bwb_dio.c

这是一个简易的basic语言解释器, 可供我们学习和改进.

         }

      length = (int) exp_getnval( e );

#if INTENSIVE_DEBUG
      sprintf( bwb_ebuf, "in bwb_field(): device <%d> length <%d> buf <%s>",
         dev_number, length, &( l->buffer[ l->position ] ) );
      bwb_debug( bwb_ebuf );
#endif

      /* read the AS */

      adv_element( l->buffer, &( l->position ), atbuf );	/* get element */
      bwb_strtoupper( atbuf );

#if INTENSIVE_DEBUG
      sprintf( bwb_ebuf, "in bwb_field(): AS element <%s>", atbuf );
      bwb_debug( bwb_ebuf );
#endif

      if ( strncmp( atbuf, "AS", 2 ) != 0 )
         {
#if PROG_ERRORS
         bwb_error( "in bwb_field(): AS statement not found" );
#else
         bwb_error( err_syntax );
#endif
         return bwb_zline( l );
         }

      /* read the string variable name */

      adv_element( l->buffer, &( l->position ), atbuf );	/* get element */
      v = var_find( atbuf );

      if ( v->type != STRING )
         {
#if PROG_ERRORS
         bwb_error( "in bwb_field(): string variable name not found" );
#else
         bwb_error( err_syntax );
#endif
         return bwb_zline( l );
         }

#if INTENSIVE_DEBUG
      sprintf( bwb_ebuf, "in bwb_field(): device <%d> var <%s> length <%d>",
         dev_number, v->name, length );
      bwb_debug( bwb_ebuf );
#endif

      /* check for overflow of record length */

      if ( ( current_pos + length ) > dev_table[ dev_number ].reclen )
         {
#if PROG_ERRORS
         bwb_error( "in bwb_field(): record length exceeded" );
#else
         bwb_error( err_overflow );
#endif
         return bwb_zline( l );
         }

      /* set buffer */

      b = var_findsval( v, v->array_pos );

#if DONTDOTHIS
      if ( b->sbuffer != NULL )
	 {
         /* Revised to FREE pass-thru call by JBV */
	 FREE( b->sbuffer, "bwb_field" );
	 b->sbuffer = NULL; /* JBV */
	 }
#endif

      b->sbuffer = dev_table[ dev_number ].buffer + current_pos;
      b->length = (unsigned char) length;
      b->rab = TRUE;

      current_pos += length;

#if INTENSIVE_DEBUG
      sprintf( bwb_ebuf, "in bwb_field(): buffer <%lXh> var <%s> buffer <%lXh>",
         (long) dev_table[ dev_number ].buffer, v->name, (long) b->sbuffer );
      bwb_debug( bwb_ebuf );
#endif

      /* eat up any remaining whitespace */

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

      }

   while ( l->buffer[ l->position ] == ',' );

   /* return */

   return bwb_zline( l );

   }

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

        FUNCTION:       bwb_lset()

        DESCRIPTION:	This C function implements the BASIC
			LSET command.

	SYNTAX:		LSET string-variable$ = expression

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

#if ANSI_C
struct bwb_line *
bwb_lset( struct bwb_line *l )
#else
struct bwb_line *
bwb_lset( l )
   struct bwb_line *l;
#endif
   {
   return dio_lrset( l, FALSE );
   }

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

        FUNCTION:       bwb_rset()

        DESCRIPTION:	This C function implements the BASIC
			RSET command.

	SYNTAX:		RSET string-variable$ = expression

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

#if ANSI_C
struct bwb_line *
bwb_rset( struct bwb_line *l )
#else
struct bwb_line *
bwb_rset( l )
   struct bwb_line *l;
#endif
   {
   return dio_lrset( l, TRUE );
   }

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

        FUNCTION:       dio_lrset()

        DESCRIPTION:	This C function implements the BASIC
			RSET and LSET commands.

