def set_length(self, buf):
"""Set the length of the variable-width encoding."""
self.length = compat.from_bytes(buf.read(self.width), "big")
buf.seek(self.length, os.SEEK_CUR)
# Update the offset with the length indicator.
self.offset += self.width
def decode_constructor(read):
"""Decodes the constructor of an AMQP-encoded value at the beginning
of the datastream in file-like object `buf`. Return a tuple indicating
the format code, width, length, symbolic and numeric decriptor.
Args:
read: a callable that accepts an integer as its argument, indicating
the number of octets to be read from the stream, and returns
a :class:`bytes` object of equal length to the input value.
Returns:
Constructor
Raises:
EOFError: may be raised by invoking `read()`.
"""
symbolic = None
numeric = None
raw_format_code = read(1)
if not raw_format_code:
raise EOFError("End of AMQP-encoded datastream")
# The first octet indicates the format code type; 0 for described
# format codes, non-zero for codec.
format_code = compat.from_bytes(raw_format_code, ENDIAN)
if format_code == 0x00:
# If the value has a described format code, its descriptor is
# either an unsigned long integer, or a symbol.
format_code = compat.from_bytes(read(1), ENDIAN)
if format_code in (ULONG, SMALLULONG):
numeric =\
compat.from_bytes(read_stream(format_code, read), ENDIAN)
elif format_code in (SYM8, SYM32):
#: Symbol is encoded as ASCII (OASIS 2012: 25).
symbolic = read_stream(format_code, read)\
.decode('ascii')
else:
raise ValueError(
"Invalid format code for descriptor: " + str(format_code)
)
# Right after the descriptor comes the actual primitive type
# of the encoded value.
format_code = compat.from_bytes(read(1), ENDIAN)
return Constructor(format_code, symbolic, numeric)
def set_members(self, buf):
"""Read the size and count indicator from the buffer."""
self.member_size = compat.from_bytes(buf.read(self.width), "big")
self.member_count = compat.from_bytes(buf.read(self.width), "big")
start = buf.tell() - self.width
if self.is_array():
self.member_ctr = decode_constructor(buf.read)
# Set the start of the members to the current buffer position
# minus the width of the type length, because the total length
# includes.
end = start + self.member_size
while buf.tell() < end:
node = type(self).frombuf(buf, parent=self, ctr=self.member_ctr, depth=self.depth)
self.children.append(node)
assert buf.tell() == end, "{0}!={1}".format(buf.tell(), end)
def read_variable(format_code, read):
"""Read a variable-length value from an AMQP-encoded datastream.
Args:
read: a callable that accepts an integer as its argument, indicating
the number of octets to be read from the stream, and returns
a :class:`bytes` object of equal length to the input value.
format_code (:class:`int`): an AMQP primitive type format
code.
Returns:
bytes
"""
n = compat.from_bytes(read(get_type_length(format_code)), ENDIAN)
return read(n)
def decode_boolean(format_code, value):
return (format_code == const.TRUE) or (compat.from_bytes(value, "big") == 1)
def decode_integer(signed, format_code, value):
return compat.from_bytes(value, "big", signed=signed)
