image: Actually make backends registerable

3 files changed, 24 insertions, 15 deletions

diff --git a/image/backends/README.rst b/image/backends/README.rst
index acb44ef..e2a91a7 100644
--- a/image/backends/README.rst
+++ b/image/backends/README.rst
@@ -41,9 +41,10 @@ Design
 
 Image creation backends shall derive from the Horizon::Image::BasicBackend
 class.  Concrete backends can exist in any namespace.  To be used with the
-Image Creation utility, the backend must be registered in the ``basic.cc``
-file along with a unique Type Code.  This Type Code can then be passed to
-the Image Creation utility with the ``-t`` parameter for use.
+Image Creation utility, the backend must be registered using the static
+``BackendManager::register_backend`` function, using a unique Type Code.
+This Type Code can then be passed to the Image Creation utility with the
+``-t`` parameter for use.
 
 The Horizon::Image::BasicBackend is an abstract (pure virtual) class that
 has a single method that you must implement: ``create()``.  This will be
diff --git a/image/backends/basic.cc b/image/backends/basic.cc
index dbe387c..bec3e41 100644
--- a/image/backends/basic.cc
+++ b/image/backends/basic.cc
@@ -20,10 +20,14 @@ std::vector<BackendDescriptor> known_backends = {
    {"squashfs", "Create a SquashFS image (.squashfs)", [](std::string, std::string){ return nullptr; } }
 };
 
-const std::vector<BackendDescriptor> BasicBackend::available_backends() {
+const std::vector<BackendDescriptor> BackendManager::available_backends() {
     return known_backends;
 }
 
+void BackendManager::register_backend(BackendDescriptor desc) {
+    known_backends.push_back(desc);
+}
+
 int BasicBackend::prepare() {
     /* The default implementation returns success immediately;
      * no preparation is required. */
diff --git a/image/backends/basic.hh b/image/backends/basic.hh
index 3181f69..95b94ae 100644
--- a/image/backends/basic.hh
+++ b/image/backends/basic.hh
@@ -19,14 +19,6 @@
 namespace Horizon {
 namespace Image {
 
-class BasicBackend;
-
-struct BackendDescriptor {
-    std::string type_code;
-    std::string description;
-    std::function<BasicBackend *(std::string, std::string)> creation_fn;
-};
-
 class BasicBackend {
 public:
     /*! Create the backend object.
@@ -53,9 +45,6 @@ public:
      */
     virtual int finalise();
 
-    /*! Returns a list of available backends. */
-    static const std::vector<BackendDescriptor> available_backends();
-
     /*! The intermediate directory which contains the sysroot the image
      *  should contain. */
     const std::string &ir_dir;
@@ -63,5 +52,20 @@ public:
     const std::string &out_path;
 };
 
+struct BackendDescriptor {
+    std::string type_code;
+    std::string description;
+    std::function<BasicBackend *(std::string, std::string)> creation_fn;
+};
+
+class BackendManager {
+public:
+    /*! Returns a list of available backends. */
+    static const std::vector<BackendDescriptor> available_backends();
+
+    /*! Register a new backend. */
+    static void register_backend(BackendDescriptor desc);
+};
+
 }
 }