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

#if ANSI_C
static struct bwb_line *
dio_lrset( struct bwb_line *l, int rset )
#else
static struct bwb_line *
dio_lrset( l, rset )
   struct bwb_line *l;
   int rset;
#endif
   {
   char varname[ MAXVARNAMESIZE + 1 ];
   bstring *d, *s;
   int *pp;
   int n_params;
   int p;
   register int n, i;
   int startpos;
   struct exp_ese *e;

   /* find the variable name */

   bwb_getvarname( l->buffer, varname, &( l->position ));

   v = var_find( varname );

   if ( v == NULL )
      {
#if PROG_ERRORS
      sprintf( bwb_ebuf, "in dio_lrset(): failed to find variable" );
      bwb_error( bwb_ebuf );
#else
      bwb_error( err_syntax );
#endif
      }

   if ( v->type != STRING )
      {
#if PROG_ERRORS
      sprintf( bwb_ebuf, "in dio_lrset(): assignment must be to string variable" );
      bwb_error( bwb_ebuf );
#else
      bwb_error( err_syntax );
#endif
      }

   /* read subscripts */

   pos = 0;
   if ( ( v->dimensions == 1 ) && ( v->array_sizes[ 0 ] == 1 ))
      {
#if INTENSIVE_DEBUG
      sprintf( bwb_ebuf, "in dio_lrset(): variable <%s> has 1 dimension",
         v->name );
      bwb_debug( bwb_ebuf );
#endif
      n_params = 1;
      pp = &p;
      pp[ 0 ] = dim_base;
      }
   else
      {
#if INTENSIVE_DEBUG
      sprintf( bwb_ebuf, "in dio_lrset(): variable <%s> has > 1 dimensions",
         v->name );
      bwb_debug( bwb_ebuf );
#endif
      dim_getparams( l->buffer, &( l->position ), &n_params, &pp );
      }

   CURTASK exps[ CURTASK expsc ].pos_adv = pos;
   for ( n = 0; n < v->dimensions; ++n )
      {
      v->array_pos[ n ] = pp[ n ];
      }

   /* get bstring pointer */

   d = var_findsval( v, pp );

   /* find equals sign */

   adv_ws( l->buffer, &( l->position ));
   if ( l->buffer[ l->position ] != '=' )
      {
#if PROG_ERRORS
      sprintf( bwb_ebuf, "in dio_lrset(): failed to find equal sign" );
      bwb_error( bwb_ebuf );
#else
      bwb_error( err_syntax );
#endif
      }
   ++( l->position );
   adv_ws( l->buffer, &( l->position ));

   /* read remainder of line to get value */

   e = bwb_exp( l->buffer, FALSE, &( l->position ) );
   s = exp_getsval( e );

   /* set starting position */

   startpos = 0;
   if ( rset == TRUE )
      {
      if ( s->length < d->length )
         {
         startpos = d->length - s->length;
         }
      }

#if INTENSIVE_DEBUG
   sprintf( bwb_ebuf, "in dio_lrset(): startpos <%d> buffer <%lX>",
      startpos, (long) d->sbuffer );
   bwb_debug( bwb_ebuf );
#endif

   /* write characters to new position */

   i = 0;
   for ( n = startpos; ( i < (int) s->length ) && ( n < (int) d->length ); ++n )
      {
      d->sbuffer[ n ] = s->sbuffer[ i ];
      ++i;
      }

   /* return */

   return bwb_zline( l );

   }

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

        FUNCTION:       bwb_get()

        DESCRIPTION:	This C function implements the BASIC
			GET command.

	SYNTAX:		GET [#] device-number [, record-number]

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

#if ANSI_C
struct bwb_line *
bwb_get( struct bwb_line *l )
#else
struct bwb_line *
bwb_get( l )
   struct bwb_line *l;
#endif
   {
   int dev_number;
   int rec_number;
   register int i;
   struct exp_ese *e;
   char atbuf[ MAXSTRINGSIZE + 1 ];
   long offset; /* JBV */

   /* first read device number */

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

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

   pos = 0;
   e = bwb_exp( atbuf, FALSE, &pos );

   if ( e->type != NUMBER )
      {
#if PROG_ERRORS
      bwb_error( "in bwb_get(): Number was expected for device number" );
#else
      bwb_error( err_syntax );
#endif
      return bwb_zline( l );
      }

   dev_number = (int) exp_getnval( e );

