def encode(self, pad=0, header=True):
"""Encodes this cFS command to binary.
If pad is specified, it indicates the maximum size of the
encoded command in bytes. If the encoded command is less than
pad, the remaining bytes are set to zero.
The optional header argument controls whether or not a header
is prepended to the encoded command and offers several levels
of granularity. If False or None, no header is prepended. If
True, a CCSDS header is computed based on the `APID` found in
the command's corresponding :class:`CmdDefn`. To control the
CCSDS sequence count (`seqcount`) only set header to an
instance of :class:`CcsdsHeader` with the desired `seqcount`.
For complete control over the header contents, set header to a
bytearray.
NOTE: This method sets the cFS command checksum byte to zero
in accordance with the current cFS ground system tools and cFE
source code. That is, as far as we can tell, the checksum is
not used.
"""
checksum = 0
secondary = struct.pack('BB', checksum, self.defn.opcode)
offset = len(secondary)
size = max(offset + self.defn.argsize, pad)
encoded = bytearray(size)
encoded[0:offset] = secondary
index = 0
for defn in self.defn.argdefns:
if defn.fixed:
value = defn.value
else:
value = self.args[index]
index += 1
encoded[ defn.slice(offset) ] = defn.encode(value)
if header is True:
header = ccsds.CcsdsHeader()
if isinstance(header, ccsds.CcsdsHeader):
header.type = 1
header.apid = self.defn.ccsds.apid if self.defn.ccsds else 0
header.shflag = 1
header.seqflags = 0b11
print 'len(encoded) =', len(encoded)
header.length = len(encoded) - 1
header = header._data
if isinstance(header, bytearray):
encoded = header + encoded
return encoded
def testCcsdsHeaderDecode():
header = ccsds.CcsdsHeader([0x18, 0x2A, 0xC4, 0xD2, 0x16, 0x2E])
assert header.version == 0
assert header.type == 1
assert header.shflag == 1
assert header.apid == 42
assert header.raw.seqflags == 0b11
assert header.seqcount == 1234
assert header.length == 5678
def testCcsdsHeaderDefaults():
header = ccsds.CcsdsHeader()
assert header.version == 0
assert header.type == 0
assert header.shflag == 0
assert header.apid == 0
assert header.raw.seqflags == 0b11
assert header.seqcount == 0
assert header.length == 0
def testCcsdsHeaderEncode():
header = ccsds.CcsdsHeader()
header.version = 0
header.type = 1
header.shflag = 1
header.apid = 42
header.seqflags = 0b11
header.seqcount = 1234
header.length = 5678
assert header._data == bytearray([0x18, 0x2A, 0xC4, 0xD2, 0x16, 0x2E])
