test-cli/txid-of: simple helper to get txid.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

.gitignore

@@ -21,6 +21,7 @@ update-channel-accept
 update-channel-signature
 update-channel-complete
 create-commit-tx
+txid-of
 ccan/tools/configurator/configurator
 libsecp256k1.a
 libsecp256k1.la

Makefile

@@ -8,7 +8,7 @@ FEATURES := -DHAS_CSV=1 -DALPHA_TXSTYLE=1 -DUSE_SCHNORR=1
 # Bitcoin uses DER for signatures
 #FEATURES := -DSCRIPTS_USE_DER
 
-PROGRAMS := test-cli/open-channel test-cli/open-anchor-scriptsigs test-cli/open-commit-sig test-cli/check-commit-sig test-cli/check-anchor-scriptsigs test-cli/get-anchor-depth test-cli/create-steal-tx test-cli/create-commit-spend-tx test-cli/close-channel test-cli/create-close-tx test-cli/update-channel test-cli/update-channel-accept test-cli/update-channel-signature test-cli/update-channel-complete test-cli/create-commit-tx
+PROGRAMS := test-cli/open-channel test-cli/open-anchor-scriptsigs test-cli/open-commit-sig test-cli/check-commit-sig test-cli/check-anchor-scriptsigs test-cli/get-anchor-depth test-cli/create-steal-tx test-cli/create-commit-spend-tx test-cli/close-channel test-cli/create-close-tx test-cli/update-channel test-cli/update-channel-accept test-cli/update-channel-signature test-cli/update-channel-complete test-cli/create-commit-tx test-cli/txid-of
 
 BITCOIN_OBJS := bitcoin/address.o bitcoin/base58.o bitcoin/pubkey.o bitcoin/script.o bitcoin/shadouble.o bitcoin/signature.o bitcoin/tx.o
 

bitcoin/tx.c

@@ -503,6 +503,14 @@ bool bitcoin_txid_from_hex(const char *hexstr, size_t hexstr_len,
 	return true;
 }
 
+bool bitcoin_txid_to_hex(const struct sha256_double *txid,
+			 char *hexstr, size_t hexstr_len)
+{
+	struct sha256_double rev = *txid;
+	reverse_bytes(rev.sha.u.u8, sizeof(rev.sha.u.u8));
+	return hex_encode(&rev, sizeof(rev), hexstr, hexstr_len);
+}
+
 static bool write_input_amounts(int fd, const struct bitcoin_tx *tx)
 {
 	/* Alpha required input amounts, so append them */

bitcoin/tx.h

@@ -64,4 +64,8 @@ bool bitcoin_tx_write(int fd, const struct bitcoin_tx *tx);
 bool bitcoin_txid_from_hex(const char *hexstr, size_t hexstr_len,
 			   struct sha256_double *txid);
 
+/* Get hex string of txid (reversed, a-la bitcoind). */
+bool bitcoin_txid_to_hex(const struct sha256_double *txid,
+			 char *hexstr, size_t hexstr_len);
+
 #endif /* LIGHTNING_BITCOIN_TX_H */

test-cli/txid-of.c

@@ -0,0 +1,43 @@
+#include <ccan/crypto/shachain/shachain.h>
+#include <ccan/read_write_all/read_write_all.h>
+#include <ccan/short_types/short_types.h>
+#include <ccan/tal/tal.h>
+#include <ccan/opt/opt.h>
+#include <ccan/str/hex/hex.h>
+#include <ccan/err/err.h>
+#include "bitcoin/tx.h"
+#include <unistd.h>
+
+int main(int argc, char *argv[])
+{
+	const tal_t *ctx = tal_arr(NULL, char, 0);
+	struct bitcoin_tx *tx;
+	struct sha256_double txid;
+	char str[hex_str_size(sizeof(txid))];
+
+	err_set_progname(argv[0]);
+
+	/* FIXME: Take update.pbs to adjust channel */
+	opt_register_noarg("--help|-h", opt_usage_and_exit,
+			   "<tx>\n"
+			   "Print txid of the transaction in the file",
+			   "Print this message.");
+
+ 	opt_parse(&argc, argv, opt_log_stderr_exit);
+
+	if (argc != 2)
+		opt_usage_exit_fail("Expected 1 argument");
+
+	tx = bitcoin_tx_from_file(ctx, argv[1]);
+	bitcoin_txid(tx, &txid);
+
+	if (!bitcoin_txid_to_hex(&txid, str, sizeof(str)))
+		abort();
+
+	/* Print it out. */
+	if (!write_all(STDOUT_FILENO, str, strlen(str)))
+		err(1, "Writing out txid");
+
+	tal_free(ctx);
+	return 0;
+}