common::str::get_chars with test

Author: youknowone

common/src/lib.rs

@@ -4,3 +4,4 @@ pub mod cell;
 pub mod float_ops;
 pub mod hash;
 pub mod rc;
+pub mod str;

common/src/str.rs

@@ -0,0 +1,30 @@
+pub fn get_chars(s: &str, range: std::ops::Range<usize>) -> &str {
+    let mut chars = s.chars();
+    for _ in 0..range.start {
+        let _ = chars.next();
+    }
+    let start = chars.as_str();
+    for _ in range {
+        let _ = chars.next();
+    }
+    let end = chars.as_str();
+    &start[..start.len() - end.len()]
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_get_chars() {
+        let s = "0123456789";
+        assert_eq!(get_chars(s, 3..7), "3456");
+        assert_eq!(get_chars(s, 3..7), &s[3..7]);
+
+        let s = "0유니코드 문자열9";
+        assert_eq!(get_chars(s, 3..7), "코드 문");
+
+        let s = "0😀😃😄😁😆😅😂🤣9";
+        assert_eq!(get_chars(s, 3..7), "😄😁😆😅");
+    }
+}

vm/src/obj/objstr.rs

@@ -1406,16 +1406,7 @@ impl<'s> PyCommonString<'s, char> for str {
     }
 
     fn get_chars<'a>(&'a self, range: std::ops::Range<usize>) -> &'a Self {
-        let mut chars = self.chars();
-        for _ in 0..range.start {
-            let _ = chars.next();
-        }
-        let start = chars.as_str();
-        for _ in range {
-            let _ = chars.next();
-        }
-        let end = chars.as_str();
-        &start[..start.len() - end.len()]
+        rustpython_common::str::get_chars(self, range)
     }
 
     fn is_empty(&self) -> bool {