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分类: 嵌入式
2018-05-09 15:02:51
说到 DBus 用过的人大概都能明白其工作的流程。典型的使用流程是,向 DBus 服务进程发送数据,然后接收其返回的数据。简单的说,就像调用函数一样,向服务进程发送数据就相当于函数的参数,其返回的数据就相当于函数返回的结果。虽然明白了流程,但想要使用 C语言 通过已有的 DBus 服务进行操作,仍然是一项不太容易的工作(对像我这样的菜鸟^_^),因为数据的类型真是太多了, 使用 Python 会简单一点。简单点的有 Boolean, Byte, Int32, Int64, String, ObjectPath, Signature 等; 复杂一点的有 Array, Struct, Dict 等。如果不能弄清楚它们之间的联系,那么将是一件非常头痛的事。为了使我研究的结果不被淡忘,于是有了这篇文章。
上一篇讨论了基本的数据类型的传递,这次我们就讨论难一点的, 高级数据类型 的传递。这里我们会讨论四种高级的(也就是难一点的)数据类型的传递: ARRAY, STRUCT, DICT_ENTRY, VARIANT, 具体请参照 。
同样先给出 Python 编写的服务与测试(这次没有 shell 脚本了)。
advanced_data_deliver_service.py
#!/usr/bin/env python
import gobject
import dbus
import dbus.service
import dbus.mainloop.glib
class AdvancedData(dbus.service.Object):
def __init__(self, bus, object_path):
dbus.service.Object.__init__(self, bus, object_path)
self._last_input = None
@dbus.service.method('airead.fan.AdvancedDataType', in_signature='ai', out_signature='ai')
def IntArrayPrint(self, ai):
print "receive int array:", ai
for i in range(len(ai)):
print ai[i],
ai[i] = ai[i] + 1
print '\n' + '=' * 33
return ai
@dbus.service.method('airead.fan.AdvancedDataType', out_signature='(sidb)')
def StructPrint(self, struct):
print "receive struct:", struct
for value in struct:
print value
print '=' * 33
return ('Li', 24, 55.1, False)
@dbus.service.method('airead.fan.AdvancedDataType', in_signature='a{ss}', out_signature='a{ss}')
def DictPrint(self, dict):
print "receive dict:", dict
for k in dict:
print "%s: %s" % (k, dict[k])
print '=' * 33
return {'fan': "male", 'li': "female"}
@dbus.service.method('airead.fan.AdvancedDataType', in_signature='v', out_signature='v')
def VariantPrint(self, variant):
print "receive variant:", variant
print '=' * 33
return {'fan': "male", 'li': "female"}
if __name__ == '__main__':
dbus.mainloop.glib.DBusGMainLoop(set_as_default=True)
session_bus = dbus.SessionBus()
name = dbus.service.BusName("airead.fan.AdvancedDataType", session_bus)
object = AdvancedData(session_bus, '/airead/fan/AdvancedDataType')
mainloop = gobject.MainLoop()
print "Running example service."
