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# Emitter expects events obeying 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 ScalarAnalysis: 

def __init__(self, scalar, empty, multiline, 

allow_flow_plain, allow_block_plain, 

allow_single_quoted, allow_double_quoted, 

allow_block): 

self.scalar = scalar 

self.empty = empty 

self.multiline = multiline 

self.allow_flow_plain = allow_flow_plain 

self.allow_block_plain = allow_block_plain 

self.allow_single_quoted = allow_single_quoted 

self.allow_double_quoted = allow_double_quoted 

self.allow_block = allow_block 

 

class Emitter: 

 

DEFAULT_TAG_PREFIXES = { 

'!' : '!', 

'tag:yaml.org,2002:' : '!!', 

} 

 

def __init__(self, stream, canonical=None, indent=None, width=None, 

allow_unicode=None, line_break=None): 

 

# The stream should have the methods `write` and possibly `flush`. 

self.stream = stream 

 

# Encoding can be overriden by STREAM-START. 

self.encoding = None 

 

# Emitter is a state machine with a stack of states to handle nested 

# structures. 

self.states = [] 

self.state = self.expect_stream_start 

 

# Current event and the event queue. 

self.events = [] 

self.event = None 

 

# The current indentation level and the stack of previous indents. 

self.indents = [] 

self.indent = None 

 

# Flow level. 

self.flow_level = 0 

 

# Contexts. 

self.root_context = False 

self.sequence_context = False 

self.mapping_context = False 

self.simple_key_context = False 

 

# Characteristics of the last emitted character: 

# - current position. 

# - is it a whitespace? 

# - is it an indention character 

# (indentation space, '-', '?', or ':')? 

self.line = 0 

self.column = 0 

self.whitespace = True 

self.indention = True 

 

# Whether the document requires an explicit document indicator 

self.open_ended = False 

 

# Formatting details. 

self.canonical = canonical 

self.allow_unicode = allow_unicode 

self.best_indent = 2 

if indent and 1 < indent < 10: 

self.best_indent = indent 

self.best_width = 80 

if width and width > self.best_indent*2: 

self.best_width = width 

self.best_line_break = '\n' 

if line_break in ['\r', '\n', '\r\n']: 

self.best_line_break = line_break 

 

# Tag prefixes. 

self.tag_prefixes = None 

 

# Prepared anchor and tag. 

self.prepared_anchor = None 

self.prepared_tag = None 

 

# Scalar analysis and style. 

self.analysis = None 

self.style = None 

 

def dispose(self): 

# Reset the state attributes (to clear self-references) 

self.states = [] 

self.state = None 

 

def emit(self, event): 

self.events.append(event) 

while not self.need_more_events(): 

self.event = self.events.pop(0) 

self.state() 

self.event = None 

 

# In some cases, we wait for a few next events before emitting. 

 

def need_more_events(self): 

if not self.events: 

return True 

event = self.events[0] 

if isinstance(event, DocumentStartEvent): 

return self.need_events(1) 

elif isinstance(event, SequenceStartEvent): 

return self.need_events(2) 

elif isinstance(event, MappingStartEvent): 

return self.need_events(3) 

else: 

return False 

 

def need_events(self, count): 

level = 0 

for event in self.events[1:]: 

if isinstance(event, (DocumentStartEvent, CollectionStartEvent)): 

level += 1 

elif isinstance(event, (DocumentEndEvent, CollectionEndEvent)): 

level -= 1 

elif isinstance(event, StreamEndEvent): 

level = -1 

if level < 0: 

return False 

return (len(self.events) < count+1) 

 

def increase_indent(self, flow=False, indentless=False): 

self.indents.append(self.indent) 

if self.indent is None: 

if flow: 

self.indent = self.best_indent 

else: 

self.indent = 0 

elif not indentless: 

self.indent += self.best_indent 

 

# States. 

 

# Stream handlers. 

 

def expect_stream_start(self): 

if isinstance(self.event, StreamStartEvent): 

if self.event.encoding and not hasattr(self.stream, 'encoding'): 

self.encoding = self.event.encoding 

self.write_stream_start() 

self.state = self.expect_first_document_start 

else: 

raise EmitterError("expected StreamStartEvent, but got %s" 

% self.event) 

 

def expect_nothing(self): 

raise EmitterError("expected nothing, but got %s" % self.event) 

 

