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 /* vim:set ts=8 sw=8 sts=8 noet: */

 /*

   bsdiff.c -- Binary patch generator.

   Copyright 2003 Colin Percival

   For the terms under which this work may be distributed, please see

   the adjoining file "LICENSE".

   ChangeLog:

   2005-05-05 - Use the modified header struct from bspatch.h; use 32-bit

                values throughout.

                  --Benjamin Smedberg <benjamin@smedbergs.us>

   2005-05-18 - Use the same CRC algorithm as bzip2, and leverage the CRC table

                provided by libbz2.

                  --Darin Fisher <darin@meer.net>

 */

 #include "bspatch.h"

 #include <stdlib.h>

 #include <stdio.h>

 #include <string.h>

 #include <fcntl.h>

 #include <stdarg.h>

 #ifdef XP_WIN

 #include <io.h>

 #include <winsock2.h>

 #else

 #include <unistd.h>

 #include <arpa/inet.h>

 #define _O_BINARY 0

 #endif

 #undef MIN

 #define MIN(x,y) (((x)<(y)) ? (x) : (y))

 /*---------------------------------------------------------------------------*/

 /* This variable lives in libbz2.  It's declared in bzlib_private.h, so we just

  * declare it here to avoid including that entire header file.

  */

 extern unsigned int BZ2_crc32Table[256];

 static unsigned int

 crc32(const unsigned char *buf, unsigned int len)

 {

 	unsigned int crc = 0xffffffffL;

 	const unsigned char *end = buf + len;

 	for (; buf != end; ++buf)

 		crc = (crc << 8) ^ BZ2_crc32Table[(crc >> 24) ^ *buf];

 	crc = ~crc;

 	return crc;

 }

 /*---------------------------------------------------------------------------*/

 static void

 reporterr(int e, const char *fmt, ...)

 {

 	if (fmt) {

 		va_list args;

 		va_start(args, fmt);

 		vfprintf(stderr, fmt, args);

 		va_end(args);

 	}

 	exit(e);

 }

 static void

 split(int32_t *I,int32_t *V,int32_t start,int32_t len,int32_t h)

 {

 	int32_t i,j,k,x,tmp,jj,kk;

 	if(len<16) {

 		for(k=start;k<start+len;k+=j) {

 			j=1;x=V[I[k]+h];

 			for(i=1;k+i<start+len;i++) {

 				if(V[I[k+i]+h]<x) {

 					x=V[I[k+i]+h];

 					j=0;

 				};

 				if(V[I[k+i]+h]==x) {

 					tmp=I[k+j];I[k+j]=I[k+i];I[k+i]=tmp;

 					j++;

 				};

 			};

 			for(i=0;i<j;i++) V[I[k+i]]=k+j-1;

 			if(j==1) I[k]=-1;

 		};

 		return;

 	};

 	x=V[I[start+len/2]+h];

 	jj=0;kk=0;

 	for(i=start;i<start+len;i++) {

 		if(V[I[i]+h]<x) jj++;

 		if(V[I[i]+h]==x) kk++;

 	};

 	jj+=start;kk+=jj;

 	i=start;j=0;k=0;

 	while(i<jj) {

 		if(V[I[i]+h]<x) {

 			i++;

 		} else if(V[I[i]+h]==x) {

 			tmp=I[i];I[i]=I[jj+j];I[jj+j]=tmp;

 			j++;

 		} else {

 			tmp=I[i];I[i]=I[kk+k];I[kk+k]=tmp;

 			k++;

 		};

 	};

 	while(jj+j<kk) {

 		if(V[I[jj+j]+h]==x) {

 			j++;

 		} else {

 			tmp=I[jj+j];I[jj+j]=I[kk+k];I[kk+k]=tmp;

 			k++;

 		};

 	};

 	if(jj>start) split(I,V,start,jj-start,h);

 	for(i=0;i<kk-jj;i++) V[I[jj+i]]=kk-1;

 	if(jj==kk-1) I[jj]=-1;

 	if(start+len>kk) split(I,V,kk,start+len-kk,h);

 }

 static void

 qsufsort(int32_t *I,int32_t *V,unsigned char *old,int32_t oldsize)

 {

 	int32_t buckets[256];

 	int32_t i,h,len;

 	for(i=0;i<256;i++) buckets[i]=0;

 	for(i=0;i<oldsize;i++) buckets[old[i]]++;

 	for(i=1;i<256;i++) buckets[i]+=buckets[i-1];

 	for(i=255;i>0;i--) buckets[i]=buckets[i-1];

 	buckets[0]=0;

 	for(i=0;i<oldsize;i++) I[++buckets[old[i]]]=i;

 	I[0]=oldsize;

 	for(i=0;i<oldsize;i++) V[i]=buckets[old[i]];

