223 lines
6.5 KiB
Python
223 lines
6.5 KiB
Python
"""Interfaces for accessing metadata.
|
|
|
|
We provide two implementations.
|
|
* The "classic" file system implementation, which uses a directory
|
|
structure of files.
|
|
* A hokey sqlite backed implementation, which basically simulates
|
|
the file system in an effort to work around poor file system performance
|
|
on OS X.
|
|
"""
|
|
|
|
import binascii
|
|
import os
|
|
import time
|
|
|
|
from abc import abstractmethod
|
|
from typing import List, Iterable, Any, Optional
|
|
from typing_extensions import TYPE_CHECKING
|
|
if TYPE_CHECKING:
|
|
# We avoid importing sqlite3 unless we are using it so we can mostly work
|
|
# on semi-broken pythons that are missing it.
|
|
import sqlite3
|
|
|
|
|
|
class MetadataStore:
|
|
"""Generic interface for metadata storage."""
|
|
|
|
@abstractmethod
|
|
def getmtime(self, name: str) -> float:
|
|
"""Read the mtime of a metadata entry..
|
|
|
|
Raises FileNotFound if the entry does not exist.
|
|
"""
|
|
pass
|
|
|
|
@abstractmethod
|
|
def read(self, name: str) -> str:
|
|
"""Read the contents of a metadata entry.
|
|
|
|
Raises FileNotFound if the entry does not exist.
|
|
"""
|
|
pass
|
|
|
|
@abstractmethod
|
|
def write(self, name: str, data: str, mtime: Optional[float] = None) -> bool:
|
|
"""Write a metadata entry.
|
|
|
|
If mtime is specified, set it as the mtime of the entry. Otherwise,
|
|
the current time is used.
|
|
|
|
Returns True if the entry is successfully written, False otherwise.
|
|
"""
|
|
|
|
@abstractmethod
|
|
def remove(self, name: str) -> None:
|
|
"""Delete a metadata entry"""
|
|
pass
|
|
|
|
@abstractmethod
|
|
def commit(self) -> None:
|
|
"""If the backing store requires a commit, do it.
|
|
|
|
But N.B. that this is not *guaranteed* to do anything, and
|
|
there is no guarantee that changes are not made until it is
|
|
called.
|
|
"""
|
|
pass
|
|
|
|
@abstractmethod
|
|
def list_all(self) -> Iterable[str]: ...
|
|
|
|
|
|
def random_string() -> str:
|
|
return binascii.hexlify(os.urandom(8)).decode('ascii')
|
|
|
|
|
|
class FilesystemMetadataStore(MetadataStore):
|
|
def __init__(self, cache_dir_prefix: str) -> None:
|
|
# We check startswith instead of equality because the version
|
|
# will have already been appended by the time the cache dir is
|
|
# passed here.
|
|
if cache_dir_prefix.startswith(os.devnull):
|
|
self.cache_dir_prefix = None
|
|
else:
|
|
self.cache_dir_prefix = cache_dir_prefix
|
|
|
|
def getmtime(self, name: str) -> float:
|
|
if not self.cache_dir_prefix:
|
|
raise FileNotFoundError()
|
|
|
|
return int(os.path.getmtime(os.path.join(self.cache_dir_prefix, name)))
|
|
|
|
def read(self, name: str) -> str:
|
|
assert os.path.normpath(name) != os.path.abspath(name), "Don't use absolute paths!"
|
|
|
|
if not self.cache_dir_prefix:
|
|
raise FileNotFoundError()
|
|
|
|
with open(os.path.join(self.cache_dir_prefix, name)) as f:
|
|
return f.read()
|
|
|
|
def write(self, name: str, data: str, mtime: Optional[float] = None) -> bool:
|
|
assert os.path.normpath(name) != os.path.abspath(name), "Don't use absolute paths!"
