[Bitcollider-commits] CVS: bitcollider/lib ftuuhash.c,1.1,1.2

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Update of /cvsroot/bitcollider/bitcollider/lib
In directory sc8-pr-cvs1:/tmp/cvs-serv1678/lib

Modified Files:
	ftuuhash.c 
Log Message:
base64 fix that should remedy occasional uuhash corruption

Index: ftuuhash.c
===================================================================
RCS file: /cvsroot/bitcollider/bitcollider/lib/ftuuhash.c,v
retrieving revision 1.1
retrieving revision 1.2
diff -C2 -r1.1 -r1.2
*** ftuuhash.c	6 Jul 2002 09:30:15 -0000	1.1
--- ftuuhash.c	18 Mar 2003 08:15:19 -0000	1.2
***************
*** 1,287 ****
! /* (PD) 2001 The Bitzi Corporation
!  * Please see file COPYING or http://bitzi.com/publicdomain 
!  * for more info.
!  *
!  *  $Id$
!  *
!  *  Support for calculating FastTrack internal hashes
!  *
!  *  Based on the definition of the FastTrack hash used
!  *  by the giFT project; reworked to allow calculation
!  *  in one stream pass, rather than with file-seeks and
!  *  a filesize known in advance.
!  *
!  *  FT identifiers are roughly:
!  *  16 bytes: md5 of first 307,200 bytes of file
!  *   4 bytes: result of running a more simple "smallHash"
!  *            over a number of ranges of the file, including:
!  *            
!  *            - the 307,200 bytes starting at each 1MiB, 2MiB, 4MiB,
!  *              8MiB, 16MiB, etc offset within the file
!  * 
!  *            - the last 307,200 bytes of the file (or less
!  *              if the filesize < 614,400)
!  *
!  *            The last 307,200 has precedence over the 307,200
!  *            starting at any sampling point -- so for example,
!  *            in a file that's 1.5 MiB, the range from 1MiB to
!  *            1MiB+307200 is not sampled, because it would overlap
!  *            into the 307,200-long endseg.
!  *
!  *  Since this code does not know the stream's length in advance,
!  *  it uses a big rolling window of file contents, and can rollback
!  *  the smallhash if the end is discovered within 307200 of the
!  *  last sample range end. (Seeding the FTUU_CTX with the file's
!  *  length would obviate the need for that rolling window... 
!  *  probably speeding up the process a lot.)
!  *
!  */
! 
! #include "ftuuhash.h"
! #include "md5.h"
! 
! #include <stdio.h>
! #include <string.h>
! 
! static const unsigned int FTSEG_SIZE = 307200;
! 
! // table from giFT project
! static const unsigned int smalltable[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
! };
! 
! /**
!  * Update the 4-byte running small hash; also from giFT project
!  */
! unsigned int hashSmallHash(byte *data, size_t len, unsigned int hash)
! {
!     unsigned int i;
! 
!     for(i=0;i<len;++i) {
! 	hash = smalltable[data[i] ^ (hash & 0xff)] ^ (hash >> 8);
!     }
! 
!     return hash;
! }
! 
! // dirt simple base64 encoding. caller should ensure out has enough space. 
! // no '=' padding provided, but string is zero-terminated. 
! void bitziEncodeBase64(byte *raw, int len, char *out) {
! 	char  *base64digits = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
! 	int bitsNeeded = 6;
! 	int bitPosition = 7;
! 	int rawIndex = 0;
! 	int strIndex = 0;
! 	int bit = 0;
! 	int digit = 0;
! 
! 	while (rawIndex < len) {
! 		while (bitsNeeded > 0) {
! 			if (bitPosition >= 0) {
! 				bit = (raw[rawIndex]>>bitPosition) & 1;
! 				digit = digit << 1;
! 				digit += bit;
! 				bitsNeeded--;
! 				bitPosition--;
! 			} else {
! 				rawIndex++;
! 				bitPosition=7;
! 				if (rawIndex>len) {
! 					digit = digit << bitsNeeded;
! 					bitsNeeded = 0;
! 				}
! 			}
! 		}
! 		out[strIndex]=base64digits[digit];
! 		digit=0;
! 		bitsNeeded=6;
! 		strIndex++;
! 	}
! 	out[strIndex]=0;
! }
! 
! 
! //
! // stream-based FT hash calculation
! //
! 
! /* FTUUHash initialization. 
!  */
! void FTUUInit(FTUU_CTX *context)                                        /* context */
! {
! 	context->nextPos = 0;
! 	context->smallHash = 0xffffffff;
! 	context->backupSmallHash = 0xffffffff;
! 	MD5Init(&(context->md5context));
! 	context->nextSampleStart = 0x100000;
! }
! 
