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# Modified from https://github.com/open-mmlab/mmcv/blob/master/mmcv/fileio/file_client.py # noqa: E501
from abc import ABCMeta, abstractmethod
class BaseStorageBackend(metaclass=ABCMeta):
"""Abstract class of storage backends.
All backends need to implement two apis: ``get()`` and ``get_text()``.
``get()`` reads the file as a byte stream and ``get_text()`` reads the file
as texts.
"""
@abstractmethod
def get(self, filepath):
pass
@abstractmethod
def get_text(self, filepath):
pass
class MemcachedBackend(BaseStorageBackend):
"""Memcached storage backend.
Attributes:
server_list_cfg (str): Config file for memcached server list.
client_cfg (str): Config file for memcached client.
sys_path (str | None): Additional path to be appended to `sys.path`.
Default: None.
"""
def __init__(self, server_list_cfg, client_cfg, sys_path=None):
if sys_path is not None:
import sys
sys.path.append(sys_path)
try:
import mc
except ImportError:
raise ImportError('Please install memcached to enable MemcachedBackend.')
self.server_list_cfg = server_list_cfg
self.client_cfg = client_cfg
self._client = mc.MemcachedClient.GetInstance(self.server_list_cfg, self.client_cfg)
# mc.pyvector servers as a point which points to a memory cache
self._mc_buffer = mc.pyvector()
def get(self, filepath):
filepath = str(filepath)
import mc
self._client.Get(filepath, self._mc_buffer)
value_buf = mc.ConvertBuffer(self._mc_buffer)
return value_buf
def get_text(self, filepath):
raise NotImplementedError
class HardDiskBackend(BaseStorageBackend):
"""Raw hard disks storage backend."""
def get(self, filepath):
filepath = str(filepath)
with open(filepath, 'rb') as f:
value_buf = f.read()
return value_buf
def get_text(self, filepath):
filepath = str(filepath)
with open(filepath, 'r') as f:
value_buf = f.read()
return value_buf
class LmdbBackend(BaseStorageBackend):
"""Lmdb storage backend.
Args:
db_paths (str | list[str]): Lmdb database paths.
client_keys (str | list[str]): Lmdb client keys. Default: 'default'.
readonly (bool, optional): Lmdb environment parameter. If True,
disallow any write operations. Default: True.
lock (bool, optional): Lmdb environment parameter. If False, when
concurrent access occurs, do not lock the database. Default: False.
readahead (bool, optional): Lmdb environment parameter. If False,
disable the OS filesystem readahead mechanism, which may improve
random read performance when a database is larger than RAM.
Default: False.
Attributes:
db_paths (list): Lmdb database path.
_client (list): A list of several lmdb envs.
"""
def __init__(self, db_paths, client_keys='default', readonly=True, lock=False, readahead=False, **kwargs):
try:
import lmdb
except ImportError:
raise ImportError('Please install lmdb to enable LmdbBackend.')
if isinstance(client_keys, str):
client_keys = [client_keys]
if isinstance(db_paths, list):
self.db_paths = [str(v) for v in db_paths]
elif isinstance(db_paths, str):
self.db_paths = [str(db_paths)]
assert len(client_keys) == len(self.db_paths), ('client_keys and db_paths should have the same length, '
f'but received {len(client_keys)} and {len(self.db_paths)}.')
self._client = {}
for client, path in zip(client_keys, self.db_paths):
self._client[client] = lmdb.open(path, readonly=readonly, lock=lock, readahead=readahead, **kwargs)
def get(self, filepath, client_key):
"""Get values according to the filepath from one lmdb named client_key.
Args:
filepath (str | obj:`Path`): Here, filepath is the lmdb key.
client_key (str): Used for distinguishing differnet lmdb envs.
"""
filepath = str(filepath)
assert client_key in self._client, (f'client_key {client_key} is not ' 'in lmdb clients.')
client = self._client[client_key]
with client.begin(write=False) as txn:
value_buf = txn.get(filepath.encode('ascii'))
return value_buf
def get_text(self, filepath):
raise NotImplementedError
class FileClient(object):
"""A general file client to access files in different backend.
The client loads a file or text in a specified backend from its path
and return it as a binary file. it can also register other backend
accessor with a given name and backend class.
Attributes:
backend (str): The storage backend type. Options are "disk",
"memcached" and "lmdb".
client (:obj:`BaseStorageBackend`): The backend object.
"""
_backends = {
'disk': HardDiskBackend,
'memcached': MemcachedBackend,
'lmdb': LmdbBackend,
}
def __init__(self, backend='disk', **kwargs):
if backend not in self._backends:
raise ValueError(f'Backend {backend} is not supported. Currently supported ones'
f' are {list(self._backends.keys())}')
self.backend = backend
self.client = self._backends[backend](**kwargs)
def get(self, filepath, client_key='default'):
# client_key is used only for lmdb, where different fileclients have
# different lmdb environments.
if self.backend == 'lmdb':
return self.client.get(filepath, client_key)
else:
return self.client.get(filepath)
def get_text(self, filepath):
return self.client.get_text(filepath)
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