Add Memory.size/0

lib/orb/instruction.ex

@@ -39,6 +39,7 @@ defmodule Orb.Instruction do
   def global_set(type, global_name, value),
     do: new(:global_effect, {:global_set, global_name, type}, [value])
 
+  def memory_size(), do: new(:memory, :size, [])
   def memory_grow(value), do: new(:memory, :grow, [value])
 
   defp type_check_operands(type, operation, operands) do

lib/orb/memory.ex

@@ -114,10 +114,27 @@ defmodule Orb.Memory do
     Orb.Instruction.new(primitive_type, store_instruction, [address, value])
   end
 
+  @doc """
+  Returns the number of pages the memory instance currently has. Each page is 64KiB.
+
+  To increase the number of pages call `grow!/1`.
+
+  https://developer.mozilla.org/en-US/docs/WebAssembly/Reference/Memory/Size
+
+  ```elixir
+  Memory.size()
+  ```
+  """
+  def size() do
+    Orb.Instruction.memory_size()
+  end
+
   @doc """
   Increases the size of the memory instance by a specified number of pages. Each page is 64KiB.
 
-  It returns the previous size of memory, in pages, if the operation was successful, or returns -1 if the operation failed.
+  Note: only `0` and `1` are supported in today’s runtimes.
+
+  It returns the previous size of memory in pages if the operation was successful, or returns -1 if the operation failed.
 
   https://developer.mozilla.org/en-US/docs/WebAssembly/Reference/Memory/Grow
 

test/memory_test.exs

@@ -51,11 +51,14 @@ defmodule MemoryTest do
            """
   end
 
-  test "grow!/1" do
+  test "size/1 and grow!/1" do
     defmodule Grow do
       use Orb
 
       defw grow() do
+        Memory.size()
+        :drop
+
         Memory.grow!(1)
         :drop
 
@@ -70,6 +73,8 @@ defmodule MemoryTest do
     assert Orb.to_wat(Grow) == """
            (module $Grow
              (func $grow (export "grow")
+               (memory.size)
+               drop
                (memory.grow (i32.const 1))
                drop
                (memory.grow (i32.const 0))