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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