/*-

 * 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;

}

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