mainloop.run()
advanced_data_deliver_test_py.py
#!/usr/bin/python
import sys
import dbus
from traceback import print_exc
def main():
bus = dbus.SessionBus()
try:
remote_object = bus.get_object("airead.fan.AdvancedDataType", "/airead/fan/AdvancedDataType")
dbus_interface = dbus.Interface(remote_object, "airead.fan.AdvancedDataType")
#test dictionary
dic = {'a':'apple', 'b':'banana', 'c':'cherry'}
ret = dbus_interface.DictPrint(dic)
print ret
print '=' * 33 + "\n"
#test int array
intarray = [1, 2, 3, 4, 5, 6]
ret = dbus_interface.IntArrayPrint(intarray)
print ret
print '=' * 33 + "\n"
#test struct
struct = ("fan", 24, 70.5, False)
ret = dbus_interface.StructPrint(struct)
print ret
print '=' * 33 + "\n"
#test variant
variant = dic
ret = dbus_interface.VariantPrint(variant)
print ret
print '-' * 33 + "\n"
variant = intarray
ret = dbus_interface.VariantPrint(variant)
print ret
print '-' * 33 + "\n"
variant = struct
ret = dbus_interface.VariantPrint(variant)
print ret
print '-' * 33 + "\n"
except dbus.DBusException:
print_exc()
sys.exit(1)
main()
以下代码仅仅为了演示数据类型的传递,不保证没有内存泄漏,请仔细检查后再使用。
ARRAY: glib->garray *, G_TYPE_ARRAY, dbus->'a'
传递字节数组的话使用 "ay", 传递 ObjectPath 数组的话使用 "ao", 传递整数数组的话使用 "ai", 具体可以使用 Python 来写 service 进行测试。下面是一个传递整数数组的例子。在这个例子中有几个要点:
int send_recv_int_array(DBusGProxy *proxy)
{
char *method;
GError *error;
GArray *garray, *ret;
gint i, j;
garray = g_array_new (FALSE, FALSE, sizeof (gint));
for (i = 0; i < 6; i++) {
j = i + 1;
g_array_append_val(garray, j);
}
method = "IntArrayPrint";
if (!dbus_g_proxy_call(proxy, method, &error,
DBUS_TYPE_G_INT_ARRAY, garray,
G_TYPE_INVALID,
DBUS_TYPE_G_INT_ARRAY, &ret,
G_TYPE_INVALID)) {
g_printerr("call %s failed: %s\n", method, error->message);
g_error_free(error);
error = NULL;
return -1;
}
g_print("receive int array:\n");
for (i = 0; i < ret->len; i++) {
g_print("%d ", g_array_index(ret, gint, i));
}
g_print("\n=================================\n\n");
return 0;
}
STRUCT: glib->GValueArray *, ????, dbus->'()'
结构体在 D-Bus 服务进程中的声名为 (??), 其中 `?' 可以任意数据类型。比如
// (si)
struct str_int {
gchar *s;
gint i;
};
// (sidb)
struct str_int_double_boolean {
gchar *s;
gint i;
gdouble d;
gboolean b;
};
下面演示了 (sidb) 在 D-Bus 中的传递。代码分为三大块:
#define DBUS_STRUCT_STRING_INT_DOUBLE_BOOLEAN ( \
dbus_g_type_get_struct ( "GValueArray", G_TYPE_STRING, G_TYPE_INT, \
G_TYPE_DOUBLE, G_TYPE_BOOLEAN, G_TYPE_INVALID))
int send_recv_struct(DBusGProxy *proxy)
{
char *method;
GError *error = NULL;
GValueArray *ret, *send_array;
GValue *gval;
GValue send_gval[4] = `0`;
int i;
g_value_init (&send_gval[0], G_TYPE_STRING);
g_value_set_string(&send_gval[0], "fan");
g_value_init (&send_gval[1], G_TYPE_INT);
g_value_set_int(&send_gval[1], 24);
g_value_init (&send_gval[2], G_TYPE_DOUBLE);
g_value_set_double(&send_gval[2], 70.2);
g_value_init (&send_gval[3], G_TYPE_BOOLEAN);
g_value_set_boolean(&send_gval[3], FALSE);
send_array = g_value_array_new(0);
for (i = 0; i < 4; i++) {
send_array = g_value_array_append(send_array, &send_gval[i]);
}
method = "StructPrint";
if (!dbus_g_proxy_call(proxy, method, &error,
DBUS_STRUCT_STRING_INT_DOUBLE_BOOLEAN, send_array,
G_TYPE_INVALID,
DBUS_STRUCT_STRING_INT_DOUBLE_BOOLEAN, &ret,
G_TYPE_INVALID)) {
g_printerr("call %s failed: %s\n", method, error->message);
g_error_free(error);
error = NULL;
return -1;
}
g_print("receive struct:\n");
for (i = 0; i < ret->n_values; i++) {
gval = g_value_array_get_nth(ret, i);
if (G_VALUE_TYPE(gval) == G_TYPE_STRING) {
g_print("%s\n", g_value_get_string(gval));
} else if (G_VALUE_TYPE(gval) == G_TYPE_DOUBLE) {
g_print("%f\n", g_value_get_double(gval));
} else if (G_VALUE_TYPE(gval) == G_TYPE_INT) {
g_print("%d\n", g_value_get_int(gval));
} else if (G_VALUE_TYPE(gval) == G_TYPE_BOOLEAN) {
g_print("%d\n", g_value_get_boolean(gval));
}
}
g_print("\n=================================\n\n");
return 0;
}
回忆一下,在传递 ARRAY 中我们遇到了 DBUS_TYPE_G_INT_ARRAY , 那么它是如何定义的呢?