# Document handlers. 

 

def expect_first_document_start(self): 

return self.expect_document_start(first=True) 

 

def expect_document_start(self, first=False): 

if isinstance(self.event, DocumentStartEvent): 

if (self.event.version or self.event.tags) and self.open_ended: 

self.write_indicator('...', True) 

self.write_indent() 

if self.event.version: 

version_text = self.prepare_version(self.event.version) 

self.write_version_directive(version_text) 

self.tag_prefixes = self.DEFAULT_TAG_PREFIXES.copy() 

if self.event.tags: 

handles = sorted(self.event.tags.keys()) 

for handle in handles: 

prefix = self.event.tags[handle] 

self.tag_prefixes[prefix] = handle 

handle_text = self.prepare_tag_handle(handle) 

prefix_text = self.prepare_tag_prefix(prefix) 

self.write_tag_directive(handle_text, prefix_text) 

implicit = (first and not self.event.explicit and not self.canonical 

and not self.event.version and not self.event.tags 

and not self.check_empty_document()) 

if not implicit: 

self.write_indent() 

self.write_indicator('---', True) 

if self.canonical: 

self.write_indent() 

self.state = self.expect_document_root 

elif isinstance(self.event, StreamEndEvent): 

if self.open_ended: 

self.write_indicator('...', True) 

self.write_indent() 

self.write_stream_end() 

self.state = self.expect_nothing 

else: 

raise EmitterError("expected DocumentStartEvent, but got %s" 

% self.event) 

 

def expect_document_end(self): 

if isinstance(self.event, DocumentEndEvent): 

self.write_indent() 

if self.event.explicit: 

self.write_indicator('...', True) 

self.write_indent() 

self.flush_stream() 

self.state = self.expect_document_start 

else: 

raise EmitterError("expected DocumentEndEvent, but got %s" 

% self.event) 

 

def expect_document_root(self): 

self.states.append(self.expect_document_end) 

self.expect_node(root=True) 

 

# Node handlers. 

 

def expect_node(self, root=False, sequence=False, mapping=False, 

simple_key=False): 

self.root_context = root 

self.sequence_context = sequence 

self.mapping_context = mapping 

self.simple_key_context = simple_key 

if isinstance(self.event, AliasEvent): 

self.expect_alias() 

elif isinstance(self.event, (ScalarEvent, CollectionStartEvent)): 

self.process_anchor('&') 

self.process_tag() 

if isinstance(self.event, ScalarEvent): 

self.expect_scalar() 

elif isinstance(self.event, SequenceStartEvent): 

if self.flow_level or self.canonical or self.event.flow_style \ 

or self.check_empty_sequence(): 

self.expect_flow_sequence() 

else: 

self.expect_block_sequence() 

elif isinstance(self.event, MappingStartEvent): 

if self.flow_level or self.canonical or self.event.flow_style \ 

or self.check_empty_mapping(): 

self.expect_flow_mapping() 

else: 

self.expect_block_mapping() 

else: 

raise EmitterError("expected NodeEvent, but got %s" % self.event) 

 

def expect_alias(self): 

if self.event.anchor is None: 

raise EmitterError("anchor is not specified for alias") 

self.process_anchor('*') 

self.state = self.states.pop() 

 

def expect_scalar(self): 

self.increase_indent(flow=True) 

self.process_scalar() 

self.indent = self.indents.pop() 

self.state = self.states.pop() 

 

# Flow sequence handlers. 

 

def expect_flow_sequence(self): 

self.write_indicator('[', True, whitespace=True) 

self.flow_level += 1 

self.increase_indent(flow=True) 

self.state = self.expect_first_flow_sequence_item 

 

def expect_first_flow_sequence_item(self): 

if isinstance(self.event, SequenceEndEvent): 

self.indent = self.indents.pop() 

self.flow_level -= 1 

self.write_indicator(']', False) 

self.state = self.states.pop() 

else: 

if self.canonical or self.column > self.best_width: 

self.write_indent() 

self.states.append(self.expect_flow_sequence_item) 

self.expect_node(sequence=True) 

 

def expect_flow_sequence_item(self): 

if isinstance(self.event, SequenceEndEvent): 

self.indent = self.indents.pop() 

self.flow_level -= 1 

if self.canonical: 

self.write_indicator(',', False) 

self.write_indent() 

self.write_indicator(']', False) 

self.state = self.states.pop() 

else: 

self.write_indicator(',', False) 

if self.canonical or self.column > self.best_width: 

self.write_indent() 

self.states.append(self.expect_flow_sequence_item) 

self.expect_node(sequence=True) 

