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digitalmars.D.learn - Binary data in the code?

reply Bill Baxter <wbaxter gmail.com> writes:
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
Nov 04 2006
next sibling parent reply "Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:
"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.
Nov 04 2006
parent reply Chris Nicholson-Sauls <ibisbasenji gmail.com> writes:
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
Nov 04 2006
parent Bill Baxter <wbaxter gmail.com> writes:
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
Nov 04 2006
prev sibling parent reply BCS <empty pathlink.com> writes:
== 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];
Nov 04 2006
parent reply Bill Baxter <wbaxter gmail.com> writes:
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
Nov 04 2006
parent reply Chris Nicholson-Sauls <ibisbasenji gmail.com> writes:
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
Nov 05 2006
parent Bill Baxter <wbaxter gmail.com> writes:
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
Nov 05 2006