! /* FTUUHash block update operation. 
!  */
! void FTUUUpdate(FTUU_CTX *context,                                        /* context */
! const unsigned char *input,                                /* input block */
! unsigned int inputLen)                     /* length of input block */
! {
! 	unsigned int firstPart = inputLen;
! 
! 	// first, handle the MD5'd portion of the file
! 	if(context->nextPos < FTSEG_SIZE) {
! 		if((context->nextPos+inputLen)>FTSEG_SIZE) {
! 			// don't overshoot the segsize
! 			firstPart = FTSEG_SIZE - context->nextPos;
! 		}
! 		MD5Update(&(context->md5context),input,firstPart);
! 		context->nextPos += firstPart;
! 		if(firstPart<inputLen) {
! 			// continue with the rest of the input
! 			FTUUUpdate(context,input+firstPart,inputLen-firstPart);
! 		}
! 		return;
! 	}
! 
! 	// OK, we're past the MD5 portion of the file
! 
!     // check for at sampling-range end
! 	if(context->nextPos == (context->nextSampleStart+FTSEG_SIZE) ) {
! 		// the rollingBuffer is loaded with exactly enough data 
! 		// to add a sample to the smallHash
!         context->backupSmallHash = context->smallHash; // save current smallhash state
! 		// through to end...
! 		context->smallHash =
! 			hashSmallHash(context->rollingBuffer + (context->nextPos % FTSEG_SIZE),
! 			                         FTSEG_SIZE - (context->nextPos % FTSEG_SIZE),
! 								     // 0,
! 								     context->smallHash);
! 		// ... and wraparound
! 		context->smallHash =
! 			hashSmallHash(context->rollingBuffer,
! 			                         context->nextPos % FTSEG_SIZE,
! 								     // FTSEG_SIZE - (context->nextPos % FTSEG_SIZE),
! 								     context->smallHash);
! 		// set new sampling startpoint
! 		context->nextSampleStart = context->nextSampleStart << 1;
! 	}
! 
! 	// OK, just move bytes of data from input to the rollingBuffer
! 	// (use smallest of: inputLen, bytes-to-wraparound, bytes-to-sample-end
!     if((context->nextPos + inputLen) > (context->nextSampleStart + FTSEG_SIZE)) 
! 		firstPart = (context->nextSampleStart + FTSEG_SIZE) - context->nextPos;
! 	if(((context->nextPos % FTSEG_SIZE) + firstPart) > FTSEG_SIZE) {
! 		firstPart = FTSEG_SIZE - (context->nextPos % FTSEG_SIZE);
! 	}
! 
!     memcpy(context->rollingBuffer + (context->nextPos % FTSEG_SIZE),
! 		   input,
! 		   firstPart);
!     context->nextPos += firstPart;
! 
! 	if (firstPart<inputLen) {
! 		// continue with the rest of the input
! 		FTUUUpdate(context,input+firstPart,inputLen-firstPart);
!     }
! }
! 
! /* FTUUHash finalization. 
!  *//* message digest *//* context */
! void FTUUFinal(unsigned char digest[20],FTUU_CTX *context)
! {
! 	int continueIndex = 0;
!     // finalize MD5
! 	MD5Final(digest,&(context->md5context));
! 
! 	// decide whether or not to rollback smallhash
! 	if(context->nextPos < ((context->nextSampleStart >> 1) + 2*FTSEG_SIZE)) {
! 		// the last FTSEG_SIZE bytes overlap the last internal sample
! 		// pretend like the last smallHash processing never happened
! 		context->smallHash = context->backupSmallHash;
! 	}
! 
! 	// do the smallHash of the end segment
! 	if(context->nextPos >= 2*FTSEG_SIZE) {
! 		// end segment is a full FTSEG_SIZE
! 		context->smallHash =
! 			hashSmallHash(context->rollingBuffer + (context->nextPos % FTSEG_SIZE),
! 			                         FTSEG_SIZE - (context->nextPos % FTSEG_SIZE),
! 								     // 0,
! 								     context->smallHash);
! 		continueIndex = FTSEG_SIZE - (context->nextPos % FTSEG_SIZE);
! 	}
! 	if(context->nextPos > FTSEG_SIZE) {
! 		// wraparound or do an endseg < FTSEG_SIZE
! 		context->smallHash =
! 			hashSmallHash(context->rollingBuffer,
! 									 context->nextPos % FTSEG_SIZE,
! 									 // continueIndex,
! 									 context->smallHash);
! 	} // else filesize was <= FTSEG_SIZE, no smallHashing of endseg necessary
!     context->smallHash ^= context->nextPos;
!     digest[16] = context->smallHash & 0xff;
!     digest[17] = (context->smallHash >> 8) & 0xff;
!     digest[18] = (context->smallHash >> 16) & 0xff;
!     digest[19] = (context->smallHash >> 24) & 0xff;
! 
