bwb_inp.c

这是一个简易的basic语言解释器, 可供我们学习和改进.

   int suppress_qm;
   static char tbuf[ MAXSTRINGSIZE + 1 ];
   static char pstring[ MAXSTRINGSIZE + 1 ];

#if INTENSIVE_DEBUG
   sprintf( bwb_ebuf, "in bwb_input(): enter function" );
   bwb_debug( bwb_ebuf );
#endif

   pstring[ 0 ] = '\0';

#if COMMON_CMDS

   /* advance beyond whitespace and check for the '#' sign */

   adv_ws( l->buffer, &( l->position ) );

   if ( l->buffer[ l->position ] == '#' )
      {
      ++( l->position );
      adv_element( l->buffer, &( l->position ), tbuf );
      pos = 0;
      v = bwb_exp( tbuf, FALSE, &pos );
      adv_ws( l->buffer, &( l->position ) );
      if ( l->buffer[ l->position ] == ',' )
         {
         ++( l->position );
         }
      else
         {
#if PROG_ERRORS
         bwb_error( "in bwb_input(): no comma after#n" );
#else
         bwb_error( err_syntax );
#endif
         return bwb_zline( l );
         }

      req_devnumber = (int) exp_getnval( v );

#if INTENSIVE_DEBUG
      sprintf( bwb_ebuf, "in bwb_input(): requested device number <%d>",
         req_devnumber );
      bwb_debug( bwb_ebuf );
#endif

      /* check the requested device number */

      if ( ( req_devnumber < 0 ) || ( req_devnumber >= DEF_DEVICES ))
         {
#if PROG_ERRORS
         bwb_error( "in bwb_input(): Requested device number is out if range." );
#else
         bwb_error( err_devnum );
#endif
         return bwb_zline( l );
         }

      if ( ( dev_table[ req_devnumber ].mode == DEVMODE_CLOSED ) ||
         ( dev_table[ req_devnumber ].mode == DEVMODE_AVAILABLE ) )
         {
#if PROG_ERRORS
         bwb_error( "in bwb_input(): Requested device number is not open." );
#else
         bwb_error( err_devnum );
#endif

         return bwb_zline( l );
         }

      if ( dev_table[ req_devnumber ].mode != DEVMODE_INPUT )
         {
#if PROG_ERRORS
         bwb_error( "in bwb_input(): Requested device is not open for INPUT." );
#else
         bwb_error( err_devnum );
#endif

         return bwb_zline( l );
         }

      /* look up the requested device in the device table */

      fp = dev_table[ req_devnumber ].cfp;

      }
   else
      {
      fp = stdin;
      }

#else
   fp = stdin;
#endif				/* COMMON_CMDS */

   /* if input is not from stdin, then branch to bwb_xinp() */

   if ( fp != stdin )
      {
      return bwb_xinp( l, fp );
      }

   /* from this point we presume that input is from stdin */

   /* check for a semicolon or a quotation mark, not in
      first position: this should indicate a prompt string */

   suppress_qm = is_prompt = FALSE;

   adv_ws( l->buffer, &( l->position ) );

   switch( l->buffer[ l->position ] )
      {
      case '\"':
         is_prompt = TRUE;
         break;

      case ';':

         /* AGENDA: add code to suppress newline if a
            semicolon is used here; this may not be possible
            using ANSI C alone, since it has not functions for
            unechoed console input. */

         is_prompt = TRUE;
         ++l->position;
         break;

      case ',':

         /* QUERY: why is this code here? the question mark should
            be suppressed if a comma <follows> the prompt string. */

#if INTENSIVE_DEBUG
         bwb_debug( "in bwb_input(): found initial comma" );
#endif
         suppress_qm = TRUE;
         ++l->position;
         break;
      }

   /* get prompt string and print it */

   if ( is_prompt == TRUE )
      {

      /* get string element */

      inp_const( l->buffer, tbuf, &( l->position ) );

