Quick hack to create nodeid flags using block hashes

nodeid-flag.c

#include <ccan/crypto/sha256/sha256.h>
#include <ccan/err/err.h>
#include <ccan/opt/opt.h>
#include <ccan/short_types/short_types.h>
#include <ccan/str/hex/hex.h>
#include <stdio.h>
#include <assert.h>
#include <string.h>

int main(int argc, char *argv[])
{
	u8 nodeid[33];
	struct sha256_ctx sha_base;

	opt_register_noarg("--usage|--help|-h", opt_usage_and_exit,
			   "nodeid blockhash...\n"
			   "Calculates an RGB color combining nodeid and blockhash",
			   "Print this message");

	opt_parse(&argc, argv, opt_log_stderr_exit);
	if (argc < 3)
		opt_usage_and_exit(NULL);

	if (!hex_decode(argv[1], strlen(argv[1]), nodeid, sizeof(nodeid)))
		errx(1, "bad nodeid");

	/* Start by hashing node id */
	sha256_init(&sha_base);
	sha256_update(&sha_base, nodeid, sizeof(nodeid));

	for (size_t i = 2; i < argc; i++) {
		struct sha256_ctx sha = sha_base;
		struct sha256 res;
		u8 blockhash[32];
		if (!hex_decode(argv[i], strlen(argv[i]), blockhash, sizeof(blockhash)))
			errx(1, "bad blockhash %s", argv[i]);

		sha256_update(&sha, blockhash, sizeof(blockhash));
		sha256_done(&sha, &res);
		printf("%02x%02x%02x\n", res.u.u8[0], res.u.u8[1], res.u.u8[2]);
	}

	/* For example, block 807747 ... 807744 gives flag:
	   $ ~/devel/cvs/rustyjunk/nodeid-flag 024b9a1fa8e006f1e3937f65f66c408e6da8e1ca728ea43222a7381df1cc449605 00000000000000000001f305cf8a3ae017a4e50468e981516b7c976a78fc5055 000000000000000000034934f36ef2518fbe17b53922cddd6dc849d789f06bf3 000000000000000000048abe38b874abb9a17c1f6cf5113a6e80e9af79743003 000000000000000000051b87289ac16d2a9cb0227602faf1b47e546037b45390
	   3d7de3
	   d3a7c1
	   98d552
	   fe8ea3
	*/
	return 0;
}