rubyでBcodeを実現する方法

2014年6月24日

ファイル名：bencode.rb

参考コード下記：
class Bencode

def initialize
@ret = “"
end

public
def encode(x)
@ret = “"
encode_auto(x)
return @ret
end
private
def encode_auto(x)
case x.class.to_s
when “String": encode_string(x)
when “Fixnum": encode_int(x)
when “Hash" : encode_dict(x)
when “Array" : encode_list(x)
else
end
end

def encode_int(x)
@ret = @ret + “i" + x.to_s + “e"
end

def encode_bool(x)
if x then
encode_int(1)
else
encode_int(0)
end
end

def encode_string(x)
@ret = @ret + x.length.to_s + “:" + x
end

def encode_list(x)
@ret = @ret + “l"
x.each do |v|
encode_auto(v)
end
@ret = @ret + “e"
end

def encode_dict(x)
@ret = @ret + “d"
x.each do |k,v|
encode_string(k)
encode_auto(v)
end
@ret = @ret + “e"
end

end

class Bdecode
def decode(x)
@pos = 0
@x = x
return decode_auto()
end
def decode_auto()
if @x[@pos, 1] == “i" then
return decode_int()
elsif @x[@pos, 1] == “l" then
return decode_list()
elsif @x[@pos, 1] == “d" then
return decode_dict()
else
return decode_string()
end
end

def decode_int()
ret = 0
len = 0
if @x[@pos,1].eql?(“i") then
@pos = @pos + 1
while not @x[@pos + len, 1].eql?(“e") do
len = len + 1
end
ret = Integer(@x[@pos, len])
@pos = @pos + len + 1
end

return ret
end

def decode_string()
=begin
x = @x[@pos, @x.length – @pos]
len = x.split(“:")[0]
=end
len = 0
while len < (@x.length – @pos) and not @x[@pos + len, 1] == “:" do
len = len + 1
end
len = @x[@pos, len]
@pos = @pos + len.length + 1
len = Integer(len)
ret = @x[@pos, len]
@pos = @pos + len
return ret
end

def decode_list()
ret = Array.new
if @x[@pos, 1].eql?(“l") then
@pos = @pos + 1
while not @x[@pos, 1].eql?(“e") do
ret << decode_auto()
end
@pos = @pos + 1
end
return ret
end

def decode_dict()
ret = Hash.new
if @x[@pos, 1].eql?(“d") then
@pos = @pos + 1
while not @x[@pos, 1].eql?(“e") do
k = decode_string()
v = decode_auto()
ret[k] = v
end

end
@pos = @pos + 1
return ret

end
end
=begin

test = Bencode.new
x = {“t"=>"aa", “y"=>"e", “e"=>[201,"A Generic Error Ocurred"]}
ret = test.encode(x)
puts ret
test2 = Bdecode.new
ret = test2.decode(ret)
puts ret[“e"]
=end