bitcoin: create new wrapper type bitcoin_txid, log backward endianness.

It's just a sha256_double, but importantly when we convert it to a
string (in type_to_string, which is used in logging) we use
bitcoin_txid_to_hex() so it's reversed as people expect.

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

bitcoin/block.c

@@ -41,11 +41,17 @@ struct bitcoin_block *bitcoin_block_from_hex(const tal_t *ctx,
 bool bitcoin_blkid_from_hex(const char *hexstr, size_t hexstr_len,
 			    struct sha256_double *blockid)
 {
-	return bitcoin_txid_from_hex(hexstr, hexstr_len, blockid);
+	struct bitcoin_txid fake_txid;
+	if (!bitcoin_txid_from_hex(hexstr, hexstr_len, &fake_txid))
+		return false;
+	*blockid = fake_txid.shad;
+	return true;
 }
 
 bool bitcoin_blkid_to_hex(const struct sha256_double *blockid,
 			  char *hexstr, size_t hexstr_len)
 {
-	return bitcoin_txid_to_hex(blockid, hexstr, hexstr_len);
+	struct bitcoin_txid fake_txid;
+	fake_txid.shad = *blockid;
+	return bitcoin_txid_to_hex(&fake_txid, hexstr, hexstr_len);
 }

bitcoin/test/run-tx-encode.c

@@ -38,7 +38,8 @@ int main(void)
 	assert(tal_count(tx->input) == 1);
 	assert(tal_count(tx->output) == 1);
 
-	reverse_bytes(tx->input[0].txid.sha.u.u8, sizeof(tx->input[0].txid));
+	reverse_bytes(tx->input[0].txid.shad.sha.u.u8,
+		      sizeof(tx->input[0].txid));
 	hexeq(&tx->input[0].txid, sizeof(tx->input[0].txid),
 	      "1db36e1306dfc810ea63f0cf866d475cce4e9261a5e8d1581f0d1dc485f4beb5");
 	assert(tx->input[0].index == 0);

bitcoin/tx.c

@@ -276,13 +276,13 @@ size_t measure_tx_cost(const struct bitcoin_tx *tx)
 	return non_witness_len * 4 + witness_len;
 }
 
-void bitcoin_txid(const struct bitcoin_tx *tx, struct sha256_double *txid)
+void bitcoin_txid(const struct bitcoin_tx *tx, struct bitcoin_txid *txid)
 {
 	struct sha256_ctx ctx = SHA256_INIT;
 
 	/* For TXID, we never use extended form. */
 	push_tx(tx, push_sha, &ctx, false);
-	sha256_double_done(&ctx, txid);
+	sha256_double_done(&ctx, &txid->shad);
 }
 
 struct bitcoin_tx *bitcoin_tx(const tal_t *ctx, varint_t input_count,
@@ -336,7 +336,7 @@ static void pull_input(const tal_t *ctx, const u8 **cursor, size_t *max,
 		       struct bitcoin_tx_input *input)
 {
 	u64 script_len;
-	pull_sha256_double(cursor, max, &input->txid);
+	pull_sha256_double(cursor, max, &input->txid.shad);
 	input->index = pull_le32(cursor, max);
 	script_len = pull_length(cursor, max);
 	if (script_len)
@@ -460,9 +460,7 @@ fail:
 	return NULL;
 }
 
-/* <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. */
+/* <sigh>.  Bitcoind represents hashes as little-endian for RPC. */
 static void reverse_bytes(u8 *arr, size_t len)
 {
 	unsigned int i;
@@ -475,18 +473,18 @@ static void reverse_bytes(u8 *arr, size_t len)
 }
 
 bool bitcoin_txid_from_hex(const char *hexstr, size_t hexstr_len,
-			   struct sha256_double *txid)
+			   struct bitcoin_txid *txid)
 {
 	if (!hex_decode(hexstr, hexstr_len, txid, sizeof(*txid)))
 		return false;
-	reverse_bytes(txid->sha.u.u8, sizeof(txid->sha.u.u8));
+	reverse_bytes(txid->shad.sha.u.u8, sizeof(txid->shad.sha.u.u8));
 	return true;
 }
 
-bool bitcoin_txid_to_hex(const struct sha256_double *txid,
+bool bitcoin_txid_to_hex(const struct bitcoin_txid *txid,
 			 char *hexstr, size_t hexstr_len)
 {
-	struct sha256_double rev = *txid;
+	struct sha256_double rev = txid->shad;
 	reverse_bytes(rev.sha.u.u8, sizeof(rev.sha.u.u8));
 	return hex_encode(&rev, sizeof(rev), hexstr, hexstr_len);
 }
@@ -499,4 +497,13 @@ static char *fmt_bitcoin_tx(const tal_t *ctx, const struct bitcoin_tx *tx)
 	return s;
 }
 
+static char *fmt_bitcoin_txid(const tal_t *ctx, const struct bitcoin_txid *txid)
+{
+	char *hexstr = tal_arr(ctx, char, hex_str_size(sizeof(*txid)));
+
+	bitcoin_txid_to_hex(txid, hexstr, hex_str_size(sizeof(*txid)));
+	return hexstr;
+}
+
 REGISTER_TYPE_TO_STRING(bitcoin_tx, fmt_bitcoin_tx);
+REGISTER_TYPE_TO_STRING(bitcoin_txid, fmt_bitcoin_txid);

bitcoin/tx.h

@@ -7,6 +7,10 @@
 #include <ccan/short_types/short_types.h>
 #include <ccan/tal/tal.h>
 
+struct bitcoin_txid {
+	struct sha256_double shad;
+};
+
 struct bitcoin_tx {
 	u32 version;
 	struct bitcoin_tx_input *input;
@@ -20,7 +24,7 @@ struct bitcoin_tx_output {
 };
 
 struct bitcoin_tx_input {
-	struct sha256_double txid;
+	struct bitcoin_txid txid;
 	u32 index; /* output number referred to by above */
 	u8 *script;
 	u32 sequence_number;
@@ -34,7 +38,7 @@ struct bitcoin_tx_input {
 
 
 /* SHA256^2 the tx: simpler than sha256_tx */
-void bitcoin_txid(const struct bitcoin_tx *tx, struct sha256_double *txid);
+void bitcoin_txid(const struct bitcoin_tx *tx, struct bitcoin_txid *txid);
 
 /* Useful for signature code. */
 void sha256_tx_for_sig(struct sha256_double *h, const struct bitcoin_tx *tx,
@@ -57,10 +61,10 @@ struct bitcoin_tx *bitcoin_tx_from_hex(const tal_t *ctx, const char *hex,
 
 /* 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);
+			   struct bitcoin_txid *txid);
 
 /* Get hex string of txid (reversed, a-la bitcoind). */
-bool bitcoin_txid_to_hex(const struct sha256_double *txid,
+bool bitcoin_txid_to_hex(const struct bitcoin_txid *txid,
 			 char *hexstr, size_t hexstr_len);
 
