Robert,
Thank you for explaining this! Perhaps we need to move faster toward
1.0and provide better manuals (and books probably).
Trustin
On 6/15/06, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
The idea is that in a protocol you know what a frame looks like. For
example you might know that a frame consists of an integer id, a string
command name and then depending on the particular command, a variable number
of integers.
In that case you know that if you have only 4 bytes in the buffer that you
cannot fully decode a frame so you "need data". If you have enough data to
read the integer plus the string you could then look up how many integers
you need following that and if you don't have enough bytes, return that you
"need data".
In the decode method returning null does not mean you need data.
Note that this implies that for efficiency you should avoid designing your
protocol so that you need to run through lots of data before you can
determine whether you have enough data to decode an entire frame. So putting
a size field right at the start is a good idea. In that case, the
decodable() method can be pretty simple.
Robert
*"Andres Quijano" <[EMAIL PROTECTED]>*
14/06/2006 21:00
Please respond to mina-dev
To: [email protected]
cc:
Subject: ByteBuffer remaining and hasRemaining
Hi
I'm new to MINA. I've been going through the examples and I'm not
quite understanding how the NEED_DATA and returning null in the
decoders work. Specifically, I do not understand the remaining and
hasRemaining method in ByteBuffer.
The example decoder goes like this:
if (in.remaining() < Constants.HEADER_LEN) {
return MessageDecoderResult.NEED_DATA;
}
I interpret it like "if there are less remaining bytes than the size
of the header, we need more data", which doesn't make sense.
Also, I tried to do something like this in a decoder:
if (in.hasRemaining()) {
return null; // Need more data.
}
On the beggining of the method. The method get's called three times,
and it never returns false on the hasRemaining method.
The question goes simply to: how to know if there's enough data when
decoding an object with many primitives and some strings (of variable
size)?
Thanks
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