Add feature registry header file

ift/feature_registry/BUILD

@@ -2,8 +2,9 @@ load("@rules_cc//cc:cc_library.bzl", "cc_library")
 load("@rules_cc//cc:cc_test.bzl", "cc_test")
 load("@rules_python//python:defs.bzl", "py_binary")
 
+# Can be used to generate feature_registry.h when there is an update to the csv.
 genrule(
-    name = "feature_registry_h",
+    name = "generate_feature_registry_h",
     srcs = [
         "@ift_spec//:feature-registry.csv",
     ],
@@ -18,8 +19,8 @@ genrule(
 
 cc_library(
     name = "feature_registry",
-    srcs = [
-        ":feature_registry_h",
+    hdrs = [
+        "feature_registry.h",
     ],
     visibility = [
         "//ift/encoder:__pkg__",

ift/feature_registry/feature_registry.h

@@ -0,0 +1,83 @@
+#ifndef IFT_FEATURE_REGISTRY_FEATURE_REGISTRY_H_
+#define IFT_FEATURE_REGISTRY_FEATURE_REGISTRY_H_
+
+#include "hb.h"
+#include "absl/base/no_destructor.h"
+#include "absl/container/flat_hash_set.h"
+
+namespace ift::feature_registry {
+
+static const absl::flat_hash_set<hb_tag_t>& DefaultFeatureTags() {
+  static const absl::NoDestructor<absl::flat_hash_set<hb_tag_t>> kDefaultFeatures((absl::flat_hash_set<hb_tag_t>) {
+    HB_TAG('a', 'b', 'v', 'f'),
+    HB_TAG('a', 'b', 'v', 'm'),
+    HB_TAG('a', 'b', 'v', 's'),
+    HB_TAG('a', 'k', 'h', 'n'),
+    HB_TAG('b', 'l', 'w', 'f'),
+    HB_TAG('b', 'l', 'w', 'm'),
+    HB_TAG('b', 'l', 'w', 's'),
+    HB_TAG('c', 'a', 'l', 't'),
+    HB_TAG('c', 'c', 'm', 'p'),
+    HB_TAG('c', 'f', 'a', 'r'),
+    HB_TAG('c', 'h', 'w', 's'),
+    HB_TAG('c', 'j', 'c', 't'),
+    HB_TAG('c', 'l', 'i', 'g'),
+    HB_TAG('c', 's', 'w', 'h'),
+    HB_TAG('c', 'u', 'r', 's'),
+    HB_TAG('d', 'i', 's', 't'),
+    HB_TAG('d', 'n', 'o', 'm'),
+    HB_TAG('d', 't', 'l', 's'),
+    HB_TAG('f', 'i', 'n', '2'),
+    HB_TAG('f', 'i', 'n', '3'),
+    HB_TAG('f', 'i', 'n', 'a'),
+    HB_TAG('f', 'l', 'a', 'c'),
+    HB_TAG('f', 'r', 'a', 'c'),
+    HB_TAG('h', 'a', 'l', 'f'),
+    HB_TAG('h', 'a', 'l', 'n'),
+    HB_TAG('i', 'n', 'i', 't'),
+    HB_TAG('i', 's', 'o', 'l'),
+    HB_TAG('j', 'a', 'l', 't'),
+    HB_TAG('k', 'e', 'r', 'n'),
+    HB_TAG('l', 'i', 'g', 'a'),
+    HB_TAG('l', 'j', 'm', 'o'),
+    HB_TAG('l', 'o', 'c', 'l'),
+    HB_TAG('l', 't', 'r', 'a'),
+    HB_TAG('l', 't', 'r', 'm'),
+    HB_TAG('m', 'a', 'r', 'k'),
+    HB_TAG('m', 'e', 'd', '2'),
+    HB_TAG('m', 'e', 'd', 'i'),
+    HB_TAG('m', 'k', 'm', 'k'),
+    HB_TAG('m', 's', 'e', 't'),
+    HB_TAG('n', 'u', 'k', 't'),
+    HB_TAG('n', 'u', 'm', 'r'),
+    HB_TAG('p', 'r', 'e', 'f'),
+    HB_TAG('p', 'r', 'e', 's'),
+    HB_TAG('p', 's', 't', 'f'),
+    HB_TAG('p', 's', 't', 's'),
+    HB_TAG('r', 'a', 'n', 'd'),
+    HB_TAG('r', 'c', 'l', 't'),
+    HB_TAG('r', 'k', 'r', 'f'),
+    HB_TAG('r', 'l', 'i', 'g'),
+    HB_TAG('r', 'p', 'h', 'f'),
+    HB_TAG('r', 't', 'l', 'a'),
+    HB_TAG('r', 't', 'l', 'm'),
+    HB_TAG('r', 'v', 'r', 'n'),
+    HB_TAG('s', 's', 't', 'y'),
+    HB_TAG('s', 't', 'c', 'h'),
+    HB_TAG('t', 'j', 'm', 'o'),
+    HB_TAG('v', 'a', 'l', 't'),
+    HB_TAG('v', 'a', 't', 'u'),
+    HB_TAG('v', 'c', 'h', 'w'),
+    HB_TAG('v', 'e', 'r', 't'),
+    HB_TAG('v', 'j', 'm', 'o'),
+    HB_TAG('v', 'k', 'r', 'n'),
+    HB_TAG('v', 'p', 'a', 'l'),
+    HB_TAG('v', 'r', 't', '2'),
+    HB_TAG('v', 'r', 't', 'r'),
+  });
+  return *kDefaultFeatures;
+}
+
+}  // namespace ift::feature_registry
+#endif  // IFT_FEATURE_REGISTRY_FEATURE_REGISTRY_H_
+