1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT RUN-TIME COMPONENTS                         --
4--                                                                          --
5--              S Y S T E M . F I L E _ C O N T R O L _ B L O C K           --
6--                                                                          --
7--                                 S p e c                                  --
8--                                                                          --
9--            Copyright (C) 1992-2012, Free Software Foundation, Inc.       --
10--                                                                          --
11-- GNAT is free software;  you can  redistribute it  and/or modify it under --
12-- terms of the  GNU General Public License as published  by the Free Soft- --
13-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
14-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
15-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
16-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
17--                                                                          --
18-- As a special exception under Section 7 of GPL version 3, you are granted --
19-- additional permissions described in the GCC Runtime Library Exception,   --
20-- version 3.1, as published by the Free Software Foundation.               --
21--                                                                          --
22-- You should have received a copy of the GNU General Public License and    --
23-- a copy of the GCC Runtime Library Exception along with this program;     --
24-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
25-- <http://www.gnu.org/licenses/>.                                          --
26--                                                                          --
27-- GNAT was originally developed  by the GNAT team at  New York University. --
28-- Extensive contributions were provided by Ada Core Technologies Inc.      --
29--                                                                          --
30------------------------------------------------------------------------------
31
32--  This package contains the declaration of the basic file control block
33--  shared between Text_IO, Sequential_IO, Direct_IO and Streams.Stream_IO.
34--  The actual control blocks are derived from this block by extension. The
35--  control block is itself derived from Ada.Streams.Root_Stream_Type which
36--  facilitates implementation of Stream_IO.Stream and Text_Streams.Stream.
37
38with Ada.Streams;
39with Interfaces.C_Streams;
40with System.CRTL;
41
42package System.File_Control_Block is
43   pragma Preelaborate;
44
45   ----------------------------
46   -- Ada File Control Block --
47   ----------------------------
48
49   --  The Ada file control block is an abstract extension of the root
50   --  stream type. This allows a file to be treated directly as a stream
51   --  for the purposes of Stream_IO, or stream operations on a text file.
52   --  The individual I/O packages extend this type with package specific
53   --  fields to create the concrete types to which the routines in this
54   --  package can be applied.
55
56   --  The type File_Type in the individual packages is an access to the
57   --  extended file control block. The value is null if the file is not
58   --  open, and a pointer to the control block if the file is open.
59
60   type Pstring is access all String;
61   --  Used to hold name and form strings
62
63   type File_Mode is (In_File, Inout_File, Out_File, Append_File);
64   subtype Read_File_Mode is File_Mode range In_File .. Inout_File;
65   --  File mode (union of file modes permitted by individual packages,
66   --  the types File_Mode in the individual packages are declared to
67   --  allow easy conversion to and from this general type.
68
69   type Shared_Status_Type is (Yes, No, None);
70   --  This type is used to define the sharing status of a file. The default
71   --  setting of None is used if no "shared=xxx" appears in the form string
72   --  when a file is created or opened. For a file with Shared_Status set to
73   --  None, Use_Error will be raised if any other file is opened or created
74   --  with the same full name. Yes/No are set in response to the presence
75   --  of "shared=yes" or "shared=no" in the form string. In either case it
76   --  is permissible to have multiple files opened with the same full name.
77   --  All files opened simultaneously with "shared=yes" will share the same
78   --  stream with the semantics specified in the RM for file sharing. All
79   --  files opened with "shared=no" will have their own stream.
80
81   type AFCB is tagged;
82   type AFCB_Ptr is access all AFCB'Class;
83
84   type AFCB is abstract new Ada.Streams.Root_Stream_Type with record
85
86      Stream : Interfaces.C_Streams.FILEs;
87      --  The file descriptor
88
89      Name : Pstring;
90      --  A pointer to the file name. The file name is null for temporary
91      --  files, and also for standard files (stdin, stdout, stderr). The
92      --  name is always null-terminated if it is non-null.
93
94      Encoding : System.CRTL.Filename_Encoding;
95      --  Encoding used to specified the filename
96
97      Form : Pstring;
98      --  A pointer to the form string. This is the string used in the
99      --  fopen call, and must be supplied by the caller (there are no
100      --  defaults at this level). The string is always null-terminated.
101
102      Mode : File_Mode;
103      --  The file mode. No checks are made that the mode is consistent
104      --  with the form used to fopen the file.
105
106      Is_Regular_File : Boolean;
107      --  A flag indicating if the file is a regular file
108
109      Is_Temporary_File : Boolean;
110      --  A flag set only for temporary files (i.e. files created using the
111      --  Create function with a null name parameter, using tmpfile). This
112      --  is currently not used since temporary files are deleted by the
113      --  operating system, but it is set properly in case some systems
114      --  need this information in the future.
115
116      Is_System_File : Boolean;
117      --  A flag set only for system files (stdin, stdout, stderr)
118
119      Is_Text_File : Boolean;
120      --  A flag set if the file was opened in text mode
121
122      Shared_Status : Shared_Status_Type;
123      --  Indicates sharing status of file, see description of type above
124
125      Access_Method : Character;
126      --  Set to 'Q', 'S', 'T', 'D' for Sequential_IO, Stream_IO, Text_IO,
127      --  Direct_IO file (used to validate file sharing request).
128
129      Next : AFCB_Ptr;
130      Prev : AFCB_Ptr;
131      --  All open files are kept on a doubly linked chain, with these
132      --  pointers used to maintain the next and previous pointers.
133
134   end record;
135
136   ----------------------------------
137   -- Primitive Operations of AFCB --
138   ----------------------------------
139
140   --  Note that we inherit the abstract operations Read and Write from
141   --  the base type. These must be overridden by the individual file
142   --  access methods to provide Stream Read/Write access.
143
144   function AFCB_Allocate (Control_Block : AFCB) return AFCB_Ptr is abstract;
145   --  Given a control block, allocate space for a control block of the same
146   --  type on the heap, and return the pointer to this allocated block. Note
147   --  that the argument Control_Block is not used other than as the argument
148   --  that controls which version of AFCB_Allocate is called.
149
150   procedure AFCB_Close (File : not null access AFCB) is abstract;
151   --  Performs any specialized close actions on a file before the file is
152   --  actually closed at the system level. This is called by Close, and
153   --  the reason we need the primitive operation is for the automatic
154   --  close operations done as part of finalization.
155
156   procedure AFCB_Free (File : not null access AFCB) is abstract;
157   --  Frees the AFCB referenced by the given parameter. It is not necessary
158   --  to free the strings referenced by the Form and Name fields, but if the
159   --  extension has any other heap objects, they must be freed as well. This
160   --  procedure must be overridden by each individual file package.
161
162end System.File_Control_Block;
163