diff --git a/ext/ddcov/ddcov.c b/ext/ddcov/ddcov.c
index 9fe245a9..417949de 100644
--- a/ext/ddcov/ddcov.c
+++ b/ext/ddcov/ddcov.c
@@ -2,19 +2,80 @@
 #include <ruby/debug.h>
 #include <stdio.h>
 
-VALUE DDCovClass = Qnil;
+// Utils
+static bool prefix(const char *pre, const char *str)
+{
+  return strncmp(pre, str, strlen(pre)) == 0;
+}
 
-VALUE dd_cov_initialize(VALUE self)
+// Data structure
+struct dd_cov_data
 {
-  rb_iv_set(self, "@var", rb_hash_new());
-  return self;
+  char *root;
+  VALUE coverage;
+};
+
+static void dd_cov_mark(void *ptr)
+{
+  // printf("MARK\n");
+  struct dd_cov_data *dd_cov_data = ptr;
+  rb_gc_mark_movable(dd_cov_data->coverage);
+}
+
+static void dd_cov_free(void *ptr)
+{
+  // printf("FREE\n");
+  struct dd_cov_data *dd_cov_data = ptr;
+
+  xfree(dd_cov_data);
+}
+
+static void dd_cov_compact(void *ptr)
+{
+  // printf("COMPACT\n");
+  struct dd_cov_data *dd_cov_data = ptr;
+  dd_cov_data->coverage = rb_gc_location(dd_cov_data->coverage);
+}
+
+const rb_data_type_t dd_cov_data_type = {
+    .wrap_struct_name = "dd_cov",
+    .function = {
+        .dmark = dd_cov_mark,
+        .dfree = dd_cov_free,
+        .dsize = NULL,
+        .dcompact = dd_cov_compact},
+    .flags = RUBY_TYPED_FREE_IMMEDIATELY};
+
+static VALUE dd_cov_allocate(VALUE klass)
+{
+  // printf("ALLOCATE\n");
+  struct dd_cov_data *dd_cov_data;
+  VALUE obj = TypedData_Make_Struct(klass, struct dd_cov_data, &dd_cov_data_type, dd_cov_data);
+  dd_cov_data->coverage = rb_hash_new();
+  return obj;
+}
+
+// DDCov methods
+static VALUE dd_cov_initialize(VALUE self, VALUE rb_root)
+{
+  // printf("INITIALIZE\n");
+  struct dd_cov_data *dd_cov_data;
+  TypedData_Get_Struct(self, struct dd_cov_data, &dd_cov_data_type, dd_cov_data);
+
+  // printf("struct got\n");
+  dd_cov_data->root = StringValueCStr(rb_root);
+  // printf("root set\n");
+
+  return Qnil;
 }
 
-void dd_cov_update_line_coverage(rb_event_flag_t event, VALUE data, VALUE self, ID id, VALUE klass)
+static void dd_cov_update_line_coverage(rb_event_flag_t event, VALUE data, VALUE self, ID id, VALUE klass)
 {
   // printf("EVENT HOOK FIRED\n");
   // printf("FILE: %s\n", rb_sourcefile());
   // printf("LINE: %d\n", rb_sourceline());
+  struct dd_cov_data *dd_cov_data;
+  TypedData_Get_Struct(data, struct dd_cov_data, &dd_cov_data_type, dd_cov_data);
 
   const char *filename = rb_sourcefile();
   if (filename == 0)
@@ -22,13 +83,18 @@ void dd_cov_update_line_coverage(rb_event_flag_t event, VALUE data, VALUE self,
     return;
   }
 
-  unsigned long filename_length = strlen(filename);
+  if (!prefix(dd_cov_data->root, filename))
+  {
+    return;
+  }
+
+  unsigned long len_filename = strlen(filename);
 
-  VALUE rb_str_source_file = rb_str_new(filename, filename_length);
-  rb_hash_aset(rb_iv_get(data, "@var"), rb_str_source_file, Qtrue);
+  VALUE rb_str_source_file = rb_str_new(filename, len_filename);
+  rb_hash_aset(dd_cov_data->coverage, rb_str_source_file, Qtrue);
 }
 
-VALUE dd_cov_start(VALUE self)
+static VALUE dd_cov_start(VALUE self)
 {
   // get current thread
   VALUE thval = rb_thread_current();
@@ -39,23 +105,30 @@ VALUE dd_cov_start(VALUE self)
   return self;
 }
 
-VALUE dd_cov_stop(VALUE self)
+static VALUE dd_cov_stop(VALUE self)
 {
   // get current thread
   VALUE thval = rb_thread_current();
-
   // remove event hook
   rb_thread_remove_event_hook(thval, dd_cov_update_line_coverage);
 
-  return rb_iv_get(self, "@var");
+  struct dd_cov_data *dd_cov_data;
+  TypedData_Get_Struct(self, struct dd_cov_data, &dd_cov_data_type, dd_cov_data);
+
+  VALUE cov = dd_cov_data->coverage;
+
+  dd_cov_data->coverage = rb_hash_new();
+
+  return cov;
 }
 
 void Init_ddcov(void)
 {
-  id_puts = rb_intern("puts");
+  VALUE cDDCov = rb_define_class("DDCov", rb_cObject);
+
+  rb_define_alloc_func(cDDCov, dd_cov_allocate);
 
-  DDCovClass = rb_define_class("DDCov", rb_cObject);
-  rb_define_method(DDCovClass, "initialize", dd_cov_initialize, 0);
-  rb_define_method(DDCovClass, "start", dd_cov_start, 0);
-  rb_define_method(DDCovClass, "stop", dd_cov_stop, 0);
+  rb_define_method(cDDCov, "initialize", dd_cov_initialize, 1);
+  rb_define_method(cDDCov, "start", dd_cov_start, 0);
+  rb_define_method(cDDCov, "stop", dd_cov_stop, 0);
 }
diff --git a/lib/datadog/ci/itr/coverage/collector.rb b/lib/datadog/ci/itr/coverage/collector.rb
index f4093edb..b58b2125 100644
--- a/lib/datadog/ci/itr/coverage/collector.rb
+++ b/lib/datadog/ci/itr/coverage/collector.rb
@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-require "coverage"
-
-require_relative "filter"
+require_relative "../../utils/git"
 require_relative "../../../../ddcov/ddcov"
 
 module Datadog
@@ -11,7 +9,7 @@ module Itr
       module Coverage
         class Collector
           def initialize
-            @ddcov = DDCov.new
+            # TODO: make this thread local
           end
 
           def setup
@@ -19,14 +17,14 @@ def setup
           end
 
           def start
+            @ddcov = DDCov.new(Utils::Git.root)
             @ddcov.start
           end
 
           def stop
-            result = @ddcov.stop
-            @ddcov.instance_variable_set(:@var, {})
-
-            Filter.call(result)
+            @ddcov.stop
+            # p "RAW"
+            # p result.count
           end
         end
       end