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# Copyright (C) 2012 Codethink Limited
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; version 2 of the License.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
import cliapp
import collections
class MutualDependencyError(cliapp.AppException):
def __init__(self, a, b):
cliapp.AppException.__init__(
self, 'Cyclic dependency between %s and %s detected' % (a, b))
class CyclicDependencyChainError(cliapp.AppException):
def __init__(self):
cliapp.AppException.__init__(
self, 'Cyclic dependency detected somewhere')
class DependencyOrderError(cliapp.AppException):
def __init__(self, stratum, chunk, dependency_name):
cliapp.AppException.__init__(
self, 'In stratum %s, chunk %s references its dependency %s '
'before it is defined' % (stratum, chunk, dependency_name))
class DependencyFormatError(cliapp.AppException):
def __init__(self, stratum, chunk):
cliapp.AppException.__init__(
self, 'In stratum %s, chunk %s uses an invalid '
'build-depends format' % (stratum, chunk))
class BuildGraph(object):
def compute_build_order(self, source_pool):
self._realise_dependencies(source_pool)
sorting = self._compute_topological_sorting(source_pool)
groups = self._create_build_groups(sorting)
return groups
def _realise_dependencies(self, source_pool):
queue = collections.deque(source_pool)
while queue:
source = queue.popleft()
if source.morphology['kind'] == 'system':
self._realise_system_dependencies(source, queue, source_pool)
elif source.morphology['kind'] == 'stratum':
self._realise_stratum_dependencies(source, queue, source_pool)
def _realise_system_dependencies(self, system, queue, source_pool):
for stratum_name in system.morphology['strata']:
stratum = source_pool.lookup(
system.repo_name,
system.original_ref,
'%s.morph' % stratum_name)
system.add_dependency(stratum)
queue.append(stratum)
def _realise_stratum_dependencies(self, stratum, queue, source_pool):
strata = []
if stratum.morphology['build-depends']:
for stratum_name in stratum.morphology['build-depends']:
other_stratum = source_pool.lookup(
stratum.repo_name,
stratum.original_ref,
'%s.morph' % stratum_name)
strata.append(other_stratum)
if other_stratum.depends_on(stratum):
raise MutualDependencyError(stratum, other_stratum)
stratum.add_dependency(other_stratum)
queue.append(other_stratum)
chunks = []
processed_chunks = []
name_to_processed_chunk = {}
for info in stratum.morphology['sources']:
chunk = source_pool.lookup(
info['repo'],
info['ref'],
'%s.morph' % info['morph'])
chunks.append(chunk)
stratum.add_dependency(chunk)
for other_stratum in strata:
chunk.add_dependency(other_stratum)
build_depends = info.get('build-depends', None)
if build_depends is None:
for earlier_chunk in processed_chunks:
if earlier_chunk.depends_on(chunk):
raise MutualDependencyError(chunk, earlier_chunk)
chunk.add_dependency(earlier_chunk)
elif isinstance(build_depends, list):
for name in build_depends:
other_chunk = name_to_processed_chunk.get(name, None)
if other_chunk:
chunk.add_dependency(other_chunk)
else:
raise DependencyOrderError(stratum, info['name'], name)
else:
raise DependencyFormatError(stratum, info['name'])
processed_chunks.append(chunk)
name_to_processed_chunk[info['name']] = chunk
def _compute_topological_sorting(self, source_pool):
'''Computes a topological sorting of the build graph.
A topological sorting basically is the result of a series of
breadth-first searches starting at each leaf node (sources with no
dependencies). Sources are added to the sorting as soon as all their
dependencies have been added (which means that by then, all
dependencies are satisfied).
For more information, see
http://en.wikipedia.org/wiki/Topological_sorting.
'''
# map sources to sets of satisfied dependencies. this is to detect when
# we can actually add sources to the BFS queue. rather than dropping
# links between nodes, like most topological sorting algorithms do,
# we simply remember all satisfied dependencies and check if all
# of them are met repeatedly
satisfied_dependencies = {}
# create an empty sorting
sorting = collections.deque()
# create a set of leafs to start the DFS from
leafs = collections.deque()
for source in source_pool:
satisfied_dependencies[source] = set()
if len(source.dependencies) == 0:
leafs.append(source)
while len(leafs) > 0:
# fetch a leaf source from the DFS queue
source = leafs.popleft()
# add it to the sorting
sorting.append(source)
# mark this dependency as resolved
for dependent in source.dependents:
satisfied_dependencies[dependent].add(source)
# add the dependent blob as a leaf if all
# its dependencies have been resolved
has = len(satisfied_dependencies[dependent])
needs = len(dependent.dependencies)
if has == needs:
leafs.append(dependent)
# if not all dependencies were resolved on the way, we
# have found at least one cyclic dependency
if len(sorting) < len(source_pool):
raise CyclicDependencyChainError()
return sorting
def _create_build_groups(self, sorting):
groups = collections.deque()
if sorting:
# create the first group
group = []
groups.append(group)
# traverse the build graph in topological order
for source in sorting:
# add the current item to the current group, or a new group
# if one of its dependencies is in the current one
create_group = False
for dependency in source.dependencies:
if dependency in group:
create_group = True
if create_group:
group = []
groups.append(group)
group.append(source)
return groups
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