bwb_var.c

这是一个简易的basic语言解释器, 可供我们学习和改进.

      v->name, v->type, v->dimensions );
   bwb_debug( bwb_ebuf );
   getchar();
#endif

   return v;

   }

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

        FUNCTION:       var_new()

	DESCRIPTION:    This function assigns memory for a new variable.

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

#if ANSI_C
struct bwb_variable *
var_new( char *name )
#else
struct bwb_variable *
var_new( name )
   char *name;
#endif
   {
   struct bwb_variable *v;

   /* get memory for new variable */

   /* Revised to CALLOC pass-thru call by JBV */
   if ( ( v = (struct bwb_variable *) CALLOC( 1, sizeof( struct bwb_variable ), "var_new" ))
      == NULL )
      {
      bwb_error( err_getmem );
      return NULL;
      }

   /* copy the name into the appropriate structure */

   strcpy( v->name, name );

   /* set memory in the new variable */

   var_make( v, (int) v->name[ strlen( v->name ) - 1 ] );

   /* and return */

   return v;

   }

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

        FUNCTION:       bwb_isvar()

	DESCRIPTION:    This function determines if the string
			in 'buffer' is the name of a previously-
			existing variable.

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

#if ANSI_C
int
bwb_isvar( char *buffer )
#else
int
bwb_isvar( buffer )
   char *buffer;
#endif
   {
   struct bwb_variable *v;

   /* run through the variable list and try to find a match */

   for ( v = CURTASK var_start.next; v != &CURTASK var_end; v = v->next )
      {

      if ( strcmp( v->name, buffer ) == 0 )
         {
         return TRUE;
         }

      }

   /* search failed */

   return FALSE;

   }

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

	FUNCTION:       var_getnval()

	DESCRIPTION:    This function returns the current value of
			the variable argument as a number.

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

#if ANSI_C
bnumber
var_getnval( struct bwb_variable *nvar )
#else
bnumber
var_getnval( nvar )
   struct bwb_variable *nvar;
#endif
   {

   switch( nvar->type )
      {
      case NUMBER:
         return *( var_findnval( nvar, nvar->array_pos ) );
      }

#if PROG_ERRORS
   sprintf( bwb_ebuf, "in var_getnval(): type is <%d>=<%c>.",
      nvar->type, nvar->type );
   bwb_error( bwb_ebuf );
#else
   bwb_error( err_mismatch );
#endif


   return (bnumber) 0.0;

   }

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

	FUNCTION:       var_getsval()

	DESCRIPTION:    This function returns the current value of
			the variable argument as a pointer to a BASIC
			string structure.

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

#if ANSI_C
bstring *
var_getsval( struct bwb_variable *nvar )
#else
bstring *
var_getsval( nvar )
   struct bwb_variable *nvar;
#endif
   {
   static bstring b;

   b.rab = FALSE;

   switch( nvar->type )
      {
      case STRING:
	 return var_findsval( nvar, nvar->array_pos );
      case NUMBER:
	 sprintf( bwb_ebuf, "%*f ", prn_precision( nvar ),
	    *( var_findnval( nvar, nvar->array_pos ) ) );
	 str_ctob( &b, bwb_ebuf );
	 return &b;
      default:
#if PROG_ERRORS
	 sprintf( bwb_ebuf, "in var_getsval(): type is <%d>=<%c>.",
	    nvar->type, nvar->type );
	 bwb_error( bwb_ebuf );
#else
	 bwb_error( err_mismatch );
#endif
	 return NULL;
      }

   }

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

	FUNCTION:	bwb_dim()

	DESCRIPTION:	This function implements the BASIC DIM
			statement, allocating memory for a
			dimensioned array of variables.

	SYNTAX:		DIM variable(elements...)[variable(elements...)]...

