bin/chpathtool.py

   1 #!/usr/bin/python
   2 # Copyright 2011-2013 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                 if isinstance(mime_type, bytes):
  45                         mime_type = mime_type.decode('ascii', 'replace')
  46                 return mime_type.startswith("text/")
  47
  48         def _is_text_encoding(self, filename):
  49                 try:
  50                         for line in io.open(filename, mode='r', encoding=self._encoding):
  51                                 pass
  52                 except UnicodeDecodeError:
  53                         return False
  54                 return True
  55
  56 def chpath_inplace(filename, is_text_file, old, new):
  57         """
  58         Returns True if any modifications were made, and False otherwise.
  59         """
  60
  61         modified = False
  62         orig_stat = os.lstat(filename)
  63         try:
  64                 f = io.open(filename, buffering=0, mode='r+b')
  65         except IOError:
  66                 try:
  67                         orig_mode = stat.S_IMODE(os.lstat(filename).st_mode)
  68                 except OSError as e:
  69                         sys.stderr.write("%s: %s\n" % (e, filename))
  70                         return
  71                 temp_mode = 0o200 | orig_mode
  72                 os.chmod(filename, temp_mode)
  73                 try:
  74                         f = io.open(filename, buffering=0, mode='r+b')
  75                 finally:
  76                         os.chmod(filename, orig_mode)
  77
  78         len_old = len(old)
  79         len_new = len(new)
  80         matched_byte_count = 0
  81         while True:
  82                 in_byte = f.read(1)
  83
  84                 if not in_byte:
  85                         break
  86
  87                 if in_byte == old[matched_byte_count]:
  88                         matched_byte_count += 1
  89                         if matched_byte_count == len_old:
  90                                 modified = True
  91                                 matched_byte_count = 0
  92                                 end_position = f.tell()
  93                                 start_position = end_position - len_old
  94                                 if not is_text_file:
  95                                         # search backwards for leading slashes written by
  96                                         # a previous invocation of this tool
  97                                         num_to_write = len_old
  98                                         f.seek(start_position - 1)
  99                                         while True:
 100                                                 if f.read(1) != b'/':
 101                                                         break
 102                                                 num_to_write += 1
 103                                                 f.seek(f.tell() - 2)
 104
 105                                         # pad with as many leading slashes as necessary
 106                                         while num_to_write > len_new:
 107                                                 f.write(b'/')
 108                                                 num_to_write -= 1
 109                                         f.write(new)
 110                                 else:
 111                                         remainder = f.read()
 112                                         f.seek(start_position)
 113                                         f.write(new)
 114                                         if remainder:
 115                                                 f.write(remainder)
 116                                                 f.truncate()
 117                                                 f.seek(start_position + len_new)
 118                 elif matched_byte_count > 0:
 119                         # back up an try to start a new match after
 120                         # the first byte of the previous partial match
 121                         f.seek(f.tell() - matched_byte_count)
 122                         matched_byte_count = 0
 123
 124         f.close()
 125         if modified:
 126                 if sys.hexversion >= 0x3030000:
 127                         orig_mtime = orig_stat.st_mtime_ns
 128                         os.utime(filename, ns=(orig_mtime, orig_mtime))
 129                 else:
 130                         orig_mtime = orig_stat[stat.ST_MTIME]
 131                         os.utime(filename, (orig_mtime, orig_mtime))
 132         return modified
 133
 134 def chpath_inplace_symlink(filename, st, old, new):
 135         target = os.readlink(filename)
 136         if target.startswith(old):
 137                 new_target = new + target[len(old):]
 138                 os.unlink(filename)
 139                 os.symlink(new_target, filename)
 140                 os.lchown(filename, st.st_uid, st.st_gid)
 141
 142 def main(argv):
 143
 144         usage = "%s [options] <location> <old> <new>" % (os.path.basename(argv[0],))
 145         parser = optparse.OptionParser(usage=usage)
 146         options, args = parser.parse_args(argv[1:])
 147
 148         if len(args) != 3:
 149                 parser.error("3 args required, got %s" % (len(args),))
 150
 151         location, old, new = args
 152
 153         is_text_file = IsTextFile()
 154
 155         if not isinstance(location, bytes):
 156                 location = location.encode(FS_ENCODING)
 157         if not isinstance(old, bytes):
 158                 old = old.encode(FS_ENCODING)
 159         if not isinstance(new, bytes):
 160                 new = new.encode(FS_ENCODING)
 161
 162         st = os.lstat(location)
 163
 164         if stat.S_ISDIR(st.st_mode):
 165                 for parent, dirs, files in os.walk(location):
 166                         for filename in files:
 167                                 filename = os.path.join(parent, filename)
 168                                 try:
 169                                         st = os.lstat(filename)
 170                                 except OSError:
 171                                         pass
 172                                 else:
 173                                         if stat.S_ISREG(st.st_mode):
 174                                                 chpath_inplace(filename,
 175                                                         is_text_file(filename), old, new)
 176                                         elif stat.S_ISLNK(st.st_mode):
 177                                                 chpath_inplace_symlink(filename, st, old, new)
 178
 179         elif stat.S_ISREG(st.st_mode):
 180                 chpath_inplace(location,
 181                         is_text_file(location), old, new)
 182         elif stat.S_ISLNK(st.st_mode):
 183                 chpath_inplace_symlink(location, st, old, new)
 184
 185         return os.EX_OK
 186
 187 if __name__ == "__main__":
 188         sys.exit(main(sys.argv))