Android增量更新和签名校验

来源：互联网发布：秦柯 python 编辑：程序博客网时间：2024/05/21 14:03

1. 概述

　　NDK图片压缩有很多人反应是蒙的，包括在文章评论的一些哥们，也包括私下聊天的一些哥们。那么内涵段子后面的所有分享都离不开NDK，比如gif图片加载，视频压缩，视频直播推流等等。当然我们也可以去网上下载别人写好的，但是对于我们来说没任何意义。经过后来一系列的考虑，内涵段子项目暂时告一个段落。希望后面有时间出一些C和C++的语法基础，然后我们再来实现后面的功能，这期是现阶段最后一次分享NDK了，这次我会一步一步来实现。
　　每次演示我记得我都下载的是内涵段子6.0.1的版本，但是每到周末就发现更新到了最新的版本，在我的印象里我从来都没有去更新过，那么到底是怎么回事？有些应用弹出更新我一般是拒绝的，因为我需要下载几十M的apk要等太久，没耐心。而增量更新就解决了这个问题，我们更新版本不需要全部下载最新版的apk，而只需要下载一个几M甚至更小的差分包，就能完成更新了。网上这方面的资料也比较多大家可以多看看别人写的文章。
　　

2. 下载C库生成AS的.so库

1.下载整合bsdiff和bzip2

　　百度搜索bsdiff目前最新版本是4.3，点击here就可以下载了。文件只有5KB，里面有两个文件很重要bsdiff.c和bspatch.c，一个用来生成差分包一个用来合并差分包。

bsdiff解压后.png
　　
　　打开.c源码瞧瞧，里面还需要我们下载bzip2，百度搜索bzip2,点击1.0.6 source tarball就可以下载了。这个文件就有点大了，我们把里面的.h和.c文件拷贝出来整合到bsdiff里面。

bsdiff和bzip2整合.png

2.生成AS的.so库

　　把整合好的所有文件都copy到项目的jni目录下面就可以开始写代码了：

#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.c"#include "crctable.c"#include "compress.c"#include "decompress.c"#include "randtable.c"#include "blocksort.c"#include "huffman.c"#include <stdlib.h>#include <stdio.h>#include <string.h>#include <err.h>#include <unistd.h>#include <fcntl.h>#include "com_darren_util_PatchUtils.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 combine(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;}// 合并差分包JNIEXPORT void JNICALL Java_com_darren_util_PatchUtils_combine(JNIEnv *env, jclass jclz, jstring old_apk_path, jstring new_apk_path, jstring patch_path){    // 固定参数 4    int argc = 4;    // 转换 jstring -> char*    char* old_apk_cstr = (char*)(*env)->GetStringUTFChars(env,old_apk_path,NULL);    char* new_apk_cstr = (char*)(*env)->GetStringUTFChars(env,new_apk_path,NULL);    char* patch_path_cstr = (char*)(*env)->GetStringUTFChars(env,patch_path,NULL);    // 赋值    char * argv[4];    argv[0] = "combine";    argv[1] = old_apk_cstr;    argv[2] = new_apk_cstr;    argv[3] = patch_path_cstr;    // 调用合并方法    patch(argc,argv);    // 释放资源    (*env)->ReleaseStringUTFChars(env,old_apk_path,old_apk_cstr);    (*env)->ReleaseStringUTFChars(env,new_apk_path,new_apk_cstr);    (*env)->ReleaseStringUTFChars(env,patch_path,patch_path_cstr);}

3.下载差分包合并校验

　　假设目前我们手机上面是安装的内涵段子1.0的版本，服务器上面已经有了2.0的版本，那么现在我们只需要下载差分包就好，然后调用已经写好的.so的方法生成2.0的版本，校验签名即可安装。

     /**     * 获取当前apk的签名     * @param context     * @return     */    public static String getSignature(Context context){        // 通过Context获取当前包名        String currentApkPackageName = context.getApplicationInfo().packageName;        Log.e(TAG,"TAG -> "+currentApkPackageName);        // 通过PackageManager获取所有应用的PackageInfo信息        PackageManager packageManager = context.getPackageManager();        List<PackageInfo> packageInfos = packageManager.getInstalledPackages(PackageManager.GET_SIGNATURES);        for (PackageInfo packageInfo : packageInfos) {            if(packageInfo.packageName.equals(currentApkPackageName)){                // 获取签名                return packageInfo.signatures[0].toCharsString();            }        }        return null;    }

