authlib/oidc/core/util.py
import hashlib
from authlib.common.encoding import to_bytes, urlsafe_b64encode
def create_half_hash(s, alg):
hash_type = f'sha{alg[2:]}'
hash_alg = getattr(hashlib, hash_type, None)
if not hash_alg:
return None
data_digest = hash_alg(to_bytes(s)).digest()
slice_index = int(len(data_digest) / 2)
return urlsafe_b64encode(data_digest[:slice_index])