src/winmsgcond.c

   1 /* Copyright (c) 2013
   2  *      Mike Gerwitz (mtg@gnu.org)
   3  *
   4  * This file is part of GNU screen.
   5  *
   6  * GNU screen is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 3, or (at your option)
   9  * any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program (see the file COPYING); if not, see
  18  * <https://www.gnu.org/licenses>.
  19  *
  20  ****************************************************************
  21  */
  22
  23 #include "config.h"
  24
  25 #include "winmsgcond.h"
  26
  27 #include <assert.h>
  28 #include <stdlib.h>
  29
  30
  31 /* Initialize new condition and set to false; can be used to re-initialize a
  32  * condition for re-use */
  33 void wmc_init(WinMsgCond *cond, int offset)
  34 {
  35         cond->locked = false;
  36         cond->offset = offset;
  37         cond->initialized = true;
  38         wmc_clear(cond);
  39 }
  40
  41 /* Mark condition as true */
  42 void wmc_set(WinMsgCond *cond)
  43 {
  44         if (cond->locked)
  45                 return;
  46
  47         cond->state = true;
  48 }
  49
  50 /* Clear condition (equivalent to non-match) */
  51 void wmc_clear(WinMsgCond *cond)
  52 {
  53         if (cond->locked)
  54                 return;
  55
  56         cond->state = false;
  57 }
  58
  59 /* Determine if condition is active (has been initialized and can be used) */
  60 bool wmc_is_active(const WinMsgCond *cond)
  61 {
  62         return cond->initialized;
  63 }
  64
  65 /* Determine if a condition is true; the result is undefined if
  66  * !wmc_active(cond) */
  67 bool wmc_is_set(const WinMsgCond *cond)
  68 {
  69         return cond->state;
  70 }
  71
  72 /* "else" encounted */
  73 int wmc_else(WinMsgCond *cond, int offset, bool *changed)
  74 {
  75         assert(wmc_is_active(cond));
  76
  77         /* if we're already set, then there is no point in processing the "else";
  78          * we will therefore consider the previous condition to have succeeded, so
  79          * now keep track of the start of the else so that it may be clobbered
  80          * instead of the beginning of the true condition---that is, we're accepting
  81          * the destination string up until this point */
  82         if (wmc_is_set(cond)) {
  83                 wmc_init(cond, offset);  /* track this as a new condition */
  84                 cond->locked = true;  /* "else" shall never succeed at this point */
  85
  86                 /* we want to keep the string we have so far (the truth string) */
  87                 if (changed)
  88                         *changed = false;
  89                 return offset;
  90         }
  91
  92         /* now that we have reached "else" and are not true, we can never be true;
  93          * discard the truth part of the string */
  94         int prevoffset = cond->offset;
  95         cond->offset = offset;
  96
  97         /* the "else" part must always be true at this point, because the previous
  98          * condition failed */
  99         wmc_set(cond);
 100         cond->locked = true;
 101
 102         if (changed)
 103                 *changed = true;
 104         return prevoffset;
 105 }
 106
 107 /* End condition and determine if string should be reset or kept---if our value
 108  * is truthful, then accept the string, otherwise reject and reset to the
 109  * position that we were initialized with */
 110 int wmc_end(const WinMsgCond *cond, int offset, bool *changed)
 111 {
 112         bool set = wmc_is_set(cond);
 113         if (changed)
 114                 *changed = !set;
 115
 116         return (set) ? offset : cond->offset;
 117 }
 118
 119 /* Deactivate a condition, preventing its use; this allows a single allocation
 120  * to be re-used and ignored until activated */
 121 void wmc_deinit(WinMsgCond *cond)
 122 {
 123         cond->state = false;
 124         cond->offset = 0;
 125         cond->locked = true;
 126         cond->initialized = false;
 127 }