htuu_string.cc

liburl是一个小的C++库

/*
  $Id: htuu_string.cc,v 1.2 2002/04/04 17:30:29 t16 Exp $

  HTUU encoded string implementation.
  Copyright (C) 2002  Kasper Peeters <[e-mail]>

  This program and its components are free software; you can
  redistribute it and/or modify it under the terms of the GNU General
  Public License as published by the Free Software Foundation; either
  version 2, or (at your option) any later version.
 
  This program and its components are distributed in the hope that it
  will be useful, but WITHOUT ANY WARRANTY; without even the implied
  warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
  the GNU General Public License for more details.
 
  You should have received a copy of the GNU General Public License in
  the file COPYING accompanying this program; if not, write to the
  Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

  Based on code by
  MR	Mark Riordan	[e-mail]
  AL	Ari Luotonen	[e-mail]
*/

/*
  File containing routines to convert a buffer
  of bytes to/from RFC 1113 printable encoding format.

  This technique is similar to the familiar Unix uuencode
  format in that it maps 6 binary bits to one ASCII
  character (or more aptly, 3 binary bytes to 4 ASCII
  characters).  However, RFC 1113 does not use the same
  mapping to printable characters as uuencode.

  Mark Riordan   12 August 1990 and 17 Feb 1991.
  This code is hereby placed in the public domain.
*/

#include <url/htuu_string.hh>

char six2pr[64] = {
    'A','B','C','D','E','F','G','H','I','J','K','L','M',
    'N','O','P','Q','R','S','T','U','V','W','X','Y','Z',
    'a','b','c','d','e','f','g','h','i','j','k','l','m',
    'n','o','p','q','r','s','t','u','v','w','x','y','z',
    '0','1','2','3','4','5','6','7','8','9','+','/'
};

unsigned char pr2six[256];


/*--- function HTUU_encode -----------------------------------------------
 *
 *   Encode a single line of binary data to a standard format that
 *   uses only printing ASCII characters (but takes up 33% more bytes).
 *
 *    Entry    bufin    points to a buffer of bytes.  If nbytes is not
 *                      a multiple of three, then the byte just beyond
 *                      the last byte in the buffer must be 0.
 *             nbytes   is the number of bytes in that buffer.
 *                      This cannot be more than 48.
 *             bufcoded points to an output buffer.  Be sure that this
 *                      can hold at least 1 + (4*nbytes)/3 characters.
 *
 *    Exit     bufcoded contains the coded line.  The first 4*nbytes/3 bytes
 *                      contain printing ASCII characters representing
 *                      those binary bytes. This may include one or
 *                      two '=' characters used as padding at the end.
 *                      The last byte is a zero byte.
 *             Returns the number of ASCII characters in "bufcoded".
 */

template<class InputIterator, class OutputIterator>
void htuu_encode(InputIterator begin, InputIterator end, OutputIterator out)
	{
	bool b2,b3;
	InputIterator::value_type i1,i2,i3,i4;

	while(begin!=end) {
		i1=i2=i3=i4=0;
		b2=b3=false;

		i1=*(begin++);
		if(begin!=end) { i2=*(begin++); b2=true; }
		if(begin!=end) { i3=*(begin++); b3=true; }

		*(out++) = six2pr[ i1 >> 2 ];
		*(out++) = six2pr[ ((i1 << 4) & 060) | ((i2 >> 4) & 017)]; 
		if(b2)
			*(out++) = six2pr[ ((i2 << 2) & 074) | ((i3 >> 6) & 03)];
		else 
			*(out++) = '=';
		if(b3)
			*(out++) = six2pr[ i3 & 077];
		else 
			*(out++) = '=';
		}
	}


