原文链接

流程

• step1 使用bsdiff生成差异包PATCH.patch
• step2 在手机上合并base包和差异包，生成新版本的安装包
• step3 安装新的安装包

准备

1. bsdiff-4.3 （用于生成差异包，合并新包）
2. bzip2 （bsdiff要使用到）

试验

• step1 解压bsdiff4.3的压缩包
• step2 修改Makefile文件，将.ifndef和.endif缩进，要么无法进行后面的操作

CFLAGS      +=  -O3 -lbz2

PREFIX      ?=  /usr/local
INSTALL_PROGRAM ?=  ${INSTALL} -c -s -m 555
INSTALL_MAN ?=  ${INSTALL} -c -m 444

all:        bsdiff bspatch
bsdiff:     bsdiff.c
bspatch:    bspatch.c

install:
    ${INSTALL_PROGRAM} bsdiff bspatch ${PREFIX}/bin
    .ifndef WITHOUT_MAN
    ${INSTALL_MAN} bsdiff.1 bspatch.1 ${PREFIX}/man/man1
    .endif

• step3 在该文件夹的命令行里执行make命令，会生成bsdiff和bspatch两个可执行的文件。如果是从上面的地址下载的bsdiff的话，会爆出bspatch.c:39:21: error: unknown type name 'u_char'; did you mean 'char'?这样的错误。这是由于bspatch.c中缺少了#include <sys/types.h>，加上即可。然后执行make命令。

bogon:bsdiff-4.3 Tony$ make
cc -O3 -lbz2    bsdiff.c   -o bsdiff
cc -O3 -lbz2    bspatch.c   -o bspatch

• step4 准备两个同一签名的apk，old.apk和.apk，放在bsdiff-4.3解压后的文件夹里。
• step5 使用bsdiff生成差异文件PATCH.patch，命令格式：bsdiff oldfile newfile patchfile（这一步操作可以放在服务端来执行）

bogon:bsdiff-4.3 Tony$ ./bsdiff old.apk new.apk PATCH.patch

-step6 使用bspatch合成新的apk，dest.apk。命令格式：bspatch oldfile newfile patchfile

bogon:bsdiff-4.3 Tony$ ./bspatch old.apk  dest.apk PATCH.patch 

• step7 验证生成的dest.apk和之前的new.apk使用一样，验证两个apk的md5值，即可。

bogon:bsdiff-4.3 Tony$ md5 new.apk 
MD5 (new.apk) = 55005cec2de8ad3668a0fd5bd8746f43
bogon:bsdiff-4.3 Tony$ md5 dest.apk 
MD5 (dest.apk) = 55005cec2de8ad3668a0fd5bd8746f43
bogon:bsdiff-4.3 Tony$ md5 old.apk 
MD5 (old.apk) = 822cc0938694008089ea5523f86585d7
bogon:bsdiff-4.3 Tony$ 

在Android中使用增量更新

ndk部分

• step1 新建一个PatchUtils的类，用于调用native的方法

public class PatchUtils {
    static PatchUtils instance;

    public static PatchUtils getInstance() {
        if (instance == null) {
            instance = new PatchUtils();
        }
        return instance;
    }

    static {
        System.loadLibrary("patchutils");
    }

    /**
     * native方法 使用路径为oldApkPath的apk与路径为patchPath的补丁包，合成新的apk，并存储于newApkPath
     * <p>
     * 返回：0，说明操作成功
     *
     * @param oldApkPath 示例:/sdcard/old.apk
     * @param newApkPath 示例:/sdcard/new.apk
     * @param patchPath  示例:/sdcard/xx.patch
     * @return
     */
    public static native int bspatch(String oldApkPath, String newApkPath, String patchPath);

}

• step2 使用javah命令生成PatchUtils的头文件，或者使用ndk-build里的javah生成头文件。会在jni文件夹下生成一个com_bigademo_updatedemo_PatchUtils.h的文件，其中com_bigademo_updatedemo是我的包名。

• step3 将bsdiff4.3文件夹中的bspatch.c文件导入到jni文件夹下。

• step4 将bzip2文件夹导入到jni文件夹下

• step5 删除bzip2中的除了以c和h结尾的其他文件。
  如图：
  

  jni文件夹目录

• step6 修改bspatch.c。引入bzip的文件，引入com_bigademo_updatedemo_PatchUtils.h，在bspatch.c中重写JNIEXPORT jint JNICALL Java_com_bigademo_updatedemo_PatchUtils_bspatch方法。代码如下

#if 0
__FBSDID("$FreeBSD: src/usr.bin/bsdiff/bspatch/bspatch.c,v 1.1 2005/08/06 01:59:06 cperciva Exp $");
#endif


