On 01/06/2013 01:48 AM, MrOrdinaire wrote:
> My question is how this function declaration is written in D.
> int av_image_alloc(uint8_t *pointers[4], int linesizes[4],
> int w, int h, enum AVPixelFormat pix_fmt, int align);
1) No array is passed to a function as-is in C. Even though there seem
to be arrays of 4 elements above, they are both passed as pointers to
their first elements. (That 4 has no bearing at all.)
2) uint8_t *pointers[4] means an array of elements of type 'uint8_t*'.
3) int linesizes[4] means an array of ints.
4) uint8_t and friends are defined in the std.stdint module in Phobos.
5) enum should not be used in that signature in D.
6) align is a keyword and cannot be used.
This is the declaration of that function in D:
extern(C)
int av_image_alloc(uint8_t** pointers, int* linesizes,
int w, int h, AVPixelFormat pix_fmt, int alignment);
Here is a program that I used to test it:
import std.stdint;
extern(C)
{
enum AVPixelFormat
{
one, two
}
int av_image_alloc(uint8_t** pointers, int* linesizes,
int w, int h, AVPixelFormat pix_fmt, int alignment);
}
void main()
{
uint8_t ui0 = 7;
uint8_t ui1 = 8;
uint8_t*[] pointers = [ &ui0, &ui1 ];
// Ditto
int[] linesizes = [ 20, 30, 40 ];
int result = av_image_alloc(pointers.ptr, linesizes.ptr,
44, 55, AVPixelFormat.two, 100);
assert(result == 42);
}
I tested it with the following C file:
#include <stdint.h>
#include <assert.h>
enum AVPixelFormat
{
AVPixelFormat_one, AVPixelFormat_two
};
int av_image_alloc(uint8_t *pointers[4], int linesizes[4],
int w, int h, enum AVPixelFormat pix_fmt, int align)
{
assert(*pointers[0] == 7);
assert(*pointers[1] == 8);
assert(linesizes[0] == 20);
assert(linesizes[1] == 30);
assert(linesizes[2] == 40);
assert(w == 44);
assert(h == 55);
assert(pix_fmt == AVPixelFormat_two);
assert(align == 100);
return 42;
}
I compiled the C file like this:
$ gcc -c deneme.c
Then compiled the D program like this (note that the C .o was in a
different directory):
$ dmd ../c/deneme.o deneme.d
And ran it like this:
$ ./deneme
All assertions passed. Yay! :)
Ali
P.S. To prove the point that that 4 in the signature has no meaning, I
tested the C function also with the following C program:
int main()
{
uint8_t ui0 = 7;
uint8_t ui1 = 8;
// Deliberately 10 (not 4) to prove a point
uint8_t* pointers[10] = { &ui0, &ui1 };
// Ditto
int linesizes[10] = { 20, 30, 40 };
av_image_alloc(pointers, linesizes, 44, 55, AVPixelFormat_two, 100);
}
