shared_source/c_datd/crchashfuncs.h

/* $Header: /cvsroot/esrg/sfesrg/esrgpcpj/shared/c_datd/crchashfuncs.h,v 1.3 2001/07/26 21:41:21 dtashley Exp $ */

//--------------------------------------------------------------------------------
//Copyright 2001 David T. Ashley
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//possible use to the public, the best way to achieve this is to make it
//free software which everyone can redistribute and change under these terms.
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//to attach them to the start of each source file to most effectively
//state the exclusion of warranty; and each file should have at least
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//Public License instead of this License.  But first, please read
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//-------------------------------------------------------------------------------------------------
//--------------------------------------------------------------------------------
//This software module is concerned with functions to support the generation
//of CRCs and hash functions.  CRCs and hash functions are similar in that they
//provide an abstraction of a large amount of data, although CRCs may have better
//(or different) statistical properties than hash functions.  These functions
//are split out from any specific application for maximum reusability of the
//code.

#ifndef CRCHASHFUNCS_H_INCLUDED
   #define CRCHASHFUNCS_H_INCLUDED

   #ifdef MODULE_CRCHASHFUNCS
      #define DECMOD_CRCHASHFUNCS
   #else
      #define DECMOD_CRCHASHFUNCS extern
   #endif

   //Define the state object that holds CRC-32 intermediate results as the CRC is
   //being formed.  This is conceptually private for the caller.
   //
   struct CRCHASHFUNCS_Crc32StateStruct
      {
      unsigned crc;
      //This is the only state for now.
      };

   //All CRC32 functions are courtesy of Richard A. Ellingson
   //from the Internet.
   //
   //Checks the CRC-32 table for integrity, returns non-zero if
   //the table is OK, or 0 if the table is corrupted.  The table
   //is a table of constants in memory--it is not known how
   //much protection the "const" keyword can give it, i.e. if
   //the tools can put it in a memory segment where some kind
   //of protection is afforded by the OS.
   DECMOD_CRCHASHFUNCS 
   int CRCHASHFUNCS_Crc32TableCheck(void);

   //Initializes the CRC formation structure.
   DECMOD_CRCHASHFUNCS 
   void CRCHASHFUNCS_Crc32StateStructOpen(struct CRCHASHFUNCS_Crc32StateStruct *arg);

   //Adds data to it.
   DECMOD_CRCHASHFUNCS
   void CRCHASHFUNCS_Crc32StateStructAddData(struct CRCHASHFUNCS_Crc32StateStruct *arg,
                                             void *data,
                                             unsigned len);

   //Reads the CRC out at any time.
   DECMOD_CRCHASHFUNCS 
   unsigned CRCHASHFUNCS_Crc32Extract(struct CRCHASHFUNCS_Crc32StateStruct *arg);

   //Closes the structure.
   DECMOD_CRCHASHFUNCS 
   void CRCHASHFUNCS_Crc32StateStructClose(struct CRCHASHFUNCS_Crc32StateStruct *arg);

   DECMOD_CRCHASHFUNCS const char *CRCHASHFUNCS_cvcinfo(void);
   DECMOD_CRCHASHFUNCS const char *CRCHASHFUNCS_hvcinfo(void);

   //Definition of the version of the H file, used for providing version control
   //information to external callers.
   #define CRCHASHFUNCS_H_VERSION ("$Header: /cvsroot/esrg/sfesrg/esrgpcpj/shared/c_datd/crchashfuncs.h,v 1.3 2001/07/26 21:41:21 dtashley Exp $")
#endif

// $Log: crchashfuncs.h,v $
// Revision 1.3  2001/07/26 21:41:21  dtashley
// Completion of CRC32 utility, and the CRCHASHFUNCS module.
//
// Revision 1.2  2001/07/26 05:01:49  dtashley
// Keyword expansion corrected.
//
// End of CRCHASHFUNCS.H.