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477 lines
14 KiB
HTML
477 lines
14 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
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"http://www.w3.org/TR/html4/strict.dtd">
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<html>
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<head>
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<meta name="description" content="LuaSocket: MIME support">
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<meta name="keywords" content="Lua, LuaSocket, MIME, Library, Support">
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<title>LuaSocket: MIME module</title>
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<link rel="stylesheet" href="reference.css" type="text/css">
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</head>
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<body>
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<!-- header +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<div class=header>
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<hr>
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<center>
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<table summary="LuaSocket logo">
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<tr><td align=center><a href="http://www.lua.org">
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<img width=128 height=128 border=0 alt="LuaSocket" src="luasocket.png">
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</a></td></tr>
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<tr><td align=center valign=top>Network support for the Lua language
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</td></tr>
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</table>
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<p class=bar>
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<a href="home.html">home</a> ·
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<a href="home.html#download">download</a> ·
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<a href="installation.html">installation</a> ·
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<a href="introduction.html">introduction</a> ·
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<a href="reference.html">reference</a>
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</p>
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</center>
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<hr>
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</div>
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<!-- mime +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<h2 id=mime>MIME</h2>
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<p>
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The <tt>mime</tt> namespace offers filters that apply and remove common
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content transfer encodings, such as Base64 and Quoted-Printable.
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It also provides functions to break text into lines and change
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the end-of-line convention.
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MIME is described mainly in
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<a href="http://www.cs.princeton.edu/~diego/rfc/rfc2045.txt">RFC 2045</a>,
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<a href="http://www.cs.princeton.edu/~diego/rfc/rfc2046.txt">2046</a>,
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<a href="http://www.cs.princeton.edu/~diego/rfc/rfc2047.txt">2047</a>,
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<a href="http://www.cs.princeton.edu/~diego/rfc/rfc2047.txt">2048</a>, and
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<a href="http://www.cs.princeton.edu/~diego/rfc/rfc2048.txt">2049</a>.
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</p>
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<p>
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All functionality provided by the MIME module
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follows the ideas presented in
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<a href="http://lua-users.org/wiki/FiltersSourcesAndSinks">
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LTN012, Filters sources and sinks</a>.
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</p>
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<p>
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To obtain the <tt>mime</tt> namespace, run:
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</p>
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<pre class=example>
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-- loads the MIME module and everything it requires
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local mime = require("mime")
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</pre>
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<!-- High-level +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<h3 id=high>High-level filters</h3>
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<!-- normalize ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class=name id="normalize">
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mime.<b>normalize(</b>[marker]<b>)</b>
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</p>
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<p class=description>
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Converts most common end-of-line markers to a specific given marker.
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</p>
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<p class=parameters>
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<tt>Marker</tt> is the new marker. It defaults to CRLF, the canonic
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end-of-line marker defined by the MIME standard.
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</p>
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<p class=return>
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The function returns a filter that performs the conversion.
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</p>
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<p class=note>
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Note: There is no perfect solution to this problem. Different end-of-line
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markers are an evil that will probably plague developers forever.
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This function, however, will work perfectly for text created with any of
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the most common end-of-line markers, i.e. the Mac OS (CR), the Unix (LF),
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or the DOS (CRLF) conventions. Even if the data has mixed end-of-line
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markers, the function will still work well, although it doesn't
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guarantee that the number of empty lines will be correct.
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</p>
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<!-- decode +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class=name id="decode">
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mime.<b>decode(</b>"base64"<b>)</b><br>
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mime.<b>decode(</b>"quoted-printable"<b>)</b>
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</p>
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<p class=description>
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Returns a filter that decodes data from a given transfer content
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encoding.
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</p>
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<!-- encode +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class=name id="encode">
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mime.<b>encode(</b>"base64"<b>)</b><br>
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mime.<b>encode(</b>"quoted-printable" [, mode]<b>)</b>
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</p>
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<p class=description>
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Returns a filter that encodes data according to a given transfer content
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encoding.
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</p>
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<p class=parameters>
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In the Quoted-Printable case, the user can specify whether the data is
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textual or binary, by passing the <tt>mode</tt> strings "<tt>text</tt>" or
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"<tt>binary</tt>". <tt>Mode</tt> defaults to "<tt>text</tt>".
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</p>
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<p class=note>
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Although both transfer content encodings specify a limit for the line
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length, the encoding filters do <em>not</em> break text into lines (for
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added flexibility).
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Below is a filter that converts binary data to the Base64 transfer content
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encoding and breaks it into lines of the correct size.
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</p>
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<pre class=example>
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base64 = ltn12.filter.chain(
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mime.encode("base64"),
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mime.wrap("base64")
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)
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</pre>
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<p class=note>
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Note: Text data <em>has</em> to be converted to canonic form
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<em>before</em> being encoded.
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</p>
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<pre class=example>
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base64 = ltn12.filter.chain(
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mime.normalize(),
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mime.encode("base64"),
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mime.wrap("base64")
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)
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</pre>
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<!-- stuff +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class=name id="stuff">
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mime.<b>stuff()</b><br>
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</p>
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<p class=description>
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Creates and returns a filter that performs stuffing of SMTP messages.
