Feature #17851: ruby extension for memoryview

• Status: Open
• Assignee: -
• Target version: -

[dsisnero (Dominic Sisneros)]

add an extension to ruby for memoryview - (just like Fiddle::MemoryView but in ruby assuming Fiddle::MemoryView gets slices)
add a method in Kernel to get initialize a memoryview on an object that is a c memoryview

lets say we want to partially copy a file - minus the first KB

f = File.open('test.txt', 'rb') do |f|
  content = f.read
  content_to_write = memoryview(content)[1024..-1]   # here is what I want new -it will use the same memory as content just pointers
  puts "content length #{content.size} - content_to_write length #{content_to_write.size}"
  File.open('output.txt','wb') do |f2|
     f2.write(content_to_write)                      # if we have #17832 this will write to file without copying 
  end
end

If we have memoryview extension in ruby we can use less memory because we are no longer copying Strings when doing slices
#17831

[jeremyevans0 (Jeremy Evans)]

• Tracker changed from Bug to Feature
• Backport deleted (2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN)

[Eregon (Benoit Daloze)]

I think Fiddle::MemoryView is not needed for this.
String#[] can already avoid copying, on CRuby I think only if taking a substring until the end (the case here).

Also if Fiddle::MemoryView returns a mutable/non-read-only view, it seems very difficult to support while not making a copy and keeping the Ruby String working.

Finally, a method on Kernel is most likely not acceptable, we'd want a proper namespace like on Fiddle::MemoryView or so.

[Eregon (Benoit Daloze)]

• Related to Feature #17831: add slice method to Fiddle::MemoryView added