/*--- function HTUU_decode ------------------------------------------------
 *
 *  Decode an ASCII-encoded buffer back to its original binary form.
 *
 *    Entry    bufcoded    points to a uuencoded string.  It is 
 *                         terminated by any character not in
 *                         the printable character table six2pr, but
 *                         leading whitespace is stripped.
 *             bufplain    points to the output buffer; must be big
 *                         enough to hold the decoded string (generally
 *                         shorter than the encoded string) plus
 *                         as many as two extra bytes used during
 *                         the decoding process.
 *             outbufsize  is the maximum number of bytes that
 *                         can fit in bufplain.
 *
 *    Exit     Returns the number of binary bytes decoded.
 *             bufplain    contains these bytes.
 */
int HTUU_decode (char *		bufcoded,
			     unsigned char *	bufplain,
			     int		outbufsize)
{
/* single character decode */
#define DEC(c) pr2six[c]
#define MAXVAL 63

   static int first = 1;

   int nbytesdecoded, j;
   register char *bufin = bufcoded;
   register unsigned char *bufout = bufplain;
   register int nprbytes;

   /* If this is the first call, initialize the mapping table.
    * This code should work even on non-ASCII machines.
    */
   if(first) {
      first = 0;
      for(j=0; j<256; j++) pr2six[j] = MAXVAL+1;

      for(j=0; j<64; j++) pr2six[(unsigned char)six2pr[j]] = (unsigned char)j;
#if 0
      pr2six['A']= 0; pr2six['B']= 1; pr2six['C']= 2; pr2six['D']= 3; 
      pr2six['E']= 4; pr2six['F']= 5; pr2six['G']= 6; pr2six['H']= 7; 
      pr2six['I']= 8; pr2six['J']= 9; pr2six['K']=10; pr2six['L']=11; 
      pr2six['M']=12; pr2six['N']=13; pr2six['O']=14; pr2six['P']=15; 
      pr2six['Q']=16; pr2six['R']=17; pr2six['S']=18; pr2six['T']=19; 
      pr2six['U']=20; pr2six['V']=21; pr2six['W']=22; pr2six['X']=23; 
      pr2six['Y']=24; pr2six['Z']=25; pr2six['a']=26; pr2six['b']=27; 
      pr2six['c']=28; pr2six['d']=29; pr2six['e']=30; pr2six['f']=31; 
      pr2six['g']=32; pr2six['h']=33; pr2six['i']=34; pr2six['j']=35; 
      pr2six['k']=36; pr2six['l']=37; pr2six['m']=38; pr2six['n']=39; 
      pr2six['o']=40; pr2six['p']=41; pr2six['q']=42; pr2six['r']=43; 
      pr2six['s']=44; pr2six['t']=45; pr2six['u']=46; pr2six['v']=47; 
      pr2six['w']=48; pr2six['x']=49; pr2six['y']=50; pr2six['z']=51; 
      pr2six['0']=52; pr2six['1']=53; pr2six['2']=54; pr2six['3']=55; 
      pr2six['4']=56; pr2six['5']=57; pr2six['6']=58; pr2six['7']=59; 
      pr2six['8']=60; pr2six['9']=61; pr2six['+']=62; pr2six['/']=63;
#endif
   }

   /* Strip leading whitespace. */

   while(*bufcoded==' ' || *bufcoded == '\t') bufcoded++;

   /* Figure out how many characters are in the input buffer.
    * If this would decode into more bytes than would fit into
    * the output buffer, adjust the number of input bytes downwards.
    */
   bufin = bufcoded;
   while(pr2six[(unsigned char)*(bufin++)] <= MAXVAL);
   nprbytes = bufin - bufcoded - 1;
   nbytesdecoded = ((nprbytes+3)/4) * 3;
   if(nbytesdecoded > outbufsize) {
      nprbytes = (outbufsize*4)/3;
   }

   bufin = bufcoded;
   
   while (nprbytes > 0) {
      *(bufout++) = (unsigned char) (DEC(*bufin) << 2 | DEC(bufin[1]) >> 4);
      *(bufout++) = (unsigned char) (DEC(bufin[1]) << 4 | DEC(bufin[2]) >> 2);
      *(bufout++) = (unsigned char) (DEC(bufin[2]) << 6 | DEC(bufin[3]));
      bufin += 4;
      nprbytes -= 4;
   }
   
   if(nprbytes & 03) {
      if(pr2six[bufin[-2]] > MAXVAL) {
         nbytesdecoded -= 2;
      } else {
         nbytesdecoded -= 1;
      }
   }

   return(nbytesdecoded);
}