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</p>
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<p class=note>
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Note: The <a href=smtp.html#send><tt>smtp.send</tt></a> function
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uses this filter automatically. You don't need to chain it with your
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source, or apply it to your message body.
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</p>
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<!-- wrap +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class=name id="wrap">
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mime.<b>wrap(</b>"text" [, length]<b>)</b><br>
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mime.<b>wrap(</b>"base64"<b>)</b><br>
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mime.<b>wrap(</b>"quoted-printable"<b>)</b>
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</p>
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<p class=description>
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Returns a filter that breaks data into lines.
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</p>
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<p class=parameters>
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The "<tt>text</tt>" line-wrap filter simply breaks text into lines by
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inserting CRLF end-of-line markers at appropriate positions.
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<tt>Length</tt> defaults 76.
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The "<tt>base64</tt>" line-wrap filter works just like the default
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"<tt>text</tt>" line-wrap filter with default length.
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The function can also wrap "<tt>quoted-printable</tt>" lines, taking care
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not to break lines in the middle of an escaped character. In that case, the
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line length is fixed at 76.
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</p>
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<p class=note>
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For example, to create an encoding filter for the Quoted-Printable transfer content encoding of text data, do the following:
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</p>
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<pre class=example>
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qp = ltn12.filter.chain(
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mime.normalize(),
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mime.encode("quoted-printable"),
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mime.wrap("quoted-printable")
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)
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</pre>
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<p class=note>
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Note: To break into lines with a different end-of-line convention, apply
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a normalization filter after the line break filter.
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</p>
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<!-- Low-level ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<h3 id=low>Low-level filters</h3>
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<!-- b64 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class=name id="b64">
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A, B = mime.<b>b64(</b>C [, D]<b>)</b>
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</p>
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<p class=description>
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Low-level filter to perform Base64 encoding.
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</p>
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<p class=description>
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<tt>A</tt> is the encoded version of the largest prefix of
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<tt>C..D</tt>
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that can be encoded unambiguously. <tt>B</tt> has the remaining bytes of
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<tt>C..D</tt>, <em>before</em> encoding.
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If <tt>D</tt> is <tt><b>nil</b></tt>, <tt>A</tt> is padded with
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the encoding of the remaining bytes of <tt>C</tt>.
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</p>
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<p class=note>
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Note: The simplest use of this function is to encode a string into it's
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Base64 transfer content encoding. Notice the extra parenthesis around the
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call to <tt>mime.b64</tt>, to discard the second return value.
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</p>
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<pre class=example>
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print((mime.b64("diego:password")))
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--> ZGllZ286cGFzc3dvcmQ=
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</pre>
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<!-- dot +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class=name id="dot">
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A, n = mime.<b>dot(</b>m [, B]<b>)</b>
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</p>
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<p class=description>
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Low-level filter to perform SMTP stuffing and enable transmission of
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messages containing the sequence "CRLF.CRLF".
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</p>
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<p class=parameters>
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<tt>A</tt> is the stuffed version of <tt>B</tt>. '<tt>n</tt>' gives the
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number of characters from the sequence CRLF seen in the end of <tt>B</tt>.
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'<tt>m</tt>' should tell the same, but for the previous chunk.
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</p>
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<p class=note>Note: The message body is defined to begin with
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an implicit CRLF. Therefore, to stuff a message correctly, the
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first <tt>m</tt> should have the value 2.
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</p>
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<pre class=example>
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print((string.gsub(mime.dot(2, ".\r\nStuffing the message.\r\n.\r\n."), "\r\n", "\\n")))
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--> ..\nStuffing the message.\n..\n..
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</pre>
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<p class=note>
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Note: The <a href=smtp.html#send><tt>smtp.send</tt></a> function
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uses this filter automatically. You don't need to
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apply it again.
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</p>
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<!-- eol ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class=name id="eol">
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A, B = mime.<b>eol(</b>C [, D, marker]<b>)</b>
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</p>
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<p class=description>
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Low-level filter to perform end-of-line marker translation.
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For each chunk, the function needs to know if the last character of the
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previous chunk could be part of an end-of-line marker or not. This is the
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context the function receives besides the chunk. An updated version of
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the context is returned after each new chunk.
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</p>
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<p class=parameters>
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<tt>A</tt> is the translated version of <tt>D</tt>. <tt>C</tt> is the
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ASCII value of the last character of the previous chunk, if it was a
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candidate for line break, or 0 otherwise.
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<tt>B</tt> is the same as <tt>C</tt>, but for the current
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chunk. <tt>Marker</tt> gives the new end-of-line marker and defaults to CRLF.
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</p>
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<pre class=example>
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-- translates the end-of-line marker to UNIX
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unix = mime.eol(0, dos, "\n")
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</pre>
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<!-- qp ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class=name id="qp">
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A, B = mime.<b>qp(</b>C [, D, marker]<b>)</b>
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</p>
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<p class=description>
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Low-level filter to perform Quoted-Printable encoding.
