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|
""" Snapcast messages. """
from construct import (ULInt8, ULInt16, ULInt32, ULInt64,
Embed, Struct, Enum, Array,
PascalString, Switch, Container)
ENCODING = 'utf-8'
BASE_SIZE = 26
# pylint: disable=bad-continuation,invalid-name
timestamp = Embed(Struct('time',
ULInt32('secs'),
ULInt32('usecs')
))
snaptype = Enum(ULInt16('type'),
Base=0,
Header=1,
WireChunk=2,
SampleFormat=3,
ServerSettings=4,
Time=5,
Request=6,
Ack=7,
Command=8,
Hello=9,
Map=10,
String=11
)
basemessage = Struct('base',
snaptype,
ULInt16('id'),
ULInt16('refer'),
Struct('sent', timestamp),
Struct('recv', timestamp),
ULInt32('payload_length'),
)
mapmessage = Struct('map',
ULInt16('num'),
Array(lambda ctx: ctx.num, Struct('map',
PascalString('field', length_field=ULInt16('length')),
PascalString('value', length_field=ULInt16('length'))
))
)
stringmessage = Struct('string',
PascalString('string', length_field=ULInt16('string_length'))
)
request = Struct('request',
Struct('request_type', Embed(snaptype))
)
server_settings = Struct('settings',
ULInt32('buffer_ms'),
ULInt32('latency'),
ULInt16('volume'),
ULInt8('mute')
)
sample_format = Struct('sample',
ULInt32('rate'),
ULInt16('bits'),
ULInt16('channels'),
ULInt16('sample_size'),
ULInt16('frame_size')
)
header = Struct('header',
PascalString('codec', length_field=ULInt16('codec_length')),
PascalString('header', length_field=ULInt32('header_length'))
)
time = Struct('header',
ULInt64('latency')
)
chunk = Struct('chunk',
Struct('timestamp', timestamp),
PascalString('chunk', length_field=ULInt32('chunk_length'))
)
hello = mapmessage
command = stringmessage
ack = stringmessage
packet = Struct('packet',
Embed(basemessage),
Switch('payload', lambda ctx: ctx.type,
{
'Header': header,
'Time': time,
'WireChunk': chunk,
'SampleFormat': sample_format,
'ServerSettings': server_settings,
'Request': request,
'Hello': hello,
'Command': command,
'Ack': ack
}
)
)
# pylint: enable=bad-continuation,invalid-name
def message(message_type, payload, payload_length):
""" Build a message. """
return packet.build(
Container(
type=message_type,
id=1,
refer=0,
sent=Container(
secs=0,
usecs=0
),
recv=Container(
secs=0,
usecs=0
),
payload_length=payload_length,
payload=payload
)
)
def map_helper(data):
""" Build a map message. """
as_list = []
length = 2
for field, value in data.items():
as_list.append(Container(field=bytes(field, ENCODING),
value=bytes(value, ENCODING)))
length += len(field) + len(value) + 4
return (Container(
num=len(as_list),
map=as_list
), length)
def hello_packet(hostname, mac, version):
""" Build a hello message. """
return message('Hello', *map_helper({
'HostName': hostname,
'MAC': mac,
'Version': version
}))
def request_packet(request_type):
""" Build a request message. """
return message('Request', Container(request_type=request_type), 2)
def command_packet(cmd):
""" Build a command message. """
return message('Command',
Container(string_length=len(cmd),
string=bytes(cmd, ENCODING)),
len(cmd) + 2)
|
