591 lines
20 KiB
Python
591 lines
20 KiB
Python
'''
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===============================
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XMODEM file transfer protocol
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===============================
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.. $Id$
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This is a literal implementation of XMODEM.TXT_, XMODEM1K.TXT_ and
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XMODMCRC.TXT_, support for YMODEM and ZMODEM is pending. YMODEM should
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be fairly easy to implement as it is a hack on top of the XMODEM
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protocol using sequence bytes ``0x00`` for sending file names (and some
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meta data).
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.. _XMODEM.TXT: doc/XMODEM.TXT
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.. _XMODEM1K.TXT: doc/XMODEM1K.TXT
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.. _XMODMCRC.TXT: doc/XMODMCRC.TXT
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Data flow example including error recovery
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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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It includes the two most common line hits - a garbaged block,
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and an ``ACK`` reply getting garbaged. ``CRC`` or ``CSUM`` represents
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the checksum bytes.
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XMODEM 128 byte blocks
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----------------------
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::
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SENDER RECEIVER
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<-- NAK
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SOH 01 FE Data[128] CSUM -->
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<-- ACK
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SOH 02 FD Data[128] CSUM -->
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<-- ACK
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SOH 03 FC Data[128] CSUM -->
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<-- ACK
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SOH 04 FB Data[128] CSUM -->
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<-- ACK
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SOH 05 FA Data[100] CPMEOF[28] CSUM -->
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<-- ACK
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EOT -->
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<-- ACK
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XMODEM-1k blocks, CRC mode
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--------------------------
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::
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SENDER RECEIVER
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<-- C
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STX 01 FE Data[1024] CRC CRC -->
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<-- ACK
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STX 02 FD Data[1024] CRC CRC -->
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<-- ACK
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STX 03 FC Data[1000] CPMEOF[24] CRC CRC -->
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<-- ACK
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EOT -->
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<-- ACK
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Mixed 1024 and 128 byte Blocks
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------------------------------
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::
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SENDER RECEIVER
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<-- C
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STX 01 FE Data[1024] CRC CRC -->
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<-- ACK
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STX 02 FD Data[1024] CRC CRC -->
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<-- ACK
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SOH 03 FC Data[128] CRC CRC -->
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<-- ACK
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SOH 04 FB Data[100] CPMEOF[28] CRC CRC -->
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<-- ACK
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EOT -->
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<-- ACK
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YMODEM Batch Transmission Session (1 file)
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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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<-- C
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SOH 01 FE Data[128] CRC CRC -->
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<-- ACK
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SOH 02 FC Data[128] CRC CRC -->
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<-- ACK
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SOH 03 FB Data[100] CPMEOF[28] CRC CRC -->
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<-- ACK
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EOT -->
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<-- NAK
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EOT -->
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<-- ACK
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<-- C
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SOH 00 FF NUL[128] CRC CRC -->
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<-- ACK
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'''
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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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__license__ = 'MIT'
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__version__ = '0.3.2'
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import logging
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import time
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import sys
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from functools import partial
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import collections
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# Loggerr
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log = logging.getLogger('xmodem')
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# Protocol bytes
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SOH = bytes([0x01])
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STX = bytes([0x02])
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EOT = bytes([0x04])
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ACK = bytes([0x06])
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DLE = bytes([0x10])
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NAK = bytes([0x15])
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CAN = bytes([0x18])
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CRC = bytes([0x43]) # C
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class XMODEM(object):
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'''
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XMODEM Protocol handler, expects an object to read from and an object to
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write to.
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>>> def getc(size, timeout=1):
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... return data or None
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...
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>>> def putc(data, timeout=1):
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... return size or None
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...
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>>> modem = XMODEM(getc, putc)
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:param getc: Function to retreive bytes from a stream
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:type getc: callable
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:param putc: Function to transmit bytes to a stream
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:type putc: callable
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:param mode: XMODEM protocol mode
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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, getc, putc, mode='xmodem', pad=b'\x1a'):
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self.getc = getc
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self.putc = putc
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self.mode = mode
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self.pad = pad
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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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'''
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for counter in range(0, count):
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self.putc(CAN, timeout)
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def send(self, stream, retry=32, timeout=360, quiet=0, callback=None):
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'''
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Send a stream via the XMODEM protocol.
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>>> stream = file('/etc/issue', 'rb')
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>>> print modem.send(stream)
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True
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Returns ``True`` upon succesful 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 0, it prints info to stderr. If 1, it does not print any info.
