c - 如何解析 "a(oa{sv})"dbus类型？

Question

我正在解析对“net.connman.Manager.GetServices”函数的响应，它看起来像这样:

<method name="GetServices">
    <arg name="services" type="a(oa{sv})" direction="out"/>
</method>

这是一个相当复杂的结构。

到目前为止我得到的是:

GVariant* result = ... // response containing data
GVariantIter* iter1;
g_variant_get( result, "a(oa{sv})", &iter1 );

GVariant* child = g_variant_iter_next_value( iter1 );
while ( nullptr != child )
{
    gchar* string;
    GVariant* data;
    g_variant_get( child, "(oa{sv})", &string, &data );

    // how to access inner array?

    g_variant_unref( child );
    child = g_variant_iter_next_value( iter1 );
}

g_variant_iter_free( iter1 );

那么，我该如何访问内部数组数据呢？

我试过这个: GVariantIter* iter2; g_variant_get( 数据, "a{sv}", &iter2 ); GVariant* child2 = g_variant_iter_next_value( iter2 );

但它因一些对齐错误而失败:

**
GLib:ERROR:../../glib-2.48.2/glib/gvarianttypeinfo.c:163:g_variant_type_info_check: assertion failed: (info->alignment == 0 || info->alignment == 1 || info->alignment == 3 || info->alignment == 7)
Aborted

Answer 1

data 应具有类型 GVariantIter*，而不是 GVariant*，根据 GVariant Format Strings 的文档(您将 GVariant 格式字符串作为第二个参数传递给 g_variant_get())。

您可以使用 g_variant_iter_loop() 大大简化代码虽然:

/* Compile with: `gcc `pkg-config --cflags --libs glib-2.0 gio-2.0` -o test test.c`.
 * Public domain. */

#include <glib.h>
#include <gio/gio.h>

int
main (void)
{
  g_autoptr(GVariant) result = g_variant_new_parsed ("@a(oa{sv}) [('/', { 'hello': <'test'>})]");

  g_autoptr(GVariantIter) iter1 = NULL;
  g_variant_get (result, "a(oa{sv})", &iter1);

  const gchar *string;
  g_autoptr(GVariantIter) iter2 = NULL;

  while (g_variant_iter_loop (iter1, "(&oa{sv})", &string, &iter2))
    {
      const gchar *key;
      g_autoptr(GVariant) value = NULL;

      while (g_variant_iter_loop (iter2, "{&sv}", &key, &value))
        g_message ("%s, %s:%p", string, key, value);
    }

  return 0;
}