bin/chpathtool.py

   1 #!/usr/bin/python
   2 # Copyright 2011-2012 Gentoo Foundation
   3 # Distributed under the terms of the GNU General Public License v2
   4
   5 import io
   6 import optparse
   7 import os
   8 import stat
   9 import sys
  10
  11 CONTENT_ENCODING = "utf_8"
  12 FS_ENCODING = "utf_8"
  13
  14 try:
  15         import magic
  16 except ImportError:
  17         magic = None
  18 else:
  19         try:
  20                 magic.MIME_TYPE
  21         except AttributeError:
  22                 # magic module seems to be broken
  23                 magic = None
  24
  25 class IsTextFile(object):
  26
  27         def __init__(self):
  28                 if magic is not None:
  29                         self._call = self._is_text_magic
  30                         self._m = magic.open(magic.MIME_TYPE)
  31                         self._m.load()
  32                 else:
  33                         self._call = self._is_text_encoding
  34                         self._encoding = CONTENT_ENCODING
  35
  36         def __call__(self, filename):
  37                 """
  38                 Returns True if the given file is a text file, and False otherwise.
  39                 """
  40                 return self._call(filename)
  41
  42         def _is_text_magic(self, filename):
  43                 mime_type = self._m.file(filename)
  44                 return mime_type.startswith("text/")
  45
  46         def _is_text_encoding(self, filename):
  47                 try:
  48                         for line in io.open(filename, mode='r', encoding=self._encoding):
  49                                 pass
  50                 except UnicodeDecodeError:
  51                         return False
  52                 return True
  53
  54 def chpath_inplace(filename, is_text_file, old, new):
  55         """
  56         Returns True if any modifications were made, and False otherwise.
  57         """
  58
  59         modified = False
  60         orig_stat = os.lstat(filename)
  61         try:
  62                 f = io.open(filename, buffering=0, mode='r+b')
  63         except IOError:
  64                 try:
  65                         orig_mode = stat.S_IMODE(os.lstat(filename).st_mode)
  66                 except OSError as e:
  67                         sys.stderr.write("%s: %s\n" % (e, filename))
  68                         return
  69                 temp_mode = 0o200 | orig_mode
  70                 os.chmod(filename, temp_mode)
  71                 try:
  72                         f = io.open(filename, buffering=0, mode='r+b')
  73                 finally:
  74                         os.chmod(filename, orig_mode)
  75
  76         len_old = len(old)
  77         len_new = len(new)
  78         matched_byte_count = 0
  79         while True:
  80                 in_byte = f.read(1)
  81
  82                 if not in_byte:
  83                         break
  84
  85                 if in_byte == old[matched_byte_count]:
  86                         matched_byte_count += 1
  87                         if matched_byte_count == len_old:
  88                                 modified = True
  89                                 matched_byte_count = 0
  90                                 end_position = f.tell()
  91                                 start_position = end_position - len_old
  92                                 if not is_text_file:
  93                                         # search backwards for leading slashes written by
  94                                         # a previous invocation of this tool
  95                                         num_to_write = len_old
  96                                         f.seek(start_position - 1)
  97                                         while True:
  98                                                 if f.read(1) != b'/':
  99                                                         break
 100                                                 num_to_write += 1
 101                                                 f.seek(f.tell() - 2)
 102
 103                                         # pad with as many leading slashes as necessary
 104                                         while num_to_write > len_new:
 105                                                 f.write(b'/')
 106                                                 num_to_write -= 1
 107                                         f.write(new)
 108                                 else:
 109                                         remainder = f.read()
 110                                         f.seek(start_position)
 111                                         f.write(new)
 112                                         if remainder:
 113                                                 f.write(remainder)
 114                                                 f.truncate()
 115                                                 f.seek(start_position + len_new)
 116                 elif matched_byte_count > 0:
 117                         # back up an try to start a new match after
 118                         # the first byte of the previous partial match
 119                         f.seek(f.tell() - matched_byte_count)
 120                         matched_byte_count = 0
 121
 122         f.close()
 123         if modified:
 124                 if sys.hexversion >= 0x3030000:
 125                         orig_mtime = orig_stat.st_mtime_ns
 126                         os.utime(filename, ns=(orig_mtime, orig_mtime))
 127                 else:
 128                         orig_mtime = orig_stat[stat.ST_MTIME]
 129                         os.utime(filename, (orig_mtime, orig_mtime))
 130         return modified
 131
 132 def chpath_inplace_symlink(filename, st, old, new):
 133         target = os.readlink(filename)
 134         if target.startswith(old):
 135                 new_target = new + target[len(old):]
 136                 os.unlink(filename)
 137                 os.symlink(new_target, filename)
 138                 os.lchown(filename, st.st_uid, st.st_gid)
 139
 140 def main(argv):
 141
 142         usage = "%s [options] <location> <old> <new>" % (os.path.basename(argv[0],))
 143         parser = optparse.OptionParser(usage=usage)
 144         options, args = parser.parse_args(argv[1:])
 145
 146         if len(args) != 3:
 147                 parser.error("3 args required, got %s" % (len(args),))
 148
 149         location, old, new = args
 150
 151         is_text_file = IsTextFile()
 152
 153         if not isinstance(location, bytes):
 154                 location = location.encode(FS_ENCODING)
 155         if not isinstance(old, bytes):
 156                 old = old.encode(FS_ENCODING)
 157         if not isinstance(new, bytes):
 158                 new = new.encode(FS_ENCODING)
 159
 160         st = os.lstat(location)
 161
 162         if stat.S_ISDIR(st.st_mode):
 163                 for parent, dirs, files in os.walk(location):
 164                         for filename in files:
 165                                 filename = os.path.join(parent, filename)
 166                                 try:
 167                                         st = os.lstat(filename)
 168                                 except OSError:
 169                                         pass
 170                                 else:
 171                                         if stat.S_ISREG(st.st_mode):
 172                                                 chpath_inplace(filename,
 173                                                         is_text_file(filename), old, new)
 174                                         elif stat.S_ISLNK(st.st_mode):
 175                                                 chpath_inplace_symlink(filename, st, old, new)
 176
 177         elif stat.S_ISREG(st.st_mode):
 178                 chpath_inplace(location,
 179                         is_text_file(location), old, new)
 180         elif stat.S_ISLNK(st.st_mode):
 181                 chpath_inplace_symlink(location, st, old, new)
 182
 183         return os.EX_OK
 184
 185 if __name__ == "__main__":
 186         sys.exit(main(sys.argv))