program mget;
{$NOMAIN}
{$NOWALKBACK}

{
File		: DE:[22,310]MGET.PAS
Author		: Peter Stadick
Date		: Aug 29,89
Edit History	:

       Last Edit: 30-AUG-1989 15:17:34 

Description:

	This routine retrives an array element from the shared region.

}

%include lb:[22,320]general3.typ;
%include de:[22,320]marray.typ;

%include de:[22,320]marray.ext;
%include de:[22,320]bytmov.ext;
%include de:[22,320]mappa.ext;
%include de:[22,320]elawpa.ext;
%include de:[22,320]crawpa.ext;

procedure mget;

const
  debug = false;

type
  apr_block_point = ^apr_use_type;

var
  window_number		: integer;
  offset_to_element	: integer;
  apr_address		: address;
  element_address	: address;
  ele_add_add		: address;
  wdb			: wdb_type;
  remap			: boolean;
  apr_use_block		: apr_block_point;

begin
  remap := false;
  error_code := 1;
  if (element_number < 1) or (element_number > m_array.max_elements) then
    error_code := -1003;

  if error_code > 0 then
  begin
    { Check to see if the correct region is mapped }
    apr_use_block := loophole(apr_block_point,m_array.apr_use_address);
    if not ((apr_use_block^[m_array.apr_to_use][1] = m_array.rdb[3]) and
      (apr_use_block^[m_array.apr_to_use][2] = m_array.rdb[4])) then 
    begin
      { correct region is not mapped so we eliminate the old address window
	and create a new one for this region }
      if debug then
        writeln('REMAP-GET');
      remap := true;
      wdb[1] := apr_use_block^[m_array.apr_to_use][3];
      elawpa(wdb);
      crawpa(m_array.wdb);
      if $dsw < 0 then
        error_code := $dsw - 400;

      { Update apr use block }
      apr_use_block^[m_array.apr_to_use][1] := m_array.rdb[3];
      apr_use_block^[m_array.apr_to_use][2] := m_array.rdb[4];
      apr_use_block^[m_array.apr_to_use][3] := m_array.wdb[1];
    end;
  end;

  if error_code > 0 then
  begin
    element_number := element_number - 1;
    window_number := element_number div m_array.elements_per_window;

    { Check to see if we have the write window mapped }
    if remap or not (window_number = m_array.current_window) then
    begin
      { Opps, don't have the correct mapped so lets remap it }
      m_array.wdb[5] := window_number * m_array.blocks_per_window;
      mappa(m_array.wdb);
      if $dsw < 0 then
      begin
        error_code := $dsw - 600;
        m_array.current_window := -1;
      end
      else
        m_array.current_window := window_number;
    end;

    { Now lets find the element in the window }
    if error_code > 0 then
    begin
      { Compute offset in number of bytes into window the element in question 
        is }
      offset_to_element := 
        (element_number mod m_array.elements_per_window) * m_array.element_size;

      { Now we need to copy data to buffer located at buffer_address }
      apr_address := m_array.apr_to_use * 20000B;
      element_address := loophole(address,apr_address) + offset_to_element;
      if m_array.use_pointer then
      begin
        { Change pointer address to point at data in region }
        ele_add_add := loophole(address,ref(element_address));
        bytmov(ele_add_add,m_array.buffer_address,2);
      end
      else
        bytmov(element_address,m_array.buffer_address,m_array.element_size);
    end;
  end;
end;