/* crc32.c

   C implementation of CRC-32 checksums for NAACCR records.  Code is based
   upon and utilizes algorithm published by Ross Williams.

   This file contains:
      CRC lookup table
      function CalcCRC32 for calculating CRC-32 checksum
      function AssignCRC32 for assigning CRC-32 in NAACCR record
      function CheckCRC32 for checking CRC-32 in NAACCR record

   Provided by:
      Eric Durbin
      Kentucky Cancer Registry
      University of Kentucky
      October 14, 1998

   Status:
      Public Domain
*/
#include "crc32.h"

/*****************************************************************/
/*                                                               */
/* CRC LOOKUP TABLE                                              */
/* ================                                              */
/* The following CRC lookup table was generated automagically    */
/* by the Rocksoft^tm Model CRC Algorithm Table Generation       */
/* Program V1.0 using the following model parameters:            */
/*                                                               */
/*    Width   : 4 bytes.                                         */
/*    Poly    : 0x04C11DB7L                                      */
/*    Reverse : TRUE.                                            */
/*                                                               */
/* For more information on the Rocksoft^tm Model CRC Algorithm,  */
/* see the document titled "A Painless Guide to CRC Error        */
/* Detection Algorithms" by Ross Williams                        */
/* (ross@guest.adelaide.edu.au.). This document is likely to be  */
/* in the FTP archive "ftp.adelaide.edu.au/pub/rocksoft".        */
/*                                                               */
/*****************************************************************/