 

# Flow mapping handlers. 

 

def expect_flow_mapping(self): 

self.write_indicator('{', True, whitespace=True) 

self.flow_level += 1 

self.increase_indent(flow=True) 

self.state = self.expect_first_flow_mapping_key 

 

def expect_first_flow_mapping_key(self): 

if isinstance(self.event, MappingEndEvent): 

self.indent = self.indents.pop() 

self.flow_level -= 1 

self.write_indicator('}', False) 

self.state = self.states.pop() 

else: 

if self.canonical or self.column > self.best_width: 

self.write_indent() 

if not self.canonical and self.check_simple_key(): 

self.states.append(self.expect_flow_mapping_simple_value) 

self.expect_node(mapping=True, simple_key=True) 

else: 

self.write_indicator('?', True) 

self.states.append(self.expect_flow_mapping_value) 

self.expect_node(mapping=True) 

 

def expect_flow_mapping_key(self): 

if isinstance(self.event, MappingEndEvent): 

self.indent = self.indents.pop() 

self.flow_level -= 1 

if self.canonical: 

self.write_indicator(',', False) 

self.write_indent() 

self.write_indicator('}', False) 

self.state = self.states.pop() 

else: 

self.write_indicator(',', False) 

if self.canonical or self.column > self.best_width: 

self.write_indent() 

if not self.canonical and self.check_simple_key(): 

self.states.append(self.expect_flow_mapping_simple_value) 

self.expect_node(mapping=True, simple_key=True) 

else: 

self.write_indicator('?', True) 

self.states.append(self.expect_flow_mapping_value) 

self.expect_node(mapping=True) 

 

def expect_flow_mapping_simple_value(self): 

self.write_indicator(':', False) 

self.states.append(self.expect_flow_mapping_key) 

self.expect_node(mapping=True) 

 

def expect_flow_mapping_value(self): 

if self.canonical or self.column > self.best_width: 

self.write_indent() 

self.write_indicator(':', True) 

self.states.append(self.expect_flow_mapping_key) 

self.expect_node(mapping=True) 

 

# Block sequence handlers. 

 

def expect_block_sequence(self): 

indentless = (self.mapping_context and not self.indention) 

self.increase_indent(flow=False, indentless=indentless) 

self.state = self.expect_first_block_sequence_item 

 

def expect_first_block_sequence_item(self): 

return self.expect_block_sequence_item(first=True) 

 

def expect_block_sequence_item(self, first=False): 

if not first and isinstance(self.event, SequenceEndEvent): 

self.indent = self.indents.pop() 

self.state = self.states.pop() 

else: 

self.write_indent() 

self.write_indicator('-', True, indention=True) 

self.states.append(self.expect_block_sequence_item) 

self.expect_node(sequence=True) 

 

# Block mapping handlers. 

 

def expect_block_mapping(self): 

self.increase_indent(flow=False) 

self.state = self.expect_first_block_mapping_key 

 

def expect_first_block_mapping_key(self): 

return self.expect_block_mapping_key(first=True) 

 

def expect_block_mapping_key(self, first=False): 

if not first and isinstance(self.event, MappingEndEvent): 

self.indent = self.indents.pop() 

self.state = self.states.pop() 

else: 

self.write_indent() 

if self.check_simple_key(): 

self.states.append(self.expect_block_mapping_simple_value) 

self.expect_node(mapping=True, simple_key=True) 

else: 

self.write_indicator('?', True, indention=True) 

self.states.append(self.expect_block_mapping_value) 

self.expect_node(mapping=True) 

 

def expect_block_mapping_simple_value(self): 

self.write_indicator(':', False) 

self.states.append(self.expect_block_mapping_key) 

self.expect_node(mapping=True) 

 

def expect_block_mapping_value(self): 

self.write_indent() 

self.write_indicator(':', True, indention=True) 

self.states.append(self.expect_block_mapping_key) 

self.expect_node(mapping=True) 

 

# Checkers. 

 

def check_empty_sequence(self): 

return (isinstance(self.event, SequenceStartEvent) and self.events 

and isinstance(self.events[0], SequenceEndEvent)) 

