A.8.4 The Generic Package Direct_IO
Static Semantics
1
The generic library
package Direct_IO has the following declaration:
2
with Ada.IO_Exceptions;
generic
type Element_Type
is private;
package Ada.Direct_IO
is
3
type File_Type
is limited private;
4
type File_Mode
is (In_File, Inout_File, Out_File);
type Count
is range 0 ..
implementation-defined;
subtype Positive_Count
is Count
range 1 .. Count'Last;
5
-- File management
6
procedure Create(File :
in out File_Type;
Mode :
in File_Mode := Inout_File;
Name :
in String := "";
Form :
in String := "");
7
procedure Open (File :
in out File_Type;
Mode :
in File_Mode;
Name :
in String;
Form :
in String := "");
8
procedure Close (File :
in out File_Type);
procedure Delete(File :
in out File_Type);
procedure Reset (File :
in out File_Type; Mode :
in File_Mode);
procedure Reset (File :
in out File_Type);
9
function Mode (File :
in File_Type)
return File_Mode;
function Name (File :
in File_Type)
return String;
function Form (File :
in File_Type)
return String;
10
function Is_Open(File :
in File_Type)
return Boolean;
11
-- Input and output operations
12
procedure Read (File :
in File_Type; Item :
out Element_Type;
From :
in Positive_Count);
procedure Read (File :
in File_Type; Item :
out Element_Type);
13
procedure Write(File :
in File_Type; Item :
in Element_Type;
To :
in Positive_Count);
procedure Write(File :
in File_Type; Item :
in Element_Type);
14
procedure Set_Index(File :
in File_Type; To :
in Positive_Count);
15
function Index(File :
in File_Type)
return Positive_Count;
function Size (File :
in File_Type)
return Count;
16
function End_Of_File(File :
in File_Type)
return Boolean;
17
-- Exceptions
18
Status_Error :
exception renames IO_Exceptions.Status_Error;
Mode_Error :
exception renames IO_Exceptions.Mode_Error;
Name_Error :
exception renames IO_Exceptions.Name_Error;
Use_Error :
exception renames IO_Exceptions.Use_Error;
Device_Error :
exception renames IO_Exceptions.Device_Error;
End_Error :
exception renames IO_Exceptions.End_Error;
Data_Error :
exception renames IO_Exceptions.Data_Error;
19
private
... -- not specified by the language
end Ada.Direct_IO;
19.a
Reason: The Element_Type formal of Direct_IO
does not have an unknown_discriminant_part
(unlike Sequential_IO) so that the implementation can make use of the
ability to declare uninitialized variables of the type.
20/2
{
AI95-00360-01}
The type File_Type needs finalization (see 7.6)
in every instantiation of Direct_IO.20.a.1/2
This paragraph
was deleted.Implementation Note:
{
8652/0097}
{
AI95-00115-01}
{
AI95-00344-01}
File_Type
cannot be implemented as a (directly) controlled type, as Ada.Direct_IO
can be instantiated at any nesting depth. File_Type could have a component
of a controlled type, as long as that type is declared in some other
(non-generic) package.
Incompatibilities With Ada 95
20.a/2
{
AI95-00360-01}
{incompatibilities with Ada 95} Amendment
Correction: File_Type in an instance of Direct_IO is defined to need
finalization. If the restriction No_Nested_Finalization (see D.7)
applies to the partition, and File_Type does not have a controlled part,
it will not be allowed in local objects in Ada 2005 whereas it would
be allowed in original Ada 95. Such code is not portable, as another
Ada compiler may have a controlled part in File_Type, and thus would
be illegal.
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