Example to add "Data" type data about c-capnproto HOT 3 CLOSED

@0xed2b3b98b3eb515b;
struct Msg {
	data @0: Data;
}

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <assert.h>
#include <unistd.h>

#include "data.capnp.h"

int main(int argc, char **argv)
{
	uint8_t data[] = { 0x12, 0x34, 0x00, 0x56, 0x78 };

	/* create capn + capn segment */
	struct capn c;
	capn_init_malloc(&c);
	capn_ptr cr = capn_root(&c);
	struct capn_segment *cs = cr.seg;

	struct Msg msg;

	/* capn_list8 & capn_data are essentially the same (they both just contain a single capn_ptr)
	 * usage is slightly convoluted sadly */
	capn_list8 list8 = capn_new_list8(cs, sizeof(data));
	capn_setv8(list8, 0, data, sizeof(data));
	msg.data.p = list8.p;

	/* encode & set as root */
	Msg_ptr pp = new_Msg(cs);
	write_Msg(&msg, pp);
	assert(capn_setp(capn_root(&c), 0, pp.p) == 0);

	uint8_t obuf[4096];
	size_t sz = capn_write_mem(&c, obuf, sizeof(obuf), 0);
	capn_free(&c);

	write(1, obuf, sz);
	return 0;
}

$ ./datatest | capnp decode data.capnp Msg
(data = "\x124\x00Vx")