　　获取某个路径下的apk签名，这个倒是真的把我难住了。某些哥们就立马来灵感了，百度啊，可是早在几年前那个时候网上很少找得到答案。况且网上找的解决方案也大多存在版本兼容问题，不过还好系统应用里面不是有签名校验吗？我们可以把系统应用的源码拿出来看看，看它是怎么校验签名的又或者说是怎么获取PackageInfo的。

    /*     * Utility method to get application information for a given packageURI     */    public static  ApplicationInfo getApplicationInfo(Uri packageURI) {        final String archiveFilePath = packageURI.getPath();        PackageParser packageParser = new PackageParser(archiveFilePath);        File sourceFile = new File(archiveFilePath);        DisplayMetrics metrics = new DisplayMetrics();        metrics.setToDefaults();        PackageParser.Package pkg = packageParser.parsePackage(sourceFile, archiveFilePath, metrics, 0);        if (pkg == null) {            return null;        }        return pkg.applicationInfo;    }    /*     * Utility method to get package information for a given packageURI     */    public static  PackageParser.Package getPackageInfo(Uri packageURI) {        final String archiveFilePath = packageURI.getPath();        PackageParser packageParser = new PackageParser(archiveFilePath);        File sourceFile = new File(archiveFilePath);        DisplayMetrics metrics = new DisplayMetrics();        metrics.setToDefaults();        return packageParser.parsePackage(sourceFile, archiveFilePath, metrics, 0);    }

　　但是目前还有一个问题PackageParser你根本找不到这个类，这个类被隐藏了。能不能不要这么操蛋，我不校验签名了还不行吗？不校验那出了问题锅得你背，你可以把这个流程去掉试试。所以硬着头皮用反射吧：

     /**     * 获取该目录下的apk签名     * @param path 当前apk路径     * @return     */    public static String getSignature(String path) throws Exception{        // 1.反射实例化PackageParser对象        Object packageParser = getPackageParser(path);        // 2.反射获取parsePackage方法        Object packageObject = getPackageInfo(path,packageParser);        // 3.调用collectCertificates方法        Method collectCertificatesMethod = packageParser.getClass().                getDeclaredMethod("collectCertificates",packageObject.getClass(),int.class);        collectCertificatesMethod.invoke(packageParser,packageObject,0);        // 4.获取mSignatures属性        Field signaturesField = packageObject.getClass().getDeclaredField("mSignatures");        signaturesField.setAccessible(true);        Signature[] mSignatures = (Signature[]) signaturesField.get(packageObject);        return mSignatures[0].toCharsString();    }    /**     * 创建PackageParser.Package类，兼容5.0     * @param path     * @return     * @throws Exception     */    private static Object getPackageInfo(String path, Object packageParser) throws Exception {        if(Build.VERSION.SDK_INT >=21){            Class<?>[] paramClass = new Class[2];            paramClass[0] = File.class;            paramClass[1] = int.class;            Method parsePackageMethod = packageParser.getClass().getDeclaredMethod("parsePackage",paramClass);            // 3.反射执行parsePackage方法            Object[] paramObject = new Object[2];            paramObject[0] = new File(path);            paramObject[1] = 0;            parsePackageMethod.setAccessible(true);            return parsePackageMethod.invoke(packageParser,paramObject);        }else{            Class<?>[] paramClass = new Class[4];            paramClass[0] = File.class;            paramClass[1] = String.class;            paramClass[2] = DisplayMetrics.class;            paramClass[3] = int.class;            Method parsePackageMethod = packageParser.getClass().getDeclaredMethod("parsePackage",paramClass);            // 3.反射执行parsePackage方法            Object[] paramObject = new Object[4];            paramObject[0] = new File(path);            paramObject[1] = path;            DisplayMetrics metrics = new DisplayMetrics();            metrics.setToDefaults();            paramObject[2] = metrics;            paramObject[3] = 0;            parsePackageMethod.setAccessible(true);            return parsePackageMethod.invoke(packageParser,paramObject);        }    }    /**     * 创建PackageParser类     * @param path     * @return     * @throws Exception     */    private static Object getPackageParser(String path) throws Exception{        Class<?> packageParserClazz = Class.forName("android.content.pm.PackageParser");        // 版本兼容        if(Build.VERSION.SDK_INT >=21 ){            Constructor<?> packageParserConstructor = packageParserClazz.getDeclaredConstructor();            return packageParserConstructor.newInstance();        }else{            Constructor<?> packageParserConstructor = packageParserClazz.getDeclaredConstructor(String.class);            return packageParserConstructor.newInstance(path);        }    }