 /* Internal de-linearization functions. */

channeld/channel.c

@@ -2351,7 +2351,7 @@ static void init_channel(struct peer *peer)
 	u16 funding_txout;
 	u64 local_msatoshi;
 	struct pubkey funding_pubkey[NUM_SIDES];
-	struct sha256_double funding_txid;
+	struct bitcoin_txid funding_txid;
 	enum side funder;
 	enum htlc_state *hstates;
 	struct fulfilled_htlc *fulfilled;

channeld/channel_wire.csv

@@ -7,7 +7,7 @@ channel_normal_operation,11001
 # Begin!  (passes gossipd-client fd)
 channel_init,1000
 channel_init,,chain_hash,struct sha256_double
-channel_init,,funding_txid,struct sha256_double
+channel_init,,funding_txid,struct bitcoin_txid
 channel_init,,funding_txout,u16
 channel_init,,funding_satoshi,u64
 channel_init,,our_config,struct channel_config

channeld/commit_tx.c

@@ -86,7 +86,7 @@ static void add_received_htlc_out(struct bitcoin_tx *tx, size_t n,
 }
 
 struct bitcoin_tx *commit_tx(const tal_t *ctx,
-			     const struct sha256_double *funding_txid,
+			     const struct bitcoin_txid *funding_txid,
 			     unsigned int funding_txout,
 			     u64 funding_satoshis,
 			     enum side funder,

channeld/commit_tx.h

@@ -7,7 +7,6 @@
 #include <common/initial_commit_tx.h>
 
 struct keyset;
-struct sha256_double;
 
 /**
  * commit_tx_num_untrimmed: how many of these htlc outputs will commit tx have?
@@ -43,7 +42,7 @@ size_t commit_tx_num_untrimmed(const struct htlc **htlcs,
  * transaction, so we carefully use the terms "self" and "other" here.
  */
 struct bitcoin_tx *commit_tx(const tal_t *ctx,
-			     const struct sha256_double *funding_txid,
+			     const struct bitcoin_txid *funding_txid,
 			     unsigned int funding_txout,
 			     u64 funding_satoshis,
 			     enum side funder,

channeld/full_channel.c

@@ -20,7 +20,7 @@
 #include <string.h>
 
 struct channel *new_channel(const tal_t *ctx,
-			    const struct sha256_double *funding_txid,
+			    const struct bitcoin_txid *funding_txid,
 			    unsigned int funding_txout,
 			    u64 funding_satoshis,
 			    u64 local_msatoshi,
@@ -178,7 +178,7 @@ static void add_htlcs(struct bitcoin_tx ***txs,
 		      enum side side)
 {
 	size_t i, n;
-	struct sha256_double txid;
+	struct bitcoin_txid txid;
 	u32 feerate_per_kw = channel->view[side].feerate_per_kw;
 
 	/* Get txid of commitment transaction */

channeld/full_channel.h

@@ -26,7 +26,7 @@
  * Returns state, or NULL if malformed.
  */
 struct channel *new_channel(const tal_t *ctx,
-			    const struct sha256_double *funding_txid,
+			    const struct bitcoin_txid *funding_txid,
 			    unsigned int funding_txout,
 			    u64 funding_satoshis,
 			    u64 local_msatoshi,

channeld/test/run-full_channel.c

@@ -20,26 +20,14 @@
 
 const void *trc;
 
-static struct sha256 sha256_from_hex(const char *hex)
-{
-	struct sha256 sha256;
-	if (strstarts(hex, "0x"))
-		hex += 2;
-	if (!hex_decode(hex, strlen(hex), &sha256, sizeof(sha256)))
-		abort();
-	return sha256;
-}
-
 /* bitcoind loves its backwards txids! */
-static struct sha256_double txid_from_hex(const char *hex)
+static struct bitcoin_txid txid_from_hex(const char *hex)
 {
-	struct sha256_double sha256;
-	struct sha256 rev = sha256_from_hex(hex);
-	size_t i;
+	struct bitcoin_txid txid;
 
-	for (i = 0; i < sizeof(rev); i++)
-		sha256.sha.u.u8[sizeof(sha256) - 1 - i] = rev.u.u8[i];
-	return sha256;
+	if (!bitcoin_txid_from_hex(hex, strlen(hex), &txid))
+		abort();
+	return txid;
 }
 
 static struct bitcoin_tx *tx_from_hex(const tal_t *ctx, const char *hex)
@@ -326,7 +314,7 @@ static void update_feerate(struct channel *channel, u32 feerate)
 int main(void)
 {
 	tal_t *tmpctx = tal_tmpctx(NULL);
-	struct sha256_double funding_txid;
+	struct bitcoin_txid funding_txid;
 	/* We test from both sides. */
 	struct channel *lchannel, *rchannel;
 	u64 funding_amount_satoshi;

closingd/closing.c

@@ -27,7 +27,7 @@ static struct bitcoin_tx *close_tx(const tal_t *ctx,
 				   struct crypto_state *cs,
 				   const struct channel_id *channel_id,
 				   u8 *scriptpubkey[NUM_SIDES],
-				   const struct sha256_double *funding_txid,
+				   const struct bitcoin_txid *funding_txid,
 				   unsigned int funding_txout,
 				   u64 funding_satoshi,
 				   const u64 satoshi_out[NUM_SIDES],
@@ -155,7 +155,7 @@ int main(int argc, char *argv[])
 	u8 *msg;
 	struct privkey seed;
 	struct pubkey funding_pubkey[NUM_SIDES];
-	struct sha256_double funding_txid;
+	struct bitcoin_txid funding_txid;
 	u16 funding_txout;
 	u64 funding_satoshi, satoshi_out[NUM_SIDES];
 	u64 our_dust_limit;

closingd/closing_wire.csv

@@ -5,7 +5,7 @@ closing_init,2001
 closing_init,,crypto_state,struct crypto_state
 closing_init,,gossip_index,u64
 closing_init,,seed,struct privkey
-closing_init,,funding_txid,struct sha256_double
+closing_init,,funding_txid,struct bitcoin_txid
 closing_init,,funding_txout,u16
 closing_init,,funding_satoshi,u64
 closing_init,,remote_fundingkey,struct pubkey

common/close_tx.c

@@ -7,7 +7,7 @@
 struct bitcoin_tx *create_close_tx(const tal_t *ctx,
 				   const u8 *our_script,
 				   const u8 *their_script,
-				   const struct sha256_double *anchor_txid,
+				   const struct bitcoin_txid *anchor_txid,
 				   unsigned int anchor_index,
 				   u64 anchor_satoshis,
 				   uint64_t to_us, uint64_t to_them,

common/close_tx.h

@@ -4,7 +4,6 @@
 #include <ccan/short_types/short_types.h>
 #include <ccan/tal/tal.h>
 
-struct sha256_double;
 struct pubkey;
 
 /* Create close tx to spend the anchor tx output; doesn't fill in
@@ -12,7 +11,7 @@ struct pubkey;
 struct bitcoin_tx *create_close_tx(const tal_t *ctx,
 				   const u8 *our_script,
 				   const u8 *their_script,
-				   const struct sha256_double *anchor_txid,
+				   const struct bitcoin_txid *anchor_txid,
 				   unsigned int anchor_index,
 				   u64 anchor_satoshis,
 				   uint64_t to_us, uint64_t to_them,

common/funding_tx.h

@@ -8,7 +8,6 @@ struct bitcoin_tx;
 struct ext_key;
 struct privkey;
 struct pubkey;
-struct sha256_double;
 struct utxo;
 
