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8.10 Operations on C Streams

The package Interfaces.C_Streams provides an Ada program with direct access to the C library functions for operations on C streams:

 
package Interfaces.C_Streams is
  -- Note: the reason we do not use the types that are in
  -- Interfaces.C is that we want to avoid dragging in the
  -- code in this unit if possible.
  subtype chars is System.Address;
  -- Pointer to null-terminated array of characters
  subtype FILEs is System.Address;
  -- Corresponds to the C type FILE*
  subtype voids is System.Address;
  -- Corresponds to the C type void*
  subtype int is Integer;
  subtype long is Long_Integer;
  -- Note: the above types are subtypes deliberately, and it
  -- is part of this spec that the above correspondences are
  -- guaranteed. This means that it is legitimate to, for
  -- example, use Integer instead of int. We provide these
  -- synonyms for clarity, but in some cases it may be
  -- convenient to use the underlying types (for example to
  -- avoid an unnecessary dependency of a spec on the spec
  -- of this unit).
  type size_t is mod 2 ** Standard'Address_Size;
  NULL_Stream : constant FILEs;
  -- Value returned (NULL in C) to indicate an
  -- fdopen/fopen/tmpfile error
  ----------------------------------
  -- Constants Defined in stdio.h --
  ----------------------------------
  EOF : constant int;
  -- Used by a number of routines to indicate error or 
  -- end of file
  IOFBF : constant int;
  IOLBF : constant int;
  IONBF : constant int;
  -- Used to indicate buffering mode for setvbuf call
  SEEK_CUR : constant int;
  SEEK_END : constant int;
  SEEK_SET : constant int;
  -- Used to indicate origin for fseek call
  function stdin return FILEs;
  function stdout return FILEs;
  function stderr return FILEs;
  -- Streams associated with standard files
  --------------------------
  -- Standard C functions --
  --------------------------
  -- The functions selected below are ones that are
  -- available in DOS, OS/2, UNIX and Xenix (but not
  -- necessarily in ANSI C). These are very thin interfaces
  -- which copy exactly the C headers. For more
  -- documentation on these functions, see the Microsoft C 
  -- "Run-Time Library Reference" (Microsoft Press, 1990,
  -- ISBN 1-55615-225-6), which includes useful information
  -- on system compatibility.
  procedure clearerr (stream : FILEs);
  function fclose (stream : FILEs) return int;
  function fdopen (handle : int; mode : chars) return FILEs; 
  function feof (stream : FILEs) return int; 
  function ferror (stream : FILEs) return int; 
  function fflush (stream : FILEs) return int; 
  function fgetc (stream : FILEs) return int; 
  function fgets (strng : chars; n : int; stream : FILEs) 
      return chars; 
  function fileno (stream : FILEs) return int; 
  function fopen (filename : chars; Mode : chars) 
      return FILEs;
  -- Note: to maintain target independence, use
  -- text_translation_required, a boolean variable defined in
  -- a-sysdep.c to deal with the target dependent text
  -- translation requirement. If this variable is set, 
  -- then  b/t should be appended to the standard mode
  -- argument to set the text translation mode off or on 
  -- as required.
  function fputc (C : int; stream : FILEs) return int;
  function fputs (Strng : chars; Stream : FILEs) return int;
  function fread
     (buffer : voids;
      size : size_t;
      count : size_t;
      stream : FILEs)
      return size_t;
  function freopen
     (filename : chars;
      mode : chars;
      stream : FILEs)
      return FILEs;
  function fseek
     (stream : FILEs;
      offset : long;
      origin : int)
      return int;
  function ftell (stream : FILEs) return long;
  function fwrite
     (buffer : voids;
      size : size_t;
      count : size_t;
      stream : FILEs)
      return size_t; 
  function isatty (handle : int) return int;
  procedure mktemp (template : chars);
  -- The return value (which is just a pointer to template)
  -- is discarded
  procedure rewind (stream : FILEs);
  function rmtmp return int;
  function setvbuf
     (stream : FILEs;
      buffer : chars;
      mode : int;
      size : size_t)
      return int;

  function tmpfile return FILEs;
  function ungetc (c : int; stream : FILEs) return int;
  function unlink (filename : chars) return int;
  ---------------------
  -- Extra functions --
  ---------------------
  -- These functions supply slightly thicker bindings than
  -- those above. They are derived from functions in the 
  -- C Run-Time Library, but may do a bit more work than
  -- just directly calling one of the Library functions.
  function is_regular_file (handle : int) return int;
  -- Tests if given handle is for a regular file (result 1)
  -- or for a non-regular file (pipe or device, result 0).
  ---------------------------------
  -- Control of Text/Binary Mode --
  ---------------------------------
  -- If text_translation_required is true, then the following
  -- functions may be used to dynamically switch a file from
  -- binary to text mode or vice versa. These functions have
  -- no effect if text_translation_required is false (i.e. in
  -- normal UNIX mode). Use fileno to get a stream handle.
  procedure set_binary_mode (handle : int);
  procedure set_text_mode (handle : int);
  ----------------------------
  -- Full Path Name support --
  ----------------------------
  procedure full_name (nam : chars; buffer : chars);
  -- Given a NUL terminated string representing a file
  -- name, returns in buffer a NUL terminated string
  -- representing the full path name for the file name. 
  -- On systems where it is relevant the   drive is also
  -- part of the full path name. It is the responsibility 
  -- of the caller to pass an actual parameter for buffer
  -- that is big enough for any full path name. Use
  -- max_path_len given below as the size of buffer.
  max_path_len : integer;
  -- Maximum length of an allowable full path name on the
  -- system, including a terminating NUL character.
end Interfaces.C_Streams;


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