3. 生成服务端.dll动态库

　　好不容测试没问题了，高高兴兴的打算去提交申请单。可是需要后台协助的时候说我根本不会生成dll动态库，好说歹说都不行，直接对你说你行你来啊，所以也只能自己来了。

#include <stdlib.h>#include "bzlib.h"#include <stdio.h>#include <string.h>//#include <err.h>//#include <unistd.h>#include <io.h>#include <fcntl.h>//#include <sys/wait.h>#include "com_hc_diff_BSDiff.h"#include <windows.h>#include <process.h>#include <sys/types.h>typedef unsigned char u_char;typedef long pid_t;template<class T>void err(int i, const char* str, T arg) {    char lastErrorTxt[1024];    FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM|FORMAT_MESSAGE_IGNORE_INSERTS,NULL,GetLastError(),0,lastErrorTxt,1024,NULL);    printf("%s",lastErrorTxt);    printf(str, arg);    exit(i);}void err(int i, const char* str) {    char lastErrorTxt[1024];    FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM|FORMAT_MESSAGE_IGNORE_INSERTS,NULL,GetLastError(),0,lastErrorTxt,1024,NULL);    printf("%s",lastErrorTxt);    if (str!=NULL) {        printf("%s",str);    }    exit(i);}template<class T>void errx(int i, const char* str, T arg) {    printf(str, arg);    exit(i);}void errx(int i, const char* str) {    printf("%s",str);    exit(i);}#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 void offtout(off_t x,u_char *buf){    off_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;}int diff(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 dblen,eblen;    u_char *db,*eb;    u_char buf[8];    u_char header[32];    FILE * pf;    BZFILE * pfbz2;    int bz2err;    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 */    //org:    //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]);    //new:    //Read in chunks, don't rely on read always returns full data!    if(((fd=_open(argv[1],O_RDONLY|O_BINARY|O_NOINHERIT,0))<0) ||        ((oldsize=lseek(fd,0,SEEK_END))==-1) ||        ((old=(u_char*)malloc(oldsize+1))==NULL) ||        (_lseek(fd,0,SEEK_SET)!=0))                err(1,"%s",argv[1]);    int r=oldsize;    while (r>0 && (i=read(fd,old+oldsize-r,r))>0) r-=i;    if (r>0 || close(fd)==-1) err(1,"%s",argv[1]);    if(((I=(off_t*)malloc((oldsize+1)*sizeof(off_t)))==NULL) ||        ((V=(off_t*)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 */    //org:    //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]);    //new:    //Read in chunks, don't rely on read always returns full data!    if(((fd=open(argv[2],O_RDONLY|O_BINARY|O_NOINHERIT,0))<0) ||        ((newsize=lseek(fd,0,SEEK_END))==-1) ||        ((_new=(u_char*)malloc(newsize+1))==NULL) ||        (lseek(fd,0,SEEK_SET)!=0))                err(1,"%s",argv[2]);    r=newsize;    while (r>0 && (i=read(fd,_new+newsize-r,r))>0) r-=i;    if (r>0 || close(fd)==-1) err(1,"%s",argv[1]);    if(((db=(u_char*)malloc(newsize+1))==NULL) ||        ((eb=(u_char*)malloc(newsize+1))==NULL)) err(1,NULL);    dblen=0;    eblen=0;    /* Create the patch file */    //org:    //if ((pf = fopen(argv[3], "w")) == NULL)    //new:    //if((fd=open(argv[3],O_CREAT|O_TRUNC|O_WRONLY|O_BINARY|O_NOINHERIT,0666))<0)    if ((pf = fopen(argv[3], "wb")) == NULL)        err(1,"%s",argv[3]);    /* Header is        0   8    "BSDIFF40"        8   8   length of bzip2ed ctrl block        16  8   length of bzip2ed diff block        24  8   length of new file */    /* File is        0   32  Header        32  ??  Bzip2ed ctrl block        ??  ??  Bzip2ed diff block        ??  ??  