 /**

common/htlc_tx.c

@@ -5,7 +5,7 @@
 #include <common/keyset.h>
 
 static struct bitcoin_tx *htlc_tx(const tal_t *ctx,
-				  const struct sha256_double *commit_txid,
+				  const struct bitcoin_txid *commit_txid,
 				  unsigned int commit_output_number,
 				  u64 msatoshi,
 				  u16 to_self_delay,
@@ -72,7 +72,7 @@ static struct bitcoin_tx *htlc_tx(const tal_t *ctx,
 }
 
 struct bitcoin_tx *htlc_success_tx(const tal_t *ctx,
-				   const struct sha256_double *commit_txid,
+				   const struct bitcoin_txid *commit_txid,
 				   unsigned int commit_output_number,
 				   u64 htlc_msatoshi,
 				   u16 to_self_delay,
@@ -117,7 +117,7 @@ void htlc_success_tx_add_witness(struct bitcoin_tx *htlc_success,
 }
 
 struct bitcoin_tx *htlc_timeout_tx(const tal_t *ctx,
-				   const struct sha256_double *commit_txid,
+				   const struct bitcoin_txid *commit_txid,
 				   unsigned int commit_output_number,
 				   u64 htlc_msatoshi,
 				   u32 cltv_expiry,

common/htlc_tx.h

@@ -6,7 +6,6 @@
 struct keyset;
 struct preimage;
 struct pubkey;
-struct sha256_double;
 
 static inline u64 htlc_timeout_fee(u32 feerate_per_kw)
 {
@@ -35,7 +34,7 @@ static inline u64 htlc_success_fee(u32 feerate_per_kw)
 /* Create HTLC-success tx to spend a received HTLC commitment tx
  * output; doesn't fill in input witness. */
 struct bitcoin_tx *htlc_success_tx(const tal_t *ctx,
-				   const struct sha256_double *commit_txid,
+				   const struct bitcoin_txid *commit_txid,
 				   unsigned int commit_output_number,
 				   u64 htlc_msatoshi,
 				   u16 to_self_delay,
@@ -55,7 +54,7 @@ void htlc_success_tx_add_witness(struct bitcoin_tx *htlc_success,
 /* Create HTLC-timeout tx to spend an offered HTLC commitment tx
  * output; doesn't fill in input witness. */
 struct bitcoin_tx *htlc_timeout_tx(const tal_t *ctx,
-				   const struct sha256_double *commit_txid,
+				   const struct bitcoin_txid *commit_txid,
 				   unsigned int commit_output_number,
 				   u64 htlc_msatoshi,
 				   u32 cltv_expiry,

common/initial_channel.c

@@ -8,7 +8,7 @@
 #include <inttypes.h>
 
 struct channel *new_initial_channel(const tal_t *ctx,
-				    const struct sha256_double *funding_txid,
+				    const struct bitcoin_txid *funding_txid,
 				    unsigned int funding_txout,
 				    u64 funding_satoshis,
 				    u64 local_msatoshi,

common/initial_channel.h

@@ -28,7 +28,7 @@ struct channel_view {
 
 struct channel {
 	/* Funding txid and output. */
-	struct sha256_double funding_txid;
+	struct bitcoin_txid funding_txid;
 	unsigned int funding_txout;
 
 	/* Keys used to spend funding tx. */
@@ -142,7 +142,7 @@ static inline u16 to_self_delay(const struct channel *channel, enum side side)
  * Returns channel, or NULL if malformed.
  */
 struct channel *new_initial_channel(const tal_t *ctx,
-				    const struct sha256_double *funding_txid,
+				    const struct bitcoin_txid *funding_txid,
 				    unsigned int funding_txout,
 				    u64 funding_satoshis,
 				    u64 local_msatoshi,

common/initial_commit_tx.c

@@ -55,7 +55,7 @@ u8 *to_self_wscript(const tal_t *ctx,
 }
 
 struct bitcoin_tx *initial_commit_tx(const tal_t *ctx,
-				     const struct sha256_double *funding_txid,
+				     const struct bitcoin_txid *funding_txid,
 				     unsigned int funding_txout,
 				     u64 funding_satoshis,
 				     enum side funder,

common/initial_commit_tx.h

@@ -6,7 +6,6 @@
 #include <common/htlc.h>
 
 struct keyset;
-struct sha256_double;
 
 /* BOLT #3:
  *
@@ -67,7 +66,7 @@ static inline u64 commit_tx_base_fee(u32 feerate_per_kw,
  * transaction, so we carefully use the terms "self" and "other" here.
  */
 struct bitcoin_tx *initial_commit_tx(const tal_t *ctx,
-				     const struct sha256_double *funding_txid,
+				     const struct bitcoin_txid *funding_txid,
 				     unsigned int funding_txout,
 				     u64 funding_satoshis,
 				     enum side funder,

common/type_to_string.h

@@ -9,6 +9,7 @@
 union printable_types {
 	const struct pubkey *pubkey;
 	const struct sha256_double *sha256_double;
+	const struct bitcoin_txid *bitcoin_txid;
 	const struct sha256 *sha256;
 	const struct ripemd160 *ripemd160;
 	const struct rel_locktime *rel_locktime;

common/utxo.c

@@ -3,7 +3,7 @@
 
 void towire_utxo(u8 **pptr, const struct utxo *utxo)
 {
-	towire_sha256_double(pptr, &utxo->txid);
+	towire_bitcoin_txid(pptr, &utxo->txid);
 	towire_u32(pptr, utxo->outnum);
 	towire_u64(pptr, utxo->amount);
 	towire_u32(pptr, utxo->keyindex);
@@ -12,7 +12,7 @@ void towire_utxo(u8 **pptr, const struct utxo *utxo)
 
 void fromwire_utxo(const u8 **ptr, size_t *max, struct utxo *utxo)
 {
-	fromwire_sha256_double(ptr, max, &utxo->txid);
+	fromwire_bitcoin_txid(ptr, max, &utxo->txid);
 	utxo->outnum = fromwire_u32(ptr, max);
 	utxo->amount = fromwire_u64(ptr, max);
 	utxo->keyindex = fromwire_u32(ptr, max);

common/utxo.h

@@ -1,13 +1,13 @@
 #ifndef LIGHTNING_COMMON_UTXO_H
 #define LIGHTNING_COMMON_UTXO_H
 #include "config.h"
-#include <bitcoin/shadouble.h>
+#include <bitcoin/tx.h>
 #include <ccan/short_types/short_types.h>
 #include <ccan/tal/tal.h>
 #include <stdbool.h>
 
 struct utxo {
-	struct sha256_double txid;
+	struct bitcoin_txid txid;
 	u32 outnum;
 	u64 amount;
 	u32 keyindex;

lightningd/chaintopology.c

@@ -43,7 +43,7 @@ static void add_tx_to_block(struct block *b,
 }
 
 static bool we_broadcast(const struct chain_topology *topo,
-			 const struct sha256_double *txid)
+			 const struct bitcoin_txid *txid)
 {
 	const struct outgoing_tx *otx;
 
@@ -74,7 +74,7 @@ static void connect_block(struct chain_topology *topo,
 	/* Now we see if any of those txs are interesting. */
 	for (i = 0; i < tal_count(b->full_txs); i++) {
 		const struct bitcoin_tx *tx = b->full_txs[i];
-		struct sha256_double txid;
+		struct bitcoin_txid txid;
 		size_t j;
 
 		/* Tell them if it spends a txo we care about. */
@@ -108,12 +108,12 @@ static void connect_block(struct chain_topology *topo,
 }
 
 static const struct bitcoin_tx *tx_in_block(const struct block *b,
-					    const struct sha256_double *txid)
+					    const struct bitcoin_txid *txid)
 {
 	size_t i, n = tal_count(b->txs);
 
 	for (i = 0; i < n; i++) {
-		struct sha256_double this_txid;
+		struct bitcoin_txid this_txid;
 		bitcoin_txid(b->txs[i], &this_txid);
 		if (structeq(&this_txid, txid))
 			return b->txs[i];
@@ -123,7 +123,7 @@ static const struct bitcoin_tx *tx_in_block(const struct block *b,
 
