bitcoin/feerate: new exposure for feerate parsing outside lightningd.

This exposes the numeric part of param_feerate() as param_feerate_val().

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

bitcoin/feerate.c

@@ -0,0 +1,40 @@
+#include <bitcoin/feerate.h>
+#include <limits.h>
+#include <stdlib.h>
+
+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();
+}
+
+const char *feerate_style_name(enum feerate_style style)
+{
+	switch (style) {
+	case FEERATE_PER_KBYTE:
+		return "perkb";
+	case FEERATE_PER_KSIPA:
+		return "perkw";
+	}
+	abort();
+}