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goobsdiff.c

/*-
 * Copyright 2003-2005 Colin Percival
 * 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.
 */

#if 0
__FBSDID("$FreeBSD: src/usr.bin/bsdiff/bsdiff/bsdiff.c,v 1.1 2005/08/06 01:59:05 cperciva Exp $");
#endif

#include <sys/types.h>

#include <bzlib.h>
#include <err.h>
#include <fcntl.h>
#include <lzma.h>
#include <openssl/sha.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <zlib.h>

#if defined(__APPLE__)
#include <libkern/OSByteOrder.h>
#define htole64(x) OSSwapHostToLittleInt64(x)
#elif defined(__linux__)
#include <endian.h>
#elif defined(_WIN32) && (defined(_M_IX86) || defined(_M_X64))
#define htole64(x) (x)
#else
#error Provide htole64 for this platform
#endif

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

static void split(off_t *I,off_t *V,off_t start,off_t len,off_t h)
{
      off_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(off_t *I,off_t *V,u_char *old,off_t oldsize)
{
      off_t buckets[256];
      off_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 off_t matchlen(u_char *old,off_t oldsize,u_char *new,off_t newsize)
{
      off_t i;

      for(i=0;(i<oldsize)&&(i<newsize);i++)
            if(old[i]!=new[i]) break;

      return i;
}

static off_t search(off_t *I,u_char *old,off_t oldsize,
            u_char *new,off_t newsize,off_t st,off_t en,off_t *pos)
{
      off_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 inline void offtout(off_t x,u_char *buf)
{
      *((off_t*)buf) = htole64(x);
}

/* zlib provides compress2, which deflates to deflate (zlib) format. This is
 * unfortunately distinct from gzip format in that the headers wrapping the
 * decompressed data are different. gbspatch reads gzip-compressed data using
 * the file-oriented gzread interface, which only supports gzip format.
 * compress2gzip is identical to zlib's compress2 except that it produces gzip
 * output compatible with gzread. This change is achieved by calling
 * deflateInit2 instead of deflateInit and specifying 31 for windowBits;
 * numbers greater than 15 cause the addition of a gzip wrapper. */
static int compress2gzip(Bytef *dest, uLongf *destLen,
                         const Bytef *source, uLong sourceLen, int level)
{
      z_stream stream;
      int err;

      stream.next_in = (Bytef*)source;
      stream.avail_in = (uInt)sourceLen;

      stream.next_out = dest;
      stream.avail_out = (uInt)*destLen;
      if ((uLong)stream.avail_out != *destLen) return Z_BUF_ERROR;

      stream.zalloc = (alloc_func)0;
      stream.zfree = (free_func)0;
      stream.opaque = (voidpf)0;

      err = deflateInit2(&stream,
                         level, Z_DEFLATED, 31, 8, Z_DEFAULT_STRATEGY);
      if (err != Z_OK) return err;

      err = deflate(&stream, Z_FINISH);
      if (err != Z_STREAM_END) {
            deflateEnd(&stream);
            return err == Z_OK ? Z_BUF_ERROR : err;
      }
      *destLen = stream.total_out;

      err = deflateEnd(&stream);
      return err;
}

/* Recompress buf of size buf_len using bzip2 or gzip. The smallest version is
 * used. The original uncompressed variant may be the smallest. Returns a
 * number identifying the encoding, 1 for uncompressed, 2 for bzip2, 3 for
 * gzip, and 4 for xz/lzma2. If the original uncompressed variant is not
 * smallest, it is freed. The caller must free any buf after this function
 * returns. */
static char make_small(u_char **buf, off_t *buf_len)
{
      u_char *source = *buf;
      off_t source_len = *buf_len;
      u_char *bz2, *gz, *lzma;
      unsigned int bz2_len;
      size_t gz_len, lzma_len, lzma_pos;
      int bz2_err, gz_err;
      lzma_ret lzma_err;
      lzma_check lzma_ck;
      char smallest;

      smallest = 1;

      bz2_len = source_len + 1;
      bz2 = malloc(bz2_len);
      bz2_err = BZ2_bzBuffToBuffCompress((char*)bz2, &bz2_len, (char*)source,
                                         source_len, 9, 0, 0);
      if (bz2_err == BZ_OK) {
            if (bz2_len < *buf_len) {
                  smallest = 2;
                  *buf = bz2;
                  *buf_len = bz2_len;
            } else {
                  free(bz2);
                  bz2 = NULL;
            }
      } else if (bz2_err == BZ_OUTBUFF_FULL) {
            free(bz2);
            bz2 = NULL;
      } else {
            errx(1, "BZ2_bzBuffToBuffCompress: %d", bz2_err);
      }

      gz_len = source_len + 1;
      gz = malloc(gz_len);
      gz_err = compress2gzip(gz, &gz_len, source, source_len, 9);
      if (gz_err == Z_OK) {
            if (gz_len < *buf_len) {
                  smallest = 3;
                  *buf = gz;
                  *buf_len = gz_len;
            } else {
                  free(gz);
                  gz = NULL;
            }
      } else if (gz_err == Z_BUF_ERROR) {
            free(gz);
            gz = NULL;
      } else {
            errx(1, "compress2gzip: %d", gz_err);
      }

      lzma_len = source_len + 1;
      lzma = malloc(lzma_len);
      lzma_pos = 0;