 /* FIXME: Use hash table. */
 static struct block *block_for_tx(const struct chain_topology *topo,
-				  const struct sha256_double *txid,
+				  const struct bitcoin_txid *txid,
 				  const struct bitcoin_tx **tx)
 {
 	struct block *b;
@@ -141,7 +141,7 @@ static struct block *block_for_tx(const struct chain_topology *topo,
 }
 
 size_t get_tx_depth(const struct chain_topology *topo,
-		    const struct sha256_double *txid,
+		    const struct bitcoin_txid *txid,
 		    const struct bitcoin_tx **tx)
 {
 	const struct block *b;
@@ -274,7 +274,7 @@ void broadcast_tx(struct chain_topology *topo,
 	tal_add_destructor2(peer, clear_otx_peer, otx);
 
 	log_add(topo->log, " (tx %s)",
-		type_to_string(ltmp, struct sha256_double, &otx->txid));
+		type_to_string(ltmp, struct bitcoin_txid, &otx->txid));
 
 #if DEVELOPER
 	if (topo->dev_no_broadcast) {
@@ -543,7 +543,7 @@ u32 get_feerate(const struct chain_topology *topo, enum feerate feerate)
 }
 
 struct txlocator *locate_tx(const void *ctx, const struct chain_topology *topo,
-			    const struct sha256_double *txid)
+			    const struct bitcoin_txid *txid)
 {
 	struct block *block = block_for_tx(topo, txid, NULL);
 	if (block == NULL) {
@@ -554,7 +554,7 @@ struct txlocator *locate_tx(const void *ctx, const struct chain_topology *topo,
 	loc->blkheight = block->height;
 	size_t i, n = tal_count(block->txs);
 	for (i = 0; i < n; i++) {
-		struct sha256_double this_txid;
+		struct bitcoin_txid this_txid;
 		bitcoin_txid(block->txs[i], &this_txid);
 		if (structeq(&this_txid, txid)){
 			loc->index = block->txnums[i];

lightningd/chaintopology.h

@@ -2,7 +2,7 @@
 #define LIGHTNING_LIGHTNINGD_CHAINTOPOLOGY_H
 #include "config.h"
 #include <bitcoin/block.h>
-#include <bitcoin/shadouble.h>
+#include <bitcoin/tx.h>
 #include <ccan/list/list.h>
 #include <ccan/short_types/short_types.h>
 #include <ccan/structeq/structeq.h>
@@ -31,7 +31,7 @@ struct outgoing_tx {
 	struct list_node list;
 	struct peer *peer;
 	const char *hextx;
-	struct sha256_double txid;
+	struct bitcoin_txid txid;
 	void (*failed)(struct peer *peer, int exitstatus, const char *err);
 	/* FIXME: Remove this. */
 	struct chain_topology *topo;
@@ -139,7 +139,7 @@ struct txlocator {
 /* This is the number of blocks which would have to be mined to invalidate
  * the tx (optional tx is filled in if return is non-zero). */
 size_t get_tx_depth(const struct chain_topology *topo,
-		    const struct sha256_double *txid,
+		    const struct bitcoin_txid *txid,
 		    const struct bitcoin_tx **tx);
 
 /* Get highest block number. */
@@ -161,7 +161,7 @@ void setup_topology(struct chain_topology *topology,
 		    struct timers *timers,
 		    struct timerel poll_time, u32 first_peer_block);
 
-struct txlocator *locate_tx(const void *ctx, const struct chain_topology *topo, const struct sha256_double *txid);
+struct txlocator *locate_tx(const void *ctx, const struct chain_topology *topo, const struct bitcoin_txid *txid);
 
 void notify_new_block(struct lightningd *ld, unsigned int height);
 void notify_feerate_change(struct lightningd *ld);

lightningd/jsonrpc.c

@@ -359,7 +359,7 @@ void json_add_pubkey(struct json_result *response,
 }
 
 void json_add_txid(struct json_result *result, const char *fieldname,
-		   const struct sha256_double *txid)
+		   const struct bitcoin_txid *txid)
 {
 	char hex[hex_str_size(sizeof(*txid))];
 

lightningd/jsonrpc.h

@@ -5,7 +5,7 @@
 #include <ccan/list/list.h>
 #include <common/json.h>
 
-struct sha256_double;
+struct bitcoin_txid;
 struct wireaddr;
 
 /* Context for a command (from JSON, but might outlive the connection!)
@@ -69,7 +69,7 @@ void json_add_pubkey(struct json_result *response,
 
 /* '"fieldname" : <hexrev>' or "<hexrev>" if fieldname is NULL */
 void json_add_txid(struct json_result *result, const char *fieldname,
-		   const struct sha256_double *txid);
+		   const struct bitcoin_txid *txid);
 
 /* Extract a pubkey from this */
 bool json_tok_pubkey(const char *buffer, const jsmntok_t *tok,

lightningd/peer_control.c

@@ -1108,7 +1108,7 @@ static enum watch_result onchain_tx_watched(struct peer *peer,
 					    void *unused)
 {
 	u8 *msg;
-	struct sha256_double txid;
+	struct bitcoin_txid txid;
 
 	if (depth == 0) {
 		log_unusual(peer->log, "Chain reorganization!");
@@ -1154,7 +1154,7 @@ static enum watch_result onchain_txo_watched(struct peer *peer,
 static void watch_tx_and_outputs(struct peer *peer,
 				 const struct bitcoin_tx *tx)
 {
-	struct sha256_double txid;
+	struct bitcoin_txid txid;
 	struct txwatch *txw;
 
 	bitcoin_txid(tx, &txid);
@@ -1379,7 +1379,7 @@ static enum watch_result funding_spent(struct peer *peer,
 				       void *unused)
 {
 	u8 *msg, *scriptpubkey;
-	struct sha256_double our_last_txid;
+	struct bitcoin_txid our_last_txid;
 	s64 keyindex;
 	struct pubkey ourkey;
 	struct htlc_stub *stubs;
@@ -1495,13 +1495,13 @@ static enum watch_result funding_lockin_cb(struct peer *peer,
 					   unsigned int depth,
 					   void *unused)
 {
-	struct sha256_double txid;
+	struct bitcoin_txid txid;
 	const char *txidstr;
 	struct txlocator *loc;
 	bool peer_ready;
 
 	bitcoin_txid(tx, &txid);
-	txidstr = type_to_string(peer, struct sha256_double, &txid);
+	txidstr = type_to_string(peer, struct bitcoin_txid, &txid);
 	log_debug(peer->log, "Funding tx %s depth %u of %u",
 		  txidstr, depth, peer->minimum_depth);
 	tal_free(txidstr);
@@ -2153,7 +2153,7 @@ static void opening_funder_finished(struct subd *opening, const u8 *resp,
 	u8 *msg;
 	struct channel_info *channel_info;
 	struct utxo *utxos;
-	struct sha256_double funding_txid;
+	struct bitcoin_txid funding_txid;
 	struct pubkey changekey;
 	struct pubkey local_fundingkey;
 	struct crypto_state cs;
@@ -2221,11 +2221,11 @@ static void opening_funder_finished(struct subd *opening, const u8 *resp,
 		log_debug(fc->peer->log, "%zi: %"PRIu64" satoshi (%s) %s\n",
 			  i, fc->utxomap[i]->amount,
 			  fc->utxomap[i]->is_p2sh ? "P2SH" : "SEGWIT",
-			  type_to_string(ltmp, struct sha256_double,
+			  type_to_string(ltmp, struct bitcoin_txid,
 					 &fc->funding_tx->input[i].txid));
 	}
 
