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##生命周期 ###创建

// Constructs a new message of the given message type. 
DBusMessage * 	dbus_message_new (int message_type)

// Constructs a new message representing a signal emission. 
DBusMessage * 	dbus_message_new_signal (const char *path, const char *interface, const char *name)

// Constructs a new message to invoke a method on a remote object. 
DBusMessage * 	dbus_message_new_method_call (const char *destination, 
	const char *path, const char *interface, const char *method)

// Constructs a message that is a reply to a method call. 
DBusMessage * 	dbus_message_new_method_return (DBusMessage *method_call)
// Creates a new message that is an error reply to another message.

DBusMessage * 	dbus_message_new_error (DBusMessage *reply_to, 
	const char *error_name, const char *error_message)

// Creates a new message that is an error reply to another message, 
// allowing you to use printf formatting.
DBusMessage * 	dbus_message_new_error_printf (DBusMessage *reply_to, 
	const char *error_name, const char *error_format,...)

###从DBusConnection中获取 通常对于发送的DBusMessage，我们需要明确的创建并设置适当的属性，对于接收的消息，直接使用DBusConnection的方法就可以了。例如

DBusMessage * msg;
DBusConnection * connection;
while (1) {
    dbus_connection_read_write(connection, 0);
    msg = dbus_connection_pop_message(connection);
}

###引用技术 DBUS中很多对象都使用应用技术来管理，DBusMessage也不例外。当dbus_message_unref之后，引用技术变成0，那么该对象就被销毁。

// Increments the reference count of a DBusMessage. 
DBusMessage * 	dbus_message_ref (DBusMessage *message)

// Decrements the reference count of a DBusMessage, freeing the message if the count reaches 0. 
void 	dbus_message_unref (DBusMessage *message)

###其他 // 拷贝消息 DBusMessage * dbus_message_copy (const DBusMessage *message)

##消息类型

  1. DBUS_MESSAGE_TYPE_SIGNAL : 事件
  2. DBUS_MESSAGE_TYPE_METHOD_CALL ： 方法调用
  3. DBUS_MESSAGE_TYPE_METHOD_RETURN ： 方法返回
  4. DBUS_MESSAGE_TYPE_ERROR ： 错误

前面提到，消息只有两种，实际上，DBUS_MESSAGE_TYPE_METHOD_RETURN和DBUS_MESSAGE_TYPE_ERROR是可以和DBUS_MESSAGE_TYPE_METHOD_CALL归为一大类的。

// 获得消息类型 
int 	dbus_message_get_type (DBusMessage *message)、

// Checks whether the message is a method call with the given interface and member fields.
dbus_bool_t 	dbus_message_is_method_call (DBusMessage *message, 
	const char *interface, const char *method)

// Checks whether the message is a signal with the given interface and member fields.
dbus_bool_t 	dbus_message_is_signal (DBusMessage *message, 
	const char *interface, const char *signal_name)

// Checks whether the message is an error reply with the given error name. 
dbus_bool_t 	dbus_message_is_error (DBusMessage *message, const char *error_name)

##基本属性 ###Path

// Sets the object path this message is being sent to (for DBUS_MESSAGE_TYPE_METHOD_CALL)
// the one a signal is being emitted from (for DBUS_MESSAGE_TYPE_SIGNAL). 
dbus_bool_t 	dbus_message_set_path (DBusMessage *message, const char *object_path)
// Gets the object path this message is being sent to (for DBUS_MESSAGE_TYPE_METHOD_CALL) 
// being emitted from (for DBUS_MESSAGE_TYPE_SIGNAL). 
char * 	dbus_message_get_path (DBusMessage *message)
// Checks if the message has a particular object path. 
dbus_bool_t 	dbus_message_has_path (DBusMessage *message, const char *path)
// Gets the object path this message is being sent to (for DBUS_MESSAGE_TYPE_METHOD_CALL) 
// being emitted from (for DBUS_MESSAGE_TYPE_SIGNAL) in a decomposed format (one array element per path component). 
dbus_bool_t 	dbus_message_get_path_decomposed (DBusMessage *message, char ***path)

