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.

        FUNCTION:       inp_str()

        DESCRIPTION:    This function does INPUT processing
                        from a determined string of input
                        data and a determined variable list
                        (both in memory).  This presupposes
			that input has been taken from stdin,
			not from a disk file or device.

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

#if ANSI_C
static struct bwb_line *
inp_str( struct bwb_line *l, char *input_buffer, char *var_list, int *vl_position )
#else
static struct bwb_line *
inp_str( l, input_buffer, var_list, vl_position )
   struct bwb_line *l;
   char *input_buffer;
   char *var_list;
   int *vl_position;
#endif
   {
   int i;
   register int n;
   struct bwb_variable *v;
   int loop;
   int *pp;
   int n_params;
   char ttbuf[ MAXSTRINGSIZE + 1 ];		/* build element */
   char varname[ MAXSTRINGSIZE + 1 ];		/* build element */

#if INTENSIVE_DEBUG
   sprintf( bwb_ebuf, "in inp_str(): received line <%s>",
      l->buffer );
   bwb_debug( bwb_ebuf );
   sprintf( bwb_ebuf, "in inp_str(): received variable list <%s>.",
      &( var_list[ *vl_position ] ) );
   bwb_debug( bwb_ebuf );
   sprintf( bwb_ebuf, "in inp_str(): received input buffer  <%s>.",
      input_buffer );
   bwb_debug( bwb_ebuf );
#endif

   /* Read elements, and assign them to variables */

   i = 0;
   loop = TRUE;
   while ( loop == TRUE )
      {

      /* get a variable name from the list */

      bwb_getvarname( var_list, varname, vl_position );    /* get name */
      v = var_find( varname );

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

      /* read subscripts if appropriate */

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

      /* build string from input buffer in ttbuf */

      n = 0;
      ttbuf[ 0 ] = '\0';
      while ( ( input_buffer[ i ] != ',' )
         &&   ( input_buffer[ i ] != '\0' ))
         {
         ttbuf[ n ] = input_buffer[ i ];
         ++n;
         ++i;
         ttbuf[ n ] = '\0';
         }

#if INTENSIVE_DEBUG
      sprintf( bwb_ebuf, "in inp_str(): string for input <%s>",
         ttbuf );
      bwb_debug( bwb_ebuf );
#endif

      /* perform type-specific input */

      inp_assign( ttbuf, v );

      /* check for commas in variable list and input list and advance */

      adv_ws( var_list, vl_position );
      switch( var_list[ *vl_position ] )
	 {
	 case '\n':
	 case '\r':
	 case '\0':
	 case ':':
	    loop = FALSE;
	    break;
	 case ',':
	    ++( *vl_position );
	    break;
         }
      adv_ws( var_list, vl_position );

      adv_ws( input_buffer, &i );
      switch ( input_buffer[ i ] )
	 {
	 case '\n':
	 case '\r':
	 case '\0':
	 case ':':
	    loop = FALSE;
	    break;
	 case ',':
	    ++i;
	    break;
	 }
      adv_ws( input_buffer, &i );

      }

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

   /* return */

   return bwb_zline( l );

   }

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

        FUNCTION:       inp_assign()

        DESCRIPTION:    This function assigns the value of a
                        numerical or string constant to a
                        variable.


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

#if ANSI_C
static int
inp_assign( char *b, struct bwb_variable *v )
#else
static int
inp_assign( b, v )
   char *b;
   struct bwb_variable *v;
#endif
   {

   switch( v->type )
      {
      case STRING:
         str_ctob( var_findsval( v, v->array_pos ), b );
         break;

      case NUMBER:
         if ( strlen( b ) == 0 )
            {
            *( var_findnval( v, v->array_pos )) = (bnumber) 0.0;
            }
         else
            {
            /*------------------------------------------------------------*/
            /* atof call replaced by inp_numconst, gets all input formats */
            /* (JBV, 10/95)                                               */
            /*------------------------------------------------------------*/
            /* *( var_findnval( v, v->array_pos )) = (bnumber) atof( b ); */
            *( var_findnval( v, v->array_pos )) = inp_numconst( b );
            }
         break;

      default:
#if PROG_ERRORS
         sprintf( bwb_ebuf, "in inp_assign(): variable <%s> of unknown type",
            v->name );
         bwb_error( bwb_ebuf );
#else
         bwb_error( err_mismatch );
#endif
         return FALSE;

      }

   return FALSE;

   }

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

        FUNCTION:       inp_adv()

        DESCRIPTION:    This function advances the string pointer
                        past whitespace and the item delimiter
                        (comma).

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

#if ANSI_C
int
inp_adv( char *b, int *c )
#else
int
inp_adv( b, c )
   char *b;
   int *c;
#endif
   {
   int rval;

   rval = FALSE;

   while( TRUE )
      {
      switch( b[ *c ] )
         {
         case ' ':              /* whitespace */
         case '\t':
         case ';':              /* semicolon, end of prompt string */
            ++*c;
            break;
         case ',':              /* comma, variable delimiter */
            rval = TRUE;
            ++*c;
            break;
         case '\0':		/* end of line */
         case ':': 		/* end of line segment */
            rval = TRUE;
            last_inp_adv_rval = rval; /* JBV */
            return rval;
         default:
            last_inp_adv_rval = rval; /* JBV */
            return rval;
         }
      }
   }

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

        FUNCTION:       inp_const()

        DESCRIPTION:    This function reads a numerical or string
                        constant from <m_buffer> into <s_buffer>,
                        incrementing <position> appropriately.