unsigned long  crctable[256] =
{
 0x00000000L, 0x77073096L, 0xEE0E612CL, 0x990951BAL,
 0x076DC419L, 0x706AF48FL, 0xE963A535L, 0x9E6495A3L,
 0x0EDB8832L, 0x79DCB8A4L, 0xE0D5E91EL, 0x97D2D988L,
 0x09B64C2BL, 0x7EB17CBDL, 0xE7B82D07L, 0x90BF1D91L,
 0x1DB71064L, 0x6AB020F2L, 0xF3B97148L, 0x84BE41DEL,
 0x1ADAD47DL, 0x6DDDE4EBL, 0xF4D4B551L, 0x83D385C7L,
 0x136C9856L, 0x646BA8C0L, 0xFD62F97AL, 0x8A65C9ECL,
 0x14015C4FL, 0x63066CD9L, 0xFA0F3D63L, 0x8D080DF5L,
 0x3B6E20C8L, 0x4C69105EL, 0xD56041E4L, 0xA2677172L,
 0x3C03E4D1L, 0x4B04D447L, 0xD20D85FDL, 0xA50AB56BL,
 0x35B5A8FAL, 0x42B2986CL, 0xDBBBC9D6L, 0xACBCF940L,
 0x32D86CE3L, 0x45DF5C75L, 0xDCD60DCFL, 0xABD13D59L,
 0x26D930ACL, 0x51DE003AL, 0xC8D75180L, 0xBFD06116L,
 0x21B4F4B5L, 0x56B3C423L, 0xCFBA9599L, 0xB8BDA50FL,
 0x2802B89EL, 0x5F058808L, 0xC60CD9B2L, 0xB10BE924L,
 0x2F6F7C87L, 0x58684C11L, 0xC1611DABL, 0xB6662D3DL,
 0x76DC4190L, 0x01DB7106L, 0x98D220BCL, 0xEFD5102AL,
 0x71B18589L, 0x06B6B51FL, 0x9FBFE4A5L, 0xE8B8D433L,
 0x7807C9A2L, 0x0F00F934L, 0x9609A88EL, 0xE10E9818L,
 0x7F6A0DBBL, 0x086D3D2DL, 0x91646C97L, 0xE6635C01L,
 0x6B6B51F4L, 0x1C6C6162L, 0x856530D8L, 0xF262004EL,
 0x6C0695EDL, 0x1B01A57BL, 0x8208F4C1L, 0xF50FC457L,
 0x65B0D9C6L, 0x12B7E950L, 0x8BBEB8EAL, 0xFCB9887CL,
 0x62DD1DDFL, 0x15DA2D49L, 0x8CD37CF3L, 0xFBD44C65L,
 0x4DB26158L, 0x3AB551CEL, 0xA3BC0074L, 0xD4BB30E2L,
 0x4ADFA541L, 0x3DD895D7L, 0xA4D1C46DL, 0xD3D6F4FBL,
 0x4369E96AL, 0x346ED9FCL, 0xAD678846L, 0xDA60B8D0L,
 0x44042D73L, 0x33031DE5L, 0xAA0A4C5FL, 0xDD0D7CC9L,
 0x5005713CL, 0x270241AAL, 0xBE0B1010L, 0xC90C2086L,
 0x5768B525L, 0x206F85B3L, 0xB966D409L, 0xCE61E49FL,
 0x5EDEF90EL, 0x29D9C998L, 0xB0D09822L, 0xC7D7A8B4L,
 0x59B33D17L, 0x2EB40D81L, 0xB7BD5C3BL, 0xC0BA6CADL,
 0xEDB88320L, 0x9ABFB3B6L, 0x03B6E20CL, 0x74B1D29AL,
 0xEAD54739L, 0x9DD277AFL, 0x04DB2615L, 0x73DC1683L,
 0xE3630B12L, 0x94643B84L, 0x0D6D6A3EL, 0x7A6A5AA8L,
 0xE40ECF0BL, 0x9309FF9DL, 0x0A00AE27L, 0x7D079EB1L,
 0xF00F9344L, 0x8708A3D2L, 0x1E01F268L, 0x6906C2FEL,
 0xF762575DL, 0x806567CBL, 0x196C3671L, 0x6E6B06E7L,
 0xFED41B76L, 0x89D32BE0L, 0x10DA7A5AL, 0x67DD4ACCL,
 0xF9B9DF6FL, 0x8EBEEFF9L, 0x17B7BE43L, 0x60B08ED5L,
 0xD6D6A3E8L, 0xA1D1937EL, 0x38D8C2C4L, 0x4FDFF252L,
 0xD1BB67F1L, 0xA6BC5767L, 0x3FB506DDL, 0x48B2364BL,
 0xD80D2BDAL, 0xAF0A1B4CL, 0x36034AF6L, 0x41047A60L,
 0xDF60EFC3L, 0xA867DF55L, 0x316E8EEFL, 0x4669BE79L,
 0xCB61B38CL, 0xBC66831AL, 0x256FD2A0L, 0x5268E236L,
 0xCC0C7795L, 0xBB0B4703L, 0x220216B9L, 0x5505262FL,
 0xC5BA3BBEL, 0xB2BD0B28L, 0x2BB45A92L, 0x5CB36A04L,
 0xC2D7FFA7L, 0xB5D0CF31L, 0x2CD99E8BL, 0x5BDEAE1DL,
 0x9B64C2B0L, 0xEC63F226L, 0x756AA39CL, 0x026D930AL,
 0x9C0906A9L, 0xEB0E363FL, 0x72076785L, 0x05005713L,
 0x95BF4A82L, 0xE2B87A14L, 0x7BB12BAEL, 0x0CB61B38L,
 0x92D28E9BL, 0xE5D5BE0DL, 0x7CDCEFB7L, 0x0BDBDF21L,
 0x86D3D2D4L, 0xF1D4E242L, 0x68DDB3F8L, 0x1FDA836EL,
 0x81BE16CDL, 0xF6B9265BL, 0x6FB077E1L, 0x18B74777L,
 0x88085AE6L, 0xFF0F6A70L, 0x66063BCAL, 0x11010B5CL,
 0x8F659EFFL, 0xF862AE69L, 0x616BFFD3L, 0x166CCF45L,
 0xA00AE278L, 0xD70DD2EEL, 0x4E048354L, 0x3903B3C2L,
 0xA7672661L, 0xD06016F7L, 0x4969474DL, 0x3E6E77DBL,
 0xAED16A4AL, 0xD9D65ADCL, 0x40DF0B66L, 0x37D83BF0L,
 0xA9BCAE53L, 0xDEBB9EC5L, 0x47B2CF7FL, 0x30B5FFE9L,
 0xBDBDF21CL, 0xCABAC28AL, 0x53B39330L, 0x24B4A3A6L,
 0xBAD03605L, 0xCDD70693L, 0x54DE5729L, 0x23D967BFL,
 0xB3667A2EL, 0xC4614AB8L, 0x5D681B02L, 0x2A6F2B94L,
 0xB40BBE37L, 0xC30C8EA1L, 0x5A05DF1BL, 0x2D02EF8DL
};

/*****************************************************************/
/*                   End of CRC Lookup Table                     */
/*****************************************************************/

/* Calculate CRC-32 Checksum for NAACCR Record,
   skipping area of record containing checksum field.

