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/tibib/article/details/8504680

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   X16  8   Y24  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 bytesfrom oldfile to x bytes from the diff block; copy y bytes from theextra 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

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