short_channel_id: don't use bitfields.

I leave all the now-unnecessary accessors in place to avoid churn, but
the use of bitfields has been more pain than help.

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

bitcoin/short_channel_id.c

@@ -3,6 +3,14 @@
 #include <stdio.h>
 #include <string.h>
 
+void mk_short_channel_id(struct short_channel_id *scid,
+			 u32 blocknum, u32 txnum, u16 outnum)
+{
+	scid->u64 = (((u64)blocknum & 0xFFFFFF) << 40 |
+		     ((u64)txnum & 0xFFFFFF) << 16 |
+		     (outnum & 0xFFFF));
+}
+
 bool short_channel_id_from_str(const char *str, size_t strlen,
 			       struct short_channel_id *dst)
 {
@@ -15,26 +23,14 @@ bool short_channel_id_from_str(const char *str, size_t strlen,
 	buf[strlen] = 0;
 
 	matches = sscanf(buf, "%u:%u:%hu", &blocknum, &txnum, &outnum);
-	dst->blocknum = blocknum;
-	dst->txnum = txnum;
-	dst->outnum = outnum;
+	mk_short_channel_id(dst, blocknum, txnum, outnum);
 	return matches == 3;
 }
 
 char *short_channel_id_to_str(const tal_t *ctx, const struct short_channel_id *scid)
 {
-	return tal_fmt(ctx, "%d:%d:%d", scid->blocknum, scid->txnum, scid->outnum);
-}
-
-bool short_channel_id_eq(const struct short_channel_id *a,
-			 const struct short_channel_id *b)
-{
-	return a->blocknum == b->blocknum && a->txnum == b->txnum &&
-	       a->outnum == b->outnum;
-}
-
-u64 short_channel_id_to_uint(const struct short_channel_id *scid)
-{
-	return ((u64)scid->blocknum & 0xFFFFFF) << 40 |
-	       ((u64)scid->txnum & 0xFFFFFF) << 16 | (scid->outnum & 0xFFFF);
+	return tal_fmt(ctx, "%d:%d:%d",
+		       short_channel_id_blocknum(scid),
+		       short_channel_id_txnum(scid),
+		       short_channel_id_outnum(scid));
 }

bitcoin/short_channel_id.h

@@ -12,20 +12,42 @@
  * just memset them and not have to take care about the extra byte for
  * u32 */
 struct short_channel_id {
-	u32 blocknum : 24;
-	u32 txnum : 24;
-	u16 outnum;
+	u64 u64;
 };
 
+static inline u32 short_channel_id_blocknum(const struct short_channel_id *scid)
+{
+	return scid->u64 >> 40;
+}
+
+static inline u32 short_channel_id_txnum(const struct short_channel_id *scid)
+{
+	return (scid->u64 >> 16) & 0x00FFFFFF;
+}
+
+static inline u16 short_channel_id_outnum(const struct short_channel_id *scid)
+{
+	return scid->u64 & 0xFFFF;
+}
+
+void mk_short_channel_id(struct short_channel_id *scid,
+			 u32 blocknum, u32 txnum, u16 outnum);
+
 bool short_channel_id_from_str(const char *str, size_t strlen,
 			       struct short_channel_id *dst);
 
-bool short_channel_id_eq(const struct short_channel_id *a,
-			 const struct short_channel_id *b);
-
-char *short_channel_id_to_str(const tal_t *ctx, const struct short_channel_id *scid);
+static inline bool short_channel_id_eq(const struct short_channel_id *a,
+				       const struct short_channel_id *b)
+{
+	return a->u64 == b->u64;
+}
 
 /* Fast, platform dependent, way to convert from a short_channel_id to u64 */
-u64 short_channel_id_to_uint(const struct short_channel_id *scid);
+static inline u64 short_channel_id_to_uint(const struct short_channel_id *scid)
+{
+	return scid->u64;
+}
+
+char *short_channel_id_to_str(const tal_t *ctx, const struct short_channel_id *scid);
 
 #endif /* LIGHTNING_BITCOIN_SHORT_CHANNEL_ID_H */

lightningd/gossip_control.c

@@ -89,7 +89,9 @@ static void get_txout(struct subd *gossip, const u8 *msg)
 	/* FIXME: Block less than 6 deep? */
 
 	bitcoind_getoutput(gossip->ld->topology->bitcoind,
-			   scid->blocknum, scid->txnum, scid->outnum,
+			   short_channel_id_blocknum(scid),
+			   short_channel_id_txnum(scid),
+			   short_channel_id_outnum(scid),
 			   got_txout, scid);
 }
 

lightningd/pay.c

@@ -256,7 +256,7 @@ remote_routing_failure(const tal_t *ctx,
 	const struct pubkey *erring_node;
 	const struct short_channel_id *route_channels;
 	const struct short_channel_id *erring_channel;
-	static const struct short_channel_id dummy_channel = { 0, 0, 0 };
+	static const struct short_channel_id dummy_channel = { 0 };
 	int origin_index;
 	bool retry_plausible;
 	bool report_to_gossipd;

lightningd/peer_control.c

@@ -521,9 +521,9 @@ static enum watch_result funding_lockin_cb(struct channel *channel,
 	/* If we restart, we could already have peer->scid from database */
 	if (!channel->scid) {
 		channel->scid = tal(channel, struct short_channel_id);
-		channel->scid->blocknum = loc->blkheight;
-		channel->scid->txnum = loc->index;
-		channel->scid->outnum = channel->funding_outnum;
+		mk_short_channel_id(channel->scid,
+				    loc->blkheight, loc->index,
+				    channel->funding_outnum);
 	}
 	tal_free(loc);
 

wire/fromwire.c

@@ -158,15 +158,7 @@ void fromwire_channel_id(const u8 **cursor, size_t *max,
 void fromwire_short_channel_id(const u8 **cursor, size_t *max,
 			       struct short_channel_id *short_channel_id)
 {
-	be32 txnum = 0, blocknum = 0;
-
-	/* Pulling 3 bytes off wire is tricky; they're big-endian. */
-	fromwire(cursor, max, (char *)&blocknum + 1, 3);
-	short_channel_id->blocknum = be32_to_cpu(blocknum);
-	fromwire(cursor, max, (char *)&txnum + 1, 3);
-	short_channel_id->txnum = be32_to_cpu(txnum);
-
-	short_channel_id->outnum = fromwire_u16 (cursor, max);
+	short_channel_id->u64 = fromwire_u64(cursor, max);
 }
 
 void fromwire_sha256(const u8 **cursor, size_t *max, struct sha256 *sha256)

wire/towire.c

@@ -105,12 +105,7 @@ void towire_channel_id(u8 **pptr, const struct channel_id *channel_id)
 void towire_short_channel_id(u8 **pptr,
 			     const struct short_channel_id *short_channel_id)
 {
-	be32 txnum = cpu_to_be32(short_channel_id->txnum);
-	be32 blocknum = cpu_to_be32(short_channel_id->blocknum);
-
-	towire(pptr, (char *)&blocknum + 1, 3);
-	towire(pptr, (char *)&txnum + 1, 3);
-	towire_u16(pptr, short_channel_id->outnum);
+	towire_u64(pptr, short_channel_id->u64);
 }
 
 void towire_sha256(u8 **pptr, const struct sha256 *sha256)