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

#if ANSI_C
static int
inp_const( char *m_buffer, char *s_buffer, int *position )
#else
static int
inp_const( m_buffer, s_buffer, position )
   char *m_buffer;
   char *s_buffer;
   int *position;
#endif
   {
   int string;
   int s_pos;
   int loop;

#if INTENSIVE_DEBUG
   sprintf( bwb_ebuf, "in inp_const(): received argument <%s>.",
      &( m_buffer[ *position ] ) );
   bwb_debug( bwb_ebuf );
#endif

   string = FALSE;

   /* first detect string constant */

   if ( m_buffer[ *position ] == '\"' )
      {
      string = TRUE;
      ++( *position );
      }
   else
      {
      string = FALSE;
      }

   /* build the constant string */

   s_buffer[ 0 ] = '\0';
   s_pos = 0;
   loop = TRUE;

   while ( loop == TRUE )
      {

      switch ( m_buffer[ *position ] )
         {
         case '\0':                     /* end of string */
         case '\n':
         case '\r':
            return TRUE;
         case ' ':                      /* whitespace */
         case '\t':
         case ',':                      /* or end of argument */
            if ( string == FALSE )
               {
               return TRUE;
               }
            else
               {
               s_buffer[ s_pos ] = m_buffer[ *position ];
               ++( *position );
               ++s_buffer;
               s_buffer[ s_pos ] = '\0';
               }
            break;
         case '\"':
            if ( string == TRUE )
               {
               ++( *position );                 /* advance beyond quotation mark */
               inp_adv( m_buffer, position );
               return TRUE;
               }
            else
               {
#if PROG_ERRORS
               sprintf( bwb_ebuf, "Unexpected character in numerical constant." );
               bwb_error( bwb_ebuf );
#else
               bwb_error( err_syntax );
#endif
               return FALSE;
               }
         default:
            s_buffer[ s_pos ] = m_buffer[ *position ];
            ++( *position );
            ++s_buffer;
            s_buffer[ s_pos ] = '\0';
            break;
         }

      }

   return FALSE;

   }

#if COMMON_CMDS

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

        FUNCTION:       bwb_line()

        DESCRIPTION:    This function implements the BASIC LINE
                        INPUT statement.

	SYNTAX:         LINE INPUT [[#] device-number,]["prompt string";] string-variable$

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

#if ANSI_C
struct bwb_line *
bwb_line( struct bwb_line *l )
#else
struct bwb_line *
bwb_line( l )
   struct bwb_line *l;
#endif
   {
   int dev_no;
   struct bwb_variable *v;
   FILE *inp_device;
   char tbuf[ MAXSTRINGSIZE + 1 ];
   char pstring[ MAXSTRINGSIZE + 1 ];
   struct exp_ese *e; /* JBV */
   int pos; /* JBV */

   /* assign default values */

   inp_device = stdin;

   pstring[ 0 ] = '\0';

   /* advance to first element (INPUT statement) */

   adv_element( l->buffer, &( l->position ), tbuf );
   bwb_strtoupper( tbuf );
   if ( strcmp( tbuf, "INPUT" ) != 0 )
      {
      bwb_error( err_syntax );
      return bwb_zline( l );
      }
   adv_ws( l->buffer, &( l->position ) );

   /* check for semicolon in first position */

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

   /* else check for# for file number in first position */

   else if ( l->buffer[ l->position ] == '#' )
      {
      ++l->position;
      adv_element( l->buffer, &( l->position ), tbuf );
      adv_ws( l->buffer, &( l->position ));
      /* dev_no = atoi( tbuf ); */  /* We really need more, added next (JBV) */
      pos = 0;
      e = bwb_exp( tbuf, FALSE, &pos );
      dev_no = (int) exp_getnval( e );

#if INTENSIVE_DEBUG
      sprintf( bwb_ebuf, "in bwb_line(): file number requested <%d>", dev_no );
      bwb_debug( bwb_ebuf );
#endif

      if ( dev_table[ dev_no ].cfp == NULL )
         {
         bwb_error( err_dev );
         return bwb_zline( l );
         }
      else
         {
         inp_device = dev_table[ dev_no ].cfp;
         }
      }

   /* check for comma */

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

   /* check for quotation mark indicating prompt */

   if ( l->buffer[ l->position ] == '\"' )
      {
      inp_const( l->buffer, pstring, &( l->position ) );
      }

   /* read the variable for assignment */

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

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

#if INTENSIVE_DEBUG
   sprintf( bwb_ebuf, "in bwb_line(): variable buffer <%s>", tbuf );
   bwb_debug( bwb_ebuf );
#endif
   v = var_find( tbuf );