###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。
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