-	fc->peer->funding_txid = tal(fc->peer, struct sha256_double);
+	fc->peer->funding_txid = tal(fc->peer, struct bitcoin_txid);
 	bitcoin_txid(fc->funding_tx, fc->peer->funding_txid);
 
 	if (!structeq(fc->peer->funding_txid, &funding_txid)) {
@@ -2292,7 +2292,7 @@ static void opening_fundee_finished(struct subd *opening,
 	/* This is a new channel_info->their_config, set its ID to 0 */
 	peer->channel_info->their_config.id = 0;
 
-	peer->funding_txid = tal(peer, struct sha256_double);
+	peer->funding_txid = tal(peer, struct bitcoin_txid);
 	if (!fromwire_opening_fundee_reply(tmpctx, reply, NULL,
 					   &channel_info->their_config,
 					   remote_commit,
@@ -2334,7 +2334,7 @@ static void opening_fundee_finished(struct subd *opening,
 	}
 
 	log_debug(peer->log, "Watching funding tx %s",
-		     type_to_string(reply, struct sha256_double,
+		     type_to_string(reply, struct bitcoin_txid,
 				    peer->funding_txid));
 	watch_txid(peer, peer->ld->topology, peer, peer->funding_txid,
 		   funding_lockin_cb, NULL);

lightningd/peer_control.h

@@ -69,7 +69,7 @@ struct peer {
 	u64 next_htlc_id;
 
 	/* Funding txid and amounts (once known) */
-	struct sha256_double *funding_txid;
+	struct bitcoin_txid *funding_txid;
 	u16 funding_outnum;
 	u64 funding_satoshi, push_msat;
 	bool remote_funding_locked;

lightningd/test/run-commit_tx.c

@@ -20,26 +20,14 @@ static bool print_superverbose;
 /* Turn this on to brute-force fee values */
 /*#define DEBUG */
 
-static struct sha256 sha256_from_hex(const char *hex)
-{
-	struct sha256 sha256;
-	if (strstarts(hex, "0x"))
-		hex += 2;
-	if (!hex_decode(hex, strlen(hex), &sha256, sizeof(sha256)))
-		abort();
-	return sha256;
-}
-
 /* bitcoind loves its backwards txids! */
-static struct sha256_double txid_from_hex(const char *hex)
+static struct bitcoin_txid txid_from_hex(const char *hex)
 {
-	struct sha256_double sha256;
-	struct sha256 rev = sha256_from_hex(hex);
-	size_t i;
+	struct bitcoin_txid txid;
 
-	for (i = 0; i < sizeof(rev); i++)
-		sha256.sha.u.u8[sizeof(sha256) - 1 - i] = rev.u.u8[i];
-	return sha256;
+	if (!bitcoin_txid_from_hex(hex, strlen(hex), &txid))
+		abort();
+	return txid;
 }
 
 static struct secret secret_from_hex(const char *hex)
@@ -204,7 +192,7 @@ static void report_htlcs(const struct bitcoin_tx *tx,
 {
 	tal_t *tmpctx = tal_tmpctx(NULL);
 	size_t i, n;
-	struct sha256_double txid;
+	struct bitcoin_txid txid;
 	struct bitcoin_tx **htlc_tx;
 	secp256k1_ecdsa_signature *remotehtlcsig;
 	struct keyset keyset;
@@ -439,7 +427,7 @@ static const struct htlc **invert_htlcs(const struct htlc **htlcs)
 int main(void)
 {
 	tal_t *tmpctx = tal_tmpctx(NULL);
-	struct sha256_double funding_txid;
+	struct bitcoin_txid funding_txid;
 	u64 funding_amount_satoshi, dust_limit_satoshi;
 	u32 feerate_per_kw;
 	u16 to_self_delay;

lightningd/watch.c

@@ -65,17 +65,18 @@ static void destroy_txowatch(struct txowatch *w)
 	txowatch_hash_del(&w->topo->txowatches, w);
 }
 
-const struct sha256_double *txwatch_keyof(const struct txwatch *w)
+const struct bitcoin_txid *txwatch_keyof(const struct txwatch *w)
 {
 	return &w->txid;
 }
 
-size_t txid_hash(const struct sha256_double *txid)
+size_t txid_hash(const struct bitcoin_txid *txid)
 {
-	return siphash24(siphash_seed(), txid->sha.u.u8, sizeof(txid->sha.u.u8));
+	return siphash24(siphash_seed(),
+			 txid->shad.sha.u.u8, sizeof(txid->shad.sha.u.u8));
 }
 
-bool txwatch_eq(const struct txwatch *w, const struct sha256_double *txid)
+bool txwatch_eq(const struct txwatch *w, const struct bitcoin_txid *txid)
 {
 	return structeq(&w->txid, txid);
 }
@@ -88,7 +89,7 @@ static void destroy_txwatch(struct txwatch *w)
 struct txwatch *watch_txid_(const tal_t *ctx,
 			    struct chain_topology *topo,
 			    struct peer *peer,
-			    const struct sha256_double *txid,
+			    const struct bitcoin_txid *txid,
 			    enum watch_result (*cb)(struct peer *peer,
 						    const struct bitcoin_tx *,
 						    unsigned int depth,
@@ -112,7 +113,7 @@ struct txwatch *watch_txid_(const tal_t *ctx,
 }
 
 bool watching_txid(const struct chain_topology *topo,
-		   const struct sha256_double *txid)
+		   const struct bitcoin_txid *txid)
 {
 	return txwatch_hash_get(&topo->txwatches, txid) != NULL;
 }
@@ -127,7 +128,7 @@ struct txwatch *watch_tx_(const tal_t *ctx,
 						  void *arg),
 			  void *cb_arg)
 {
-	struct sha256_double txid;
+	struct bitcoin_txid txid;
 
 	bitcoin_txid(tx, &txid);
 	return watch_txid(ctx, topo, peer, &txid, cb, cb_arg);
@@ -136,7 +137,7 @@ struct txwatch *watch_tx_(const tal_t *ctx,
 struct txowatch *watch_txo_(const tal_t *ctx,
 			    struct chain_topology *topo,
 			    struct peer *peer,
-			    const struct sha256_double *txid,
+			    const struct bitcoin_txid *txid,
 			    unsigned int output,
 			    enum watch_result (*cb)(struct peer *peer,
 						    const struct bitcoin_tx *tx,
@@ -173,7 +174,7 @@ static bool txw_fire(struct chain_topology *topo,
 	log_debug(txw->peer->log,
 		  "Got depth change %u->%u for %s",
 		  txw->depth, depth,
-		  type_to_string(ltmp, struct sha256_double, &txw->txid));
+		  type_to_string(ltmp, struct bitcoin_txid, &txw->txid));
 	txw->depth = depth;
 	r = txw->cb(txw->peer, tx, txw->depth, txw->cbdata);
 	switch (r) {
@@ -190,7 +191,7 @@ void txwatch_fire(struct chain_topology *topo,
 		  const struct bitcoin_tx *tx,
 		  unsigned int depth)
 {
-	struct sha256_double txid;
+	struct bitcoin_txid txid;
 	struct txwatch *txw;
 
 	bitcoin_txid(tx, &txid);
@@ -206,15 +207,15 @@ void txowatch_fire(struct chain_topology *topo,
 		   size_t input_num,
 		   const struct block *block)
 {
-	struct sha256_double txid;
+	struct bitcoin_txid txid;
 	enum watch_result r;
 
 	bitcoin_txid(tx, &txid);
 	log_debug(txow->peer->log,
 		  "Got UTXO spend for %s:%u: %s",
-		  type_to_string(ltmp, struct sha256_double, &txow->out.txid),
+		  type_to_string(ltmp, struct bitcoin_txid, &txow->out.txid),
 		  txow->out.index,
-		  type_to_string(ltmp, struct sha256_double, &txid));
+		  type_to_string(ltmp, struct bitcoin_txid, &txid));
 
 	r = txow->cb(txow->peer, tx, input_num, block, txow->cbdata);
 	switch (r) {

lightningd/watch.h

@@ -1,7 +1,7 @@
 #ifndef LIGHTNING_LIGHTNINGD_WATCH_H
 #define LIGHTNING_LIGHTNINGD_WATCH_H
 #include "config.h"
-#include "bitcoin/shadouble.h"
+#include <bitcoin/tx.h>
 #include <ccan/crypto/ripemd160/ripemd160.h>
 #include <ccan/htable/htable_type.h>
 #include <ccan/list/list.h>
@@ -17,7 +17,7 @@ enum watch_result {
 };
 
 struct txwatch_output {
-	struct sha256_double txid;
+	struct bitcoin_txid txid;
 	unsigned int index;
 };
 
