usr.bin/doscmd/dispatch.h

   1 /*
   2 ** Copyright (c) 1996
   3 **      Michael Smith.  All rights reserved.
   4 **
   5 ** Redistribution and use in source and binary forms, with or without
   6 ** modification, are permitted provided that the following conditions
   7 ** are met:
   8 ** 1. Redistributions of source code must retain the above copyright
   9 **    notice, this list of conditions and the following disclaimer.
  10 ** 2. Redistributions in binary form must reproduce the above copyright
  11 **    notice, this list of conditions and the following disclaimer in the
  12 **    documentation and/or other materials provided with the distribution.
  13 **
  14 ** THIS SOFTWARE IS PROVIDED BY Michael Smith ``AS IS'' AND
  15 ** ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  16 ** IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  17 ** ARE DISCLAIMED.  IN NO EVENT SHALL Michael Smith BE LIABLE
  18 ** FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  19 ** DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  20 ** OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  21 ** HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  22 ** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  23 ** OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  24 ** SUCH DAMAGE.
  25 **
  26 ** $FreeBSD: src/usr.bin/doscmd/dispatch.h,v 1.2.2.1 2001/08/02 02:17:15 obrien Exp $
  27 ** $DragonFly: src/usr.bin/doscmd/dispatch.h,v 1.2 2003/06/17 04:29:25 dillon Exp $
  28 */
  29
  30 /*
  31 ** Interrupt dispatcher assistants.
  32 */
  33
  34
  35 /*
  36 ** Declare a static, initialised array of these, with one
  37 ** entry per function/subfunction.
  38 **
  39 ** The last element should be a dummy with a 'func' of -1
  40 */
  41 struct intfunc_table
  42 {
  43     int         func;                           /* interrupt function number */
  44     int         subfunc;                        /* subfunction number */
  45     int         (* handler)(regcontext_t *REGS);/* handling function */
  46     const char  *desc;                          /* textual description */
  47 };
  48 #define IFT_NOSUBFUNC   -1
  49
  50
  51 /*
  52 ** Declare a static array of 256 integers to use as a fast lookup
  53 ** into the table of handlers.
  54 **
  55 ** Call this function to initialise the lookup.  Note that the table
  56 ** must be arranged with all handlers for a given function together, and
  57 ** that the handler listed with IFT_NOSUBFUNC should be last.
  58 */
  59 static inline void
  60 intfunc_init(struct intfunc_table table[], int idx[])
  61 {
  62     int         hn;
  63
  64     for (hn = 0; hn < 256; hn++)                /* initialise all no-handler state */
  65         idx[hn] = -1;                           /* default to no handler */
  66
  67     for (hn = 0; table[hn].func >= 0; hn++)     /* walk list of handlers and add references */
  68         if (idx[table[hn].func] == -1 ) /* reference first handler */
  69             idx[table[hn].func] = hn;
  70 }
  71
  72 /*
  73 ** Call this to get an index matching the function/subfunction
  74 ** described by (sc), or -1 if none exist
  75 */
  76 static inline int
  77 intfunc_find(struct intfunc_table table[], int idx[], int func, int subfunc)
  78 {
  79     int ent = idx[func];                                /* look for handler */
  80
  81     while ((ent >= 0) &&                                /* scan entries for function */
  82            (table[ent].func == func)) {
  83
  84         if ((table[ent].subfunc == IFT_NOSUBFUNC) ||    /* handles all */
  85             (table[ent].subfunc == subfunc)) {          /* handles this one */
  86             return(ent);
  87         }
  88         ent++;
  89     }
  90     return(-1);
  91 }
  92
  93 /*
  94 ** A slower lookup for a set of function handlers, but one that requires
  95 ** no initialisation calls.
  96 ** Again, handlers with IFT_NOSUBFUNC should be listed after any with
  97 ** specific subfunction values.
  98 */
  99 static inline int
 100 intfunc_search(struct intfunc_table table[], int func, int subfunc)
 101 {
 102     int         ent;
 103
 104     for (ent = 0; table[ent].func >= 0; ent++)
 105         if ((table[ent].func == func) &&        /* matches required function */
 106             ((table[ent].subfunc == IFT_NOSUBFUNC) || table[ent].subfunc == subfunc))
 107             return(ent);
 108     return(-1);
 109 }
 110
 111