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

#if ANSI_C
struct bwb_line *
bwb_dim( struct bwb_line *l )
#else
struct bwb_line *
bwb_dim( l )
   struct bwb_line *l;
#endif
   {
   register int n;
   static int n_params;                         /* number of parameters */
   static int *pp;                              /* pointer to parameter values */
   struct bwb_variable *newvar;
   bnumber *np;
   int loop;
   int old_name, old_dimensions;
   char tbuf[ MAXSTRINGSIZE + 1 ];

#if INTENSIVE_DEBUG
   sprintf( bwb_ebuf, "in bwb_dim(): entered function." );
   bwb_debug( bwb_ebuf );
#endif

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

      old_name = FALSE;

      /* Get variable name */

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

      /* check for previously used variable name */

      if ( bwb_isvar( tbuf ) == TRUE )
         {
#if INTENSIVE_DEBUG
         sprintf( bwb_ebuf, "in bwb_dim(): variable name is already used.",
            l->number );
         bwb_debug( bwb_ebuf );
#endif
         old_name = TRUE;
         }

      /* get the new variable */

      newvar = var_find( tbuf );

#if INTENSIVE_DEBUG
      sprintf( bwb_ebuf, "in bwb_dim(): new variable name is <%s>.",
         newvar->name );
      bwb_debug( bwb_ebuf );
#endif

      /* note that DIM has been called */

      dimmed = TRUE;

      /* read parameters */

      old_dimensions = newvar->dimensions;
      dim_getparams( l->buffer, &( l->position ), &n_params, &pp );
      newvar->dimensions = n_params;

      /* Check parameters for an old variable name */

      if ( old_name == TRUE )
         {

         /* check to be sure the number of dimensions is the same */

         if ( newvar->dimensions != old_dimensions )
            {
#if PROG_ERRORS
            sprintf( bwb_ebuf, "in bwb_dim(): variable <%s> cannot be re-dimensioned",
               newvar->name );
            bwb_error( bwb_ebuf );
#else
            bwb_error( err_redim );
#endif
            }

         /* check to be sure sizes for the old variable are the same */

         for ( n = 0; n < newvar->dimensions; ++n )
            {
#if INTENSIVE_DEBUG
            sprintf( bwb_ebuf, "in bwb_dim(): old var <%s> parameter <%d> size <%d>.",
               newvar->name, n, pp[ n ] );
            bwb_debug( bwb_ebuf );
#endif
            if ( ( pp[ n ] + ( 1 - dim_base )) != newvar->array_sizes[ n ] )
               {
#if PROG_ERRORS
               sprintf( bwb_ebuf, "in bwb_dim(): variable <%s> parameter <%d> cannot be resized",
                  newvar->name, n );
               bwb_error( bwb_ebuf );
#else
               bwb_error( err_redim );
#endif
               }
            }

         }         /* end of conditional for old variable */


      /* a new variable */

      else
         {

         /* assign memory for parameters */

         /* Revised to CALLOC pass-thru call by JBV */
         if ( ( newvar->array_sizes = (int *) CALLOC( n_params, sizeof( int ), "bwb_dim"  )) == NULL )
            {
#if PROG_ERRORS
            sprintf( bwb_ebuf, "in line %d: Failed to find memory for array_sizes for <%s>",
               l->number, newvar->name );
            bwb_error( bwb_ebuf );
#else
            bwb_error( err_getmem );
#endif
            return bwb_zline( l );
            }

         for ( n = 0; n < newvar->dimensions; ++n )
            {
            newvar->array_sizes[ n ] = pp[ n ] + ( 1 - dim_base );
#if INTENSIVE_DEBUG
            sprintf( bwb_ebuf, "in bwb_dim(): array_sizes dim <%d> value <%d>",
               n, newvar->array_sizes[ n ] );
            bwb_debug( bwb_ebuf );
#endif
            }

         /* assign memory for current position */

         /* Revised to CALLOC pass-thru call by JBV */
         if ( ( newvar->array_pos = (int *) CALLOC( n_params, sizeof( int ), "bwb_dim" )) == NULL )
            {
#if PROG_ERRORS
            sprintf( bwb_ebuf, "in line %d: Failed to find memory for array_pos for <%s>",
               l->number, newvar->name );
            bwb_error( bwb_ebuf );
#else
            bwb_error( err_getmem );
#endif
            return bwb_zline( l );
            }

         for ( n = 0; n < newvar->dimensions; ++n )
            {
            newvar->array_pos[ n ] = dim_base;
            }

         /* calculate the array size */

	 newvar->array_units = (size_t) MAXINTSIZE;	/* avoid error in dim_unit() */
	 newvar->array_units = dim_unit( newvar, pp ) + 1;

