import hashlib import json import os.path import filelock cache_filename = "cache.json" cache_data = None def dump_cache(): with filelock.FileLock(cache_filename+".lock"): with open(cache_filename, "w", encoding="utf8") as file: json.dump(cache_data, file, indent=4) def cache(subsection): global cache_data if cache_data is None: with filelock.FileLock(cache_filename+".lock"): if not os.path.isfile(cache_filename): cache_data = {} else: with open(cache_filename, "r", encoding="utf8") as file: cache_data = json.load(file) s = cache_data.get(subsection, {}) cache_data[subsection] = s return s def calculate_sha256(filename): hash_sha256 = hashlib.sha256() blksize = 1024 * 1024 with open(filename, "rb") as f: for chunk in iter(lambda: f.read(blksize), b""): hash_sha256.update(chunk) return hash_sha256.hexdigest() def sha256_from_cache(filename, title): hashes = cache("hashes") ondisk_mtime = os.path.getmtime(filename) if title not in hashes: return None cached_sha256 = hashes[title].get("sha256", None) cached_mtime = hashes[title].get("mtime", 0) if ondisk_mtime > cached_mtime or cached_sha256 is None: return None return cached_sha256 def sha256(filename, title): hashes = cache("hashes") sha256_value = sha256_from_cache(filename, title) if sha256_value is not None: return sha256_value print(f"Calculating sha256 for {filename}: ", end='') sha256_value = calculate_sha256(filename) print(f"{sha256_value}") hashes[title] = { "mtime": os.path.getmtime(filename), "sha256": sha256_value, } dump_cache() return sha256_value