 

def check_empty_mapping(self): 

return (isinstance(self.event, MappingStartEvent) and self.events 

and isinstance(self.events[0], MappingEndEvent)) 

 

def check_empty_document(self): 

if not isinstance(self.event, DocumentStartEvent) or not self.events: 

return False 

event = self.events[0] 

return (isinstance(event, ScalarEvent) and event.anchor is None 

and event.tag is None and event.implicit and event.value == '') 

 

def check_simple_key(self): 

length = 0 

if isinstance(self.event, NodeEvent) and self.event.anchor is not None: 

if self.prepared_anchor is None: 

self.prepared_anchor = self.prepare_anchor(self.event.anchor) 

length += len(self.prepared_anchor) 

if isinstance(self.event, (ScalarEvent, CollectionStartEvent)) \ 

and self.event.tag is not None: 

if self.prepared_tag is None: 

self.prepared_tag = self.prepare_tag(self.event.tag) 

length += len(self.prepared_tag) 

if isinstance(self.event, ScalarEvent): 

if self.analysis is None: 

self.analysis = self.analyze_scalar(self.event.value) 

length += len(self.analysis.scalar) 

return (length < 128 and (isinstance(self.event, AliasEvent) 

or (isinstance(self.event, ScalarEvent) 

and not self.analysis.empty and not self.analysis.multiline) 

or self.check_empty_sequence() or self.check_empty_mapping())) 

 

# Anchor, Tag, and Scalar processors. 

 

def process_anchor(self, indicator): 

if self.event.anchor is None: 

self.prepared_anchor = None 

return 

if self.prepared_anchor is None: 

self.prepared_anchor = self.prepare_anchor(self.event.anchor) 

if self.prepared_anchor: 

self.write_indicator(indicator+self.prepared_anchor, True) 

self.prepared_anchor = None 

 

def process_tag(self): 

tag = self.event.tag 

if isinstance(self.event, ScalarEvent): 

if self.style is None: 

self.style = self.choose_scalar_style() 

if ((not self.canonical or tag is None) and 

((self.style == '' and self.event.implicit[0]) 

or (self.style != '' and self.event.implicit[1]))): 

self.prepared_tag = None 

return 

if self.event.implicit[0] and tag is None: 

tag = '!' 

self.prepared_tag = None 

else: 

if (not self.canonical or tag is None) and self.event.implicit: 

self.prepared_tag = None 

return 

if tag is None: 

raise EmitterError("tag is not specified") 

if self.prepared_tag is None: 

self.prepared_tag = self.prepare_tag(tag) 

if self.prepared_tag: 

self.write_indicator(self.prepared_tag, True) 

self.prepared_tag = None 

 

def choose_scalar_style(self): 

if self.analysis is None: 

self.analysis = self.analyze_scalar(self.event.value) 

if self.event.style == '"' or self.canonical: 

return '"' 

if not self.event.style and self.event.implicit[0]: 

if (not (self.simple_key_context and 

(self.analysis.empty or self.analysis.multiline)) 

and (self.flow_level and self.analysis.allow_flow_plain 

or (not self.flow_level and self.analysis.allow_block_plain))): 

return '' 

if self.event.style and self.event.style in '|>': 

if (not self.flow_level and not self.simple_key_context 

and self.analysis.allow_block): 

return self.event.style 

if not self.event.style or self.event.style == '\'': 

if (self.analysis.allow_single_quoted and 

not (self.simple_key_context and self.analysis.multiline)): 

return '\'' 

return '"' 

 

def process_scalar(self): 

if self.analysis is None: 

self.analysis = self.analyze_scalar(self.event.value) 

if self.style is None: 

self.style = self.choose_scalar_style() 

split = (not self.simple_key_context) 

#if self.analysis.multiline and split \ 

# and (not self.style or self.style in '\'\"'): 

# self.write_indent() 

if self.style == '"': 

self.write_double_quoted(self.analysis.scalar, split) 

elif self.style == '\'': 

self.write_single_quoted(self.analysis.scalar, split) 

elif self.style == '>': 

self.write_folded(self.analysis.scalar) 

elif self.style == '|': 

self.write_literal(self.analysis.scalar) 

else: 

self.write_plain(self.analysis.scalar, split) 

self.analysis = None 

self.style = None 

 

# Analyzers. 

 

def prepare_version(self, version): 

major, minor = version 

if major != 1: 

raise EmitterError("unsupported YAML version: %d.%d" % (major, minor)) 

return '%d.%d' % (major, minor) 

