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query.py
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# Copyright (C) 2015-2017 The Software Heritage developers
# See the AUTHORS file at the top-level directory of this distribution
# License: GNU Affero General Public License version 3, or any later version
# See top-level LICENSE file for more information
import re
from uuid import UUID
from swh.model.hashutil import ALGORITHMS, hash_to_bytes
from swh.web.api.exc import BadInputExc
SHA256_RE = re.compile(r'^[0-9a-f]{64}$', re.IGNORECASE)
SHA1_RE = re.compile(r'^[0-9a-f]{40}$', re.IGNORECASE)
def parse_hash(q):
"""Detect the hash type of a user submitted query string.
Args:
query string with the following format: "[HASH_TYPE:]HEX_CHECKSUM",
where HASH_TYPE is optional, defaults to "sha1", and can be one of
swh.model.hashutil.ALGORITHMS
Returns:
A pair (hash_algorithm, byte hash value)
Raises:
ValueError if the given query string does not correspond to a valid
hash value
"""
def guess_algo(q):
if SHA1_RE.match(q):
return 'sha1'
elif SHA256_RE.match(q):
return 'sha256'
else:
raise BadInputExc('Invalid checksum query string %s' % q)
def check_algo(algo, hex):
if (algo in {'sha1', 'sha1_git'} and not SHA1_RE.match(hex)) \
or (algo == 'sha256' and not SHA256_RE.match(hex)):
raise BadInputExc('Invalid hash %s for algorithm %s' % (hex, algo))
parts = q.split(':')
if len(parts) > 2:
raise BadInputExc('Invalid checksum query string %s' % q)
elif len(parts) == 1:
parts = (guess_algo(q), q)
elif len(parts) == 2:
check_algo(parts[0], parts[1])
algo = parts[0]
if algo not in ALGORITHMS:
raise BadInputExc('Unknown hash algorithm %s' % algo)
return (algo, hash_to_bytes(parts[1]))
def parse_hash_with_algorithms_or_throws(q, accepted_algo, error_msg):
"""Parse a query but only accepts accepted_algo.
Otherwise, raise the exception with message error_msg.
Args:
- q: query string with the following format: "[HASH_TYPE:]HEX_CHECKSUM"
where HASH_TYPE is optional, defaults to "sha1", and can be one of
swh.model.hashutil.ALGORITHMS.
- accepted_algo: array of strings representing the names of accepted
algorithms.
- error_msg: error message to raise as BadInputExc if the algo of
the query does not match.
Returns:
A pair (hash_algorithm, byte hash value)
Raises:
BadInputExc when the inputs is invalid or does not
validate the accepted algorithms.
"""
algo, hash = parse_hash(q)
if algo not in accepted_algo:
raise BadInputExc(error_msg)
return (algo, hash)
def parse_uuid4(uuid):
"""Parse an uuid 4 from a string.
Args:
uuid: String representing an uuid.
Returns:
The uuid as is if everything is ok.
Raises:
BadInputExc: if the uuid is invalid.
"""
try:
UUID(uuid, version=4)
except ValueError as e:
# not a valid hex code for a UUID
raise BadInputExc(str(e))
return uuid

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