Yenc encoder en C

// Created by Juergen Helbing in 2001 as a part of the MyNews project 

// This is a source code example for the yEncoder - see also:  http://www.yenc.org
// It is public domain - as well as the yEnc specification
//
// The progamming style is very "basic" and readable.
//
// The function is writing a binary source file (fSrc) to an encoded target file (fDes).
// The original filename is "postname"
// The size of the sourcefile is "filelen"
// For singlepart messages 'part' 'lastpart' and 'fulllen' are set to zero.

// For multipart:
// Set "part" to 1..lastpart
// "fulllen" is the size of the entire sourcefile
// "filelen" is the size of the part which is actually encoded.

// print() and eprint() are logging displays from 'MyNews'
// Crc32 - functions avbailable at the end of this example


int yEncode(FILE * fDes, char * postname, FILE * fSrc, long filelen,int part,int lastpart,long fulllen)
	{
	long restlen;
	long srclen;
	long deslen;
	unsigned char srcbuf[4100];
	unsigned char desbuf[260];
	unsigned char * srcp;
	unsigned char * desp;
	unsigned char c;
	int id;
	int linelength;
	static long pbegin, pend;

	print("yEncode (%ld bytes)\r\n",filelen);

	linelength=128;  // max 255 - due to desbuf size

	if (part==0)  // SinglePart message
		{
		fprintf(fDes,"=ybegin line=%ld size=%ld name=%s\r\n",linelength,filelen,postname);
		}
	else          // Multipart message
		{

		if (part==1) { pbegin=1; pend=filelen; }
		else         { pbegin=pend+1; pend=pend+filelen; };

		fprintf(fDes,"=ybegin part=%d line=%ld size=%ld name=%s\r\n",part,linelength,fulllen,postname);
		fprintf(fDes,"=ypart begin=%ld end=%ld\r\n",pbegin,pend);
		}

	CrcInit();

	deslen=0; desp=desbuf; restlen=filelen;
	while (restlen>0)
		{
		srclen=restlen;
		if (srclen>4096) srclen=4096;
		id=fread(srcbuf,srclen,1,fSrc);
		if (id != 1)
			{
			eprint("Error in reading file for encoding (code=%d)\r\n",errno);
			return(1);
			}
		restlen=restlen-srclen;
		srcp=srcbuf;

		while (srclen>0)
			{

			c=*srcp;                    // Get a source byte
			CrcAdd(c);                  // Add it to the CRC
			c=(unsigned char) (c+42);   // and add the secret number
			srcp++; srclen--;
			switch (c)  // Solve special in NNTP 'forbidden' characters
				{
			case 0:
			case 9:
			case 10:
			case 13:
			case '=':   // Including the escape character itself
			case '.':   // Some usual servers have problems with a dot in the first column
				*desp='='; desp++; deslen++;
				c=(unsigned char)(c+64);
				}
			*desp=c; desp++; deslen++;
			if ((deslen>=linelength)|((srclen==0)&(restlen==0))) // Block full - or end of file
				{
				*desp=13; desp++; deslen++;
				*desp=10; deslen++;
				id=fwrite(desbuf,deslen,1,fDes);
				if (id!=1)
					{
					eprint("Error in writing encoded file (code=%d)\r\n",errno);
					return(1);
					}
				deslen=0; desp=desbuf;
				}
			}  // end of while (srclen > 0)

		}	// end of while (restlen > 0)

	if (part==0)   // Single part message
		{
		fprintf(fDes,"=yend size=%ld crc32=%08lx \r\n",filelen,crc_val ^ 0xFFFFFFFF);
		}
	else           // Multipart message
		{
		// This does not yet support the full crc32 for the entire file
		fprintf(fDes,"=yend size=%ld part=%d pcrc32=%08lx \r\n",filelen,part,crc_val ^ 0xFFFFFFFF);
		}
	if (part==lastpart) print("Last part encoded\r\n"); // Only dummy
	return(0);
	}






int crc_tab[256] =

{
	0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3,
	0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91,
	0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
	0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5,
	0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
	0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
	0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
	0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d,
	0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
	0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
	0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457,
	0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
	0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb,
	0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
	0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
	0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad,
	0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683,
	0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
	0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7,
	0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
	0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
	0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79,
	0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f,
	0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
	0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
	0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21,
	0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
	0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,
	0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db,
	0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
	0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf,
	0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
}
;

int crc_val;
long crc_anz;

void CrcInit()
	  {
	  crc_val = -1L ;
	  crc_anz=0L;
	  }



void CrcAdd(int c)
	{
	unsigned long ch1,ch2,cc;


	  /* X^32+X^26+X^23+X^22+X^16+X^12+X^11+X^10+X^8+X^7+X^5+X^4+X^2+X^1+X^0 */
	  /* for (i = 0; i < size; i++) */
	  /*      crccode = crc32Tab[(int) ((crccode) ^ (buf[i])) & 0xff] ^  */
	  /*                (((crccode) >> 8) & 0x00FFFFFFL); */
	  /*   return(crccode); */


	 cc= (c) & 0x000000ffL;
	 ch1=(crc_val ^ cc) & 0xffL;
	 ch1=crc_tab[ch1];
	 ch2=(crc_val>>8L) & 0xffffffL;  // Correct version
	 crc_val=ch1 ^ ch2;
	 crc_anz++;
	}