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Handle empty file, Remove second purge, Fix dead loop #50

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merged 3 commits into from
May 1, 2023
Merged

Handle empty file, Remove second purge, Fix dead loop #50

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6836e2b
Handles receiving empty file
rdelagato Jan 21, 2021
64f294e
Added comment to explain usecond sleep
rdelagato Jan 21, 2021
576216e
Modified test for equality
rdelagato Jan 21, 2021
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46 changes: 27 additions & 19 deletions xmodem/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -419,6 +419,7 @@ def recv(self, stream, crc_mode=1, retry=16, timeout=60, delay=1, quiet=0):
error_count = 0
char = 0
cancel = 0
empty = 0
while True:
# first try CRC mode, if this fails,
# fall back to checksum mode
Expand Down Expand Up @@ -459,6 +460,19 @@ def recv(self, stream, crc_mode=1, retry=16, timeout=60, delay=1, quiet=0):
else:
self.log.debug('cancellation at start sequence.')
cancel = 1
elif char == EOT:
if empty:
self.log.info('transmission canceled: file empty ')
self.putc(CAN)
self.putc(CAN)
while True:
if self.getc(1, timeout=1) is None:
break
time.sleep(.001) # better cpu usage
return 0
else:
self.log.info('first eot received ')
empty = 1
else:
error_count += 1

Expand Down Expand Up @@ -508,6 +522,10 @@ def recv(self, stream, crc_mode=1, retry=16, timeout=60, delay=1, quiet=0):
retry)
self.abort()
return None
time.sleep(timeout)

# Reads next char from stream
char = self.getc(1, timeout=1)

# read sequence
error_count = 0
Expand All @@ -530,8 +548,7 @@ def recv(self, stream, crc_mode=1, retry=16, timeout=60, delay=1, quiet=0):
# consume data anyway ... even though we will discard it,
# it is not the sequence we expected!
self.log.error('expected sequence %d, '
'got (seq1=%r, seq2=%r), '
'receiving next block, will NAK.',
'got (seq1=%r, seq2=%r), ',
sequence, seq1, seq2)
self.getc(packet_size + 1 + crc_mode)
else:
Expand All @@ -546,27 +563,18 @@ def recv(self, stream, crc_mode=1, retry=16, timeout=60, delay=1, quiet=0):
stream.write(data)
self.putc(ACK)
sequence = (sequence + 1) % 0x100
# get next start-of-header byte
# get possible start-of-header byte
# may be echoed ACK, NAK signal if so purge
char = self.getc(1, timeout)
if char in { ACK, NAK }:
char = self.getc(1, timeout)
continue

# something went wrong, request retransmission
self.log.warning('recv error: purge, requesting retransmission (NAK)')
while True:
# When the receiver wishes to <nak>, it should call a "PURGE"
# subroutine, to wait for the line to clear. Recall the sender
# tosses any characters in its UART buffer immediately upon
# completing sending a block, to ensure no glitches were mis-
# interpreted. The most common technique is for "PURGE" to
# call the character receive subroutine, specifying a 1-second
# timeout, and looping back to PURGE until a timeout occurs.
# The <nak> is then sent, ensuring the other end will see it.
data = self.getc(1, timeout=1)
if data is None:
break
self.putc(NAK)
# get next start-of-header byte
# get possible start-of-header byte
# may be echoed ACK, NAK signal if so purge
char = self.getc(1, timeout)
if char in { ACK, NAK }:
char = self.getc(1, timeout)
continue

def _verify_recv_checksum(self, crc_mode, data):
Expand Down