refactor: ♻️ extract trim-related functions to its own module

crates/rsjudge-judger/src/comparer/default_comparer.rs

@@ -7,8 +7,9 @@ use tokio::{
 };
 use tokio_stream::{wrappers::SplitStream, StreamExt as _};
 
-use crate::{CompareResult, Comparer};
+use crate::{utils::trim::slice::trim_ascii_end, CompareResult, Comparer};
 
+///
 pub struct DefaultComparer {
     ignore_trailing_whitespace: bool,
     ignore_trailing_newline: bool,
@@ -22,21 +23,10 @@ impl DefaultComparer {
         }
     }
     fn compare_line(&self, out_line: impl AsRef<[u8]>, ans_line: impl AsRef<[u8]>) -> bool {
-        fn trim_end(line: &[u8]) -> &[u8] {
-            if line.is_empty() {
-                line
-            } else {
-                let end = line
-                    .iter()
-                    .rposition(|c| !c.is_ascii_whitespace())
-                    .unwrap_or_else(|| line.len() - 1);
-                &line[..=end]
-            }
-        }
         let out_line = out_line.as_ref();
         let ans_line = ans_line.as_ref();
         let (out_line, ans_line) = if self.ignore_trailing_whitespace {
-            (trim_end(out_line), trim_end(ans_line))
+            (trim_ascii_end(out_line), trim_ascii_end(ans_line))
         } else {
             (out_line, ans_line)
         };
@@ -68,17 +58,17 @@ impl Comparer for DefaultComparer {
                         return Ok(CompareResult::WrongAnswer);
                     }
                 }
-                (Some(out_line), None) => {
+                (Some(out_line), _) => {
                     if !self.ignore_trailing_newline || !self.compare_line(&out_line?, []) {
                         return Ok(CompareResult::WrongAnswer);
                     }
                 }
-                (None, Some(ans_line)) => {
+                (_, Some(ans_line)) => {
                     if !self.ignore_trailing_newline || !self.compare_line([], &ans_line?) {
                         return Ok(CompareResult::WrongAnswer);
                     }
                 }
-                (None, None) => return Ok(CompareResult::Accepted),
+                _ => return Ok(CompareResult::Accepted),
             }
         }
     }

crates/rsjudge-judger/src/lib.rs

@@ -1,3 +1,4 @@
 pub mod comparer;
+mod utils;
 
 pub use comparer::{default_comparer::DefaultComparer, CompareResult, Comparer};

crates/rsjudge-judger/src/utils/mod.rs

@@ -0,0 +1 @@
+pub(crate) mod trim;

crates/rsjudge-judger/src/utils/trim.rs

@@ -0,0 +1 @@
+pub(crate) mod slice;

crates/rsjudge-judger/src/utils/trim/slice.rs

@@ -0,0 +1,36 @@
+#![allow(dead_code)]
+
+#[inline]
+pub(crate) const fn trim_ascii_start(input: &[u8]) -> &[u8] {
+    let mut bytes = input;
+    // Note: A pattern matching based approach (instead of indexing) allows
+    // making the function const.
+    while let [first, rest @ ..] = bytes {
+        if first.is_ascii_whitespace() {
+            bytes = rest;
+        } else {
+            break;
+        }
+    }
+    bytes
+}
+
+#[inline]
+pub(crate) const fn trim_ascii_end(input: &[u8]) -> &[u8] {
+    let mut bytes = input;
+    // Note: A pattern matching based approach (instead of indexing) allows
+    // making the function const.
+    while let [rest @ .., last] = bytes {
+        if last.is_ascii_whitespace() {
+            bytes = rest;
+        } else {
+            break;
+        }
+    }
+    bytes
+}
+
+#[inline]
+pub(crate) const fn trim_ascii(input: &[u8]) -> &[u8] {
+    trim_ascii_end(trim_ascii_start(input))
+}