Bzip2ed extra block */    memcpy(header,"BSDIFF40",8);    offtout(0, header + 8);    offtout(0, header + 16);    offtout(newsize, header + 24);    if (fwrite(header, 32, 1, pf) != 1)        err(1, "fwrite(%s)", argv[3]);    /* Compute the differences, writing ctrl as we go */    if ((pfbz2 = BZ2_bzWriteOpen(&bz2err, pf, 9, 0, 0)) == NULL)        errx(1, "BZ2_bzWriteOpen, bz2err = %d", bz2err);    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,buf);            BZ2_bzWrite(&bz2err, pfbz2, buf, 8);            if (bz2err != BZ_OK)                errx(1, "BZ2_bzWrite, bz2err = %d", bz2err);            offtout((scan-lenb)-(lastscan+lenf),buf);            BZ2_bzWrite(&bz2err, pfbz2, buf, 8);            if (bz2err != BZ_OK)                errx(1, "BZ2_bzWrite, bz2err = %d", bz2err);            offtout((pos-lenb)-(lastpos+lenf),buf);            BZ2_bzWrite(&bz2err, pfbz2, buf, 8);            if (bz2err != BZ_OK)                errx(1, "BZ2_bzWrite, bz2err = %d", bz2err);            lastscan=scan-lenb;            lastpos=pos-lenb;            lastoffset=pos-scan;        };    };    BZ2_bzWriteClose(&bz2err, pfbz2, 0, NULL, NULL);    if (bz2err != BZ_OK)        errx(1, "BZ2_bzWriteClose, bz2err = %d", bz2err);    /* Compute size of compressed ctrl data */    if ((len = ftell(pf)) == -1)        err(1, "ftello");    offtout(len-32, header + 8);    /* Write compressed diff data */    if ((pfbz2 = BZ2_bzWriteOpen(&bz2err, pf, 9, 0, 0)) == NULL)        errx(1, "BZ2_bzWriteOpen, bz2err = %d", bz2err);    BZ2_bzWrite(&bz2err, pfbz2, db, dblen);    if (bz2err != BZ_OK)        errx(1, "BZ2_bzWrite, bz2err = %d", bz2err);    BZ2_bzWriteClose(&bz2err, pfbz2, 0, NULL, NULL);    if (bz2err != BZ_OK)        errx(1, "BZ2_bzWriteClose, bz2err = %d", bz2err);    /* Compute size of compressed diff data */    if ((newsize = ftell(pf)) == -1)        err(1, "ftello");    offtout(newsize - len, header + 16);    /* Write compressed extra data */    if ((pfbz2 = BZ2_bzWriteOpen(&bz2err, pf, 9, 0, 0)) == NULL)        errx(1, "BZ2_bzWriteOpen, bz2err = %d", bz2err);    BZ2_bzWrite(&bz2err, pfbz2, eb, eblen);    if (bz2err != BZ_OK)        errx(1, "BZ2_bzWrite, bz2err = %d", bz2err);    BZ2_bzWriteClose(&bz2err, pfbz2, 0, NULL, NULL);    if (bz2err != BZ_OK)        errx(1, "BZ2_bzWriteClose, bz2err = %d", bz2err);    /* Seek to the beginning, write the header, and close the file */    if (fseek(pf, 0, SEEK_SET))        err(1, "fseeko");    if (fwrite(header, 32, 1, pf) != 1)        err(1, "fwrite(%s)", argv[3]);    if (fclose(pf))        err(1, "fclose");    /* Free the memory we used */    free(db);    free(eb);    free(I);    free(old);    free(_new);    return 0;}JNIEXPORT void JNICALL Java_com_hc_diff_BSDiff_diff(JNIEnv *env, jclass jclz, jstring new_apk_path, jstring old_apk_path, jstring patch_path){    // 固定为4    int argc = 4;    char *argv[4];    // jstring -> char*    char* new_apk_cstr = (char*)env->GetStringUTFChars(new_apk_path, NULL);    char* old_apk_cstr = (char*)env->GetStringUTFChars(old_apk_path, NULL);    char* patch_path_cstr = (char*)env->GetStringUTFChars(patch_path, NULL);    // 封装参数    argv[0] = "diff";    argv[1] = new_apk_cstr;    argv[2] = old_apk_cstr;    argv[3] = patch_path_cstr;    // 调用生成差分包方法    diff(argc,argv);    // 释放资源    env->ReleaseStringUTFChars(new_apk_path,new_apk_cstr);    env->ReleaseStringUTFChars(old_apk_path, old_apk_cstr);    env->ReleaseStringUTFChars(patch_path, patch_path_cstr);}

　　NDK图片压缩加密上传和增量更新的实现流程差不多，我们都是用的第三方提供好的一些C库文件，然后在他的基础上写了一些调用代码。以后我们自己去编译libgif，webrtc，ffmpeg，fomd也是类似，解决问题的方式很重要而不是过多的关注代码，这是内涵段子最后一篇技术分享的文章了。

所有分享大纲：2017Android进阶之路与你同行

视频讲解地址：http://pan.baidu.com/s/1eR9GoFK

1 0