DBUS_TYPE_G_INT_ARRAY (dbus_g_type_get_collection ("GArray", G_TYPE_INT))
它是 dbus-glib 库帮我定义的,使用到了 dbus_g_type_get_collection() 函数。当我们传递某些特殊数据的时候,如果 dbus-glib 库没有它的定义,那我们需要使用
等相关函数自行定义。上面的例子中我们就定义一个 struct 类型:
DBUS_STRUCT_STRING_INT_DOUBLE_BOOLEAN ( \
dbus_g_type_get_struct ( "GValueArray", G_TYPE_STRING, G_TYPE_INT, \
G_TYPE_DOUBLE, G_TYPE_BOOLEAN, G_TYPE_INVALID))
具体细节请参考 ,以及详解中其它的类型定义。 map 对应 GHashTable, collection 对应 GArray, struct 对 GValueArray 等。
另外,STRUCT 数据还有另一种构造方法,在 `使用 VARINAT 传递 STRUCT' 中,我也不知道哪种方法更好。
DICT_ENTRY: glib->GHashTable, ????, dbus->a{??}
参考 STRUCT 中 `?' 的示例,下面我们演示了 a{ss} 的传递代码。其中 DBUS_TYPE_G_STRING_STRING_HASHTABLE,是库帮我们定义的:
DBUS_TYPE_G_STRING_STRING_HASHTABLE (dbus_g_type_get_map ("GHashTable", G_TYPE_STRING, G_TYPE_STRING))
代码同样分为三大块,与 STUCT 流程相似。
int send_recv_dict(DBusGProxy *proxy)
{
char *method;
GHashTable *table, *ret;
GHashTableIter iter;
gpointer key, value;
GError *error = NULL;
char *str[3];
table = g_hash_table_new(NULL, NULL);
str[0] = "apple";
str[1] = "banana";
str[2] = "cherry";
g_hash_table_insert(table, "a", str[0]);
g_hash_table_insert(table, "b", str[1]);
g_hash_table_insert(table, "c", str[2]);
method = "DictPrint";
if (!dbus_g_proxy_call(proxy, method, &error,
DBUS_TYPE_G_STRING_STRING_HASHTABLE, table,
G_TYPE_INVALID,
DBUS_TYPE_G_STRING_STRING_HASHTABLE, &ret,
G_TYPE_INVALID)) {
g_printerr("call %s failed: %s\n", method, error->message);
g_error_free(error);
error = NULL;
return -1;
}
g_print("receive: dictionary\n");
g_hash_table_iter_init(&iter, ret);
while (g_hash_table_iter_next(&iter, &key, &value)) {
g_print("key: %s, %s\n", (char *)key, (char *)value);
}
g_print("=================================\n\n");
g_hash_table_unref(table);
g_hash_table_unref(ret);
return 0;
}
VARIANT: glib->GValue, G_TYPE_VALUE, dbus->'v'
VARIANT 是一个通用的容器,它可以装任意数据类型。如:所有基本类型,ARRAY, STRUCT, DICT_ENTRY 甚至容纳自身。以下代码演示了装 INT_ARRAY 和 STRUCT 的 VARIANT 的传递,它们分为两个函数。
int send_recv_variant(DBusGProxy *proxy)
{
char *method;
method = "VariantPrint";
send_recv_variant_int_array(proxy, method);
send_recv_variant_struct(proxy, method);
return 0;
}
使用 VARINAT 传递 INT_ARRAY
重点就是如何将 INT_ARRAY 装入 GValue 中。这里的办法是,先产生一个容器,然后从容器中获取指针进行赋值。试这个的时候费了我老大劲了-_-!。注意,服务进程返回的是 DICT_ENTRY 类型的数据。
int send_recv_variant_int_array(DBusGProxy *proxy, char *method)
{
GError *error = NULL;
GValue gval = G_VALUE_INIT;
GValue ret = G_VALUE_INIT;
GHashTable *table;
GHashTableIter iter;
gpointer key, value;
GArray *garray;
gint i, j;
g_value_init(&gval, DBUS_TYPE_G_INT_ARRAY);
g_value_take_boxed(&gval, dbus_g_type_specialized_construct(DBUS_TYPE_G_INT_ARRAY));
garray = g_value_get_boxed(&gval);
for (i = 0; i < 6; i++) {
j = i + 1;
g_array_append_val(garray, j);
}
if (!dbus_g_proxy_call(proxy, method, &error,
G_TYPE_VALUE, &gval,
G_TYPE_INVALID,
G_TYPE_VALUE, &ret,
G_TYPE_INVALID)) {
g_printerr("call %s failed: %s\n", method, error->message);