 

def prepare_tag_handle(self, handle): 

if not handle: 

raise EmitterError("tag handle must not be empty") 

if handle[0] != '!' or handle[-1] != '!': 

raise EmitterError("tag handle must start and end with '!': %r" % handle) 

for ch in handle[1:-1]: 

if not ('0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z' \ 

or ch in '-_'): 

raise EmitterError("invalid character %r in the tag handle: %r" 

% (ch, handle)) 

return handle 

 

def prepare_tag_prefix(self, prefix): 

if not prefix: 

raise EmitterError("tag prefix must not be empty") 

chunks = [] 

start = end = 0 

if prefix[0] == '!': 

end = 1 

while end < len(prefix): 

ch = prefix[end] 

if '0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z' \ 

or ch in '-;/?!:@&=+$,_.~*\'()[]': 

end += 1 

else: 

if start < end: 

chunks.append(prefix[start:end]) 

start = end = end+1 

data = ch.encode('utf-8') 

for ch in data: 

chunks.append('%%%02X' % ord(ch)) 

if start < end: 

chunks.append(prefix[start:end]) 

return ''.join(chunks) 

 

def prepare_tag(self, tag): 

if not tag: 

raise EmitterError("tag must not be empty") 

if tag == '!': 

return tag 

handle = None 

suffix = tag 

prefixes = sorted(self.tag_prefixes.keys()) 

for prefix in prefixes: 

if tag.startswith(prefix) \ 

and (prefix == '!' or len(prefix) < len(tag)): 

handle = self.tag_prefixes[prefix] 

suffix = tag[len(prefix):] 

chunks = [] 

start = end = 0 

while end < len(suffix): 

ch = suffix[end] 

if '0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z' \ 

or ch in '-;/?:@&=+$,_.~*\'()[]' \ 

or (ch == '!' and handle != '!'): 

end += 1 

else: 

if start < end: 

chunks.append(suffix[start:end]) 

start = end = end+1 

data = ch.encode('utf-8') 

for ch in data: 

chunks.append('%%%02X' % ord(ch)) 

if start < end: 

chunks.append(suffix[start:end]) 

suffix_text = ''.join(chunks) 

if handle: 

return '%s%s' % (handle, suffix_text) 

else: 

return '!<%s>' % suffix_text 

 

def prepare_anchor(self, anchor): 

if not anchor: 

raise EmitterError("anchor must not be empty") 

for ch in anchor: 

if not ('0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z' \ 

or ch in '-_'): 

raise EmitterError("invalid character %r in the anchor: %r" 

% (ch, anchor)) 

return anchor 

 

def analyze_scalar(self, scalar): 

 

# Empty scalar is a special case. 

if not scalar: 

return ScalarAnalysis(scalar=scalar, empty=True, multiline=False, 

allow_flow_plain=False, allow_block_plain=True, 

allow_single_quoted=True, allow_double_quoted=True, 

allow_block=False) 

 

# Indicators and special characters. 

block_indicators = False 

flow_indicators = False 

line_breaks = False 

special_characters = False 

 

# Important whitespace combinations. 

leading_space = False 

leading_break = False 

trailing_space = False 

trailing_break = False 

break_space = False 

space_break = False 

 

# Check document indicators. 

if scalar.startswith('---') or scalar.startswith('...'): 

block_indicators = True 

flow_indicators = True 

 

# First character or preceded by a whitespace. 

preceeded_by_whitespace = True 

 

# Last character or followed by a whitespace. 

followed_by_whitespace = (len(scalar) == 1 or 

scalar[1] in '\0 \t\r\n\x85\u2028\u2029') 

 

# The previous character is a space. 

previous_space = False 

 

# The previous character is a break. 

previous_break = False 

 

index = 0 

while index < len(scalar): 

ch = scalar[index] 

 

# Check for indicators. 

if index == 0: 

# Leading indicators are special characters. 

if ch in '#,[]{}&*!|>\'\"%@`': 

flow_indicators = True 

block_indicators = True 

if ch in '?:': 

flow_indicators = True 

if followed_by_whitespace: 

block_indicators = True 

if ch == '-' and followed_by_whitespace: 

flow_indicators = True 

block_indicators = True 

else: 

