[Feature] Adds importable memory.

lib/orb/import.ex

@@ -80,6 +80,12 @@ defmodule Orb.Import do
     end
   end
 
+  defmacro register_memory(global, namespace, min \\ nil) do
+    quote do
+      @wasm_imports [%Orb.Import{module: unquote(global), name: unquote(namespace), type: %Orb.Memory{is_imported?: true, min: unquote(min)}}]
+    end
+  end
+
   defimpl Orb.ToWat do
     def to_wat(%Orb.Import{module: nil, name: name, type: type}, indent) do
       [indent, ~S|(import "|, to_string(name), ~S|" |, Orb.ToWat.to_wat(type, ""), ?)]

lib/orb/memory.ex

@@ -3,7 +3,7 @@ defmodule Orb.Memory do
   Work with memory: load, store, declare pages & initial data.
   """
 
-  defstruct name: "", min: 0, exported_name: "memory"
+  defstruct name: "", min: 0, exported_name: "memory", is_imported?: false
 
   @doc false
   def new(page_definitions, constants)
@@ -186,7 +186,7 @@ defmodule Orb.Memory do
   end
 
   defimpl Orb.ToWat do
-    def to_wat(%Orb.Memory{min: min}, indent) do
+    def to_wat(%Orb.Memory{min: min, is_imported?: is_imported?}, indent) when not is_imported? do
       [
         indent,
         ~S{(memory (export "memory")},
@@ -198,6 +198,19 @@ defmodule Orb.Memory do
         "\n"
       ]
     end
+
+    def to_wat(%Orb.Memory{is_imported?: true, name: name, min: min}, indent) do
+      [
+        indent,
+        "(memory",
+        to_string(name),
+        case min do
+          nil -> []
+          min when min >= 0 -> [" ", to_string(min)]
+        end,
+        ")",
+      ]
+    end
   end
 
   defimpl Orb.ToWasm do

test/import_test.exs

@@ -56,4 +56,19 @@ defmodule ImportTest do
            )
            """ = Orb.to_wat(ImportsExample)
   end
+
+  defmodule ImportsGlobal do
+    use Orb
+
+    Orb.Import.register_memory(:env, :memory, 1)
+  end
+
+  test "importing memory should work" do
+
+    assert """
+           (module $ImportsGlobal
+             (import "env" "memory" (memory 1))
+           )
+           """ = Orb.to_wat(ImportsGlobal)
+  end
 end