! }
! 
--- 1,288 ----
! /* (PD) 2001 The Bitzi Corporation
!  * Please see file COPYING or http://bitzi.com/publicdomain
!  * for more info.
!  *
!  *  $Id$
!  *
!  *  Support for calculating FastTrack internal hashes
!  *
!  *  Based on the definition of the FastTrack hash used
!  *  by the giFT project; reworked to allow calculation
!  *  in one stream pass, rather than with file-seeks and
!  *  a filesize known in advance.
!  *
!  *  FT identifiers are roughly:
!  *  16 bytes: md5 of first 307,200 bytes of file
!  *   4 bytes: result of running a more simple "smallHash"
!  *            over a number of ranges of the file, including:
!  *
!  *            - the 307,200 bytes starting at each 1MiB, 2MiB, 4MiB,
!  *              8MiB, 16MiB, etc offset within the file
!  *
!  *            - the last 307,200 bytes of the file (or less
!  *              if the filesize < 614,400)
!  *
!  *            The last 307,200 has precedence over the 307,200
!  *            starting at any sampling point -- so for example,
!  *            in a file that's 1.5 MiB, the range from 1MiB to
!  *            1MiB+307200 is not sampled, because it would overlap
!  *            into the 307,200-long endseg.
!  *
!  *  Since this code does not know the stream's length in advance,
!  *  it uses a big rolling window of file contents, and can rollback
!  *  the smallhash if the end is discovered within 307200 of the
!  *  last sample range end. (Seeding the FTUU_CTX with the file's
!  *  length would obviate the need for that rolling window...
!  *  probably speeding up the process a lot.)
!  *
!  */
! 
! 
! #include <stdio.h>
! #include <string.h>
! 
! #include "ftuuhash.h"
! #include "md5.h"
! 
! static const unsigned int FTSEG_SIZE = 307200;
! 
! // table from giFT project
! static const unsigned int smalltable[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
! };
! 
! /**
!  * Update the 4-byte running small hash; also from giFT project
!  */
! unsigned int hashSmallHash(byte *data, size_t len, unsigned int hash)
! {
!     unsigned int i;
! 
!     for(i=0;i<len;++i) {
! 	hash = smalltable[data[i] ^ (hash & 0xff)] ^ (hash >> 8);
!     }
! 
!     return hash;
! }
! 
! // dirt simple base64 encoding. caller should ensure out has enough space.
! // no '=' padding provided, but string is zero-terminated.
! void bitziEncodeBase64(byte *raw, int len, char *out) {
! 	char  *base64digits = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
! 	int bitsNeeded = 6;
! 	int bitPosition = 7;
! 	int rawIndex = 0;
! 	int strIndex = 0;
! 	int bit = 0;
! 	int digit = 0;
! 
! 	while (rawIndex < len) {
! 		while (bitsNeeded > 0) {
! 			if (bitPosition >= 0) {
! 				bit = (raw[rawIndex]>>bitPosition) & 1;
! 				digit = digit << 1;
! 				digit += bit;
! 				bitsNeeded--;
! 				bitPosition--;
! 			} else {
! 				rawIndex++;
! 				bitPosition=7;
! 				if (rawIndex==len) {  // we're past the end; zero-pad
! 					digit = digit << bitsNeeded;
! 					bitsNeeded = 0;
! 				}
! 			}
! 		}
! 		out[strIndex]=base64digits[digit];
! 		digit=0;
! 		bitsNeeded=6;
! 		strIndex++;
! 	}
! 	out[strIndex]=0;
! }
! 
! 
! //
! // stream-based FT hash calculation
! //
! 
! /* FTUUHash initialization.
!  */
! void FTUUInit(FTUU_CTX *context)                                        /* context */
! {
! 	context->nextPos = 0;
! 	context->smallHash = 0xffffffff;
! 	context->backupSmallHash = 0xffffffff;
! 	MD5Init(&(context->md5context));
! 	context->nextSampleStart = 0x100000;
! }
! 
! /* FTUUHash block update operation.
!  */
! void FTUUUpdate(FTUU_CTX *context,                                        /* context */
! const unsigned char *input,                                /* input block */
! unsigned int inputLen)                     /* length of input block */
! {
! 	unsigned int firstPart = inputLen;
! 
