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 __all__ = ["encode","decode"]
   8
   9 ESCAPE = '='
  10 MAXLINESIZE = 76
  11 HEX = '0123456789ABCDEF'
  12
  13 def needsquoting(c, quotetabs):
  14     """Decide whether a particular character needs to be quoted.
  15
  16     The 'quotetabs' flag indicates whether tabs should be quoted."""
  17     if c == '\t':
  18         return not quotetabs
  19     return c == ESCAPE or not(' ' <= c <= '~')
  20
  21 def quote(c):
  22     """Quote a single character."""
  23     i = ord(c)
  24     return ESCAPE + HEX[i/16] + HEX[i%16]
  25
  26 def encode(input, output, quotetabs):
  27     """Read 'input', apply quoted-printable encoding, and write to 'output'.
  28
  29     'input' and 'output' are files with readline() and write() methods.
  30     The 'quotetabs' flag indicates whether tabs should be quoted.
  31         """
  32     while 1:
  33         line = input.readline()
  34         if not line:
  35             break
  36         new = ''
  37         last = line[-1:]
  38         if last == '\n':
  39             line = line[:-1]
  40         else:
  41             last = ''
  42         prev = ''
  43         for c in line:
  44             if needsquoting(c, quotetabs):
  45                 c = quote(c)
  46             if len(new) + len(c) >= MAXLINESIZE:
  47                 output.write(new + ESCAPE + '\n')
  48                 new = ''
  49             new = new + c
  50             prev = c
  51         if prev in (' ', '\t'):
  52             output.write(new + ESCAPE + '\n\n')
  53         else:
  54             output.write(new + '\n')
  55
  56 def decode(input, output):
  57     """Read 'input', apply quoted-printable decoding, and write to 'output'.
  58
  59     'input' and 'output' are files with readline() and write() methods."""
  60     new = ''
  61     while 1:
  62         line = input.readline()
  63         if not line: break
  64         i, n = 0, len(line)
  65         if n > 0 and line[n-1] == '\n':
  66             partial = 0; n = n-1
  67             # Strip trailing whitespace
  68             while n > 0 and line[n-1] in " \t\r":
  69                 n = n-1
  70         else:
  71             partial = 1
  72         while i < n:
  73             c = line[i]
  74             if c != ESCAPE:
  75                 new = new + c; i = i+1
  76             elif i+1 == n and not partial:
  77                 partial = 1; break
  78             elif i+1 < n and line[i+1] == ESCAPE:
  79                 new = new + ESCAPE; i = i+2
  80             elif i+2 < n and ishex(line[i+1]) and ishex(line[i+2]):
  81                 new = new + chr(unhex(line[i+1:i+3])); i = i+3
  82             else: # Bad escape sequence -- leave it in
  83                 new = new + c; i = i+1
  84         if not partial:
  85             output.write(new + '\n')
  86             new = ''
  87     if new:
  88         output.write(new)
  89
  90 def ishex(c):
  91     """Return true if the character 'c' is a hexadecimal digit."""
  92     return '0' <= c <= '9' or 'a' <= c <= 'f' or 'A' <= c <= 'F'
  93
  94 def unhex(s):
  95     """Get the integer value of a hexadecimal number."""
  96     bits = 0
  97     for c in s:
  98         if '0' <= c <= '9':
  99             i = ord('0')
 100         elif 'a' <= c <= 'f':
 101             i = ord('a')-10
 102         elif 'A' <= c <= 'F':
 103             i = ord('A')-10
 104         else:
 105             break
 106         bits = bits*16 + (ord(c) - i)
 107     return bits
 108
 109 def test():
 110     import sys
 111     import getopt
 112     try:
 113         opts, args = getopt.getopt(sys.argv[1:], 'td')
 114     except getopt.error, msg:
 115         sys.stdout = sys.stderr
 116         print msg
 117         print "usage: quopri [-t | -d] [file] ..."
 118         print "-t: quote tabs"
 119         print "-d: decode; default encode"
 120         sys.exit(2)
 121     deco = 0
 122     tabs = 0
 123     for o, a in opts:
 124         if o == '-t': tabs = 1
 125         if o == '-d': deco = 1
 126     if tabs and deco:
 127         sys.stdout = sys.stderr
 128         print "-t and -d are mutually exclusive"
 129         sys.exit(2)
 130     if not args: args = ['-']
 131     sts = 0
 132     for file in args:
 133         if file == '-':
 134             fp = sys.stdin
 135         else:
 136             try:
 137                 fp = open(file)
 138             except IOError, msg:
 139                 sys.stderr.write("%s: can't open (%s)\n" % (file, msg))
 140                 sts = 1
 141                 continue
 142         if deco:
 143             decode(fp, sys.stdout)
 144         else:
 145             encode(fp, sys.stdout, tabs)
 146         if fp is not sys.stdin:
 147             fp.close()
 148     if sts:
 149         sys.exit(sts)
 150
 151 if __name__ == '__main__':
 152     test()