mirror of
https://github.com/lunarmodules/luasocket.git
synced 2024-11-16 18:28:21 +01:00
5b8d7dec54
Update get.lua to use the new callbacks.
The old "code" module is now the "mime" module.
Updated all modules that depended on it.
Updated url.lua to use the new namespace scheme, and moved the
escape and unescape functions that used to be in the code.lua module
to it, since these are specific to urls.
Updated the callback entries in the manual.
167 lines
5.0 KiB
HTML
167 lines
5.0 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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<title>LuaSocket: Network support for the Lua language</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 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="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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<!-- stream ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<h2 id=stream>Streaming with Callbacks</h2>
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<p>
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HTTP, FTP, and SMTP transfers sometimes involve large amounts of
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information. Sometimes an application needs to generate outgoing data
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in real time, or needs to process incoming information as it is being
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received. To address these problems, LuaSocket allows HTTP and SMTP message
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bodies and FTP file contents to be received or sent through the
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callback mechanism outlined below.
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</p>
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<p>
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Instead of returning the entire contents of an entity
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as strings to the Lua application, the library allows the user to
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provide a <em>receive callback</em> that will be called with successive
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chunks of data, as the data becomes available. Conversely, the <em>send
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callbacks</em> can be used when the application wants to incrementally
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provide LuaSocket with the data to be sent.
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</p>
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<!-- tohostname +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class=name id=receive_cb>
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<b>receive_cb(</b>chunk, err<b>)</b>
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</p>
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<p class=description>
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The callback provided by the user will be repeatedly called by the
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library whenever new data is available. Each time it is called, the
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callback receives successive chunks of downloaded data.
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</p>
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<p class=parameters>
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<tt>Chunk</tt> contains the current chunk of data.
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When the transmission is over, the function is called with an
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empty string (i.e. <tt>""</tt>) as the <tt>chunk</tt>.
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If an error occurs, the function receives <tt>nil</tt>
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as <tt>chunk</tt> and an error message in <tt>err</tt>.
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</p>
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<p class=return>
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The callback can abort transmission by returning <tt>nil</tt> as its first
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return value, and an optional error message as the
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second return value. If the application wants to continue receiving
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data, the function should return non-<tt>nil</tt> as it's first return
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value. In this case, the function can optionally return a
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new callback function, to replace itself, as the second return value.
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</p>
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<p class=note>
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Note: The <tt>callback</tt> module provides several standard receive callbacks, including the following:
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</p>
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<pre class=example>
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function receive.concat(concat)
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concat = concat or socket.concat.create()
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local callback = function(chunk, err)
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-- if not finished, add chunk
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if chunk and chunk ~= "" then
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concat:addstring(chunk)
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return 1
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end
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end
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return callback, concat
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end
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</pre>
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<p class=note>
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This function creates a new receive callback that concatenates all
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received chunks into a the same concat object, which can later be
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queried for its contents.
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</p>
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<!-- send_cb ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
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<p class=name>
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<b>send_cb()</b>
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</p>
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<p class=description>
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The callback provided by the user will be repeatedly called whenever the
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library needs more data to be sent.
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</p>
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<p class=return>
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Each time the callback is called, it should return the next chunk of data. It
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can optionally return, as it's second return value, a new callback to replace
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itself. The callback can abort the process at any time by returning
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<tt>nil</tt> followed by an optional error message.
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</p>
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<p class=note>
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Note: Below is the implementation of the <tt>callback.send.file</tt>
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function. Given an open file handle, it returns a send callback that will send the contents of that file, chunk by chunk.
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</p>
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<pre class=example>
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function send.file(file, io_err)
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-- if successful, return the callback that reads from the file
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if file then
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return function()
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-- send next block of data
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return (file:read(BLOCKSIZE)) or ""
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end
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-- else, return a callback that just aborts the transfer
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else return fail(io_err or "unable to open file") end
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end
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</pre>
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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="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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Sat Aug 9 01:00:41 PDT 2003
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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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