深入理解PackageManagerService

mSettings = new Settings();
        mSettings.addSharedUserLPw("android.uid.system",
                Process.SYSTEM_UID, ApplicationInfo.FLAG_SYSTEM);
        mSettings.addSharedUserLPw("android.uid.phone",
                MULTIPLE_APPLICATION_UIDS
                        ? RADIO_UID : FIRST_APPLICATION_UID,
                ApplicationInfo.FLAG_SYSTEM);
        mSettings.addSharedUserLPw("android.uid.log",
                MULTIPLE_APPLICATION_UIDS
                        ? LOG_UID : FIRST_APPLICATION_UID,
                ApplicationInfo.FLAG_SYSTEM);
        mSettings.addSharedUserLPw("android.uid.nfc",
                MULTIPLE_APPLICATION_UIDS
                        ? NFC_UID : FIRST_APPLICATION_UID,
                ApplicationInfo.FLAG_SYSTEM);

mHandlerThread.start();
mHandler = new PackageHandler(mHandlerThread.getLooper());

 private UserInfo readUser(int id) {
        int flags = 0;
        String name = null;

        FileInputStream fis = null;
        try {
            File userFile = new File(mUsersDir, Integer.toString(id) + ".xml");
            fis = new FileInputStream(userFile);
            XmlPullParser parser = Xml.newPullParser();
            parser.setInput(fis, null);
            int type;
            while ((type = parser.next()) != XmlPullParser.START_TAG
                    && type != XmlPullParser.END_DOCUMENT) {
                ;
            }

            if (type != XmlPullParser.START_TAG) {
                Slog.e(LOG_TAG, "Unable to read user " + id);
                return null;
            }

            if (type == XmlPullParser.START_TAG && parser.getName().equals(TAG_USER)) {
                String storedId = parser.getAttributeValue(null, ATTR_ID);
                if (Integer.parseInt(storedId) != id) {
                    Slog.e(LOG_TAG, "User id does not match the file name");
                    return null;
                }
                String flagString = parser.getAttributeValue(null, ATTR_FLAGS);
                flags = Integer.parseInt(flagString);

                while ((type = parser.next()) != XmlPullParser.START_TAG
                        && type != XmlPullParser.END_DOCUMENT) {
                }
                if (type == XmlPullParser.START_TAG && parser.getName().equals(TAG_NAME)) {
                    type = parser.next();
                    if (type == XmlPullParser.TEXT) {
                        name = parser.getText();
                    }
                }
            }
            fis.close();

            UserInfo userInfo = new UserInfo(id, name, flags);
            return userInfo;

        } catch (IOException ioe) {
        } catch (XmlPullParserException pe) {
        }
        return null;
}

public class UserInfo implements Parcelable {
     public static final int FLAG_PRIMARY = 0x00000001;

   public static final int FLAG_ADMIN   = 0x00000002;
 public static final int FLAG_GUEST   = 0x00000004;

   public int id;//用户id
    public String name;//用户名称
    public int flags;//用户标记，是primary，admin，guest等等

    public UserInfo(int id, String name, int flags) {
        this.id = id;
        this.name = name;
        this.flags = flags;
    }

 public boolean isPrimary() {
        return (flags & FLAG_PRIMARY) == FLAG_PRIMARY;
    }

    public boolean isAdmin() {
        return (flags & FLAG_ADMIN) == FLAG_ADMIN;
    }

    public boolean isGuest() {
        return (flags & FLAG_GUEST) == FLAG_GUEST;
    }
 public int describeContents() {
        return 0;
    }

    public void writeToParcel(Parcel dest, int parcelableFlags) {
        dest.writeInt(id);
        dest.writeString(name);
        dest.writeInt(flags);
    }

    public static final Parcelable.Creator<UserInfo> CREATOR
            = new Parcelable.Creator<UserInfo>() {
        public UserInfo createFromParcel(Parcel source) {
            return new UserInfo(source);
        }
        public UserInfo[] newArray(int size) {
            return new UserInfo[size];
        }
    };

    private UserInfo(Parcel source) {
        id = source.readInt();
        name = source.readString();
        flags = source.readInt();
    }
}

void readPermissions() {
        //  指向etc/permissions 文件
        File libraryDir = new File(Environment.getRootDirectory(), "etc/permissions");
         ..

