Lib/quopri.py

   1 #! /usr/bin/env python
   2
   3 """Conversions to/from quoted-printable transport encoding as per RFC-1521."""
   4
   5 # (Dec 1991 version).
   6
   7 ESCAPE = '='
   8 MAXLINESIZE = 76
   9 HEX = '0123456789ABCDEF'
  10
  11 def needsquoting(c, quotetabs):
  12         """Decide whether a particular character needs to be quoted.
  13
  14         The 'quotetabs' flag indicates whether tabs should be quoted."""
  15         if c == '\t':
  16                 return not quotetabs
  17         return c == ESCAPE or not(' ' <= c <= '~')
  18
  19 def quote(c):
  20         """Quote a single character."""
  21         if c == ESCAPE:
  22                 return ESCAPE * 2
  23         else:
  24                 i = ord(c)
  25                 return ESCAPE + HEX[i/16] + HEX[i%16]
  26
  27 def encode(input, output, quotetabs):
  28         """Read 'input', apply quoted-printable encoding, and write to 'output'.
  29
  30         'input' and 'output' are files with readline() and write() methods.
  31         The 'quotetabs' flag indicates whether tabs should be quoted."""
  32         while 1:
  33                 line = input.readline()
  34                 if not line: break
  35                 new = ''
  36                 last = line[-1:]
  37                 if last == '\n': line = line[:-1]
  38                 else: last = ''
  39                 prev = ''
  40                 for c in line:
  41                         if needsquoting(c, quotetabs):
  42                                 c = quote(c)
  43                         if len(new) + len(c) >= MAXLINESIZE:
  44                                 output.write(new + ESCAPE + '\n')
  45                                 new = ''
  46                         new = new + c
  47                         prev = c
  48                 if prev in (' ', '\t'):
  49                         output.write(new + ESCAPE + '\n\n')
  50                 else:
  51                         output.write(new + '\n')
  52
  53 def decode(input, output):
  54         """Read 'input', apply quoted-printable decoding, and write to 'output'.
  55
  56         'input' and 'output' are files with readline() and write() methods."""
  57         new = ''
  58         while 1:
  59                 line = input.readline()
  60                 if not line: break
  61                 i, n = 0, len(line)
  62                 if n > 0 and line[n-1] == '\n':
  63                         partial = 0; n = n-1
  64                         # Strip trailing whitespace
  65                         while n > 0 and line[n-1] in (' ', '\t'):
  66                                 n = n-1
  67                 else:
  68                         partial = 1
  69                 while i < n:
  70                         c = line[i]
  71                         if c <> ESCAPE:
  72                                 new = new + c; i = i+1
  73                         elif i+1 == n and not partial:
  74                                 partial = 1; break
  75                         elif i+1 < n and line[i+1] == ESCAPE:
  76                                 new = new + ESCAPE; i = i+2
  77                         elif i+2 < n and ishex(line[i+1]) and ishex(line[i+2]):
  78                                 new = new + chr(unhex(line[i+1:i+3])); i = i+3
  79                         else: # Bad escape sequence -- leave it in
  80                                 new = new + c; i = i+1
  81                 if not partial:
  82                         output.write(new + '\n')
  83                         new = ''
  84         if new:
  85                 output.write(new)
  86
  87 def ishex(c):
  88         """Return true if the character 'c' is a hexadecimal digit."""
  89         return '0' <= c <= '9' or 'a' <= c <= 'f' or 'A' <= c <= 'F'
  90
  91 def unhex(s):
  92         """Get the integer value of a hexadecimal number."""
  93         bits = 0
  94         for c in s:
  95                 if '0' <= c <= '9':
  96                         i = ord('0')
  97                 elif 'a' <= c <= 'f':
  98                         i = ord('a')-10
  99                 elif 'A' <= c <= 'F':
 100                         i = ord('A')-10
 101                 else:
 102                         break
 103                 bits = bits*16 + (ord(c) - i)
 104         return bits
 105
 106 def test():
 107         import sys
 108         import getopt
 109         try:
 110                 opts, args = getopt.getopt(sys.argv[1:], 'td')
 111         except getopt.error, msg:
 112                 sys.stdout = sys.stderr
 113                 print msg
 114                 print "usage: quopri [-t | -d] [file] ..."
 115                 print "-t: quote tabs"
 116                 print "-d: decode; default encode"
 117                 sys.exit(2)
 118         deco = 0
 119         tabs = 0
 120         for o, a in opts:
 121                 if o == '-t': tabs = 1
 122                 if o == '-d': deco = 1
 123         if tabs and deco:
 124                 sys.stdout = sys.stderr
 125                 print "-t and -d are mutually exclusive"
 126                 sys.exit(2)
 127         if not args: args = ['-']
 128         sts = 0
 129         for file in args:
 130                 if file == '-':
 131                         fp = sys.stdin
 132                 else:
 133                         try:
 134                                 fp = open(file)
 135                         except IOError, msg:
 136                                 sys.stderr.write("%s: can't open (%s)\n" % (file, msg))
 137                                 sts = 1
 138                                 continue
 139                 if deco:
 140                         decode(fp, sys.stdout)
 141                 else:
 142                         encode(fp, sys.stdout, tabs)
 143                 if fp is not sys.stdin:
 144                         fp.close()
 145         if sts:
 146                 sys.exit(sts)
 147
 148 if __name__ == '__main__':
 149         test()