#!/usr/bin/python2
#
# Python functions to read, split and apply patches.
#
# Copyright (C) 2014 Sebastian Lackner
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library 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
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
#
import collections
import difflib
import hashlib
import itertools
import os
import re
import subprocess
import tempfile
class PatchParserError(RuntimeError):
"""Unable to parse patch file - either an unimplemented feature, or corrupted patch."""
pass
class PatchApplyError(RuntimeError):
"""Failed to apply/merge patch."""
pass
class PatchObject(object):
def __init__(self, filename):
self.extracted_patch = None
self.unique_hash = None
self.filename = filename
self.offset_begin = None
self.offset_end = None
self.isbinary = False
self.oldname = None
self.newname = None
self.modified_file = None
self.oldsha1 = None
self.newsha1 = None
self.newmode = None
def is_binary(self):
return self.isbinary
def read_chunks(self):
"""Iterates over arbitrary sized chunks of this patch."""
assert self.offset_end >= self.offset_begin
with open(self.filename) as fp:
fp.seek(self.offset_begin)
i = self.offset_end - self.offset_begin
while i > 0:
buf = fp.read(4096 if i > 4096 else i)
if buf == "": raise IOError("Unable to extract patch.")
yield buf
i -= len(buf)
def extract(self):
"""Create a temporary file containing the extracted patch."""
if not self.extracted_patch:
self.extracted_patch = tempfile.NamedTemporaryFile()
for chunk in self.read_chunks():
self.extracted_patch.write(chunk)
self.extracted_patch.flush()
return self.extracted_patch
def hash(self):
"""Hash the content of the patch."""
if not self.unique_hash:
m = hashlib.sha256()
for chunk in self.read_chunks():
m.update(chunk)
self.unique_hash = m.digest()
return self.unique_hash
def read_patch(filename):
"""Iterates over all patches contained in a file, and returns PatchObject objects."""
class _FileReader(object):
def __init__(self, filename):
self.filename = filename
self.fp = open(self.filename)
self.peeked = None
def close(self):
self.fp.close()
def __enter__(self):
return self
def __exit__(self, type, value, traceback):
self.close()
def seek(self, pos):
"""Change the file cursor position."""
self.fp.seek(pos)
self.peeked = None
def tell(self):
"""Return the current file cursor position."""
if self.peeked is None:
return self.fp.tell()
return self.peeked[0]
def peek(self):
"""Read one line without changing the file cursor."""
if self.peeked is None:
pos = self.fp.tell()
tmp = self.fp.readline()
if len(tmp) == 0: return None
self.peeked = (pos, tmp)
return self.peeked[1]
def read(self):
"""Read one line from the file, and move the file cursor to the next line."""
if self.peeked is None:
tmp = self.fp.readline()
if len(tmp) == 0: return None
return tmp
tmp, self.peeked = self.peeked, None
return tmp[1]
def _read_single_patch(fp, oldname=None, newname=None):
"""Internal function to read a single patch from a file."""
patch = PatchObject(fp.filename)
patch.offset_begin = fp.tell()
patch.oldname = oldname
patch.newname = newname
# Skip over initial diff --git header
line = fp.peek()
if line.startswith("diff --git "):
assert fp.read() == line
# Read header
while True:
line = fp.peek()
if line is None:
break
elif line.startswith("--- "):
patch.oldname = line[4:].strip()
elif line.startswith("+++ "):
patch.newname = line[4:].strip()
elif line.startswith("old mode") or line.startswith("deleted file mode"):
pass # ignore
elif line.startswith("new mode "):
patch.newmode = line[9:].strip()
elif line.startswith("new file mode "):
patch.newmode = line[14:].strip()
elif line.startswith("new mode") or line.startswith("new file mode"):
raise PatchParserError("Unable to parse header line '%s'." % line)
elif line.startswith("copy from") or line.startswith("copy to"):
raise NotImplementedError("Patch copy header not implemented yet.")
elif line.startswith("rename "):
raise NotImplementedError("Patch rename header not implemented yet.")
elif line.startswith("similarity index") or line.startswith("dissimilarity index"):
pass # ignore
elif line.startswith("index "):
r = re.match("^index ([a-fA-F0-9]*)\.\.([a-fA-F0-9]*)", line)
if not r: raise PatchParserError("Unable to parse index header line '%s'." % line)
patch.oldsha1, patch.newsha1 = r.group(1), r.group(2)
else:
break
assert fp.read() == line
if patch.oldname is None or patch.newname is None:
raise PatchParserError("Missing old or new name.")
