rfc1523.txt

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RFC 1523           A text/enriched MIME Content-type      September 1993


   where the word "beloved" would be in red on a color display if the
   receiving software implemented the "x-color" extension.

Security Considerations

   Security issues are not discussed in this memo, as the mechanism
   raises no security issues.

Author's Address

   For more information, the author of this document may be contacted
   via Internet mail:

   Nathaniel S. Borenstein
   MRE 2D-296, Bellcore
   445 South St.
   Morristown, NJ 07962-1910

   Phone: [phone]
   Fax:  [phone]
   EMail: [e-mail]

Acknowledgements

   This document reflects the input of many contributors, readers, and
   implementors of the original MIME specification, RFC 1341.  This memo
   also reflects particular contributions and comments from Terry
   Crowley and Rhys Weatherley.























Borenstein                                                     [Page 11]

RFC 1523           A text/enriched MIME Content-type      September 1993


Appendix A -- A Simple enriched-to-plain Translator in C

   One of the major goals in the design of the text/enriched subtype of
   the text Content-Type is to make formatted text so simple that even
   text-only mailers will implement enriched-to-plain-text translators,
   thus increasing the likelihood that multifont text will become "safe"
   to use very widely.  To demonstrate this simplicity, what follows is
   a simple C program that converts text/enriched input into plain text
   output.  Note that the local newline convention (the single character
   represented by "\n") is assumed by this program, but that special
   CRLF handling might be necessary on some systems.


                 #include <stdio.h>
                 #include <ctype.h>

                 main() {
                     int c, i, paramct=0, newlinect=0, verbatim=0,
                 nofill=0;
                     char token[62], *p;

                     while ((c=getc(stdin)) != EOF) {
                         if (c == '<') {
                             if (verbatim != 0) {
                                 for (i=0, p=token; (*p++ = getc(stdin))
                 != EOF
                                     && !lc2strncmp(token, "/verbatim>",
                 i+1) && i<9; i++) {}
                                 if (i==9) {
                                     verbatim = 0;
                                 } else {
                                     *p = '\0';
                                     putc('<', stdout);
                                     fputs(token, stdout);
                                 }
                                 continue;
                             } else {
                                 newlinect=0;
                                 c = getc(stdin);
                                 if (c == '<') {
                                     if (paramct <= 0) putc(c, stdout);
                                 } else {
                                     ungetc(c, stdin);
                                     for (i=0, p=token; (c=getc(stdin))
                 != EOF && c != '>'; i++) {
                                         if (i < sizeof(token)-1) *p++ =
                 isupper(c) ? tolower(c) : c;
                                     }



Borenstein                                                     [Page 12]

RFC 1523           A text/enriched MIME Content-type      September 1993


                                     *p = '\0';
                                     if (c == EOF) break;
                                     if (strcmp(token, "param") == 0)
                                         paramct++;
                                     else if (strcmp(token, "verbatim")
                 == 0)
                                         verbatim = 1;
                                     else if (strcmp(token, "nofill") ==
                 0)
                                         nofill++;
                                     else if (strcmp(token, "/param") ==
                 0)
                                         paramct--;
                                     else if (strcmp(token, "/nofill")
                 == 0)

                                         nofill--;
                                 }
                             }
                      } else {
                         if (paramct > 0)
                           ; /* ignore params */
                            else if (c == '\n' && verbatim == 0 &&
                 nofill <= 0)
                                if (++newlinect > 1) {
                                    putc(c, stdout);
                                } else {
                                    putc(' ', stdout);
                                }
                            else {
                                newlinect = 0;
                                putc(c, stdout);
                            }
                      }
                     }
                     /* The following line is only needed with line-
                 buffering */
                     putc('\n', stdout);
                     exit(0);
                 }

                 lc2strncmp(s1, s2, len)
                 char *s1, *s2;
                 int len;
                 {
                     if (!s1 || !s2) return (-1);
                     while (*s1 && *s2 && len > 0) {
                      if (*s1 != *s2 && (tolower(*s1) != *s2)) return(-



