97 lines
3.2 KiB
Lua
97 lines
3.2 KiB
Lua
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-- Based on bencode.lua from the jeejah project by Phil Hagelberg
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-- Distributed under the MIT license
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-- https://gitlab.com/technomancy/jeejah/
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local encode, decode
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local function decode_list(str, t, total_len)
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-- print("list", str, lume.serialize(t))
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if #str == 0 then error("Incomplete") end
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if(str:sub(1,1) == "e") then return t, total_len + 1 end
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local value, v_len = decode(str)
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table.insert(t, value)
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total_len = total_len + v_len
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return decode_list(str:sub(v_len + 1), t, total_len)
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end
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local function decode_table(str, t, total_len)
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-- print("table", str, lume.serialize(t))
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if #str == 0 then error("Incomplete") end
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if(str:sub(1,1) == "e") then return t, total_len + 1 end
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local key, k_len = decode(str)
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local value, v_len = decode(str:sub(k_len+1))
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local end_pos = 1 + k_len + v_len
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t[key] = value
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total_len = total_len + k_len + v_len
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return decode_table(str:sub(end_pos), t, total_len)
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end
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function decode(str)
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-- print("decoding", str)
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if #str == 0 then
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error("Incomplete")
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elseif(str:sub(1,1) == "l") then
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return decode_list(str:sub(2), {}, 1)
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elseif(str:sub(1,1) == "d") then
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return decode_table(str:sub(2), {}, 1)
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elseif(str:sub(1,1) == "i") then
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local iend = str:find("e")
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if iend == nil then error("Incomplete") end
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return(tonumber(str:sub(2, iend - 1))), iend
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elseif(str:match("[0-9]+:")) then
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local num_str = str:match("[0-9]+")
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local beginning_of_string = #num_str + 2
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local str_len = tonumber(num_str)
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local total_len = beginning_of_string + str_len - 1
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if #str < total_len then error("Incomplete") end
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return str:sub(beginning_of_string, total_len), total_len
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else
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error("Could not parse "..str)
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end
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end
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local function encode_str(s) return #s .. ":" .. s end
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local function encode_int(n) return "i" .. tostring(n) .. "e" end
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local function encode_table(t)
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-- sort keys by encoded value as per bencode spec
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-- https://www.bittorrent.org/beps/bep_0003.html#bencoding
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-- we assume that sorting the concatenated key-value pairs will result in the same ordering as just the keys, since keys are unique
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-- even if this is untrue in some corner cases, the most important thing for our purposes is that the same table always results in the same encoding
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local encoded_kvs = {}
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for k,v in pairs(t) do table.insert(encoded_kvs, encode(k) .. encode(v)) end
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table.sort(encoded_kvs)
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table.insert(encoded_kvs, 1, "d")
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table.insert(encoded_kvs, "e")
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return table.concat(encoded_kvs)
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end
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local function encode_list(l)
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local s = "l"
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for _,x in ipairs(l) do s = s .. encode(x) end
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return s .. "e"
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end
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local function count(tbl)
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local i = 0
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for _ in pairs(tbl) do i = i + 1 end
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return i
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end
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function encode(x)
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local unpack = unpack or table.unpack
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if(type(x) == "table" and select("#", unpack(x)) == count(x)) then
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return encode_list(x)
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elseif(type(x) == "table") then
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return encode_table(x)
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elseif(type(x) == "number" and math.floor(x) == x) then
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return encode_int(x)
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elseif(type(x) == "string") then
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return encode_str(x)
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else
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error("Could not encode " .. type(x) .. ": " .. tostring(x))
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end
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end
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return {decode=decode, encode=encode}
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