WindowsDevice: Add GetDeviceInterfaceList function and NullTerminatedStringList template.

Source/Core/Common/WindowsDevice.cpp

@@ -83,6 +83,36 @@ std::optional<std::wstring> GetDeviceInterfaceStringProperty(LPCWSTR iface,
                            DEVPROP_TYPE_STRING);
 }
 
+NullTerminatedStringList<WCHAR> GetDeviceInterfaceList(LPGUID iface_class_guid, DEVINSTID device_id,
+                                                       ULONG flags)
+{
+  while (true)
+  {
+    ULONG list_size = 0;
+    const auto size_result =
+        CM_Get_Device_Interface_List_Size(&list_size, iface_class_guid, device_id, flags);
+    if (size_result != CR_SUCCESS || list_size == 0)
+      list_size = 1;
+
+    auto buffer = std::make_unique_for_overwrite<WCHAR[]>(list_size);
+    const auto list_result =
+        CM_Get_Device_Interface_List(iface_class_guid, device_id, buffer.get(), list_size, flags);
+
+    // "A new device can be added to the system causing the size returned to no longer be valid."
+    // Microsoft recommends trying again in a loop.
+    if (list_result == CR_BUFFER_SMALL)
+      continue;
+
+    if (list_result != CR_SUCCESS)
+    {
+      ERROR_LOG_FMT(COMMON, "CM_Get_Device_Interface_List: {}", list_result);
+      buffer[0] = 0;
+    }
+
+    return {std::move(buffer)};
+  }
+}
+
 }  // namespace Common
 
 #endif

Source/Core/Common/WindowsDevice.h

@@ -5,6 +5,8 @@
 
 #ifdef _WIN32
 
+#include <iterator>
+#include <memory>
 #include <optional>
 #include <string>
 
@@ -32,6 +34,47 @@ std::optional<std::wstring> GetDevNodeStringProperty(DEVINST device,
 std::optional<std::wstring> GetDeviceInterfaceStringProperty(LPCWSTR iface,
                                                              const DEVPROPKEY* requested_property);
 
+// Allows iterating null-separated/terminated string lists returned by the Windows API.
+template <typename T>
+struct NullTerminatedStringList
+{
+  class Iterator
+  {
+    friend NullTerminatedStringList;
+
+  public:
+    constexpr T* operator*() { return m_ptr; }
+
+    constexpr Iterator& operator++()
+    {
+      m_ptr += std::basic_string_view(m_ptr).size() + 1;
+      return *this;
+    }
+
+    constexpr Iterator operator++(int)
+    {
+      const auto result{*this};
+      ++*this;
+      return result;
+    }
+
+    constexpr bool operator==(std::default_sentinel_t) const { return *m_ptr == T{}; }
+
+  private:
+    constexpr Iterator(T* ptr) : m_ptr{ptr} {}
+
+    T* m_ptr;
+  };
+
+  constexpr auto begin() const { return Iterator{list.get()}; }
+  constexpr auto end() const { return std::default_sentinel; }
+
+  std::unique_ptr<T[]> list;
+};
+
+NullTerminatedStringList<WCHAR> GetDeviceInterfaceList(LPGUID iface_class_guid, DEVINSTID device_id,
+                                                       ULONG flags);
+
 }  // namespace Common
 
 #endif