Implement Write Barriers

This makes the gem a bit more GC friendly. Objects with `RUBY_TYPED_WB_PROTECTED`
can be promoted to the old generation (hence not be scanned on minor GC cycles),
however they MUST trigger write barriers using the `RB_OBJ_WRITE` macro when updating
a reference.

Author: byroot

ext/zstdruby/streaming_compress.c

@@ -57,7 +57,7 @@ static const rb_data_type_t streaming_compress_type = {
     streaming_compress_compact,
 #endif
   },
-  0, 0, RUBY_TYPED_FREE_IMMEDIATELY
+  0, 0, RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED
 };
 
 static VALUE
@@ -66,9 +66,9 @@ rb_streaming_compress_allocate(VALUE klass)
   struct streaming_compress_t* sc;
   VALUE obj = TypedData_Make_Struct(klass, struct streaming_compress_t, &streaming_compress_type, sc);
   sc->ctx = NULL;
-  sc->buf = Qnil;
+  RB_OBJ_WRITE(obj, &sc->buf, Qnil);
   sc->buf_size = 0;
-  sc->pending = Qnil;
+  RB_OBJ_WRITE(obj, &sc->pending, Qnil);
   return obj;
 }
 
@@ -89,9 +89,9 @@ rb_streaming_compress_initialize(int argc, VALUE *argv, VALUE obj)
   set_compress_params(ctx, kwargs);
 
   sc->ctx = ctx;
-  sc->buf = rb_str_new(NULL, buffOutSize);
+  RB_OBJ_WRITE(obj, &sc->buf, rb_str_new(NULL, buffOutSize));
   sc->buf_size = buffOutSize;
-  sc->pending = rb_str_new(0, 0);
+  RB_OBJ_WRITE(obj, &sc->pending, rb_str_new(0, 0));
 
   return obj;
 }

ext/zstdruby/streaming_decompress.c

@@ -53,7 +53,7 @@ static const rb_data_type_t streaming_decompress_type = {
     streaming_decompress_compact,
 #endif
   },
-  0, 0, RUBY_TYPED_FREE_IMMEDIATELY
+  0, 0, RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED
 };
 
 static VALUE
@@ -62,7 +62,7 @@ rb_streaming_decompress_allocate(VALUE klass)
   struct streaming_decompress_t* sd;
   VALUE obj = TypedData_Make_Struct(klass, struct streaming_decompress_t, &streaming_decompress_type, sd);
   sd->dctx = NULL;
-  sd->buf = Qnil;
+  RB_OBJ_WRITE(obj, &sd->buf, Qnil);
   sd->buf_size = 0;
   return obj;
 }
@@ -84,7 +84,7 @@ rb_streaming_decompress_initialize(int argc, VALUE *argv, VALUE obj)
   set_decompress_params(dctx, kwargs);
 
   sd->dctx = dctx;
-  sd->buf = rb_str_new(NULL, buffOutSize);
+  RB_OBJ_WRITE(obj, &sd->buf, rb_str_new(NULL, buffOutSize));
   sd->buf_size = buffOutSize;
 
   return obj;

ext/zstdruby/zstdruby.c

@@ -145,13 +145,13 @@ static size_t sizeof_ddict(const void *dict)
 static const rb_data_type_t cdict_type = {
   "Zstd::CDict",
   {0, free_cdict, sizeof_cdict,},
-  0, 0, RUBY_TYPED_FREE_IMMEDIATELY
+  0, 0, RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED
 };
 
 static const rb_data_type_t ddict_type = {
   "Zstd::DDict",
   {0, free_ddict, sizeof_ddict,},
-  0, 0, RUBY_TYPED_FREE_IMMEDIATELY
+  0, 0, RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED
 };
 
 static VALUE rb_cdict_alloc(VALUE self)