Version 3 of HTML character entity references

aricb HTML character entity references are defined as part of the HTML specification: http://www.w3.org/TR/REC-html40/sgml/entities.html

The following code defines two commands, htmlentities::insertentities and htmlentities::removeentities. The first command replaces Unicode characters with HTML character entity references; the second command replaces HTML character entity references with the literal Unicode characters they represent. There's nothing fancy about the code, but hopefully it's useful to somebody.

  namespace eval htmlentities {
      variable map [list \
          \u00a0 &nbsp\;    \
          \u00a1 &iexcl\;   \
          \u00a2 &cent\;    \
          \u00a3 &pound\;   \
          \u00a4 &curren\;  \
          \u00a5 &yen\;     \
          \u00a6 &brvbar\;  \
          \u00a7 &sect\;    \
          \u00a8 &uml\;     \
          \u00a9 &copy\;    \
          \u00aa &ordf\;    \
          \u00ab &laquo\;   \
          \u00ac &not\;     \
          \u00ad &shy\;     \
          \u00ae &reg\;     \
          \u00af &macr\;    \
          \u00b0 &deg\;     \
          \u00b1 &plusmn\;  \
          \u00b2 &sup2\;    \
          \u00b3 &sup3\;    \
          \u00b4 &acute\;   \
          \u00b5 &micro\;   \
          \u00b6 &para\;    \
          \u00b7 &middot\;  \
          \u00b8 &cedil\;   \
          \u00b9 &sup1\;    \
          \u00ba &ordm\;    \
          \u00bb &raquo\;   \
          \u00bc &frac14\;  \
          \u00bd &frac12\;  \
          \u00be &frac34\;  \
          \u00bf &iquest\;  \
          \u00c0 &Agrave\;  \
          \u00c1 &Aacute\;  \
          \u00c2 &Acirc\;   \
          \u00c3 &Atilde\;  \
          \u00c4 &Auml\;    \
          \u00c5 &Aring\;   \
          \u00c6 &AElig\;   \
          \u00c7 &Ccedil\;  \
          \u00c8 &Egrave\;  \
          \u00c9 &Eacute\;  \
          \u00ca &Ecirc\;   \
          \u00cb &Euml\;    \
          \u00cc &Igrave\;  \
          \u00cd &Iacute\;  \
          \u00ce &Icirc\;   \
          \u00cf &Iuml\;    \
          \u00d0 &ETH\;     \
          \u00d1 &Ntilde\;  \
          \u00d2 &Ograve\;  \
          \u00d3 &Oacute\;  \
          \u00d4 &Ocirc\;   \
          \u00d5 &Otilde\;  \
          \u00d6 &Ouml\;    \
          \u00d7 &times\;   \
          \u00d8 &Oslash\;  \
          \u00d9 &Ugrave\;  \
          \u00da &Uacute\;  \
          \u00db &Ucirc\;   \
          \u00dc &Uuml\;    \
          \u00dd &Yacute\;  \
          \u00de &THORN\;   \
          \u00df &szlig\;   \
          \u00e0 &agrave\;  \
          \u00e1 &aacute\;  \
          \u00e2 &acirc\;   \
          \u00e3 &atilde\;  \
          \u00e4 &auml\;    \
          \u00e5 &aring\;   \
          \u00e6 &aelig\;   \
          \u00e7 &ccedil\;  \
          \u00e8 &egrave\;  \
          \u00e9 &eacute\;  \
          \u00ea &ecirc\;   \
          \u00eb &euml\;    \
          \u00ec &igrave\;  \
          \u00ed &iacute\;  \
          \u00ee &icirc\;   \
          \u00ef &iuml\;    \
          \u00f0 &eth\;     \
          \u00f1 &ntilde\;  \
          \u00f2 &ograve\;  \
          \u00f3 &oacute\;  \
          \u00f4 &ocirc\;   \
          \u00f5 &otilde\;  \
          \u00f6 &ouml\;    \
          \u00f7 &divide\;  \
          \u00f8 &oslash\;  \
          \u00f9 &ugrave\;  \
          \u00fa &uacute\;  \
          \u00fb &ucirc\;   \
          \u00fc &uuml\;    \
          \u00fd &yacute\;  \
          \u00fe &thorn\;   \
          \u00ff &yuml\;    \
          \u0192 &fnof\;    \
          \u0391 &Alpha\;   \
          \u0392 &Beta\;    \
          \u0393 &Gamma\;   \
          \u0394 &Delta\;   \
          \u0395 &Epsilon\; \
          \u0396 &Zeta\;    \
          \u0397 &Eta\;     \
          \u0398 &Theta\;   \
          \u0399 &Iota\;    \
          \u039a &Kappa\;   \
          \u039b &Lambda\;  \
          \u039c &Mu\;      \
          \u039d &Nu\;      \
          \u039e &Xi\;      \
          \u039f &Omicron\; \
          \u03a0 &Pi\;      \
          \u03a1 &Rho\;     \
          \u03a3 &Sigma\;   \
          \u03a4 &Tau\;     \
