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+# nxt.telegram module -- LEGO Mindstorms NXT telegram formatting and parsing
+# Copyright (C) 2006 Douglas P Lau
+# Copyright (C) 2009 Marcus Wanner
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+
+'Used by nxt.system for sending telegrams to the NXT'
+
+from cStringIO import StringIO
+from struct import pack, unpack
+import nxt.error
+
+class InvalidReplyError(Exception):
+ pass
+
+class InvalidOpcodeError(Exception):
+ pass
+
+class Telegram(object):
+
+ TYPE = 0 # type byte offset
+ CODE = 1 # code byte offset
+ DATA = 2 # data byte offset
+
+ TYPE_NOT_DIRECT = 0x01 # system vs. direct type
+ TYPE_REPLY = 0x02 # reply type (from NXT brick)
+ TYPE_REPLY_NOT_REQUIRED = 0x80 # reply not required flag
+
+ def __init__(self, direct=False, opcode=0, reply_req=True, pkt=None):
+ if pkt:
+ self.pkt = StringIO(pkt)
+ self.typ = self.parse_u8()
+ self.opcode = self.parse_u8()
+ if not self.is_reply():
+ raise InvalidReplyError
+ if self.opcode != opcode:
+ raise InvalidOpcodeError, self.opcode
+ else:
+ self.pkt = StringIO()
+ typ = 0
+ if not direct:
+ typ |= Telegram.TYPE_NOT_DIRECT
+ if not reply_req:
+ typ |= Telegram.TYPE_REPLY_NOT_REQUIRED
+ self.add_u8(typ)
+ self.add_u8(opcode)
+
+ def __str__(self):
+ return self.pkt.getvalue()
+
+ def is_reply(self):
+ return self.typ == Telegram.TYPE_REPLY
+
+ def add_string(self, n_bytes, v):
+ self.pkt.write(pack('%ds' % n_bytes, v))
+
+ def add_filename(self, fname):
+ self.pkt.write(pack('20s', fname))
+
+ def add_s8(self, v):
+ self.pkt.write(pack('<b', v))
+
+ def add_u8(self, v):
+ self.pkt.write(pack('<B', v))
+
+ def add_s16(self, v):
+ self.pkt.write(pack('<h', v))
+
+ def add_u16(self, v):
+ self.pkt.write(pack('<H', v))
+
+ def add_s32(self, v):
+ self.pkt.write(pack('<i', v))
+
+ def add_u32(self, v):
+ self.pkt.write(pack('<I', v))
+
+ def parse_string(self, n_bytes=0):
+ if n_bytes:
+ return unpack('%ss' % n_bytes,
+ self.pkt.read(n_bytes))[0]
+ else:
+ return self.pkt.read()
+
+ def parse_s8(self):
+ return unpack('<b', self.pkt.read(1))[0]
+
+ def parse_u8(self):
+ return unpack('<B', self.pkt.read(1))[0]
+
+ def parse_s16(self):
+ return unpack('<h', self.pkt.read(2))[0]
+
+ def parse_u16(self):
+ return unpack('<H', self.pkt.read(2))[0]
+
+ def parse_s32(self):
+ return unpack('<i', self.pkt.read(4))[0]
+
+ def parse_u32(self):
+ return unpack('<I', self.pkt.read(4))[0]
+
+ def check_status(self):
+ nxt.error.check_status(self.parse_u8())
+
+import nxt.direct
+import nxt.system
+
+OPCODES = dict(nxt.system.OPCODES)
+OPCODES.update(nxt.direct.OPCODES)