# Some indicators cannot appear within a scalar as well. 

if ch in ',?[]{}': 

flow_indicators = True 

if ch == ':': 

flow_indicators = True 

if followed_by_whitespace: 

block_indicators = True 

if ch == '#' and preceeded_by_whitespace: 

flow_indicators = True 

block_indicators = True 

 

# Check for line breaks, special, and unicode characters. 

if ch in '\n\x85\u2028\u2029': 

line_breaks = True 

if not (ch == '\n' or '\x20' <= ch <= '\x7E'): 

if (ch == '\x85' or '\xA0' <= ch <= '\uD7FF' 

or '\uE000' <= ch <= '\uFFFD' 

or '\U00010000' <= ch < '\U0010ffff') and ch != '\uFEFF': 

unicode_characters = True 

if not self.allow_unicode: 

special_characters = True 

else: 

special_characters = True 

 

# Detect important whitespace combinations. 

if ch == ' ': 

if index == 0: 

leading_space = True 

if index == len(scalar)-1: 

trailing_space = True 

if previous_break: 

break_space = True 

previous_space = True 

previous_break = False 

elif ch in '\n\x85\u2028\u2029': 

if index == 0: 

leading_break = True 

if index == len(scalar)-1: 

trailing_break = True 

if previous_space: 

space_break = True 

previous_space = False 

previous_break = True 

else: 

previous_space = False 

previous_break = False 

 

# Prepare for the next character. 

index += 1 

preceeded_by_whitespace = (ch in '\0 \t\r\n\x85\u2028\u2029') 

followed_by_whitespace = (index+1 >= len(scalar) or 

scalar[index+1] in '\0 \t\r\n\x85\u2028\u2029') 

 

# Let's decide what styles are allowed. 

allow_flow_plain = True 

allow_block_plain = True 

allow_single_quoted = True 

allow_double_quoted = True 

allow_block = True 

 

# Leading and trailing whitespaces are bad for plain scalars. 

if (leading_space or leading_break 

or trailing_space or trailing_break): 

allow_flow_plain = allow_block_plain = False 

 

# We do not permit trailing spaces for block scalars. 

if trailing_space: 

allow_block = False 

 

# Spaces at the beginning of a new line are only acceptable for block 

# scalars. 

if break_space: 

allow_flow_plain = allow_block_plain = allow_single_quoted = False 

 

# Spaces followed by breaks, as well as special character are only 

# allowed for double quoted scalars. 

if space_break or special_characters: 

allow_flow_plain = allow_block_plain = \ 

allow_single_quoted = allow_block = False 

 

# Although the plain scalar writer supports breaks, we never emit 

# multiline plain scalars. 

if line_breaks: 

allow_flow_plain = allow_block_plain = False 

 

# Flow indicators are forbidden for flow plain scalars. 

if flow_indicators: 

allow_flow_plain = False 

 

# Block indicators are forbidden for block plain scalars. 

if block_indicators: 

allow_block_plain = False 

 

return ScalarAnalysis(scalar=scalar, 

empty=False, multiline=line_breaks, 

allow_flow_plain=allow_flow_plain, 

allow_block_plain=allow_block_plain, 

allow_single_quoted=allow_single_quoted, 

allow_double_quoted=allow_double_quoted, 

allow_block=allow_block) 

 

# Writers. 

 

def flush_stream(self): 

if hasattr(self.stream, 'flush'): 

self.stream.flush() 

 

def write_stream_start(self): 

# Write BOM if needed. 

if self.encoding and self.encoding.startswith('utf-16'): 

self.stream.write('\uFEFF'.encode(self.encoding)) 

 

def write_stream_end(self): 

self.flush_stream() 

 

def write_indicator(self, indicator, need_whitespace, 

whitespace=False, indention=False): 

if self.whitespace or not need_whitespace: 

data = indicator 

else: 

data = ' '+indicator 

self.whitespace = whitespace 

self.indention = self.indention and indention 

self.column += len(data) 

self.open_ended = False 

if self.encoding: 

data = data.encode(self.encoding) 

self.stream.write(data) 

 

def write_indent(self): 

indent = self.indent or 0 

if not self.indention or self.column > indent \ 

or (self.column == indent and not self.whitespace): 

self.write_line_break() 

if self.column < indent: 

self.whitespace = True 

data = ' '*(indent-self.column) 

self.column = indent 

if self.encoding: 

data = data.encode(self.encoding) 

self.stream.write(data) 

