cleanup: extract and formalize feerate conversion.

I didn't want to create a new file for this now, as that would totally
break #1880.

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

lightningd/bitcoind.c

@@ -332,7 +332,8 @@ static bool process_estimatefee(struct bitcoin_cli *bcli)
 		efee->satoshi_per_kw[efee->i] = 0;
 	} else
 		/* Rate in satoshi per kw. */
-		efee->satoshi_per_kw[efee->i] = feerate / 4;
+		efee->satoshi_per_kw[efee->i]
+			= feerate_from_style(feerate, FEERATE_PER_KBYTE);
 
 	efee->i++;
 	if (efee->i == tal_count(efee->satoshi_per_kw)) {

lightningd/chaintopology.c

@@ -19,7 +19,6 @@
 #include <inttypes.h>
 #include <lightningd/channel_control.h>
 #include <lightningd/gossip_control.h>
-#include <lightningd/json.h>
 #include <lightningd/jsonrpc_errors.h>
 #include <lightningd/param.h>
 
@@ -422,6 +421,32 @@ u32 unilateral_feerate(struct chain_topology *topo)
 	return try_get_feerate(topo, FEERATE_URGENT);
 }
 
+u32 feerate_from_style(u32 feerate, enum feerate_style style)
+{
+	switch (style) {
+	case FEERATE_PER_KSIPA:
+		return feerate;
+	case FEERATE_PER_KBYTE:
+		/* Everyone uses satoshi per kbyte, but we use satoshi per ksipa
+		 * (don't round down to zero though)! */
+		return (feerate + 3) / 4;
+	}
+	abort();
+}
+
+u32 feerate_to_style(u32 feerate_perkw, enum feerate_style style)
+{
+	switch (style) {
+	case FEERATE_PER_KSIPA:
+		return feerate_perkw;
+	case FEERATE_PER_KBYTE:
+		if ((u64)feerate_perkw * 4 > UINT_MAX)
+			return UINT_MAX;
+		return feerate_perkw * 4;
+	}
+	abort();
+}
+
 static void json_feerates(struct command *cmd,
 			    const char *buffer, const jsmntok_t *params)
 {
@@ -429,12 +454,10 @@ static void json_feerates(struct command *cmd,
 	struct json_result *response;
 	u32 *urgent, *normal, *slow, feerates[NUM_FEERATES];
 	bool missing;
-	const jsmntok_t *style;
+	enum feerate_style *style;
-	bool bitcoind_style;
-	u64 mulfactor;
 
 	if (!param(cmd, buffer, params,
-		   p_req("style", json_tok_tok, &style),
+		   p_req("style", json_tok_feerate_style, &style),
 		   p_opt("urgent", json_tok_number, &urgent),
 		   p_opt("normal", json_tok_number, &normal),
 		   p_opt("slow", json_tok_number, &slow),
@@ -446,20 +469,8 @@ static void json_feerates(struct command *cmd,
 	feerates[FEERATE_NORMAL] = normal ? *normal : 0;
 	feerates[FEERATE_SLOW] = slow ? *slow : 0;
 
-	if (json_tok_streq(buffer, style, "perkw")) {
+	for (size_t i = 0; i < ARRAY_SIZE(feerates); i++)
-		bitcoind_style = false;
+		feerates[i] = feerate_from_style(feerates[i], *style);
-		mulfactor = 1;
-	} else if (json_tok_streq(buffer, style, "perkb")) {
-		/* Everyone uses satoshi per kbyte, but we use satoshi per ksipa
-		 * (don't round down to zero though)! */
-		for (size_t i = 0; i < ARRAY_SIZE(feerates); i++)
-			feerates[i] = (feerates[i] + 3) / 4;
-		bitcoind_style = true;
-		mulfactor = 4;
-	} else {
-		command_fail(cmd, JSONRPC2_INVALID_PARAMS, "invalid style");
-		return;
-	}
 
 	log_info(topo->log,
 		 "feerates: inserting feerates in sipa/kb %u/%u/%u",
@@ -478,16 +489,17 @@ static void json_feerates(struct command *cmd,
 
 	response = new_json_result(cmd);
 	json_object_start(response, NULL);
-	json_object_start(response, bitcoind_style ? "perkb" : "perkw");
+	json_object_start(response, json_feerate_style_name(*style));
 	for (size_t i = 0; i < ARRAY_SIZE(feerates); i++) {
 		if (!feerates[i])
 			continue;
-		json_add_num(response, feerate_name(i), feerates[i] * mulfactor);
+		json_add_num(response, feerate_name(i),
+			     feerate_to_style(feerates[i], *style));
 	}
 	json_add_u64(response, "min_acceptable",
-		     feerate_min(cmd->ld, NULL) * mulfactor);
+		     feerate_to_style(feerate_min(cmd->ld, NULL), *style));
 	json_add_u64(response, "max_acceptable",
-		     feerate_max(cmd->ld, NULL) * mulfactor);
+		     feerate_to_style(feerate_max(cmd->ld, NULL), *style));
 	json_object_end(response);
 
