378 lines
15 KiB
Python
378 lines
15 KiB
Python
'''
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=======================================
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Modified YMODEM file transfer protocol
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=======================================
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.. $Id$
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This is a implementation of YMODEM as used on the Cosmo Communicator.
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Data flow example
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=================
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Here is a sample of the data flow, sending a 3-block message.
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Batch Transmission Session (1 file - not tested with more than one)
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-------------------------------------------------------------------
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::
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SENDER RECEIVER
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<-- C (command:rb)
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SOH 00 FF foo.c NUL[123] CRC CRC -->
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<-- ACK
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SOH 01 FE Data[1024] CRC CRC --> (probably received garbled)
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<-- C
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SOH 01 FE Data[1024] CRC CRC (resend) --> (starts flash erase)
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<-- (empty read timed out)
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<-- (empty read timed out)
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<-- (empty read timed out)
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<-- C
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SOH 01 FE Data[1024] CRC CRC (resend) -->
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<-- ACK
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SOH 02 FC Data[1024] CRC CRC --> (probably received garbled)
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<-- C
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SOH 02 FC Data[1024] CRC CRC (resend) -->
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<-- ACK
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SOH 03 FB Data[1000] CPMEOF[24] CRC CRC -->
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<-- ACK
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EOT -->
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EOT -->
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EOT -->
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<-- C
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EOT -->
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EOT -->
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EOT -->
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<-- C
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EOT -->
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EOT -->
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EOT -->
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<-- C
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EOT -->
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EOT -->
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EOT -->
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<-- ACK
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'''
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from __future__ import division, print_function
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__author__ = 'Wijnand Modderman <maze@pyth0n.org>'
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__copyright__ = ['Copyright (c) 2010 Wijnand Modderman',
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'Copyright (c) 1981 Chuck Forsberg',
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'Copyright (c) 2016 Michael Tesch']
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__license__ = 'MIT'
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__version__ = '0.4.5'
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import platform
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import logging
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import time
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import sys
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import os
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# Protocol bytes
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NUL = b'\x00'
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SOH = b'\x01'
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STX = b'\x02'
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EOT = b'\x04'
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ACK = b'\x06'
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ACK2 = b'\x86'
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DLE = b'\x10'
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NAK = b'\x15'
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CAN = b'\x18'
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CAN2 = b'\x98'
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CRC = b'C' #0x43
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CRC2 = b'\xc3'
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CRC3 = b'\x83'
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ABT = b'a' #0x61 - flash fail - abort
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class YMODEM(object):
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'''
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YMODEM Protocol handler, expects two callables which encapsulate the read
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and write operations on the underlying stream.
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Example functions for reading and writing to a serial line:
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>>> import serial
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>>> from xmodem import YMODEM
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>>> ser = serial.Serial('/dev/ttyUSB0', timeout=0) # or whatever you need
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>>> modem = YMODEM(ser)
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:param ser: serial port to read from or write to.
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:type getc: class
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:type mode: string
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:param pad: Padding character to make the packets match the packet size
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:type pad: char
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'''
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# crctab calculated by Mark G. Mendel, Network Systems Corporation
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crctable = [
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0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7,
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0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef,
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0x1231, 0x0210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6,
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0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de,
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0x2462, 0x3443, 0x0420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485,
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0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d,
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0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6, 0x5695, 0x46b4,
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0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc,
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0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823,
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0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b,
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0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0x0a50, 0x3a33, 0x2a12,
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0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a,
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0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0x0c60, 0x1c41,
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0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49,
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0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70,
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0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78,
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0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f,
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0x1080, 0x00a1, 0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067,
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0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e,
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0x02b1, 0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256,
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0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d,
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0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
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0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e, 0xc71d, 0xd73c,
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0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634,
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0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab,
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0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x08e1, 0x3882, 0x28a3,
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0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a,
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0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0, 0x2ab3, 0x3a92,
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0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9,
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0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1,
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0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8,
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0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0,
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]
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def __init__(self, ser, pad=b'\x1a'):
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self.ser = ser
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self.pad = pad
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self.log = logging.getLogger('codiUpdate')
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def abort(self, count=2, timeout=60):
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'''
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Send an abort sequence using CAN bytes.
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:param count: how many abort characters to send
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:type count: int
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:param timeout: timeout in seconds
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:type timeout: int
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'''
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for _ in range(count):
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self.ser.write(CAN)
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def send(self, filename, retry=20, timeout=60, quiet=False, callback=None):
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'''
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Send a stream via the YMODEM protocol.
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>>> print(modem.send('filename'))
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True
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Returns ``True`` upon successful transmission or ``False`` in case of
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failure.
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:param stream: The stream object to send data from.
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:type stream: stream (file, etc.)
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:param retry: The maximum number of times to try to resend a failed
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packet before failing.
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:type retry: int
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:param timeout: The number of seconds to wait for a response before
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timing out.
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:type timeout: int
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:param quiet: If True, write transfer information to stderr.
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:type quiet: bool
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:param callback: Reference to a callback function that has the
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following signature. This is useful for
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getting status updates while a ymodem
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transfer is underway.
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Expected callback signature:
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def callback(total_packets, success_count, error_count, total)
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:type callback: callable
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'''
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# initialize protocol
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packet_size = 1024
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self.log.debug('Begin start sequence, packet_size=%d', packet_size)
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error_count = 0
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crc_mode = 0
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cancel = 0
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while True:
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char = self.ser.read(1)
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if char:
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if char == NAK:
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self.log.debug('standard checksum requested (NAK).')
