def prefix_lock(self, spec):
"""Get a lock on a particular spec's installation directory.
NOTE: The installation directory **does not** need to exist.
Prefix lock is a byte range lock on the nth byte of a file.
The lock file is ``spack.store.db.prefix_lock`` -- the DB
tells us what to call it and it lives alongside the install DB.
n is the sys.maxsize-bit prefix of the DAG hash. This makes
likelihood of collision is very low AND it gives us
readers-writer lock semantics with just a single lockfile, so no
cleanup required.
"""
prefix = spec.prefix
if prefix not in self._prefix_locks:
self._prefix_locks[prefix] = Lock(
self.prefix_lock_path,
spec.dag_hash_bit_prefix(bit_length(sys.maxsize)), 1)
return self._prefix_locks[prefix]
def prefix_lock(self, spec):
"""Get a lock on a particular spec's installation directory.
NOTE: The installation directory **does not** need to exist.
Prefix lock is a byte range lock on the nth byte of a file.
The lock file is ``spack.store.db.prefix_lock`` -- the DB
tells us what to call it and it lives alongside the install DB.
n is the sys.maxsize-bit prefix of the DAG hash. This makes
likelihood of collision is very low AND it gives us
readers-writer lock semantics with just a single lockfile, so no
cleanup required.
"""
prefix = spec.prefix
if prefix not in self._prefix_locks:
self._prefix_locks[prefix] = Lock(
self.prefix_lock_path,
spec.dag_hash_bit_prefix(bit_length(sys.maxsize)), 1)
return self._prefix_locks[prefix]
