text: /*-
   * Copyright 2003-2005 Colin Percival
   * Copyright 2012 Matthew Endsley
   * All rights reserved
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted providing that the following conditions 
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
   * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
   * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
   * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   * POSSIBILITY OF SUCH DAMAGE.
   */
  
  #include "bsdiff.h"
  
  #include <limits.h>
  #include <string.h>
  
  #define MIN(x,y) (((x)<(y)) ? (x) : (y))
  
  static void split(int64_t *I,int64_t *V,int64_t start,int64_t len,int64_t h)
  {
  	int64_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(int64_t *I,int64_t *V,const uint8_t *old,int64_t oldsize)
  {
  	int64_t buckets[256];
  	int64_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 int64_t matchlen(const uint8_t *old,int64_t oldsize,const uint8_t *new,int64_t newsize)
  {
  	int64_t i;
  
  	for(i=0;(i<oldsize)&&(i<newsize);i++)
  		if(old[i]!=new[i]) break;
  
  	return i;
  }
  
  static int64_t search(const int64_t *I,const uint8_t *old,int64_t oldsize,
  		const uint8_t *new,int64_t newsize,int64_t st,int64_t en,int64_t *pos)
  {
  	int64_t x,y;
  
  	if(en-st<2) {
  		x=matchlen(old+I[st],oldsize-I[st],new,newsize);
  		y=matchlen(old+I[en],oldsize-I[en],new,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],new,MIN(oldsize-I[x],newsize))<0) {
  		return search(I,old,oldsize,new,newsize,x,en,pos);
  	} else {
  		return search(I,old,oldsize,new,newsize,st,x,pos);
  	};
  }
  
  static void offtout(int64_t x,uint8_t *buf)
  {
  	int64_t y;
  
  	if(x<0) y=-x; else y=x;
  
  	buf[0]=y%256;y-=buf[0];
  	y=y/256;buf[1]=y%256;y-=buf[1];
  	y=y/256;buf[2]=y%256;y-=buf[2];
  	y=y/256;buf[3]=y%256;y-=buf[3];
  	y=y/256;buf[4]=y%256;y-=buf[4];
  	y=y/256;buf[5]=y%256;y-=buf[5];
  	y=y/256;buf[6]=y%256;y-=buf[6];
  	y=y/256;buf[7]=y%256;
  
  	if(x<0) buf[7]|=0x80;
  }
  
  static int64_t writedata(struct bsdiff_stream* stream, const void* buffer, int64_t length)
  {
  	int64_t result = 0;
  
  	while (length > 0)
  	{
  		const int smallsize = (int)MIN(length, INT_MAX);
  		const int writeresult = stream->write(stream, buffer, smallsize);
  		if (writeresult == -1)
  		{
  			return -1;
  		}
  
  		result += writeresult;
  		length -= smallsize;
  		buffer = (uint8_t*)buffer + smallsize;
  	}
  
  	return result;
  }
  
  struct bsdiff_request
  {
  	const uint8_t* old;
  	int64_t oldsize;
  	const uint8_t* new;
  	int64_t newsize;
  	struct bsdiff_stream* stream;
  	int64_t *I;
  	uint8_t *buffer;
  };
  
  static int bsdiff_internal(const struct bsdiff_request req)
  {
  	int64_t *I,*V;
  	int64_t scan,pos,len;
  	int64_t lastscan,lastpos,lastoffset;
  	int64_t oldscore,scsc;
  	int64_t s,Sf,lenf,Sb,lenb;
  	int64_t overlap,Ss,lens;
  	int64_t i;
  	uint8_t *buffer;
  	uint8_t buf[8 * 3];
  
  	if((V=req.stream->malloc((req.oldsize+1)*sizeof(int64_t)))==NULL) return -1;
  	I = req.I;
  
  	qsufsort(I,V,req.old,req.oldsize);
  	req.stream->free(V);
  
  	buffer = req.buffer;
  
  	/* Compute the differences, writing ctrl as we go */
  	scan=0;len=0;pos=0;
  	lastscan=0;lastpos=0;lastoffset=0;
  	while(scan<req.newsize) {
  		oldscore=0;
  
  		for(scsc=scan+=len;scan<req.newsize;scan++) {
  			len=search(I,req.old,req.oldsize,req.new+scan,req.newsize-scan,
  					0,req.oldsize,&pos);
  
  			for(;scsc<scan+len;scsc++)
  			if((scsc+lastoffset<req.oldsize) &&
  				(req.old[scsc+lastoffset] == req.new[scsc]))
  				oldscore++;
  
  			if(((len==oldscore) && (len!=0)) || 
  				(len>oldscore+8)) break;
  
  			if((scan+lastoffset<req.oldsize) &&
  				(req.old[scan+lastoffset] == req.new[scan]))
  				oldscore--;
  		};
  
  		if((len!=oldscore) || (scan==req.newsize)) {
  			s=0;Sf=0;lenf=0;
  			for(i=0;(lastscan+i<scan)&&(lastpos+i<req.oldsize);) {
  				if(req.old[lastpos+i]==req.new[lastscan+i]) s++;
  				i++;
  				if(s*2-i>Sf*2-lenf) { Sf=s; lenf=i; };
  			};
  
  			lenb=0;
  			if(scan<req.newsize) {
  				s=0;Sb=0;
  				for(i=1;(scan>=lastscan+i)&&(pos>=i);i++) {
  					if(req.old[pos-i]==req.new[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(req.new[lastscan+lenf-overlap+i]==
  					   req.old[lastpos+lenf-overlap+i]) s++;
  					if(req.new[scan-lenb+i]==
  					   req.old[pos-lenb+i]) s--;
  					if(s>Ss) { Ss=s; lens=i+1; };
  				};
  
  				lenf+=lens-overlap;
  				lenb-=lens;
  			};
  
  			offtout(lenf,buf);
  			offtout((scan-lenb)-(lastscan+lenf),buf+8);
  			offtout((pos-lenb)-(lastpos+lenf),buf+16);
  
