------------------------------------------------------------------------------ -- -- -- GNAT RUN-TIME COMPONENTS -- -- -- -- S Y S T E M . F I L E _ C O N T R O L _ B L O C K -- -- -- -- S p e c -- -- -- -- -- -- Copyright (C) 1992-2000 Free Software Foundation, Inc. -- -- -- -- GNAT is free software; you can redistribute it and/or modify it under -- -- terms of the GNU General Public License as published by the Free Soft- -- -- ware Foundation; either version 2, or (at your option) any later ver- -- -- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License -- -- for more details. You should have received a copy of the GNU General -- -- Public License distributed with GNAT; see file COPYING. If not, write -- -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, -- -- MA 02111-1307, USA. -- -- -- -- As a special exception, if other files instantiate generics from this -- -- unit, or you link this unit with other files to produce an executable, -- -- this unit does not by itself cause the resulting executable to be -- -- covered by the GNU General Public License. This exception does not -- -- however invalidate any other reasons why the executable file might be -- -- covered by the GNU Public License. -- -- -- -- GNAT was originally developed by the GNAT team at New York University. -- -- Extensive contributions were provided by Ada Core Technologies Inc. -- -- -- ------------------------------------------------------------------------------ -- This package contains the declaration of the basic file control block -- shared between Text_IO, Sequential_IO, Direct_IO and Streams.Stream_IO. -- The actual control blocks are derived from this block by extension. The -- control block is itself derived from Ada.Streams.Root_Stream_Type which -- facilitates implementation of Stream_IO.Stream and Text_Streams.Stream. with Ada.Streams; with Interfaces.C_Streams; package System.File_Control_Block is ----------------------------- -- Ada File Control Block -- ----------------------------- -- The Ada file control block is an abstract extension of the root -- stream type. This allows a file to be treated directly as a stream -- for the purposes of Stream_IO, or stream operations on a text file. -- The individual I/O packages extend this type with package specific -- fields to create the concrete types to which the routines in this -- package can be applied. -- The type File_Type in the individual packages is an access to the -- extended file control block. The value is null if the file is not -- open, and a pointer to the control block if the file is open. type Pstring is access all String; -- Used to hold name and form strings type File_Mode is (In_File, Inout_File, Out_File, Append_File); -- File mode (union of file modes permitted by individual packages, -- the types File_Mode in the individual packages are declared to -- allow easy conversion to and from this general type. type Shared_Status_Type is (Yes, No, None); -- This type is used to define the sharing status of a file. The default -- setting of None is used if no "shared=xxx" appears in the form string -- when a file is created or opened. For a file with Shared_Status set to -- None, Use_Error will be raised if any other file is opened or created -- with the same full name. Yes/No are set in response to the presence -- of "shared=yes" or "shared=no" in the form string. In either case it -- is permissible to have multiple files opened with the same full name. -- All files opened simultaneously with "shared=yes" will share the same -- stream with the semantics specified in the RM for file sharing. All -- files opened with "shared=no" will have their own stream. type AFCB; type AFCB_Ptr is access all AFCB'Class; type AFCB is abstract new Ada.Streams.Root_Stream_Type with record Stream : Interfaces.C_Streams.FILEs; -- The file descriptor Name : Pstring; -- A pointer to the file name. The file name is null for temporary -- files, and also for standard files (stdin, stdout, stderr). The -- name is always null-terminated if it is non-null. Form : Pstring; -- A pointer to the form string. This is the string used in the -- fopen call, and must be supplied by the caller (there are no -- defaults at this level). The string is always null-terminated. Mode : File_Mode; -- The file mode. No checks are made that the mode is consistent -- with the form used to fopen the file. Is_Regular_File : Boolean; -- A flag indicating if the file is a regular file Is_Temporary_File : Boolean; -- A flag set only for temporary files (i.e. files created using the -- Create function with a null name parameter, using tmpfile). This -- is currently not used since temporary files are deleted by the -- operating system, but it is set properly in case some systems -- need this information in the future. Is_System_File : Boolean; -- A flag set only for system files (stdin, stdout, stderr) Is_Text_File : Boolean; -- A flag set if the file was opened in text mode Shared_Status : Shared_Status_Type; -- Indicates sharing status of file, see description of type above Access_Method : Character; -- Set to 'Q', 'S', 'T, 'D' for Sequential_IO, Stream_IO, Text_IO -- Direct_IO file (used to validate file sharing request). Next : AFCB_Ptr; Prev : AFCB_Ptr; -- All open files are kept on a doubly linked chain, with these -- pointers used to maintain the next and previous pointers. end record; ---------------------------------- -- Primitive Operations of AFCB -- ---------------------------------- -- Note that we inherit the abstract operations Read and Write from -- the base type. These must be overridden by the individual file -- access methods to provide Stream Read/Write access. function AFCB_Allocate (Control_Block : AFCB) return AFCB_Ptr is abstract; -- Given a control block, allocate space for a control block of the same -- type on the heap, and return the pointer to this allocated block. Note -- that the argument Control_Block is not used other than as the argument -- that controls which version of AFCB_Allocate is called. procedure AFCB_Close (File : access AFCB) is abstract; -- Performs any specialized close actions on a file before the file is -- actually closed at the system level. This is called by Close, and -- the reason we need the primitive operation is for the automatic -- close operations done as part of finalization. procedure AFCB_Free (File : access AFCB) is abstract; -- Frees the AFCB referenced by the given parameter. It is not necessary -- to free the strings referenced by the Form and Name fields, but if the -- extension has any other heap objects, they must be freed as well. This -- procedure must be overridden by each individual file package. end System.File_Control_Block;