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digitalmars.D.learn - Fixed Length Array Syntax in extern(C) Function Signatures

reply =?UTF-8?B?Ik5vcmRsw7Z3Ig==?= <per.nordlow gmail.com> writes:
Given

     extern(C):

     struct AVFrame
     {
         uint8_t*[AV_NUM_DATA_POINTERS] data;
         int[AV_NUM_DATA_POINTERS] linesize;
         int width, height;
         ...
     }

     void av_image_copy(ubyte *[4] dst_data, int[4] dst_linesizes,
                        const ubyte *[4] src_data, const int[4] 
src_linesizes,
                        AVPixelFormat pix_fmt, int width, int 
height)


will `dst_data` will be C-ABI-fed to `image_copy()` as a C-style 
single pointer in constrast to what happens in D which calls it 
as fixed-size (4) array of ubyte-pointers?

Further, is it correct to use it in D as

     void copyVideo(const AVFrame* source,
                    AVFrame* target)
     {
         av_image_copy(target.data[0 .. 4], target.linesize[0 .. 
4],
                       source.data[0 .. 4], source.linesize[0 .. 
4],
                       format, source.width, source.height);
     }

?

It compiles without warnings, at least. I haven't been able to 
test it yet, though.
Jul 09 2015
next sibling parent =?UTF-8?B?Ik5vcmRsw7Z3Ig==?= <per.nordlow gmail.com> writes:
On Thursday, 9 July 2015 at 15:19:41 UTC, Nordlöw wrote:

         uint8_t*[AV_NUM_DATA_POINTERS] data;
         int[AV_NUM_DATA_POINTERS] linesize;


Forgot

     enum AV_NUM_DATA_POINTERS = 8;
Jul 09 2015
prev sibling parent reply Timon Gehr <timon.gehr gmx.ch> writes:
On 07/09/2015 05:19 PM, "Nordlöw" wrote:

 Given

      extern(C):

      struct AVFrame
      {
          uint8_t*[AV_NUM_DATA_POINTERS] data;
          int[AV_NUM_DATA_POINTERS] linesize;
          int width, height;
          ...
      }

      void av_image_copy(ubyte *[4] dst_data, int[4] dst_linesizes,
                         const ubyte *[4] src_data, const int[4]
 src_linesizes,
                         AVPixelFormat pix_fmt, int width, int height)


 will `dst_data` will be C-ABI-fed to `image_copy()` as a C-style single
 pointer in constrast to what happens in D which calls it as fixed-size
 (4) array of ubyte-pointers?


No. You'll need explicit pass by reference on the D side.
Jul 09 2015
parent reply "Per =?UTF-8?B?Tm9yZGzDtnci?= <per.nordlow gmail.com> writes:
On Thursday, 9 July 2015 at 16:12:27 UTC, Timon Gehr wrote:

 No. You'll need explicit pass by reference on the D side.


So, how should I modify my call to `image_copy` with respect to 
the four first parameters?
Jul 09 2015
parent reply "Alex Parrill" <initrd.gz gmail.com> writes:
On Thursday, 9 July 2015 at 17:11:36 UTC, Per Nordlöw wrote:

 On Thursday, 9 July 2015 at 16:12:27 UTC, Timon Gehr wrote:

 No. You'll need explicit pass by reference on the D side.


 So, how should I modify my call to `image_copy` with respect to 
 the four first parameters?


In C, array parameters are the same as pointers; i.e. `foo(T[] 
arg)` is the same as `foo(T* arg)` [1].

You should just be able to replace `[4]` with `*` in the 
arguments.

[1]: http://stackoverflow.com/a/5573741/646619
Jul 09 2015
parent reply "Mike Parker" <aldacron gmail.com> writes:
On Thursday, 9 July 2015 at 17:42:33 UTC, Alex Parrill wrote:

 On Thursday, 9 July 2015 at 17:11:36 UTC, Per Nordlöw wrote:

 On Thursday, 9 July 2015 at 16:12:27 UTC, Timon Gehr wrote:

 No. You'll need explicit pass by reference on the D side.


 So, how should I modify my call to `image_copy` with respect 
 to the four first parameters?


 In C, array parameters are the same as pointers; i.e. `foo(T[] 
 arg)` is the same as `foo(T* arg)` [1].

 You should just be able to replace `[4]` with `*` in the 
 arguments.

 [1]: http://stackoverflow.com/a/5573741/646619


Static arrays in C function parameter lists should be declared as 
ref on the D side. See "Passinbg D Array Arguments to C 
Functions" at [1]. So the function declaration above in D should 
be:

void av_image_copy(ref ubyte *[4] dst_data, ref int[4] 
dst_linesizes,
                        ref const ubyte *[4] src_data, ref const 
int[4] src_linesizes,
                        AVPixelFormat pix_fmt, int width, int 
height)

[1]http://dlang.org/interfaceToC.html
Jul 09 2015
next sibling parent =?UTF-8?B?Ik5vcmRsw7Z3Ig==?= <per.nordlow gmail.com> writes:
On Friday, 10 July 2015 at 03:18:23 UTC, Mike Parker wrote:

 You should just be able to replace `[4]` with `*` in the 
 arguments.


 [1]http://dlang.org/interfaceToC.html


Great!

One more thing: How shall my call to `avg_image_copy()` (from D) 
look then? Is the slicing syntax `[0 .. 4]` I use above as

     av_image_copy(target.data[0 .. 4], target.linesize[0 .. 4],
                   source.data[0 .. 4], source.linesize[0 .. 4],
                   format, source.width, source.height);

the best way?
Jul 10 2015
prev sibling parent reply "Per =?UTF-8?B?Tm9yZGzDtnci?= <per.nordlow gmail.com> writes:
On Friday, 10 July 2015 at 03:18:23 UTC, Mike Parker wrote:

 [1]http://dlang.org/interfaceToC.html


Is there any tool out there that automatically creates D wrappers 
from C headers`?
Jul 10 2015
parent reply "Andrea Fontana" <nospam example.com> writes:
On Friday, 10 July 2015 at 08:42:06 UTC, Per Nordlöw wrote:

 On Friday, 10 July 2015 at 03:18:23 UTC, Mike Parker wrote:

 [1]http://dlang.org/interfaceToC.html


 Is there any tool out there that automatically creates D 
 wrappers from C headers`?


https://github.com/jacob-carlborg/dstep ?
Jul 10 2015
parent "Per =?UTF-8?B?Tm9yZGzDtnci?= <per.nordlow gmail.com> writes:
On Friday, 10 July 2015 at 08:54:57 UTC, Andrea Fontana wrote:

 Is there any tool out there that automatically creates D 
 wrappers from C headers`?


 https://github.com/jacob-carlborg/dstep ?


Great! I'll try that!
Jul 10 2015