      /* advance past semicolon to beginning of variable */

      /*--------------------------------------------------------*/
      /* Since inp_const was just called and inp_adv is called  */
      /* within that, it will have already noted and passed the */
      /* comma by the time it gets here.  Therefore one must    */
      /* refer instead to the last returned value for inp_adv!  */
      /* (JBV, 10/95)                                           */
      /*--------------------------------------------------------*/
      /* suppress_qm = inp_adv( l->buffer, &( l->position ) ); */
      suppress_qm = last_inp_adv_rval;

      /* print the prompt string */

      strncpy( pstring, tbuf, MAXSTRINGSIZE );
      }                                      /* end condition: prompt string */

   /* print out the question mark delimiter unless it has been
      suppressed */

   if ( suppress_qm != TRUE )
      {
      strncat( pstring, "? ", MAXSTRINGSIZE );
      }

#if INTENSIVE_DEBUG
   sprintf( bwb_ebuf, "in bwb_input(): ready to get input line" );
   bwb_debug( bwb_ebuf );
#endif

   /* read a line into the input buffer */

   bwx_input( pstring, tbuf );
   bwb_stripcr( tbuf );

#if INTENSIVE_DEBUG
   sprintf( bwb_ebuf, "in bwb_input(): received line <%s>", tbuf );
   bwb_debug( bwb_ebuf );
   bwb_debug( "Press RETURN: " );
   getchar();
#endif

   /* reset print column to account for LF at end of fgets() */

   * prn_getcol( stdout ) = 1;

   return inp_str( l, tbuf, l->buffer, &( l->position ) );

   }

/***************************************************************

        FUNCTION:       bwb_xinp()

        DESCRIPTION:    This function does the bulk of processing
                        for INPUT#, and so is file independent.

***************************************************************/

#if ANSI_C
static struct bwb_line *
bwb_xinp( struct bwb_line *l, FILE *f )
#else
static struct bwb_line *
bwb_xinp( l, f )
   struct bwb_line *l;
   FILE *f;
#endif
   {
   int loop;
   struct bwb_variable *v;
   char c;
   register int n;
   int *pp;
   int n_params;
   char tbuf[ MAXSTRINGSIZE + 1 ];

#if INTENSIVE_DEBUG
   sprintf( bwb_ebuf, "in bwb_xinp(): buffer <%s>",
      &( l->buffer[ l->position ] ) );
   bwb_debug( bwb_ebuf );
#endif

   /* loop through elements required */

   loop = TRUE;
   while ( loop == TRUE )
      {
      
      /* read a variable from the list */

      bwb_getvarname( l->buffer, tbuf, &( l->position ) );
      v = var_find( tbuf );

#if INTENSIVE_DEBUG
      sprintf( bwb_ebuf, "in bwb_xinp(): found variable name <%s>",
         v->name );
      bwb_debug( bwb_ebuf );
#endif

      /* read subscripts */

      adv_ws( l->buffer, &( l->position ) );
      if ( l->buffer[ l->position ] == '(' )
         {
#if INTENSIVE_DEBUG
         sprintf( bwb_ebuf, "in bwb_xinp(): variable <%s> has dimensions",
            v->name );
         bwb_debug( bwb_ebuf );
#endif
         dim_getparams( l->buffer, &( l->position ), &n_params, &pp );
         for ( n = 0; n < v->dimensions; ++n )
            {
            v->array_pos[ n ] = pp[ n ];
            }
         }

      inp_advws( f );

