Android应用增量升级

阅读此文之前请先阅读  http://blog.csdn.net/hmg25/article/details/8100896

何为增量升级，简单说下，当应用版本要更新时通常的做法是重新下载新的版本去覆盖旧版本，但这样有个比较明显缺点，太浪费流量了，尤其是在GPRS模式下。我们能不能只更新新版本增加的内容呢，bsdiff/bzlib2可以帮助我们实现这点。下面介绍下具体的做法

第一、生成旧版和新版的差分比patch文件，可以借助bsdiff开源库windows版本

 bsdiff.exe   ../iReader1.6.2.0(v35).apk   ../iReader1.8.0.1(v40).apk   ../ireader.patch

第二、有了patch文件，我们就可以在Android平台上利用JNI调用bzlib2就可以实现增量升级了。

1、首先要有ndk编译环境，具体怎么搭建详见：http://blog.csdn.net/goodding/article/details/9120507

2、编写本地方法

 //oldapk_filepath：旧版本存储路径   newapk_savepath：生成的新版本要存放的路径  patchpath:差分比文件存放路径
 public native int applyPatchToOldApk(String oldapk_filepath, String newapk_savepath , String patchpath);

3、编写Android.mk配置文件，并把需要的bzlib2源代码文件()拷贝到目录下

 LOCAL_PATH:= $(call my-dir)
 include $(CLEAR_VARS)

 # This is the target being built.
 LOCAL_MODULE:= libBsdiff


 # All of the source files that we will compile.
 # 具体到底需要哪些c代码，没有仔细研究过
 LOCAL_SRC_FILES:= tu_bingbing_bsdiff_BsdiffBusiness.c \
                   bzlib.c \
                   blocksort.c \
                   compress.c \
                   crctable.c \
                   decompress.c \
                   huffman.c \
                   randtable.c \
                   bzip2.c \

 # No static libraries.
 LOCAL_STATIC_LIBRARIES := \
      libbz


 # Also need the JNI headers.
 LOCAL_C_INCLUDES += \
     $(JNI_H_INCLUDE) external/bzip2

 # No special compiler flags.
 LOCAL_CFLAGS +=

 include $(BUILD_SHARED_LIBRARY)

4、实现本地方法

 #include <stdio.h>
 #include "tu_bingbing_bsdiff_BsdiffBusiness.h"

 #include "bzlib_private.h"

 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
 #include <err.h>
 #include <unistd.h>
 #include <fcntl.h>
 #include <android/log.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 applypatch(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;
 }

 // old 升级之前apk包路径
 // new 升级之后apk包路径
 // patch文件，可以用bsdiff工具生成
 // 具体原理可以参看http://blog.csdn.net/hmg25/article/details/8100896
 JNIEXPORT jint JNICALL Java_tu_bingbing_bsdiff_BsdiffBusiness_applyPatchToOldApk(JNIEnv *env,
         jobject obj, jstring old, jstring new , jstring patch){
   int argc=4;
   char * argv[argc];
   argv[0]="bspatch";
   argv[1]=(char*)((*env)->GetStringUTFChars(env,old, 0));
   argv[2]=(char*)((*env)->GetStringUTFChars(env,new, 0));
   argv[3]=(char*)((*env)->GetStringUTFChars(env,patch, 0));

   int ret=applypatch(argc, argv);

    (*env)->ReleaseStringUTFChars(env,old,argv[1]);
    (*env)->ReleaseStringUTFChars(env,new,argv[2]);
    (*env)->ReleaseStringUTFChars(env,patch,argv[3]);
    return ret;
 }

最后 ndk编译，在Android中调用native方法，你会发现在你传入路径下生成了新版本的apk。

DEMO：http://download.csdn.net/detail/tibib/5581905