#if INTENSIVE_DEBUG
         sprintf( bwb_ebuf, "in bwb_dim(): array memory requires <%ld> units",
            (long) newvar->array_units );
         bwb_debug( bwb_ebuf );
#endif

         /* assign array memory */

         switch( newvar->type )
            {
            case STRING:
#if INTENSIVE_DEBUG
               sprintf( bwb_ebuf, "in bwb_dim(): 1 STRING requires <%ld> bytes",
                  (long) sizeof( bstring ));
               bwb_debug( bwb_ebuf );
               sprintf( bwb_ebuf, "in bwb_dim(): STRING array memory requires <%ld> bytes",
        	  (long) ( newvar->array_units + 1 ) * sizeof( bstring ));
               bwb_debug( bwb_ebuf );
#endif
               /*------------------------------------------------------*/
               /* memnum, not memstr, was used here -- incorrect (JBV) */
               /* Revised to CALLOC pass-thru call by JBV              */
               /*------------------------------------------------------*/
               if ( ( newvar->memstr = (bstring *)
                  CALLOC( newvar->array_units, sizeof( bstring), "bwb_dim" )) == NULL )
               {
#if PROG_ERRORS
                  sprintf( bwb_ebuf, "in line %d: Failed to find memory for array <%s>",
                     l->number, newvar->name );
                  bwb_error( bwb_ebuf );
#else
                  bwb_error( err_getmem );
#endif
                  return bwb_zline( l );
                  }
               break;
            case NUMBER:
#if INTENSIVE_DEBUG
               sprintf( bwb_ebuf, "in bwb_dim(): 1 DOUBLE requires <%ld> bytes",
                  (long) sizeof( double ));
               bwb_debug( bwb_ebuf );
               sprintf( bwb_ebuf, "in bwb_dim(): DOUBLE array memory requires <%ld> bytes",
        	  (long) ( newvar->array_units + 1 ) * sizeof( double ));
               bwb_debug( bwb_ebuf );
#endif

               /* Revised to CALLOC pass-thru call by JBV */
               if ( ( np = (bnumber *)
                  CALLOC( newvar->array_units, sizeof( bnumber ), "bwb_dim" )) == NULL )
                  {
#if PROG_ERRORS
                  sprintf( bwb_ebuf, "in line %d: Failed to find memory for array <%s>",
                  l->number, newvar->name );
                  bwb_error( bwb_ebuf );
#else
                  bwb_error( err_getmem );
#endif
                  return bwb_zline( l );
                  }
	       newvar->memnum = np;
	       break;
	    default:
#if PROG_ERRORS
               sprintf( bwb_ebuf, "in line %d: New variable has unrecognized type.",
                  l->number );
               bwb_error( bwb_ebuf );
#else
               bwb_error( err_syntax );
#endif
               return bwb_zline( l );
            }

         }			/* end of conditional for new variable */

      /* now check for end of string */

      if ( l->buffer[ l->position ] == ')' )
         {
         ++( l->position );
         }
      adv_ws( l->buffer, &( l->position ));
      switch( l->buffer[ l->position ] )
         {
         case '\n':			/* end of line */
         case '\r':
         case ':':			/* end of line segment */
         case '\0':			/* end of string */
            loop = FALSE;
            break;
         case ',':
            ++( l->position );
            adv_ws( l->buffer, &( l->position ) );
            loop = TRUE;
            break;
         default:
#if PROG_ERRORS
            sprintf( bwb_ebuf, "in bwb_dim(): unexpected end of string, buf <%s>",
               &( l->buffer[ l->position ] ) );
            bwb_error( bwb_ebuf );
#else
            bwb_error( err_syntax );
#endif
            loop = FALSE;
            break;
         }

      }				/* end of loop through variables */

   /* return */

   return bwb_zline( l );

   }

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

        FUNCTION:       dim_unit()

        DESCRIPTION:    This function calculates the unit
        		position for an array.

