[armedbear-devel] is there a good method to read/write java byte arrays?

[Alessio Stalla]

On Wed, Mar 17, 2010 at 8:10 PM, David Kirkman <dkirkman at ucsd.edu> wrote:
> On Wed, Mar 17, 2010 at 11:51 AM, Alessio Stalla
> <alessiostalla at gmail.com> wrote:
>> On Wed, Mar 17, 2010 at 7:36 PM, David Kirkman <dkirkman at ucsd.edu> wrote:
>>> On Wed, Mar 17, 2010 at 9:55 AM, Alessio Stalla <alessiostalla at gmail.com> wrote:
>>>> On Wed, Mar 17, 2010 at 5:32 PM, Alessio Stalla <alessiostalla at gmail.com> wrote:
>>>>> On Wed, Mar 17, 2010 at 5:22 PM, Mark Evenson <evenson at panix.com> wrote:
>>>>>> On 3/17/10 5:04 PM, Alessio Stalla wrote:
>>>>>> […]
>>>>>>
>>>>>>> I wrote sys::%make-byte-array-output-stream in order to make the
>>>>>>> runtime compiler capable of generating bytecode without using
>>>>>>> temporary files; it wasn't meant to be used by the ABCL user, and as
>>>>>>> such it's not very polished (for example, the type of a
>>>>>>> byte-array-output-stream is simply STREAM). In any case, it's defined
>>>>>>> in the ByteArrayOutputStream Java class, and as you correctly noted,
>>>>>>> it explicitly sets the element type to (unsigned-byte 8). As a quick
>>>>>>> and dirty solution, you could more or less copy-paste that class and
>>>>>>> replace "output" with "input" :) (as well as update Autoload.java to
>>>>>>> make ABCL know of the new primitives).
>>>>>>>
>>>>>>> We should probably polish it a bit and release it as an extension.
>>>>>>
>>>>>> Well, at least we should quickly  whip out the inverse version so David
>>>>>> doesn't have to rely on hacking Stream.java (although I'm not sure when
>>>>>> telling Stream that initAsBinaryStream() means a format of unsigned 8bit
>>>>>> bytes will fail).
>>>>>>
>>>>>> I think we can commit to the interface you've implemented in
>>>>>> ByteArrayOutputStream, as those are the basic necessary operations.
>>>>>>
>>>>>> Or maybe I am not seeing what potential problems there would be with
>>>>>> this as a short-term strategy, Alessio?
>>>>>
>>>>> No problem at all in the implementation per se; however, when we'll
>>>>> make it an "official" extension, the interface will change (if
>>>>> anything, symbols won't probably be in sys anymore and they won't be
>>>>> prefixed with %). Since this functionality will have approximately 1
>>>>> user in the near future :), I think it's ok to commit a quick fix for
>>>>> David. I'm working on it right now.
>>>>
>>>> Committed as r12557.
>>>>
>>>> A.
>>>>
>>>
>>> Thanks for implementing the inverse function so quickly!
>>>
>>> I ended up doing a bit more hacking last night.  When I tried to serialize
>>> structures that contain raw java objects, I realized that I need a way to
>>> convert lisp streams into java streams so that I can use the java
>>> serialization system.   I ended up writing:
>>>
>>>  public static OutputStream
>>>    outputStreamFromABCLStream(final LispObject stream) {
>>>
>>>    if (stream instanceof org.armedbear.lisp.Stream) {
>>>      return new OutputStream() {
>>>        public void write(int b) {
>>>          ((org.armedbear.lisp.Stream) stream)._writeByte(b);
>>>        }
>>>      };
>>>    } else {
>>>      throw new RuntimeException("argument not an abcl stream");
>>>    }
>>>  }
>>>
>>> and another version for InputStream.  Should something like these
>>> also go in as primitives?
>>
>> For binary input/output streams only, I think accessing the Java
>> streams wrapped by the Lisp stream is a better solution: no extra
>> objects are allocated and no API mismatch is possible. Unfortunately
>> those are private fields right now, but a couple of getters are not
>> hard to add ;)
>>
>> so, your outputStreamFromABCLStream would become:
>>
>> public static OutputStream
>>  outputStreamFromABCLStream(final LispObject stream) {
>>
>>  if (stream instanceof org.armedbear.lisp.Stream) {
>>    return ((org.armedbear.lisp.Stream) stream).getOutputStream();
>>  } else {
>>    throw new RuntimeException("argument not an abcl stream");
>>  }
>> }
>>
>> or, if you don't mind getting a ClassCastException instead, simply
>>
>> public static OutputStream
>>  outputStreamFromABCLStream(final LispObject stream) {
>>  return ((org.armedbear.lisp.Stream) stream).getOutputStream();
>> }
>>
>> what do you think?
>
> I think that's a much better solution!  I don't mind ClassCastExceptions, my
> code had that structure because it started as something copy/pasted out of
> Stream.java.  And I was using _readByte and _writeByte just because I didn't
> want to have to make changes to Stream.java and end up with my own version
> of abcl.

Ok. I committed the modified Stream with accessors for the underlying
Java streams.

Bye,
Alessio