[srv.init] Rework init to use module iterator

Init now uses a module iterator that facilitates filtering on module
type.

src/user/srv.init/modules.h

@@ -2,10 +2,61 @@
 /// \file modules.h
 /// Routines for loading initial argument modules
 
-namespace modules {
+#include "j6/types.h"
+#include "init_args.h"
+#include "pointer_manipulation.h"
 
-/// Load all modules
-/// \arg address  The physical address of the first page of modules
-void load_all(uintptr_t address);
 
-} // namespace modules
+class module_iterator
+{
+public:
+    using type = kernel::init::module_type;
+    using module = kernel::init::module;
+
+    module_iterator(const module *m, type t = type::none) :
+        m_mod {m}, m_type {t} {}
+
+    const module * operator++();
+    const module * operator++(int);
+
+    bool operator==(const module* m) const { return m == m_mod; }
+    bool operator!=(const module* m) const { return m != m_mod; }
+    bool operator==(const module_iterator &i) const { return i.m_mod == m_mod; }
+    bool operator!=(const module_iterator &i) const { return i.m_mod != m_mod; }
+
+    const module & operator*() const { return *m_mod; }
+    operator const module & () const { return *m_mod; }
+    const module * operator->() const { return m_mod; }
+
+    // Allow iterators to be used in for(:) statments
+    module_iterator & begin() { return *this; }
+    module_iterator end() const { return nullptr; }
+
+private:
+    module const * m_mod;
+    type m_type;
+};
+
+class modules
+{
+public:
+    using type = kernel::init::module_type;
+    using iterator = module_iterator;
+
+    static modules load_modules(
+        uintptr_t address,
+        j6_handle_t system,
+        j6_handle_t self);
+
+    iterator of_type(type t) const { return iterator {m_root, t}; }
+
+    iterator begin() const { return iterator {m_root}; }
+    iterator end() const { return nullptr; }
+
+private:
+    using module = kernel::init::module;
+
+    modules(const module* root) : m_root {root} {}
+
+    const module *m_root;
+};