   Uses reflected table driven method documented by Ross Williams.

   PARAMETERS:
     unsigned char *p           NAACCR Record Buffer
     unsigned long reclen       NAACCR Record Length
     unsigned long checksumpos  Position of CHECKSUM (as in Data Dictionary)
     unsigned long checksumlen  Length of checksum Field

   RETURNS:
         checksum value

   Author:
     Eric Durbin 1998-10-14

   Status:
     Public Domain
*/
unsigned long CalcCRC32(unsigned char *p, unsigned long reclen, unsigned long checksumpos, unsigned long checksumlen)
{
        unsigned long j;

        /* initialize value */
        unsigned long crc = CRC32_XINIT;

        /* process each byte prior to checksum field */
        for (j = 1; j < checksumpos; j++) {
                crc = crctable[(crc ^ *p++) & 0xFFL] ^ (crc >> 8);
        }

        /* skip checksum position */
        j += checksumlen;
        p += checksumlen;

        /* process remaining bytes in record */
        while (j <= reclen) {
                crc = crctable[(crc ^ *p++) & 0xFFL] ^ (crc >> 8);
                j++;
        }

        /* return XOR out value */
        return crc ^ CRC32_XOROT;
}

/* Assign CRC-32 checksum for NAACCR record passed in buffer p of length
   reclen with checksum occupying position checksumpos of length checksumlen.

   PARAMETERS:
     unsigned char *p           NAACCR Record Buffer
     unsigned long reclen       NAACCR Record Length
     unsigned long checksumpos  Position of CHECKSUM (as in Data Dictionary)
     unsigned long checksumlen  Length of checksum Field

   RETURNS:
     0  Checksum successfully placed in checksum field
    -1  Checksum length too short
    -2  Checksum length too long
    -3  Checksum position exceeds record length

    Author:
     Eric Durbin 1998-10-14

   Status:
     Public Domain
*/
int AssignCRC32(unsigned char *p, unsigned long reclen, unsigned long checksumpos, unsigned long checksumlen)
{
        unsigned long CRCValue;              /* value of CRC checksum for record */
        unsigned long Mask = 0x0000000FL;    /* Mask for converting hex string */
        char *HexString ="0123456789ABCDEF"; /* hex string characters */
        unsigned char *s;                    /* string pointer */

        /* validate checksum length */
        if (checksumlen < MINIMUM_CHECKSUM_LEN)
                return -1;
        if (checksumlen > MAXIMUM_CHECKSUM_LEN)
                return -2;
        if (checksumpos > reclen)
                return -3;

        CRCValue = CalcCRC32(p, reclen, checksumpos, checksumlen);

        /* convert CRC Value to ASCII Hex String */
        s = p+checksumpos-1;
        while (checksumlen--) {
                *(s+checksumlen) = *(HexString + (CRCValue & Mask));
                CRCValue >>= 4;  /* right shift 4 bits */
        }
        return 0;
}

/* compare CRC-32 checksum in NAACCR record

   PARAMETERS:
     unsigned char *p           NAACCR Record Buffer
     unsigned long reclen       NAACCR Record Length
     unsigned long checksumpos  Position of CHECKSUM (as in Data Dictionary)
     unsigned long checksumlen  Length of checksum Field

   RETURNS:
     0   Checksum matches
    -1   Checksum mismatch

   Author:
     Eric Durbin 1998-10-14

   Status:
     Public Domain
*/
int CompareCRC32(unsigned char *p, unsigned long reclen, unsigned long checksumpos, unsigned long checksumlen)
{
        unsigned long RecordCRCValue = 0L; /* initialize record's CRC Value */
        unsigned long CalcCRCValue;
        unsigned char *s = p+checksumpos-1;/* incoming checksum string */

        CalcCRCValue = CalcCRC32(p, reclen, checksumpos, checksumlen);

        /* extract records hexadecimal checksum value */
        while (checksumlen--) {
                RecordCRCValue <<= 4;  /* left shift 4 bits */
                RecordCRCValue += (*s>'9') ? *s++-'A'+10 : *s++-'0';
        }

        /* compare values */
        if (RecordCRCValue != CalcCRCValue)
                return -1;
        return 0;
}
