Android增量更新和签名校验

sorunme 8年前
   <h3>1. 概述</h3>    <p>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, <strong>这次我会一步一步来实现</strong> 。</p>    <p>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。</p>    <h3>2. 下载生成AS的.so库</h3>    <p>1.下载整合bsdiff和bzip2</p>    <p>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。</p>    <p style="text-align:center"><img src="https://simg.open-open.com/show/f774697b814647afe9eca6e9f894497d.png"></p>    <p>bsdiff解压后.png</p>    <p>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。</p>    <p style="text-align:center"><img src="https://simg.open-open.com/show/128dddbbe454668d14b9fc5ebb576e06.png"></p>    <p>bsdiff和bzip2整合.png</p>    <p>2.生成AS的.so库</p>    <p>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:</p>    <pre>  <code class="language-java">#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);  }</code></pre>    <p>3.下载差分包合并校验</p>    <p>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。</p>    <pre>  <code class="language-java">/**       * 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;      }</code></pre>    <p>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。</p>    <pre>  <code class="language-java">/*       * 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);      }</code></pre>    <p>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:</p>    <pre>  <code class="language-java">/**       * 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);          }      }</code></pre>    <h3>3. 生成服务端.dll动态库</h3>    <p>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。</p>    <pre>  <code class="language-java">#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);    }</code></pre>    <p>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。</p>    <p> </p>    <p> </p>    <p>来自:http://www.jianshu.com/p/4132834b7fe7</p>    <p> </p>