Borenstein                                                     [Page 13]

RFC 1523           A text/enriched MIME Content-type      September 1993


                 1);
                      ++s1; ++s2; --len;
                     }
                     if (len <= 0) return(0);
                     return((*s1 == *s2) ? 0 : -1);
                 }

   It should be noted that one can do considerably better than this in
   displaying text/enriched data on a dumb terminal.  In particular, one
   can replace font information such as "bold" with textual emphasis
   (like *this* or _T_H_I_S_).  One can also properly handle the
   text/enriched formatting commands regarding indentation,
   justification, and others.  However, the above program is all that is
   necessary in order to present text/enriched on a dumb terminal
   without showing the user any formatting artifacts.

Appendix B -- Differences from RFC 1341 text/richtext

   Text/enriched is a clarification, simplification, and refinement of
   the type defined as text/richtext in RFC 1341.  For the benefit of
   those who are already familiar with text/richtext, or for those who
   want to exploit the similarities to be able to display text/richtext
   data with their text/enriched software, the differences between the
   two are summarized here. Note, however, that text/enriched is
   intended to make text/richtext obsolete, so it is not recommended
   that new software generate text/richtext.

   0.  The name "richtext" was changed to "enriched", both to
   differentiate the two versions and because "richtext" created
   widespread confusion with Microsoft's Rich Text Format (RTF).

   1.  Clarifications.  Many things were ambiguous or unspecified in the
   text/richtext definition, particularly the initial state and the
   semantics of richtext with multibyte character sets.  However, such
   differences are OPERATIONALLY irrelevant, since the clarifications
   offered in this document are at least reasonable interpretations of
   the text/richtext specification.

   2.  Newline semantics have changed.  In text/richtext, all CRLFs were
   mapped to spaces, and line breaks were indicated by "<nl>".  This has
   been replaced by the "n-1" rule for CRLFs.

   3.  The representation of a literal "<" character was "<lt>" in
   text/richtext, but is "<<" in text/enriched.

   4.  The "verbatim" and "nofill" commands did not exist in
   text/richtext.




Borenstein                                                     [Page 14]

RFC 1523           A text/enriched MIME Content-type      September 1993


   5.  The "param" command did not exist in text/richtext.

   6.  The following commands from text/richtext have been REMOVED from
   text/enriched: <COMMENT>, <OUTDENT>, <OUTDENTRIGHT>, <SAMEPAGE>,
   <SUBSCRIPT>, <SUPERSCRIPT>, <HEADING>, <FOOTING>, <ISO-8859-[1-9]>,
   <US-ASCII>, <PARAGRAPH>, <SIGNATURE>, <NO-OP>, <LT>, <NL>, and <NP>.

   7.  All claims of SGML compatibility have been dropped.  However,
   with the possible exceptions of the new semantics for CRLF and "<<"
   can be implemented, text/enriched should be no less SGML-friendly
   than text/richtext was.

   8.  In text/richtext, there were three commands (<NL>, <NP>, and
   <LT>) that did not use balanced closing delimiters.  Since all of
   these have been eliminated, there are NO exceptions to the
   nesting/balancing rules in text/enriched.

   9.  The limit on the size of formatting tokens has been increased
   from 40 to 60 characters.

   References

   [RFC-1341] Borenstein, N., and N.  Freed, "MIME (Multipurpose Internet
   Mail Extensions): Mechanisms for Specifying and Describing the Format
   of Internet Message Bodies", RFC 1341, Bellcore, Innosoft, June 1992.

   [RFC-1521] Borenstein, N., and N.  Freed, "MIME (Multipurpose Internet
   Mail Extensions) Part One: Mechanisms for Specifying and Describing
   the Format of Internet Message Bodies", RFC 1521, September 1993.






















Borenstein                                                     [Page 15]