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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <meta name="description" content="LuaSocket: LTN12 support"> <meta name="keywords" content="Lua, LuaSocket, Filters, Source, Sink, Pump, Support, Library"> <title>LuaSocket: LTN12 module</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 width="128" height="128" 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="index.html">home</a> · <a href="index.html#download">download</a> · <a href="installation.html">installation</a> · <a href="introduction.html">introduction</a> · <a href="reference.html">reference</a> </p> </center> <hr> </div> <!-- ltn12 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <h2 id="ltn12">LTN12</h2> <p> The <tt>ltn12</tt> namespace implements the ideas described in <a href="http://lua-users.org/wiki/FiltersSourcesAndSinks"> LTN012, Filters sources and sinks</a>. This manual simply describes the functions. Please refer to the LTN for a deeper explanation of the functionality provided by this module. </p> <p> To obtain the <tt>ltn12</tt> namespace, run: </p> <pre class="example"> -- loads the LTN21 module local ltn12 = require("ltn12") </pre> <!-- filters ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <h3 id="filter">Filters</h3> <!-- chain ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <p class="name" id="filter.chain"> ltn12.filter.<b>chain(</b>filter<sub>1</sub>, filter<sub>2</sub> [, ... filter<sub>N</sub>]<b>)</b> </p> <p class="description"> Returns a filter that passes all data it receives through each of a series of given filters. </p> <p class="parameters"> <tt>Filter<sub>1</sub></tt> to <tt>filter<sub>N</sub></tt> are simple filters. </p> <p class="return"> The function returns the chained filter. </p> <p class="note"> The nesting of filters can be arbitrary. For instance, the useless filter below doesn't do anything but return the data that was passed to it, unaltered. </p> <pre class="example"> -- load required modules local ltn12 = require("ltn12") local mime = require("mime") -- create a silly identity filter id = ltn12.filter.chain( mime.encode("quoted-printable"), mime.encode("base64"), mime.decode("base64"), mime.decode("quoted-printable") ) </pre> <!-- cycle ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <p class="name" id="filter.cycle"> ltn12.filter.<b>cycle(</b>low [, ctx, extra]<b>)</b> </p> <p class="description"> Returns a high-level filter that cycles though a low-level filter by passing it each chunk and updating a context between calls. </p> <p class="parameters"> <tt>Low</tt> is the low-level filter to be cycled, <tt>ctx</tt> is the initial context and <tt>extra</tt> is any extra argument the low-level filter might take. </p> <p class="return"> The function returns the high-level filter. </p> <pre class="example"> -- load the ltn12 module local ltn12 = require("ltn12") -- the base64 mime filter factory encodet['base64'] = function() return ltn12.filter.cycle(b64, "") end </pre> <!-- pumps ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <h3 id="pump">Pumps</h3> <!-- all ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <p class="name" id="pump.all"> ltn12.pump.<b>all(</b>source, sink<b>)</b> </p> <p class="description"> Pumps <em>all</em> data from a <tt>source</tt> to a <tt>sink</tt>. </p> <p class="return"> If successful, the function returns a value that evaluates to <b><tt>true</tt></b>. In case of error, the function returns a <b><tt>false</tt></b> value, followed by an error message. </p> <!-- step +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <p class="name" id="pump.step"> ltn12.pump.<b>step(</b>source, sink<b>)</b> </p> <p class="description"> Pumps <em>one</em> chunk of data from a <tt>source</tt> to a <tt>sink</tt>. </p> <p class="return"> If successful, the function returns a value that evaluates to <b><tt>true</tt></b>. In case of error, the function returns a <b><tt>false</tt></b> value, followed by an error message. </p> <!-- sinks ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <h3 id="sink">Sinks</h3> <!-- chain ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <p class="name" id="sink.chain"> ltn12.sink.<b>chain(</b>filter, sink<b>)</b> </p> <p class="description"> Creates and returns a new sink that passes data through a <tt>filter</tt> before sending it to a given <tt>sink</tt>. </p> <!-- error ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <p class="name" id="sink.error"> ltn12.sink.<b>error(</b>message<b>)</b> </p> <p class="description"> Creates and returns a sink that aborts transmission with the error <tt>message</tt>. </p> <!-- file +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <p class="name" id="sink.file"> ltn12.sink.<b>file(</b>handle, message<b>)</b> </p> <p class="description"> Creates a sink that sends data to a file. </p> <p class="parameters"> <tt>Handle</tt> is a file handle. If <tt>handle</tt> is <tt><b>nil</b></tt>, <tt>message</tt> should give the reason for failure. </p> <p class="return"> The function returns a sink that sends all data to the given <tt>handle</tt> and closes the file when done, or a sink that aborts the transmission with the error <tt>message</tt> </p> <p class="note"> In the following example, notice how the prototype is designed to fit nicely with the <tt>io.open</tt> function. </p> <pre class="example"> -- load the ltn12 module local ltn12 = require("ltn12") -- copy a file ltn12.pump.all( ltn12.source.file(io.open("original.png", "rb")), ltn12.sink.file(io.open("copy.png", "wb")) ) </pre> <!