From ab87e56bec6a8727a1bbfae7858fb5b0122539a7 Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty@rustcorp.com.au>
Date: Thu, 18 Aug 2022 13:02:16 +0930
Subject: [PATCH] rune: add helpers for users doing DIY parsing.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 ccan/rune/coding.c | 34 +++++++++++++++++++---------------
 ccan/rune/rune.h   | 21 +++++++++++++++++++++
 2 files changed, 40 insertions(+), 15 deletions(-)

diff --git a/ccan/rune/coding.c b/ccan/rune/coding.c
index 380a225c..f4d11028 100644
--- a/ccan/rune/coding.c
+++ b/ccan/rune/coding.c
@@ -184,7 +184,7 @@ static bool pull_char(const char **data, size_t *len, char *c)
 	return true;
 }
 
-static bool is_valid_cond(enum rune_condition cond)
+bool rune_condition_is_valid(enum rune_condition cond)
 {
 	switch (cond) {
 	case RUNE_COND_IF_MISSING:
@@ -203,31 +203,35 @@ static bool is_valid_cond(enum rune_condition cond)
 	return false;
 }
 
+size_t rune_altern_fieldname_len(const char *alternstr, size_t alternstrlen)
+{
+	for (size_t i = 0; i < alternstrlen; i++) {
+		if (cispunct(alternstr[i]))
+			return i;
+	}
+	return alternstrlen;
+}
+
 /* Sets *more on success: true if another altern follows */
 static struct rune_altern *rune_altern_decode(const tal_t *ctx,
 					      const char **data, size_t *len,
 					      bool *more)
 {
 	struct rune_altern *alt = tal(ctx, struct rune_altern);
-	const char *strstart = *data;
 	char *value;
-	size_t strlen = 0;
+	size_t strlen;
 	char c;
 
-        /* Swallow field up to conditional */
-	for (;;) {
-		if (!pull_char(data, len, &c))
-			return tal_free(alt);
-		if (cispunct(c))
-			break;
-		strlen++;
-	}
+        /* Swallow field up to possible conditional */
+	strlen = rune_altern_fieldname_len(*data, *len);
+	alt->fieldname = tal_strndup(alt, *data, strlen);
+	*data += strlen;
+	*len -= strlen;
 
-	alt->fieldname = tal_strndup(alt, strstart, strlen);
-	if (!is_valid_cond(c)) {
-		pull_invalid(data, len);
+	/* Grab conditional */
+	if (!pull_char(data, len, &c) || !rune_condition_is_valid(c))
 		return tal_free(alt);
-	}
+
 	alt->condition = c;
 
 	/* Assign worst case. */
diff --git a/ccan/rune/rune.h b/ccan/rune/rune.h
index b67b7828..c373269a 100644
--- a/ccan/rune/rune.h
+++ b/ccan/rune/rune.h
@@ -376,4 +376,25 @@ char *rune_to_string(const tal_t *ctx, const struct rune *rune);
 struct rune_restr *rune_restr_from_string(const tal_t *ctx,
 					  const char *str,
 					  size_t len);
+
+/**
+ * rune_condition_is_valid: is this a valid condition?
+ * @cond: potential condition character.
+ *
+ * Returns true if it's one of enum rune_condition.
+ */
+bool rune_condition_is_valid(enum rune_condition cond);
+
+/**
+ * rune_altern_fieldname_len: how much of this string is condition?
+ * @alternstr: potential alternative string
+ * @alternstrlen: length
+ *
+ * This helps parsing your own runes.
+ *
+ * Returns the first possible condition (check with rune_condition_is_valid)
+ * or alternstrlen if none found.
+ */
+size_t rune_altern_fieldname_len(const char *alternstr, size_t alternstrlen);
+
 #endif /* CCAN_RUNE_RUNE_H */
-- 
2.39.2