Trying to infer datablock sizes from pointers

sizes of datablocks.py

import bpy
from itertools import chain
import math

def convert_size(size_bytes):
   if size_bytes == 0:
       return "0B"
   size_name = ("B", "KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB")
   i = int(math.floor(math.log(size_bytes, 1024)))
   p = math.pow(1024, i)
   s = round(size_bytes / p, 2)
   return "%s %s" % (s, size_name[i])

def popup(title = "Info", icon = 'INFO', lines=""):
    myLines=lines
    def draw(self, context):
        for n in myLines:
            self.layout.label(text=n)
    bpy.context.window_manager.popup_menu(draw, title = title, icon = icon)



dbs = []
class DB:
    def __init__(self, db):
        self.type = type(db).bl_rna.identifier
        self.name = db.name
        self.ptr = db.as_pointer()
        dbs.append(self)

for db in chain(bpy.data.actions, bpy.data.armatures, bpy.data.brushes, bpy.data.cache_files, bpy.data.cameras, bpy.data.collections, bpy.data.curves, bpy.data.fonts, bpy.data.grease_pencils, bpy.data.hair_curves, bpy.data.images, bpy.data.lattices, bpy.data.libraries, bpy.data.lightprobes, bpy.data.lights, bpy.data.linestyles, bpy.data.masks, bpy.data.materials, bpy.data.meshes, bpy.data.metaballs, bpy.data.movieclips, bpy.data.node_groups, bpy.data.objects, bpy.data.paint_curves, bpy.data.palettes, bpy.data.particles, bpy.data.pointclouds, bpy.data.scenes, bpy.data.screens, bpy.data.shape_keys, bpy.data.sounds, bpy.data.speakers, bpy.data.texts, bpy.data.textures, bpy.data.volumes, bpy.data.window_managers, bpy.data.workspaces, bpy.data.worlds):
    DB(db)

dbs.sort(key=lambda x: x.ptr)

for i, db in enumerate(dbs):
    if i > 0:
        prev = dbs[i-1]
        prev.size = db.ptr - prev.ptr
dbs[-1].size = 0

dbs.sort(key=lambda x: x.size, reverse=True)

dblist = []
for db in dbs:
    dblist.append("{} ({}) = {}".format(db.name, db.type, convert_size(db.size)))

info = '\r\n'.join(dblist)

popup(title="Datablocks by size in memory", icon='INFO', lines=dblist)