gcc/ada/krunch.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                               K R U N C H                                --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2021, 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.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNAT; see file COPYING3.  If not, go to --
  19 -- http://www.gnu.org/licenses for a complete copy of the license.          --
  20 --                                                                          --
  21 -- GNAT was originally developed  by the GNAT team at  New York University. --
  22 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  23 --                                                                          --
  24 ------------------------------------------------------------------------------
  25
  26 --  This procedure implements file name crunching
  27
  28 --    First, the name is divided into segments separated by minus signs and
  29 --    underscores, then all minus signs and underscores are eliminated. If
  30 --    this leaves the name short enough, we are done.
  31
  32 --    If not, then the longest segment is located (left-most if there are
  33 --    two of equal length), and shortened by dropping its last character.
  34 --    This is repeated until the name is short enough.
  35
  36 --    As an example, consider the krunch of our-strings-wide_fixed.adb
  37 --    to fit the name into 8 characters as required by DOS:
  38
  39 --      our-strings-wide_fixed      22
  40 --      our strings wide fixed      19
  41 --      our string  wide fixed      18
  42 --      our strin   wide fixed      17
  43 --      our stri    wide fixed      16
  44 --      our stri    wide fixe       15
  45 --      our str     wide fixe       14
  46 --      our str     wid  fixe       13
  47 --      our str     wid  fix        12
  48 --      ou  str     wid  fix        11
  49 --      ou  st      wid  fix        10
  50 --      ou  st      wi   fix         9
  51 --      ou  st      wi   fi          8
  52
  53 --      Final file name: OUSTWIFX.ADB
  54
  55 --    A special rule applies for children of System, Ada, Gnat, and Interfaces.
  56 --    In these cases, the following special prefix replacements occur:
  57
  58 --       ada-        replaced by  a-
  59 --       gnat-       replaced by  g-
  60 --       interfaces- replaced by  i-
  61 --       system-     replaced by  s-
  62
  63 --    The rest of the name is krunched in the usual manner described above.
  64 --    In addition, these names, as well as the names of the renamed packages
  65 --    from the obsolescent features annex, are always krunched to 8 characters
  66 --    regardless of the setting of Maxlen.
  67
  68 --    As an example of this special rule, consider ada-strings-wide_fixed.adb
  69 --    which gets krunched as follows:
  70
  71 --      ada-strings-wide_fixed      22
  72 --      a-  strings wide fixed      18
  73 --      a-  string  wide fixed      17
  74 --      a-  strin   wide fixed      16
  75 --      a-  stri    wide fixed      15
  76 --      a-  stri    wide fixe       14
  77 --      a-  str     wide fixe       13
  78 --      a-  str     wid  fixe       12
  79 --      a-  str     wid  fix        11
  80 --      a-  st      wid  fix        10
  81 --      a-  st      wi   fix         9
  82 --      a-  st      wi   fi          8
  83
  84 --      Final file name: A-STWIFX.ADB
  85
  86 --  Since children of units named A, G, I or S might conflict with the names
  87 --  of predefined units, the naming rule in that case is that the first hyphen
  88 --  is replaced by a tilde sign.
  89
  90 --  Note: as described below, this special treatment of predefined library
  91 --  unit file names can be inhibited by setting the No_Predef flag.
  92
  93 --  Of course there is no guarantee that this algorithm results in uniquely
  94 --  crunched names (nor, obviously, is there any algorithm which would do so)
  95 --  In fact we run into such a case in the standard library routines with
  96 --  children of Wide_Text_IO, so a special rule is applied to deal with this
  97 --  clash, namely the prefix ada-wide_text_io- is replaced by a-wt- and then
  98 --  the normal crunching rules are applied, so that for example, the unit:
  99
 100 --    Ada.Wide_Text_IO.Float_IO
 101
 102 --  has the file name
 103
 104 --    a-wtflio
 105
 106 --  More problems arise with Wide_Wide, so we replace this sequence by
 107 --  a z (which is not used much) and also (as in the Wide_Text_IO case),
 108 --  we replace the prefix ada.wide_wide_text_io- by a-zt- and then
 109 --  the normal crunching rules are applied.
 110
 111 --  An additional trick is used for Ada.Long_Long_Long_Integer_*_IO, where
 112 --  the Integer word is dropped.
 113
 114 --  The units implementing the support of 128-bit types are crunched to 9 and
 115 --  System.Compare_Array_* is replaced with System.CA_* before crunching.
 116
 117 --  These are the only irregularity required (so far) to keep the file names
 118 --  unique in the standard predefined libraries.
 119
 120 procedure Krunch
 121   (Buffer        : in out String;
 122    Len           : in out Natural;
 123    Maxlen        : Natural;
 124    No_Predef     : Boolean);
 125 pragma Elaborate_Body (Krunch);
 126 --  The full file name is stored in Buffer (1 .. Len) on entry. The file
 127 --  name is crunched in place and on return Len is updated, so that the
 128 --  resulting krunched name is in Buffer (1 .. Len) where Len <= Maxlen.
 129 --  Note that Len may be less than or equal to Maxlen on entry, in which
 130 --  case it may be possible that Krunch does not modify Buffer. The fourth
 131 --  parameter, No_Predef, is a switch which, if set to True, disables the
 132 --  normal special treatment of predefined library unit file names.
 133 --
 134 --  Note: the string Buffer must have a lower bound of 1, and may not
 135 --  contain any blanks (in particular, it must not have leading blanks).