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", "encodestring", "decodestring"]
   8
   9 ESCAPE = '='
  10 MAXLINESIZE = 76
  11 HEX = '0123456789ABCDEF'
  12 EMPTYSTRING = ''
  13
  14
  15
  16 def needsquoting(c, quotetabs):
  17     """Decide whether a particular character needs to be quoted.
  18
  19     The 'quotetabs' flag indicates whether embedded tabs and spaces should be
  20     quoted.  Note that line-ending tabs and spaces are always encoded, as per
  21     RFC 1521.
  22     """
  23     if c in ' \t':
  24         return quotetabs
  25     return c == ESCAPE or not (' ' <= c <= '~')
  26
  27 def quote(c):
  28     """Quote a single character."""
  29     i = ord(c)
  30     return ESCAPE + HEX[i/16] + HEX[i%16]
  31
  32
  33
  34 def encode(input, output, quotetabs):
  35     """Read 'input', apply quoted-printable encoding, and write to 'output'.
  36
  37     'input' and 'output' are files with readline() and write() methods.
  38     The 'quotetabs' flag indicates whether embedded tabs and spaces should be
  39     quoted.  Note that line-ending tabs and spaces are always encoded, as per
  40     RFC 1521.
  41     """
  42     def write(s, output=output, lineEnd='\n'):
  43         # RFC 1521 requires that the line ending in a space or tab must have
  44         # that trailing character encoded.
  45         if s and s[-1:] in ' \t':
  46             output.write(s[:-1] + quote(s[-1]) + lineEnd)
  47         else:
  48             output.write(s + lineEnd)
  49
  50     prevline = None
  51     while 1:
  52         line = input.readline()
  53         if not line:
  54             break
  55         outline = []
  56         # Strip off any readline induced trailing newline
  57         stripped = ''
  58         if line[-1:] == '\n':
  59             line = line[:-1]
  60             stripped = '\n'
  61         # Calculate the un-length-limited encoded line
  62         for c in line:
  63             if needsquoting(c, quotetabs):
  64                 c = quote(c)
  65             outline.append(c)
  66         # First, write out the previous line
  67         if prevline is not None:
  68             write(prevline)
  69         # Now see if we need any soft line breaks because of RFC-imposed
  70         # length limitations.  Then do the thisline->prevline dance.
  71         thisline = EMPTYSTRING.join(outline)
  72         while len(thisline) > MAXLINESIZE:
  73             # Don't forget to include the soft line break `=' sign in the
  74             # length calculation!
  75             write(thisline[:MAXLINESIZE-1], lineEnd='=\n')
  76             thisline = thisline[MAXLINESIZE-1:]
  77         # Write out the current line
  78         prevline = thisline
  79     # Write out the last line, without a trailing newline
  80     if prevline is not None:
  81         write(prevline, lineEnd=stripped)
  82
  83 def encodestring(s, quotetabs=0):
  84     from cStringIO import StringIO
  85     infp = StringIO(s)
  86     outfp = StringIO()
  87     encode(infp, outfp, quotetabs)
  88     return outfp.getvalue()
  89
  90
  91
  92 def decode(input, output):
  93     """Read 'input', apply quoted-printable decoding, and write to 'output'.
  94
  95     'input' and 'output' are files with readline() and write() methods."""
  96     new = ''
  97     while 1:
  98         line = input.readline()
  99         if not line: break
 100         i, n = 0, len(line)
 101         if n > 0 and line[n-1] == '\n':
 102             partial = 0; n = n-1
 103             # Strip trailing whitespace
 104             while n > 0 and line[n-1] in " \t\r":
 105                 n = n-1
 106         else:
 107             partial = 1
 108         while i < n:
 109             c = line[i]
 110             if c != ESCAPE:
 111                 new = new + c; i = i+1
 112             elif i+1 == n and not partial:
 113                 partial = 1; break
 114             elif i+1 < n and line[i+1] == ESCAPE:
 115                 new = new + ESCAPE; i = i+2
 116             elif i+2 < n and ishex(line[i+1]) and ishex(line[i+2]):
 117                 new = new + chr(unhex(line[i+1:i+3])); i = i+3
 118             else: # Bad escape sequence -- leave it in
 119                 new = new + c; i = i+1
 120         if not partial:
 121             output.write(new + '\n')
 122             new = ''
 123     if new:
 124         output.write(new)
 125
 126 def decodestring(s):
 127     from cStringIO import StringIO
 128     infp = StringIO(s)
 129     outfp = StringIO()
 130     decode(infp, outfp)
 131     return outfp.getvalue()
 132
 133
 134
 135 # Other helper functions
 136 def ishex(c):
 137     """Return true if the character 'c' is a hexadecimal digit."""
 138     return '0' <= c <= '9' or 'a' <= c <= 'f' or 'A' <= c <= 'F'
 139
 140 def unhex(s):
 141     """Get the integer value of a hexadecimal number."""
 142     bits = 0
 143     for c in s:
 144         if '0' <= c <= '9':
 145             i = ord('0')
 146         elif 'a' <= c <= 'f':
 147             i = ord('a')-10
 148         elif 'A' <= c <= 'F':
 149             i = ord('A')-10
 150         else:
 151             break
 152         bits = bits*16 + (ord(c) - i)
 153     return bits
 154
 155
 156
 157 def main():
 158     import sys
 159     import getopt
 160     try:
 161         opts, args = getopt.getopt(sys.argv[1:], 'td')
 162     except getopt.error, msg:
 163         sys.stdout = sys.stderr
 164         print msg
 165         print "usage: quopri [-t | -d] [file] ..."
 166         print "-t: quote tabs"
 167         print "-d: decode; default encode"
 168         sys.exit(2)
 169     deco = 0
 170     tabs = 0
 171     for o, a in opts:
 172         if o == '-t': tabs = 1
 173         if o == '-d': deco = 1
 174     if tabs and deco:
 175         sys.stdout = sys.stderr
 176         print "-t and -d are mutually exclusive"
 177         sys.exit(2)
 178     if not args: args = ['-']
 179     sts = 0
 180     for file in args:
 181         if file == '-':
 182             fp = sys.stdin
 183         else:
 184             try:
 185                 fp = open(file)
 186             except IOError, msg:
 187                 sys.stderr.write("%s: can't open (%s)\n" % (file, msg))
 188                 sts = 1
 189                 continue
 190         if deco:
 191             decode(fp, sys.stdout)
 192         else:
 193             encode(fp, sys.stdout, tabs)
 194         if fp is not sys.stdin:
 195             fp.close()
 196     if sts:
 197         sys.exit(sts)
 198
 199
 200
 201 if __name__ == '__main__':
 202     main()