From 30b9a7852092f7201de5f764ecf5af9c78fff8a0 Mon Sep 17 00:00:00 2001
From: Jiahao XU <Jiahao_XU@outlook.com>
Date: Wed, 15 Jun 2022 17:45:50 +1000
Subject: [PATCH] Optimize `normalize_path`: Avoid copy if possible

Signed-off-by: Jiahao XU <Jiahao_XU@outlook.com>
---
 src/drivers/visitor.rs  |  3 ++-
 src/helpers/path_ext.rs | 26 ++++++++++++++++++++++----
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/src/drivers/visitor.rs b/src/drivers/visitor.rs
index 850d7c39..3f354771 100644
--- a/src/drivers/visitor.rs
+++ b/src/drivers/visitor.rs
@@ -49,7 +49,8 @@ impl TarEntriesVisitor for ManifestVisitor {
     fn visit<R: Read>(&mut self, entries: Entries<'_, R>) -> Result<(), BinstallError> {
         for res in entries {
             let mut entry = res?;
-            let path = entry.path()?.normalize_path();
+            let path = entry.path()?;
+            let path = path.normalize_path();
 
             let path = if let Ok(path) = path.strip_prefix(&self.manifest_dir_path) {
                 path
diff --git a/src/helpers/path_ext.rs b/src/helpers/path_ext.rs
index 1e5d2cc7..bf223280 100644
--- a/src/helpers/path_ext.rs
+++ b/src/helpers/path_ext.rs
@@ -1,16 +1,34 @@
-//! Shamelessly taken from:
+//! Shamelessly adapted from:
 //! https://github.com/rust-lang/cargo/blob/fede83ccf973457de319ba6fa0e36ead454d2e20/src/cargo/util/paths.rs#L61
 
+use std::borrow::Cow;
 use std::path::{Component, Path, PathBuf};
 
 pub trait PathExt {
     /// Similiar to `os.path.normpath`: It does not perform
     /// any fs operation.
-    fn normalize_path(&self) -> PathBuf;
+    fn normalize_path(&self) -> Cow<'_, Path>;
+}
+
+fn is_normalized(path: &Path) -> bool {
+    for component in path.components() {
+        match component {
+            Component::CurDir | Component::ParentDir => {
+                return false;
+            }
+            _ => continue,
+        }
+    }
+
+    true
 }
 
 impl PathExt for Path {
-    fn normalize_path(&self) -> PathBuf {
+    fn normalize_path(&self) -> Cow<'_, Path> {
+        if is_normalized(self) {
+            return Cow::Borrowed(self);
+        }
+
         let mut components = self.components().peekable();
         let mut ret = if let Some(c @ Component::Prefix(..)) = components.peek().cloned() {
             components.next();
@@ -34,6 +52,6 @@ impl PathExt for Path {
                 }
             }
         }
-        ret
+        Cow::Owned(ret)
     }
 }