/*-

 * 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

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

			for(i=1;k+i

				if(V[I[k+i]+h]

					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

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

		};

		return;

	};

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

	jj=0;kk=0;

	for(i=start;i

		if(V[I[i]+h]

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

	};

	jj+=start;kk+=jj;

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

	while(i

		if(V[I[i]+h]

			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

		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

	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

	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

	I[0]=oldsize;

	for(i=0;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

			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

}

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

		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

		oldscore=0;

		for(scsc=scan+=len;scan

			len=search(I,req.old,req.oldsize,req.new+scan,req.newsize-scan,

					0,req.oldsize,&pos;;

			for(;scsc

			if((scsc+lastoffset

				(req.old[scsc+lastoffset] == req.new[scsc]))

				oldscore++;

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

				(len>oldscore+8)) break;

			if((scan+lastoffset

				(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

				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

				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

					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

				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;

}

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) ||

		(read(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) ||

		(read(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