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|
# Events should obey the following grammar:
# stream ::= STREAM-START document* STREAM-END
# document ::= DOCUMENT-START node DOCUMENT-END
# node ::= SCALAR | sequence | mapping
# sequence ::= SEQUENCE-START node* SEQUENCE-END
# mapping ::= MAPPING-START (node node)* MAPPING-END
__all__ = ['Emitter', 'EmitterError']
from error import YAMLError
from events import *
class EmitterError(YAMLError):
pass
class Emitter:
def __init__(self, writer):
self.writer = writer
self.states = []
self.state = self.expect_stream_start
self.levels = []
self.level = 0
self.soft_space = False
def emit(self, event):
self.state(event)
def expect_stream_start(self, event):
if isinstance(event, StreamStartEvent):
self.state = self.expect_document_start
else:
raise EmitterError("expected StreamStartEvent, but got %s" % event.__class__.__name__)
def expect_document_start(self, event):
if isinstance(event, DocumentStartEvent):
self.write_document_start()
self.states.append(self.expect_document_end)
self.state = self.expect_root_node
elif isinstance(event, StreamEndEvent):
self.writer.flush()
self.state = self.expect_nothing
else:
raise EmitterError("expected DocumentStartEvent, but got %s" % event.__class__.__name__)
def expect_document_end(self, event):
if isinstance(event, DocumentEndEvent):
self.write_document_end()
self.state = self.expect_document_start
else:
raiseEmitterError("expected DocumentEndEvent, but got %s" % event.__class__.__name__)
def expect_root_node(self, event):
self.expect_node(event)
def expect_node(self, event):
if isinstance(event, AliasEvent):
self.write_anchor("*", event.anchor)
self.state = self.states.pop()
elif isinstance(event, NodeEvent):
if event.anchor:
self.write_anchor("&", event.anchor)
if event.tag:
self.write_tag(event.tag)
if isinstance(event, ScalarEvent):
self.write_scalar(event.value)
self.state = self.states.pop()
elif isinstance(event, SequenceEvent):
self.write_collection_start("[")
self.level += 1
self.state = self.expect_first_sequence_item
elif isinstance(event, MappingEvent):
self.write_collection_start("{")
self.level += 1
self.state = self.expect_first_mapping_key
else:
raise EmitterError("Expected NodeEvent, but got %s" % event.__class__.__name__)
def expect_first_sequence_item(self, event):
if isinstance(event, CollectionEndEvent):
self.write_collection_end("]")
self.state = self.states.pop()
else:
self.write_indent()
self.states.append(self.expect_sequence_item)
self.expect_node(event)
def expect_sequence_item(self, event):
if isinstance(event, CollectionEndEvent):
self.level -= 1
self.write_indent()
self.write_collection_end("]")
self.state = self.states.pop()
else:
self.write_indicator(",")
self.write_indent()
self.states.append(self.expect_sequence_item)
self.expect_node(event)
def expect_first_mapping_key(self, event):
if isinstance(event, CollectionEndEvent):
self.write_collection_end("}")
self.state = self.states.pop()
else:
self.write_indent()
self.write_indicator("?")
self.states.append(self.expect_mapping_value)
self.expect_node(event)
def expect_mapping_key(self, event):
if isinstance(event, CollectionEndEvent):
self.level -= 1
self.write_indent()
self.write_collection_end("}")
self.state = self.states.pop()
else:
self.write_indicator(",")
self.write_indent()
self.write_indicator("?")
self.states.append(self.expect_mapping_value)
self.expect_node(event)
def expect_mapping_value(self, event):
self.write_indent()
self.write_indicator(":")
self.states.append(self.expect_mapping_key)
self.expect_node(event)
def expect_nothing(self, event):
raise EmitterError("expected nothing, but got %s" % event.__class__.__name__)
def write_document_start(self):
self.writer.write("%YAML 1.1\n")
self.writer.write("---")
self.soft_space = True
def write_document_end(self):
self.writer.write("\n...\n")
self.soft_space = False
def write_collection_start(self, indicator):
if self.soft_space:
self.writer.write(" ")
self.writer.write(indicator)
self.soft_space = False
def write_collection_end(self, indicator):
self.writer.write(indicator)
self.soft_space = True
def write_anchor(self, indicator, name):
if self.soft_space:
self.writer.write(" ")
self.writer.write("%s%s" % (indicator, name))
self.soft_space = True
def write_tag(self, tag):
if self.soft_space:
self.writer.write(" ")
if tag.startswith("tag:yaml.org,2002:"):
self.writer.write("!!%s" % tag[len("tag.yaml.org,2002:"):])
else:
self.writer.write("!<%s>" % tag)
self.soft_space = True
def write_scalar(self, value):
if self.soft_space:
self.writer.write(" ")
self.writer.write("\"%s\"" % value.encode('utf-8'))
self.soft_space = True
def write_indicator(self, indicator):
self.writer.write(indicator)
self.soft_space = True
def write_indent(self):
self.writer.write("\n"+" "*(self.level*2))
self.soft_space = False
|