  			/* Write control data */
  			if (writedata(req.stream, buf, sizeof(buf)))
  				return -1;
  
  			/* Write diff data */
  			for(i=0;i<lenf;i++)
  				buffer[i]=req.new[lastscan+i]-req.old[lastpos+i];
  			if (writedata(req.stream, buffer, lenf))
  				return -1;
  
  			/* Write extra data */
  			for(i=0;i<(scan-lenb)-(lastscan+lenf);i++)
  				buffer[i]=req.new[lastscan+lenf+i];
  			if (writedata(req.stream, buffer, (scan-lenb)-(lastscan+lenf)))
  				return -1;
  
  			lastscan=scan-lenb;
  			lastpos=pos-lenb;
  			lastoffset=pos-scan;
  		};
  	};
  
  	return 0;
  }
  
  int bsdiff(const uint8_t* old, int64_t oldsize, const uint8_t* new, int64_t newsize, struct bsdiff_stream* stream)
  {
  	int result;
  	struct bsdiff_request req;
  
  	if((req.I=stream->malloc((oldsize+1)*sizeof(int64_t)))==NULL)
  		return -1;
  
  	if((req.buffer=stream->malloc(newsize+1))==NULL)
  	{
  		stream->free(req.I);
  		return -1;
  	}
  
  	req.old = old;
  	req.oldsize = oldsize;
  	req.new = new;
  	req.newsize = newsize;
  	req.stream = stream;
  
  	result = bsdiff_internal(req);
  
  	stream->free(req.buffer);
  	stream->free(req.I);
  
  	return result;
  }
  
  #if defined(BSDIFF_EXECUTABLE)
  
  #include <sys/types.h>
  
  #include <bzlib.h>
  #include <err.h>
  #include <fcntl.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <unistd.h>
  
  static int bz2_write(struct bsdiff_stream* stream, const void* buffer, int size)
  {
  	int bz2err;
  	BZFILE* bz2;
  
  	bz2 = (BZFILE*)stream->opaque;
  	BZ2_bzWrite(&bz2err, bz2, (void*)buffer, size);
  	if (bz2err != BZ_STREAM_END && bz2err != BZ_OK)
  		return -1;
  
  	return 0;
  }
  
  static off_t readFileToBuffer(int fd, uint8_t* buffer, off_t bufferSize)
  {
      off_t bytesRead = 0;
      int ret;
      while (bytesRead < bufferSize)
      {
          ret = read(fd, buffer + bytesRead, bufferSize - bytesRead);
          if (ret > 0)
          {
              bytesRead += ret;
          }
          else
          {
              break;
          }
      }
      return bytesRead;
  }
  
  int main(int argc,char *argv[])
  {
  	int fd;
  	int bz2err;
  	uint8_t *old,*new;
  	off_t oldsize,newsize;
  	uint8_t buf[8];
  	FILE * pf;
  	struct bsdiff_stream stream;
  	BZFILE* bz2;
  
  	memset(&bz2, 0, sizeof(bz2));
  	stream.malloc = malloc;
  	stream.free = free;
  	stream.write = bz2_write;
  
  	if(argc!=4) errx(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,0))<0) ||
  		((oldsize=lseek(fd,0,SEEK_END))==-1) ||
  		((old=malloc(oldsize+1))==NULL) ||
  		(lseek(fd,0,SEEK_SET)!=0) ||
  		(readFileToBuffer(fd,old,oldsize)!=oldsize) ||
  		(close(fd)==-1)) err(1,"%s",argv[1]);
  
  
  	/* 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,0))<0) ||
  		((newsize=lseek(fd,0,SEEK_END))==-1) ||
  		((new=malloc(newsize+1))==NULL) ||
  		(lseek(fd,0,SEEK_SET)!=0) ||
  		(readFileToBuffer(fd,new,newsize)!=newsize) ||
  		(close(fd)==-1)) err(1,"%s",argv[2]);
  
  	/* Create the patch file */
  	if ((pf = fopen(argv[3], "w")) == NULL)
  		err(1, "%s", argv[3]);
  
  	/* Write header (signature+newsize)*/
  	offtout(newsize, buf);
  	if (fwrite("ENDSLEY/BSDIFF43", 16, 1, pf) != 1 ||
  		fwrite(buf, sizeof(buf), 1, pf) != 1)
  		err(1, "Failed to write header");
  
  
  	if (NULL == (bz2 = BZ2_bzWriteOpen(&bz2err, pf, 9, 0, 0)))
  		errx(1, "BZ2_bzWriteOpen, bz2err=%d", bz2err);
  
  	stream.opaque = bz2;
  	if (bsdiff(old, oldsize, new, newsize, &stream))
  		err(1, "bsdiff");
  
  	BZ2_bzWriteClose(&bz2err, bz2, 0, NULL, NULL);
  	if (bz2err != BZ_OK)
  		err(1, "BZ2_bzWriteClose, bz2err=%d", bz2err);
  
  	if (fclose(pf))
  		err(1, "fclose");
  
  	/* Free the memory we used */
  	free(old);
  	free(new);
  
  	return 0;
  }
  
  #endif
  