RN差量更新

作者: 哪吒闹海全靠浪 | 来源:发表于2017-05-22 14:22 被阅读220次

    目前常见的diff工具有bsdiffgoogle-diff-match-patch
    google-diff-match-patch可以参考这篇文章
    这里我是想用bsdiff来实现,主要的思路:

    • 在上传时,服务器使用bsdiff算法将老RN包和新RN包生成一个补丁patch文件,供客户端下载。(这步服务器不好做,可以我们生成好上传)
    • 用户下载patch文件,使用bspatch算法将补丁patch文件和老RN包生成一个新RN包。

    安装

    brew install bsdiff
    

    使用bsdiff生成*.patched补丁文件

    bsdiff /Users/xxx/Desktop/test/hot_old.zip /Users/xxx/Desktop/test/hot_new.zip /Users/xxx/Desktop/test/hot.patched
    

    使用bspatch生成新包文件

    bspatch /Users/javalong/Desktop/test/hot_old.zip /Users/javalong/Desktop/test/hot_new_patch.zip /Users/javalong/Desktop/test/hot.patched
    

    验证生成的新包是否正确,两个md5相同,则生成是正确的

    md5 /Users/xxx/Desktop/test/hot_new.zip
    
    md5 /Users/xxx/Desktop/test/hot_new_patch.zip
    

    iOS上的patch代码实现

    #include "bspatch.h"
    #include <sys/cdefs.h>
    
    #include <bzlib.h>
    #include <stdlib.h>
    #include <stdio.h>
    #include <string.h>
    #include <err.h>
    #include <unistd.h>
    #include <fcntl.h>
    
    typedef unsigned char u_char;
    
    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 beginPatch(const char* oldfile, const char* newfile, const char* patchfile)
    {
        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(patchfile, "r")) == NULL) {
            //        err(1, "fopen(%s)", patchfile);
            return -1;
        }
        
        /*
         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");
            return -1;
        }
        
        /* 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))
            return -1;
        if ((cpf = fopen(patchfile, "r")) == NULL)
            return -1;
        if (fseeko(cpf, 32, SEEK_SET))
            return -1;
        if ((cpfbz2 = BZ2_bzReadOpen(&cbz2err, cpf, 0, 0, NULL, 0)) == NULL)
            return -1;
        if ((dpf = fopen(patchfile, "r")) == NULL)
            return -1;
        if (fseeko(dpf, 32 + bzctrllen, SEEK_SET))
            return -1;
        if ((dpfbz2 = BZ2_bzReadOpen(&dbz2err, dpf, 0, 0, NULL, 0)) == NULL)
            return -1;
        if ((epf = fopen(patchfile, "r")) == NULL)
            return -1;
        if (fseeko(epf, 32 + bzctrllen + bzdatalen, SEEK_SET))
            return -1;
        if ((epfbz2 = BZ2_bzReadOpen(&ebz2err, epf, 0, 0, NULL, 0)) == NULL)
            return -1;
        
        if(((fd=open(oldfile,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",oldfile);
        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)", patchfile);
            return -1;
        }
        
        /* Write the new file */
        if(((fd=open(newfile,O_CREAT|O_TRUNC|O_WRONLY,0666))<0) ||
           (write(fd,new,newsize)!=newsize) || (close(fd)==-1)) {
            err(1,"%s",newfile);
            return -1;
        }
        
        free(new);
        free(old);
        
        return 0;
    }
    

    Android上的patch代码实现

    https://github.com/wangkunlin/Bsdiff-Bspatch/tree/master/Bsdiffwkl
    https://github.com/jinyaqiao1102/Bsdiff-BspatchAndroid
    JNI的使用
    http://m.blog.csdn.net/article/details?id=51476144
    这个让客户端开发实现好了。

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