Add width() function.

Author: AldaronLau

Cargo.toml

@@ -3,7 +3,6 @@ name = "unicode-columns"
 version = "0.1.0"
 edition = "2021"
 
-# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
 unicode-width = "0.1"

src/lib.rs

@@ -1,26 +1,53 @@
 use unicode_width::UnicodeWidthChar;
 
+const ZWJ: u32 = 0x200d;
+
+/// Get the column width of a string
+pub fn width(string: &str) -> usize {
+    let mut cw = 0;
+    let mut iter = string.chars();
+    while let Some(c) = iter.next() {
+        if u32::from(c) == ZWJ {
+            iter.next();
+            continue;
+        }
+        cw += c.width().unwrap_or(0);
+    }
+    cw
+}
+
 /// Truncate a string to a specific column width
 pub fn truncate(string: &str, width: usize) -> &str {
     let mut cw = 0;
     let mut iter = string.char_indices();
     while let Some((i, c)) = iter.next() {
-        if u32::from(c) == /* ZWJ */ 0x200d {
+        if u32::from(c) == ZWJ {
             iter.next();
             continue;
         }
-        let nw = cw + c.width().unwrap_or(0);
-        if nw > width {
+        cw += c.width().unwrap_or(0);
+        if cw > width {
             return &string[..i];
         }
-        cw = nw;
     }
     string
 }
 
 #[cfg(test)]
 mod tests {
-    use crate::truncate;
+    use super::*;
+
+    #[test]
+    fn test_width() {
+        // basic tests
+        assert_eq!(width("teststring"), 10);
+        // full-width (2 column) characters test
+        assert_eq!(width("잘라야"), 6);
+        // combining characters (zalgo text) test
+        assert_eq!(width("ę̵̡̛̮̹̼̝̲͓̳̣͉̞͔̳̥̝͍̩̣̹͙̘̼̥̗̼͈̯͎̮̥̤̪̻̮͕̩̮͓͔̟͈͇͎̣͉͇̦͔̝̣͎͎͔͇̭͈̌̂̈̄̈́̾͑̀̈̓̂͗̾̉͊͒̆̽͊̽͘̕͜͜͝͠ :width"), 8);
+        // zero-width-joiner (emoji) test
+        assert_eq!(width("👨‍👩‍👦:width"), 8);
+    }
 
     #[test]
     fn test_truncation() {