diplodocus.org Git - nmh/blob - docs/historical/mh-6.8.5/miscellany/less-177/signal.c

   1 /*
   2  * Routines dealing with signals.
   3  *
   4  * A signal usually merely causes a bit to be set in the "signals" word.
   5  * At some convenient time, the mainline code checks to see if any
   6  * signals need processing by calling psignal().
   7  * If we happen to be reading from a file [in iread()] at the time
   8  * the signal is received, we call intread to interrupt the iread.
   9  */
  10
  11 #include "less.h"
  12 #include <signal.h>
  13
  14 /*
  15  * "sigs" contains bits indicating signals which need to be processed.
  16  */
  17 public int sigs;
  18
  19 #define S_INTERRUPT     01
  20 #ifdef SIGTSTP
  21 #define S_STOP          02
  22 #endif
  23 #if defined(SIGWINCH) || defined(SIGWIND)
  24 #define S_WINCH         04
  25 #endif
  26
  27 extern int sc_width, sc_height;
  28 extern int swindow;
  29 extern int screen_trashed;
  30 extern int lnloop;
  31 extern int linenums;
  32 extern int scroll;
  33 extern int reading;
  34
  35 /*
  36  * Interrupt signal handler.
  37  */
  38         /* ARGSUSED*/
  39         static HANDLER
  40 u_interrupt(type)
  41         int type;
  42 {
  43         SIGNAL(SIGINT, u_interrupt);
  44         sigs |= S_INTERRUPT;
  45         if (reading)
  46                 intread();
  47 }
  48
  49         public void
  50 fake_interrupt()
  51 {
  52         sigs |= S_INTERRUPT;
  53 }
  54
  55 #ifdef SIGTSTP
  56 /*
  57  * "Stop" (^Z) signal handler.
  58  */
  59         /* ARGSUSED*/
  60         static HANDLER
  61 stop(type)
  62         int type;
  63 {
  64         SIGNAL(SIGTSTP, stop);
  65         sigs |= S_STOP;
  66         if (reading)
  67                 intread();
  68 }
  69 #endif
  70
  71 #ifdef SIGWINCH
  72 /*
  73  * "Window" change handler
  74  */
  75         /* ARGSUSED*/
  76         public HANDLER
  77 winch(type)
  78         int type;
  79 {
  80         SIGNAL(SIGWINCH, winch);
  81         sigs |= S_WINCH;
  82         if (reading)
  83                 intread();
  84 }
  85 #else
  86 #ifdef SIGWIND
  87 /*
  88  * "Window" change handler
  89  */
  90         /* ARGSUSED*/
  91         public HANDLER
  92 winch(type)
  93         int type;
  94 {
  95         SIGNAL(SIGWIND, winch);
  96         sigs |= S_WINCH;
  97         if (reading)
  98                 intread();
  99 }
 100 #endif
 101 #endif
 102
 103 /*
 104  * Set up the signal handlers.
 105  */
 106         public void
 107 init_signals(on)
 108         int on;
 109 {
 110         if (on)
 111         {
 112                 /*
 113                  * Set signal handlers.
 114                  */
 115                 (void) SIGNAL(SIGINT, u_interrupt);
 116 #ifdef SIGTSTP
 117                 (void) SIGNAL(SIGTSTP, stop);
 118 #endif
 119 #ifdef SIGWINCH
 120                 (void) SIGNAL(SIGWINCH, winch);
 121 #else
 122 #ifdef SIGWIND
 123                 (void) SIGNAL(SIGWIND, winch);
 124 #endif
 125 #endif
 126         } else
 127         {
 128                 /*
 129                  * Restore signals to defaults.
 130                  */
 131                 (void) SIGNAL(SIGINT, SIG_DFL);
 132 #ifdef SIGTSTP
 133                 (void) SIGNAL(SIGTSTP, SIG_DFL);
 134 #endif
 135 #ifdef SIGWINCH
 136                 (void) SIGNAL(SIGWINCH, SIG_IGN);
 137 #endif
 138 #ifdef SIGWIND
 139                 (void) SIGNAL(SIGWIND, SIG_IGN);
 140 #endif
 141         }
 142 }
 143
 144 /*
 145  * Process any signals we have received.
 146  * A received signal cause a bit to be set in "sigs".
 147  */
 148         public void
 149 psignals()
 150 {
 151         register int tsignals;
 152
 153         if ((tsignals = sigs) == 0)
 154                 return;
 155         sigs = 0;
 156
 157 #ifdef S_WINCH
 158         if (tsignals & S_WINCH)
 159         {
 160                 int old_width, old_height;
 161                 /*
 162                  * Re-execute get_term() to read the new window size.
 163                  */
 164                 old_width = sc_width;
 165                 old_height = sc_height;
 166                 swindow = -1;
 167                 get_term();
 168                 if (sc_width != old_width || sc_height != old_height)
 169                 {
 170                         scroll = (sc_height + 1) / 2;
 171                         screen_trashed = 1;
 172                 }
 173         }
 174 #endif
 175 #ifdef SIGTSTP
 176         if (tsignals & S_STOP)
 177         {
 178                 /*
 179                  * Clean up the terminal.
 180                  */
 181 #ifdef SIGTTOU
 182                 SIGNAL(SIGTTOU, SIG_IGN);
 183 #endif
 184                 lower_left();
 185                 clear_eol();
 186                 deinit();
 187                 flush();
 188                 raw_mode(0);
 189 #ifdef SIGTTOU
 190                 SIGNAL(SIGTTOU, SIG_DFL);
 191 #endif
 192                 SIGNAL(SIGTSTP, SIG_DFL);
 193                 kill(getpid(), SIGTSTP);
 194                 /*
 195                  * ... Bye bye. ...
 196                  * Hopefully we'll be back later and resume here...
 197                  * Reset the terminal and arrange to repaint the
 198                  * screen when we get back to the main command loop.
 199                  */
 200                 SIGNAL(SIGTSTP, stop);
 201                 raw_mode(1);
 202                 init();
 203                 screen_trashed = 1;
 204         }
 205 #endif
 206         if (tsignals & S_INTERRUPT)
 207         {
 208                 bell();
 209                 /*
 210                  * {{ You may wish to replace the bell() with
 211                  *    error("Interrupt", NULL_PARG); }}
 212                  */
 213
 214                 /*
 215                  * If we were interrupted while in the "calculating
 216                  * line numbers" loop, turn off line numbers.
 217                  */
 218                 if (lnloop)
 219                 {
 220                         lnloop = 0;
 221                         if (linenums == 2)
 222                                 screen_trashed = 1;
 223                         linenums = 0;
 224                         error("Line numbers turned off", NULL_PARG);
 225                 }
 226
 227         }
 228 }