          \u03a5 &Upsilon\; \
          \u03a6 &Phi\;     \
          \u03a7 &Chi\;     \
          \u03a8 &Psi\;     \
          \u03a9 &Omega\;   \
          \u03b1 &alpha\;   \
          \u03b2 &beta\;    \
          \u03b3 &gamma\;   \
          \u03b4 &delta\;   \
          \u03b5 &epsilon\; \
          \u03b6 &zeta\;    \
          \u03b7 &eta\;     \
          \u03b8 &theta\;   \
          \u03b9 &iota\;    \
          \u03ba &kappa\;   \
          \u03bb &lambda\;  \
          \u03bc &mu\;      \
          \u03bd &nu\;      \
          \u03be &xi\;      \
          \u03bf &omicron\; \
          \u03c0 &pi\;      \
          \u03c1 &rho\;     \
          \u03c2 &sigmaf\;  \
          \u03c3 &sigma\;   \
          \u03c4 &tau\;     \
          \u03c5 &upsilon\; \
          \u03c6 &phi\;     \
          \u03c7 &chi\;     \
          \u03c8 &psi\;     \
          \u03c9 &omega\;   \
          \u03d1 &thetasym\; \
          \u03d2 &upsih\;   \
          \u03d6 &piv\;     \
          \u2022 &bull\;    \
          \u2026 &hellip\;  \
          \u2032 &prime\;   \
          \u2033 &Prime\;   \
          \u203e &oline\;   \
          \u2044 &frasl\;   \
          \u2118 &weierp\;  \
          \u2111 &image\;   \
          \u211c &real\;    \
          \u2122 &trade\;   \
          \u2135 &alefsym\; \
          \u2190 &larr\;    \
          \u2191 &uarr\;    \
          \u2192 &rarr\;    \
          \u2193 &darr\;    \
          \u2194 &harr\;    \
          \u21b5 &crarr\;   \
          \u21d0 &lArr\;    \
          \u21d1 &uArr\;    \
          \u21d2 &rArr\;    \
          \u21d3 &dArr\;    \
          \u21d4 &hArr\;    \
          \u2200 &forall\;  \
          \u2202 &part\;    \
          \u2203 &exist\;   \
          \u2205 &empty\;   \
          \u2207 &nabla\;   \
          \u2208 &isin\;    \
          \u2209 &notin\;   \
          \u220b &ni\;      \
          \u220f &prod\;    \
          \u2211 &sum\;     \
          \u2212 &minus\;   \
          \u2217 &lowast\;  \
          \u221a &radic\;   \
          \u221d &prop\;    \
          \u221e &infin\;   \
          \u2220 &ang\;     \
          \u2227 &and\;     \
          \u2228 &or\;      \
          \u2229 &cap\;     \
          \u222a &cup\;     \
          \u222b &int\;     \
          \u2234 &there4\;  \
          \u223c &sim\;     \
          \u2245 &cong\;    \
          \u2248 &asymp\;   \
          \u2260 &ne\;      \
          \u2261 &equiv\;   \
          \u2264 &le\;      \
          \u2265 &ge\;      \
          \u2282 &sub\;     \
          \u2283 &sup\;     \
          \u2284 &nsub\;    \
          \u2286 &sube\;    \
          \u2287 &supe\;    \
          \u2295 &oplus\;   \
          \u2297 &otimes\;  \
          \u22a5 &perp\;    \
          \u22c5 &sdot\;    \
          \u2308 &lceil\;   \
          \u2309 &rceil\;   \
          \u230a &lfloor\;  \
          \u230b &rfloor\;  \
          \u2329 &lang\;    \
          \u232a &rang\;    \
          \u25ca &loz\;     \
          \u2660 &spades\;  \
          \u2663 &clubs\;   \
          \u2665 &hearts\;  \
          \u2666 &diams\;   \
          \u0022 &quot\;    \
          \u0026 &amp\;     \
          \u003c &lt\;      \
          \u003e &gt\;      \
          \u0152 &OElig\;   \
          \u0153 &oelig\;   \
          \u0160 &Scaron\;  \
          \u0161 &scaron\;  \
          \u0178 &Yuml\;    \
          \u02c6 &circ\;    \
          \u02dc &tilde\;   \
          \u2002 &ensp\;    \
          \u2003 &emsp\;    \
          \u2009 &thinsp\;  \
          \u200c &zwnj\;    \
          \u200d &zwj\;     \
          \u200e &lrm\;     \
          \u200f &rlm\;     \
          \u2013 &ndash\;   \
          \u2014 &mdash\;   \
          \u2018 &lsquo\;   \
          \u2019 &rsquo\;   \
          \u201a &sbquo\;   \
          \u201c &ldquo\;   \
          \u201d &rdquo\;   \
          \u201e &bdquo\;   \
          \u2020 &dagger\;  \
          \u2021 &Dagger\;  \
          \u2030 &permil\;  \
          \u2039 &lsaquo\;  \
          \u203a &rsaquo\;  \
          \u20ac &euro\;    ]

