Hello!

If I have a dynamic array of bytes, say

byte[] a; a = [1,2,3,4];

Is it possible to somehow cast a number of these bytes into an int or a long, like so;

int b = cast(int)a[0..2];
long c = cast(long)a;

or something? The goal is to convert 2 * 8 bit into 1 * 16 bit or 4 * 8 bit
into 1 * 64 bit. 1) Is it possible? 2) Is it possible without confusing the
GC? 3) How? ;)

Henrik wrote:
> Hello!
> 
> If I have a dynamic array of bytes, say
> 
> byte[] a; a = [1,2,3,4];
> 
> Is it possible to somehow cast a number of these bytes into an int or a long,
> like so;
> 
> int b = cast(int)a[0..2];
> long c = cast(long)a;
> 
> or something? The goal is to convert 2 * 8 bit into 1 * 16 bit or 4 * 8 bit
> into 1 * 64 bit. 1) Is it possible? 2) Is it possible without confusing the
> GC? 3) How? ;)

You need something like:
  int b = *cast(int*)&a[0];
  long c = *cast(long*)a.ptr;

--bb

Bill Baxter wrote:
> Henrik wrote:
> 
>> Hello!
>>
>> If I have a dynamic array of bytes, say
>>
>> byte[] a; a = [1,2,3,4];
>>
>> Is it possible to somehow cast a number of these bytes into an int or a long,
>> like so;
>>
>> int b = cast(int)a[0..2];
>> long c = cast(long)a;
>>
>> or something? The goal is to convert 2 * 8 bit into 1 * 16 bit or 4 * 8 bit
>> into 1 * 64 bit. 1) Is it possible? 2) Is it possible without confusing the
>> GC? 3) How? ;)
> 
> 
> You need something like:
>   int b = *cast(int*)&a[0];
>   long c = *cast(long*)a.ptr;
> 
> --bb

You probably know this, but be very careful while doing this, endianness makes all the difference:

int main()
{
    long a = 10;
    int *b = cast(int *) &a;
    writefln("%d", *b);
}

(Untested) That code will print 10 on a little-endian system, but will print 0 on a big-endian system.

 - Gregor Richards

Gregor Richards wrote:
>(Untested) That code will print 10 on a little-endian system, but will
print 0 on a big-endian system.

Shit, you are right. I would have forgotten about it :| std.system to the rescue!