1: # include   <stdio.h>
   2: # include   "constants.h"
   3: # include       "globals.h"
   4: # include   <sccs.h>
   5: 
   6: SCCSID(@(#)getch.c	8.2	1/16/85)
   7: 
   8: 
   9: /*
  10: **  GETCH -- Get a character from the input stream
  11: **
  12: **	Parameters:
  13: **		none
  14: **
  15: **	Returns:
  16: **		the next character on the input stream, or
  17: **		the backed up character if there is one.
  18: **		EOF_TOK is returned on EOF.
  19: **
  20: **	Side Effects:
  21: **		If a backed up character exists, unloads it.
  22: **		*Line_pos is returned if Line_pos != 0
  23: **		and no backup character exists. Line_buf
  24: **		contains the line from which characters are being
  25: **		returned. A call with Line_pos == 0 forces
  26: **		reading of the next input line. Yyline is
  27: **		incremented when a newline is returned.
  28: **		If an EOF is in the middle of a line,
  29: **		then a newline will be appended.
  30: **
  31: **	Compilation Flags:
  32: **		xDEBUG -- to test Chardebug for
  33: **			returning activity of getch() and backup().
  34: */
  35: 
  36: 
  37: /* initializes peek buffer to be empty */
  38: int     Peekc [2]   = {-1, -1};
  39: 
  40: getch()
  41: {
  42:     register char   *cp;
  43:     register char   ch;
  44:     static      eoflag;
  45:     extern int  yyline;
  46:     extern FILE     *In_file;
  47: 
  48:     if (Peekc [0] >= 0)
  49:     {
  50:         /* have a backed up character */
  51:         ch = Peekc [0];
  52:         if (ch == '\n')
  53:             yyline += 1;
  54:         Peekc [0] = Peekc [1];
  55:         Peekc [1] = -1;
  56:     }
  57:     else
  58:     {
  59:         for ( ; ; )
  60:         {
  61:             /* no lookahead character */
  62:             if (!Line_pos)
  63:             {
  64:                 if (eoflag)
  65:                 {
  66:                     eoflag = 0;
  67: 
  68:                     /* try to restore previous file */
  69:                     if (!restoref())
  70:                         return (0);
  71: #					ifdef xDEBUG
  72:                     if (Chardebug || Lex_debug)
  73:                         printf("include file - pop\n");
  74: #					endif
  75:                 }
  76:                 for (cp = Line_buf; (*cp = getc(In_file)) != '\n'
  77:                             && *cp != EOF; cp++)
  78:                 {
  79:                     if (cp - Line_buf > sizeof Line_buf - 1)
  80:                     {
  81:                         yysemerr("WARNING : line too long, broken in two\n",
  82:                         0);
  83:                         break;
  84:                     }
  85:                 }
  86:                 if (*cp == EOF)
  87:                 {
  88:                     eoflag++;
  89:                     if (cp == Line_buf)
  90:                         /* EOF after '\n' */
  91:                         continue;
  92:                     /* EOF in middle of line */
  93:                     *cp = '\n';
  94:                 }
  95:                 Line_pos = Line_buf;
  96: 
  97:                 /* test for a "#include" line */
  98:                 if (tst_include())
  99:                 {
 100:                     /* Force reloading Line_buf */
 101:                     Line_pos = 0;
 102:                     eoflag = 0;
 103: #					ifdef xDEBUG
 104:                     if (Chardebug || Lex_debug)
 105:                         printf("include file - push\n");
 106: #					endif
 107:                     continue;
 108:                 }
 109:             }
 110:             cp =  Line_pos;
 111:             if (*cp == '\n')
 112:             {
 113:                 Line_pos = 0;
 114:                 yyline += 1;
 115:             }
 116:             else
 117:                 Line_pos++;
 118:             ch = *cp;
 119:             break;
 120:         }
 121:     }
 122:     ch &= I1MASK;
 123: 
 124: #	ifdef xDEBUG
 125:     if (Chardebug)
 126:         printf("getch - returning '%c'.\n", ch);
 127: #	endif
 128: 
 129:     return (ch);
 130: }
 131: 
 132: /*
 133: **  BACKUP -- Back up a character on the input stream.
 134: **	Backs up a single character into Peekc.
 135: **
 136: **	Parameters:
 137: **		ch - character to back up
 138: **
 139: **	Returns:
 140: **		none
 141: **
 142: **	Side Effects:
 143: **		pushes Peekc [0] to Peekc [1].
 144: **		sets Peekc [0] to backed up character.
 145: */
 146: 
 147: backup(ch)
 148: char        ch;
 149: {
 150:     extern int  yyline;
 151: 
 152: 
 153: #	ifdef xDEBUG
 154:     if (Chardebug)
 155:         printf("backed up : '%c'\n", ch);
 156: #	endif
 157: 
 158:     if (Peekc [1] >= 0)
 159:         syserr("backup buffer overflow on line %d, \"%c%c%c\".",
 160:         yyline, Peekc [0], Peekc [1], ch);
 161: 
 162:     Peekc [1] = Peekc [0];
 163:     if ((Peekc [0] = ch & I1MASK) == '\n')
 164:         --yyline;
 165: }
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