1 files changed, 239 insertions, 0 deletions
diff --git a/buildstream/plugins/elements/oci.py b/buildstream/plugins/elements/oci.py
new file mode 100644
index 000000000..5197b766c
--- /dev/null
+++ b/buildstream/plugins/elements/oci.py
@@ -0,0 +1,239 @@
+#
+#  Copyright 2018 Bloomberg Finance LP
+#
+#  This program is free software; you can redistribute it and/or
+#  modify it under the terms of the GNU Lesser General Public
+#  License as published by the Free Software Foundation; either
+#  version 2 of the License, or (at your option) any later version.
+#
+#  This library 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
+#  Lesser General Public License for more details.
+#
+#  You should have received a copy of the GNU Lesser General Public
+#  License along with this library. If not, see <http://www.gnu.org/licenses/>.
+#
+#  Authors:
+#        Chandan singh <csingh43@bloomberg.net>
+
+"""
+oci - Generate OCI Image
+========================
+Generate OCI image from its dependencies.
+
+This element is normally used near the end of a pipeline to prepare an OCI
+image that can be used for later deployment.
+
+.. note::
+
+   The ``oci`` element is available since :ref:`format version XX <project_format_version>`
+
+Here is the default configuration for the ``oci`` element in full:
+  .. literalinclude:: ../../../buildstream/plugins/elements/oci.yaml
+     :language: yaml
+"""
+
+import gzip
+import hashlib
+import json
+import os
+import shutil
+import tarfile
+
+from buildstream import Element, Scope, utils
+
+OCIIMAGE_SPEC_VERSION = '1.0.0'
+
+
+################
+# Helper classes
+################
+
+class Blob():
+
+    size = None
+    digest = None
+
+    def __init__(self, basedir):
+        self.basedir = basedir
+        # FIXME consider supporting other hashing algorithms
+        self._algorithm = hashlib.sha256
+        self._algorithm_name = 'sha256'
+
+    @property
+    def path(self):
+        blobs_dir = os.path.join(self.basedir, 'blobs', self._algorithm_name)
+        os.makedirs(blobs_dir, exist_ok=True)
+        return os.path.join(blobs_dir, self.digest)
+
+    @property
+    def digest_str(self):
+        return '{}:{}'.format(self._algorithm_name, self.digest)
+
+
+class RootfsBlob(Blob):
+
+    diff_id = None
+
+    def __init__(self, basedir, inputdir):
+        super().__init__(basedir)
+        self.inputdir = inputdir
+
+        # Create uncompressed tar archive and calculate diff id
+        with tarfile.TarFile(name='files.tar', mode='w') as tar:
+            for f in os.listdir(inputdir):
+                tar.add(os.path.join(inputdir, f), arcname=f)
+        with open('files.tar', 'rb') as f:
+            self.diff_id = self._algorithm(f.read()).hexdigest()
+
+        # Now compress the tar archive and calculate layer data
+        with open('files.tar', 'rb') as raw_archive:
+            with gzip.open('files.tar.gz', 'w') as compressed_archive:
+                compressed_archive.write(raw_archive.read())
+
+        with open('files.tar.gz', 'rb') as f:
+            self.digest = self._algorithm(f.read()).hexdigest()
+        self.size = os.path.getsize('files.tar.gz')
+
+        # Move the compressed tar archive into correct directory and clean up
+        shutil.move('files.tar.gz', self.path)
+        os.remove('files.tar')
+
+    @property
+    def diff_id_str(self):
+        return '{}:{}'.format(self._algorithm_name, self.diff_id)
+
+
+class StringBlob(Blob):
+
+    def __init__(self, basedir, contents):
+        super().__init__(basedir)
+        self.contents = contents = contents.encode()
+        self.size = len(contents)
+        self.digest = self._algorithm(contents).hexdigest()
+
+        # Write the blob
+        with utils.save_file_atomic(self.path, 'wb') as f:
+            f.write(contents)
+
+
+###################
+# OCI Image Element
+###################
+
+class OCIImageElement(Element):
+
+    # The oci element's output is its dependencies, so
+    # we must rebuild if the dependencies change even when
+    # not in strict build plans.
+    BST_STRICT_REBUILD = True
+
+    # OCI artifacts must never have indirect dependencies,
+    # so runtime dependencies are forbidden.
+    BST_FORBID_RDEPENDS = True
+
+    # This element ignores sources, so we should forbid them from being
+    # added, to reduce the potential for confusion
+    BST_FORBID_SOURCES = True
+
+    def configure(self, node):
+        # We don't need anything, yet...
+        self.node_validate(node, [])
+
+    def preflight(self):
+        # All good!
+        pass
+
+    def get_unique_key(self):
+        # All good! We don't need to rebuild if our dependencies haven't
+        # changed
+        return 1
+
+    def configure_sandbox(self, sandbox):
+        pass
+
+    def stage(self, sandbox):
+        pass
+
+    def assemble(self, sandbox):
+        basedir = sandbox.get_directory()
+        inputdir = os.path.join(basedir, 'input')
+        outputdir = os.path.join(basedir, 'output')
+        os.makedirs(inputdir, exist_ok=True)
+        os.makedirs(outputdir, exist_ok=True)
+
+        # Stage deps in the sandbox root
+        with self.timed_activity("Staging dependencies", silent_nested=True):
+            self.stage_dependency_artifacts(sandbox, Scope.BUILD, path='/input')
+
+        with self.timed_activity("Creating OCI image bundle", silent_nested=True):
+            # Generate oci-layout
+            with utils.save_file_atomic(os.path.join(outputdir, 'oci-layout'), 'w') as f:
+                f.write(json.dumps(self._oci_layout()))
+
+            # Generate blobs
+            # 1. rootfs
+            rootfs = RootfsBlob(outputdir, inputdir)
+            # 2. config
+            config_str = json.dumps(self._config(rootfs))
+            config = StringBlob(outputdir, config_str)
+            # 3. manifest
+            manifest_str = json.dumps(self._manifest(config, rootfs))
+            manifest = StringBlob(outputdir, manifest_str)
+
+            # Generate index.json
+            with utils.save_file_atomic(os.path.join(outputdir, 'index.json'), 'w') as f:
+                f.write(json.dumps(self._image_index(manifest)))
+
+        return '/output'
+
+    def _image_index(self, manifest):
+        index = {
+            'schemaVersion': 2,
+            'manifests': [{
+                'mediaType': 'application/vnd.oci.image.manifest.v1+json',
+                'size': manifest.size,
+                'digest': manifest.digest_str
+            }],
+        }
+        if self._annotations():
+            index['annotations'] = self._annotations()
+        return index
+
+    def _oci_layout(self):
+        return {
+            'imageLayoutVersion': OCIIMAGE_SPEC_VERSION,
+        }
+
+    def _manifest(self, config, rootfs):
+        return {
+            'schemaVersion': 2,
+            'config': {
+                'mediaType': 'application/vnd.oci.image.config.v1+json',
+                'digest': config.digest_str,
+                'size': config.size
+            },
+            'layers': [{
+                'mediaType': 'application/vnd.oci.image.layer.v1.tar+gzip',
+                'digest': rootfs.digest_str,
+                'size': rootfs.size
+            }]
+        }
+
+    def _annotations(self):
+        return []
+
+    def _config(self, rootfs):
+        return {
+            'architecture': 'amd64',
+            'os': 'linux',
+            'rootfs': {
+                'type': 'layers',
+                'diff_ids': [rootfs.diff_id_str]
+            }
+        }
+
+
+def setup():
+    return OCIImageElement