assignment to Java::byte[] creates range error for values greater than 127

I'm on the fence about this one. For the other types, we also throw a hard error if the incoming value is outside the signed range of the target. This is sometimes a hassle, but if we tried to guess what to do we'd be wrong half the time.

In this case, however, we're talking about bytes, which are very commonly used in their unsigned form. Indeed, we return unsigned byte values from String and IO methods that return bytes, so not being able to stuff a signed Fixnum in the range 0..255 into an 8-bit Java byte is definitely problematic.

Perhaps the "right" way to do this would be to convert values in the range 128..255 to their signed bits equivalent and allow them through? I hate adding exceptions like this, but if it's not there it's a bit painful to pass a full range of 8-bit values to Java.

What do others think?

In the interim you could simply convert values in that range to their signed equivalent and it should work...

Perhaps adding to_jb to Fixnum would be a solution for both sides of the fence:

class Fixnum
  # to Java byte
  # takes a Ruby Fixnum and returns the value as signed byte range -128..128 (Java byte).
  # rasies RangeError
  def to_jb
     raise RangeError,"too big for Java byte: #{self}" if (self < -128 || self > 255) 
    if self > 127 then
       return self - 256
    else 
      return self
      end
  end
end

to_jb added to Fixnum
Also testcase works for both JRuby 1.5.6 and 1.6.0

I opted to add two methods to byte[] directly: ubyte_set and ubyte_get. They work pretty much like you'd expect:

ary = Java::byte[1].new
ary.ubyte_set(0, 0xFF)
ary.ubyte_get(0) # => 0xFF
ary[0] # => -1
ary[0] = 0xFF # => RangeError

Your option was certainly a reasonable one, but added the overhead of constructing an intermediate java.lang.Byte that also gets wrapped in a proxy object. The ubyte_set and ubyte_get options will still deal directly with Fixnum, and only have the overhead of Fixnum math and a bit of Ruby code.

If you see that the overhead is too much, we can look at implementing it native. Let us know (and probably file a separate bug).

commit 270179091a19063bdd88507cc3ee3d89da1c4127
Author: Charles Oliver Nutter <headius@headius.com>
Date: Thu Mar 31 20:12:45 2011 -0500

Fix JRUBY-5597: assignment to Java::byte[] creates range error for values greater than 127

• Add ubyte_set and ubyte_get to Java byte[] to allow setting and getting unsigned bytes.

I'm happy with your solution. It makes sense.