add find_char_boundary, get_term_width_message

Cargo.toml

@@ -6,3 +6,4 @@ edition = "2018"
 
 [dependencies]
 term = "0.5.2"
+term_size = "0.3.1"

src/lib.rs

@@ -178,6 +178,35 @@ pub fn print_lastline(line: &str) {
     flush_stdout();
 }
 
+// thanks https://blog.csdn.net/star_xiong/article/details/89401149
+pub fn find_char_boundary(s: &str, index: usize) -> usize {
+    if s.len() <= index {
+        return index;
+    }
+    let mut new_index = index;
+    while !s.is_char_boundary(new_index) {
+        new_index += 1;
+    }
+    new_index
+}
+
+pub fn get_term_width_message(message: &str, left: usize) -> String {
+    match term_size::dimensions() {
+        None => message.to_string(),
+        Some((w, _h)) => {
+            let len = message.len();
+            if w > len {
+               return message.to_string();
+            }
+            let mut s = String::new();
+            s.push_str(&message[0..find_char_boundary(&message, w-10-5-left)]);
+            s.push_str("[...]");
+            s.push_str(&message[find_char_boundary(&message, len-10)..]);
+            s
+        },
+    }
+}
+
 pub fn parse_size(size: &str) -> XResult<i64> {
     let lower_size = size.to_lowercase();
     let no_last_b_size = if lower_size.ends_with("b") {