g_error_free(error);
error = NULL;
return -1;
}
g_print("receive variant:\n");
table = g_value_get_boxed(&ret);
g_hash_table_iter_init(&iter, table);
while (g_hash_table_iter_next(&iter, &key, &value)) {
g_print("key: %s, %s\n", (char *)key, (char *)value);
}
g_print("\n=================================\n\n");
return 0;
}
使用 VARINAT 传递 INT_STRUCT
重点就是如何将 STRUCT 装入 GValue 中。这里出现了构造 STRUCT 的第二种方法。注意,服务进程返回的是 DICT_ENTRY 类型的数据。
int send_recv_variant_struct(DBusGProxy *proxy, char *method)
{
GError *error = NULL;
GValue gval = G_VALUE_INIT;
GValue ret = G_VALUE_INIT;
GHashTable *table;
GHashTableIter iter;
gpointer key, value;
g_value_init(&gval, DBUS_STRUCT_STRING_INT_DOUBLE_BOOLEAN);
g_value_take_boxed(&gval, dbus_g_type_specialized_construct(DBUS_STRUCT_STRING_INT_DOUBLE_BOOLEAN));
dbus_g_type_struct_set(&gval, 0, "fan",
1, 24,
2, 70.1,
3, FALSE, G_MAXUINT);
if (!dbus_g_proxy_call(proxy, method, &error,
G_TYPE_VALUE, &gval,
G_TYPE_INVALID,
G_TYPE_VALUE, &ret,
G_TYPE_INVALID)) {
g_printerr("call %s failed: %s\n", method, error->message);
g_error_free(error);
error = NULL;
return -1;
}
g_print("receive variant:\n");
table = g_value_get_boxed(&ret);
g_hash_table_iter_init(&iter, table);
while (g_hash_table_iter_next(&iter, &key, &value)) {
g_print("key: %s, %s\n", (char *)key, (char *)value);
}
g_print("\n=================================\n\n");
return 0;
}
advanced_data_deliver_test_c.c
/**
* @file advanced_data_deliver_test_c.c
* @brief
* @author Airead Fan
* @date 2012/03/23 11:28:29
*/
#include
#include
#include
#include
#define METHOD_STRLEN 128
int send_recv_dict(DBusGProxy *proxy)
{
char *method;
GHashTable *table, *ret;
GHashTableIter iter;
gpointer key, value;
GError *error = NULL;
char *str[3];
table = g_hash_table_new(NULL, NULL);
str[0] = "apple";
str[1] = "banana";
str[2] = "cherry";
g_hash_table_insert(table, "a", str[0]);
g_hash_table_insert(table, "b", str[1]);
g_hash_table_insert(table, "c", str[2]);
method = "DictPrint";
if (!dbus_g_proxy_call(proxy, method, &error,
DBUS_TYPE_G_STRING_STRING_HASHTABLE, table,
G_TYPE_INVALID,
DBUS_TYPE_G_STRING_STRING_HASHTABLE, &ret,
G_TYPE_INVALID)) {
g_printerr("call %s failed: %s\n", method, error->message);
g_error_free(error);
error = NULL;
return -1;
}
g_print("receive: dictionary\n");
g_hash_table_iter_init(&iter, ret);
while (g_hash_table_iter_next(&iter, &key, &value)) {
g_print("key: %s, %s\n", (char *)key, (char *)value);
}
g_print("=================================\n\n");
g_hash_table_unref(table);
g_hash_table_unref(ret);
return 0;
}
int send_recv_int_array(DBusGProxy *proxy)
{
char *method;
GError *error;
GArray *garray, *ret;
gint i, j;
garray = g_array_new (FALSE, FALSE, sizeof (gint));
for (i = 0; i < 6; i++) {
j = i + 1;
g_array_append_val(garray, j);
}
method = "IntArrayPrint";
if (!dbus_g_proxy_call(proxy, method, &error,
DBUS_TYPE_G_INT_ARRAY, garray,
G_TYPE_INVALID,
