android binder机制实现

核心提示：data.writeInt32(pid);data.writeInt32(uid);remote()->transact(CHECK_PERMISSION_TRANSACTION, data, &reply);if (reply.readInt32() != 0) return 0;return reply.re

data.writeInt32(pid);

data.writeInt32(uid);

remote()->transact(CHECK_PERMISSION_TRANSACTION, data, &reply);

if (reply.readInt32() != 0) return 0;

return reply.readInt32() != 0;

}

};

class BpPermissionController : public BpInterface { public: BpPermissionController(const sp& impl) : BpInterface(impl) { } virtual bool checkPermission(const String16& permission, int32_t pid, int32_t uid) { Parcel data, reply; data.writeInterfaceToken(IPermissionController:: getInterfaceDescriptor()); data.writeString16(permission); data.writeInt32(pid); data.writeInt32(uid); remote()->transact(CHECK_PERMISSION_TRANSACTION, data, &reply); if (reply.readInt32() != 0) return 0; return reply.readInt32() != 0; } };

IMPLEMENT_META_INTERFACE(PermissionController, "android.os.IPermissionController");

BpPermissionController继承了BpInterface，它本身是一个

已经实现的类，而且并没有在接口中体现。这个类按照格式写就可以，在实现checkPermission()函数的过程中，使用Parcel作为传输数据

的容器，传输中时候transact()函数，其参数需要包含枚举值CHECK_PERMISSION_TRANSACTION。

IMPLEMENT_META_INTERFACE用于扶助生成。

BnPermissionController中实现的onTransact()函数如下所示：

Java代码 < width="14" height="15" src="http://mintelong.javaeye.com/javascripts/syntaxhighlighter/clipboard_new.swf" pluginspage="http://www.macromedia.com/go/getflashplayer">

status_t BnPermissionController:: BnTransact(

uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags)

{

switch(code) {

case CHECK_PERMISSION_TRANSACTION: {

CHECK_INTERFACE(IPermissionController, data, reply);

String16 permission = data.readString16();

int32_t pid = data.readInt32();

int32_t uid = data.readInt32();

bool res = checkPermission(permission, pid, uid);