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OTNetstring

Similar to Tagged Netstrings, but optimized for streaming.

What changed: The type info is not at the end of the encoded data, but at the beginning, right after the size info. That way nested objects can be created while reading from the stream. Therefore it is rather similar to Bencode, plus the Netstring advantage of always knowing how many bytes to read.

Objects look like this:

Ruby            TNetstring      OTNetstring     Bencode

42              2:42#           2#42            i42e
"hi"            2:hi,           2,hi            2:hi
true            4:true!         4!true          (not possible)
[1]             4:1:1#}         3[1#1           li1ee
{"a" => "b"}    8:1:a,=1:b,}    6{1,a1,b        d1:a1:be

Similar implementations (both pure ruby, using recursion for nested objects) show the performance difference, esp. when simulating network IO:

                                                          user     system      total        real
TNetstring: simple objects                            0.000000   0.000000   0.000000 (  0.000160)
OTNetstring: simple objects                           0.000000   0.000000   0.000000 (  0.000166)*
TNetstring: long string                               0.130000   0.050000   0.180000 (  0.186946)
OTNetstring: long string                              0.050000   0.000000   0.050000 (  0.047778)
TNetstring: flat arrays                               2.280000   2.940000   5.220000 (  5.432791)
OTNetstring: flat arrays                              0.470000   0.010000   0.480000 (  0.484575)
TNetstring: complex nesting                           4.310000   3.100000   7.410000 (  7.562399)
OTNetstring: complex nesting                          1.940000   0.010000   1.950000 (  1.943385)
TNetstring: with remainder                            0.300000   0.250000   0.550000 (  0.574956)
OTNetstring: with remainder                           0.080000   0.080000   0.160000 (  0.152838)
TNetstring: streaming (3 GBit/sec)                    2.160000   3.010000   5.170000 (  5.180267)
OTNetstring: streaming (3 GBit/sec)                   0.860000   0.050000   0.910000 (  0.917463)
TNetstring: streaming (3 GBit/sec), with remainder    0.490000   0.360000   0.850000 (  4.836673)
OTNetstring: streaming (3 GBit/sec), with remainder   0.080000   0.070000   0.150000 (  0.148301)

* this is (insignificantly) slower, since OTNetstring wraps each String in a StringIO

API is identical to tnetstring-rb, except that you use OTNetstring instead of TNetstring and that parse also takes IO or IO-like objects as argument.

Running benchmarks

git submodule init
git submodule update
./bench.rb

Stuff to think about

  • If : would identify strings rather than , and each object would end with a ,, then Netstrings and TNetstring-Strings would be valid OTNetstring objects.
  • Representations of true and false could be shortened.