utf8truncate: max size was specified to be bytes but used as character count

src/utils/utf8iter.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2017-2019 J.F.Dockes
+/* Copyright (C) 2017-2020 J.F.Dockes
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU Lesser General Public License as published by
  *   the Free Software Foundation; either version 2.1 of the License, or
@@ -17,12 +17,13 @@
 
 #include "utf8iter.h"
 
+#include <algorithm>
 #include <unordered_set>
 #include <iostream>
 
 using namespace std;
 
-void utf8truncate(std::string& s, int maxlen, int flags, const string& ellipsis,
+void utf8truncate(string& s, int maxlen, int flags, const string& ellipsis,
                   const string& ws)
 {
     if (s.size() <= string::size_type(maxlen)) {
@@ -39,11 +40,7 @@ void utf8truncate(std::string& s, int maxlen, int flags, const string& ellipsis,
 
     if (flags & UTF8T_ELLIPSIS) {
         size_t ellen = utf8len(ellipsis);
-        if (maxlen > int(ellen)) {
-            maxlen -= ellen;
-        } else {
-            maxlen = 0;
-        }
+        maxlen = std::max(0, maxlen - int(ellen));
     }
 
     Utf8Iter iter(s);
@@ -51,7 +48,7 @@ void utf8truncate(std::string& s, int maxlen, int flags, const string& ellipsis,
     string::size_type lastwspos = 0;
     for (; !iter.eof(); iter++) {
         unsigned int c = *iter;
-        if (iter.getCpos() < string::size_type(maxlen)) {
+        if (iter.getBpos() < string::size_type(maxlen)) {
             pos = iter.getBpos() + iter.getBlen();
             if ((flags & UTF8T_ATWORD) && wss.find(c) != wss.end()) {
                 lastwspos = pos;

src/utils/utf8iter.h

@@ -281,11 +281,18 @@ private:
 
 
 enum Utf8TruncateFlag {UTF8T_NONE, UTF8T_ATWORD, UTF8T_ELLIPSIS};
-// maxlen is in utf-8 chars.
-extern void utf8truncate(std::string& s, int maxlen, int flags = 0,
-                         const std::string& ellipsis = "...",
-                         const std::string& ws = " \t\n\r");
-extern size_t utf8len(const std::string& s);
+
+/** Truncate utf8 string, maintaining encoding integrity
+ * @param s input string to be modified in place
+ * @param maxlen maximum size after truncation in bytes
+ * @param flags Specify cutting at word position, adding an ellipsis
+ */
+void utf8truncate(std::string& s, int maxlen, int flags = 0,
+                  const std::string& ellipsis = "...",
+                  const std::string& ws = " \t\n\r");
+
+/** Compute length in characters of utf-8 string */
+size_t utf8len(const std::string& s);
 
 /** @brief Check and possibly fix string by replacing badly encoded
  * characters with the standard question mark replacement character.
@@ -297,7 +304,7 @@ extern size_t utf8len(const std::string& s);
  * @return -1 for failure (fixit false or maxrepl reached). 
  *   0 or positive: replacement count.
  */
-extern int utf8check(
+int utf8check(
     const std::string& in, std::string& out, bool fixit=false, int maxrepl=100);
 
 #endif /* _UTF8ITER_H_INCLUDED_ */