rfc5092.txt

广泛使用的邮件服务器！同时

          /* enough bits for a UTF-16 character? */
          if (bitcount >= 16) {
              bitcount -= 16;
              utf16 = (bitcount ? bitbuf >> bitcount
                             : bitbuf) & 0xffff;
              /* convert UTF16 to UCS4 */
              if
                    (utf16 >= UTF16HIGHSTART && utf16 <= UTF16HIGHEND) {
               ucs4 = (utf16 - UTF16HIGHSTART) << UTF16SHIFT;
               continue;
              } else if
                    (utf16 >= UTF16LOSTART && utf16 <= UTF16LOEND) {
               ucs4 += utf16 - UTF16LOSTART + UTF16BASE;
              } else {



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               ucs4 = utf16;
              }
              /* convert UTF-16 range of UCS4 to UTF-8 */
              if (ucs4 <= 0x7fUL) {
               utf8[0] = (unsigned char) ucs4;
               i = 1;
              } else if (ucs4 <= 0x7ffUL) {
               utf8[0] = 0xc0 | (unsigned char) (ucs4 >> 6);
               utf8[1] = 0x80 | (unsigned char) (ucs4 & 0x3f);
               i = 2;
              } else if (ucs4 <= 0xffffUL) {
               utf8[0] = 0xe0 | (unsigned char) (ucs4 >> 12);
               utf8[1] = 0x80 | (unsigned char) ((ucs4 >> 6) & 0x3f);
               utf8[2] = 0x80 | (unsigned char) (ucs4 & 0x3f);
               i = 3;
              } else {
               utf8[0] = 0xf0 | (unsigned char) (ucs4 >> 18);
               utf8[1] = 0x80 | (unsigned char) ((ucs4 >> 12) & 0x3f);
               utf8[2] = 0x80 | (unsigned char) ((ucs4 >> 6) & 0x3f);
               utf8[3] = 0x80 | (unsigned char) (ucs4 & 0x3f);
               i = 4;
              }
              /* convert utf8 to hex */
              for (c = 0; c < i; ++c) {
               dst[0] = '%';
               dst[1] = hex[utf8[c] >> 4];
               dst[2] = hex[utf8[c] & 0x0f];
               dst += 3;
              }
          }
         }
         /* skip over trailing '-' in modified UTF-7 encoding */
         if (*src == '-') ++src;
     }
    }
    /* terminate destination string */
    *dst = '\0';
}

/* Convert hex coded UTF-8 URL path to modified UTF-7 IMAP mailbox
 *  dst should be about twice the length of src to deal with non-hex
 *  coded URLs
 */
int URLtoMailbox(char *dst, char *src)
{
    unsigned int utf8pos = 0;
    unsigned int utf8total, i, c, utf7mode, bitstogo, utf16flag;
    unsigned long ucs4 = 0, bitbuf = 0;



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    utf7mode = 0; /* is the output UTF7 currently in base64 mode? */
    utf8total = 0; /* how many octets is the current input UTF-8 char;
                      0 == between characters */
    bitstogo = 0; /* bits that need to be encoded into base64; if
                     bitstogo != 0 then utf7mode == 1 */
    while ((c = (unsigned char)*src) != '\0') {
     ++src;
     /* undo hex-encoding */
     if (c == '%' && src[0] != '\0' && src[1] != '\0') {
         c = HEXCHAR(src[0]);
         i = HEXCHAR(src[1]);
         if (c == XX || i == XX) {
             return 0;
         } else {
             c = (char)((c << 4) | i);
         }
         src += 2;
     }
     /* normal character? */
     if (c >= ' ' && c <= '~') {
         /* switch out of UTF-7 mode */
         if (utf7mode) {
          if (bitstogo) {
          *dst++ = base64chars[(bitbuf << (6 - bitstogo)) & 0x3F];
          }
          *dst++ = '-';
          utf7mode = 0;
          bitstogo = bitbuf = 0;
         }
         *dst++ = c;
         /* encode '&' as '&-' */
         if (c == '&') {
          *dst++ = '-';
         }
         continue;
     }
     /* switch to UTF-7 mode */
     if (!utf7mode) {
         *dst++ = '&';
         utf7mode = 1;
     }
     /* Encode US-ASCII characters as themselves */
     if (c < 0x80) {
         ucs4 = c;
         utf8total = 1;
     } else if (utf8total) {
         /* this is a subsequent octet of a multi-octet character */
         /* save UTF8 bits into UCS4 */