! 	// first, handle the MD5'd portion of the file
! 	if(context->nextPos < FTSEG_SIZE) {
! 		if((context->nextPos+inputLen)>FTSEG_SIZE) {
! 			// don't overshoot the segsize
! 			firstPart = FTSEG_SIZE - context->nextPos;
! 		}
! 		MD5Update(&(context->md5context),input,firstPart);
! 		context->nextPos += firstPart;
! 		if(firstPart<inputLen) {
! 			// continue with the rest of the input
! 			FTUUUpdate(context,input+firstPart,inputLen-firstPart);
! 		}
! 		return;
! 	}
! 
! 	// OK, we're past the MD5 portion of the file
! 
!     // check for at sampling-range end
! 	if(context->nextPos == (context->nextSampleStart+FTSEG_SIZE) ) {
! 		// the rollingBuffer is loaded with exactly enough data
! 		// to add a sample to the smallHash
!         context->backupSmallHash = context->smallHash; // save current smallhash state
! 		// through to end...
! 		context->smallHash =
! 			hashSmallHash(context->rollingBuffer + (context->nextPos % FTSEG_SIZE),
! 			                         FTSEG_SIZE - (context->nextPos % FTSEG_SIZE),
! 								     // 0,
! 								     context->smallHash);
! 		// ... and wraparound
! 		context->smallHash =
! 			hashSmallHash(context->rollingBuffer,
! 			                         context->nextPos % FTSEG_SIZE,
! 								     // FTSEG_SIZE - (context->nextPos % FTSEG_SIZE),
! 								     context->smallHash);
! 		// set new sampling startpoint
! 		context->nextSampleStart = context->nextSampleStart << 1;
! 	}
! 
! 	// OK, just move bytes of data from input to the rollingBuffer
! 	// (use smallest of: inputLen, bytes-to-wraparound, bytes-to-sample-end
!     if((context->nextPos + inputLen) > (context->nextSampleStart + FTSEG_SIZE))
! 		firstPart = (context->nextSampleStart + FTSEG_SIZE) - context->nextPos;
! 	if(((context->nextPos % FTSEG_SIZE) + firstPart) > FTSEG_SIZE) {
! 		firstPart = FTSEG_SIZE - (context->nextPos % FTSEG_SIZE);
! 	}
! 
!     memcpy(context->rollingBuffer + (context->nextPos % FTSEG_SIZE),
! 		   input,
! 		   firstPart);
!     context->nextPos += firstPart;
! 
! 	if (firstPart<inputLen) {
! 		// continue with the rest of the input
! 		FTUUUpdate(context,input+firstPart,inputLen-firstPart);
!     }
! }
! 
! /* FTUUHash finalization.
!  *//* message digest *//* context */
! void FTUUFinal(unsigned char digest[20],FTUU_CTX *context)
! {
! 	int continueIndex = 0;
!     // finalize MD5
! 	MD5Final(digest,&(context->md5context));
! 
! 	// decide whether or not to rollback smallhash
! 	if(context->nextPos < ((context->nextSampleStart >> 1) + 2*FTSEG_SIZE)) {
! 		// the last FTSEG_SIZE bytes overlap the last internal sample
! 		// pretend like the last smallHash processing never happened
! 		context->smallHash = context->backupSmallHash;
! 	}
! 
! 	// do the smallHash of the end segment
! 	if(context->nextPos >= 2*FTSEG_SIZE) {
! 		// end segment is a full FTSEG_SIZE
! 		context->smallHash =
! 			hashSmallHash(context->rollingBuffer + (context->nextPos % FTSEG_SIZE),
! 			                         FTSEG_SIZE - (context->nextPos % FTSEG_SIZE),
! 								     // 0,
! 								     context->smallHash);
! 		continueIndex = FTSEG_SIZE - (context->nextPos % FTSEG_SIZE);
! 	}
! 	if(context->nextPos > FTSEG_SIZE) {
! 		// wraparound or do an endseg < FTSEG_SIZE
! 		context->smallHash =
! 			hashSmallHash(context->rollingBuffer,
! 									 context->nextPos % FTSEG_SIZE,
! 									 // continueIndex,
! 									 context->smallHash);
! 	} // else filesize was <= FTSEG_SIZE, no smallHashing of endseg necessary
!     context->smallHash ^= context->nextPos;
!     digest[16] = context->smallHash & 0xff;
!     digest[17] = (context->smallHash >> 8) & 0xff;
!     digest[18] = (context->smallHash >> 16) & 0xff;
!     digest[19] = (context->smallHash >> 24) & 0xff;
! 
! }
!