Re: Help with array maniipulation

2014-02-04 Thread bearophile 

Ali Çehreli:

Is that the C extension where the last array in a struct can 
have more elements than its size? That will be a problem in D.


Since V.2.065 D supports well variable-length structs. You have 
to use ubyte[0] data, and then allocate a large enough memory for 
the whole variable-length struct. Here I have written an usage 
example:


http://rosettacode.org/wiki/Sokoban#Faster_Version

Bye,
bearophile

Re: Help with array maniipulation

2014-02-04 Thread ollie 
On Tue, 04 Feb 2014 11:16:00 -0800, Ali Çehreli wrote:


> Is that the C extension where the last array in a struct can have more 
> elements than its size? That will be a problem in D.

yes it is.

>  int[] D_slice = C_array[0 .. C_array_number_of_elements];

Thank you, that gives me what I was looking for. I thought I had tried
something like that. Too many moving parts with threads and context
changes to call GDK/GTK functions make things very precarious. I am
still getting an access violation, but your help has moved me a step
nearer a solution.

Thanks,
ollie

Re: Help with array maniipulation

2014-02-04 Thread Ali Çehreli 

On 02/04/2014 10:58 AM, ollie wrote:

> I have a C Struct:

[...]

> uintdata_size;
> ubyte[1]data;

Is that the C extension where the last array in a struct can have more 
elements than its size? That will be a problem in D.


> }
>
> libraw_dcraw_make_mem_thumb() returns a pointer to this struct.
> I need to create a char[] from the data and data_size members,
> ideally without copying, to send to GdkPixbufLoader.write(char[]).
>
> If I do this:
> libraw_processed_image_t *img;
> img = libraw_dcraw_make_mem_thumb();
> char[] buf = cast(char[]) img.data[];

This:

  char[] buf = (cast(char*)img.data.ptr)[0  .. img.data_size];

However, as I said above, data won't have room for more than 1 element.

In any case, treating a C array as a D slice is achieved by the 
following syntax:


int[] D_slice = C_array[0 .. C_array_number_of_elements];

Ali

Help with array maniipulation

2014-02-04 Thread ollie 
I have a C Struct:

   typedef struct
   {
   enum LibRaw_image_formats type; 
   ushort  height,
   width,
   colors,
   bits;
   unsigned int  data_size; 
   unsigned char data[1]; 
   }libraw_processed_image_t;

with a D version:

   struct libraw_processed_image_t
   {
   LibRaw_image_formatstype; 
   ushort  height,
   width,
   colors,
   bits;
   uintdata_size; 
   ubyte[1]data; 
   }

libraw_dcraw_make_mem_thumb() returns a pointer to this struct.
I need to create a char[] from the data and data_size members,
ideally without copying, to send to GdkPixbufLoader.write(char[]).

If I do this:
   libraw_processed_image_t *img;
   img = libraw_dcraw_make_mem_thumb();
   char[] buf = cast(char[]) img.data[];
   GdkPixbufLoader.write(buf); // Runtime error

buf.ptr == img.data.ptr and length of both arrays is 1.
If I try:
   buf.length = img.data_size;
buf is reallocated.

Any suggestions to make buf.ptr == img.data.ptr and
buf.length = img.data_size?

Thanks
ollie