Add a decoder for bencode

1 files changed, 80 insertions, 0 deletions

diff --git a/plugins/bencode.lua b/plugins/bencode.lua
new file mode 100644
index 0000000..8a704fd
--- /dev/null
+++ b/plugins/bencode.lua
@@ -0,0 +1,80 @@
+--
+-- bencode.lua: BitTorrent data encoding
+--
+-- Copyright (c) 2017, Přemysl Janouch <p.janouch@gmail.com>
+--
+-- Permission to use, copy, modify, and/or distribute this software for any
+-- purpose with or without fee is hereby granted, provided that the above
+-- copyright notice and this permission notice appear in all copies.
+--
+-- THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+-- WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+-- MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+-- SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+-- WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+-- OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+-- CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+--
+
+local detect = function (c)
+	-- There is no magic to go by
+	return false
+end
+
+-- We're not making it exactly readable but at least we're trying
+local function one_value (c, level)
+	local p, type = c.position, c:read (1)
+	if type == "e" then
+		c (p, c.position -1):mark ("%d: container end", level - 1)
+		return false
+	elseif type == "i" then
+		local n = ""
+		type = c:read (1)
+		while type ~= "e" do
+			n = n .. type
+			type = c:read (1)
+		end
+		c (p, c.position - 1):mark ("%d: integer: %s", level, n)
+	elseif type == "l" then
+		c (p, p):mark ("%d: list begin", level)
+		local i = 0
+		while true do
+			local p = c.position
+			if not one_value (c, level + 1) then break end
+			c (p, c.position - 1):mark ("%d: list value %d", level, i)
+			i = i + 1
+		end
+	elseif type == "d" then
+		c (p, p):mark ("%d: dictionary begin", level)
+		while true do
+			local p = c.position
+			if not one_value (c, level + 1) then break end
+			c (p, c.position - 1):mark ("%d: dictionary key", level)
+
+			local p = c.position
+			if not one_value (c, level + 1) then break end
+			c (p, c.position - 1):mark ("%d: dictionary value", level)
+		end
+	else
+		local n = type
+		type = c:read (1)
+		while type ~= ":" do
+			n = n .. type
+			type = c:read (1)
+		end
+		c (p, c.position - 1):mark ("%d: string length: %s", level, n)
+
+		p = c.position
+		c:read (tonumber (n))
+		c (p, c.position - 1):mark ("%d: string value", level)
+	end
+	return true
+end
+
+local decode = function (c)
+	while not c.eof do
+		one_value (c, 0)
+	end
+end
+
+hex.register { type="bencode", detect=detect, decode=decode }