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:type quiet: int
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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 xmodem
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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)
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:type callback: callable
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'''
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# initialize protocol
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try:
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packet_size = dict(
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xmodem = 128,
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xmodem1k = 1024,
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)[self.mode]
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except AttributeError:
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raise ValueError("An invalid mode was supplied")
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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.getc(1)
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if char:
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if char == NAK:
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crc_mode = 0
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break
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elif char == CRC:
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crc_mode = 1
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break
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elif char == CAN:
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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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return False
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else:
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cancel = 1
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else:
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log.error('send ERROR expected NAK/CRC, got %s' % \
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(ord(char),))
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error_count += 1
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if error_count >= 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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sequence = 1
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while True:
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data = stream.read(packet_size)
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if not data:
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log.info('sending EOT')
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# end of stream
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break
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total_packets += 1
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data = data.ljust(packet_size, self.pad)
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if crc_mode:
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crc = self.calc_crc(data)
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else:
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crc = self.calc_checksum(data)
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# emit packet
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while True:
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if packet_size == 128:
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self.putc(SOH)
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else: # packet_size == 1024
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self.putc(STX)
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self.putc(bytes([sequence]))
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self.putc(bytes([0xff - sequence]))
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self.putc(data)
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if crc_mode:
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self.putc(bytes([crc >> 8]))
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self.putc(bytes([crc & 0xff]))
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else:
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self.putc(bytes([crc]))
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char = self.getc(1, timeout)
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if char == ACK:
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success_count += 1
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if isinstance(callback, collections.Callable):
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callback(total_packets, success_count, error_count)
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break
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if char == NAK:
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error_count += 1
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if isinstance(callback, collections.Callable):
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callback(total_packets, success_count, error_count)
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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.abort(timeout=timeout)
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log.warning('excessive NAKs, transfer aborted')
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return False
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# return to loop and resend
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continue
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else:
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log.error('Not ACK, Not NAK')
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error_count += 1
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if isinstance(callback, collections.Callable):
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callback(total_packets, success_count, error_count)
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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.abort(timeout=timeout)
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log.warning('excessive protocol errors, transfer aborted')
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return False
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# return to loop and resend
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continue
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# protocol error
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self.abort(timeout=timeout)
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log.error('protocol error')
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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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while True:
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# end of transmission
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self.putc(EOT)
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#An ACK should be returned
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char = self.getc(1, timeout)
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if char == ACK:
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break
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else:
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error_count += 1
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if error_count >= retry:
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self.abort(timeout=timeout)
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log.warning('EOT was not ACKd, transfer aborted')
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return False
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return True
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def recv(self, stream, crc_mode=1, retry=16, timeout=60, delay=1, quiet=0):
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'''
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Receive a stream via the XMODEM protocol.
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>>> stream = file('/etc/issue', 'wb')
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>>> print modem.recv(stream)
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2342
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Returns the number of bytes received on success or ``None`` in case of
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failure.
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'''
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# initiate protocol
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error_count = 0
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char = 0
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cancel = 0
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while True:
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# first try CRC mode, if this fails,
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# fall back to checksum mode
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if error_count >= retry:
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self.abort(timeout=timeout)
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return None
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elif crc_mode and error_count < (retry / 2):
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if not self.putc(CRC):
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time.sleep(delay)
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error_count += 1