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</p>
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<p class=parameters>
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<tt>A</tt> is the encoded version of the largest prefix of
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<tt>C..D</tt>
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that can be encoded unambiguously. <tt>B</tt> has the remaining bytes of
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<tt>C..D</tt>, <em>before</em> encoding.
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If <tt>D</tt> is <tt><b>nil</b></tt>, <tt>A</tt> is padded with
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the encoding of the remaining bytes of <tt>C</tt>.
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Throughout encoding, occurrences of CRLF are replaced by the
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<tt>marker</tt>, which itself defaults to CRLF.
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</p>
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<p class=note>
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Note: The simplest use of this function is to encode a string into it's
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Quoted-Printable transfer content encoding.
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Notice the extra parenthesis around the call to <tt>mime.qp</tt>, to discard the second return value.
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</p>
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<pre class=example>
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print((mime.qp("ma<6D><61>")))
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--> ma=E7=E3=
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</pre>
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<!-- qpwrp ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class=name id="qpwrp">
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A, m = mime.<b>qpwrp(</b>n [, B, length]<b>)</b>
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</p>
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<p class=description>
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Low-level filter to break Quoted-Printable text into lines.
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</p>
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<p class=parameters>
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<tt>A</tt> is a copy of <tt>B</tt>, broken into lines of at most
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<tt>length</tt> bytes (defaults to 76).
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'<tt>n</tt>' should tell how many bytes are left for the first
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line of <tt>B</tt> and '<tt>m</tt>' returns the number of bytes
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left in the last line of <tt>A</tt>.
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</p>
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<p class=note>
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Note: Besides breaking text into lines, this function makes sure the line
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breaks don't fall in the middle of an escaped character combination. Also,
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this function only breaks lines that are bigger than <tt>length</tt> bytes.
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</p>
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<!-- unb64 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class=name id="unb64">
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A, B = mime.<b>unb64(</b>C [, D]<b>)</b>
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</p>
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<p class=description>
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Low-level filter to perform Base64 decoding.
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</p>
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<p class=parameters>
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<tt>A</tt> is the decoded version of the largest prefix of
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<tt>C..D</tt>
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that can be decoded unambiguously. <tt>B</tt> has the remaining bytes of
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<tt>C..D</tt>, <em>before</em> decoding.
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If <tt>D</tt> is <tt><b>nil</b></tt>, <tt>A</tt> is the empty string
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and <tt>B</tt> returns whatever couldn't be decoded.
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</p>
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<p class=note>
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Note: The simplest use of this function is to decode a string from it's
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Base64 transfer content encoding.
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Notice the extra parenthesis around the call to <tt>mime.unqp</tt>, to discard the second return value.
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</p>
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<pre class=example>
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print((mime.unb64("ZGllZ286cGFzc3dvcmQ=")))
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--> diego:password
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</pre>
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<!-- unqp +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class=name id="unqp">
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A, B = mime.<b>unqp(</b>C [, D]<b>)</b>
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</p>
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<p class=description>
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Low-level filter to remove the Quoted-Printable transfer content encoding
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from data.
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</p>
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<p class=parameters>
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<tt>A</tt> is the decoded version of the largest prefix of
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<tt>C..D</tt>
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that can be decoded unambiguously. <tt>B</tt> has the remaining bytes of
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<tt>C..D</tt>, <em>before</em> decoding.
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If <tt>D</tt> is <tt><b>nil</b></tt>, <tt>A</tt> is augmented with
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the encoding of the remaining bytes of <tt>C</tt>.
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</p>
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<p class=note>
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Note: The simplest use of this function is to decode a string from it's
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Quoted-Printable transfer content encoding.
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Notice the extra parenthesis around the call to <tt>mime.unqp</tt>, to discard the second return value.
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</p>
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<pre class=example>
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print((mime.qp("ma=E7=E3=")))
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--> ma<6D><61>
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</pre>
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<!-- wrp ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class=name id="wrp">
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A, m = mime.<b>wrp(</b>n [, B, length]<b>)</b>
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</p>
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<p class=description>
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Low-level filter to break text into lines with CRLF marker.
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Text is assumed to be in the <a href=#normalize><tt>normalize</tt></a> form.
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</p>
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<p class=parameters>
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<tt>A</tt> is a copy of <tt>B</tt>, broken into lines of at most
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<tt>length</tt> bytes (defaults to 76).
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'<tt>n</tt>' should tell how many bytes are left for the first
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line of <tt>B</tt> and '<tt>m</tt>' returns the number of bytes
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left in the last line of <tt>A</tt>.
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</p>
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<p class=note>
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Note: This function only breaks lines that are bigger than
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<tt>length</tt> bytes. The resulting line length does not include the CRLF
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marker.
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</p>
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<!-- footer +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<div class=footer>
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<hr>
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<center>
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<p class=bar>
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<a href="home.html">home</a> ·
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||
<a href="home.html#down">download</a> ·
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||
<a href="installation.html">installation</a> ·
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<a href="introduction.html">introduction</a> ·
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||
<a href="reference.html">reference</a>
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</p>
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<p>
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<small>
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Last modified by Diego Nehab on <br>
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Mon Nov 21 01:57:51 EST 2005
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</small>
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</p>
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</center>
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</div>
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</body>
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</html>
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