|
|
|
|
if not self.cache_dir_prefix:
|
|
return False
|
|
|
|
path = os.path.join(self.cache_dir_prefix, name)
|
|
tmp_filename = path + '.' + random_string()
|
|
try:
|
|
os.makedirs(os.path.dirname(path), exist_ok=True)
|
|
with open(tmp_filename, 'w') as f:
|
|
f.write(data)
|
|
os.replace(tmp_filename, path)
|
|
if mtime is not None:
|
|
os.utime(path, times=(mtime, mtime))
|
|
|
|
except os.error:
|
|
return False
|
|
return True
|
|
|
|
def remove(self, name: str) -> None:
|
|
if not self.cache_dir_prefix:
|
|
raise FileNotFoundError()
|
|
|
|
os.remove(os.path.join(self.cache_dir_prefix, name))
|
|
|
|
def commit(self) -> None:
|
|
pass
|
|
|
|
def list_all(self) -> Iterable[str]:
|
|
if not self.cache_dir_prefix:
|
|
return
|
|
|
|
for dir, _, files in os.walk(self.cache_dir_prefix):
|
|
dir = os.path.relpath(dir, self.cache_dir_prefix)
|
|
for file in files:
|
|
yield os.path.join(dir, file)
|
|
|
|
|
|
SCHEMA = '''
|
|
CREATE TABLE IF NOT EXISTS files (
|
|
path TEXT UNIQUE NOT NULL,
|
|
mtime REAL,
|
|
data TEXT
|
|
);
|
|
CREATE INDEX IF NOT EXISTS path_idx on files(path);
|
|
'''
|
|
# No migrations yet
|
|
MIGRATIONS: List[str] = []
|
|
|
|
|
|
def connect_db(db_file: str) -> 'sqlite3.Connection':
|
|
import sqlite3.dbapi2
|
|
|
|
db = sqlite3.dbapi2.connect(db_file)
|
|
db.executescript(SCHEMA)
|
|
for migr in MIGRATIONS:
|
|
try:
|
|
db.executescript(migr)
|
|
except sqlite3.OperationalError:
|
|
pass
|
|
return db
|
|
|
|
|
|
class SqliteMetadataStore(MetadataStore):
|
|
def __init__(self, cache_dir_prefix: str) -> None:
|
|
# We check startswith instead of equality because the version
|
|
# will have already been appended by the time the cache dir is
|
|
# passed here.
|
|
if cache_dir_prefix.startswith(os.devnull):
|
|
self.db = None
|
|
return
|
|
|
|
os.makedirs(cache_dir_prefix, exist_ok=True)
|
|
self.db = connect_db(os.path.join(cache_dir_prefix, 'cache.db'))
|
|
|
|
def _query(self, name: str, field: str) -> Any:
|
|
# Raises FileNotFound for consistency with the file system version
|
|
if not self.db:
|
|
raise FileNotFoundError()
|
|
|
|
cur = self.db.execute(f'SELECT {field} FROM files WHERE path = ?', (name,))
|
|
results = cur.fetchall()
|
|
if not results:
|
|
raise FileNotFoundError()
|
|
assert len(results) == 1
|
|
return results[0][0]
|
|
|
|
def getmtime(self, name: str) -> float:
|
|
return self._query(name, 'mtime')
|
|
|
|
def read(self, name: str) -> str:
|
|
return self._query(name, 'data')
|
|
|
|
def write(self, name: str, data: str, mtime: Optional[float] = None) -> bool:
|
|
import sqlite3
|
|
|
|
if not self.db:
|
|
return False
|
|
try:
|
|
if mtime is None:
|
|
mtime = time.time()
|
|
self.db.execute('INSERT OR REPLACE INTO files(path, mtime, data) VALUES(?, ?, ?)',
|
|
(name, mtime, data))
|
|
except sqlite3.OperationalError:
|
|
return False
|
|
return True
|
|
|
|
def remove(self, name: str) -> None:
|
|
if not self.db:
|
|
raise FileNotFoundError()
|
|
|
|
self.db.execute('DELETE FROM files WHERE path = ?', (name,))
|
|
|
|
def commit(self) -> None:
|
|
if self.db:
|
|
self.db.commit()
|
|
|
|
def list_all(self) -> Iterable[str]:
|
|
if self.db:
|
|
for row in self.db.execute('SELECT path FROM files'):
|
|
yield row[0]
|