/**
   BLOCK -- BLOCK file access
   
    Copyright (C) Tektronix, Inc. 1998 - 2001. All rights reserved.
  
    @see     GNU LGPL
    @author  Tektronix CTE              @(#) %derived_by: guidod %
    @version %version: 5.5 %
      (%date_modified: Mon Mar 12 10:31:59 2001 %)
  
    @description
       Historically Forth was implemented on small computers as an
       operating system in its own right. Mass storage was not
       organized in files but as a sequence of 1 KB blocks. A block
       was addressed with a block number. This way a diskette drive
       provided a few hundred blocks and if you had a fixed disk
       you simply had thousands of those blocks.
  
       Both program text and arbitrary data can be stored in blocks.
       In order to hold source text the 1K block is treated as
       having 16 lines with 64 charactes each. This is often 
       referred to as a 'screen'.
  
       When loading (i.e. interpreting) a block with source text it
       is simply taking to be a single line of 1024 characters. The
       only exception to this is the word => \ (begin comment to
       end of line) which skips text up to the end of a 64-char line
       in a block.
 */
/*@{*/
#if defined(__version_control__) && defined(__GNUC__)
static char* id __attribute__((unused)) = 
"@(#) $Id: %full_filespec: block-ext.c~5.5:csrc:bln_12xx!1 % $";
#endif

#define _P4_SOURCE 1

#include <pfe/pfe-base.h>
#include <pfe/def-xtra.h>

#include <string.h>
#include <limits.h>

#include <pfe/block-sub.h>
#include <pfe/_missing.h>

/** BLOCK ( u -- addr )
   load the specified block into a block buffer
   and return the address of that block buffer
   - see also => BUFFER
 */
FCode (p4_block)
{
    *SP = (p4cell) p4_block (BLOCK_FILE, *SP);
}


/** BUFFER ( u -- addr )
   get the block buffer address for the specified 
   block - if it had not been loaded already it
   is <b>not</b> filled with data from the disk
   unlike => BLOCK does.
 */
FCode (p4_buffer)
{
    int n;

    *SP = (p4cell) p4_buffer (BLOCK_FILE, *SP, &n);
}


/** SAVE-BUFFERS ( -- )
   write all modified buffer to
   the disk, see => UPDATE and
   => FLUSH
 */
FCode (p4_save_buffers)
{
    p4_save_buffers (BLOCK_FILE);
}


/** EMPTY-BUFFERS ( -- )
   unassign all block buffers, does not even => UPDATE
 */
FCode (p4_empty_buffers)
{
    p4_empty_buffers (BLOCK_FILE);
}


/** FLUSH ( -- )
   call => SAVE-BUFFERS and then unassign all
   block buffers with => EMPTY-BUFFERS
 */
FCode (p4_flush)
{
    FX (p4_save_buffers);
    FX (p4_empty_buffers);
}


/** LIST ( u -- )
   display the block
 */
FCode (p4_list)
{
    p4_list (BLOCK_FILE, SCR = *SP++);
}


/** LOAD ( u -- )
   => INTERPRET the specified => BLOCK
 */
FCode (p4_load)
{
    p4_load (BLOCK_FILE, *SP++);
}


/** THRU ( u1 u2 -- )
   => LOAD a number of block in sequence.
 */
FCode (p4_thru)
{
    int hi = *SP++;
    int lo = *SP++;

    p4_thru (BLOCK_FILE, lo, hi);
}


/** UPDATE ( -- )
   mark the current block buffer as modified,
   see => FLUSH
 */
FCode (p4_update)
{
    p4_update (BLOCK_FILE);
}


/** BLK ( -- val )
   the direct use of => BLK and => SCR is depracated
   (very traditional variables for I/O system)
 */

/** SCR ( -- val )
   the direct use of => BLK and => SCR is depracated
   (very traditional variables for I/O system)
 */

P4_LISTWORDS (block) =
{
    P4_INTO ("[ANS]", 0), /* block */
    P4_DVaR ("BLK",		input.blk),
    P4_FXco ("BLOCK",		p4_block),
    P4_FXco ("BUFFER",		p4_buffer),
    P4_FXco ("FLUSH",		p4_flush),
    P4_FXco ("LOAD",		p4_load),
    P4_FXco ("SAVE-BUFFERS",	p4_save_buffers),
    P4_FXco ("UPDATE",		p4_update),
    /* FXco ("EVALUATE",	...) */

    P4_INTO ("[ANS]", 0), /* block ext */
    P4_FXco ("EMPTY-BUFFERS",	p4_empty_buffers),
    P4_FXco ("LIST",		p4_list),
    P4_DVaR ("SCR",		scr),
    P4_FXco ("THRU",		p4_thru),
    /* FXco ("REFILL",		...) */
    /* FXco ("\\",		...) */

    P4_INTO ("ENVIRONMENT", 0 ),
    /* enviroment hints (testing for -EXT will mark this wordset as present) */
    P4_OCON ("BLOCK-EXT",	1994 ),
}
;
P4_COUNTWORDS (block, "Block Words + extensions");

/*@}*/