Converting byte[] to signed int

[JT]

Need some help in converting a byte[] to a signed int. This is what I
have attempted to do:

byte[] bytes = new byte[3] { 0xFF, 0xFF, 0x9C};
StringBuilder hexString = new StringBuilder() ;
foreach (byte tmpByte in bytes) hexString.Appen d(tmpByte.ToStr ing("X2"));

int intValue = int.Parse(hexSt ring.ToString() ,
NumberStyles.Al lowHexSpecific) ;

I am getting a positive intValue. However, the intValue is supposed to
be a negative value. Any help would be greatly appreciated.

JT

[Dennis Myrén]

Re: Converting byte[] to signed int

I cannot see why you are expecting a negative value.
[BASE16] FFFF9C = [BASE10] 16777116

--
Regards,
Dennis JD Myrén
Oslo Kodebureau
"JT" <jt@jt.jt> wrote in message
news:OFYOqCizEH A.2200@TK2MSFTN GP09.phx.gbl...[color=blue]
> Need some help in converting a byte[] to a signed int. This is what I
> have attempted to do:
>
> byte[] bytes = new byte[3] { 0xFF, 0xFF, 0x9C};
> StringBuilder hexString = new StringBuilder() ;
> foreach (byte tmpByte in bytes) hexString.Appen d(tmpByte.ToStr ing("X2"));
>
> int intValue = int.Parse(hexSt ring.ToString() ,
> NumberStyles.Al lowHexSpecific) ;
>
> I am getting a positive intValue. However, the intValue is supposed to be
> a negative value. Any help would be greatly appreciated.
>
> JT[/color]

[JT]

Re: Converting byte[] to signed int

Sorry, I should explained my situation abit more. I am getting some
bytes from a device connected to the serial port. The device displays a
negative value and the bytes I am getting for the value is FFFF9C.
Also, the API documentation says that the bytes are in Big-Endian. In
this case, would FFFF9C translate to some negative integer value?

Dennis Myrén wrote:
[color=blue]
> I cannot see why you are expecting a negative value.
> [BASE16] FFFF9C = [BASE10] 16777116
>[/color]

[Jon Skeet [C# MVP]]

Re: Converting byte[] to signed int

JT <jt@jt.jt> wrote:[color=blue]
> Need some help in converting a byte[] to a signed int. This is what I
> have attempted to do:
>
> byte[] bytes = new byte[3] { 0xFF, 0xFF, 0x9C};
> StringBuilder hexString = new StringBuilder() ;
> foreach (byte tmpByte in bytes) hexString.Appen d(tmpByte.ToStr ing("X2"));
>
> int intValue = int.Parse(hexSt ring.ToString() ,
> NumberStyles.Al lowHexSpecific) ;
>
> I am getting a positive intValue. However, the intValue is supposed to
> be a negative value. Any help would be greatly appreciated.[/color]

A 24-bit signed int is quite rare - did you really mean it to only have
3 bytes rather than 4?

You can use BitConverter to do the conversion without using a string
format. If that's the wrong endianness, you can use my
EndianBitConver ter from

http://www.pobox.com/~skeet/csharp/miscutil

--
Jon Skeet - <skeet@pobox.co m>

http://www.pobox.com/~skeet

If replying to the group, please do not mail me too

[Dennis Myrén]

Re: Converting byte[] to signed int

Then, try:
int result = (a [0x2] << 0x8) + (a [0x1] << 0x10) + (a [0x0] << 0x18);

--
Regards,
Dennis JD Myrén
Oslo Kodebureau
"JT" <jt@jt.jt> wrote in message
news:uygZ%23Liz EHA.4028@TK2MSF TNGP15.phx.gbl. ..[color=blue]
> Sorry, I should explained my situation abit more. I am getting some bytes
> from a device connected to the serial port. The device displays a
> negative value and the bytes I am getting for the value is FFFF9C. Also,
> the API documentation says that the bytes are in Big-Endian. In this
> case, would FFFF9C translate to some negative integer value?
>
> Dennis Myrén wrote:
>[color=green]
>> I cannot see why you are expecting a negative value.
>> [BASE16] FFFF9C = [BASE10] 16777116
>>[/color][/color]

[Dennis Myrén]

Re: Converting byte[] to signed int

(Where 'a' is represents your variable 'bytes')

--
Regards,
Dennis JD Myrén
Oslo Kodebureau
"Dennis Myrén" <dennis@oslokb. no> wrote in message
news:lfknd.1753 7$Km6.208108@ne ws4.e.nsc.no...[color=blue]
> Then, try:
> int result = (a [0x2] << 0x8) + (a [0x1] << 0x10) + (a [0x0] << 0x18);
>
> --
> Regards,
> Dennis JD Myrén
> Oslo Kodebureau
> "JT" <jt@jt.jt> wrote in message
> news:uygZ%23Liz EHA.4028@TK2MSF TNGP15.phx.gbl. ..[color=green]
>> Sorry, I should explained my situation abit more. I am getting some
>> bytes from a device connected to the serial port. The device displays a
>> negative value and the bytes I am getting for the value is FFFF9C. Also,
>> the API documentation says that the bytes are in Big-Endian. In this
>> case, would FFFF9C translate to some negative integer value?
>>
>> Dennis Myrén wrote:
>>[color=darkred]
>>> I cannot see why you are expecting a negative value.
>>> [BASE16] FFFF9C = [BASE10] 16777116
>>>[/color][/color]
>
>[/color]

