Re: [Asterisk-java-users] fastagi.command.GetDataCommand issue

[Steve D. <Ste...@Su...>]

On Apr 29, 2005, at 4:56 PM, Stefan Reuter wrote:

>>> It seems to me that "GET DATA foo" is translated to "GET DATA foo 0
>>> 1024" and thats exactly what asterisk-java sends. right?
>>>
>>
>> Yes, that is what it sends.  I think it should send "GET DATA foo".
>>
>
> hmm we could do this, though it would imply to use nullable Integers
> instead of the easier to use ints for timeout and maxDigits.

Um, just change return "GET DATA " + escapeAndQuote(file) + " " +  
timeout + ...
to "GET DATA " + escapeAndQuote(file) + " " + (timeout != 0 ?  
timeout : "")
and likewise for maxDigits.

> That would
> make GetDataCommand quite different from the other Commands that use
> primitive attributes.

"Consistency is the hobgoblin of small minds" ;-)

> Nevertheless asterisk uses a default timeout of 0 and a default
> maxDigits of 1024, so there is really no semantic difference  
> between the
> two.

In fact there is.  If you send "GET FILE foo", then  
ast_readstring_full gets timeout=2000 and ftimeout=6000.
But if you send "GET FILE foo 0 1024, then timeout=ftimeout=6000.

> You might consider this knowledge of asterisk internals a violation
> of encapsulation practices but some knowledge is needed anyway  
> (i.e. to
> enforce the maximum maxDigits of 1024 to prevent buffer overflows, see
> below).

Not at all.  Asterisk enforces the max length of 1024 as it should,  
since it owns the buffer.  Asterisk-java
has no business knowing this.  Nor should it care as long as it sends  
the syntactically correct GET DATA
command, which is documented in res_agi.c as:

GET DATA <file to be streamed> [timeout] [max digits]

Which actually is wrong.  It should be:

GET DATA <file to be streamed> [timeout [max digits]]

> Using 1024 as maxDigits is the maximum number of digits GET DATA can
> handle anyway as the buffer that is used by asterisk is defined as
> char data[1024]. Although asterisk does not enforce a maximum of 1024
> reading more digits would result in a buffer overflow.

Actually, Asterisk does enforce the 1024 limit.