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

#if ANSI_C
static size_t
dim_unit( struct bwb_variable *v, int *pp )
#else
static size_t
dim_unit( v, pp )
   struct bwb_variable *v;
   int *pp;
#endif
   {
   size_t r;
   size_t b;
   register int n;

   /* Calculate and return the address of the dimensioned array */

   b = 1;
   r = 0;
   for ( n = 0; n < v->dimensions; ++n )
      {
      r += b * ( pp[ n ] - dim_base );
      b *= v->array_sizes[ n ];
      }

#if INTENSIVE_DEBUG
   for ( n = 0; n < v->dimensions; ++n )
      {
      sprintf( bwb_ebuf,
         "in dim_unit(): variable <%s> pos <%d> val <%d>.",
         v->name, n, pp[ n ] );
      bwb_debug( bwb_ebuf );
      }
   sprintf( bwb_ebuf, "in dim_unit(): return unit: <%ld>", (long) r );
   bwb_debug( bwb_ebuf );
#endif

   if ( r > v->array_units )
      {
#if PROG_ERRORS
      sprintf( bwb_ebuf, "in dim_unit(): unit value <%ld> exceeds array units <%ld>",
         r, v->array_units );
      bwb_error( bwb_ebuf );
#else
      bwb_error( err_valoorange );
#endif
      return 0;
      }

   return r;

   }

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

        FUNCTION:       dim_getparams()

	DESCRIPTION:    This function reads a string in <buffer>
                        beginning at position <pos> and finds a
                        list of parameters surrounded by paren-
                        theses, returning in <n_params> the number
                        of parameters found, and returning in
                        <pp> an array of n_params integers giving
                        the sizes for each dimension of the array.

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

#if ANSI_C
int
dim_getparams( char *buffer, int *pos, int *n_params, int **pp )
#else
int
dim_getparams( buffer, pos, n_params, pp )
   char *buffer;
   int *pos;
   int *n_params;
   int **pp;
#endif
   {
   int loop;
   static int params[ MAX_DIMS ];
   int x_pos, s_pos;
   struct exp_ese *e;
   char tbuf[ MAXSTRINGSIZE + 1 ];
#if INTENSIVE_DEBUG
   register int n;
#endif

   /* set initial values */

   *n_params = 0;
#if OLDSTUFF
   paren_found = FALSE;
#endif

   /* advance and check for undimensioned variable */

   adv_ws( buffer, pos );
   if ( buffer[ *pos ] != '(' )
      {
      *n_params = 1;
      params[ 0 ] = dim_base;
      *pp = params;
      return TRUE;
      }
   else
      {
      ++(*pos);
      }

   /* Variable has DIMensions: Find each parameter */

   s_pos = 0;
   tbuf[ 0 ] = '\0';
   loop = TRUE;
   while( loop == TRUE )
      {
      switch( buffer[ *pos ] )
         {
         case ')':                      /* end of parameter list */
            x_pos = 0;
            if ( tbuf[ 0 ] == '\0' )
               {
               params[ *n_params ] = DEF_SUBSCRIPT;
               }
            else
               {
#if INTENSIVE_DEBUG
               sprintf( bwb_ebuf, "in dim_getparams(): call bwb_exp() for last element" );
               bwb_debug( bwb_ebuf );
#endif
               e = bwb_exp( tbuf, FALSE, &x_pos );
#if INTENSIVE_DEBUG
               sprintf( bwb_ebuf, "in dim_getparams(): return from bwb_exp() for last element" );
               bwb_debug( bwb_ebuf );
#endif
               params[ *n_params ] = (int) exp_getnval( e );
               }
            ++(*n_params);
            loop = FALSE;
            ++( *pos );
            break;

         case ',':                      /* end of a parameter */
            x_pos = 0;
            if ( tbuf[ 0 ] == '\0' )
               {
               params[ *n_params ] = DEF_SUBSCRIPT;
               }
            else
               {
#if INTENSIVE_DEBUG
               sprintf( bwb_ebuf, "in dim_getparams(): call bwb_exp() for element (not last)" );
               bwb_debug( bwb_ebuf );
#endif
               e = bwb_exp( tbuf, FALSE, &x_pos );
               params[ *n_params ] = (int) exp_getnval( e );
               }
            ++(*n_params);
            tbuf[ 0 ] = '\0';
            ++(*pos);
            s_pos = 0;
            break;

         case ' ':                      /* whitespace -- skip */
         case '\t':
            ++(*pos);
            break;

         default:
            tbuf[ s_pos ] = buffer[ *pos ];
            ++(*pos);
            ++s_pos;
            tbuf[ s_pos ] = '\0';
            break;
         }
      }