 	V[oldsize]=0;

 	for(i=1;i<256;i++) if(buckets[i]==buckets[i-1]+1) I[buckets[i]]=-1;

 	I[0]=-1;

 	for(h=1;I[0]!=-(oldsize+1);h+=h) {

 		len=0;

 		for(i=0;i<oldsize+1;) {

 			if(I[i]<0) {

 				len-=I[i];

 				i-=I[i];

 			} else {

 				if(len) I[i-len]=-len;

 				len=V[I[i]]+1-i;

 				split(I,V,i,len,h);

 				i+=len;

 				len=0;

 			};

 		};

 		if(len) I[i-len]=-len;

 	};

 	for(i=0;i<oldsize+1;i++) I[V[i]]=i;

 }

 static int32_t

 matchlen(unsigned char *old,int32_t oldsize,unsigned char *newbuf,int32_t newsize)

 {

 	int32_t i;

 	for(i=0;(i<oldsize)&&(i<newsize);i++)

 		if(old[i]!=newbuf[i]) break;

 	return i;

 }

 static int32_t

 search(int32_t *I,unsigned char *old,int32_t oldsize,

        unsigned char *newbuf,int32_t newsize,int32_t st,int32_t en,int32_t *pos)

 {

 	int32_t x,y;

 	if(en-st<2) {

 		x=matchlen(old+I[st],oldsize-I[st],newbuf,newsize);

 		y=matchlen(old+I[en],oldsize-I[en],newbuf,newsize);

 		if(x>y) {

 			*pos=I[st];

 			return x;

 		} else {

 			*pos=I[en];

 			return y;

 		}

 	};

 	x=st+(en-st)/2;

 	if(memcmp(old+I[x],newbuf,MIN(oldsize-I[x],newsize))<0) {

 		return search(I,old,oldsize,newbuf,newsize,x,en,pos);

 	} else {

 		return search(I,old,oldsize,newbuf,newsize,st,x,pos);

 	};

 }

 int main(int argc,char *argv[])

 {

 	int fd;

 	unsigned char *old,*newbuf;

 	int32_t oldsize,newsize;

 	int32_t *I,*V;

 	int32_t scan,pos,len;

 	int32_t lastscan,lastpos,lastoffset;

 	int32_t oldscore,scsc;

 	int32_t s,Sf,lenf,Sb,lenb;

 	int32_t overlap,Ss,lens;

 	int32_t i;

 	int32_t dblen,eblen;

 	unsigned char *db,*eb;

 	unsigned int scrc;

 	MBSPatchHeader header = {

 		{'M','B','D','I','F','F','1','0'},

 		0, 0, 0, 0, 0, 0

 	};

 	uint32_t numtriples;

 	if(argc!=4)

 		reporterr(1,"usage: %s <oldfile> <newfile> <patchfile>\n",argv[0]);

 	/* Allocate oldsize+1 bytes instead of oldsize bytes to ensure

 		that we never try to malloc(0) and get a NULL pointer */

 	if(((fd=open(argv[1],O_RDONLY|_O_BINARY,0))<0) ||

 		((oldsize=lseek(fd,0,SEEK_END))==-1) ||

 		((old=(unsigned char*) malloc(oldsize+1))==NULL) ||

 		(lseek(fd,0,SEEK_SET)!=0) ||

 		(read(fd,old,oldsize)!=oldsize) ||

 		(close(fd)==-1))

 		reporterr(1,"%s\n",argv[1]);

 	scrc = crc32(old, oldsize);

 	if(((I=(int32_t*) malloc((oldsize+1)*sizeof(int32_t)))==NULL) ||

 		((V=(int32_t*) malloc((oldsize+1)*sizeof(int32_t)))==NULL))

 		reporterr(1,NULL);

 	qsufsort(I,V,old,oldsize);

 	free(V);

 	/* Allocate newsize+1 bytes instead of newsize bytes to ensure

 		that we never try to malloc(0) and get a NULL pointer */

 	if(((fd=open(argv[2],O_RDONLY|_O_BINARY,0))<0) ||

 		((newsize=lseek(fd,0,SEEK_END))==-1) ||

 		((newbuf=(unsigned char*) malloc(newsize+1))==NULL) ||

 		(lseek(fd,0,SEEK_SET)!=0) ||

 		(read(fd,newbuf,newsize)!=newsize) ||

 		(close(fd)==-1)) reporterr(1,"%s\n",argv[2]);

 	if(((db=(unsigned char*) malloc(newsize+1))==NULL) ||

 		((eb=(unsigned char*) malloc(newsize+1))==NULL))

 		reporterr(1,NULL);

 	dblen=0;

 	eblen=0;

 	if((fd=open(argv[3],O_CREAT|O_TRUNC|O_WRONLY|_O_BINARY,0666))<0)

 		reporterr(1,"%s\n",argv[3]);