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         ucs4 = (ucs4 << 6) | (c & 0x3FUL);
         if (++utf8pos < utf8total) {
          continue;
         }
     } else {
         /* this is the first octet of a multi-octet character */
         utf8pos = 1;
         if (c < 0xE0) {
          utf8total = 2;
          ucs4 = c & 0x1F;
         } else if (c < 0xF0) {
          utf8total = 3;
          ucs4 = c & 0x0F;
         } else {
          /* NOTE: can't convert UTF8 sequences longer than 4 */
          utf8total = 4;
          ucs4 = c & 0x03;
         }
         continue;
     }
     /* Finished with UTF-8 character.  Make sure it isn't an
        overlong sequence.  If it is, return failure. */
     if ((ucs4 < 0x80 && utf8total > 1) ||
         (ucs4 < 0x0800 && utf8total > 2) ||
         (ucs4 < 0x00010000 && utf8total > 3) ||
         (ucs4 < 0x00200000 && utf8total > 4) ||
         (ucs4 < 0x04000000 && utf8total > 5) ||
         (ucs4 < 0x80000000 && utf8total > 6)) {
         return 0;
     }
     /* loop to split ucs4 into two utf16 chars if necessary */
     utf8total = 0;
     do {
         if (ucs4 >= UTF16BASE) {
                ucs4 -= UTF16BASE;
          bitbuf = (bitbuf << 16) | ((ucs4 >> UTF16SHIFT)
                            + UTF16HIGHSTART);
          ucs4 = (ucs4 & UTF16MASK) + UTF16LOSTART;
          utf16flag = 1;
         } else {
          bitbuf = (bitbuf << 16) | ucs4;
          utf16flag = 0;
         }
         bitstogo += 16;
         /* spew out base64 */
         while (bitstogo >= 6) {
          bitstogo -= 6;
          *dst++ = base64chars[(bitstogo ? (bitbuf >> bitstogo)



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                               : bitbuf)
                         & 0x3F];
         }
     } while (utf16flag);
    }
    /* if in UTF-7 mode, finish in ASCII */
    if (utf7mode) {
     if (bitstogo) {
         *dst++ = base64chars[(bitbuf << (6 - bitstogo)) & 0x3F];
     }
     *dst++ = '-';
    }
    /* tie off string */
    *dst = '\0';
    return 1;
}

Appendix B.  List of Changes since RFC 2192

   Updated boilerplate, list of editor's, etc.
   Updated references.
   Updated ABNF not to use _, to use SP instead of SPACE, etc.
   Updated example domains to use example.org.
   Fixed ABNF error in "imessagelist" non-terminal.
   Updated ABNF, due to changes in RFC 3501, RFC 4466, and RFC 3986.
   Renamed "iuserauth" non-terminal to <iuserinfo>.
   Clarified that the userinfo component describes both authorization
   identity and mailbox naming scope.
   Allow for non-synchronizing literals in "enc-search".
   Added "ipartial" specifier that denotes a partial FETCH.
   Moved URLAUTH text from RFC 4467 to this document.
   Updated ABNF for the whole server to allow missing trailing "/"
   (e.g., "imap://imap.example.com" is now valid and is the same as
   "imap://imap.example.com/").
   Clarified how relative-path references are constructed.
   Added more examples demonstrating relative-path references.
   Added rules for relative URLs and restructured ABNF as the result.
   Removed text on use of relative URLs in MHTML.
   Added examples demonstrating security considerations when resolving
   URLs.
   Recommend usage of STARTTLS/SASL security layer to protect
   confidential data.
   Removed some advices about connection reuse that were incorrect.
   Removed URLs referencing a list of mailboxes, as this feature
   hasn't seen any deployments.
   Clarified that user name "anonymous" is case-insensitive.





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Appendix C.  List of Changes since RFC 4467

   Renamed <mechanism> to <uauth-mechanism>.  Restructured ABNF.

Appendix D.  Acknowledgments

   Text describing URLAUTH was lifted from [URLAUTH] by Mark Crispin.

   Stephane H. Maes contributed some ideas to this document; he also
   co-edited early versions of this document.

   The editors would like to thank Mark Crispin, Ken Murchison, Ted
   Hardie, Zoltan Ordogh, Dave Cridland, Kjetil Torgrim Homme, Lisa
   Dusseault, Spencer Dawkins, Filip Navara, Shawn M. Emery, Sam
   Hartman, Russ Housley, and Lars Eggert for the time they devoted to
   reviewing this document and/or for the comments received.

Authors' Addresses

   Chris Newman (Author/Editor)
   Sun Microsystems
   3401 Centrelake Dr., Suite 410
   Ontario, CA 91761
   EMail: [e-mail]

   Alexey Melnikov (Editor)
   Isode Limited
   5 Castle Business Village
   36 Station Road
   Hampton, Middlesex
   TW12 2BX, UK
   EMail: [e-mail]
   URI:   http://www.melnikov.ca/


















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Full Copyright Statement

   Copyright (C) The IETF Trust (2007).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

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   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the procedures with respect to rights in RFC documents can be
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   Copies of IPR disclosures made to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
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   [e-mail].












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