elif patch.oldname == "/dev/null" and patch.newname == "/dev/null":
raise PatchParserError("Old and new name is /dev/null?")
if patch.oldname.startswith("a/"):
patch.oldname = patch.oldname[2:]
elif patch.oldname != "/dev/null":
raise PatchParserError("Old name in patch doesn't start with a/.")
if patch.newname.startswith("b/"):
patch.newname = patch.newname[2:]
elif patch.newname != "/dev/null":
raise PatchParserError("New name in patch doesn't start with b/.")
if patch.newname != "/dev/null":
patch.modified_file = patch.newname
else:
patch.modified_file = patch.oldname
# Decide between binary and textual patch
if line is None or line.startswith("diff --git ") or line.startswith("--- "):
if oldname != newname:
raise PatchParserError("Stripped old- and new name doesn't match.")
elif line.startswith("@@ -"):
while True:
line = fp.peek()
if line is None or not line.startswith("@@ -"):
break
r = re.match("^@@ -(([0-9]+),)?([0-9]+) \+(([0-9]+),)?([0-9]+) @@", line)
if not r: raise PatchParserError("Unable to parse hunk header '%s'." % line)
srcpos = max(int(r.group(2)) - 1, 0) if r.group(2) else 0
dstpos = max(int(r.group(5)) - 1, 0) if r.group(5) else 0
srclines, dstlines = int(r.group(3)), int(r.group(6))
if srclines <= 0 and dstlines <= 0:
raise PatchParserError("Empty hunk doesn't make sense.")
assert fp.read() == line
while srclines > 0 or dstlines > 0:
line = fp.read()
if line is None:
raise PatchParserError("Truncated patch.")
elif line.startswith(" "):
if srclines == 0 or dstlines == 0:
raise PatchParserError("Corrupted patch.")
srclines -= 1
dstlines -= 1
elif line.startswith("-"):
if srclines == 0:
raise PatchParserError("Corrupted patch.")
srclines -= 1
elif line.startswith("+"):
if dstlines == 0:
raise PatchParserError("Corrupted patch.")
dstlines -= 1
elif line.startswith("\\ "):
pass # ignore
else:
raise PatchParserError("Unexpected line in hunk.")
while True:
line = fp.peek()
if line is None or not line.startswith("\\ "): break
assert fp.read() == line
elif line.rstrip() == "GIT binary patch":
if patch.oldsha1 is None or patch.newsha1 is None:
raise PatchParserError("Missing index header, sha1 sums required for binary patch.")
elif patch.oldname != patch.newname:
raise PatchParserError("Stripped old- and new name doesn't match for binary patch.")
assert fp.read() == line
line = fp.read()
if line is None: raise PatchParserError("Unexpected end of file.")
r = re.match("^(literal|delta) ([0-9]+)", line)
if not r: raise NotImplementedError("Only literal/delta patches are supported.")
patch.isbinary = True
# Skip over patch data
while True:
line = fp.read()
if line is None or line.strip() == "":
break
else:
raise PatchParserError("Unknown patch format.")
patch.offset_end = fp.tell()
return patch
with _FileReader(filename) as fp:
while True:
line = fp.peek()
if line is None:
break
elif line.startswith("diff --git "):
tmp = line.strip().split(" ")
if len(tmp) != 4: raise PatchParserError("Unable to parse git diff header line '%s'." % line)
yield _read_single_patch(fp, tmp[2].strip(), tmp[3].strip())
elif line.startswith("--- "):
yield _read_single_patch(fp)
elif line.startswith("@@ -") or line.startswith("+++ "):
raise PatchParserError("Patch didn't start with a git or diff header.")
else:
assert fp.read() == line
def apply_patch(content, patches, reverse=False, fuzz=2):
"""Apply a patch with optional fuzz - uses the commandline 'patch' utility."""
if not isinstance(patches, collections.Sequence):
patches = [patches]
contentfile = tempfile.NamedTemporaryFile(delete=False)
try:
contentfile.write(content)
contentfile.close()
for patch in patches:
patchfile = patch.extract()
cmdline = ["patch", "--force", "--silent", "-r", "-"]
if reverse: cmdline.append("--reverse")
if fuzz != 2: cmdline.append("--fuzz=%d" % fuzz)
cmdline += [contentfile.name, patchfile.name]
with open(os.devnull, 'w') as devnull:
exitcode = subprocess.call(cmdline, stdout=devnull, stderr=devnull)
if exitcode != 0:
raise PatchApplyError("Failed to apply patch (exitcode %d)." % exitcode)
with open(contentfile.name) as fp:
content = fp.read()
finally:
os.unlink(contentfile.name)
return content