        // Iterate over the files in the directory and scan .xml files
        for (File f : libraryDir.listFiles()) {
            //不处理etc/permissions/platform.xml 
            if (f.getPath().endsWith("etc/permissions/platform.xml")) {
                continue;
            }
            //处理.xml文件
            if (!f.getPath().endsWith(".xml")) {
               
                continue;
            }
            //处理刻度的
            if (!f.canRead()) {
               
                continue;
            }

            readPermissionsFromXml(f);
        }

        // Read permissions from .../etc/permissions/platform.xml last so it will take precedence
          最后解析etc/permissions/platform.xm 文件
        final File permFile = new File(Environment.getRootDirectory(),"etc/permissions/platform.xml");
        readPermissionsFromXml(permFile);
    }

<permissions>
<!--为指定group 的gid分配相应的权限--> 
<!--为指定gid为net_bt_admin分配 BLUETOOTH_ADMIN权限--> 
 <permission name="android.permission.BLUETOOTH_ADMIN" >
        <group gid="net_bt_admin" />
    </permission>

    <permission name="android.permission.BLUETOOTH" >
        <group gid="net_bt" />
    </permission>

    <permission name="android.permission.BLUETOOTH_STACK" >
        <group gid="net_bt_stack" />
    </permission>

<!--为指定的uid分配相应的权限--> 
<!--为指定uid为  shell 分配WRITE_EXTERNAL_STORAGE权限-->  
   <assign-permission name="android.permission.WRITE_EXTERNAL_STORAGE" uid="shell" />
    <assign-permission name="android.permission.SEND_SMS" uid="shell" />
    <assign-permission name="android.permission.CALL_PHONE" uid="shell" />
    <assign-permission name="android.permission.READ_CONTACTS" uid="shell" />
    <assign-permission name="android.permission.WRITE_CONTACTS" uid="shell" />

<!--连接库-->
 <library name="android.test.runner" file="/system/framework/android.test.runner.jar" />
    <library name="javax.obex" file="/system/framework/javax.obex.jar"/>

</permissions>

<permissions>
    <feature name="android.hardware.wifi" />
</permissions>

permissions>
    <feature name="android.software.live_wallpaper" />
</permissions>

 int scanMode = SCAN_MONITOR | SCAN_NO_PATHS | SCAN_DEFER_DEX;
            if (mNoDexOpt) {                
                scanMode |= SCAN_NO_DEX;//不需要DEX优化
            }
            final HashSet<String> libFiles = new HashSet<String>();
            mFrameworkDir = new File(Environment.getRootDirectory(), "framework");
            mDalvikCacheDir = new File(dataDir, "dalvik-cache");
            boolean didDexOpt = false;
            
            String bootClassPath = System.getProperty("java.boot.class.path");
            if (bootClassPath != null) {
                String[] paths = splitString(bootClassPath, ':');
                for (int i=0; i<paths.length; i++) {
                    try {
                         //判断是否需要dex优化，如果需要则加入到libFiles中
                        if (dalvik.system.DexFile.isDexOptNeeded(paths[i])) {
                            libFiles.add(paths[i]);
                            mInstaller.dexopt(paths[i], Process.SYSTEM_UID, true);
                            didDexOpt = true;
                        }
                    } catch (FileNotFoundException e) {
                        
                    } catch (IOException e) {
                      
                    }
                }
            } else {
              
            }

             //在platform.xml文件中存储library  标签的变量
            if (mSharedLibraries.size() > 0) {
                Iterator<String> libs = mSharedLibraries.values().iterator();
                while (libs.hasNext()) {
                    String lib = libs.next();
                    try {
                         //判断是否需要dex优化
                        if (dalvik.system.DexFile.isDexOptNeeded(lib)) {
                            libFiles.add(lib);
                            mInstaller.dexopt(lib, Process.SYSTEM_UID, true);
                            didDexOpt = true;
                        }
                    } catch (FileNotFoundException e) {
                         
