- Fixes#1229
- Primarily written by @normanmaurer and revised by @trustin
This commit removes the notion of unfolding from the codec framework
completely. Unfolding was introduced in Netty 3.x to work around the
shortcoming of the codec framework where encode() and decode() did not
allow generating multiple messages.
Such a shortcoming can be fixed by changing the signature of encode()
and decode() instead of introducing an obscure workaround like
unfolding. Therefore, we changed the signature of them in 4.0.
The change is simple, but backward-incompatible. encode() and decode()
do not return anything. Instead, the codec framework will pass a
MessageBuf<Object> so encode() and decode() can add the generated
messages into the MessageBuf.
This pull request provides a framework for exchanging a very large
stream between handlers, typically between a decoder and an inbound
handler (or between a handler that writes a message and an encoder that
encodes that message).
For example, an HTTP decoder, previously, generates multiple
micro-messages to decode an HTTP message (i.e. HttpRequest +
HttpChunks). With the streaming API, The HTTP decoder can simply
generate a single HTTP message whose content is a Stream. And then the
inbound handler can consume the Stream via the buffer you created when
you begin to read the stream. If you create a buffer whose capacity is
bounded, you can handle a very large stream without allocating a lot of
memory. If you just want to wait until the whole content is ready, you
can also do that with an unbounded buffer.
The streaming API also supports a limited form of communication between
a producer (i.e. decoder) and a consumer. A producer can abort the
stream if the stream is not valid anymore. A consumer can choose to
reject or discard the stream, where rejection is for unrecoverable
failure and discard is for recoverable failure.
P.S. Special thanks to @jpinner for the initial input.
- Make PoolSubpage a linked list node in the pool
- Now that a subpage is added to and removed from the pool correctly, allocating a subpage from the pool became vastly simpler.
