Add __wasm_data_defs__/1 to allow dynamic data to be initialized

lib/orb.ex

@@ -475,6 +475,9 @@ defmodule Orb do
             def __wasm_body__(_), do: []
             defoverridable __wasm_body__: 1
 
+            def __wasm_data_defs__(_), do: []
+            defoverridable __wasm_data_defs__: 1
+
             # TODO: rename these to orb_ prefix instead of wasm_ ?
             Module.put_attribute(
               __MODULE__,
@@ -614,7 +617,7 @@ defmodule Orb do
         end
 
         def __wasm_module__() do
-          %{body: body, constants: constants, global_definitions: global_definitions} =
+          %{body: body, constants: constants, global_defs: global_defs, data_defs: data_defs} =
             Orb.Compiler.run(__MODULE__, @wasm_globals)
 
           memory = Memory.new(@wasm_memory, constants)
@@ -624,11 +627,11 @@ defmodule Orb do
             types: @wasm_types |> Enum.reverse() |> List.flatten(),
             table_size: @wasm_table_allocations |> List.flatten() |> length(),
             imports: @wasm_imports |> Enum.reverse() |> List.flatten(),
-            globals: global_definitions,
+            globals: global_defs,
             memory: memory,
             constants: constants,
             body: body,
-            data: @wasm_section_data |> Enum.reverse()
+            data: Enum.reverse(@wasm_section_data) ++ data_defs
           )
         end
 

lib/orb/compiler.ex

@@ -12,17 +12,24 @@ defmodule Orb.Compiler do
     Orb.Constants.__begin()
 
     # Each global is expanded, possibly looking up with the current compiler context begun above.
-    global_definitions =
+    global_defs =
       globals |> Enum.reverse() |> List.flatten() |> Enum.map(&Orb.Global.expand!/1)
 
     body = Orb.ModuleDefinition.get_body_of(mod)
 
+    data_defs = mod.__wasm_data_defs__(nil)
+
     Process.delete({Orb, :global_types})
 
     # We’re done. Get all the constant strings that were actually used.
     constants = Orb.Constants.__read()
 
-    %{body: body, constants: constants, global_definitions: global_definitions}
+    %{
+      body: body,
+      constants: constants,
+      global_defs: global_defs,
+      data_defs: data_defs
+    }
   after
     Orb.Constants.__cleanup()
   end

lib/orb/data.ex

@@ -2,7 +2,7 @@ defmodule Orb.Data do
   @moduledoc false
 
   # TODO: remove nul_terminated
-  defstruct [:offset, :value, :nul_terminated]
+  defstruct [:offset, :value, nul_terminated: false]
 
   defimpl Orb.ToWat do
     def to_wat(%Orb.Data{offset: offset, value: value, nul_terminated: nul_terminated}, indent) do

lib/orb/memory.ex

@@ -57,7 +57,7 @@ defmodule Orb.Memory do
   @doc "Initializes data in memory. In Wat is `(data …)`"
   defmacro initial_data!(offset, value) do
     quote bind_quoted: [offset: offset, value: value] do
-      @wasm_section_data %Orb.Data{offset: offset, value: value, nul_terminated: false}
+      @wasm_section_data %Orb.Data{offset: offset, value: value}
     end
   end