DBUS_TYPE_G_INT_ARRAY, &ret,
G_TYPE_INVALID)) {
g_printerr("call %s failed: %s\n", method, error->message);
g_error_free(error);
error = NULL;
return -1;
}
g_print("receive int array:\n");
for (i = 0; i < ret->len; i++) {
g_print("%d ", g_array_index(ret, gint, i));
}
g_print("\n=================================\n\n");
return 0;
}
#define DBUS_STRUCT_STRING_INT_DOUBLE_BOOLEAN ( \
dbus_g_type_get_struct ( "GValueArray", G_TYPE_STRING, G_TYPE_INT, \
G_TYPE_DOUBLE, G_TYPE_BOOLEAN, G_TYPE_INVALID))
int send_recv_struct(DBusGProxy *proxy)
{
char *method;
GError *error = NULL;
GValueArray *ret, *send_array;
GValue *gval;
GValue send_gval[4] = `0`;
int i;
g_value_init (&send_gval[0], G_TYPE_STRING);
g_value_set_string(&send_gval[0], "fan");
g_value_init (&send_gval[1], G_TYPE_INT);
g_value_set_int(&send_gval[1], 24);
g_value_init (&send_gval[2], G_TYPE_DOUBLE);
g_value_set_double(&send_gval[2], 70.2);
g_value_init (&send_gval[3], G_TYPE_BOOLEAN);
g_value_set_boolean(&send_gval[3], FALSE);
send_array = g_value_array_new(0);
for (i = 0; i < 4; i++) {
send_array = g_value_array_append(send_array, &send_gval[i]);
}
method = "StructPrint";
if (!dbus_g_proxy_call(proxy, method, &error,
DBUS_STRUCT_STRING_INT_DOUBLE_BOOLEAN, send_array,
G_TYPE_INVALID,
DBUS_STRUCT_STRING_INT_DOUBLE_BOOLEAN, &ret,
G_TYPE_INVALID)) {
g_printerr("call %s failed: %s\n", method, error->message);
g_error_free(error);
error = NULL;
return -1;
}
g_print("receive struct:\n");
for (i = 0; i < ret->n_values; i++) {
gval = g_value_array_get_nth(ret, i);
if (G_VALUE_TYPE(gval) == G_TYPE_STRING) {
g_print("%s\n", g_value_get_string(gval));
} else if (G_VALUE_TYPE(gval) == G_TYPE_DOUBLE) {
g_print("%f\n", g_value_get_double(gval));
} else if (G_VALUE_TYPE(gval) == G_TYPE_INT) {
g_print("%d\n", g_value_get_int(gval));
} else if (G_VALUE_TYPE(gval) == G_TYPE_BOOLEAN) {
g_print("%d\n", g_value_get_boolean(gval));
}
}
g_print("\n=================================\n\n");
return 0;
}
int send_recv_variant_int_array(DBusGProxy *proxy, char *method)
{
GError *error = NULL;
GValue gval = G_VALUE_INIT;
GValue ret = G_VALUE_INIT;
GHashTable *table;
GHashTableIter iter;
gpointer key, value;
GArray *garray;
gint i, j;
g_value_init(&gval, DBUS_TYPE_G_INT_ARRAY);
g_value_take_boxed(&gval, dbus_g_type_specialized_construct(DBUS_TYPE_G_INT_ARRAY));
garray = g_value_get_boxed(&gval);
for (i = 0; i < 6; i++) {
j = i + 1;
g_array_append_val(garray, j);
}
if (!dbus_g_proxy_call(proxy, method, &error,
G_TYPE_VALUE, &gval,
G_TYPE_INVALID,
G_TYPE_VALUE, &ret,
G_TYPE_INVALID)) {
g_printerr("call %s failed: %s\n", method, error->message);
g_error_free(error);
error = NULL;
return -1;
}
g_print("receive variant:\n");
table = g_value_get_boxed(&ret);
g_hash_table_iter_init(&iter, table);
while (g_hash_table_iter_next(&iter, &key, &value)) {
g_print("key: %s, %s\n", (char *)key, (char *)value);
}
