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-rw-r--r--python/pyyaml/lib/yaml/composer.py139
1 files changed, 139 insertions, 0 deletions
diff --git a/python/pyyaml/lib/yaml/composer.py b/python/pyyaml/lib/yaml/composer.py
new file mode 100644
index 000000000..06e5ac782
--- /dev/null
+++ b/python/pyyaml/lib/yaml/composer.py
@@ -0,0 +1,139 @@
+
+__all__ = ['Composer', 'ComposerError']
+
+from error import MarkedYAMLError
+from events import *
+from nodes import *
+
+class ComposerError(MarkedYAMLError):
+ pass
+
+class Composer(object):
+
+ def __init__(self):
+ self.anchors = {}
+
+ def check_node(self):
+ # Drop the STREAM-START event.
+ if self.check_event(StreamStartEvent):
+ self.get_event()
+
+ # If there are more documents available?
+ return not self.check_event(StreamEndEvent)
+
+ def get_node(self):
+ # Get the root node of the next document.
+ if not self.check_event(StreamEndEvent):
+ return self.compose_document()
+
+ def get_single_node(self):
+ # Drop the STREAM-START event.
+ self.get_event()
+
+ # Compose a document if the stream is not empty.
+ document = None
+ if not self.check_event(StreamEndEvent):
+ document = self.compose_document()
+
+ # Ensure that the stream contains no more documents.
+ if not self.check_event(StreamEndEvent):
+ event = self.get_event()
+ raise ComposerError("expected a single document in the stream",
+ document.start_mark, "but found another document",
+ event.start_mark)
+
+ # Drop the STREAM-END event.
+ self.get_event()
+
+ return document
+
+ def compose_document(self):
+ # Drop the DOCUMENT-START event.
+ self.get_event()
+
+ # Compose the root node.
+ node = self.compose_node(None, None)
+
+ # Drop the DOCUMENT-END event.
+ self.get_event()
+
+ self.anchors = {}
+ return node
+
+ def compose_node(self, parent, index):
+ if self.check_event(AliasEvent):
+ event = self.get_event()
+ anchor = event.anchor
+ if anchor not in self.anchors:
+ raise ComposerError(None, None, "found undefined alias %r"
+ % anchor.encode('utf-8'), event.start_mark)
+ return self.anchors[anchor]
+ event = self.peek_event()
+ anchor = event.anchor
+ if anchor is not None:
+ if anchor in self.anchors:
+ raise ComposerError("found duplicate anchor %r; first occurence"
+ % anchor.encode('utf-8'), self.anchors[anchor].start_mark,
+ "second occurence", event.start_mark)
+ self.descend_resolver(parent, index)
+ if self.check_event(ScalarEvent):
+ node = self.compose_scalar_node(anchor)
+ elif self.check_event(SequenceStartEvent):
+ node = self.compose_sequence_node(anchor)
+ elif self.check_event(MappingStartEvent):
+ node = self.compose_mapping_node(anchor)
+ self.ascend_resolver()
+ return node
+
+ def compose_scalar_node(self, anchor):
+ event = self.get_event()
+ tag = event.tag
+ if tag is None or tag == u'!':
+ tag = self.resolve(ScalarNode, event.value, event.implicit)
+ node = ScalarNode(tag, event.value,
+ event.start_mark, event.end_mark, style=event.style)
+ if anchor is not None:
+ self.anchors[anchor] = node
+ return node
+
+ def compose_sequence_node(self, anchor):
+ start_event = self.get_event()
+ tag = start_event.tag
+ if tag is None or tag == u'!':
+ tag = self.resolve(SequenceNode, None, start_event.implicit)
+ node = SequenceNode(tag, [],
+ start_event.start_mark, None,
+ flow_style=start_event.flow_style)
+ if anchor is not None:
+ self.anchors[anchor] = node
+ index = 0
+ while not self.check_event(SequenceEndEvent):
+ node.value.append(self.compose_node(node, index))
+ index += 1
+ end_event = self.get_event()
+ node.end_mark = end_event.end_mark
+ return node
+
+ def compose_mapping_node(self, anchor):
+ start_event = self.get_event()
+ tag = start_event.tag
+ if tag is None or tag == u'!':
+ tag = self.resolve(MappingNode, None, start_event.implicit)
+ node = MappingNode(tag, [],
+ start_event.start_mark, None,
+ flow_style=start_event.flow_style)
+ if anchor is not None:
+ self.anchors[anchor] = node
+ while not self.check_event(MappingEndEvent):
+ #key_event = self.peek_event()
+ item_key = self.compose_node(node, None)
+ #if item_key in node.value:
+ # raise ComposerError("while composing a mapping", start_event.start_mark,
+ # "found duplicate key", key_event.start_mark)
+ item_value = self.compose_node(node, item_key)
+ #node.value[item_key] = item_value
+ node.value.append((item_key, item_value))
+ end_event = self.get_event()
+ node.end_mark = end_event.end_mark
+ return node
+