@@ -55,7 +55,7 @@ struct txwatch {
 	struct peer *peer;
 
 	/* Transaction to watch. */
-	struct sha256_double txid;
+	struct bitcoin_txid txid;
 	unsigned int depth;
 
 	/* A new depth (0 if kicked out, otherwise 1 = tip, etc.) */
@@ -67,9 +67,9 @@ struct txwatch {
 	void *cbdata;
 };
 
-const struct sha256_double *txwatch_keyof(const struct txwatch *w);
-size_t txid_hash(const struct sha256_double *txid);
-bool txwatch_eq(const struct txwatch *w, const struct sha256_double *txid);
+const struct bitcoin_txid *txwatch_keyof(const struct txwatch *w);
+size_t txid_hash(const struct bitcoin_txid *txid);
+bool txwatch_eq(const struct txwatch *w, const struct bitcoin_txid *txid);
 HTABLE_DEFINE_TYPE(struct txwatch, txwatch_keyof, txid_hash, txwatch_eq,
 		   txwatch_hash);
 
@@ -77,7 +77,7 @@ HTABLE_DEFINE_TYPE(struct txwatch, txwatch_keyof, txid_hash, txwatch_eq,
 struct txwatch *watch_txid_(const tal_t *ctx,
 			    struct chain_topology *topo,
 			    struct peer *peer,
-			    const struct sha256_double *txid,
+			    const struct bitcoin_txid *txid,
 			    enum watch_result (*cb)(struct peer *peer,
 						    const struct bitcoin_tx *,
 						    unsigned int depth,
@@ -115,7 +115,7 @@ struct txwatch *watch_tx_(const tal_t *ctx,
 struct txowatch *watch_txo_(const tal_t *ctx,
 			    struct chain_topology *topo,
 			    struct peer *peer,
-			    const struct sha256_double *txid,
+			    const struct bitcoin_txid *txid,
 			    unsigned int output,
 			    enum watch_result (*cb)(struct peer *peer,
 						    const struct bitcoin_tx *tx,
@@ -144,7 +144,7 @@ void txowatch_fire(struct chain_topology *topo,
 		   const struct block *block);
 
 bool watching_txid(const struct chain_topology *topo,
-		   const struct sha256_double *txid);
+		   const struct bitcoin_txid *txid);
 
 void watch_topology_changed(struct chain_topology *topo);
 #endif /* LIGHTNING_LIGHTNINGD_WATCH_H */

onchaind/onchain.c

@@ -68,14 +68,14 @@ struct proposed_resolution {
 
 /* How it actually got resolved. */
 struct resolution {
-	struct sha256_double txid;
+	struct bitcoin_txid txid;
 	unsigned int depth;
 	enum tx_type tx_type;
 };
 
 struct tracked_output {
 	enum tx_type tx_type;
-	struct sha256_double txid;
+	struct bitcoin_txid txid;
 	u32 tx_blockheight;
 	u32 outnum;
 	u64 satoshi;
@@ -257,7 +257,7 @@ static struct bitcoin_tx *tx_to_us(const tal_t *ctx,
 
 static struct tracked_output *
 	new_tracked_output(struct tracked_output ***outs,
-			   const struct sha256_double *txid,
+			   const struct bitcoin_txid *txid,
 			   u32 tx_blockheight,
 			   enum tx_type tx_type,
 			   u32 outnum,
@@ -272,7 +272,7 @@ static struct tracked_output *
 
 	status_trace("Tracking output %u of %s: %s/%s",
 		     outnum,
-		     type_to_string(trc, struct sha256_double, txid),
+		     type_to_string(trc, struct bitcoin_txid, txid),
 		     tx_type_name(tx_type),
 		     output_type_name(output_type));
 
@@ -298,7 +298,7 @@ static void ignore_output(struct tracked_output *out)
 {
 	status_trace("Ignoring output %u of %s: %s/%s",
 		     out->outnum,
-		     type_to_string(trc, struct sha256_double, &out->txid),
+		     type_to_string(trc, struct bitcoin_txid, &out->txid),
 		     tx_type_name(out->tx_type),
 		     output_type_name(out->output_type));
 
@@ -366,7 +366,7 @@ static void propose_resolution_at_block(struct tracked_output *out,
 
 /* This simple case: true if this was resolved by our proposal. */
 static bool resolved_by_proposal(struct tracked_output *out,
-				 const struct sha256_double *txid)
+				 const struct bitcoin_txid *txid)
 {
 	/* If there's no TX associated, it's not us. */
 	if (!out->proposal->tx)
@@ -394,7 +394,7 @@ static bool resolved_by_proposal(struct tracked_output *out,
 
 /* Otherwise, we figure out what happened and then call this. */
 static void resolved_by_other(struct tracked_output *out,
-			      const struct sha256_double *txid,
+			      const struct bitcoin_txid *txid,
 			      enum tx_type tx_type)
 {
 	out->resolved = tal(out, struct resolution);
@@ -406,7 +406,7 @@ static void resolved_by_other(struct tracked_output *out,
 		     tx_type_name(out->tx_type),
 		     output_type_name(out->output_type),
 		     tx_type_name(tx_type),
-		     type_to_string(trc, struct sha256_double, txid));
+		     type_to_string(trc, struct bitcoin_txid, txid));
 }
 
 static void unknown_spend(struct tracked_output *out,
@@ -479,8 +479,8 @@ static bool is_mutual_close(const struct bitcoin_tx *tx,
 }
 
 /* We only ever send out one, so matching it is easy. */
-static bool is_local_commitment(const struct sha256_double *txid,
-				const struct sha256_double *our_broadcast_txid)
+static bool is_local_commitment(const struct bitcoin_txid *txid,
+				const struct bitcoin_txid *our_broadcast_txid)
 {
 	return structeq(txid, our_broadcast_txid);
 }
@@ -505,7 +505,7 @@ static bool all_irrevocably_resolved(struct tracked_output **outs)
 static void unwatch_tx(const struct bitcoin_tx *tx)
 {
 	u8 *msg;
-	struct sha256_double txid;
+	struct bitcoin_txid txid;
 
 	bitcoin_txid(tx, &txid);
 
@@ -591,7 +591,7 @@ static void handle_htlc_onchain_fulfill(struct tracked_output *out,
 static void resolve_htlc_tx(struct tracked_output ***outs,
 			    size_t out_index,
 			    const struct bitcoin_tx *htlc_tx,
-			    const struct sha256_double *htlc_txid,
+			    const struct bitcoin_txid *htlc_txid,
 			    u32 tx_blockheight)
 {
 	struct tracked_output *out;
@@ -670,7 +670,7 @@ static void output_spent(struct tracked_output ***outs,
 			 u32 input_num,
 			 u32 tx_blockheight)
 {
-	struct sha256_double txid;
+	struct bitcoin_txid txid;
 
 	bitcoin_txid(tx, &txid);
 
