Ruby » Ruby master

Bug #16285

Updated by alanwu (Alan Wu) over 4 years ago

Run the following script to observe the issue 
 ```ruby 
 require 'zlib' 

 def write_gzip_file(content, mtime) 
   File.open('archieve.gz', 'w') do |f| 
     gz = Zlib::GzipWriter.new(f) 
     gz.mtime = mtime 
     gz.write(content) 
     gz.close 
   end 
   system("file archieve.gz") 
 end 

 write_gzip_file("current time", 0) 
 write_gzip_file("one second from epoch", 1) 
 ``` 

 Output:  
 ``` 
 ruby 2.6.5p114 (2019-10-01 revision 67812) [x86_64-darwin18] 
 archieve.gz: gzip compressed data, last modified: Wed Oct 30 18:04:07 2019, from Unix, original size 12 
 archieve.gz: gzip compressed data, last modified: Thu Jan    1 00:00:01 1970, from Unix, original size 21 
 ``` 

 As you can see, setting mtime to 0 doesn't set the timestamp in the file header to be all zeros. 
 The documentation for `#mtime=` says: 

 > If you do not set an mtime, the default value will be the time when compression started. Setting a value of 0 indicates no time stamp is available. 

 which sounds like setting 0 should be a valid operation. valid.  

 I have a PR to fix this: https://github.com/ruby/zlib/pull/10

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