#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <err.h>
#include <unistd.h>
#include <fcntl.h>
#include "bzip2/bzlib.c"
#include "bzip2/crctable.c"
#include "bzip2/compress.c"
#include "bzip2/decompress.c"
#include "bzip2/randtable.c"
#include "bzip2/blocksort.c"
#include "bzip2/huffman.c"
#include <com_bigademo_updatedemo_PatchUtils.h>
JNIEXPORT jint JNICALL Java_com_bigademo_updatedemo_PatchUtils_bspatch(JNIEnv *env,
        jclass cls, jstring old, jstring new, jstring patch) {
    int argc = 4;
    char * argv[argc];
    argv[0] = "bsdiff";
    argv[1] = (char*) ((*env)->GetStringUTFChars(env, old, 0));
    argv[2] = (char*) ((*env)->GetStringUTFChars(env, new, 0));
    argv[3] = (char*) ((*env)->GetStringUTFChars(env, patch, 0));

    printf("old apk = %s \n", argv[1]);
    printf("new apk = %s \n", argv[2]);
    printf("patch = %s \n", argv[3]);

    int ret = genpatch(argc, argv);

    printf("genDiff result = %d ", ret);

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

    return ret;
}


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 genpatch(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;
}

• step7 在jni下创建Android.mk和Application.mk两个文件

Android.mk

# 构建系统提供的宏函数 my-dir 将返回当前目录（包含 Android.mk 文件本身的目录）的路径，基本上是固定的，不需要去动
LOCAL_PATH := $(call my-dir)
# 会清除很多 LOCAL_XXX 变量，不会清除 LOCAL_PATH，基本上是固定的，不需要去动
include $(CLEAR_VARS)
# 需要构建模块的名称，会自动生成相应的 libNDKSample.so 文件，每个模块名称必须唯一，且不含任何空格
LOCAL_MODULE := patchutils
# 包含要构建到模块中的 C 或 C++ 源文件列表
LOCAL_SRC_FILES := bspatch.c
LOCAL_C_INCLUDES := /Users/Tony/Code/android/AndroidStudioProjects/demo/updatedemo/app/src/main/jni/bzip2
# 帮助系统将所有内容连接到一起，固定的，不需要去动
include $(BUILD_SHARED_LIBRARY)

Application.mk

APP_PLATFORM := android-16
# 选择不同的 ABI，多个使用空格作为分隔符，全部是all
APP_ABI := all

• step8 在module中的build.gradle中配置ndk。

android{
    ...
    defaultConfig{
        ndk{
            //这个名字就是在PatchUtils中loadLibrary的名字，同时和Android.mk中的LOCAL_MODULE的名字一样，也和生成的so的文件的名字类似。
            moduleName "patchutils"
        }
    }
    externalNativeBuild {
        ndkBuild {
            path "src/main/jni/Android.mk"
        }
    }
}

java部分

创建一个ApkExtract类，用于获取当前app的apk和安装新的apk。因为涉及到Android 7.0的，需要处理Provider的问题，同时在AndroidManifest.xml增加一些代码

public class ApkExtract {
    public static String extract(Context context) {
        context = context.getApplicationContext();
        ApplicationInfo applicationInfo = context.getApplicationInfo();
        String apkPath = applicationInfo.sourceDir;
        Log.d("info", apkPath);
        return apkPath;
    }
    public static void install(Context context, String apkPath) {
        Intent intent = new Intent(Intent.ACTION_VIEW);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
intent.setFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
            Uri contentUri = FileProvider.getUriForFile(context, BuildConfig.APPLICATION_ID + ".fileProvider", new File(apkPath));
            intent.setDataAndType(contentUri, "application/vnd.android.package-archive");
        } else {
            intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
            intent.setDataAndType(Uri.fromFile(new File(apkPath)),
                    "application/vnd.android.package-archive");
        }
        context.startActivity(intent);
    }
}

androidmanifest.xml

<application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
            <provider
            android:name="android.support.v4.content.FileProvider"
            android:authorities="${applicationId}.fileProvider"
            android:grantUriPermissions="true"
            android:exported="false">
            <meta-data
                android:name="android.support.FILE_PROVIDER_PATHS"
                android:resource="@xml/file_paths" />
  ...
  </application>

最后在需要更新的时候调用下面这个方法，当然先做一下动态调用读写权限的操作。

if (ContextCompat.checkSelfPermission(MainActivity.this, android.Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
                    ActivityCompat.requestPermissions(MainActivity.this, new String[]{android.Manifest.permission.WRITE_EXTERNAL_STORAGE}, 2);
                } else {
                    doBspatch();
//                    startActivity(new Intent(MainActivity.this, SecondActivity.class));
                }

 private void doBspatch() {
        final File destApk = new File(Environment.getExternalStorageDirectory(), "dest.apk");
        final File patch = new File(Environment.getExternalStorageDirectory(), "PATCH.patch");

        //一定要检查文件都存在
      int result=  PatchUtils.bspatch(ApkExtract.extract(this),
                destApk.getAbsolutePath(),
                patch.getAbsolutePath());
        Log.e("info","patch result   "+result);
        if (destApk.exists()) {
            ApkExtract.install(this, destApk.getAbsolutePath());
        }
    }

demo项目：https://github.com/yyt231/updatedemo

巨人的肩膀：
https://blog.csdn.net/lmj623565791/article/details/52761658
https://www.cnblogs.com/lping/p/5833090.html
https://blog.csdn.net/qq_33750826/article/details/75540738