g_print("\n=================================\n\n");
return 0;
}
int send_recv_variant_struct(DBusGProxy *proxy, char *method)
{
GError *error = NULL;
GValue gval = G_VALUE_INIT;
GValue ret = G_VALUE_INIT;
GHashTable *table;
GHashTableIter iter;
gpointer key, value;
g_value_init(&gval, DBUS_STRUCT_STRING_INT_DOUBLE_BOOLEAN);
g_value_take_boxed(&gval, dbus_g_type_specialized_construct(DBUS_STRUCT_STRING_INT_DOUBLE_BOOLEAN));
dbus_g_type_struct_set(&gval, 0, "fan",
1, 24,
2, 70.1,
3, FALSE, G_MAXUINT);
if (!dbus_g_proxy_call(proxy, method, &error,
G_TYPE_VALUE, &gval,
G_TYPE_INVALID,
G_TYPE_VALUE, &ret,
G_TYPE_INVALID)) {
g_printerr("call %s failed: %s\n", method, error->message);
g_error_free(error);
error = NULL;
return -1;
}
g_print("receive variant:\n");
table = g_value_get_boxed(&ret);
g_hash_table_iter_init(&iter, table);
while (g_hash_table_iter_next(&iter, &key, &value)) {
g_print("key: %s, %s\n", (char *)key, (char *)value);
}
g_print("\n=================================\n\n");
return 0;
}
int send_recv_variant(DBusGProxy *proxy)
{
char *method;
method = "VariantPrint";
send_recv_variant_int_array(proxy, method);
send_recv_variant_struct(proxy, method);
return 0;
}
int main(int argc, char *argv[])
{
DBusGConnection *connection;
GError *error = NULL;
DBusGProxy *proxy;
g_type_init();
/* conect system connection and get proxy */
connection = dbus_g_bus_get(DBUS_BUS_SESSION, &error);
if (connection == NULL) {
g_printerr("get system bus failed: %s\n", error->message);
g_error_free(error);
return -1;
}
/* get proxy */
proxy = dbus_g_proxy_new_for_name(connection,
"airead.fan.AdvancedDataType",
"/airead/fan/AdvancedDataType",
"airead.fan.AdvancedDataType");
send_recv_dict(proxy);
send_recv_int_array(proxy);
send_recv_struct(proxy);
send_recv_variant(proxy);
return 0;
}
有些东西实际上没用,我也懒得去了。
CC = gcc CFLAGS = -Wall -g CFLAGS += $(shell pkg-config --cflags glib-2.0 ) CFLAGS += $(shell pkg-config --cflags dbus-glib-1) #CFLAGS += $(shell pkg-config --cflags gtk+-2.0) LDFLAGS = LDFLAGS += $(shell pkg-config --libs glib-2.0) LDFLAGS += $(shell pkg-config --libs dbus-glib-1) #LDFLAGS += $(shell pkg-config --libs gtk+-2.0) SOURCE = $(wildcard *.c) TARGETS := $(patsubst %.c, %, $(SOURCE)) TARGETS_OUT = common_marshaler basic_data TARGETS := $(filter-out $(TARGETS_OUT), $(TARGETS)) TARGETS := $(addsuffix .out, $(TARGETS)) %.out: %.c @echo CC $< -o $@ @$(CC) $< common_marshaler.c basic_data.c $(CFLAGS) -o $@ $(LDFLAGS) .PHONY: all clean test marshaler all: $(TARGETS) marshaler: glib-genmarshal --prefix _common_marshal --header common_marshaler.list > common_marshaler.h glib-genmarshal --prefix _common_marshal --body common_marshaler.list > common_marshaler.c dbus-binding-tool --prefix=airead_fan --mode=glib-server all_basic_data_deliver_server.xml > all_basic_data_deliver_server.h clean: rm -f *~ a.out *.o $(TARGETS) core.* test: @echo TARGETS: $(TARGETS)