      /* Equivalent to the options used by xz -9 -e. */
      lzma_ck = LZMA_CHECK_CRC64;
      if (!lzma_check_is_supported(lzma_ck))
            lzma_ck = LZMA_CHECK_CRC32;
      lzma_err = lzma_easy_buffer_encode(9 | LZMA_PRESET_EXTREME,
                                         lzma_ck, NULL,
                                         source, source_len,
                                         lzma, &lzma_pos, lzma_len);
      if (lzma_err == LZMA_OK) {
            if (lzma_pos < *buf_len) {
                  smallest = 4;
                  *buf = lzma;
                  *buf_len = lzma_pos;
            } else {
                  free(lzma);
                  lzma = NULL;
            }
      } else if (lzma_err == LZMA_BUF_ERROR) {
            free(lzma);
            lzma = NULL;
      } else {
            errx(1, "lzma_easy_buffer_encode: %d", lzma_err);
      }

      if (smallest != 1) {
            free(source);
      }

      return smallest;
}

int main(int argc,char *argv[])
{
      int fd;
      u_char *old,*new;
      off_t oldsize,newsize;
      off_t *I,*V;
      off_t scan,pos,len;
      off_t lastscan,lastpos,lastoffset;
      off_t oldscore,scsc;
      off_t s,Sf,lenf,Sb,lenb;
      off_t overlap,Ss,lens;
      off_t i;
      off_t cblen, dblen, eblen;
      u_char *cb, *db, *eb;
      u_char header[96];
      FILE * pf;

      if(argc!=4) errx(1,"usage: %s oldfile newfile patchfile",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]);

      if(((I=malloc((oldsize+1)*sizeof(off_t)))==NULL) ||
            ((V=malloc((oldsize+1)*sizeof(off_t)))==NULL)) err(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,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]);

      if(((cb=malloc(newsize+1))==NULL) ||
            ((db=malloc(newsize+1))==NULL) ||
            ((eb=malloc(newsize+1))==NULL)) err(1,NULL);
      cblen=0;
      dblen=0;
      eblen=0;

      /* Create the patch file */
      if ((pf = fopen(argv[3], "wb")) == NULL)
            err(1, "%s", argv[3]);

      /* File format:
            0     8     "BSDIFF4G"
            8     8     length of compressed control block (x)
            16    8     length of compressed diff block (y)
            24    8     length of compressed extra block (z)
            32    8     length of old file
            40    8     length of new file
            48    20    SHA1 of old file
            68    20    SHA1 of new file
            88    1     encoding of control block
            89    1     encoding of diff block
            90    1     encoding of extra block
            91    5     unused
            96    x     compressed control block
            96+x  y     compressed diff block
            96+x+y      z     compressed extra block
      Encodings are 1 (uncompressed), 2 (bzip2), 3 (gzip), and 4 (xz/lzma2).
      */

      memset(header, 0, sizeof(header));
      if (fwrite(header, sizeof(header), 1, pf) != 1)
            err(1, "fwrite(%s)", argv[3]);
      memcpy(header, "BSDIFF4G", 8);
      offtout(oldsize, header + 32);
      offtout(newsize, header + 40);
      SHA1(old, oldsize, header + 48);
      SHA1(new, newsize, header + 68);

      /* Compute the differences */
      scan=0;len=0;
      lastscan=0;lastpos=0;lastoffset=0;
      while(scan<newsize) {
            oldscore=0;

            for(scsc=scan+=len;scan<newsize;scan++) {
                  len=search(I,old,oldsize,new+scan,newsize-scan,
                              0,oldsize,&pos);

                  for(;scsc<scan+len;scsc++)
                  if((scsc+lastoffset<oldsize) &&
                        (old[scsc+lastoffset] == new[scsc]))
                        oldscore++;

                  if(((len==oldscore) && (len!=0)) || 
                        (len>oldscore+8)) break;

                  if((scan+lastoffset<oldsize) &&
                        (old[scan+lastoffset] == new[scan]))
                        oldscore--;
            };

            if((len!=oldscore) || (scan==newsize)) {
                  s=0;Sf=0;lenf=0;
                  for(i=0;(lastscan+i<scan)&&(lastpos+i<oldsize);) {
                        if(old[lastpos+i]==new[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]==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(new[lastscan+lenf-overlap+i]==
                                 old[lastpos+lenf-overlap+i]) s++;
                              if(new[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]=new[lastscan+i]-old[lastpos+i];
                  for(i=0;i<(scan-lenb)-(lastscan+lenf);i++)
                        eb[eblen+i]=new[lastscan+lenf+i];

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

                  offtout(lenf, cb + cblen);
                  cblen += 8;

                  offtout((scan - lenb) - (lastscan + lenf), cb + cblen);
                  cblen += 8;

                  offtout((pos - lenb) - (lastpos + lenf), cb + cblen);
                  cblen += 8;

                  lastscan=scan-lenb;
                  lastpos=pos-lenb;
                  lastoffset=pos-scan;
            };
      };

      header[88] = make_small(&cb, &cblen);
      header[89] = make_small(&db, &dblen);
      header[90] = make_small(&eb, &eblen);

      if (fwrite(cb, 1, cblen, pf) != cblen)
            err(1, "fwrite");
      if (fwrite(db, 1, dblen, pf) != dblen)
            err(1, "fwrite");
      if (fwrite(eb, 1, eblen, pf) != eblen)
            err(1, "fwrite");

      offtout(cblen, header + 8);
      offtout(dblen, header + 16);
      offtout(eblen, header + 24);

      /* Seek to the beginning, write the header, and close the file */
      if (fseeko(pf, 0, SEEK_SET))
            err(1, "fseeko");
      if (fwrite(header, sizeof(header), 1, pf) != 1)
            err(1, "fwrite(%s)", argv[3]);
      if (fclose(pf))
            err(1, "fclose");

      /* Free the memory we used */
      free(cb);
      free(db);
      free(eb);
      free(I);
      free(old);
      free(new);

      return 0;
}

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