                    } catch (IOException e) {
                         
                    }
                }
            }

  //对于framework-res.apk直接添加到libFiles中
 libFiles.add(mFrameworkDir.getPath() + "/framework-res.apk");
//mFrameworkDir代表 /system/frameworks目录，优化里面的apk和jar文件
String[] frameworkFiles = mFrameworkDir.list();
            if (frameworkFiles != null) {
                for (int i=0; i<frameworkFiles.length; i++) {
                 .....  
                }
            }

            if (didDexOpt) {//如果didDexOpt为true，则说明优化成功      
               //mDalvikCacheDir代表      /data/dalvik-cache  
                String[] files = mDalvikCacheDir.list();
                if (files != null) {
                    for (int i=0; i<files.length; i++) {
                        String fn = files[i];
                         //删除data@app@ 或者data@app-private@的文件
                          if (fn.startsWith("data@app@")|| fn.startsWith("data@app-private@")) {                           
                            (new File(mDalvikCacheDir, fn)).delete();//删除缓存数据
                        }
                    }
                }
            }

 <span style="white-space:pre">	</span>    //监控 system/framework目录
            mFrameworkInstallObserver = new AppDirObserver(mFrameworkDir.getPath(), OBSERVER_EVENTS, true);
            mFrameworkInstallObserver.startWatching();
            scanDirLI(mFrameworkDir, PackageParser.PARSE_IS_SYSTEM| PackageParser.PARSE_IS_SYSTEM_DIR,scanMode | SCAN_NO_DEX, 0);
            
           //监控 system/app目录 
            mSystemAppDir = new File(Environment.getRootDirectory(), "app");
            mSystemInstallObserver = new AppDirObserver(mSystemAppDir.getPath(), OBSERVER_EVENTS, true);
            mSystemInstallObserver.startWatching();
            scanDirLI(mSystemAppDir, PackageParser.PARSE_IS_SYSTEM| PackageParser.PARSE_IS_SYSTEM_DIR, scanMode, 0);
            
             //监控 /vendor/app目录  
            mVendorAppDir = new File("/vendor/app");
            mVendorInstallObserver = new AppDirObserver(mVendorAppDir.getPath(), OBSERVER_EVENTS, true);
            mVendorInstallObserver.startWatching();
            scanDirLI(mVendorAppDir, PackageParser.PARSE_IS_SYSTEM| PackageParser.PARSE_IS_SYSTEM_DIR, scanMode, 0);

            mInstaller.moveFiles();

            ...            
            mAppInstallDir = new File(dataDir, "app");
            //look for any incomplete package installations
            ArrayList<PackageSetting> deletePkgsList = mSettings.getListOfIncompleteInstallPackagesLPr();
            //clean up list
            for(int i = 0; i < deletePkgsList.size(); i++) {               
                cleanupInstallFailedPackage(deletePkgsList.get(i));
            }
          
            deleteTempPackageFiles();

            if (!mOnlyCore) {
                 
                mAppInstallObserver = new AppDirObserver(mAppInstallDir.getPath(), OBSERVER_EVENTS, false);
                mAppInstallObserver.startWatching();
                scanDirLI(mAppInstallDir, 0, scanMode, 0);
    
                mDrmAppInstallObserver = new AppDirObserver(mDrmAppPrivateInstallDir.getPath(), OBSERVER_EVENTS, false);
                mDrmAppInstallObserver.startWatching();
                scanDirLI(mDrmAppPrivateInstallDir, PackageParser.PARSE_FORWARD_LOCK,scanMode, 0);
            } else {
                mAppInstallObserver = null;
                mDrmAppInstallObserver = null;
            }

 public int install(String name, int uid, int gid) {
        StringBuilder builder = new StringBuilder("install");
        builder.append(' ');
        builder.append(name);
        builder.append(' ');
        builder.append(uid);
        builder.append(' ');
        builder.append(gid);
        return execute(builder.toString());
    }

