gcc/ada/libgnat/g-io_aux.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUN-TIME COMPONENTS                         --
   4 --                                                                          --
   5 --                          G N A T . I O _ A U X                           --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --                     Copyright (C) 1995-2023, AdaCore                     --
  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 with Interfaces.C_Streams; use Interfaces.C_Streams;
  33
  34 package body GNAT.IO_Aux is
  35
  36    Buflen : constant := 2000;
  37    --  Buffer length. Works for any non-zero value, larger values take
  38    --  more stack space, smaller values require more recursion.
  39
  40    -----------------
  41    -- File_Exists --
  42    -----------------
  43
  44    function File_Exists (Name : String) return Boolean
  45    is
  46       Namestr : aliased String (1 .. Name'Length + 1);
  47       --  Name as given with ASCII.NUL appended
  48
  49    begin
  50       Namestr (1 .. Name'Length) := Name;
  51       Namestr (Name'Length + 1)  := ASCII.NUL;
  52       return file_exists (Namestr'Address) /= 0;
  53    end File_Exists;
  54
  55    --------------
  56    -- Get_Line --
  57    --------------
  58
  59    --  Current_Input case
  60
  61    function Get_Line return String is
  62       Buffer : String (1 .. Buflen);
  63       --  Buffer to read in chunks of remaining line. Will work with any
  64       --  size buffer. We choose a length so that most of the time no
  65       --  recursion will be required.
  66
  67       Last : Natural;
  68
  69    begin
  70       Ada.Text_IO.Get_Line (Buffer, Last);
  71
  72       --  If the buffer is not full, then we are all done
  73
  74       if Last < Buffer'Last then
  75          return Buffer (1 .. Last);
  76
  77       --  Otherwise, we still have characters left on the line. Note that
  78       --  as specified by (RM A.10.7(19)) the end of line is not skipped
  79       --  in this case, even if we are right at it now.
  80
  81       else
  82          return Buffer & GNAT.IO_Aux.Get_Line;
  83       end if;
  84    end Get_Line;
  85
  86    --  Case of reading from a specified file. Note that we could certainly
  87    --  share code between these two versions, but these are very short
  88    --  routines, and we may as well aim for maximum speed, cutting out an
  89    --  intermediate call (calls returning string may be somewhat slow)
  90
  91    function Get_Line (File : Ada.Text_IO.File_Type) return String is
  92       Buffer : String (1 .. Buflen);
  93       Last   : Natural;
  94
  95    begin
  96       Ada.Text_IO.Get_Line (File, Buffer, Last);
  97
  98       if Last < Buffer'Last then
  99          return Buffer (1 .. Last);
 100       else
 101          return Buffer & Get_Line (File);
 102       end if;
 103    end Get_Line;
 104
 105 end GNAT.IO_Aux;