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Java Forum / General / December 2005usigned int java
Hi, I need to used an unsigned integer in my program. I am actually developing a protocol which at a certain points asks me to transfer 4 bytes unsigned. long makes 8 bytes. How can I transfer the unsigned int value. any help or info is appreciated. regards Rajesh Rapaka On 24 Dec 2005 01:09:51 -0800, "Rajesh.Rapaka" <rajesh.rapaka@gmail.com> wrote, quoted or indirectly quoted someone who said : >I need to used an unsigned integer in my program. I am actually >developing a protocol which at a certain points asks me to transfer 4 >bytes unsigned. long makes 8 bytes. How can I transfer the unsigned int >value. when transferring bytes an int will do for unsigned. It is only when you do a multiplication or compare does signed/unsigned matter. See http://mindprod.com/jgloss/unsigned.html  SignatureCanadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. > On 24 Dec 2005 01:09:51 -0800, "Rajesh.Rapaka" > <rajesh.rapaka@gmail.com> wrote, quoted or indirectly quoted someone [quoted text clipped - 4 lines] > >bytes unsigned. long makes 8 bytes. How can I transfer the unsigned int > >value. > when transferring bytes an int will do for unsigned. It is only when > you do a multiplication or compare does signed/unsigned matter. I think you mean division/remainder instead of multiplication. I'd also add casting to the list. >> when transferring bytes an int will do for unsigned. It is only when >> you do a multiplication or compare does signed/unsigned matter. > >I think you mean division/remainder instead of multiplication. >I'd also add casting to the list. compare, multiplication, division, remainder all are different from a bit point of view for signed/unsigned. addition, subtraction, move are not. see http://mindprod.com/jgloss/unsigned.html for details. SignatureCanadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. > >> when transferring bytes an int will do for unsigned. It is only when > >> you do a multiplication or compare does signed/unsigned matter. [quoted text clipped - 5 lines] > bit point of view for signed/unsigned. addition, subtraction, move are > not. Are you sure about multiplication? Can you provide a counterexample? Thanks. >Are you sure about multiplication? Can you provide >a counterexample? Thanks. In Forth there are signed * and unsigned U* multiplication operators. I implemented them in BBL Forth. There I was multiplying to 32 bit quantities to get a 64 bit result. If you have a hex calculator with more than 32 bits, try some experiments with two +, two - and mixed, treated both as unsigned and signed. pick some large and small numbers. Or try the same in Java with 16 bits where you have char and short to play with to give you a 32 bit result. SignatureCanadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. >>Are you sure about multiplication? Can you provide >>a counterexample? Thanks. [quoted text clipped - 9 lines] > Or try the same in Java with 16 bits where you have char and short to > play with to give you a 32 bit result. The low order 32 bits of a 32 bit multiply is the same for signed and unsigned. All that differs is testing for overflow. Mark Thornton > >>Are you sure about multiplication? Can you provide > >>a counterexample? Thanks. [quoted text clipped - 12 lines] > The low order 32 bits of a 32 bit multiply is the same for signed and > unsigned. All that differs is testing for overflow. Thanks, that's the same conclusion I reached. Since Java truncates overflow, you get exactly the same bits (just like for add/subtract). On Wed, 28 Dec 2005 10:12:57 GMT, Mark Thornton <mark.p.thornton@ntl-spam-world.com> wrote, quoted or indirectly quoted someone who said : >The low order 32 bits of a 32 bit multiply is the same for signed and >unsigned. All that differs is testing for overflow. Here is an example demonstrating this is so. A 32x32->64 bit differs between signed and unsigned however. // unsigned 32-bit multiply long a = ( 0x7fffffffL * 0xffffffffL ) & 0xffffffffL; // signed 32-bit multiply long b = ((long) ( 0x7fffffff * 0xffffffff )) & 0xffffffffL; // prints 2147483649 System.out.println( a ); // prints 2147483649 System.out.println( b ); SignatureCanadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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