How does one embed binary data in code with D?

In C/C++ one would do something like:

  static const unsigned char data[] = {99,12,2,21};

The compiler counts the elements for you, but you still get a compile-time length, so you can do sizeof(data) and you'll get back 4 in the above example.

With D it looks like to get a fixed-size array I have to count the elements myself (annoying if there are a page full of numbers):
  static const ubyte[4] data = {99,12,2,21};

Or live with a dynamic array:
  static const ubyte[] data = {99,12,2,21};

Neither of which seems to be quite what I want, which is to end up with exactly one non-modifiable copy of the data in the data segment.

Thanks,
--bb

"Bill Baxter" <wbaxter@gmail.com> wrote in message news:eihhpl$1ish$1@digitaldaemon.com...

> Or live with a dynamic array:
>   static const ubyte[] data = {99,12,2,21};

Actually, if you then write

data.length = 6;

The compiler will complain.

However, getting data.sizeof does still return 8, which is the size of a dynamic array reference.. so.. hmm, confusing.

Jarrett Billingsley wrote:
> "Bill Baxter" <wbaxter@gmail.com> wrote in message news:eihhpl$1ish$1@digitaldaemon.com...
> 
> 
>>Or live with a dynamic array:
>>  static const ubyte[] data = {99,12,2,21};
> 
> 
> Actually, if you then write
> 
> data.length = 6;
> 
> The compiler will complain.
> 
> However, getting data.sizeof does still return 8, which is the size of a dynamic array reference.. so.. hmm, confusing. 
> 
> 

Of course one can get the "actual" size by doing 'data.length * (typeof(data[0]).sizeof)' but... ack, if you need to use this a lot (which I assume he will).  Might be another example of where an expression alias would be useful.

-- Chris Nicholson-Sauls

Chris Nicholson-Sauls wrote:
> Jarrett Billingsley wrote:
> 
>> "Bill Baxter" <wbaxter@gmail.com> wrote in message news:eihhpl$1ish$1@digitaldaemon.com...
>>
>>
>>> Or live with a dynamic array:
>>>  static const ubyte[] data = {99,12,2,21};
>>
>>
>>
>> Actually, if you then write
>>
>> data.length = 6;
>>
>> The compiler will complain.

The compilers complaints can be useful for the fixed-length array --
  static const ubyte[1 /*intentionally wrong*/] data = [99,12,2,21];

The compiler will complain 'hey 1 is to small for 4 elements'.
Really annoying to have to try to compile once to get the fixed length for the array, but it works.

It seems like there should be a syntax for a fixed-length array with automatically-deduced length.

I suggest either

  static const ubyte[$] data = [99,12,2,21];

taking the '$'-means-length syntax from arrays.  That would suggest that ubyte[length] data should also work.

Or alternatively use the 'auto' keyword:

  static const ubyte[auto] data = [99,12,2,21];


---
Anyway, I do find it useful to embed binary data in the app quite often, so I hope someone can chime in with the right way to do it in D.  It's good for inlining little images and things like that.
In fact, I have a little command line utility program for C++ that I use just for that purpose.  It takes binary files and converts them to C++ source files. (It's a slightly modified version of this: http://fox-toolkit.net/cgi-bin/wiki.pl?Tutorial_14_Reswrap)

I guess if I wrote a D version of that tool then I could have it automatically spit out the length as well, assuming fixed-length arrays are the right way to do this.

--bb

== Quote from Bill Baxter (wbaxter@gmail.com)'s article
> How does one embed binary data in code with D?
> In C/C++ one would do something like:
>    static const unsigned char data[] = {99,12,2,21};
> The compiler counts the elements for you, but you still get a
> compile-time length, so you can do sizeof(data) and you'll get
> back 4 in the above example.
[...]
> Thanks,
> --bb


IIRC, this works:

auto data = [cast(char)99,12,2,21];
// type of data == char[4];

BCS wrote:
> == Quote from Bill Baxter (wbaxter@gmail.com)'s article
> 
>>How does one embed binary data in code with D?
>>In C/C++ one would do something like:
>>   static const unsigned char data[] = {99,12,2,21};
>>The compiler counts the elements for you, but you still get a
>>compile-time length, so you can do sizeof(data) and you'll get
>>back 4 in the above example.
> 
> [...]
> 
>>Thanks,
>>--bb
> 
> 
> 
> IIRC, this works:
> 
> auto data = [cast(char)99,12,2,21];
> // type of data == char[4];


Ick.  Combines the lack of readability of 'auto' with the lameness of D's first-value array typing rule.

It's beside the point though, since that doesn't actually work.
   staticdata.d(9): Error: cannot infer type from initializer

--bb

Bill Baxter wrote:
> BCS wrote:
> 
>> == Quote from Bill Baxter (wbaxter@gmail.com)'s article
>>
>>> How does one embed binary data in code with D?
>>> In C/C++ one would do something like:
>>>   static const unsigned char data[] = {99,12,2,21};
>>> The compiler counts the elements for you, but you still get a
>>> compile-time length, so you can do sizeof(data) and you'll get
>>> back 4 in the above example.
>>
>>
>> [...]
>>
>>> Thanks,
>>> --bb
>>
>>
>>
>>
>> IIRC, this works:
>>
>> auto data = [cast(char)99,12,2,21];
>> // type of data == char[4];
> 
> 
> 
> Ick.  Combines the lack of readability of 'auto' with the lameness of D's first-value array typing rule.
> 
> It's beside the point though, since that doesn't actually work.
>    staticdata.d(9): Error: cannot infer type from initializer
> 
> --bb

Well, if as in the example one wishes to use char[] as the holding data type, one can always just use D's HexStrings.  Then the example becomes:

const data = x"63 0C 02 15"c ;

-- Chris Nicholson-Sauls

Chris Nicholson-Sauls wrote:
> Bill Baxter wrote:
> 
>> BCS wrote:
>>
>>> == Quote from Bill Baxter (wbaxter@gmail.com)'s article
>>>
>>>> How does one embed binary data in code with D?
>>>> In C/C++ one would do something like:
>>>>   static const unsigned char data[] = {99,12,2,21};
>>>> The compiler counts the elements for you, but you still get a
>>>> compile-time length, so you can do sizeof(data) and you'll get
>>>> back 4 in the above example.
>>>
>>>
>>>
>>> [...]
>>>
>>>> Thanks,
>>>> --bb
>>>
>>>
>>>
>>>
>>>
>>> IIRC, this works:
>>>
>>> auto data = [cast(char)99,12,2,21];
>>> // type of data == char[4];
>>
>>
>>
>>
>> Ick.  Combines the lack of readability of 'auto' with the lameness of D's first-value array typing rule.
>>
>> It's beside the point though, since that doesn't actually work.
>>    staticdata.d(9): Error: cannot infer type from initializer
>>
>> --bb
> 
> 
> Well, if as in the example one wishes to use char[] as the holding data type, one can always just use D's HexStrings.  Then the example becomes:
> 
> const data = x"63 0C 02 15"c ;
> 
> -- Chris Nicholson-Sauls

No dice:
  static const auto data = x"00 10 A3"c;
  --> ?Error: 4invalid UTF-8 sequence

The ? is actually some non-ascii character.

--bb