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crc_mode = 0
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break
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elif char == CRC:
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self.log.debug('16-bit CRC requested (CRC).')
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crc_mode = 1
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break
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elif char == CAN or char == CAN2:
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if not quiet:
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print('received CAN', file=sys.stderr)
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if cancel:
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self.log.info('Transmission canceled: received 2xCAN '
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'at start-sequence')
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return False
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else:
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self.log.debug('cancellation at start sequence.')
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cancel = 1
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else:
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self.log.error('send error: expected NAK, CRC, or CAN; '
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'got %r', char)
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error_count += 1
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if error_count > retry:
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self.log.info('send error: error_count reached %d, '
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'aborting.', retry)
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self.abort(timeout=timeout)
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return False
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# send data
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error_count = 0
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success_count = 0
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total_packets = 0
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total = 0
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header_sent = False
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sequence = 0
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stream = None
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while True:
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# build packet
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if not header_sent:
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# send packet sequence 0 containing:
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# Filename Length [Modification-Date [Mode [Serial-Number]]]
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stream = open(filename, 'rb')
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stat = os.stat(filename)
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data = os.path.basename(filename).encode() + NUL + str(stat.st_size).encode()
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self.log.debug('ymodem sending : "%s" len:%d', filename, stat.st_size)
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if len(data) <= 128:
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header_size = 128
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else:
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header_size = 1024
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header = self._make_send_header(header_size, sequence)
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data = data.ljust(header_size, NUL)
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checksum = self._make_send_checksum(crc_mode, data)
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header_sent = True
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total = (stat.st_size / packet_size) + 1
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else:
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# normal data packet
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data = stream.read(packet_size)
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if not data:
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# end of stream
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self.log.debug('send: at EOF')
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break
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total_packets += 1
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header = self._make_send_header(packet_size, sequence)
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data = data.ljust(packet_size, self.pad)
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checksum = self._make_send_checksum(crc_mode, data)
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# emit packet & get ACK
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self.ser.write(header + data + checksum)
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while True:
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char = self.ser.read(1)
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if char == CRC or char == CRC2 or char == CRC3:
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if self.ser.in_waiting == 0:
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self.log.debug('re-send: block %d, pks: %d', sequence, packet_size)
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self.ser.write(header + data + checksum)
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else:
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rubbish = self.ser.read(self.ser.in_waiting-1)
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self.log.error('got NAK rubbish %r for block %d', rubbish, sequence)
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continue
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if char == ACK or char == ACK2 or char == NAK:
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success_count += 1
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if callable(callback):
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callback(total_packets, success_count, error_count, total)
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error_count = 0
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if char == NAK:
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rubbish = self.ser.read(1024)
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self.log.error('got NAK rubbish %r for block %d', rubbish, sequence)
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rubbish = self.ser.read(1024)
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self.log.error('got NAK rubbish %r for block %d', rubbish, sequence)
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rubbish = self.ser.read(1024)
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self.log.error('got NAK rubbish %r for block %d', rubbish, sequence)
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rubbish = self.ser.read(1024)
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self.log.error('got NAK rubbish %r for block %d', rubbish, sequence)
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break
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if char == ABT:
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self.log.debug('got abort')
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return False
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self.log.error('send error: expected CRC|ACK; got %r for block %d',
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char, sequence)
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error_count += 1
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if callable(callback):
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callback(total_packets, success_count, error_count, total)
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if error_count > retry:
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# excessive amounts of retransmissions requested,
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# abort transfer
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self.log.error('send error: Unexpected received %d times, '
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'aborting.', error_count)
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self.abort(timeout=timeout)
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return False
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# keep track of sequence
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sequence = (sequence + 1) % 0x100
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# emit EOT and get corresponding ACK
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while True:
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self.log.debug('sending EOT, awaiting ACK')
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# end of transmission
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self.ser.write(EOT)
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self.ser.write(EOT)
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self.ser.write(EOT)
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# An ACK should be returned
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char = self.ser.read(1)
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if char == ACK:
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break
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else:
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self.log.error('send error: expected ACK; got %r', char)
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error_count += 1
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if error_count > retry:
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self.log.warning('EOT was not ACKd, aborting transfer')
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self.abort(timeout=timeout)
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return False
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self.log.info('Transmission successful (ACK received).')
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stream.close()
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return True
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def _make_send_header(self, packet_size, sequence):
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assert packet_size in (128, 1024), packet_size
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_bytes = []
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if packet_size == 128:
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_bytes.append(ord(SOH))
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elif packet_size == 1024:
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_bytes.append(ord(STX))
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_bytes.extend([sequence, 0xff - sequence])
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return bytearray(_bytes)
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def _make_send_checksum(self, crc_mode, data):
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assert crc_mode is 1
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_bytes = []
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if crc_mode:
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crc = self.calc_crc(data)
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_bytes.extend([crc >> 8, crc & 0xff])
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return bytearray(_bytes)
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def calc_crc(self, data, crc=0):
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'''
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Calculate the Cyclic Redundancy Check for a given block of data, can
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also be used to update a CRC.
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>>> crc = modem.calc_crc('hello')
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>>> crc = modem.calc_crc('world', crc)
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>>> hex(crc)
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'0xd5e3'
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'''
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for char in bytearray(data):
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crctbl_idx = ((crc >> 8) ^ char) & 0xff
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crc = ((crc << 8) ^ self.crctable[crctbl_idx]) & 0xffff
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return crc & 0xffff
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