# Copyright 2022 The Johns Hopkins University
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import sqlite3
import subprocess
import sys
[docs]class Cache():
"""
This class handles all cache database operations. It is used largely in
support of recursive file uploads and downloads.
It operates by storing a SHA1 hash representing the time stamps for children
within a given directory and a status bit that indicates whether the
contents were successfully transferred at the time the hash was created.
"""
db_conn = None
db_cursor = None
def close(self):
"""
Close the database connection.
"""
self.db_conn.close()
def open(self, path):
"""
Open the database connection. Create the database and requisite tables
if they do not exist.
:param path: the path to the database file
:type path: string
"""
self.db_conn = sqlite3.connect(path)
self.db_cursor = self.db_conn.cursor()
# create table if it does not already exist
self.db_cursor.execute('''
SELECT count(name)
FROM sqlite_master
WHERE type='table'
AND name='dirs'
''')
if self.db_cursor.fetchone()[0] != 1:
self.db_cursor.execute('''
CREATE TABLE dirs (
complete bit,
hash varchar(40) NOT NULL,
path varchar(1024) NOT NULL UNIQUE
)
''')
# make file hidden for Windows
if sys.platform == 'win32':
subprocess.check_call(['attrib', '+H', path])
def check(self, dir_path, dir_hash):
"""
Check whether a directory's hash matches and has successfully completed.
In this case the check passes, returning `True`, so the directory may be
safely skipped. Should the directory not exist, the hash not match, or
the synchronization be incomplete, this returns `False` because it is
unsafe to skip this directory.
:param dir_path: the directory path
:type: string
:param dir_hash: the SHA1 hash for the timestamps of children of this
directory
:type dir_hash: string
:returns: True if the directory and hash match the stored value and the
transfer successfully completed; False otherwise
"""
self.db_cursor.execute('''
SELECT count(hash)
FROM dirs
WHERE hash=?
AND path=?
AND complete=1
''', (
dir_hash,
dir_path
))
if self.db_cursor.fetchone()[0] == 1:
return True
return False
def finish(self, dir_path, dir_hash):
"""
Finish a transfer. Mark a directory with matching hash as complete.
:param dir_path: the directory path
:type: string
:param dir_hash: the SHA1 hash for the timestamps of children of this
directory
:type dir_hash: string
"""
self.db_cursor.execute('''
UPDATE dirs
SET complete=1
WHERE hash=?
AND path=?
''', (
dir_hash,
dir_path
))
self.db_conn.commit()
def start(self, dir_path, dir_hash):
"""
Start a transfer. Create the directory and hash entry, and mark it as
incomplete.
:param dir_path: the directory path
:type: string
:param dir_hash: the SHA1 hash for the timestamps of children of this
directory
:type dir_hash: string
"""
try:
self.db_cursor.execute('''
INSERT INTO dirs VALUES (
?,
?,
?
)
''', (
0,
dir_hash,
dir_path,
))
self.db_conn.commit()
except sqlite3.IntegrityError:
self.db_cursor.execute('''
UPDATE dirs
SET complete=0, hash=?
WHERE path=?
''', (
dir_hash,
dir_path
))
self.db_conn.commit()