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From: Dirk Bruere at NeoPax on 27 Mar 2010 19:56
How do I actually write hex bytes into a byte array?
The obvious method gives me an error ie

myArray[0] = 0xc9;

--
Dirk

http://www.transcendence.me.uk/ - Transcendence UK
http://www.blogtalkradio.com/onetribe - Occult Talk Show
From: Peter Duniho on 27 Mar 2010 20:31
Dirk Bruere at NeoPax wrote:
> How do I actually write hex bytes into a byte array?
> The obvious method gives me an error ie
>
> myArray[0] = 0xc9;

In general, if you are asking a question related to an error you are
seeing, you should post specific information about the error.

And if you are asking a question related to some specific code you are
trying to get to work, you should post a complete enough example of the
code so that at least there is no question about how variables and types
are declared, if not a fully compilable example (see http://sscce.org/)

That said, it may help you to know that "byte" in Java is a signed type,
supporting values only from -128 to 127 (0x80 to 0x7f). The value
0xc9 is the same as 201 decimal, which is outside that range.

The code you posted, assuming "myArray" is declared as:

byte[] myArray;

is essentially the same as this:

int i = 0xc9;
byte b = i;

And hopefully you can see why the above doesn't work.

You can fix the code in at least one of two ways:

� cast the literal to byte, forcing the conversion: "myArray[0] =
(byte)0xc9;"
� specify a literal that can fit in a byte: "myArray[0] = 0xffffffc9;"

Pete
From: Dirk Bruere at NeoPax on 27 Mar 2010 20:43
On 28/03/2010 00:31, Peter Duniho wrote:
> Dirk Bruere at NeoPax wrote:
>> How do I actually write hex bytes into a byte array?
>> The obvious method gives me an error ie
>>
>> myArray[0] = 0xc9;
>
> In general, if you are asking a question related to an error you are
> seeing, you should post specific information about the error.
>
> And if you are asking a question related to some specific code you are
> trying to get to work, you should post a complete enough example of the
> code so that at least there is no question about how variables and types
> are declared, if not a fully compilable example (see http://sscce.org/)
>
> That said, it may help you to know that "byte" in Java is a signed type,
> supporting values only from -128 to 127 (0x80 to 0x7f). The value 0xc9
> is the same as 201 decimal, which is outside that range.
>
> The code you posted, assuming "myArray" is declared as:
>
> byte[] myArray;
>
> is essentially the same as this:
>
> int i = 0xc9;
> byte b = i;
>
> And hopefully you can see why the above doesn't work.
>
> You can fix the code in at least one of two ways:
>
> � cast the literal to byte, forcing the conversion: "myArray[0] =
> (byte)0xc9;"
> � specify a literal that can fit in a byte: "myArray[0] = 0xffffffc9;"
>
> Pete

Thanks.
I saw the error of my ways just before this came up - I did a cast.
I'm going to bed.

--
Dirk

http://www.transcendence.me.uk/ - Transcendence UK
http://www.blogtalkradio.com/onetribe - Occult Talk Show
From: Mike Schilling on 27 Mar 2010 22:35
Peter Duniho wrote:
> Dirk Bruere at NeoPax wrote:
>> How do I actually write hex bytes into a byte array?
>> The obvious method gives me an error ie
>>
>> myArray[0] = 0xc9;
>
> In general, if you are asking a question related to an error you are
> seeing, you should post specific information about the error.
>
> And if you are asking a question related to some specific code you are
> trying to get to work, you should post a complete enough example of
> the code so that at least there is no question about how variables
> and types are declared, if not a fully compilable example (see
> http://sscce.org/)
> That said, it may help you to know that "byte" in Java is a signed
> type, supporting values only from -128 to 127 (0x80 to 0x7f). The
> value 0xc9 is the same as 201 decimal, which is outside that range.
>
> The code you posted, assuming "myArray" is declared as:
>
> byte[] myArray;
>
> is essentially the same as this:
>
> int i = 0xc9;
> byte b = i;
>
> And hopefully you can see why the above doesn't work.
>
> You can fix the code in at least one of two ways:
>
> � cast the literal to byte, forcing the conversion: "myArray[0] =
> (byte)0xc9;"
> � specify a literal that can fit in a byte: "myArray[0] =
> 0xffffffc9;"

How intuitive that an 8-bit literal doesn't fit into an 8-bit byte, but a
32-bit literal does ;-)

A bit more seriously, I presume that 99% of people would use the cast rather
than try to type the right number of 'f's.


From: Mike Amling on 27 Mar 2010 23:06
Mike Schilling wrote:
> Peter Duniho wrote:
>> You can fix the code in at least one of two ways:
>>
>> � cast the literal to byte, forcing the conversion: "myArray[0] =
>> (byte)0xc9;"
>> � specify a literal that can fit in a byte: "myArray[0] =
>> 0xffffffc9;"
>
> How intuitive that an 8-bit literal doesn't fit into an 8-bit byte, but a
> 32-bit literal does ;-)
>
> A bit more seriously, I presume that 99% of people would use the cast rather
> than try to type the right number of 'f's.

To avoid the counting of Fs, you can also use

myByteArray[0]=0xC9-256;

to assign 0x80..0xFF to a byte.

--Mike Amling
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