Added static assert of std::string::value_type size

* CodepointIterator only supports UTF-8 encoded single-byte input strings
** this should prevent CodepointIterator from compiling on systems with larger char sizes while providing a helpful error message
* improved const-correctness by marking currByte (iterator dereferencing cache) and helper method arguments as const

1 files changed, 5 insertions, 0 deletions

diff --git a/src/codepoint_iterator.h b/src/codepoint_iterator.h
index d1806e5..77600b7 100644
--- a/src/codepoint_iterator.h
+++ b/src/codepoint_iterator.h
@@ -10,6 +10,11 @@ namespace UTF8 {
 class CodepointIterator : public std::iterator<std::bidirectional_iterator_tag,
                                                char32_t,
                                                std::string::difference_type> {
+	static_assert(
+		sizeof(std::string::value_type) == 1,
+		"CodepointIterator only supports single-byte UTF-8 encoded input"
+	);
+
 	public:
 		CodepointIterator(std::string::const_iterator);
 		CodepointIterator(const CodepointIterator&);