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/*-
 * 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/bspatch/bspatch.c,v 1.1 2005/08/06 01:59:06 cperciva Exp $");
#endif

#include <bzlib.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <err.h>
#include <unistd.h>
#include <fcntl.h>

static off_t offtin(u_char *buf)
{
        off_t y;

        y=buf[7]&0x7F;
        y=y*256;y+=buf[6];
        y=y*256;y+=buf[5];
        y=y*256;y+=buf[4];
        y=y*256;y+=buf[3];
        y=y*256;y+=buf[2];
        y=y*256;y+=buf[1];
        y=y*256;y+=buf[0];

        if(buf[7]&0x80) y=-y;

        return y;
}

int main(int argc,char * argv[])
{
        FILE * f, * cpf, * dpf, * epf;
        BZFILE * cpfbz2, * dpfbz2, * epfbz2;
        int cbz2err, dbz2err, ebz2err;
        int fd;
        ssize_t oldsize,newsize;
        ssize_t bzctrllen,bzdatalen;
        u_char header[32],buf[8];
        u_char *old, *new;
        off_t oldpos,newpos;
        off_t ctrl[3];
        off_t lenread;
        off_t i;

        if(argc!=4) errx(1,"usage: %s oldfile newfile patchfile\n",argv[0]);

        /* Open patch file */
        if ((f = fopen(argv[3], "r")) == NULL)
                err(1, "fopen(%s)", argv[3]);

        /*
        File format:
                0       8       "BSDIFF40"
                8       8       X
                16      8       Y
                24      8       sizeof(newfile)
                32      X       bzip2(control block)
                32+X    Y       bzip2(diff block)
                32+X+Y  ???     bzip2(extra block)
        with control block a set of triples (x,y,z) meaning "add x bytes
        from oldfile to x bytes from the diff block; copy y bytes from the
        extra block; seek forwards in oldfile by z bytes".
        */


        /* Read header */
        if (fread(header, 1, 32, f) < 32) {
                if (feof(f))
                        errx(1, "Corrupt patch\n");
                err(1, "fread(%s)", argv[3]);
        }

        /* Check for appropriate magic */
        if (memcmp(header, "BSDIFF40", 8) != 0)
                errx(1, "Corrupt patch\n");

        /* Read lengths from header */
        bzctrllen=offtin(header+8);
        bzdatalen=offtin(header+16);
        newsize=offtin(header+24);
        if((bzctrllen<0) || (bzdatalen<0) || (newsize<0))
                errx(1,"Corrupt patch\n");

        /* Close patch file and re-open it via libbzip2 at the right places */
        if (fclose(f))
                err(1, "fclose(%s)", argv[3]);
        if ((cpf = fopen(argv[3], "r")) == NULL)
                err(1, "fopen(%s)", argv[3]);
        if (fseeko(cpf, 32, SEEK_SET))
                err(1, "fseeko(%s, %lld)", argv[3],
                    (long long)32);
        if ((cpfbz2 = BZ2_bzReadOpen(&cbz2err, cpf, 0, 0, NULL, 0)) == NULL)
                errx(1, "BZ2_bzReadOpen, bz2err = %d", cbz2err);
        if ((dpf = fopen(argv[3], "r")) == NULL)
                err(1, "fopen(%s)", argv[3]);
        if (fseeko(dpf, 32 + bzctrllen, SEEK_SET))
                err(1, "fseeko(%s, %lld)", argv[3],
                    (long long)(32 + bzctrllen));
        if ((dpfbz2 = BZ2_bzReadOpen(&dbz2err, dpf, 0, 0, NULL, 0)) == NULL)
                errx(1, "BZ2_bzReadOpen, bz2err = %d", dbz2err);
        if ((epf = fopen(argv[3], "r")) == NULL)
                err(1, "fopen(%s)", argv[3]);
        if (fseeko(epf, 32 + bzctrllen + bzdatalen, SEEK_SET))
                err(1, "fseeko(%s, %lld)", argv[3],
                    (long long)(32 + bzctrllen + bzdatalen));
        if ((epfbz2 = BZ2_bzReadOpen(&ebz2err, epf, 0, 0, NULL, 0)) == NULL)
                errx(1, "BZ2_bzReadOpen, bz2err = %d", ebz2err);

        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((new=malloc(newsize+1))==NULL) err(1,NULL);

        oldpos=0;newpos=0;
        while(newpos<newsize) {
                /* Read control data */
                for(i=0;i<=2;i++) {
                        lenread = BZ2_bzRead(&cbz2err, cpfbz2, buf, 8);
                        if ((lenread < 8) || ((cbz2err != BZ_OK) &&
                            (cbz2err != BZ_STREAM_END)))
                                errx(1, "Corrupt patch\n");
                        ctrl[i]=offtin(buf);
                };

                /* Sanity-check */
                if(newpos+ctrl[0]>newsize)
                        errx(1,"Corrupt patch\n");

                /* Read diff string */
                lenread = BZ2_bzRead(&dbz2err, dpfbz2, new + newpos, ctrl[0]);
                if ((lenread < ctrl[0]) ||
                    ((dbz2err != BZ_OK) && (dbz2err != BZ_STREAM_END)))
                        errx(1, "Corrupt patch\n");

                /* Add old data to diff string */
                for(i=0;i<ctrl[0];i++)
                        if((oldpos+i>=0) && (oldpos+i<oldsize))
                                new[newpos+i]+=old[oldpos+i];

                /* Adjust pointers */
                newpos+=ctrl[0];
                oldpos+=ctrl[0];

                /* Sanity-check */
                if(newpos+ctrl[1]>newsize)
                        errx(1,"Corrupt patch\n");

                /* Read extra string */
                lenread = BZ2_bzRead(&ebz2err, epfbz2, new + newpos, ctrl[1]);
                if ((lenread < ctrl[1]) ||
                    ((ebz2err != BZ_OK) && (ebz2err != BZ_STREAM_END)))
                        errx(1, "Corrupt patch\n");

                /* Adjust pointers */
                newpos+=ctrl[1];
                oldpos+=ctrl[2];
        };

        /* Clean up the bzip2 reads */
        BZ2_bzReadClose(&cbz2err, cpfbz2);
        BZ2_bzReadClose(&dbz2err, dpfbz2);
        BZ2_bzReadClose(&ebz2err, epfbz2);
        if (fclose(cpf) || fclose(dpf) || fclose(epf))
                err(1, "fclose(%s)", argv[3]);

        /* Write the new file */
        if(((fd=open(argv[2],O_CREAT|O_TRUNC|O_WRONLY,0666))<0) ||
                (write(fd,new,newsize)!=newsize) || (close(fd)==-1))
                err(1,"%s",argv[2]);

        free(new);
        free(old);

        return 0;
}