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else:
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crc_mode = 0
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if not self.putc(NAK):
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time.sleep(delay)
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error_count += 1
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char = self.getc(1, timeout)
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if not char:
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error_count += 1
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continue
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elif char == SOH:
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#crc_mode = 0
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break
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elif char == STX:
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break
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elif char == CAN:
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if cancel:
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return None
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else:
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cancel = 1
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else:
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error_count += 1
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# read data
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error_count = 0
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income_size = 0
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packet_size = 128
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sequence = 1
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cancel = 0
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while True:
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while True:
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if char == SOH:
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packet_size = 128
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break
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elif char == STX:
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packet_size = 1024
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break
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elif char == EOT:
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# We received an EOT, so send an ACK and return the received
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# data length
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self.putc(ACK)
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return income_size
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elif char == CAN:
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# cancel at two consecutive cancels
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if cancel:
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return None
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else:
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cancel = 1
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else:
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if not quiet:
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print('recv ERROR expected SOH/EOT, got', ord(char), file=sys.stderr)
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error_count += 1
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if error_count >= retry:
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self.abort()
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return None
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# read sequence
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error_count = 0
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cancel = 0
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seq1 = ord(self.getc(1))
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seq2 = 0xff - ord(self.getc(1))
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if seq1 == sequence and seq2 == sequence:
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# sequence is ok, read packet
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# packet_size + checksum
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data = self.getc(packet_size + 1 + crc_mode, timeout)
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if crc_mode:
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csum = (ord(data[-2]) << 8) + ord(data[-1])
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data = data[:-2]
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log.debug('CRC (%04x <> %04x)' % \
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(csum, self.calc_crc(data)))
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valid = csum == self.calc_crc(data)
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else:
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csum = data[-1]
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data = data[:-1]
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log.debug('checksum (checksum(%02x <> %02x)' % \
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(ord(csum), self.calc_checksum(data)))
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valid = ord(csum) == self.calc_checksum(data)
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# valid data, append chunk
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if valid:
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income_size += len(data)
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stream.write(data)
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self.putc(ACK)
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sequence = (sequence + 1) % 0x100
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char = self.getc(1, timeout)
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continue
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else:
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# consume data
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self.getc(packet_size + 1 + crc_mode)
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self.debug('expecting sequence %d, got %d/%d' % \
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(sequence, seq1, seq2))
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# something went wrong, request retransmission
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self.putc(NAK)
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def calc_checksum(self, data, checksum=0):
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'''
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Calculate the checksum for a given block of data, can also be used to
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update a checksum.
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>>> csum = modem.calc_checksum('hello')
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>>> csum = modem.calc_checksum('world', csum)
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>>> hex(csum)
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'0x3c'
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'''
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return (sum(map(ord, data)) + checksum) % 256
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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
|
|
also be used to update a CRC.
|
|
|
|
>>> 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 data:
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crc = (crc << 8) ^ self.crctable[((crc >> 8) ^ int(char)) & 0xff]
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|
return crc & 0xffff
|
|
|
|
|
|
XMODEM1k = partial(XMODEM, mode='xmodem1k')
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|
|
|
|
|
def run():
|
|
import optparse
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|
import subprocess
|
|
|
|
parser = optparse.OptionParser(usage='%prog [<options>] <send|recv> filename filename')
|
|
parser.add_option('-m', '--mode', default='xmodem',
|
|
help='XMODEM mode (xmodem, xmodem1k)')
|
|
|
|
options, args = parser.parse_args()
|
|
if len(args) != 3:
|
|
parser.error('invalid arguments')
|
|
return 1
|
|
|
|
elif args[0] not in ('send', 'recv'):
|
|
parser.error('invalid mode')
|
|
return 1
|
|
|
|
def _func(so, si):
|
|
import select
|
|
import subprocess
|
|
|
|
print('si', si)
|
|
print('so', so)
|
|
|
|
def getc(size, timeout=3):
|
|
w,t,f = select.select([so], [], [], timeout)
|
|
if w:
|
|
data = so.read(size)
|
|
else:
|
|
data = None
|
|
|
|
print('getc(', repr(data), ')')
|
|
return data
|
|
|
|
def putc(data, timeout=3):
|
|
w,t,f = select.select([], [si], [], timeout)
|
|
if t:
|
|
si.write(data)
|
|
si.flush()
|
|
size = len(data)
|
|
else:
|
|
size = None
|
|
|
|
print('putc(', repr(data), repr(size), ')')
|
|
return size
|
|
|
|
return getc, putc
|
|
|
|
def _pipe(*command):
|
|
pipe = subprocess.Popen(command,
|
|
stdout=subprocess.PIPE, stdin=subprocess.PIPE)
|
|
return pipe.stdout, pipe.stdin
|
|
|
|
if args[0] == 'recv':
|
|
import io
|
|
getc, putc = _func(*_pipe('sz', '--xmodem', args[2]))
|
|
stream = open(args[1], 'wb')
|
|
xmodem = XMODEM(getc, putc, mode=options.mode)
|
|
status = xmodem.recv(stream, retry=8)
|
|
stream.close()
|
|
|
|
elif args[0] == 'send':
|
|
getc, putc = _func(*_pipe('rz', '--xmodem', args[2]))
|
|
stream = open(args[1], 'rb')
|
|
xmodem = XMODEM(getc, putc, mode=options.mode)
|
|
status = xmodem.send(stream, retry=8)
|
|
stream.close()
|
|
|
|
if __name__ == '__main__':
|
|
sys.exit(run())
|