gcc/ada/libgnat/s-valuns.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                       S Y S T E M . V A L _ U N S                        --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2017, 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 routines for scanning modular Unsigned
  33 --  values for use in Text_IO.Modular_IO, and the Value attribute.
  34
  35 with System.Unsigned_Types;
  36
  37 package System.Val_Uns is
  38    pragma Pure;
  39
  40    function Scan_Raw_Unsigned
  41      (Str : String;
  42       Ptr : not null access Integer;
  43       Max : Integer) return System.Unsigned_Types.Unsigned;
  44    --  This function scans the string starting at Str (Ptr.all) for a valid
  45    --  integer according to the syntax described in (RM 3.5(43)). The substring
  46    --  scanned extends no further than Str (Max).  Note: this does not scan
  47    --  leading or trailing blanks, nor leading sign.
  48    --
  49    --  There are three cases for the return:
  50    --
  51    --  If a valid integer is found, then Ptr.all is updated past the last
  52    --  character of the integer.
  53    --
  54    --  If no valid integer is found, then Ptr.all points either to an initial
  55    --  non-digit character, or to Max + 1 if the field is all spaces and the
  56    --  exception Constraint_Error is raised.
  57    --
  58    --  If a syntactically valid integer is scanned, but the value is out of
  59    --  range, or, in the based case, the base value is out of range or there
  60    --  is an out of range digit, then Ptr.all points past the integer, and
  61    --  Constraint_Error is raised.
  62    --
  63    --  Note: these rules correspond to the requirements for leaving the pointer
  64    --  positioned in Text_IO.Get. Note that the rules as stated in the RM would
  65    --  seem to imply that for a case like:
  66    --
  67    --    8#12345670009#
  68    --
  69    --  the pointer should be left at the first # having scanned out the longest
  70    --  valid integer literal (8), but in fact in this case the pointer points
  71    --  past the final # and Constraint_Error is raised. This is the behavior
  72    --  expected for Text_IO and enforced by the ACATS tests.
  73    --
  74    --  If a based literal is malformed in that a character other than a valid
  75    --  hexadecimal digit is encountered during scanning out the digits after
  76    --  the # (this includes the case of using the wrong terminator, : instead
  77    --  of # or vice versa) there are two cases. If all the digits before the
  78    --  non-digit are in range of the base, as in
  79    --
  80    --    8#100x00#
  81    --    8#100:
  82    --
  83    --  then in this case, the "base" value before the initial # is returned as
  84    --  the result, and the pointer points to the initial # character on return.
  85    --
  86    --  If an out of range digit has been detected before the invalid character,
  87    --  as in:
  88    --
  89    --   8#900x00#
  90    --   8#900:
  91    --
  92    --  then the pointer is also left at the initial # character, but constraint
  93    --  error is raised reflecting the encounter of an out of range digit.
  94    --
  95    --  Finally if we have an unterminated fixed-point constant where the final
  96    --  # or : character is missing, Constraint_Error is raised and the pointer
  97    --  is left pointing past the last digit, as in:
  98    --
  99    --   8#22
 100    --
 101    --  This string results in a Constraint_Error with the pointer pointing
 102    --  past the second 2.
 103    --
 104    --  Note: if Str is empty, i.e. if Max is less than Ptr, then this is a
 105    --  special case of an all-blank string, and Ptr is unchanged, and hence
 106    --  is greater than Max as required in this case.
 107    --
 108    --  Note: this routine should not be called with Str'Last = Positive'Last.
 109    --  If this occurs Program_Error is raised with a message noting that this
 110    --  case is not supported. Most such cases are eliminated by the caller.
 111
 112    function Scan_Unsigned
 113      (Str : String;
 114       Ptr : not null access Integer;
 115       Max : Integer) return System.Unsigned_Types.Unsigned;
 116    --  Same as Scan_Raw_Unsigned, except scans optional leading
 117    --  blanks, and an optional leading plus sign.
 118    --
 119    --  Note: if a minus sign is present, Constraint_Error will be raised.
 120    --  Note: trailing blanks are not scanned.
 121
 122    function Value_Unsigned
 123      (Str : String) return System.Unsigned_Types.Unsigned;
 124    --  Used in computing X'Value (Str) where X is a modular integer type whose
 125    --  modulus does not exceed the range of System.Unsigned_Types.Unsigned. Str
 126    --  is the string argument of the attribute. Constraint_Error is raised if
 127    --  the string is malformed, or if the value is out of range.
 128
 129 end System.Val_Uns;