plugins/compression.lua

-- Copyright (C) 2009-2010 Matthew Wild

-- Copyright (C) 2009-2010 Tobias Markmann

--

-- This project is MIT/X11 licensed. Please see the

-- COPYING file in the source package for more information.

--

local verse = require "verse";

local zlib = require "zlib";

local xmlns_compression_feature = "http://jabber.org/features/compress"

local xmlns_compression_protocol = "http://jabber.org/protocol/compress"

local xmlns_stream = "http://etherx.jabber.org/streams";

local compression_level = 9;

-- returns either nil or a fully functional ready to use inflate stream

local function get_deflate_stream(session)

	local status, deflate_stream = pcall(zlib.deflate, compression_level);

	if status == false then

		local error_st = verse.stanza("failure", {xmlns=xmlns_compression_protocol}):tag("setup-failed");

		session:send(error_st);

		session:error("Failed to create zlib.deflate filter: %s", tostring(deflate_stream));

		return

	end

	return deflate_stream

end

-- returns either nil or a fully functional ready to use inflate stream

local function get_inflate_stream(session)

	local status, inflate_stream = pcall(zlib.inflate);

	if status == false then

		local error_st = verse.stanza("failure", {xmlns=xmlns_compression_protocol}):tag("setup-failed");

		session:send(error_st);

		session:error("Failed to create zlib.inflate filter: %s", tostring(inflate_stream));

		return

	end

	return inflate_stream

end

-- setup compression for a stream

local function setup_compression(session, deflate_stream)

	function session:send(t)

			--TODO: Better code injection in the sending process

			local status, compressed, eof = pcall(deflate_stream, tostring(t), 'sync');

			if status == false then

				session:close({

					condition = "undefined-condition";

					text = compressed;

					extra = verse.stanza("failure", {xmlns=xmlns_compression_protocol}):tag("processing-failed");

				});

				session:warn("Compressed send failed: %s", tostring(compressed));

				return;

			end

			session.conn:write(compressed);

		end;

end

-- setup decompression for a stream

local function setup_decompression(session, inflate_stream)

	local old_data = session.data

	session.data = function(conn, data)

			session:debug("Decompressing data...");

			local status, decompressed, eof = pcall(inflate_stream, data);

			if status == false then

				session:close({

					condition = "undefined-condition";

					text = decompressed;

					extra = verse.stanza("failure", {xmlns=xmlns_compression_protocol}):tag("processing-failed");

				});

				stream:warn("%s", tostring(decompressed));

				return;

			end

			return old_data(conn, decompressed);

		end;

end

function verse.plugins.compression(stream)

	local function handle_features(features)

		if not stream.compressed then

			-- does remote server support compression?

			local comp_st = features:child_with_name("compression");

			if comp_st then

				-- do we support the mechanism

				for a in comp_st:children() do

					local algorithm = a[1]

					if algorithm == "zlib" then

						stream:send(verse.stanza("compress", {xmlns=xmlns_compression_protocol}):tag("method"):text("zlib"))

						stream:debug("Enabled compression using zlib.")

						return true;

					end

				end

				session:debug("Remote server supports no compression algorithm we support.")

			end

		end

	end

	local function handle_compressed(stanza)

		if stanza.name == "compressed" then

			stream:debug("Activating compression...")

			-- create deflate and inflate streams

			local deflate_stream = get_deflate_stream(stream);

			if not deflate_stream then return end

			local inflate_stream = get_inflate_stream(stream);

			if not inflate_stream then return end

			-- setup compression for stream.w

			setup_compression(stream, deflate_stream);

			-- setup decompression for stream.data

			setup_decompression(stream, inflate_stream);

			stream.compressed = true;

			stream:reopen();

		elseif stanza.name == "failure" then

			stream:warn("Failed to establish compression");

		end

	end

	stream:hook("stream-features", handle_features, 250);

	stream:hook("stream/"..xmlns_compression_protocol, handle_compressed);

end