-- null +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <p class="name" id="sink.null"> ltn12.sink.<b>null()</b> </p> <p class="description"> Returns a sink that ignores all data it receives. </p> <!-- simplify +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <p class="name" id="sink.simplify"> ltn12.sink.<b>simplify(</b>sink<b>)</b> </p> <p class="description"> Creates and returns a simple sink given a fancy <tt>sink</tt>. </p> <!-- table ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <p class="name" id="sink.table"> ltn12.sink.<b>table(</b>[table]<b>)</b> </p> <p class="description"> Creates a sink that stores all chunks in a table. The chunks can later be efficiently concatenated into a single string. </p> <p class="parameters"> <tt>Table</tt> is used to hold the chunks. If <tt><b>nil</b></tt>, the function creates its own table. </p> <p class="return"> The function returns the sink and the table used to store the chunks. </p> <pre class="example"> -- load needed modules local http = require("socket.http") local ltn12 = require("ltn12") -- a simplified http.get function function http.get(u) local t = {} local respt = request{ url = u, sink = ltn12.sink.table(t) } return table.concat(t), respt.headers, respt.code end </pre> <!-- sinks ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <h3 id="source">Sources</h3> <!-- cat ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <p class="name" id="source.cat"> ltn12.source.<b>cat(</b>source<sub>1</sub> [, source<sub>2</sub>, ..., source<sub>N</sub>]<b>)</b> </p> <p class="description"> Creates a new source that produces the concatenation of the data produced by a number of sources. </p> <p class="parameters"> <tt>Source<sub>1</sub></tt> to <tt>source<sub>N</sub></tt> are the original sources. </p> <p class="return"> The function returns the new source. </p> <!-- chain ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <p class="name" id="source.chain"> ltn12.source.<b>chain(</b>source, filter<b>)</b> </p> <p class="description"> Creates a new <tt>source</tt> that passes data through a <tt>filter</tt> before returning it. </p> <p class="return"> The function returns the new source. </p> <!-- empty ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <p class="name" id="source.empty"> ltn12.source.<b>empty()</b> </p> <p class="description"> Creates and returns an empty source. </p> <!-- error ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <p class="name" id="source.error"> ltn12.source.<b>error(</b>message<b>)</b> </p> <p class="description"> Creates and returns a source that aborts transmission with the error <tt>message</tt>. </p> <!-- file +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <p class="name" id="source.file"> ltn12.source.<b>file(</b>handle, message<b>)</b> </p> <p class="description"> Creates a source that produces the contents of a file. </p> <p class="parameters"> <tt>Handle</tt> is a file handle. If <tt>handle</tt> is <tt><b>nil</b></tt>, <tt>message</tt> should give the reason for failure. </p> <p class="return"> The function returns a source that reads chunks of data from given <tt>handle</tt> and returns it to the user, closing the file when done, or a source that aborts the transmission with the error <tt>message</tt> </p> <p class="note"> In the following example, notice how the prototype is designed to fit nicely with the <tt>io.open</tt> function. </p> <pre class="example"> -- load the ltn12 module local ltn12 = require("ltn12") -- copy a file ltn12.pump.all( ltn12.source.file(io.open("original.png", "rb")), ltn12.sink.file(io.open("copy.png", "wb")) ) </pre> <!-- simplify +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <p class="name" id="source.simplify"> ltn12.source.<b>simplify(</b>source<b>)</b> </p> <p class="description"> Creates and returns a simple source given a fancy <tt>source</tt>. </p> <!-- string +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <p class="name" id="source.string"> ltn12.source.<b>string(</b>string<b>)</b> </p> <p class="description"> Creates and returns a source that produces the contents of a <tt>string</tt>, chunk by chunk. </p> <!-- table +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <p class="name" id="source.table"> ltn12.source.<b>table(</b>table<b>)</b> </p> <p class="description"> Creates and returns a source that produces the numerically-indexed values of a <tt>table</tt> successively beginning at 1. The source returns nil (end-of-stream) whenever a nil value is produced by the current index, which proceeds forward regardless. </p> <!-- footer +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <div class="footer"> <hr> <center> <p class="bar"> <a href="index.html">home</a> · <a href="index.html#down">download</a> · <a href="installation.html">installation</a> · <a href="introduction.html">introduction</a> · <a href="reference.html">reference</a> </p> <p> <small> Last modified by Diego Nehab on <br> Thu Apr 20 00:25:41 EDT 2006 </small> </p> </center> </div> </body> </html>