      /* perform type-specific input */

      switch( v->type )
         {
         case STRING:
            if ( inp_xgetc( f, TRUE ) != '\"' )
               {
#if PROG_ERRORS
               sprintf( bwb_ebuf, "in bwb_xinp(): expected quotation mark" );
               bwb_error( bwb_ebuf );
#else
               bwb_error( err_mismatch );
#endif
               }
            n = 0;
            while ( ( c = (char) inp_xgetc( f, TRUE )) != '\"' )
               {
               tbuf[ n ] = c;
               ++n;
               tbuf[ n ] = '\0';
               }
            str_ctob( var_findsval( v, v->array_pos ), tbuf );
#if INTENSIVE_DEBUG
            sprintf( bwb_ebuf, "in bwb_xinp(): read STRING <%s>",
               tbuf );
            bwb_debug( bwb_ebuf );
#endif
            inp_eatcomma( f );
            break;
         default:
            n = 0;
            while ( ( c = (char) inp_xgetc( f, FALSE )) != ',' )
               {
               tbuf[ n ] = c;
               ++n;
               tbuf[ n ] = '\0';
               }
#if INTENSIVE_DEBUG
            sprintf( bwb_ebuf, "in bwb_xinp(): read NUMBER <%s>",
               tbuf );
            bwb_debug( bwb_ebuf );
#endif
            /*------------------------------------------------------------*/
            /* atof call replaced by inp_numconst, gets all input formats */
            /* (JBV, 10/95)                                               */
            /*------------------------------------------------------------*/
            /* * var_findnval( v, v->array_pos ) = (bnumber) atof( tbuf ); */
            * var_findnval( v, v->array_pos ) = inp_numconst( tbuf );
            break;
         }				/* end of switch for type-specific input */

      /* check for comma */

      adv_ws( l->buffer, &( l->position ) );
      if ( l->buffer[ l->position ] == ',' )
         {
         ++( l->position );
         }
      else
         {
         loop = FALSE;
         }

      }

   /* return */

   return bwb_zline( l );

   }

/***************************************************************

        FUNCTION:       inp_advws()

	DESCRIPTION:    This C function advances past whitespace
			input from a particular file or device.

***************************************************************/

#if ANSI_C
static int
inp_advws( FILE *f )
#else
static int
inp_advws( f )
   FILE *f;
#endif
   {
   register int c;
   int loop;

   loop = TRUE;
   while ( loop == TRUE )
      {
      c = (char) inp_xgetc( f, TRUE );

      switch( c )
         {
         case '\n':
         case '\r':
         case ' ':
         case '\t':
            break;
         default:
            char_saved = TRUE;
            cs = c;
            loop = FALSE;
            break;
         }
      }   

   return TRUE;
   }

/***************************************************************

        FUNCTION:       inp_xgetc()

	DESCRIPTION:    This C function reads in a character from
			a specified file or device.

***************************************************************/

#if ANSI_C
static int
inp_xgetc( FILE *f, int is_string )
#else
static int
inp_xgetc( f, is_string )
   FILE *f;
   int is_string;
#endif
   {
   register int c;
   static int prev_eof = FALSE;

   if ( char_saved == TRUE )
      {
      char_saved = FALSE;
      return cs;
      }

   if ( feof( f ) != 0 )
      {
      if ( prev_eof == TRUE )
         {
         bwb_error( err_od );
         }
      else
         {
	 prev_eof = TRUE;
	 return (int) ',';
	 }
      }

   prev_eof = FALSE;

   c = fgetc( f );

   if ( is_string == TRUE )
      {
      return c;
      }
      
   switch( c )
      {
      case ' ':
      case '\n':
      case ',':
      case '\r':
         return ',';
      }

   return c;

   }

/***************************************************************

        FUNCTION:       inp_eatcomma()

	DESCRIPTION:    This C function advances beyond a comma
			input from a specified file or device.

***************************************************************/

#if ANSI_C
static int
inp_eatcomma( FILE *f )
#else
static int
inp_eatcomma( f )
   FILE *f;
#endif
   {
   char c;

   while ( ( c = (char) inp_xgetc( f, TRUE ) ) == ',' )
      {
      }
      
   char_saved = TRUE;
   cs = c;
      
   return TRUE;
   }

/***************************************************************