Environment Information

Provide at least:

• JRuby version (jruby -v) and command line: jruby 9.2.16.0 (2.5.7) 2021-03-03 f82228dc32 OpenJDK 64-Bit Server VM 25.275-b01 on 1.8.0_275-b01 +jit [linux-x86_64]
• Operating system and platform (e.g. uname -a): Linux noblesse 5.4.80-gentoo-r1 #1 SMP Tue Dec 8 10:34:59 MSK 2020 x86_64 AMD Ryzen 7 3700X 8-Core Processor AuthenticAMD GNU/Linux

Way to reproduce

1. Download attached data.gz
2. Run ruby -e "require 'zlib'; f = File.read('data.gz'); puts Zlib::Inflate.inflate(f).bytesize" in the directory where you saved data.gz with different Ruby implementations

Expected Behavior

Uncompressed data size is 60992 bytes. This is what MRI says and what I actually expect.

$ zlib-flate -uncompress < data.gz > data && ls -l data agrees that uncompressed data is 60992 bytes.

$ openssl zlib -d < data.gz > data && ls -l data also thinks that uncompressed data is 60992 bytes.

$ python3 -c "import zlib; print(len(zlib.decompress(open('data.gz', 'rb').read())))" also thinks that uncompressed data is 60992 bytes.

Java also agrees data is 60992 bytes:

  public static void main(String[] args) throws Exception {
    byte[] input = Files.readAllBytes(Path.of("data.gz"));
    Inflater inflater = new Inflater();
    inflater.setInput(input);

    ByteArrayOutputStream output = new ByteArrayOutputStream();
    byte[] buffer = new byte[1024];

    while (!inflater.finished()) {
      int len = inflater.inflate(buffer);
      output.write(buffer, 0, len);
    }
    System.out.println(output.toByteArray().length); // prints 60992
  }

Actual Behavior

Uncompressed data size is 60994 bytes on JRuby. I observe this on JRuby 9.2.13 and 9.2.16. I didn't test other JRuby versions.