111 lines
3.9 KiB
Python
111 lines
3.9 KiB
Python
# DistUpgradeEdPatcher.py
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#
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# Copyright (c) 2011 Canonical
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#
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# Author: Michael Vogt <michael.vogt@ubuntu.com>
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#
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# This program is free software; you can redistribute it and/or
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# modify it under the terms of the GNU General Public License as
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# published by the Free Software Foundation; either version 2 of the
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# License, or (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
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# USA
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import hashlib
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import re
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class PatchError(Exception):
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""" Error during the patch process """
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pass
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def patch(orig, edpatch, result_md5sum=None):
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""" python implementation of enough "ed" to apply ed-style
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patches. Note that this patches in memory so its *not*
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suitable for big files
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"""
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# we only have two states, waiting for command or reading data
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(STATE_EXPECT_COMMAND,
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STATE_EXPECT_DATA) = range(2)
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# this is inefficient for big files
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with open(orig, encoding="UTF-8") as f:
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orig_lines = f.readlines()
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start = end = 0
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# we start in wait-for-commend state
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state = STATE_EXPECT_COMMAND
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with open(edpatch, encoding="UTF-8") as f:
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lines = f.readlines()
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for line in lines:
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if state == STATE_EXPECT_COMMAND:
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# in commands get rid of whitespace,
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line = line.strip()
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# check if we have a substitute command
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if line.startswith("s/"):
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# strip away the "s/"
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line = line[2:]
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# chop off the flags at the end
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subs, flags = line.rsplit("/", 1)
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if flags:
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raise PatchError("flags for s// not supported yet")
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# get the actual substitution regexp and replacement and
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# execute it
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regexp, sep, repl = subs.partition("/")
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new, count = re.subn(regexp, repl, orig_lines[start], count=1)
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orig_lines[start] = new
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continue
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# otherwise the last char is the command
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command = line[-1]
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# read address
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(start_str, sep, end_str) = line[:-1].partition(",")
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# ed starts with 1 while python with 0
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start = int(start_str)
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start -= 1
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# if we don't have end, set it to the next line
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if end_str == "":
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end = start + 1
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else:
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end = int(end_str)
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# interpret command
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if command == "c":
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del orig_lines[start:end]
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state = STATE_EXPECT_DATA
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start -= 1
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elif command == "a":
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# not allowed to have a range in append
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state = STATE_EXPECT_DATA
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elif command == "d":
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del orig_lines[start:end]
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else:
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raise PatchError("unknown command: '%s'" % line)
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elif state == STATE_EXPECT_DATA:
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# this is the data end marker
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if line == ".\n":
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state = STATE_EXPECT_COMMAND
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else:
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# copy line verbatim and increase position
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start += 1
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orig_lines.insert(start, line)
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# done with the patching, (optional) verify and write result
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result = "".join(orig_lines)
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if result_md5sum:
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md5 = hashlib.md5()
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md5.update(result.encode("UTF-8"))
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if md5.hexdigest() != result_md5sum:
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raise PatchError("the md5sum after patching is not correct")
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with open(orig, "w", encoding="UTF-8") as f:
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f.write(result)
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return True
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