util/StringVerify: new library

src/util/StringVerify.hxx

@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright CM4all GmbH
+// author: Max Kellermann <mk@cm4all.com>
+
+#pragma once
+
+#include <algorithm>
+#include <concepts>
+#include <string_view>
+
+/**
+ * Does the given string consist only of characters allowed by the
+ * given function?
+ */
+constexpr bool
+CheckChars(std::string_view s, std::predicate<char> auto f) noexcept
+{
+	return std::all_of(s.begin(), s.end(), f);
+}
+
+/**
+ * Is the given string non-empty and consists only of characters
+ * allowed by the given function?
+ */
+constexpr bool
+CheckCharsNonEmpty(std::string_view s, std::predicate<char> auto f) noexcept
+{
+	return !s.empty() && CheckChars(s, f);
+}
+
+constexpr bool
+CheckCharsNonEmpty(const char *s, std::predicate<char> auto f) noexcept
+{
+	do {
+		if (!f(*s))
+			return false;
+	} while (*++s);
+	return true;
+}