bitcoin_tx: bitcoin_txid_from_hex helper.

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

bitcoin_tx.c

@@ -287,3 +287,27 @@ struct bitcoin_tx *bitcoin_tx_from_file(const tal_t *ctx,
 
 	return tx;
 }
+
+/* <sigh>.  Bitcoind represents hashes as little-endian for RPC.  This didn't
+ * stick for blockids (everyone else uses big-endian, eg. block explorers),
+ * but it did stick for txids. */
+static void reverse_bytes(u8 *arr, size_t len)
+{
+	unsigned int i;
+
+	for (i = 0; i < len / 2; i++) {
+		unsigned char tmp = arr[i];
+		arr[i] = arr[len - 1 - i];
+		arr[len - 1 - i] = tmp;
+	}
+}
+
+bool bitcoin_txid_from_hex(const char *hexstr, size_t hexstr_len,
+			   struct sha256_double *txid)
+{
+	if (!hex_decode(hexstr, hexstr_len, txid, sizeof(*txid)))
+		return false;
+	reverse_bytes(txid->sha.u.u8, sizeof(txid->sha.u.u8));
+	return true;
+}
+	

bitcoin_tx.h

@@ -50,4 +50,8 @@ struct bitcoin_tx *bitcoin_tx(const tal_t *ctx, varint_t input_count,
 struct bitcoin_tx *bitcoin_tx_from_file(const tal_t *ctx,
 					const char *filename);
 
+/* Parse hex string to get txid (reversed, a-la bitcoind). */
+bool bitcoin_txid_from_hex(const char *hexstr, size_t hexstr_len,
+			   struct sha256_double *txid);
+
 #endif /* LIGHTNING_BITCOIN_TX_H */

open-channel.c

@@ -14,6 +14,7 @@
 #include "pkt.h"
 #include "bitcoin_script.h"
 #include "bitcoin_address.h"
+#include "bitcoin_tx.h"
 #include "pubkey.h"
 #include "shadouble.h"
 #include <openssl/ec.h>
@@ -40,20 +41,6 @@ static void opt_show_bits(char buf[OPT_SHOW_LEN], const u64 *bits)
 	opt_show_ulonglongval_si(buf, &ll);
 }
 
-/* <sigh>.  Bitcoind represents hashes as little-endian for RPC.  This didn't
- * stick for blockids (everyone else uses big-endian, eg. block explorers),
- * but it did stick for txids. */
-static void reverse_bytes(u8 *arr, size_t len)
-{
-	unsigned int i;
-
-	for (i = 0; i < len / 2; i++) {
-		unsigned char tmp = arr[i];
-		arr[i] = arr[len - 1 - i];
-		arr[len - 1 - i] = tmp;
-	}
-}
-
 static BitcoinInput *parse_anchor_input(const tal_t *ctx, const char *spec)
 {
 	BitcoinInput *in = tal(ctx, BitcoinInput);
@@ -68,9 +55,8 @@ static BitcoinInput *parse_anchor_input(const tal_t *ctx, const char *spec)
 	if (!slash)
 		errx(1, "Expected / in <txid>/<num>/<satoshis>/<hexscript>");
 
-	if (!hex_decode(spec, slash - spec, &txid, sizeof(txid)))
+	if (!bitcoin_txid_from_hex(spec, slash - spec, &txid))
 		errx(1, "Expected 256-bit hex txid before /");
-	reverse_bytes(txid.sha.u.u8, sizeof(txid.sha.u.u8));
 	in->txid = sha256_to_proto(in, &txid.sha);
 
 	in->output = l = strtol(slash + 1, &end, 10);