Virtual directory API: Add get_size with implementations

buildstream/storage/_casbaseddirectory.py

@@ -836,6 +836,18 @@ class CasBasedDirectory(Directory):
         self._recalculate_recursing_up()
         self._recalculate_recursing_down()
 
+    def get_size(self):
+        total = len(self.pb2_directory.SerializeToString())
+        for i in self.index.values():
+            if isinstance(i.buildstream_object, CasBasedDirectory):
+                total += i.buildstream_object.get_size()
+            elif isinstance(i.pb_object, remote_execution_pb2.FileNode):
+                src_name = self.cas_cache.objpath(i.pb_object.digest)
+                filesize = os.stat(src_name).st_size
+                total += filesize
+            # Symlink nodes are encoded as part of the directory serialization.
+        return total
+
     def _get_identifier(self):
         path = ""
         if self.parent:

buildstream/storage/_filebaseddirectory.py

@@ -30,6 +30,7 @@ See also: :ref:`sandboxing`.
 import os
 import time
 from .directory import Directory, VirtualDirectoryError
+from .. import utils
 from ..utils import link_files, copy_files, list_relative_paths, _get_link_mtime, _magic_timestamp
 from ..utils import _set_deterministic_user, _set_deterministic_mtime
 
@@ -201,6 +202,9 @@ class FileBasedDirectory(Directory):
 
         return list_relative_paths(self.external_directory)
 
+    def get_size(self):
+        return utils._get_dir_size(self.external_directory)
+
     def __str__(self):
         # This returns the whole path (since we don't know where the directory started)
         # which exposes the sandbox directory; we will have to assume for the time being

buildstream/storage/directory.py

@@ -176,3 +176,9 @@ class Directory():
 
         """
         raise NotImplementedError()
+
+    def get_size(self):
+        """ Get an approximation of the storage space in bytes used by this directory
+        and all files and subdirectories in it. Storage space varies by implementation
+        and effective space used may be lower than this number due to deduplication. """
+        raise NotImplementedError()