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   1  --  UnZip.Decompress.Huffman
   2  ----------------------------
   3  --  Huffman tree generation and deletion.
   4  --  Originally from info-zip's unzip, data structure rewritten by G. de Montmollin
   5  
   6  --  Legal licensing note:
   7  
   8  --  Copyright (c) 1999 .. 2019 Gautier de Montmollin
   9  --  SWITZERLAND
  10  
  11  --  Permission is hereby granted, free of charge, to any person obtaining a copy
  12  --  of this software and associated documentation files (the "Software"), to deal
  13  --  in the Software without restriction, including without limitation the rights
  14  --  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  15  --  copies of the Software, and to permit persons to whom the Software is
  16  --  furnished to do so, subject to the following conditions:
  17  
  18  --  The above copyright notice and this permission notice shall be included in
  19  --  all copies or substantial portions of the Software.
  20  
  21  --  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  22  --  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  23  --  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  24  --  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  25  --  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  26  --  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  27  --  THE SOFTWARE.
  28  
  29  --  NB: this is the MIT License, as found on the site
  30  --  http://www.opensource.org/licenses/mit-license.php
  31  
  32  private package UnZip.Decompress.Huffman is
  33  
  34    type HufT_table;
  35    type p_HufT_table is access HufT_table;
  36  
  37    type HufT is record
  38      extra_bits : Natural;
  39      bits       : Natural;
  40      n          : Natural;
  41      next_table : p_HufT_table;
  42    end record;
  43  
  44    invalid : constant := 99; -- invalid value for extra bits
  45  
  46    type HufT_table is array (Natural range <>) of HufT;
  47  
  48    --  Linked list just for destroying Huffman tables
  49  
  50    type Table_list;
  51    type p_Table_list is access Table_list;
  52  
  53    type Table_list is record
  54      table : p_HufT_table;
  55      next  : p_Table_list;
  56    end record;
  57  
  58    type Length_array is array (Integer range <>) of Natural;
  59  
  60    empty : constant Length_array (1 .. 0) := (others => 0);
  61  
  62    --  Free huffman tables starting with table where t points to
  63    procedure HufT_free (tl : in out p_Table_list);
  64  
  65    --  Build huffman table from code lengths given by array b.all
  66    procedure HufT_build (b    : Length_array;
  67                          s    : Integer;
  68                          d, e : Length_array;
  69                          tl   :    out p_Table_list;
  70                          m    : in out Integer;
  71               huft_incomplete :    out Boolean);
  72  
  73    --  Possible exceptions occuring in huft_build
  74    huft_error,                    -- bad tree constructed
  75    huft_out_of_memory : exception; -- not enough memory
  76  
  77  end UnZip.Decompress.Huffman;