 	if (missing)

lightningd/chaintopology.h

@@ -8,6 +8,7 @@
 #include <ccan/structeq/structeq.h>
 #include <ccan/time/time.h>
 #include <jsmn.h>
+#include <lightningd/json.h>
 #include <lightningd/watch.h>
 #include <math.h>
 #include <stddef.h>
@@ -19,6 +20,7 @@ struct lightningd;
 struct peer;
 struct txwatch;
 
+/* FIXME: move all feerate stuff out to new lightningd/feerate.[ch] files */
 enum feerate {
 	FEERATE_URGENT, /* Aka: aim for next block. */
 	FEERATE_NORMAL, /* Aka: next 4 blocks or so. */
@@ -144,6 +146,10 @@ u32 mutual_close_feerate(struct chain_topology *topo);
 u32 opening_feerate(struct chain_topology *topo);
 u32 unilateral_feerate(struct chain_topology *topo);
 
+/* We always use feerate-per-ksipa, ie. perkw */
+u32 feerate_from_style(u32 feerate, enum feerate_style style);
+u32 feerate_to_style(u32 feerate_perkw, enum feerate_style style);
+
 /* Broadcast a single tx, and rebroadcast as reqd (copies tx).
  * If failed is non-NULL, call that and don't rebroadcast. */
 void broadcast_tx(struct chain_topology *topo,

lightningd/json.c

@@ -223,6 +223,41 @@ bool json_tok_short_channel_id(struct command *cmd, const char *name,
 	return false;
 }
 
+const char *json_feerate_style_name(enum feerate_style style)
+{
+	switch (style) {
+	case FEERATE_PER_KBYTE:
+		return "perkb";
+	case FEERATE_PER_KSIPA:
+		return "perkw";
+	}
+	abort();
+}
+
+bool json_tok_feerate_style(struct command *cmd, const char *name,
+			    const char *buffer, const jsmntok_t *tok,
+			    enum feerate_style **style)
+{
+	*style = tal(cmd, enum feerate_style);
+	if (json_tok_streq(buffer, tok,
+			   json_feerate_style_name(FEERATE_PER_KSIPA))) {
+		**style = FEERATE_PER_KSIPA;
+		return true;
+	} else if (json_tok_streq(buffer, tok,
+				  json_feerate_style_name(FEERATE_PER_KBYTE))) {
+		**style = FEERATE_PER_KBYTE;
+		return true;
+	}
+
+	command_fail(cmd, JSONRPC2_INVALID_PARAMS,
+		     "'%s' should be '%s' or '%s', not '%.*s'",
+		     name,
+		     json_feerate_style_name(FEERATE_PER_KSIPA),
+		     json_feerate_style_name(FEERATE_PER_KBYTE),
+		     tok->end - tok->start, buffer + tok->start);
+	return false;
+}
+
 bool
 json_tok_channel_id(const char *buffer, const jsmntok_t *tok,
 		    struct channel_id *cid)

lightningd/json.h

@@ -83,6 +83,18 @@ bool json_tok_u64(struct command *cmd, const char *name,
 		  const char *buffer, const jsmntok_t *tok,
 		  uint64_t **num);
 
+enum feerate_style {
+	FEERATE_PER_KSIPA,
+	FEERATE_PER_KBYTE
+};
+
+/* Extract a feerate style. */
+bool json_tok_feerate_style(struct command *cmd, const char *name,
+			    const char *buffer, const jsmntok_t *tok,
+			    enum feerate_style **style);
+
+const char *json_feerate_style_name(enum feerate_style style);
+
 /* '"fieldname" : "1234:5:6"' */
 void json_add_short_channel_id(struct json_result *response,
 			       const char *fieldname,

tests/test_misc.py

@@ -876,7 +876,7 @@ def test_feerates(node_factory):
     assert len(feerates['perkb']) == 2
     assert feerates['warning'] == 'Some fee estimates unavailable: bitcoind startup?'
     assert 'perkw' not in feerates
-    assert feerates['perkb']['max_acceptable'] == (2**32 - 1) * 4
+    assert feerates['perkb']['max_acceptable'] == (2**32 - 1)
     assert feerates['perkb']['min_acceptable'] == 253 * 4
 
     # Now try setting them, one at a time.