Embed File::Stat objects

They are very short lived and fit in a 160B slot.

file.c

@@ -483,28 +483,29 @@ apply2files(int (*func)(const char *, void *), int argc, VALUE *argv, void *arg)
     return LONG2FIX(argc);
 }
 
-static size_t
-stat_memsize(const void *p)
-{
-    return sizeof(struct stat);
-}
-
 static const rb_data_type_t stat_data_type = {
     "stat",
-    {NULL, RUBY_TYPED_DEFAULT_FREE, stat_memsize,},
-    0, 0, RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED
+    {
+        NULL,
+        RUBY_TYPED_DEFAULT_FREE,
+        NULL, // No external memory to report
+    },
+    0, 0, RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED | RUBY_TYPED_EMBEDDABLE
+};
+
+struct rb_stat {
+    struct stat stat;
+    bool initialized;
 };
 
 static VALUE
 stat_new_0(VALUE klass, const struct stat *st)
 {
-    struct stat *nst = 0;
-    VALUE obj = TypedData_Wrap_Struct(klass, &stat_data_type, 0);
-
+    struct rb_stat *rb_st;
+    VALUE obj = TypedData_Make_Struct(klass, struct rb_stat, &stat_data_type, rb_st);
     if (st) {
-        nst = ALLOC(struct stat);
-        *nst = *st;
-        RTYPEDDATA_DATA(obj) = nst;
+        rb_st->stat = *st;
+        rb_st->initialized = true;
     }
     return obj;
 }
@@ -518,10 +519,10 @@ rb_stat_new(const struct stat *st)
 static struct stat*
 get_stat(VALUE self)
 {
-    struct stat* st;
-    TypedData_Get_Struct(self, struct stat, &stat_data_type, st);
-    if (!st) rb_raise(rb_eTypeError, "uninitialized File::Stat");
-    return st;
+    struct rb_stat* rb_st;
+    TypedData_Get_Struct(self, struct rb_stat, &stat_data_type, rb_st);
+    if (!rb_st->initialized) rb_raise(rb_eTypeError, "uninitialized File::Stat");
+    return &rb_st->stat;
 }
 
 static struct timespec stat_mtimespec(const struct stat *st);
@@ -1092,9 +1093,9 @@ rb_stat_inspect(VALUE self)
 #endif
     };
 
-    struct stat* st;
-    TypedData_Get_Struct(self, struct stat, &stat_data_type, st);
-    if (!st) {
+    struct rb_stat* rb_st;
+    TypedData_Get_Struct(self, struct rb_stat, &stat_data_type, rb_st);
+    if (!rb_st->initialized) {
         return rb_sprintf("#<%s: uninitialized>", rb_obj_classname(self));
     }
 
@@ -5557,7 +5558,7 @@ rb_stat_s_alloc(VALUE klass)
 static VALUE
 rb_stat_init(VALUE obj, VALUE fname)
 {
-    struct stat st, *nst;
+    struct stat st;
 
     FilePathValue(fname);
     fname = rb_str_encode_ospath(fname);
@@ -5565,13 +5566,11 @@ rb_stat_init(VALUE obj, VALUE fname)
         rb_sys_fail_path(fname);
     }
 
-    if (DATA_PTR(obj)) {
-        xfree(DATA_PTR(obj));
-        DATA_PTR(obj) = NULL;
-    }
-    nst = ALLOC(struct stat);
-    *nst = st;
-    DATA_PTR(obj) = nst;
+    struct rb_stat *rb_st;
+    TypedData_Get_Struct(obj, struct rb_stat, &stat_data_type, rb_st);
+
+    rb_st->stat = st;
+    rb_st->initialized = true;
 
     return Qnil;
 }
@@ -5580,19 +5579,15 @@ rb_stat_init(VALUE obj, VALUE fname)
 static VALUE
 rb_stat_init_copy(VALUE copy, VALUE orig)
 {
-    struct stat *nst;
-
     if (!OBJ_INIT_COPY(copy, orig)) return copy;
-    if (DATA_PTR(copy)) {
-        xfree(DATA_PTR(copy));
-        DATA_PTR(copy) = 0;
-    }
-    if (DATA_PTR(orig)) {
-        nst = ALLOC(struct stat);
-        *nst = *(struct stat*)DATA_PTR(orig);
-        DATA_PTR(copy) = nst;
-    }
 
+    struct rb_stat *orig_rb_st;
+    TypedData_Get_Struct(orig, struct rb_stat, &stat_data_type, orig_rb_st);
+
+    struct rb_stat *copy_rb_st;
+    TypedData_Get_Struct(copy, struct rb_stat, &stat_data_type, copy_rb_st);
+
+    *copy_rb_st = *orig_rb_st;
     return copy;
 }