PL/SQL implementation of the crc32()

Recently I was kindly asked to share PL/SQL implementation of the crc32() I developed once. I slightly polished and optimized it. NO WARRANTY is implied. Please let me know if you find any errors.

/***********************************************************************
** These functions calculate crc32
** calculate   -- this one is PLS_INTEGER based, some simple modifications
**                are needed to make it working on < 9i editions
** calculate10 -- uses enriched Oracle 10g BITAND (INTEGER)
**
**   a_data_i -- input string
**   a_init_i -- crc32 initial value
**
** As an alternative one can consider using CRC32 java class
** http://java.sun.com/j2se/1.4.2/docs/api/java/util/zip/CRC32.html
** or to use dbms_crypto/dbms_obfuscation_toolkit's hash functions
*/
/* Example:

SQL> !perl -e 'use String::CRC32; print crc32("quick brown fox jumps over the lazy dog") . "\n";'

998814576

SQL> VAR crc32 NUMBER
SQL> EXEC :crc32 := crc32.calculate('quick brown fox jumps over the lazy dog', :crc32);
SQL> PRINT crc32

     CRC32
----------
 998814576

SQL> BEGIN         
  2    :crc32 := 0;
  3    :crc32 := crc32.calculate('quick ', :crc32);
  4    :crc32 := crc32.calculate('brown ', :crc32);
  5    :crc32 := crc32.calculate('fox ', :crc32);
  6    :crc32 := crc32.calculate('jumps ', :crc32);
  7    :crc32 := crc32.calculate('over ', :crc32);
  8    :crc32 := crc32.calculate('the ', :crc32);
  9    :crc32 := crc32.calculate('lazy ', :crc32);
 10    :crc32 := crc32.calculate('dog', :crc32);
 11  END;
 12  /

PL/SQL procedure successfully completed.

SQL> PRINT crc32 

     CRC32
----------
 998814576

*/