[Dennis Myrén]

Re: Converting byte[] to signed int

JT wrote:[color=blue]
> In this case, would FFFF9C translate to some negative integer value?[/color]

Yes, it would be -25600 .

--
Regards,
Dennis JD Myrén
Oslo Kodebureau
"JT" <jt@jt.jt> wrote in message
news:uygZ%23Liz EHA.4028@TK2MSF TNGP15.phx.gbl. ..[color=blue]
> Sorry, I should explained my situation abit more. I am getting some bytes
> from a device connected to the serial port. The device displays a
> negative value and the bytes I am getting for the value is FFFF9C. Also,
> the API documentation says that the bytes are in Big-Endian. In this
> case, would FFFF9C translate to some negative integer value?
>
> Dennis Myrén wrote:
>[color=green]
>> I cannot see why you are expecting a negative value.
>> [BASE16] FFFF9C = [BASE10] 16777116
>>[/color][/color]

[Liam McNamara]

Re: Converting byte[] to signed int

The number given is positive for both big and little endian:

Big: 00FFFF9C
Little: 9CFFFF00

Only when the left-most bit is set will it become negative.

using System.Net;

byte[] data = new byte[] { 0x0, 0xFF, 0xFF, 0x9C };
int bigEndian = BitConverter.To Int32(data, 0);
int littleEndian = IPAddress.Netwo rkToHostOrder(b igEndian);

--Liam.

"JT" <jt@jt.jt> wrote in message
news:uygZ%23Liz EHA.4028@TK2MSF TNGP15.phx.gbl. ..[color=blue]
> Sorry, I should explained my situation abit more. I am getting some
> bytes from a device connected to the serial port. The device displays a
> negative value and the bytes I am getting for the value is FFFF9C.
> Also, the API documentation says that the bytes are in Big-Endian. In
> this case, would FFFF9C translate to some negative integer value?
>
> Dennis Myrén wrote:
>[color=green]
> > I cannot see why you are expecting a negative value.
> > [BASE16] FFFF9C = [BASE10] 16777116
> >[/color][/color]

[James Curran]

Re: Converting byte[] to signed int

What you need to do is "sign-extend" the upper bit from the third byte into
the fourth. (i.e., if the high bit of the highest byte you have is "1",
then every bit of the new fourth byte should be "1". Otherwise they should
be all "0"s)

byte[] data = new byte[] { 0x0, 0xFF, 0xFF, 0x9C };
data[0] = (byte) ((data[1] > 0x7f) ? 0xFF : 0x00);
int littleEndian = BitConverter.To Int32(data, 0);
int bigEndian= IPAddress.Netwo rkToHostOrder(l ittleEndian);
Console.WriteLi ne( "{0}, {0:x}",bigEndia n);

This correct prints out "-100, FFFFFF9C"

Note that Liam had bigEndian & littleEndian reversed in his code.


--
Truth,
James Curran
[erstwhile VC++ MVP]
Home: www.noveltheory.com Work: www.njtheater.com
Blog: www.honestillusion.com Day Job: www.partsearch.com

"JT" <jt@jt.jt> wrote in message
news:OFYOqCizEH A.2200@TK2MSFTN GP09.phx.gbl...[color=blue]
> Need some help in converting a byte[] to a signed int. This is what I
> have attempted to do:
>
> byte[] bytes = new byte[3] { 0xFF, 0xFF, 0x9C};
> StringBuilder hexString = new StringBuilder() ;
> foreach (byte tmpByte in bytes) hexString.Appen d(tmpByte.ToStr ing("X2"));
>
> int intValue = int.Parse(hexSt ring.ToString() ,
> NumberStyles.Al lowHexSpecific) ;
>
> I am getting a positive intValue. However, the intValue is supposed to
> be a negative value. Any help would be greatly appreciated.
>
> JT[/color]

[JT]

