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module BERT
class Encode
include Types
attr_accessor :out
def initialize(out)
self.out = out
end
def self.encode(data)
io = StringIO.new
io.set_encoding('binary') if io.respond_to?(:set_encoding)
self.new(io).write_any(data)
io.string
end
def write_any obj
write_1 MAGIC
write_any_raw obj
end
def write_any_raw obj
case obj
when Symbol then write_symbol(obj)
when Integer then write_fixnum(obj)
when Float then write_float(obj)
when Tuple then write_tuple(obj)
when Array then write_list(obj)
when String then write_binary(obj)
else
fail(obj)
end
end
def write_1(byte)
out.write([byte].pack("C"))
end
def write_2(short)
out.write([short].pack("n"))
end
def write_4(long)
out.write([long].pack("N"))
end
def write_string(string)
out.write(string)
end
def write_boolean(bool)
write_symbol(bool.to_s.to_sym)
end
def write_symbol(sym)
fail(sym) unless sym.is_a?(Symbol)
data = sym.to_s
write_1 ATOM
write_2 data.bytesize
write_string data
end
def write_fixnum(num)
if num >= 0 && num < 256
write_1 SMALL_INT
write_1 num
elsif num <= MAX_INT && num >= MIN_INT
write_1 INT
write_4 num
else
write_bignum num
end
end
def write_float(float)
write_1 FLOAT
write_string format("%15.15e", float).ljust(31, "\000")
end
def write_bignum(num)
n = (num.abs.to_s(2).size / 8.0).ceil
if n < 256
write_1 SMALL_BIGNUM
write_1 n
write_bignum_guts(num)
else
write_1 LARGE_BIGNUM
write_4 n
write_bignum_guts(num)
end
end
def write_bignum_guts(num)
write_1 (num >= 0 ? 0 : 1)
num = num.abs
while num != 0
rem = num % 256
write_1 rem
num = num >> 8
end
end
def write_tuple(data)
fail(data) unless data.is_a? Array
if data.length < 256
write_1 SMALL_TUPLE
write_1 data.length
else
write_1 LARGE_TUPLE
write_4 data.length
end
data.each { |e| write_any_raw e }
end
def write_list(data)
fail(data) unless data.is_a? Array
write_1 NIL and return if data.empty?
write_1 LIST
write_4 data.length
data.each{|e| write_any_raw e }
write_1 NIL
end
def write_binary(data)
write_1 BIN
write_4 data.bytesize
write_string data
end
private
def fail(obj)
raise "Cannot encode to erlang external format: #{obj.inspect}"
end
end
end
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