def index_tag(tag, data, start=0):
"""
Finds a tag in an encoded message byte string.
:param tag: The tag number to find.
:param data: The encoded FIX message data to search.
:param start: Optimization: position at which to start the search.
:return: A tuple consisting of the tag value, the index at which the tag was found, and the index that
denotes the end of the field in the byte string.
:raises: TagNotFound if the tag could not be found in the encoded message data.
"""
search_bytes = encode(tag) + b"="
if data.startswith(search_bytes):
start_of_field = 0
else:
# Ensure that the tag is prefixed by SOH to avoid partial matches.
search_bytes = settings.SOH + search_bytes
try:
start_of_field = data.index(search_bytes, start)
except ValueError as e:
raise TagNotFound(tag, data) from e
end_of_field = data.find(settings.SOH, start_of_field + 1)
return (
data[start_of_field + len(search_bytes):end_of_field],
start_of_field,
end_of_field,
)
def __getattr__(self, name):
"""
Convenience method for retrieving fields using the field name (e.g. field.MsgType will try to
retrieve tag number 35).
:param name: The tag name.
:return: The Field in this FieldMap with name.
:raises UnknownTag if name is not defined in one of the available FIX specifications.
:raises TagNotFound if the tag name is valid, but no Field for that tag exists in the FieldMap.
"""
try:
# First, try to get the tag number associated with 'name'.
tag = connection.protocol.Tag.get_tag(name)
except UnknownTag as e:
# Not a known tag, ignore.
raise AttributeError(
f"{type(self).__name__} instance has no attribute '{name}'."
) from e
try:
# Then, see if a Field with that tag number is available in this FieldMap.
return self[tag]
except KeyError as e:
raise TagNotFound(tag, self,
f"Tag {tag} not found in {self!r}.") from e
def __getitem__(self, tag: int) -> Union[Field, list]:
items = [field for field in self.data if field.tag == tag]
if len(items) == 0:
raise TagNotFound(tag, self)
if len(items) == 1:
return items[0] # Return Field instead of a list of one.
return items
def __delitem__(self, tag: int):
count = self.count(tag)
if count > 1:
raise DuplicateTags(
tag,
self.values(),
message=f"Cannot delete Field by tag reference: "
f"FieldMap contains {count} occurrences of '{tag}'. "
f"Delete the Field(s) manually from 'data' instead.",
)
idx = 0
for field in self._data:
if field.tag == tag:
del self._data[idx]
return
idx += 1
raise TagNotFound(tag, self)
def rindex_tag(tag, data, start=0):
"""
Finds a tag in an encoded message byte string, searching from right to left.
:param tag: The tag number to find.
:param data: The encoded FIX message data to search.
:param start: Optimization: position at which to start the search.
:return: A tuple consisting of the tag value, the index at which the tag was found, and the index that
denotes the end of the field in the byte string.
:raises: TagNotFound if the tag could not be found in the encoded message data.
"""
search_bytes = encode(tag) + b"="
try:
start_of_field = data.rindex(search_bytes, start)
except ValueError as e:
raise TagNotFound(tag, data) from e
end_of_field = data.find(settings.SOH, start_of_field + 1)
return (
data[start_of_field + len(search_bytes):end_of_field],
start_of_field,
end_of_field,
)
def __delitem__(self, tag: int):
try:
del self._data[tag]
except KeyError:
raise TagNotFound(tag, self)
def __getitem__(self, tag: int):
try:
return self._data[tag] # Shortcut: lookup Field by tag
except KeyError:
raise TagNotFound(tag, self)
