unit kern_sx;

{$mode ObjFPC}{$H+}
{$CALLING SysV_ABI_CDecl}

interface

uses
 kern_rwlock;

type
 p_sx=^t_sx;
 t_sx=packed record
  n:PChar;
  c:Pointer;
  m:QWORD;
 end;

procedure sx_init(p:p_sx;name:PChar);
function  sx_xlocked(p:p_sx):Boolean;
procedure sx_assert(p:p_sx);
procedure sx_slock(p:p_sx);
procedure sx_xlock(p:p_sx);
procedure sx_sunlock(p:p_sx);
procedure sx_xunlock(p:p_sx);
procedure sx_unlock(p:p_sx);

implementation

procedure sx_init(p:p_sx;name:PChar);
begin
 p^.n:=name;
 p^.c:=nil;
 p^.m:=0;
end;

function sx_xlocked(p:p_sx):Boolean;
begin
 Result:=(PDWORD(@p^.m)[0]=System.GetCurrentThreadId) and
         (PDWORD(@p^.m)[1]=2);
end;

procedure sx_assert(p:p_sx);
begin
 Assert(sx_xlocked(p),'sx_assert');
end;

procedure sx_slock(p:p_sx);
begin
 rw_rlock(p^.c);
 PDWORD(@p^.m)[0]:=0;
 PDWORD(@p^.m)[1]:=1;
end;

procedure sx_xlock(p:p_sx);
begin
 rw_wlock(p^.c);
 PDWORD(@p^.m)[0]:=System.GetCurrentThreadId;
 PDWORD(@p^.m)[1]:=2;
end;

procedure sx_sunlock(p:p_sx);
begin
 rw_runlock(p^.c);
end;

procedure sx_xunlock(p:p_sx);
begin
 rw_wunlock(p^.c);
end;

procedure sx_unlock(p:p_sx);
begin
 case PDWORD(@p^.m)[1] of
  1:rw_runlock(p^.c);
  2:rw_wunlock(p^.c);
 end;
end;

end.