@@ -742,7 +742,7 @@ static void output_spent(struct tracked_output ***outs,
 
 	/* Not interesting to us, so unwatch the tx and all its outputs */
 	status_trace("Notified about tx %s output %u spend, but we don't care",
-		     type_to_string(trc, struct sha256_double,
+		     type_to_string(trc, struct bitcoin_txid,
 				    &tx->input[input_num].txid),
 		     tx->input[input_num].index);
 	unwatch_tx(tx);
@@ -783,7 +783,7 @@ static void update_resolution_depth(struct tracked_output *out, u32 depth)
 }
 
 static void tx_new_depth(struct tracked_output **outs,
-			 const struct sha256_double *txid, u32 depth)
+			 const struct bitcoin_txid *txid, u32 depth)
 {
 	size_t i;
 
@@ -932,7 +932,7 @@ static void wait_for_resolved(struct tracked_output **outs)
 {
 	while (!all_irrevocably_resolved(outs)) {
 		u8 *msg = wire_sync_read(outs, REQ_FD);
-		struct sha256_double txid;
+		struct bitcoin_txid txid;
 		struct bitcoin_tx *tx = tal(msg, struct bitcoin_tx);
 		u32 input_num, depth, tx_blockheight;
 		struct preimage preimage;
@@ -962,7 +962,7 @@ static void set_state(enum peer_state state)
 }
 
 static void handle_mutual_close(const struct bitcoin_tx *tx,
-				const struct sha256_double *txid,
+				const struct bitcoin_txid *txid,
 				struct tracked_output **outs)
 {
 	set_state(ONCHAIND_MUTUAL);
@@ -1151,7 +1151,7 @@ static void note_missing_htlcs(u8 **htlc_scripts,
 
 static void handle_our_unilateral(const struct bitcoin_tx *tx,
 				  u32 tx_blockheight,
-				  const struct sha256_double *txid,
+				  const struct bitcoin_txid *txid,
 				  const struct secrets *secrets,
 				  const struct sha256 *shaseed,
 				  const struct pubkey *remote_revocation_basepoint,
@@ -1450,7 +1450,7 @@ static void steal_htlc(struct tracked_output *out)
  * claim all the funds.
  */
 static void handle_their_cheat(const struct bitcoin_tx *tx,
-			       const struct sha256_double *txid,
+			       const struct bitcoin_txid *txid,
 			       u32 tx_blockheight,
 			       const struct sha256 *revocation_preimage,
 			       const struct secrets *secrets,
@@ -1714,7 +1714,7 @@ static void handle_their_cheat(const struct bitcoin_tx *tx,
 
 static void handle_their_unilateral(const struct bitcoin_tx *tx,
 				    u32 tx_blockheight,
-				    const struct sha256_double *txid,
+				    const struct bitcoin_txid *txid,
 				    const struct secrets *secrets,
 				    const struct sha256 *shaseed,
 				    const struct pubkey *remote_per_commitment_point,
@@ -1950,7 +1950,7 @@ int main(int argc, char *argv[])
 	struct secrets secrets;
 	struct sha256 shaseed;
 	struct tracked_output **outs;
-	struct sha256_double our_broadcast_txid, txid;
+	struct bitcoin_txid our_broadcast_txid, txid;
 	secp256k1_ecdsa_signature *remote_htlc_sigs;
 	u64 funding_amount_satoshi, num_htlcs;
 	u8 *scriptpubkey[NUM_SIDES];

onchaind/onchain_wire.csv

@@ -14,7 +14,7 @@ onchain_init,,feerate_per_kw,u32
 onchain_init,,local_dust_limit_satoshi,u64
 onchain_init,,remote_revocation_basepoint,struct pubkey
 # Gives an easy way to tell if it's our unilateral close or theirs...
-onchain_init,,our_broadcast_txid,struct sha256_double
+onchain_init,,our_broadcast_txid,struct bitcoin_txid
 onchain_init,,local_scriptpubkey_len,u16
 onchain_init,,local_scriptpubkey,local_scriptpubkey_len*u8
 onchain_init,,remote_scriptpubkey_len,u16
@@ -56,12 +56,12 @@ onchain_spent,,blockheight,u32
 
 # master->onchaind: We will receive more than one of these, as depth changes.
 onchain_depth,5005
-onchain_depth,,txid,struct sha256_double
+onchain_depth,,txid,struct bitcoin_txid
 onchain_depth,,depth,u32
 
 # onchaind->master: We don't want to watch this tx, or its outputs
 onchain_unwatch_tx,5006
-onchain_unwatch_tx,,txid,struct sha256_double
+onchain_unwatch_tx,,txid,struct bitcoin_txid
 onchain_unwatch_tx,,num_outputs,u32
 
 # master->onchaind: We know HTLC preimage

openingd/opening.c

@@ -47,7 +47,7 @@ struct state {
 	/* Funding and feerate: set by opening peer. */
 	u64 funding_satoshis, push_msat;
 	u32 feerate_per_kw;
-	struct sha256_double funding_txid;
+	struct bitcoin_txid funding_txid;
 	u16 funding_txout;
 
 	/* Secret keys and basepoint secrets. */
@@ -436,7 +436,7 @@ static u8 *funder_channel(struct state *state,
 		     type_to_string(trc, struct pubkey, our_funding_pubkey));
 
 	msg = towire_funding_created(state, &state->channel_id,
-				     &state->funding_txid.sha,
+				     &state->funding_txid,
 				     state->funding_txout,
 				     &sig);
 	if (!sync_crypto_write(&state->cs, PEER_FD, msg))
@@ -643,7 +643,7 @@ static u8 *fundee_channel(struct state *state,
 			      "Reading funding_created: %s", strerror(errno));
 
 	if (!fromwire_funding_created(msg, NULL, &id_in,
-				      &state->funding_txid.sha,
+				      &state->funding_txid,
 				      &state->funding_txout,
 				      &theirsig))
 		peer_failed(PEER_FD, &state->cs, &state->channel_id,

openingd/opening_wire.csv

@@ -43,7 +43,7 @@ opening_funder_reply,,delayed_payment_basepoint,struct pubkey
 opening_funder_reply,,their_per_commit_point,struct pubkey
 opening_funder_reply,,minimum_depth,u32
 opening_funder_reply,,remote_fundingkey,struct pubkey
-opening_funder_reply,,funding_txid,struct sha256_double
+opening_funder_reply,,funding_txid,struct bitcoin_txid
 opening_funder_reply,,feerate_per_kw,u32
 
