Improve precompiled downloads (#94)

.gitignore

@@ -30,3 +30,6 @@ xla-*.tar
 
 # Output from compilations within Docker
 /builds/output/
+
+# Archive checksums file
+/checksum.txt

README.md

@@ -76,12 +76,6 @@ The target triplet describing the target platform, such as `aarch64-linux-gcc`.
 this target is inferred for the host, however you may want to override this when cross-compiling
 the project using Nerves.
 
-#### `XLA_HTTP_HEADERS`
-
-Headers to use when querying and downloading the precompiled archive. By default the
-requests are sent to GitHub, unless `XLA_ARCHIVE_URL` specifies otherwise. The headers
-should be a list following this format: `Key1: Value1; Key2: value2`.
-
 ## Building from source
 
 > Note: currently only macOS and Linux is supported. When on Windows, the best option

lib/mix/tasks/xla.checksum.ex

@@ -0,0 +1,41 @@
+defmodule Mix.Tasks.Xla.Checksum do
+  @moduledoc """
+  Generates a checksum file for all precompiled artifacts.
+  """
+
+  use Mix.Task
+
+  @impl true
+  def run(_args) do
+    XLA.Utils.start_inets_profile()
+
+    Mix.shell().info("Downloading and computing checksums...")
+
+    checksums =
+      XLA.precompiled_files()
+      |> Task.async_stream(
+        fn {filename, url} ->
+          {filename, download_checksum!(url)}
+        end,
+        timeout: :infinity,
+        ordered: false
+      )
+      |> Map.new(fn {:ok, {filename, checksum}} -> {filename, checksum} end)
+
+    XLA.write_checksums!(checksums)
+
+    Mix.shell().info("Checksums written")
+  after
+    XLA.Utils.stop_inets_profile()
+  end
+
+  defp download_checksum!(url) do
+    case XLA.Utils.download(url, %XLA.Checksumer{}) do
+      {:ok, checksum} ->
+        checksum
+
+      {:error, message} ->
+        Mix.raise("failed to download archive from #{url}, reason: #{message}")
+    end
+  end
+end

lib/mix/tasks/xla.info.ex

@@ -11,7 +11,7 @@ defmodule Mix.Tasks.Xla.Info do
   end
 
   def run(["release_tag"]) do
-    Mix.shell().info(XLA.release_tag())
+    Mix.shell().info("v" <> XLA.version())
   end
 
   def run(["build_archive_dir"]) do