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eucrypt_crc32_div...    1 ------------------------------------------------------------------------------
eucrypt_crc32_div...    2 ------------------------------------------------------------------------------
eucrypt_crc32_div...    3 -- This file is part of 'CRC32'                                             --
eucrypt_crc32_div...    4 --                                                                          --
eucrypt_crc32_div...    5 -- You do not have, nor can you ever acquire the right to use, copy or      --
eucrypt_crc32_div...    6 -- distribute this software ; Should you use this software for any purpose, -- 
eucrypt_crc32_div...    7 -- or copy and distribute it to anyone or in any manner, you are breaking   --
eucrypt_crc32_div...    8 -- the laws of whatever soi-disant jurisdiction, and you promise to         --
eucrypt_crc32_div...    9 -- continue doing so for the indefinite future. In any case, please         --
eucrypt_crc32_div...   10 -- always : read and understand any software ; verify any PGP signatures    --
eucrypt_crc32_div...   11 -- that you use - for any purpose.                                          --
eucrypt_crc32_div...   12 --                                                                          --
eucrypt_crc32_div...   13 -- See also http://trilema.com/2015/a-new-software-licensing-paradigm .     --
eucrypt_crc32_div...   14 ------------------------------------------------------------------------------
eucrypt_crc32_div...   15 ------------------------------------------------------------------------------
eucrypt_crc32_div...   16 
eucrypt_crc32_div...   17   -- CRC32, modulo 2 based implementation
eucrypt_crc32_div...   18   -- S.MG, 2018
eucrypt_crc32_div...   19   --
eucrypt_crc32_div...   20   -- The CRC32 is a checksum calculated as the remainder of dividing
eucrypt_crc32_div...   21   -- the input data by the 0x04C11DB7 polynomial. Specifications:
eucrypt_crc32_div...   22   -- Name   : "CRC-32"
eucrypt_crc32_div...   23   -- Width  : 32        (number of bits)
eucrypt_crc32_div...   24   -- Poly   : 04C11DB7  (generator polynomial)
eucrypt_crc32_div...   25   -- Init   : FFFFFFFF
eucrypt_crc32_div...   26   -- RefIn  : True      (input is reflected)  
eucrypt_crc32_div...   27   -- RefOut : True      (output is reflected)
eucrypt_crc32_div...   28   -- XorOut : FFFFFFFF
eucrypt_crc32_div...   29   -- Check  : CBF43926  (expected value for input "123456789")
eucrypt_crc32_div...   30   --
eucrypt_crc32_div...   31   -- This implementation is based on the CRC32 example in:
eucrypt_crc32_div...   32   -- Ross N. Williams, A PAINLESS GUIDE TO CRC ERROR DETECTION ALGORITHMS
eucrypt_crc32_div...   33   -- version 3, 1993
eucrypt_crc32_div...   34   -- http://ross.net/crc/download/crc_v3.txt
eucrypt_crc32_div...   35 
eucrypt_crc32_div...   36 with Interfaces; use Interfaces;
eucrypt_crc32_div...   37 
eucrypt_crc32_div...   38 package CRC32 is
eucrypt_crc32_div...   39   -- local, shorthand version of Interfaces. types
eucrypt_crc32_div...   40   subtype CRC32 is Interfaces.Unsigned_32;
eucrypt_crc32_div...   41   subtype Octet is Interfaces.Unsigned_8;
eucrypt_crc32_div...   42 
eucrypt_crc32_div...   43   type Octet_Array is array( Integer range <> ) of Octet;
eucrypt_crc32_div...   44 
eucrypt_crc32_div...   45   -- interface for external callers
eucrypt_crc32_div...   46     -- calculate CRC32 for the given string
eucrypt_crc32_div...   47   function CRC( S: in String ) return CRC32;
eucrypt_crc32_div...   48 
eucrypt_crc32_div...   49     -- calculate CRC32 for the given array of octets
eucrypt_crc32_div...   50   function CRC( Data: in Octet_Array ) return CRC32;
eucrypt_crc32_div...   51   
eucrypt_crc32_div...   52   -- internal constants and helper methods
eucrypt_crc32_div...   53 private
eucrypt_crc32_div...   54   -- These functions need to be imported to get to the shift operators. 
eucrypt_crc32_div...   55   -- (Specific for GNAT)
eucrypt_crc32_div...   56   function Shift_Left ( Value  : CRC32; 
eucrypt_crc32_div...   57                         Amount : Natural )
eucrypt_crc32_div...   58                         return CRC32;
eucrypt_crc32_div...   59   function Shift_Right ( Value  : CRC32; 
eucrypt_crc32_div...   60                          Amount : Natural )
eucrypt_crc32_div...   61                          return CRC32;
eucrypt_crc32_div...   62   function Rotate_Left ( Value  : CRC32; 
eucrypt_crc32_div...   63                          Amount : Natural )
eucrypt_crc32_div...   64                          return CRC32;
eucrypt_crc32_div...   65   function Rotate_Right ( Value  : CRC32; 
eucrypt_crc32_div...   66                          Amount : Natural )
eucrypt_crc32_div...   67                          return CRC32;
eucrypt_crc32_div...   68   
eucrypt_crc32_div...   69   pragma Import ( Intrinsic, Rotate_Left );
eucrypt_crc32_div...   70   pragma Import ( Intrinsic, Rotate_Right );
eucrypt_crc32_div...   71   pragma Import ( Intrinsic, Shift_Left  );
eucrypt_crc32_div...   72   pragma Import ( Intrinsic, Shift_Right ); 
eucrypt_crc32_div...   73   
eucrypt_crc32_div...   74   
eucrypt_crc32_div...   75   -- The Shift_Left instruction does not return the bit that was shifted
eucrypt_crc32_div...   76   -- We need a mask for this last bit
eucrypt_crc32_div...   77   -- Bits are counted from right to left, starting at 0
eucrypt_crc32_div...   78   Bit31 : constant CRC32 := 16#80_00_00_00#;
eucrypt_crc32_div...   79   
eucrypt_crc32_div...   80   procedure CRC_Step(C : in out CRC32; R : in out CRC32);
eucrypt_crc32_div...   81   pragma Inline_Always(CRC_Step);
eucrypt_crc32_div...   82   
eucrypt_crc32_div...   83   function Bits_Reverse(A : in CRC32) return CRC32;
eucrypt_crc32_div...   84   
eucrypt_crc32_div...   85 end CRC32;