File Content: DistUpgradePatcher.py # DistUpgradeEdPatcher.py # # Copyright (c) 2011 Canonical # # Author: Michael Vogt <michael.vogt@ubuntu.com> # # 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 2 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. # # You should have received a copy of the GNU General Public License # along with this program; if not, write to the Free Software # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 # USA import hashlib import re class PatchError(Exception): """ Error during the patch process """ pass def patch(orig, edpatch, result_md5sum=None): """ python implementation of enough "ed" to apply ed-style patches. Note that this patches in memory so its *not* suitable for big files """ # we only have two states, waiting for command or reading data (STATE_EXPECT_COMMAND, STATE_EXPECT_DATA) = range(2) # this is inefficient for big files with open(orig, encoding="UTF-8") as f: orig_lines = f.readlines() start = end = 0 # we start in wait-for-commend state state = STATE_EXPECT_COMMAND with open(edpatch, encoding="UTF-8") as f: lines = f.readlines() for line in lines: if state == STATE_EXPECT_COMMAND: # in commands get rid of whitespace, line = line.strip() # check if we have a substitute command if line.startswith("s/"): # strip away the "s/" line = line[2:] # chop off the flags at the end subs, flags = line.rsplit("/", 1) if flags: raise PatchError("flags for s// not supported yet") # get the actual substitution regexp and replacement and # execute it regexp, sep, repl = subs.partition("/") new, count = re.subn(regexp, repl, orig_lines[start], count=1) orig_lines[start] = new continue # otherwise the last char is the command command = line[-1] # read address (start_str, sep, end_str) = line[:-1].partition(",") # ed starts with 1 while python with 0 start = int(start_str) start -= 1 # if we don't have end, set it to the next line if end_str == "": end = start + 1 else: end = int(end_str) # interpret command if command == "c": del orig_lines[start:end] state = STATE_EXPECT_DATA start -= 1 elif command == "a": # not allowed to have a range in append state = STATE_EXPECT_DATA elif command == "d": del orig_lines[start:end] else: raise PatchError("unknown command: '%s'" % line) elif state == STATE_EXPECT_DATA: # this is the data end marker if line == ".\n": state = STATE_EXPECT_COMMAND else: # copy line verbatim and increase position start += 1 orig_lines.insert(start, line) # done with the patching, (optional) verify and write result result = "".join(orig_lines) if result_md5sum: md5 = hashlib.md5() md5.update(result.encode("UTF-8")) if md5.hexdigest() != result_md5sum: raise PatchError("the md5sum after patching is not correct") with open(orig, "w", encoding="UTF-8") as f: f.write(result) return True Submit