69 lines
2.5 KiB
Python
69 lines
2.5 KiB
Python
import hashlib
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from pathlib import Path
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class KeyValueStore:
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KEY_FILE_SUFFIX = '.key'
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VALUE_FILE_SUFFIX = '.value'
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def __init__(
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self,
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cache_dir: str,
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):
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cache_dir = Path(cache_dir)
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hash_func = (
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lambda text: hashlib.sha256(text.encode('utf-8')).hexdigest())
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self.cache_dir = cache_dir
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self.hash_func = hash_func
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def store_value_text(self, key: str, text: str) -> str:
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return self.store_value_bytes(key, text.encode('utf-8'))
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def store_value_bytes(self, key: str, data: bytes) -> str:
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cache_id = self.hash_func(key)
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self.cache_dir.mkdir(parents=True, exist_ok=True)
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cache_key_file_path = self.cache_dir / (
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cache_id + KeyValueStore.KEY_FILE_SUFFIX)
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cache_value_file_path = self.cache_dir / (
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cache_id + KeyValueStore.VALUE_FILE_SUFFIX)
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if cache_key_file_path.exists():
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old_key = cache_key_file_path.read_text()
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if key != old_key:
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raise RuntimeError(
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'Cache is corrupted: File "{}" contains existing key '
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'"{}" != new key "{}"'.format(cache_key_file_path, old_key,
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key))
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if cache_value_file_path.exists():
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old_data = cache_value_file_path.read_bytes()
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if data != old_data:
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# TODO: Add options to raise error when overwriting the value.
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pass
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cache_value_file_path.write_bytes(data)
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cache_key_file_path.write_text(key)
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return cache_id
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def try_get_value_text(self, key: str) -> str:
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result = self.try_get_value_bytes(key)
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if result is None:
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return None
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return result.decode('utf-8')
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def try_get_value_bytes(self, key: str) -> bytes:
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cache_id = self.hash_func(key)
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cache_value_file_path = self.cache_dir / (
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cache_id + KeyValueStore.VALUE_FILE_SUFFIX)
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if cache_value_file_path.exists():
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return cache_value_file_path.read_bytes()
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return None
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def exists(self, key: str) -> bool:
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cache_id = self.hash_func(key)
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cache_key_file_path = self.cache_dir / (
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cache_id + KeyValueStore.KEY_FILE_SUFFIX)
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return cache_key_file_path.exists()
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def keys(self):
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for cache_key_file_path in self.cache_dir.glob(
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'*' + KeyValueStore.KEY_FILE_SUFFIX):
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yield Path(cache_key_file_path).read_text()
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