[test] move string helper functions into test library

1 files changed, 33 insertions, 0 deletions

diff --git a/src/test/util/str.h b/src/test/util/str.h
index 63629501e8..ef94692df0 100644
--- a/src/test/util/str.h
+++ b/src/test/util/str.h
@@ -9,4 +9,37 @@
 
 bool CaseInsensitiveEqual(const std::string& s1, const std::string& s2);
 
+/**
+ * Increment a string. Useful to enumerate all fixed length strings with
+ * characters in [min_char, max_char].
+ */
+template <typename CharType, size_t StringLength>
+bool NextString(CharType (&string)[StringLength], CharType min_char, CharType max_char)
+{
+    for (CharType& elem : string) {
+        bool has_next = elem != max_char;
+        elem = elem < min_char || elem >= max_char ? min_char : CharType(elem + 1);
+        if (has_next) return true;
+    }
+    return false;
+}
+
+/**
+ * Iterate over string values and call function for each string without
+ * successive duplicate characters.
+ */
+template <typename CharType, size_t StringLength, typename Fn>
+void ForEachNoDup(CharType (&string)[StringLength], CharType min_char, CharType max_char, Fn&& fn) {
+    for (bool has_next = true; has_next; has_next = NextString(string, min_char, max_char)) {
+        int prev = -1;
+        bool skip_string = false;
+        for (CharType c : string) {
+            if (c == prev) skip_string = true;
+            if (skip_string || c < min_char || c > max_char) break;
+            prev = c;
+        }
+        if (!skip_string) fn();
+    }
+}
+
 #endif // BITCOIN_TEST_UTIL_STR_H