2003-08-31 03:00:15 +02:00
|
|
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
|
|
|
|
"http://www.w3.org/TR/html4/strict.dtd">
|
|
|
|
<html>
|
|
|
|
|
|
|
|
<head>
|
|
|
|
<title>LuaSocket: Network support for the Lua language</title>
|
|
|
|
<link rel="stylesheet" href="reference.css" type="text/css">
|
|
|
|
</head>
|
|
|
|
|
|
|
|
<body>
|
|
|
|
|
|
|
|
<!-- header +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
|
|
|
|
|
|
|
|
<div class=header>
|
|
|
|
<hr>
|
|
|
|
<center>
|
|
|
|
<table summary="LuaSocket logo">
|
|
|
|
<tr><td align=center><a href="http://www.lua.org">
|
|
|
|
<img border=0 alt="LuaSocket" src="luasocket.png">
|
|
|
|
</a></td></tr>
|
|
|
|
<tr><td align=center valign=top>Network support for the Lua language
|
|
|
|
</td></tr>
|
|
|
|
</table>
|
|
|
|
<p class=bar>
|
|
|
|
<a href="home.html">home</a> ·
|
|
|
|
<a href="home.html#download">download</a> ·
|
|
|
|
<a href="introduction.html">introduction</a> ·
|
|
|
|
<a href="reference.html">reference</a>
|
|
|
|
</p>
|
|
|
|
</center>
|
|
|
|
<hr>
|
|
|
|
</div>
|
|
|
|
|
|
|
|
<!-- stream ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
|
|
|
|
|
|
|
|
<h2 id=stream>Streaming with Callbacks</h2>
|
|
|
|
|
|
|
|
<p>
|
2004-01-19 06:41:30 +01:00
|
|
|
HTTP, FTP, and SMTP transfers sometimes involve large amounts of
|
|
|
|
information. Sometimes an application needs to generate outgoing data
|
|
|
|
in real time, or needs to process incoming information as it is being
|
|
|
|
received. To address these problems, LuaSocket allows HTTP and SMTP message
|
|
|
|
bodies and FTP file contents to be received or sent through the
|
|
|
|
callback mechanism outlined below.
|
2003-08-31 03:00:15 +02:00
|
|
|
</p>
|
|
|
|
|
|
|
|
<p>
|
2004-01-19 06:41:30 +01:00
|
|
|
Instead of returning the entire contents of an entity
|
|
|
|
as strings to the Lua application, the library allows the user to
|
2003-08-31 03:00:15 +02:00
|
|
|
provide a <em>receive callback</em> that will be called with successive
|
|
|
|
chunks of data, as the data becomes available. Conversely, the <em>send
|
2004-01-19 06:41:30 +01:00
|
|
|
callbacks</em> can be used when the application wants to incrementally
|
|
|
|
provide LuaSocket with the data to be sent.
|
2003-08-31 03:00:15 +02:00
|
|
|
</p>
|
|
|
|
|
|
|
|
<!-- tohostname +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
|
|
|
|
|
|
|
|
<p class=name id=receive_cb>
|
|
|
|
<b>receive_cb(</b>chunk, err<b>)</b>
|
|
|
|
</p>
|
|
|
|
|
|
|
|
<p class=description>
|
|
|
|
The callback provided by the user will be repeatedly called by the
|
|
|
|
library whenever new data is available. Each time it is called, the
|
|
|
|
callback receives successive chunks of downloaded data.
|
|
|
|
</p>
|
|
|
|
|
|
|
|
<p class=parameters>
|
|
|
|
<tt>Chunk</tt> contains the current chunk of data.
|
|
|
|
When the transmission is over, the function is called with an
|
2004-01-19 06:41:30 +01:00
|
|
|
empty string (i.e. <tt>""</tt>) as the <tt>chunk</tt>.
|
2004-01-24 03:47:24 +01:00
|
|
|
If an error occurs, the function receives <b><tt>nil</tt></b>
|
2004-01-19 06:41:30 +01:00
|
|
|
as <tt>chunk</tt> and an error message in <tt>err</tt>.
|
2003-08-31 03:00:15 +02:00
|
|
|
</p>
|
|
|
|
|
|
|
|
<p class=return>
|
2004-01-24 03:47:24 +01:00
|
|
|
The callback can abort transmission by returning <b><tt>nil</tt></b> as its first
|
2004-01-19 06:41:30 +01:00
|
|
|
return value, and an optional error message as the
|
|
|
|
second return value. If the application wants to continue receiving
|
2004-01-24 03:47:24 +01:00
|
|
|
data, the function should return non-<b><tt>nil</tt></b> as it's first return
|
2004-01-19 06:41:30 +01:00
|
|
|
value. In this case, the function can optionally return a
|
|
|
|
new callback function, to replace itself, as the second return value.
