casting and arrays..

[Daniel Keep]

gareis wrote:
> Chris Warwick wrote:
>> "Kirk McDonald" <kirklin.mcdonald at gmail.com> wrote in message
>> news:esvk4l$28mi$1 at digitalmars.com...
>>> Chris Warwick wrote:
>>>> "Jarrett Billingsley" <kb3ctd2 at yahoo.com> wrote in message
>>>> news:esvhdv$261a$1 at digitalmars.com...
>>>>> "Chris Warwick" <sp at m.me.not> wrote in message
>>>>> news:esvf5h$2317$1 at digitalmars.com...
>>>>>> std.file.read(filename);
>>>>>>
>>>>>> returns type void[]
>>>> Ok say you have that void[] array returned from std.read.file().
>>>> Whats the best way to copy a struct out from the void array? Only
>>>> way i can think is memcpy, or some heavy duty casting and pointers.
>>>> Is there a cleaner - pretier way with D?
>>>>
>>>> thanks,
>>>>
>>>> cw
>>> Assuming that array.length == YourStruct.sizeof, you can say
>>>     cast(YourStruct*)array.ptr
>>> to treat the array as the struct in-place.
>>
>> Well i cant realy do that cause im reading a binary file in, and then
>> i want to parse it, extract structs and various types here and there.
> 
> Then you need to do pointer arithmetic, it seems. Assuming your struct
> has a deserializer method that takes a void*:
> ---
> for (int i = 0; i < array.length; i++) {
>     if (someStructStartsHere()) {
>         someStruct s;
>         s.deserialize(array.ptr + i);
>         do_stuff_with_someStruct (s);
>     }
> }
> ---
> 
> That should probably work.
> 
>> cheers,
>>
>> cw
>>
>>

Personally, I like std.stream.MemoryStream for things like this.  That
way, I don't have to stuff around with pointer arithmetic, and
potentially make a mistake.

Incidentally, I never knew that you could safely cast arrays of one type
to another!  Yet another thing I didn't know about D :P

	-- Daniel

-- 
Unlike Knuth, I have neither proven or tried the above; it may not even
make sense.

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