Re: [infinispan-dev] writeUnsignedInt() inefficient with bytes between 128 and 255

On 09/03/2009 01:29 PM, Galder Zamarreno wrote: > On 09/03/2009 12:53 PM, Galder Zamarreno wrote: >> Hi, >> >> While looking at https://jira.jboss.org/jira/browse/ISPN-149, I've >> realised that writeUnsignedInt(), due to its dynamic behaivour, it's >> more efficient than using a leading byte and then writing a byte, >> short >> or int. >> >> However, I've spotted an unefficiency in >> UnsignedNumeric.writeUnsignedInt() which is that if you write a byte >> that's between 128-255, it writes two bytes, whereas in theory, you >> could just write it as a single unsigned byte. >> >> Now, I'm not an expert on these methods, but I believe a >> writeUnsignedInt like this would make 128-255 bytes be written as >> 1 byte >> too: >> >> public static void writeUnsignedInt(ObjectOutput out, int i) >> throws >> IOException { >> while ((i& ~0xFF) != 0) { >> out.writeByte((byte) ((i& 0xFF) | 0x100)); >> i>>>= 8; >> } >> out.writeByte((byte) i); >> } >> >> And the read part would look like: >> >> public static int readUnsignedInt(ObjectInput in) throws >> IOException { >> int b = in.readUnsignedByte(); >> int i = b& 0xFF; >> for (int shift = 8; (b& 0x100) != 0; shift += 8) { >> b = in.readUnsignedByte(); >> i |= (b& 0xFFL)<< shift; >> } >> return i; >> } > > Hmmm, the read part is not working as expected. Trying to figure > out how > to get on values equal or bigger than 256 to read the next byte. Hmmm, this is trickier than I thought. In the current solution, you know you have to read more bytes cos the byte you've just read is negative. However, if you use the full 4 bytes, how do you know that you need to read another byte? Hmmmm.... > >> Manik, I think you created these methods in the 1st place, thoughts? >> CC'ing David M L who's quite an expert on this too. >> >> Cheers, > -- Galder Zamarreño Sr. Software Engineer Infinispan, JBoss Cache _______________________________________________ infinispan-dev mailing list infinispan-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/infinispan-dev