common: infrastructure to construct warning messages.

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

common/wire_error.c

@@ -42,6 +42,43 @@ u8 *towire_errorfmt(const tal_t *ctx,
 	return msg;
 }
 
+u8 *towire_warningfmtv(const tal_t *ctx,
+		       const struct channel_id *channel,
+		       const char *fmt,
+		       va_list ap)
+{
+	/* BOLT #1:
+	 *
+	 * The channel is referred to by `channel_id`, unless `channel_id` is
+	 * 0 (i.e. all bytes are 0), in which case it refers to all
+	 * channels. */
+	static const struct channel_id all_channels;
+	char *estr;
+	u8 *msg;
+
+	estr = tal_vfmt(ctx, fmt, ap);
+	/* We need tal_len to work, so we use copy. */
+	msg = towire_warning(ctx, channel ? channel : &all_channels,
+			     (u8 *)tal_dup_arr(estr, char, estr, strlen(estr), 0));
+	tal_free(estr);
+
+	return msg;
+}
+
+u8 *towire_warningfmt(const tal_t *ctx,
+		      const struct channel_id *channel,
+		      const char *fmt, ...)
+{
+	va_list ap;
+	u8 *msg;
+
+	va_start(ap, fmt);
+	msg = towire_warningfmtv(ctx, channel, fmt, ap);
+	va_end(ap);
+
+	return msg;
+}
+
 bool channel_id_is_all(const struct channel_id *channel_id)
 {
 	return memeqzero(channel_id, sizeof(*channel_id));

common/wire_error.h

@@ -32,6 +32,30 @@ u8 *towire_errorfmtv(const tal_t *ctx,
 		     const char *fmt,
 		     va_list ap);
 
+/**
+ * towire_warningfmt - helper to turn string into WIRE_WARNING.
+ *
+ * @ctx: context to allocate from
+ * @channel: specific channel to complain about, or NULL for all.
+ * @fmt: format for warning.
+ */
+u8 *towire_warningfmt(const tal_t *ctx,
+		      const struct channel_id *channel,
+		      const char *fmt, ...) PRINTF_FMT(3,4);
+
+/**
+ * towire_warningfmtv - helper to turn string into WIRE_WARNING.
+ *
+ * @ctx: context to allocate from
+ * @channel: specific channel to complain about, or NULL for all.
+ * @fmt: format for warning.
+ * @ap: accumulated varargs.
+ */
+u8 *towire_warningfmtv(const tal_t *ctx,
+		       const struct channel_id *channel,
+		       const char *fmt,
+		       va_list ap);
+
 /* BOLT #1:
  *
  * The channel is referred to by `channel_id`, unless `channel_id` is 0