Re: Converting byte[] to signed int

thanks james. another question. in the event, the byte
data is 2 bytes, how would this be handled? thanks.
[color=blue]
>-----Original Message-----
>What you need to do is "sign-extend" the upper bit from[/color]
the third byte into[color=blue]
>the fourth. (i.e., if the high bit of the highest byte[/color]
you have is "1",[color=blue]
>then every bit of the new fourth byte should be "1".[/color]
Otherwise they should[color=blue]
>be all "0"s)
>
> byte[] data = new byte[] { 0x0, 0xFF, 0xFF, 0x9C };
> data[0] = (byte) ((data[1] > 0x7f) ? 0xFF : 0x00);
> int littleEndian = BitConverter.To Int32(data, 0);
> int bigEndian= IPAddress.Netwo rkToHostOrder[/color]
(littleEndian);[color=blue]
> Console.WriteLi ne( "{0}, {0:x}",bigEndia n);
>
>This correct prints out "-100, FFFFFF9C"
>
>Note that Liam had bigEndian & littleEndian reversed in[/color]
his code.[color=blue]
>
>
>--
>Truth,
>James Curran
>[erstwhile VC++ MVP]
>Home: www.noveltheory.com Work: www.njtheater.com
>Blog: www.honestillusion.com Day Job: www.partsearch.com
>
>"JT" <jt@jt.jt> wrote in message
>news:OFYOqCizE HA.2200@TK2MSFT NGP09.phx.gbl.. .[color=green]
>> Need some help in converting a byte[] to a signed int.[/color][/color]
This is what I[color=blue][color=green]
>> have attempted to do:
>>
>> byte[] bytes = new byte[3] { 0xFF, 0xFF, 0x9C};
>> StringBuilder hexString = new StringBuilder() ;
>> foreach (byte tmpByte in bytes) hexString.Appen d[/color][/color]
(tmpByte.ToStri ng("X2"));[color=blue][color=green]
>>
>> int intValue = int.Parse(hexSt ring.ToString() ,
>> NumberStyles.Al lowHexSpecific) ;
>>
>> I am getting a positive intValue. However, the[/color][/color]
intValue is supposed to[color=blue][color=green]
>> be a negative value. Any help would be greatly[/color][/color]
appreciated.[color=blue][color=green]
>>
>> JT[/color]
>
>
>.
>[/color]

[James Curran]

Re: Converting byte[] to signed int

"JT" <anonymous@disc ussions.microso ft.com> wrote in message
news:7a6501c4d0 35$0b4aebc0$a40 1280a@phx.gbl.. .[color=blue]
> thanks james. another question. in the event, the byte
> data is 2 bytes, how would this be handled? thanks.[/color]

int littleEndian = BitConverter.To Int16(data, 0);

In this case the sign-bit is already in the correct place, so know other
modification is needed.

--
Truth,
James Curran
[erstwhile VC++ MVP]
Home: www.noveltheory.com Work: www.njtheater.com
Blog: www.honestillusion.com Day Job: www.partsearch.com
[color=blue]
>[color=green]
> >-----Original Message-----
> >What you need to do is "sign-extend" the upper bit from[/color]
> the third byte into[color=green]
> >the fourth. (i.e., if the high bit of the highest byte[/color]
> you have is "1",[color=green]
> >then every bit of the new fourth byte should be "1".[/color]
> Otherwise they should[color=green]
> >be all "0"s)
> >
> > byte[] data = new byte[] { 0x0, 0xFF, 0xFF, 0x9C };
> > data[0] = (byte) ((data[1] > 0x7f) ? 0xFF : 0x00);
> > int littleEndian = BitConverter.To Int32(data, 0);
> > int bigEndian= IPAddress.Netwo rkToHostOrder[/color]
> (littleEndian);[color=green]
> > Console.WriteLi ne( "{0}, {0:x}",bigEndia n);
> >
> >This correct prints out "-100, FFFFFF9C"
> >
> >Note that Liam had bigEndian & littleEndian reversed in[/color]
> his code.[color=green]
> >
> >
> >--
> >Truth,
> >James Curran
> >[erstwhile VC++ MVP]
> >Home: www.noveltheory.com Work: www.njtheater.com
> >Blog: www.honestillusion.com Day Job: www.partsearch.com
> >
> >"JT" <jt@jt.jt> wrote in message
> >news:OFYOqCizE HA.2200@TK2MSFT NGP09.phx.gbl.. .[color=darkred]
> >> Need some help in converting a byte[] to a signed int.[/color][/color]
> This is what I[color=green][color=darkred]
> >> have attempted to do:
> >>
> >> byte[] bytes = new byte[3] { 0xFF, 0xFF, 0x9C};
> >> StringBuilder hexString = new StringBuilder() ;
> >> foreach (byte tmpByte in bytes) hexString.Appen d[/color][/color]
> (tmpByte.ToStri ng("X2"));[color=green][color=darkred]
> >>
> >> int intValue = int.Parse(hexSt ring.ToString() ,
> >> NumberStyles.Al lowHexSpecific) ;
> >>
> >> I am getting a positive intValue. However, the[/color][/color]
> intValue is supposed to[color=green][color=darkred]
> >> be a negative value. Any help would be greatly[/color][/color]
> appreciated.[color=green][color=darkred]
> >>
> >> JT[/color]
> >
> >
> >.
> >[/color][/color]