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   1  --  Huffman.Encoding
   2  --------------------
   3  --
   4  --  Legal licensing note:
   5  --
   6  --  Copyright (c) 2024 Gautier de Montmollin (maintainer of the Ada version)
   7  --  SWITZERLAND
   8  --
   9  --  Permission is hereby granted, free of charge, to any person obtaining a copy
  10  --  of this software and associated documentation files (the "Software"), to deal
  11  --  in the Software without restriction, including without limitation the rights
  12  --  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  13  --  copies of the Software, and to permit persons to whom the Software is
  14  --  furnished to do so, subject to the following conditions:
  15  --
  16  --  The above copyright notice and this permission notice shall be included in
  17  --  all copies or substantial portions of the Software.
  18  --
  19  --  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  20  --  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  21  --  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  22  --  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  23  --  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  24  --  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  25  --  THE SOFTWARE.
  26  --
  27  --  NB: this is the MIT License, as found 03-Nov-2024 on the site
  28  --  http://www.opensource.org/licenses/mit-license.php
  29  
  30  with Interfaces;
  31  
  32  package Huffman.Encoding is
  33  
  34    invalid : constant := -1;
  35  
  36    subtype Code_Range is Interfaces.Integer_32 range invalid .. Interfaces.Integer_32'Last;
  37  
  38    type Length_Code_Pair is record
  39      bit_length : Natural;                --  Huffman code length, in bits
  40      code       : Code_Range := invalid;  --  The code itself (the 0's and 1's)
  41    end record;
  42  
  43    type Descriptor is array (Natural range <>) of Length_Code_Pair;
  44  
  45    --  The Prepare_Huffman_Codes procedure finds the Huffman
  46    --  code for all values, given the bit_length imposed as input.
  47    --
  48    procedure Prepare_Codes
  49      (hd               : in out Descriptor;
  50       max_huffman_bits : in     Positive;
  51       invert_bit_order : in     Boolean);
  52  
  53  end Huffman.Encoding;