 	/* start writing here */

 	/* We don't know the lengths yet, so we will write the header again

 		 at the end */

 	if(write(fd,&header,sizeof(MBSPatchHeader))!=sizeof(MBSPatchHeader))

 		reporterr(1,"%s\n",argv[3]);

 	scan=0;len=0;

 	lastscan=0;lastpos=0;lastoffset=0;

 	numtriples = 0;

 	while(scan<newsize) {

 		oldscore=0;

 		for(scsc=scan+=len;scan<newsize;scan++) {

 			len=search(I,old,oldsize,newbuf+scan,newsize-scan,

 					0,oldsize,&pos);

 			for(;scsc<scan+len;scsc++)

 			if((scsc+lastoffset<oldsize) &&

 				(old[scsc+lastoffset] == newbuf[scsc]))

 				oldscore++;

 			if(((len==oldscore) && (len!=0)) || 

 				(len>oldscore+8)) break;

 			if((scan+lastoffset<oldsize) &&

 				(old[scan+lastoffset] == newbuf[scan]))

 				oldscore--;

 		};

 		if((len!=oldscore) || (scan==newsize)) {

 			MBSPatchTriple triple;

 			s=0;Sf=0;lenf=0;

 			for(i=0;(lastscan+i<scan)&&(lastpos+i<oldsize);) {

 				if(old[lastpos+i]==newbuf[lastscan+i]) s++;

 				i++;

 				if(s*2-i>Sf*2-lenf) { Sf=s; lenf=i; };

 			};

 			lenb=0;

 			if(scan<newsize) {

 				s=0;Sb=0;

 				for(i=1;(scan>=lastscan+i)&&(pos>=i);i++) {

 					if(old[pos-i]==newbuf[scan-i]) s++;

 					if(s*2-i>Sb*2-lenb) { Sb=s; lenb=i; };

 				};

 			};

 			if(lastscan+lenf>scan-lenb) {

 				overlap=(lastscan+lenf)-(scan-lenb);

 				s=0;Ss=0;lens=0;

 				for(i=0;i<overlap;i++) {

 					if(newbuf[lastscan+lenf-overlap+i]==

 					   old[lastpos+lenf-overlap+i]) s++;

 					if(newbuf[scan-lenb+i]==

 					   old[pos-lenb+i]) s--;

 					if(s>Ss) { Ss=s; lens=i+1; };

 				};

 				lenf+=lens-overlap;

 				lenb-=lens;

 			};

 			for(i=0;i<lenf;i++)

 				db[dblen+i]=newbuf[lastscan+i]-old[lastpos+i];

 			for(i=0;i<(scan-lenb)-(lastscan+lenf);i++)

 				eb[eblen+i]=newbuf[lastscan+lenf+i];

 			dblen+=lenf;

 			eblen+=(scan-lenb)-(lastscan+lenf);

 			triple.x = htonl(lenf);

 			triple.y = htonl((scan-lenb)-(lastscan+lenf));

 			triple.z = htonl((pos-lenb)-(lastpos+lenf));

 			if (write(fd,&triple,sizeof(triple)) != sizeof(triple))

 				reporterr(1,NULL);

 #ifdef DEBUG_bsmedberg

 			printf("Writing a block:\n"

 			       "	X: %u\n"

 			       "	Y: %u\n"

 			       "	Z: %i\n",

 			       (uint32_t) lenf,

 			       (uint32_t) ((scan-lenb)-(lastscan+lenf)),

 			       (uint32_t) ((pos-lenb)-(lastpos+lenf)));

 #endif

 			++numtriples;

 			lastscan=scan-lenb;

 			lastpos=pos-lenb;

 			lastoffset=pos-scan;

 		};

 	};

 	if(write(fd,db,dblen)!=dblen)

 		reporterr(1,NULL);

 	if(write(fd,eb,eblen)!=eblen)

 		reporterr(1,NULL);

 	header.slen	= htonl(oldsize);

 	header.scrc32	= htonl(scrc);

 	header.dlen	= htonl(newsize);

 	header.cblen	= htonl(numtriples * sizeof(MBSPatchTriple));

 	header.difflen	= htonl(dblen);

 	header.extralen = htonl(eblen);

 	if (lseek(fd,0,SEEK_SET) == -1 ||

 	    write(fd,&header,sizeof(header)) != sizeof(header) ||

 	    close(fd) == -1)

 		reporterr(1,NULL);

 	free(db);

 	free(eb);

 	free(I);

 	free(old);

 	free(newbuf);

 	return 0;

 }