###Interface

// Sets the interface this message is being sent to (for DBUS_MESSAGE_TYPE_METHOD_CALL) 
// the interface a signal is being emitted from (for DBUS_MESSAGE_TYPE_SIGNAL). 
dbus_bool_t 	dbus_message_set_interface (DBusMessage *message, const char *interface)
// Gets the interface this message is being sent to (for DBUS_MESSAGE_TYPE_METHOD_CALL) 
// being emitted from (for DBUS_MESSAGE_TYPE_SIGNAL). 
const char * 	dbus_message_get_interface (DBusMessage *message)
// Checks if the message has an interface. 
dbus_bool_t 	dbus_message_has_interface (DBusMessage *message, const char *interface)

###Member // Sets the interface member being invoked (DBUS_MESSAGE_TYPE_METHOD_CALL) // emitted (DBUS_MESSAGE_TYPE_SIGNAL). dbus_bool_t dbus_message_set_member (DBusMessage *message, const char *member)

// Gets the interface member being invoked (DBUS_MESSAGE_TYPE_METHOD_CALL) 
// emitted (DBUS_MESSAGE_TYPE_SIGNAL). 
const char * 	dbus_message_get_member (DBusMessage *message)
// Checks if the message has an interface member. 
dbus_bool_t 	dbus_message_has_member (DBusMessage *message, const char *member)

###发送接收方 对于方法调用，需要明确地指定发送接收方

// Checks whether the message has the given unique name as its sender. 
dbus_bool_t 	dbus_message_has_sender (DBusMessage *message, const char *name)
// Sets the message sender. 
dbus_bool_t 	dbus_message_set_sender (DBusMessage *message, const char *sender)
// Gets the unique name of the connection which originated this message, or NULL if unknown or inapplicable. 
const char * 	dbus_message_get_sender (DBusMessage *message)
// Checks whether the message was sent to the given name. 
dbus_bool_t 	dbus_message_has_destination (DBusMessage *message, const char *name)

dbus_bool_t 	dbus_message_set_destination (DBusMessage *message, const char *destination)
 	// Sets the message's destination.
// Gets the destination of a message or NULL if there is none set. 
const char * 	dbus_message_get_destination (DBusMessage *message)

dbus_message_new函数很少用，不过在使用它创建DBusMessage之后，在配合上述属性设置的方法，也可以实现dbus_message_new_signal等函数相同的效果。

##私有数据 DBusMessage可以携带一些私有数据在各个程序逻辑中传递，方便管理（注意和参数相区分，后者会被发送到连接对端）

// Allocates an integer ID to be used for storing application-specific data on any DBusMessage. 
dbus_bool_t 	dbus_message_allocate_data_slot (dbus_int32_t *slot_p)

// Deallocates a global ID for message data slots. 
void 	dbus_message_free_data_slot (dbus_int32_t *slot_p)

// Stores a pointer on a DBusMessage, along with an optional function to be used 
// for freeing the data when the data is set again, or when the message is finalized. 
dbus_bool_t 	dbus_message_set_data (DBusMessage *message, 
	dbus_int32_t slot, void *data, DBusFreeFunction free_data_func)
	
// Retrieves data previously set with dbus_message_set_data(). 
void * 	dbus_message_get_data (DBusMessage *message, dbus_int32_t slot)

##参数

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <dbus/dbus.h>
#include <unistd.h>

int main()
{
	DBusMessage * msg;
	msg = dbus_message_new_signal(
				"/test/signal/Object1fasdf",
				"test.signal.Type", "Test");


	//给这个信号（messge）具体的内容
	{
		DBusMessageIter iter;
		DBusMessageIter subiter;
		dbus_message_iter_init_append(msg, &iter);
		// 基本类型，字符串
		const char * msg_ = "hello world";
		dbus_message_iter_append_basic(&iter, DBUS_TYPE_STRING, &msg_);

		// 结构
		dbus_message_iter_open_container(
				&iter,
				DBUS_TYPE_STRUCT,
				NULL,
				&subiter);
		dbus_message_iter_append_basic(&subiter, DBUS_TYPE_STRING, &msg_);
		dbus_message_iter_append_basic(&subiter, DBUS_TYPE_STRING, &msg_);
		dbus_message_iter_close_container(&iter,&subiter);