      set reversemap [lreverse $map]

      proc insertentities {string} {
          variable map
          return [string map $map $string]
      }

      proc removeentities {string} {
          variable reversemap
          return [string map $reversemap $string]
      }
  }

AMG: Here's the same code, written in a somewhat more compressed manner. I took the liberty of using namespace ensembles and renaming the commands.

namespace eval htmlentities {
    namespace ensemble create -subcommands {encode decode}
    set encode [list {*}{
        \u00a0 &nbsp\; \u00a1 &iexcl\; \u00a2 &cent\; \u00a3 &pound\; \u00a4
        &curren\; \u00a5 &yen\; \u00a6 &brvbar\; \u00a7 &sect\; \u00a8 &uml\;
        \u00a9 &copy\; \u00aa &ordf\; \u00ab &laquo\; \u00ac &not\; \u00ad
        &shy\; \u00ae &reg\; \u00af &macr\; \u00b0 &deg\; \u00b1 &plusmn\;
        \u00b2 &sup2\; \u00b3 &sup3\; \u00b4 &acute\; \u00b5 &micro\; \u00b6
        &para\; \u00b7 &middot\; \u00b8 &cedil\; \u00b9 &sup1\; \u00ba &ordm\;
        \u00bb &raquo\; \u00bc &frac14\; \u00bd &frac12\; \u00be &frac34\;
        \u00bf &iquest\; \u00c0 &Agrave\; \u00c1 &Aacute\; \u00c2 &Acirc\;
        \u00c3 &Atilde\; \u00c4 &Auml\; \u00c5 &Aring\; \u00c6 &AElig\; \u00c7
        &Ccedil\; \u00c8 &Egrave\; \u00c9 &Eacute\; \u00ca &Ecirc\; \u00cb
        &Euml\; \u00cc &Igrave\; \u00cd &Iacute\; \u00ce &Icirc\; \u00cf
        &Iuml\; \u00d0 &ETH\; \u00d1 &Ntilde\; \u00d2 &Ograve\; \u00d3
        &Oacute\; \u00d4 &Ocirc\; \u00d5 &Otilde\; \u00d6 &Ouml\; \u00d7
        &times\; \u00d8 &Oslash\; \u00d9 &Ugrave\; \u00da &Uacute\; \u00db
        &Ucirc\; \u00dc &Uuml\; \u00dd &Yacute\; \u00de &THORN\; \u00df
        &szlig\; \u00e0 &agrave\; \u00e1 &aacute\; \u00e2 &acirc\; \u00e3
        &atilde\; \u00e4 &auml\; \u00e5 &aring\; \u00e6 &aelig\; \u00e7
        &ccedil\; \u00e8 &egrave\; \u00e9 &eacute\; \u00ea &ecirc\; \u00eb
        &euml\; \u00ec &igrave\; \u00ed &iacute\; \u00ee &icirc\; \u00ef
        &iuml\; \u00f0 &eth\; \u00f1 &ntilde\; \u00f2 &ograve\; \u00f3
        &oacute\; \u00f4 &ocirc\; \u00f5 &otilde\; \u00f6 &ouml\; \u00f7
        &divide\; \u00f8 &oslash\; \u00f9 &ugrave\; \u00fa &uacute\; \u00fb
        &ucirc\; \u00fc &uuml\; \u00fd &yacute\; \u00fe &thorn\; \u00ff &yuml\;
        \u0192 &fnof\; \u0391 &Alpha\; \u0392 &Beta\; \u0393 &Gamma\; \u0394
        &Delta\; \u0395 &Epsilon\; \u0396 &Zeta\; \u0397 &Eta\; \u0398 &Theta\;
        \u0399 &Iota\; \u039a &Kappa\; \u039b &Lambda\; \u039c &Mu\; \u039d
        &Nu\; \u039e &Xi\; \u039f &Omicron\; \u03a0 &Pi\; \u03a1 &Rho\; \u03a3
        &Sigma\; \u03a4 &Tau\; \u03a5 &Upsilon\; \u03a6 &Phi\; \u03a7 &Chi\;
        \u03a8 &Psi\; \u03a9 &Omega\; \u03b1 &alpha\; \u03b2 &beta\; \u03b3
        &gamma\; \u03b4 &delta\; \u03b5 &epsilon\; \u03b6 &zeta\; \u03b7 &eta\;
