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Annotation of 42BSD/ingres/source/iutil/opencat.c, revision 1.1.1.1

1.1       root        1: # include      <ingres.h>
                      2: # include      <aux.h>
                      3: # include      <opsys.h>
                      4: # include      <access.h>
                      5: # include      <sccs.h>
                      6: 
                      7: SCCSID(@(#)opencat.c   7.1     2/5/81)
                      8: 
                      9: /*
                     10: **  OPENCATALOG -- open system catalog
                     11: **
                     12: **     This routine opens a system catalog into a predetermined
                     13: **     cache.  If the catalog is already open, it is not reopened.
                     14: **
                     15: **     The 'Desxx' struct defines which relations may be opened
                     16: **     in this manner and is defined in .../source/aux.h.
                     17: **
                     18: **     The relation should not be closed after use (except in
                     19: **     special cases); however, it should be noclose'd after use
                     20: **     if the number of tuples in the catalog may have changed.
                     21: **
                     22: **     The Desxx structure has an alias field which
                     23: **     is the address of the 'Admin' structure cache which holds
                     24: **     the relation descriptor.  Thus, an openr need never actually
                     25: **     occur.
                     26: **
                     27: **     The actual desxx structure definition is in the file
                     28: **     
                     29: **             catalog_desc.c
                     30: **
                     31: **     which defines which relations can be cached and if any
                     32: **     alias descriptors exist for the relations. That file
                     33: **     can be redefined to include various caching.
                     34: **
                     35: **
                     36: **     Parameters:
                     37: **             name -- the name of the relation to open.  It must
                     38: **                     match one of the names in the Desxx
                     39: **                     structure.
                     40: **             mode -- just like 'mode' to openr.  If zero, it
                     41: **                     is opened read-only; if two, it is opened
                     42: **                     read/write.  In fact, the catalog is always
                     43: **                     opened read/write, but the flags are set
                     44: **                     right for concurrency to think that you are
                     45: **                     using it as you have declared.
                     46: **
                     47: **     Returns:
                     48: **             none
                     49: **
                     50: **     Side Effects:
                     51: **             A relation is (may be) opened.
                     52: **
                     53: **     Trace Flags:
                     54: **             none
                     55: */
                     56: 
                     57: opencatalog(name, mode)
                     58: char   *name;
                     59: int    mode;
                     60: {
                     61:        int                     i;
                     62:        register DESC           *d;
                     63:        register char           *n;
                     64:        register struct desxx   *p;
                     65:        extern struct desxx     Desxx[];
                     66:        extern long             CmOfiles;
                     67: 
                     68:        n = name;
                     69: 
                     70:        /* find out which descriptor it is */
                     71:        for (p = Desxx; p->cach_relname; p++)
                     72:                if (sequal(n, p->cach_relname))
                     73:                        break;
                     74:        if (!p->cach_relname)
                     75:                syserr("opencatalog: (%s)", n);
                     76: 
                     77:        d = p->cach_desc;
                     78: 
                     79:        /* if it's already open, just return */
                     80:        if (d->relopn)
                     81:        {
                     82:                clearkeys(d);
                     83:        }
                     84:        else
                     85:        {
                     86:                /* not open, open it */
                     87:                if (p->cach_alias)
                     88:                {
                     89:                        acc_init();
                     90:                        bmove((char *) p->cach_alias, (char *) d, sizeof (*d));
                     91:                }
                     92:                else
                     93:                {
                     94:                        if ((i = openr(d, 2, n)) != 0)
                     95:                                syserr("opencatalog: openr(%s) %d", n, i);
                     96:                }
                     97: 
                     98:                /* mark it as an open file */
                     99:                CmOfiles |= 1 << d->relfp;
                    100:        }
                    101: 
                    102:        /* determine the mode to mark it as for concurrency */
                    103:        switch (mode)
                    104:        {
                    105:          case 0:       /* read only */
                    106:                d->relopn = abs(d->relopn);
                    107:                break;
                    108: 
                    109:          case 2:       /* read-write */
                    110:                d->relopn = -abs(d->relopn);
                    111:                break;
                    112: 
                    113:          default:
                    114:                syserr("opencatalog(%s): mode %d", n, mode);
                    115:        }
                    116: 
                    117:        return;
                    118: }

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