#if INTENSIVE_DEBUG
   sprintf( bwb_ebuf, "in bwb_get(): device <%d>", dev_number );
   bwb_debug( bwb_ebuf );
#endif

   /* be sure that the requested device is open */

   if ( ( dev_table[ dev_number ].mode == DEVMODE_CLOSED ) ||
      ( dev_table[ req_devnumber ].mode == DEVMODE_AVAILABLE ) )
      {
#if PROG_ERRORS
      bwb_error( "in bwb_get(): Requested device number is not in use." );
#else
      bwb_error( err_devnum );
#endif
      return bwb_zline( l );
      }

   /* see if there is a comma (and record number) */

   adv_ws( l->buffer, &( l->position ) );
   if ( l->buffer[ l->position ] == ',' )	/* yes, there is a comma */
      {
      ++( l->position );

      /* get the record number element */

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

      pos = 0;
      e = bwb_exp( atbuf, FALSE, &pos );
      rec_number = (int) exp_getnval( e );

      }

   else				/* no record number given */
      {
      rec_number = dev_table[ dev_number ].next_record;
      }

#if INTENSIVE_DEBUG
   sprintf( bwb_ebuf, "in bwb_get(): record number <%d>", rec_number );
   bwb_debug( bwb_ebuf );
#endif

   /* wind the c file up to the proper point */

   /* Added by JBV */
   offset = (long) (( rec_number - 1 ) * dev_table[ dev_number ].reclen);

   if ( fseek( dev_table[ dev_number ].cfp, offset, SEEK_SET ) != 0 )
      {
#if PROG_ERRORS
      sprintf( bwb_ebuf, "in bwb_get(): fseek() failed, rec number <%d> offset <%ld>",
        rec_number, (long) (( rec_number - 1 ) * dev_table[ dev_number ].reclen ) );
      bwb_error( bwb_ebuf );
#else
      bwb_error( err_dev );
#endif
      return bwb_zline( l );
      }

   /* read the requested bytes into the buffer */

   dev_table[ dev_number ].loc = offset; /* Slight bug fix (JBV) */
   for ( i = 0; i < dev_table[ dev_number ].reclen; ++i )
      {
      dev_table[ dev_number ].buffer[ i ] =
         (char) fgetc( dev_table[ dev_number ].cfp );
      ++( dev_table[ dev_number ].loc );
      }

   /* increment (or reset) the current record */

   dev_table[ dev_number ].next_record = rec_number + 1;

   return bwb_zline( l );

   }

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

        FUNCTION:       bwb_put()

        DESCRIPTION:	This C function implements the BASIC
			PUT command.

	SYNTAX:		PUT [#] device-number [, record-number]

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

#if ANSI_C
struct bwb_line *
bwb_put( struct bwb_line *l )
#else
struct bwb_line *
bwb_put( l )
   struct bwb_line *l;
#endif
   {
   int dev_number;
   int rec_number;
   register int i;
   struct exp_ese *e;
   char atbuf[ MAXSTRINGSIZE + 1 ];
   long offset; /* JBV */

   /* first read device number */

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

   adv_element( l->buffer, &( l->position ), atbuf );
/*   dev_number = atoi( atbuf ); */  /* Not quite right (JBV) */

   /* Added by JBV */
   pos = 0;
   e = bwb_exp( atbuf, FALSE, &pos );

   if ( e->type != NUMBER )
      {
#if PROG_ERRORS
      bwb_error( "in bwb_put(): Number was expected for device number" );
#else
      bwb_error( err_syntax );
#endif
      return bwb_zline( l );
      }

   dev_number = (int) exp_getnval( e );

#if INTENSIVE_DEBUG
   sprintf( bwb_ebuf, "in bwb_put(): device <%d>", dev_number );
   bwb_debug( bwb_ebuf );
#endif

   /* be sure that the requested device is open */

   if ( ( dev_table[ dev_number ].mode == DEVMODE_CLOSED ) ||
      ( dev_table[ req_devnumber ].mode == DEVMODE_AVAILABLE ) )
      {
#if PROG_ERRORS
      bwb_error( "in bwb_put(): Requested device number is not in use." );
#else
      bwb_error( err_devnum );
#endif
      return bwb_zline( l );
      }