 private int execute(String cmd) {
        String res = transaction(cmd);//调用transaction 方法
        try {
            return Integer.parseInt(res);
        } catch (NumberFormatException ex) {
            return -1;
        }
    }

 private synchronized String transaction(String cmd) {
        if (!connect()) {//连接installd服务
            Slog.e(TAG, "connection failed");
            return "-1";
        }

        if (!writeCommand(cmd)) {//向installd发送命令       
            Slog.e(TAG, "write command failed? reconnect!");
            if (!connect() || !writeCommand(cmd)) {
                return "-1";
            }
        }
        if (LOCAL_DEBUG) {
            Slog.i(TAG, "send: '" + cmd + "'");
        }
        if (readReply()) {//读取返回的数据
            String s = new String(buf, 0, buflen);
            if (LOCAL_DEBUG) {
                Slog.i(TAG, "recv: '" + s + "'");
            }
            return s;
        } else {
            if (LOCAL_DEBUG) {
                Slog.i(TAG, "fail");
            }
            return "-1";
        }
    }

struct cmdinfo {
    const char *name;  //命令名称
    unsigned numargs; //参数个数
    int (*func)(char **arg, char reply[REPLY_MAX]);  //该命令对应的函数
};

struct cmdinfo cmds[] = {
    { "ping",                 0, do_ping },
    { "install",              3, do_install },
    { "dexopt",               3, do_dexopt },
    { "movedex",              2, do_move_dex },
    { "rmdex",                1, do_rm_dex },
    { "remove",               2, do_remove },
    { "rename",               2, do_rename },
    { "freecache",            1, do_free_cache },
    { "rmcache",              1, do_rm_cache },
    { "protect",              2, do_protect },
    { "getsize",              4, do_get_size },
    { "rmuserdata",           2, do_rm_user_data },
    { "movefiles",            0, do_movefiles },
    { "linklib",              2, do_linklib },
    { "unlinklib",            1, do_unlinklib },
    { "mkuserdata",           3, do_mk_user_data },
    { "rmuser",               1, do_rm_user },
};

int install(const char *pkgname, uid_t uid, gid_t gid)
{
    char pkgdir[PKG_PATH_MAX];
    char libdir[PKG_PATH_MAX];

    if ((uid < AID_SYSTEM) || (gid < AID_SYSTEM)) {
        LOGE("invalid uid/gid: %d %d\n", uid, gid);
        return -1;
    }

    if (create_pkg_path(pkgdir, pkgname, PKG_DIR_POSTFIX, 0)) {
        LOGE("cannot create package path\n");
        return -1;
    }

    if (create_pkg_path(libdir, pkgname, PKG_LIB_POSTFIX, 0)) {
        LOGE("cannot create package lib path\n");
        return -1;
    }

    if (mkdir(pkgdir, 0751) < 0) {
        LOGE("cannot create dir '%s': %s\n", pkgdir, strerror(errno));
        return -errno;
    }
    if (chmod(pkgdir, 0751) < 0) {
        LOGE("cannot chmod dir '%s': %s\n", pkgdir, strerror(errno));
        unlink(pkgdir);
        return -errno;
    }
    if (chown(pkgdir, uid, gid) < 0) {
        LOGE("cannot chown dir '%s': %s\n", pkgdir, strerror(errno));
        unlink(pkgdir);
        return -errno;
    }
    if (mkdir(libdir, 0755) < 0) {
        LOGE("cannot create dir '%s': %s\n", libdir, strerror(errno));
        unlink(pkgdir);
        return -errno;
    }
    if (chmod(libdir, 0755) < 0) {
        LOGE("cannot chmod dir '%s': %s\n", libdir, strerror(errno));
        unlink(libdir);
        unlink(pkgdir);
        return -errno;
    }
    if (chown(libdir, AID_SYSTEM, AID_SYSTEM) < 0) {
        LOGE("cannot chown dir '%s': %s\n", libdir, strerror(errno));
        unlink(libdir);
        unlink(pkgdir);
        return -errno;
    }
    return 0;
}