Improve xml output

lib/components_guide/wasm/examples/podcast_feed/podcast_feed.ex

@@ -44,6 +44,12 @@ defmodule ComponentsGuide.Wasm.PodcastFeed do
   # Global.import()
   # wasm_import(:datasource, populate_episode_at_index: Orb.DSL.funcp(name: :datasource_populate_episode, params: I32))
 
+  defmodule StdOut do
+    use Orb.Import
+
+    defw(flush(read_ptr: I32.UnsafePointer, byte_count: I32), nil)
+  end
+
   defmodule Datasource do
     use Orb.Import
 
@@ -53,6 +59,10 @@ defmodule ComponentsGuide.Wasm.PodcastFeed do
     defw(write_episode_id(episode_id: EpisodeID, write_ptr: I32.UnsafePointer), I32)
     defw(write_episode_title(episode_id: EpisodeID, write_ptr: I32.UnsafePointer), I32)
     # defw(write_episode_author(episode_id: EpisodeID, write_ptr: I32.UnsafePointer), I32)
+    # TODO: what happens if it wants to write more than the memory available?
+    # Yet another reason to have arenas for title, description, etc.
+    # Or have to use a proper malloc approach.
+    # Or have to flush before each write, and rewind bump_offset to beginning.
     defw(write_episode_description(episode_id: EpisodeID, write_ptr: I32.UnsafePointer), I32)
     defw(write_episode_link_url(episode_id: EpisodeID, write_ptr: I32.UnsafePointer), I32)
     defw(write_episode_mp3_url(episode_id: EpisodeID, write_ptr: I32.UnsafePointer), I32)
@@ -72,6 +82,10 @@ defmodule ComponentsGuide.Wasm.PodcastFeed do
   importw(Datasource, :datasource)
 
   # SilverOrb.Arena.def(DatasourceArena, pages: 1)
+  # Used by url attribute in <enclosure url="…">
+  SilverOrb.Arena.def(WriteBuffer, pages: 1)
+  # Attributes must have <&" escaped.
+  SilverOrb.Arena.def(EscapeXMLBuffer, pages: byte_size("&amp;"))
 
   # There are a few ways to implement this:
   # 1. Pass every episode in as some sort of data structure. e.g.
@@ -134,7 +148,7 @@ defmodule ComponentsGuide.Wasm.PodcastFeed do
     build! do
       ~S[<?xml version="1.0" encoding="UTF-8"?>\n]
 
-      XML.open(:rss,
+      XML.open_newline(:rss,
         version: "2.0",
         "xmlns:itunes": "http://www.itunes.com/dtds/podcast-1.0.dtd",
         "xmlns:googleplay": "http://www.google.com/schemas/play-podcasts/1.0",
@@ -146,7 +160,7 @@ defmodule ComponentsGuide.Wasm.PodcastFeed do
       # This then causes the module to clear its local memory, resetting the bump
       # offset to the very beginning again.
 
-      XML.open(:channel)
+      XML.open_newline(:channel)
       XML.element(:title, @title)
 
       XML.element(:description, @description)

lib/components_guide/wasm/examples/podcast_feed/xml_formatter.ex

@@ -29,6 +29,13 @@ defmodule ComponentsGuide.Wasm.PodcastFeed.XMLFormatter do
     ])
   end
 
+  def open_newline(tag, attributes \\ []) when is_atom(tag) do
+    Orb.InstructionSequence.new(:memory_effect, [
+      open(tag, attributes),
+      append!(ascii: ?\n)
+    ])
+  end
+
   def close_newline(tag) when is_atom(tag) do
     xml_close_newline(Orb.DSL.const(Atom.to_string(tag)))
   end

test/components_guide/wasm/examples/podcast_feed_test.exs

@@ -101,6 +101,9 @@ defmodule ComponentsGuide.Wasm.PodcastFeed.Test do
     assert "Episode 2" = xml_text_content(item2, "//itunes:title[1]")
     assert "Description for 1" = xml_text_content(item1, "//description[1]")
     assert "Description for 2" = xml_text_content(item2, "//description[1]")
+
+    # <enclosure url="${bunnyEpisodeURL(episodeID)}" length="${feedItem.mp3ByteCount}" type="audio/mpeg"/>
+    assert "Description for 2" = xml_xpath(item1, "//enclosure[1]")
   end
 
   defp xml_parse(xml) do
@@ -131,7 +134,7 @@ defmodule ComponentsGuide.Wasm.PodcastFeed.Test do
 
   defp do_xml_text_content(_, acc), do: acc
 
-  @tag :skip
+  # @tag :skip
   test "output optimized wasm" do
     path_wasm = Path.join(__DIR__, "podcast_feed_xml.wasm")
     path_wat = Path.join(__DIR__, "podcast_feed_xml.wat")
@@ -142,10 +145,10 @@ defmodule ComponentsGuide.Wasm.PodcastFeed.Test do
     System.cmd("wasm-opt", [path_wasm, "-o", path_opt_wasm, "-O"])
 
     %{size: size} = File.stat!(path_wasm)
-    assert size == 2419
+    assert size == 2418
 
     %{size: size} = File.stat!(path_opt_wasm)
-    assert size == 1868
+    assert size == 1909
 
     {wat, 0} = System.cmd("wasm2wat", [path_wasm])
     File.write!(path_wat, wat)