1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME COMPONENTS --
5 -- S Y S T E M . F I L E _ C O N T R O L _ B L O C K --
9 -- Copyright (C) 1992-2017, Free Software Foundation, Inc. --
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. --
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. --
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/>. --
27 -- GNAT was originally developed by the GNAT team at New York University. --
28 -- Extensive contributions were provided by Ada Core Technologies Inc. --
30 ------------------------------------------------------------------------------
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.
39 with Interfaces
.C_Streams
;
42 package System
.File_Control_Block
is
45 ----------------------------
46 -- Ada File Control Block --
47 ----------------------------
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.
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.
60 type Pstring
is access all String;
61 -- Used to hold name and form strings
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.
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.
82 type AFCB_Ptr
is access all AFCB
'Class;
84 type AFCB
is abstract new Ada
.Streams
.Root_Stream_Type
with record
86 Stream
: Interfaces
.C_Streams
.FILEs
;
87 -- The file descriptor
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 NUL-terminated if it is non-null.
94 Encoding
: System
.CRTL
.Filename_Encoding
;
95 -- Encoding used to specified the filename
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.
103 -- The file mode. No checks are made that the mode is consistent
104 -- with the form used to fopen the file.
106 Is_Regular_File
: Boolean;
107 -- A flag indicating if the file is a regular file
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).
113 Is_System_File
: Boolean;
114 -- A flag set only for system files (stdin, stdout, stderr)
116 Text_Encoding
: Interfaces
.C_Streams
.Content_Encoding
;
117 -- A flag set to describe file content encoding
119 Shared_Status
: Shared_Status_Type
;
120 -- Indicates sharing status of file, see description of type above
122 Access_Method
: Character;
123 -- Set to 'Q', 'S', 'T', 'D' for Sequential_IO, Stream_IO, Text_IO,
124 -- Direct_IO file (used to validate file sharing request).
128 -- All open files are kept on a doubly linked chain, with these
129 -- pointers used to maintain the next and previous pointers.
133 ----------------------------------
134 -- Primitive Operations of AFCB --
135 ----------------------------------
137 -- Note that we inherit the abstract operations Read and Write from
138 -- the base type. These must be overridden by the individual file
139 -- access methods to provide Stream Read/Write access.
141 function AFCB_Allocate
(Control_Block
: AFCB
) return AFCB_Ptr
is abstract;
142 -- Given a control block, allocate space for a control block of the same
143 -- type on the heap, and return the pointer to this allocated block. Note
144 -- that the argument Control_Block is not used other than as the argument
145 -- that controls which version of AFCB_Allocate is called.
147 procedure AFCB_Close
(File
: not null access AFCB
) is abstract;
148 -- Performs any specialized close actions on a file before the file is
149 -- actually closed at the system level. This is called by Close, and
150 -- the reason we need the primitive operation is for the automatic
151 -- close operations done as part of finalization.
153 procedure AFCB_Free
(File
: not null access AFCB
) is abstract;
154 -- Frees the AFCB referenced by the given parameter. It is not necessary
155 -- to free the strings referenced by the Form and Name fields, but if the
156 -- extension has any other heap objects, they must be freed as well. This
157 -- procedure must be overridden by each individual file package.
159 end System
.File_Control_Block
;