|
|
|
|
</p>
|
|
|
|
|
|
|
|
<p class=note>
|
|
|
|
Note: The <tt>callback</tt> module provides several standard receive callbacks, including the following:
|
2003-08-31 03:00:15 +02:00
|
|
|
</p>
|
|
|
|
|
|
|
|
<pre class=example>
|
2004-01-19 06:41:30 +01:00
|
|
|
function receive.concat(concat)
|
2003-08-31 03:00:15 +02:00
|
|
|
concat = concat or socket.concat.create()
|
|
|
|
local callback = function(chunk, err)
|
|
|
|
-- if not finished, add chunk
|
|
|
|
if chunk and chunk ~= "" then
|
|
|
|
concat:addstring(chunk)
|
|
|
|
return 1
|
|
|
|
end
|
|
|
|
end
|
|
|
|
return callback, concat
|
|
|
|
end
|
|
|
|
</pre>
|
|
|
|
|
2004-01-19 06:41:30 +01:00
|
|
|
<p class=note>
|
|
|
|
This function creates a new receive callback that concatenates all
|
|
|
|
received chunks into a the same concat object, which can later be
|
|
|
|
queried for its contents.
|
|
|
|
</p>
|
|
|
|
|
2003-08-31 03:00:15 +02:00
|
|
|
<!-- send_cb ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
|
|
|
|
|
|
|
|
<p class=name>
|
|
|
|
<b>send_cb()</b>
|
|
|
|
</p>
|
|
|
|
|
|
|
|
<p class=description>
|
|
|
|
The callback provided by the user will be repeatedly called whenever the
|
|
|
|
library needs more data to be sent.
|
|
|
|
</p>
|
|
|
|
|
|
|
|
<p class=return>
|
2004-01-19 06:41:30 +01:00
|
|
|
Each time the callback is called, it should return the next chunk of data. It
|
|
|
|
can optionally return, as it's second return value, a new callback to replace
|
|
|
|
itself. The callback can abort the process at any time by returning
|
2004-01-24 03:47:24 +01:00
|
|
|
<b><tt>nil</tt></b> followed by an optional error message.
|
2003-08-31 03:00:15 +02:00
|
|
|
</p>
|
|
|
|
|
|
|
|
<p class=note>
|
2004-01-19 06:41:30 +01:00
|
|
|
Note: Below is the implementation of the <tt>callback.send.file</tt>
|
|
|
|
function. Given an open file handle, it returns a send callback that will send the contents of that file, chunk by chunk.
|
2003-08-31 03:00:15 +02:00
|
|
|
</p>
|
|
|
|
|
|
|
|
<pre class=example>
|
2004-01-19 06:41:30 +01:00
|
|
|
function send.file(file, io_err)
|
|
|
|
-- if successful, return the callback that reads from the file
|
2003-08-31 03:00:15 +02:00
|
|
|
if file then
|
2004-01-19 06:41:30 +01:00
|
|
|
return function()
|
2003-08-31 03:00:15 +02:00
|
|
|
-- send next block of data
|
2004-01-19 06:41:30 +01:00
|
|
|
return (file:read(BLOCKSIZE)) or ""
|
2003-08-31 03:00:15 +02:00
|
|
|
end
|
|
|
|
-- else, return a callback that just aborts the transfer
|
2004-01-19 06:41:30 +01:00
|
|
|
else return fail(io_err or "unable to open file") end
|
2003-08-31 03:00:15 +02:00
|
|
|
end
|
|
|
|
</pre>
|
|
|
|
|
|
|
|
<!-- footer +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
|
|
|
|
|
|
|
|
<div class=footer>
|
|
|
|
<hr>
|
|
|
|
<center>
|
|
|
|
<p class=bar>
|
|
|
|
<a href="home.html">home</a> ·
|
|
|
|
<a href="home.html#down">download</a> ·
|
|
|
|
<a href="introduction.html">introduction</a> ·
|
|
|
|
<a href="reference.html">reference</a>
|
|
|
|
</p>
|
|
|
|
<p>
|
|
|
|
<small>
|
|
|
|
Last modified by Diego Nehab on <br>
|
|
|
|
Sat Aug 9 01:00:41 PDT 2003
|
|
|
|
</small>
|
|
|
|
</p>
|
|
|
|
</center>
|
|
|
|
</div>
|
|
|
|
|
|
|
|
</body>
|
|
|
|
</html>
|