   /* see if there is a comma (and record number) */

   adv_ws( l->buffer, &( l->position ) );
   if ( l->buffer[ l->position ] == ',' )	/* yes, there is a comma */
      {
      ++( l->position );

      /* get the record number element */

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

#if INTENSIVE_DEBUG
      sprintf( bwb_ebuf, "in bwb_put(): rec no buffer <%s>", atbuf );
      bwb_debug( bwb_ebuf );
#endif

      pos = 0;
      e = bwb_exp( atbuf, FALSE, &pos );

#if INTENSIVE_DEBUG
      sprintf( bwb_ebuf, "in bwb_put(): return type <%c>", e->type );
      bwb_debug( bwb_ebuf );
#endif

      rec_number = (int) exp_getnval( e );

      }

   else				/* no record number given */
      {
      rec_number = dev_table[ dev_number ].next_record;
      }

#if INTENSIVE_DEBUG
   sprintf( bwb_ebuf, "in bwb_put(): record number <%d>", rec_number );
   bwb_debug( bwb_ebuf );
#endif

   /* wind the c file up to the proper point */

   /* Added by JBV */
   offset = (long) (( rec_number - 1 ) * dev_table[ dev_number ].reclen);

   if ( fseek( dev_table[ dev_number ].cfp, offset, SEEK_SET ) != 0 )
      {
#if PROG_ERRORS
      sprintf( bwb_ebuf, "in bwb_get(): fseek() failed, rec number <%d> offset <%ld>",
        rec_number, (long) (( rec_number - 1 ) * dev_table[ dev_number ].reclen ) );
      bwb_error( bwb_ebuf );
#else
      bwb_error( err_dev );
#endif
      return bwb_zline( l );
      }

#if INTENSIVE_DEBUG
   sprintf( bwb_ebuf, "in bwb_put(): ready to write to file, buffer <%lXh>",
      (long) dev_table[ dev_number ].buffer );
   bwb_debug( bwb_ebuf );
   prn_xprintf( stderr, "Buffer: <" );
#endif

   /* write the requested bytes to the file */

   dev_table[ dev_number ].loc = offset; /* Slight bug fix (JBV) */
   for ( i = 0; i < dev_table[ dev_number ].reclen; ++i )
      {
      fputc( dev_table[ dev_number ].buffer[ i ],
         dev_table[ dev_number ].cfp );
#if INTENSIVE_DEBUG
      xputc( stderr, dev_table[ dev_number ].buffer[ i ] );
#endif
      ++( dev_table[ dev_number ].loc );
      }

#if INTENSIVE_DEBUG
   prn_xprintf( stderr, ">\n" );
   sprintf( bwb_ebuf, "in bwb_put(): write to file complete" );
   bwb_debug( bwb_ebuf );
#endif

   /* flush the buffer */

   dio_flush( dev_number );

   /* increment (or reset) the current record */

   dev_table[ dev_number ].next_record = rec_number + 1;

   return bwb_zline( l );

   }

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

        FUNCTION:       dio_flush()

        DESCRIPTION:    This C function flushes the random-access
			buffer associated with file dev_number.

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

#if ANSI_C
static int
dio_flush( int dev_number )
#else
static int
dio_flush( dev_number )
   int dev_number;
#endif
   {
   register int n;

   if ( dev_table[ dev_number ].mode != DEVMODE_RANDOM )
      {
#if PROG_ERRORS
      sprintf( bwb_ebuf, "in dio_flush(): only random-access buffers can be flushed" );
      bwb_error( bwb_ebuf );
#else
      bwb_error( err_dev );
#endif
      }

   /* fill buffer with blanks (or 'X' for test) */

   for ( n = 0; n < dev_table[ req_devnumber ].reclen; ++n )
      {
      dev_table[ req_devnumber ].buffer[ n ] = RANDOM_FILLCHAR;
      }

   return TRUE;

   }

#endif				/* COMMON_CMDS */