What would be the most efficient way to calculate the two's complement
of a variable length byte array?
Thanks for your time.
Feb 10 '07
14  10514 
On Feb 16, 11:44 pm, "Bruce Wood" <brucew...@cana da.comwrote:
On Feb 16, 8:54 pm, darthgha...@gma il.com wrote:
So what you are all saying is that there is no easy way to get a two's
complement of a byte array? That sucks. I guess that's Microsoft's
gift to me?
I don't know if it's particularly _Microsoft's_ gift to you. More like
the modern Intel processor's gift to you. In fact, I don't think I've
ever worked on a language or a processor in which something as obscure
as taking the two's-complement of a byte array was optimized into some
special instruction or operation.
There's certainly an _easy_ way to do it: loop through the bytes and
take the two's complement of each one. That's pretty darned easy.
However, what you asked for was _faster_. As I said, I've never seen a
_fast_, short-cut way to do that, on any platform, on any chip.
Perhaps others with wider experience have, but not me.
Thanks for the response. That was the way I was hoping to avoid.
Looks like it's the best bet.
Thanks again for the time.
Chris
On Feb 17, 12:16 am, darthgha...@gma il.com wrote:
On Feb 16, 11:44 pm, "Bruce Wood" <brucew...@cana da.comwrote:
On Feb 16, 8:54 pm, darthgha...@gma il.com wrote:
So what you are all saying is that there is no easy way to get a two's
complement of a byte array? That sucks. I guess that's Microsoft's
gift to me?
I don't know if it's particularly _Microsoft's_ gift to you. More like
the modern Intel processor's gift to you. In fact, I don't think I've
ever worked on a language or a processor in which something as obscure
as taking the two's-complement of a byte array was optimized into some
special instruction or operation.
There's certainly an _easy_ way to do it: loop through the bytes and
take the two's complement of each one. That's pretty darned easy.
However, what you asked for was _faster_. As I said, I've never seen a
_fast_, short-cut way to do that, on any platform, on any chip.
Perhaps others with wider experience have, but not me.
Thanks for the response. That was the way I was hoping to avoid.
Looks like it's the best bet.
Thanks again for the time.
Chris
Looks like the newest version of Visual Studio will come with a
BigInteger class that I could use. It doesn't support bitwise right
now, but may be they will add it later.
Here's where I saw that: http://blogs.msdn.com/bclteam/archiv...bar-gazit.aspx
On Feb 20, 8:25 pm, darthgha...@gma il.com wrote:
On Feb 17, 12:16 am, darthgha...@gma il.com wrote:
On Feb 16, 11:44 pm, "Bruce Wood" <brucew...@cana da.comwrote:
On Feb 16, 8:54 pm, darthgha...@gma il.com wrote:
So what you are all saying is that there is no easy way to get a two's
complement of a byte array? That sucks. I guess that's Microsoft's
gift to me?
I don't know if it's particularly _Microsoft's_ gift to you. More like
the modern Intel processor's gift to you. In fact, I don't think I've
ever worked on a language or a processor in which something as obscure
as taking the two's-complement of a byte array was optimized into some
special instruction or operation.
There's certainly an _easy_ way to do it: loop through the bytes and
take the two's complement of each one. That's pretty darned easy.
However, what you asked for was _faster_. As I said, I've never seen a
_fast_, short-cut way to do that, on any platform, on any chip.
Perhaps others with wider experience have, but not me.
Thanks for the response. That was the way I was hoping to avoid.
Looks like it's the best bet.
Thanks again for the time.
Chris
Looks like the newest version of Visual Studio will come with a
BigInteger class that I could use. It doesn't support bitwise right
now, but may be they will add it later.
Here's where I saw that:http://blogs.msdn.com/bclteam/archiv...ucing-system-n...
Sorry... still won't work. Again, if you want ones-complement then
this is fine. If you want twos-complement then it won't fly: you have
to take twos-complement byte by byte.
"Bruce Wood" <br*******@cana da.comwrote in message
news:11******** **************@ j27g2000cwj.goo glegroups.com.. .
On Feb 16, 8:54 pm, darthgha...@gma il.com wrote:
>So what you are all saying is that there is no easy way to get a two's
complement of a byte array? That sucks. I guess that's Microsoft's
gift to me?
I don't know if it's particularly _Microsoft's_ gift to you. More like
the modern Intel processor's gift to you. In fact, I don't think I've
ever worked on a language or a processor in which something as obscure
as taking the two's-complement of a byte array was optimized into some
special instruction or operation.
PSUBSB? http://asm.inightmare.org/opcodelst/index.php?op=PSUBSB
>
There's certainly an _easy_ way to do it: loop through the bytes and
take the two's complement of each one. That's pretty darned easy.
However, what you asked for was _faster_. As I said, I've never seen a
_fast_, short-cut way to do that, on any platform, on any chip.
Perhaps others with wider experience have, but not me.
"Ben Voigt" <rb*@nospam.nos pamwrote in message
news:uA******** ******@TK2MSFTN GP04.phx.gbl...
>
"Bruce Wood" <br*******@cana da.comwrote in message
news:11******** **************@ j27g2000cwj.goo glegroups.com.. .
>On Feb 16, 8:54 pm, darthgha...@gma il.com wrote:
>>So what you are all saying is that there is no easy way to get a two's
complement of a byte array? That sucks. I guess that's Microsoft's
gift to me?
I don't know if it's particularly _Microsoft's_ gift to you. More like
the modern Intel processor's gift to you. In fact, I don't think I've
ever worked on a language or a processor in which something as obscure
as taking the two's-complement of a byte array was optimized into some
special instruction or operation.
PSUBSB?
http://asm.inightmare.org/opcodelst/index.php?op=PSUBSB
Sorry, if you want true two's-complement, don't use non-saturating PSUBB http://asm.inightmare.org/opcodelst/index.php?op=PSUBB
If you want arithmetic negation, PSUBSB more likely serves your purpose. This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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