 

def write_line_break(self, data=None): 

if data is None: 

data = self.best_line_break 

self.whitespace = True 

self.indention = True 

self.line += 1 

self.column = 0 

if self.encoding: 

data = data.encode(self.encoding) 

self.stream.write(data) 

 

def write_version_directive(self, version_text): 

data = '%%YAML %s' % version_text 

if self.encoding: 

data = data.encode(self.encoding) 

self.stream.write(data) 

self.write_line_break() 

 

def write_tag_directive(self, handle_text, prefix_text): 

data = '%%TAG %s %s' % (handle_text, prefix_text) 

if self.encoding: 

data = data.encode(self.encoding) 

self.stream.write(data) 

self.write_line_break() 

 

# Scalar streams. 

 

def write_single_quoted(self, text, split=True): 

self.write_indicator('\'', True) 

spaces = False 

breaks = False 

start = end = 0 

while end <= len(text): 

ch = None 

if end < len(text): 

ch = text[end] 

if spaces: 

if ch is None or ch != ' ': 

if start+1 == end and self.column > self.best_width and split \ 

and start != 0 and end != len(text): 

self.write_indent() 

else: 

data = text[start:end] 

self.column += len(data) 

if self.encoding: 

data = data.encode(self.encoding) 

self.stream.write(data) 

start = end 

elif breaks: 

if ch is None or ch not in '\n\x85\u2028\u2029': 

if text[start] == '\n': 

self.write_line_break() 

for br in text[start:end]: 

if br == '\n': 

self.write_line_break() 

else: 

self.write_line_break(br) 

self.write_indent() 

start = end 

else: 

if ch is None or ch in ' \n\x85\u2028\u2029' or ch == '\'': 

if start < end: 

data = text[start:end] 

self.column += len(data) 

if self.encoding: 

data = data.encode(self.encoding) 

self.stream.write(data) 

start = end 

if ch == '\'': 

data = '\'\'' 

self.column += 2 

if self.encoding: 

data = data.encode(self.encoding) 

self.stream.write(data) 

start = end + 1 

if ch is not None: 

spaces = (ch == ' ') 

breaks = (ch in '\n\x85\u2028\u2029') 

end += 1 

self.write_indicator('\'', False) 

 

ESCAPE_REPLACEMENTS = { 

'\0': '0', 

'\x07': 'a', 

'\x08': 'b', 

'\x09': 't', 

'\x0A': 'n', 

'\x0B': 'v', 

'\x0C': 'f', 

'\x0D': 'r', 

'\x1B': 'e', 

'\"': '\"', 

'\\': '\\', 

'\x85': 'N', 

'\xA0': '_', 

'\u2028': 'L', 

'\u2029': 'P', 

} 

 

def write_double_quoted(self, text, split=True): 

self.write_indicator('"', True) 

start = end = 0 

while end <= len(text): 

ch = None 

if end < len(text): 

ch = text[end] 

if ch is None or ch in '"\\\x85\u2028\u2029\uFEFF' \ 

or not ('\x20' <= ch <= '\x7E' 

or (self.allow_unicode 

and ('\xA0' <= ch <= '\uD7FF' 

or '\uE000' <= ch <= '\uFFFD'))): 

if start < end: 

data = text[start:end] 

self.column += len(data) 

if self.encoding: 

data = data.encode(self.encoding) 

self.stream.write(data) 

start = end 

if ch is not None: 

if ch in self.ESCAPE_REPLACEMENTS: 

data = '\\'+self.ESCAPE_REPLACEMENTS[ch] 

elif ch <= '\xFF': 

data = '\\x%02X' % ord(ch) 

elif ch <= '\uFFFF': 

data = '\\u%04X' % ord(ch) 

else: 

data = '\\U%08X' % ord(ch) 

self.column += len(data) 

if self.encoding: 

data = data.encode(self.encoding) 

self.stream.write(data) 

start = end+1 

if 0 < end < len(text)-1 and (ch == ' ' or start >= end) \ 

and self.column+(end-start) > self.best_width and split: 

data = text[start:end]+'\\' 

if start < end: 

start = end 

self.column += len(data) 

if self.encoding: 

data = data.encode(self.encoding) 

self.stream.write(data) 

self.write_indent() 

self.whitespace = False 

self.indention = False 

if text[start] == ' ': 

data = '\\' 

self.column += len(data) 

if self.encoding: 

data = data.encode(self.encoding) 

self.stream.write(data) 

end += 1 

self.write_indicator('"', False) 

