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