Add string_truncate utility function

common/common.cpp

@@ -1,3 +1,5 @@
+##testing if devin picks up changes
+
 #if defined(_MSC_VER)
 #define _SILENCE_CXX17_CODECVT_HEADER_DEPRECATION_WARNING
 #endif
@@ -527,6 +529,37 @@ std::string string_repeat(const std::string & str, size_t n) {
     return result;
 }
 
+/**
+ * @brief Truncates a string to a maximum length, appending ellipsis if truncated.
+ *
+ * This function shortens a string to fit within a specified maximum length.
+ * If truncation occurs, "..." is appended to indicate the string was shortened.
+ *
+ * @param str The input string to truncate.
+ * @param max_len The maximum allowed length of the output string (including ellipsis).
+ *
+ * @return The original string if its length is <= max_len.
+ *         If max_len < 3, returns the first max_len characters without ellipsis.
+ *         Otherwise, returns the first (max_len - 3) characters followed by "...".
+ *
+ * @note This function operates on bytes, not Unicode code points. Truncating
+ *       UTF-8 strings may result in invalid sequences if cut mid-character.
+ *
+ * @example
+ *   string_truncate("Hello World", 8)  -> "Hello..."
+ *   string_truncate("Hi", 10)          -> "Hi"
+ *   string_truncate("Hello", 2)        -> "He"
+ */
+std::string string_truncate(const std::string & str, size_t max_len) {
+    if (str.length() <= max_len) {
+        return str;
+    }
+    if (max_len < 3) {
+        return str.substr(0, max_len);
+    }
+    return str.substr(0, max_len - 3) + "...";
+}
+
 std::string string_from(bool value) {
     return value ? "true" : "false";
 }

common/common.h

@@ -587,6 +587,9 @@ bool string_ends_with(const std::string_view & str, const std::string_view & suf
 bool string_remove_suffix(std::string & str, const std::string_view & suffix);
 size_t string_find_partial_stop(const std::string_view & str, const std::string_view & stop);
 
+// Truncate a string to a maximum length, adding ellipsis if truncated
+std::string string_truncate(const std::string & str, size_t max_len);
+
 bool string_parse_kv_override(const char * data, std::vector<llama_model_kv_override> & overrides);
 void string_process_escapes(std::string & input);