 

def determine_block_hints(self, text): 

hints = '' 

if text: 

if text[0] in ' \n\x85\u2028\u2029': 

hints += str(self.best_indent) 

if text[-1] not in '\n\x85\u2028\u2029': 

hints += '-' 

elif len(text) == 1 or text[-2] in '\n\x85\u2028\u2029': 

hints += '+' 

return hints 

 

def write_folded(self, text): 

hints = self.determine_block_hints(text) 

self.write_indicator('>'+hints, True) 

if hints[-1:] == '+': 

self.open_ended = True 

self.write_line_break() 

leading_space = True 

spaces = False 

breaks = True 

start = end = 0 

while end <= len(text): 

ch = None 

if end < len(text): 

ch = text[end] 

if breaks: 

if ch is None or ch not in '\n\x85\u2028\u2029': 

if not leading_space and ch is not None and ch != ' ' \ 

and text[start] == '\n': 

self.write_line_break() 

leading_space = (ch == ' ') 

for br in text[start:end]: 

if br == '\n': 

self.write_line_break() 

else: 

self.write_line_break(br) 

if ch is not None: 

self.write_indent() 

start = end 

elif spaces: 

if ch != ' ': 

if start+1 == end and self.column > self.best_width: 

self.write_indent() 

else: 

data = text[start:end] 

self.column += len(data) 

if self.encoding: 

data = data.encode(self.encoding) 

self.stream.write(data) 

start = end 

else: 

if ch is None or ch in ' \n\x85\u2028\u2029': 

data = text[start:end] 

self.column += len(data) 

if self.encoding: 

data = data.encode(self.encoding) 

self.stream.write(data) 

if ch is None: 

self.write_line_break() 

start = end 

if ch is not None: 

breaks = (ch in '\n\x85\u2028\u2029') 

spaces = (ch == ' ') 

end += 1 

 

def write_literal(self, text): 

hints = self.determine_block_hints(text) 

self.write_indicator('|'+hints, True) 

if hints[-1:] == '+': 

self.open_ended = True 

self.write_line_break() 

breaks = True 

start = end = 0 

while end <= len(text): 

ch = None 

if end < len(text): 

ch = text[end] 

if breaks: 

if ch is None or ch not in '\n\x85\u2028\u2029': 

for br in text[start:end]: 

if br == '\n': 

self.write_line_break() 

else: 

self.write_line_break(br) 

if ch is not None: 

self.write_indent() 

start = end 

else: 

if ch is None or ch in '\n\x85\u2028\u2029': 

data = text[start:end] 

if self.encoding: 

data = data.encode(self.encoding) 

self.stream.write(data) 

if ch is None: 

self.write_line_break() 

start = end 

if ch is not None: 

breaks = (ch in '\n\x85\u2028\u2029') 

end += 1 

 

def write_plain(self, text, split=True): 

if self.root_context: 

self.open_ended = True 

if not text: 

return 

if not self.whitespace: 

data = ' ' 

self.column += len(data) 

if self.encoding: 

data = data.encode(self.encoding) 

self.stream.write(data) 

self.whitespace = False 

self.indention = False 

spaces = False 

breaks = False 

start = end = 0 

while end <= len(text): 

ch = None 

if end < len(text): 

ch = text[end] 

if spaces: 

if ch != ' ': 

if start+1 == end and self.column > self.best_width and split: 

self.write_indent() 

self.whitespace = False 

self.indention = False 

else: 

data = text[start:end] 

self.column += len(data) 

if self.encoding: 

data = data.encode(self.encoding) 

self.stream.write(data) 

start = end 

elif breaks: 

if ch not in '\n\x85\u2028\u2029': 

if text[start] == '\n': 

self.write_line_break() 

for br in text[start:end]: 

if br == '\n': 

self.write_line_break() 

else: 

self.write_line_break(br) 

self.write_indent() 

self.whitespace = False 

self.indention = False 

start = end 

else: 

if ch is None or ch in ' \n\x85\u2028\u2029': 

data = text[start:end] 

self.column += len(data) 

if self.encoding: 

data = data.encode(self.encoding) 

self.stream.write(data) 

start = end 

if ch is not None: 

spaces = (ch == ' ') 

breaks = (ch in '\n\x85\u2028\u2029') 

end += 1