RFR: 8245036: DataInputStream.readFully(byte[], int, int) does not throw expected IndexOutOfBoundsExceptions

Raffaello Giulietti raffaello.giulietti at gmail.com
Thu Aug 6 21:36:04 UTC 2020

Hi Brian,

the body of readFully() seems to silently assume that the other 
arguments are correct (e.g., off >= 0 and so on).

In the (still) current implementation of 
DataInputStream.readFully(byte[], int, int), when off < 0 and len > 0, 
in the loop it then invokes the underlying in.read(byte[], int, int) 
with a negative offset off + n during the initial iterations.

In the specific case of the tests on underlying FileInputStreams, it 
thus seems that read(byte[], int, int) does not, in turn, validate its 
arguments. I didn't investigate further, although I will in the next 
days if deemed necessary.


On 2020-08-06 22:09, Brian Burkhalter wrote:
>> On Aug 6, 2020, at 12:36 PM, Raffaello Giulietti 
>> <raffaello.giulietti at gmail.com <mailto:raffaello.giulietti at gmail.com>> 
>> wrote:
>>> This looks all right. I would be inclined to do like in [1] and throw 
>>> the RuntimeException on the line after each readFully() and drop the 
>>> return statements], but I’m not going to insist on it.
>>> Thanks,
>>> Brian
>>> [1]http://hg.openjdk.java.net/jdk/jdk/file/db6952bf8c39/test/jdk/java/nio/file/etc/MacVolumesTest.java#l58
>> Sorry, I didn't completely get that.
>> Here we are!
> This looks good. I observed however that the test passes without the 
> change to DataInputStream.
> Brian

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