Resume zstream if available [Bug #10961]

[wanabe]

I think zstream should resume when a signal is received but no exception is raised. I wanted to add tests, but it would consume too much time, so I decided to give up.

script bug10961.rb

require 'zlib'
Signal.trap("INT") { } if ARGV[0]
str = ("A".."z").to_a.join("") * 10_000
loop do
  str << str.dup
  spawn("ruby", "-e", <<~"end;", $$.to_s) # it must be out of GVL
    sleep 0.1
    begin
      Process.kill :INT, ARGV[0].to_i
    rescue Errno::ESRCH
    end
  end;
  t = Time.now
  Zlib::Deflate.deflate(str)
  s = Time.now - t
  puts "byte: %d, sec: %.4f" % [str.size, s]
  break if s > 0.5
end

trap without patch:

$ ruby -Ilib bug10961.rb trap
byte: 1160000, sec: 0.0070
byte: 2320000, sec: 0.0194
byte: 4640000, sec: 0.0393
byte: 9280000, sec: 0.0814
Traceback (most recent call last):
    3: from bug10961.rb:4:in `<main>'
    2: from bug10961.rb:4:in `loop'
    1: from bug10961.rb:14:in `block in <main>'
bug10961.rb:14:in `deflate': data error (Zlib::DataError)

with patch:

$ ruby -Ilib bug10961.rb trap
byte: 1160000, sec: 0.0061
byte: 2320000, sec: 0.0200
byte: 4640000, sec: 0.0389
byte: 9280000, sec: 0.0690
byte: 18560000, sec: 0.1063
byte: 37120000, sec: 0.2201
byte: 74240000, sec: 0.3873
byte: 148480000, sec: 0.7742

And the results are same when it is not trapped. notrap without patch:

$ ruby -Ilib bug10961.rb
byte: 1160000, sec: 0.0060
byte: 2320000, sec: 0.0170
byte: 4640000, sec: 0.0378
byte: 9280000, sec: 0.0849
Traceback (most recent call last):
    3: from bug10961.rb:4:in `<main>'
    2: from bug10961.rb:4:in `loop'
    1: from bug10961.rb:14:in `block in <main>'
bug10961.rb:14:in `deflate': Interrupt
    3: from bug10961.rb:4:in `<main>'
    2: from bug10961.rb:4:in `loop'
    1: from bug10961.rb:14:in `block in <main>'
bug10961.rb:14:in `deflate': data error (Zlib::DataError)
bug10961.rb: Interrupt

notrap with patch:

$ ruby -Ilib bug10961.rb
byte: 1160000, sec: 0.0060
byte: 2320000, sec: 0.0198
byte: 4640000, sec: 0.0430
byte: 9280000, sec: 0.0786
Traceback (most recent call last):
    3: from bug10961.rb:4:in `<main>'
    2: from bug10961.rb:4:in `loop'
    1: from bug10961.rb:14:in `block in <main>'
bug10961.rb:14:in `deflate': Interrupt
    3: from bug10961.rb:4:in `<main>'
    2: from bug10961.rb:4:in `loop'
    1: from bug10961.rb:14:in `block in <main>'
bug10961.rb:14:in `deflate': data error (Zlib::DataError)

[wanabe]

Thank you to review! I'll merge it with "Rebase and merge" button.

[jorgemanrubia]

Hi @jeremyevans and @wanabe , any chance you could push a new rubygem version with this patch?

[jeremyevans]

I haven't handled a zlib gem release, I think @hsbt handles them. I have no problems with a release, but it would be up to him. It appears the last gem release was before Ruby 2.7.