 # This means they offer the open (contains their offer packet)
@@ -67,7 +67,7 @@ opening_fundee_reply,,htlc_basepoint,struct pubkey
 opening_fundee_reply,,delayed_payment_basepoint,struct pubkey
 opening_fundee_reply,,their_per_commit_point,struct pubkey
 opening_fundee_reply,,remote_fundingkey,struct pubkey
-opening_fundee_reply,,funding_txid,struct sha256_double
+opening_fundee_reply,,funding_txid,struct bitcoin_txid
 opening_fundee_reply,,funding_txout,u16
 opening_fundee_reply,,funding_satoshis,u64
 opening_fundee_reply,,push_msat,u64

tools/generate-wire.py

@@ -19,6 +19,7 @@ type2size = {
     'struct pubkey': 33,
     'struct sha256': 32,
     'struct sha256_double': 32,
+    'struct bitcoin_txid': 32,
     'u64': 8,
     'u32': 4,
     'u16': 2,
@@ -78,6 +79,7 @@ partialtypemap = {
     'features': FieldType('u8'),
     'channel_id': FieldType('struct channel_id'),
     'chain_hash': FieldType('struct sha256_double'),
+    'funding_txid': FieldType('struct bitcoin_txid'),
     'pad': FieldType('pad'),
 }
 

wallet/test/run-wallet.c

@@ -255,7 +255,7 @@ static bool test_channel_crud(const tal_t *ctx)
 	struct wallet_channel c1, *c2 = tal(w, struct wallet_channel);
 	struct peer p;
 	struct channel_info ci;
-	struct sha256_double *hash = tal(w, struct sha256_double);
+	struct bitcoin_txid *hash = tal(w, struct bitcoin_txid);
 	struct pubkey pk;
 	struct changed_htlc last_commit;
 	secp256k1_ecdsa_signature *sig = tal(w, secp256k1_ecdsa_signature);

wallet/wallet.c

@@ -55,7 +55,7 @@ static bool wallet_stmt2output(sqlite3_stmt *stmt, struct utxo *utxo)
 }
 
 bool wallet_update_output_status(struct wallet *w,
-				 const struct sha256_double *txid,
+				 const struct bitcoin_txid *txid,
 				 const u32 outnum, enum output_status oldstatus,
 				 enum output_status newstatus)
 {
@@ -475,7 +475,7 @@ static bool wallet_stmt2channel(struct wallet *w, sqlite3_stmt *stmt,
 
 	if (sqlite3_column_type(stmt, 12) != SQLITE_NULL) {
 		assert(sqlite3_column_bytes(stmt, 12) == 32);
-		chan->peer->funding_txid = tal(chan->peer, struct sha256_double);
+		chan->peer->funding_txid = tal(chan->peer, struct bitcoin_txid);
 		memcpy(chan->peer->funding_txid, sqlite3_column_blob(stmt, 12), 32);
 	} else {
 		chan->peer->funding_txid = NULL;
@@ -829,7 +829,7 @@ int wallet_extract_owned_outputs(struct wallet *w, const struct bitcoin_tx *tx,
 		log_debug(w->log, "Owning output %zu %"PRIu64" (%s) txid %s",
 			  output, tx->output[output].amount,
 			  is_p2sh ? "P2SH" : "SEGWIT",
-			  type_to_string(ltmp, struct sha256_double,
+			  type_to_string(ltmp, struct bitcoin_txid,
 					 &utxo->txid));
 
 		if (!wallet_add_utxo(w, utxo, is_p2sh ? p2sh_wpkh : our_change)) {

wallet/wallet.h

@@ -118,7 +118,7 @@ bool wallet_add_utxo(struct wallet *w, struct utxo *utxo,
  * `output_state_any` as @oldstatus.
  */
 bool wallet_update_output_status(struct wallet *w,
-				 const struct sha256_double *txid,
+				 const struct bitcoin_txid *txid,
 				 const u32 outnum, enum output_status oldstatus,
 				 enum output_status newstatus);
 

wire/fromwire.c

@@ -2,6 +2,7 @@
 #include <bitcoin/preimage.h>
 #include <bitcoin/pubkey.h>
 #include <bitcoin/shadouble.h>
+#include <bitcoin/tx.h>
 #include <ccan/build_assert/build_assert.h>
 #include <ccan/endian/endian.h>
 #include <ccan/mem/mem.h>
@@ -176,6 +177,12 @@ void fromwire_sha256_double(const u8 **cursor, size_t *max,
 	fromwire_sha256(cursor, max, &sha256d->sha);
 }
 
+void fromwire_bitcoin_txid(const u8 **cursor, size_t *max,
+			   struct bitcoin_txid *txid)
+{
+	fromwire_sha256_double(cursor, max, &txid->shad);
+}
+
 void fromwire_preimage(const u8 **cursor, size_t *max, struct preimage *preimage)
 {
 	fromwire(cursor, max, preimage, sizeof(*preimage));
@@ -207,7 +214,7 @@ REGISTER_TYPE_TO_HEXSTR(channel_id);
  * (ie. `funding_output_index` alters the last two bytes).
  */
 void derive_channel_id(struct channel_id *channel_id,
-		       struct sha256_double *txid, u16 txout)
+		       struct bitcoin_txid *txid, u16 txout)
 {
 	BUILD_ASSERT(sizeof(*channel_id) == sizeof(*txid));
 	memcpy(channel_id, txid, sizeof(*channel_id));

wire/test/run-peer-wire.c

@@ -82,7 +82,7 @@ struct msg_closing_signed {
 };
 struct msg_funding_created {
 	struct channel_id temporary_channel_id;
-	struct sha256 txid;
+	struct bitcoin_txid txid;
 	u16 output_index;
 	secp256k1_ecdsa_signature signature;
 };

wire/towire.c

@@ -1,6 +1,7 @@
 #include "wire.h"
 #include <bitcoin/preimage.h>
 #include <bitcoin/shadouble.h>
+#include <bitcoin/tx.h>
 #include <ccan/crypto/ripemd160/ripemd160.h>
 #include <ccan/endian/endian.h>
 #include <ccan/mem/mem.h>
@@ -119,6 +120,11 @@ void towire_sha256_double(u8 **pptr, const struct sha256_double *sha256d)
 	towire_sha256(pptr, &sha256d->sha);
 }
 
+void towire_bitcoin_txid(u8 **pptr, const struct bitcoin_txid *txid)
+{
+	towire_sha256_double(pptr, &txid->shad);
+}
+
 void towire_preimage(u8 **pptr, const struct preimage *preimage)
 {
 	towire(pptr, preimage, sizeof(*preimage));

wire/wire.h

@@ -15,11 +15,12 @@ struct channel_id {
 	u8 id[32];
 };
 
+struct bitcoin_txid;
 struct preimage;
 struct ripemd160;
 
 void derive_channel_id(struct channel_id *channel_id,
-		       struct sha256_double *txid, u16 txout);
+		       struct bitcoin_txid *txid, u16 txout);
 
 /* Read the type; returns -1 if not long enough.  cursor is a tal ptr. */
 int fromwire_peektype(const u8 *cursor);
@@ -38,6 +39,7 @@ void towire_short_channel_id(u8 **pptr,
 			     const struct short_channel_id *short_channel_id);
 void towire_sha256(u8 **pptr, const struct sha256 *sha256);
 void towire_sha256_double(u8 **pptr, const struct sha256_double *sha256d);
+void towire_bitcoin_txid(u8 **pptr, const struct bitcoin_txid *txid);
 void towire_preimage(u8 **pptr, const struct preimage *preimage);
 void towire_ripemd160(u8 **pptr, const struct ripemd160 *ripemd);
 void towire_u8(u8 **pptr, u8 v);
@@ -70,6 +72,8 @@ void fromwire_short_channel_id(const u8 **cursor, size_t *max,
 void fromwire_sha256(const u8 **cursor, size_t *max, struct sha256 *sha256);
 void fromwire_sha256_double(const u8 **cursor, size_t *max,
 			    struct sha256_double *sha256d);
+void fromwire_bitcoin_txid(const u8 **cursor, size_t *max,
+			   struct bitcoin_txid *txid);
 void fromwire_preimage(const u8 **cursor, size_t *max, struct preimage *preimage);
 void fromwire_ripemd160(const u8 **cursor, size_t *max, struct ripemd160 *ripemd);
 void fromwire_pad(const u8 **cursor, size_t *max, size_t num);