Xgit.Util.UnzipStream: No code coverage for zlib :continue case

[scouten]

• Add label: "bug"
• Add label: "good first issue" or "help wanted" if appropriate

Describe the Bug
In Xgit.Util.UnzipStream.process_all_data/3 the case where :zlib.safeInflate/2 returns {:continue, data} is not reachable by any test data I've been able to construct.

Steps to Reproduce
If I knew … 😉

[dbernheisel]

Haven't tested yet myself, but I think if you take the compressed binary, and splitt it into 2 parts and only throw the 1st part into :zlib.safeInflate/2 you should get the :continue response. This may also show itself if the file is larger than the initial-read buffer.

Here's an example:

# generate a random large file
$ dd if=/dev/urandom of=largefile.txt bs=1048576 count=10
$ gzip largefile.txt
# => largefile.txt.gz

defmodule Test do
  @windowbits 15 + 32 # automatically detect headers and deflate
  @stream_bytes 50
  def decompress(file) do
    z = :zlib.open()
    :zlib.inflateInit(z, @windowbits)
    binary = file |> File.stream!([], @stream_bytes) |> Enum.take(1000)
    loop(z, :zlib.safeInflate(z, binary))
  end
  
  def loop(z, {:continue, _incomplete_decompressed_binary}) do
    # wait in a holding pattern until we get more binary
    IO.puts "waiting for more data"
    loop(z, :zlib.safeInflate(z, []))
  end
  
  def loop(z, {:finished, decompressed_data}) do
    IO.puts "done"
    :zlib.close(z)
    decompressed_data
  end
end

Test.decompress("largefile.txt.gz")
#=> waiting for more data
#=> waiting for more data
#=> waiting for more data
#=> done
#=> [
  <<150, 228, 216, 236, 53, 47, 20, 62, 248, 185, 65, 227, 173, 63, 163, 31,
    248, 207, 252, 79, 134, 34, 193, 185, 23, 122, 23, 62, 250, 7, 241, 229,
    126, 251, 192, 135, 139, 173, 68, 132, 79, 67, 7, 250, 100, 252, 167, 228,
    245, ...>>
]

This may be a good place to start for understanding how to write a test to cover :continue

[scouten]

@dbernheisel thank you, that looks like a promising lead!

[scouten]

Confirmed. Fix coming soon. Thank you!

[scouten]

Closed by #104. Will be included in a new release soon.