        \u03b8 &theta\; \u03b9 &iota\; \u03ba &kappa\; \u03bb &lambda\; \u03bc
        &mu\; \u03bd &nu\; \u03be &xi\; \u03bf &omicron\; \u03c0 &pi\; \u03c1
        &rho\; \u03c2 &sigmaf\; \u03c3 &sigma\; \u03c4 &tau\; \u03c5 &upsilon\;
        \u03c6 &phi\; \u03c7 &chi\; \u03c8 &psi\; \u03c9 &omega\; \u03d1
        &thetasym\; \u03d2 &upsih\; \u03d6 &piv\; \u2022 &bull\; \u2026
        &hellip\; \u2032 &prime\; \u2033 &Prime\; \u203e &oline\; \u2044
        &frasl\; \u2118 &weierp\; \u2111 &image\; \u211c &real\; \u2122
        &trade\; \u2135 &alefsym\; \u2190 &larr\; \u2191 &uarr\; \u2192 &rarr\;
        \u2193 &darr\; \u2194 &harr\; \u21b5 &crarr\; \u21d0 &lArr\; \u21d1
        &uArr\; \u21d2 &rArr\; \u21d3 &dArr\; \u21d4 &hArr\; \u2200 &forall\;
        \u2202 &part\; \u2203 &exist\; \u2205 &empty\; \u2207 &nabla\; \u2208
        &isin\; \u2209 &notin\; \u220b &ni\; \u220f &prod\; \u2211 &sum\;
        \u2212 &minus\; \u2217 &lowast\; \u221a &radic\; \u221d &prop\; \u221e
        &infin\; \u2220 &ang\; \u2227 &and\; \u2228 &or\; \u2229 &cap\; \u222a
        &cup\; \u222b &int\; \u2234 &there4\; \u223c &sim\; \u2245 &cong\;
        \u2248 &asymp\; \u2260 &ne\; \u2261 &equiv\; \u2264 &le\; \u2265 &ge\;
        \u2282 &sub\; \u2283 &sup\; \u2284 &nsub\; \u2286 &sube\; \u2287
        &supe\; \u2295 &oplus\; \u2297 &otimes\; \u22a5 &perp\; \u22c5 &sdot\;
        \u2308 &lceil\; \u2309 &rceil\; \u230a &lfloor\; \u230b &rfloor\;
        \u2329 &lang\; \u232a &rang\; \u25ca &loz\; \u2660 &spades\; \u2663
        &clubs\; \u2665 &hearts\; \u2666 &diams\; \u0022 &quot\; \u0026 &amp\;
        \u003c &lt\; \u003e &gt\; \u0152 &OElig\; \u0153 &oelig\; \u0160
        &Scaron\; \u0161 &scaron\; \u0178 &Yuml\; \u02c6 &circ\; \u02dc
        &tilde\; \u2002 &ensp\; \u2003 &emsp\; \u2009 &thinsp\; \u200c &zwnj\;
        \u200d &zwj\; \u200e &lrm\; \u200f &rlm\; \u2013 &ndash\; \u2014
        &mdash\; \u2018 &lsquo\; \u2019 &rsquo\; \u201a &sbquo\; \u201c
        &ldquo\; \u201d &rdquo\; \u201e &bdquo\; \u2020 &dagger\; \u2021
        &Dagger\; \u2030 &permil\; \u2039 &lsaquo\; \u203a &rsaquo\; \u20ac
        &euro\;
    }]
    set decode [lreverse $encode]
    proc encode {string} {
        variable encode
        string map $encode $string
    }
    proc decode {string} {
        variable decode
        string map $decode $string
    }
}

By the way, that's a very interesting use for [lreverse]!

If you look in the page history, you'll find my failed attempts to upload a UTF-8 version which avoids using \uXXXX escapes. But neither Firefox 3.6.3 nor IE8 could hack it, and I got mojibake [L1 ]. I'm not sure where the problem lies. I triple-checked that I had UTF-8 encoding set in my browser, both when viewing and when editing. Funny: even though that didn't work, I'm able to paste this text in without problems: 文字化け.