[armedbear-devel] How to use JARRAY-SET to fill a byte array?

Chun Tian (binghe) binghe.lisp at gmail.com
Tue Sep 14 07:26:38 UTC 2010

Hi, Alessio

Thanks for your information.

I think, if you can make JARRAY-SET or (SETF JARRAY-REF) directly use Lisp (signed-byte 8) numbers, that will be better.

Beside, Java booleans has the same problem, I have to use (make-immediate-object t :boolean) and (make-immediate-object nil :boolean) to fill method arguments when they need "boolean". Why not let us just use T and NIL?


在 2010-9-14,15:08, Alessio Stalla 写道:

> On Tue, Sep 14, 2010 at 8:45 AM, Chun Tian (binghe)
> <binghe.lisp at gmail.com> wrote:
>> Hi again ... ABCL
>> I want to fill a Java byte[] array. But I don't know how to correctly use JARRAY-SET (I should use it, right?):
>> CL-USER(1): (defvar $*byte (jclass "byte"))
>> $*BYTE
>> CL-USER(2): (setf array (jnew-array $*byte 10))
>> #<jarray [B at 7a2ee7e5 {1D7AAA0E}>
>> CL-USER(3): (jarray-set array 1 0)
>> #<THREAD "interpreter" {6E61A414}>: Debugger invoked on condition of type JAVA-EXCEPTION
>>  Java exception 'java.lang.IllegalArgumentException: argument type mismatch'.
>> Restarts:
>>  0: TOP-LEVEL Return to top level.
>> [1] CL-USER(4): 0
>> CL-USER(5): (jarray-ref array 0)
>> 0
>> So, a plain number "1" cannot work, but what else I can do? a object of java.lang.Byte?
> You need to convert 1 to a Java byte... honestly I don't know if and
> how it can be done. Our fixnums are mapped to integers... we should
> probably extend jcoerce to handle numeric conversions as well. And
> conversion of numeric arrays, while we're at it.
>> And, is there any quick way I can fill a byte array using contents from a Lisp array?
> The unexported system::%make-byte-array-output-stream and
> system::%get-output-stream-bytes come to my mind... but still you'll
> have to loop over the Lisp array. If there are no objections from
> other devs, I'd rather extend jcoerce to support your use case.
> Cheers,
> Alessio
> PS you can use (setf (jarray-ref array index) value) instead of jarray-set.

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