libbb/read_key.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * Utility routines.
   4  *
   5  * Copyright (C) 2008 Rob Landley <rob@landley.net>
   6  * Copyright (C) 2008 Denys Vlasenko <vda.linux@googlemail.com>
   7  *
   8  * Licensed under GPL version 2, see file LICENSE in this tarball for details.
   9  */
  10 #include "libbb.h"
  11
  12 int FAST_FUNC read_key(int fd, smalluint *nbuffered, char *buffer)
  13 {
  14         struct pollfd pfd;
  15         const char *seq;
  16         int n;
  17         int c;
  18
  19         /* Known escape sequences for cursor and function keys */
  20         static const char esccmds[] ALIGN1 = {
  21                 'O','A'        |0x80,KEYCODE_UP      ,
  22                 'O','B'        |0x80,KEYCODE_DOWN    ,
  23                 'O','C'        |0x80,KEYCODE_RIGHT   ,
  24                 'O','D'        |0x80,KEYCODE_LEFT    ,
  25                 'O','H'        |0x80,KEYCODE_HOME    ,
  26                 'O','F'        |0x80,KEYCODE_END     ,
  27 #if 0
  28                 'O','P'        |0x80,KEYCODE_FUN1    ,
  29                 /* [ESC] ESC O [2] P - [Alt-][Shift-]F1 */
  30                 /* Ctrl- seems to not affect sequences */
  31                 'O','Q'        |0x80,KEYCODE_FUN2    ,
  32                 'O','R'        |0x80,KEYCODE_FUN3    ,
  33                 'O','S'        |0x80,KEYCODE_FUN4    ,
  34 #endif
  35                 '[','A'        |0x80,KEYCODE_UP      ,
  36                 '[','B'        |0x80,KEYCODE_DOWN    ,
  37                 '[','C'        |0x80,KEYCODE_RIGHT   ,
  38                 '[','D'        |0x80,KEYCODE_LEFT    ,
  39                 '[','H'        |0x80,KEYCODE_HOME    , /* xterm */
  40                 /* [ESC] ESC [ [2] H - [Alt-][Shift-]Home */
  41                 '[','F'        |0x80,KEYCODE_END     , /* xterm */
  42                 '[','1','~'    |0x80,KEYCODE_HOME    , /* vt100? linux vt? or what? */
  43                 '[','2','~'    |0x80,KEYCODE_INSERT  ,
  44                 '[','3','~'    |0x80,KEYCODE_DELETE  ,
  45                 /* [ESC] ESC [ 3 [;2] ~ - [Alt-][Shift-]Delete */
  46                 '[','4','~'    |0x80,KEYCODE_END     , /* vt100? linux vt? or what? */
  47                 '[','5','~'    |0x80,KEYCODE_PAGEUP  ,
  48                 '[','6','~'    |0x80,KEYCODE_PAGEDOWN,
  49                 '[','7','~'    |0x80,KEYCODE_HOME    , /* vt100? linux vt? or what? */
  50                 '[','8','~'    |0x80,KEYCODE_END     , /* vt100? linux vt? or what? */
  51 #if 0
  52                 '[','1','1','~'|0x80,KEYCODE_FUN1    ,
  53                 '[','1','2','~'|0x80,KEYCODE_FUN2    ,
  54                 '[','1','3','~'|0x80,KEYCODE_FUN3    ,
  55                 '[','1','4','~'|0x80,KEYCODE_FUN4    ,
  56                 '[','1','5','~'|0x80,KEYCODE_FUN5    ,
  57                 /* [ESC] ESC [ 1 5 [;2] ~ - [Alt-][Shift-]F5 */
  58                 '[','1','7','~'|0x80,KEYCODE_FUN6    ,
  59                 '[','1','8','~'|0x80,KEYCODE_FUN7    ,
  60                 '[','1','9','~'|0x80,KEYCODE_FUN8    ,
  61                 '[','2','0','~'|0x80,KEYCODE_FUN9    ,
  62                 '[','2','1','~'|0x80,KEYCODE_FUN10   ,
  63                 '[','2','3','~'|0x80,KEYCODE_FUN11   ,
  64                 '[','2','4','~'|0x80,KEYCODE_FUN12   ,
  65 #endif
  66                 0
  67         };
  68
  69         n = 0;
  70         if (nbuffered)
  71                 n = *nbuffered;
  72         if (n == 0) {
  73                 /* If no data, block waiting for input. If we read more
  74                  * than the minimal ESC sequence size, the "n=0" below
  75                  * would instead have to figure out how much to keep,
  76                  * resulting in larger code. */
  77                 n = safe_read(fd, buffer, 3);
  78                 if (n <= 0)
  79                         return -1;
  80         }
  81
  82         /* Grab character to return from buffer */
  83         c = (unsigned char)buffer[0];
  84         n--;
  85         if (n)
  86                 memmove(buffer, buffer + 1, n);
  87
  88         /* Only ESC starts ESC sequences */
  89         if (c != 27)
  90                 goto ret;
  91
  92         /* Loop through known ESC sequences */
  93         pfd.fd = fd;
  94         pfd.events = POLLIN;
  95         seq = esccmds;
  96         while (*seq != '\0') {
  97                 /* n - position in sequence we did not read yet */
  98                 int i = 0; /* position in sequence to compare */
  99
 100                 /* Loop through chars in this sequence */
 101                 while (1) {
 102                         /* So far escape sequence matched up to [i-1] */
 103                         if (n <= i) {
 104                                 /* Need more chars, read another one if it wouldn't block.
 105                                  * Note that escape sequences come in as a unit,
 106                                  * so if we block for long it's not really an escape sequence.
 107                                  * Timeout is needed to reconnect escape sequences
 108                                  * split up by transmission over a serial console. */
 109                                 if (safe_poll(&pfd, 1, 50) == 0) {
 110                                         /* No more data!
 111                                          * Array is sorted from shortest to longest,
 112                                          * we can't match anything later in array,
 113                                          * break out of both loops. */
 114                                         goto ret;
 115                                 }
 116                                 errno = 0;
 117                                 if (safe_read(fd, buffer + n, 1) <= 0) {
 118                                         /* If EAGAIN, then fd is O_NONBLOCK and poll lied:
 119                                          * in fact, there is no data. */
 120                                         if (errno != EAGAIN)
 121                                                 c = -1; /* otherwise it's EOF/error */
 122                                         goto ret;
 123                                 }
 124                                 n++;
 125                         }
 126                         if (buffer[i] != (seq[i] & 0x7f)) {
 127                                 /* This seq doesn't match, go to next */
 128                                 seq += i;
 129                                 /* Forward to last char */
 130                                 while (!(*seq & 0x80))
 131                                         seq++;
 132                                 /* Skip it and the keycode which follows */
 133                                 seq += 2;
 134                                 break;
 135                         }
 136                         if (seq[i] & 0x80) {
 137                                 /* Entire seq matched */
 138                                 c = (signed char)seq[i+1];
 139                                 n = 0;
 140                                 /* n -= i; memmove(...);
 141                                  * would be more correct,
 142                                  * but we never read ahead that much,
 143                                  * and n == i here. */
 144                                 goto ret;
 145                         }
 146                         i++;
 147                 }
 148         }
 149         /* We did not find matching sequence, it was a bare ESC.
 150          * We possibly read and stored more input in buffer[]
 151          * by now. */
 152
 153  ret:
 154         if (nbuffered)
 155                 *nbuffered = n;
 156         return c;
 157 }