		// 基本类型 int
		int intval_ = 123456;
		dbus_message_iter_append_basic(&iter, DBUS_TYPE_INT32, &intval_);

		// 数组
		/**
		 * For variants, the contained_signature should be the type of
		 * the single value inside the variant. For structs and dict entries,
		 *  contained_signature should be NULL;
		 *  it will be set to whatever types you write into the struct.
		 *   For arrays, contained_signature should be the type
		 *    of the array elements.
		 */
		dbus_message_iter_open_container(&iter,
				DBUS_TYPE_ARRAY,
				"i", // i 对应 DBUS_TYPE_INT32
				&subiter);
		int array[] = { 1, 2, 3 ,4 ,5};
		int* fuck_ = array;
		dbus_message_iter_append_fixed_array (
				&subiter,
				DBUS_TYPE_INT32,
				&fuck_,
				sizeof(array)/sizeof(array[0]));
		dbus_message_iter_close_container(&iter,&subiter);

		// 基本类型 浮点
		double doubleval_ = 1.234567;
		dbus_message_iter_append_basic(&iter, DBUS_TYPE_DOUBLE, &doubleval_);
	}
	{
		// 遍历参数
		DBusMessageIter iter;
		dbus_message_iter_init(msg, &iter);
		int current_type;
		int cnt_ = 1;
		while ((current_type = dbus_message_iter_get_arg_type(&iter))
				!= DBUS_TYPE_INVALID)
		{
			// 基本类型
			if(DBUS_TYPE_STRING == current_type)
			{
				char* value_;
				dbus_message_iter_get_basic(&iter, &value_);
				printf("iter %d string '%s'\n",cnt_,value_);
			}
			else if(DBUS_TYPE_INT32 == current_type)
			{
				int value_;
				dbus_message_iter_get_basic(&iter, &value_);
				printf("iter %d int32 '%d'\n",cnt_,value_);
			}
			else if(DBUS_TYPE_DOUBLE == current_type)
			{
				double value_;
				dbus_message_iter_get_basic(&iter, &value_);
				printf("iter %d int32 '%f'\n",cnt_,value_);
			}
			// 数组类型
			else if(DBUS_TYPE_ARRAY == current_type)
			{
				// 先获取数组元素的类型
				if(DBUS_TYPE_INT32 == dbus_message_iter_get_element_type(&iter))
				{
					// 跳进去
					DBusMessageIter subiter;
					dbus_message_iter_recurse(&iter, &subiter);
					int* array_;
					int array_len_;
					// 获得地址和数组长度
					dbus_message_iter_get_fixed_array(&subiter, &array_,&array_len_);
					printf("iter %d array len '%d' type\n",
							cnt_,
							array_len_);
					int index = 0;
					for(;index < array_len_;index++)
					{
						printf("iter %d array [%d] = '%d'\n",
								cnt_,
								index,
								array_[index]);
					}
				}
				else
				{
					printf("iter %d array type\n");
				}
			}
			// 结构类型
			else if(DBUS_TYPE_STRUCT == current_type)
			{
				printf("iter %d struct type\n");

				// 跳进去
				DBusMessageIter subiter;
				int subcnt_ = 0;
				dbus_message_iter_recurse(&iter, &subiter);

				// 遍历，同上
				int sub_current_type;
				while ((sub_current_type = dbus_message_iter_get_arg_type(&subiter))
						!= DBUS_TYPE_INVALID)
				{
					printf("sub iter %d struct type\n",subcnt_);
					dbus_message_iter_next(&subiter);
					subcnt_ ++;
				}
			}
			else
			{
				printf("iter %d unknown type\n");
			}
			dbus_message_iter_next(&iter);
			cnt_ ++;
		}
	}

	return 0;
}

##参考

  1. http://dbus.freedesktop.org/doc/api/html/group__DBusMessage.html
  2. http://hi.baidu.com/9562512/item/f93cac0be4849cdcdce5b076
  3. http://dbus.freedesktop.org/doc/api/html/group__DBusProtocol.html#ga7eb77066dadf5415896b44c56d93acce