= 0)
 274:         close(Alockdes);
 275:     Alockdes = -1;
 276:     Acc_init = FALSE;
 277:     return (0);
 278: }

Defined functions

acc_close defined in line 264; never used
top_acc defined in line 126; used 1 times

Defined variables

Acc_buf defined in line 15; used 3 times
Acc_head defined in line 16; used 8 times
Acc_init defined in line 31; used 4 times
Acc_tail defined in line 17; used 5 times
Acclock defined in line 33; used 1 times
Admin defined in line 24; used 5 times
Alockdes defined in line 34; used 5 times
Lock defined in line 18; used 1 times
Lockrel defined in line 35; used 2 times
Last modified: 1986-04-17
Generated: 2016-12-26
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