Daniel and folks,
It seems like we are getting close to consensus.
I concur with you that the stream-like implementation makes a perfect
sense. I'd prefer to roll out our own stream-like real non-blocking
stream and provide a wrapper to InputStream and OutputStream. I think we
can use java.io.RandomAccessFile as a good starting point:
* http://java.sun.com/javase/6/docs/api/java/io/RandomAccessFile.html
What we need with the new interface are:
* stream-like sequential read and write operations for primitive types,
arrays of primitive type and ByteBuffer
* seek operations - mark, reset, position (let's keep this minimal
because it's not used often)
* discard operation for efficient memory utilization (+ discardAll)
* no flip / no compact
* no convenience read / write methods such as readString, readUTF8,
readEnum, ... (will be provided in a utility class)
For instance, it could look like this:
public interface NameToBeDetermined extends Iterable<ByteBuffer> {
ByteBuffer read();
byte readByte();
int readInt();
int read(ByteBuffer dst);
...
void write(ByteBuffer src);
void writeByte(byte value);
void writeInt(int value);
...
int available();
int position();
void position(int position);
int skip(int bytes);
void mark();
void reset();
void discard();
void discardAll();
// Some extra methods which might help:
ByteOrder order();
void order(ByteOrder order);
boolean isAutoDiscard();
// true by default, which is OK for most users.
void setAutoDiscard(boolean autoDiscard);
// Conversion methods...
ByteBuffer[] asByteBuffers();
InputStream asInputStream();
OutputStream asOutputStream();
}
I introduced autoDiscard so any read buffer is discarded automatically.
Some users would want this happen manually, then they can call
setAutoDiscard(false).
Another good thing to have is a bounded stream, which has limited capacity
to prevent OutOfMemoryError. It should be simple to implement because all
it needs to is implement the interface.
The last (?) thing to consider is to use get and put instead of read and
write to ease migration from IoBuffer, and it is easier to type.
WDYT?
On Sat, 03 May 2008 23:49:41 +0900, Daniel Wirtz <[EMAIL PROTECTED]>
wrote:
Hello Trusin,
you pointed out some very interesting thoughts. In fact it will result in
unexpected behaviour, when common stream wrappers are used on a
non-blocking
stream without proper orevious checking. I see two possibilities: Using
streams that emulate a blocking mode and throw some sort of
WouldBlockException if blocking is disabled (by default) or rolling out
our
own stream-like version of a real non-blocking stream.
I see the following general advantages of streams over buffers:
- Very easy to use because the stream API is very clear and known by most
developers
- Automatic dispose of already consumed underlying buffers
- No exposure of unnecessary low level functionality like flip(),
limit(), iterate over buffers etc.
- Possibility to reuse the same stream when some new data is available so
that protocol developers don`t need to handle buffering on their own
(just
leave unused bytes inside the stream and process them later when more
data
is available / the decoder is notified)
- Zero-Copy without a need for users to know (much) about the underlying
buffer architecture (just append buffers to a stream)
- Not an advantage, but also: Possibility for random access by using
mark(), skip() and reset() in sequence, maybe with an additional moveTo()
relative to the marked position implemented by combining the previous
three
- however, random access is not required for most protocols
- Ability to use common wrappers for OutputStream
- Ability to use common wrappers for InputStream (but only if data
availability is previously checkable/checked to be valid)
Disadvantages of extending java.io.InputStream:
- Unexpected behaviour when using common wrappers on a stream in
non-blocking mode with no proper previous checking of available data
So, do we really need to extend InputStream / use common input wrappers?
Maybe it makes sence to roll out our own stream-like real non-blocking
inputstream that cannot be used with common input wrappers but
implementing
all the required put- and get-Methods. However, I still think that a
stream-like implementation of the whole buffer thing makes it much easier
for the end user to understand and use.
regards
Daniel
--
Trustin Lee - Principal Software Engineer, JBoss, Red Hat
--
what we call human nature is actually human habit
--
http://gleamynode.net/
