From d824de1935ac80982ec0f14d18c491aa47dcbe09 Mon Sep 17 00:00:00 2001
From: Erick Tryzelaar <erick.tryzelaar@gmail.com>
Date: Thu, 16 Apr 2015 21:46:22 -0700
Subject: [PATCH] collections: Move optimized String::from_str to String::from

This implementation is currently about 3-4 times faster than using
the `.to_string()` based approach.
---
 src/libcollections/string.rs     |  2 +-
 src/libcollectionstest/string.rs | 29 ++++++++++++++++++++++++++++-
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/src/libcollections/string.rs b/src/libcollections/string.rs
index 51ce5564c49c5..886b14d8cfd9d 100644
--- a/src/libcollections/string.rs
+++ b/src/libcollections/string.rs
@@ -1015,7 +1015,7 @@ impl AsRef<str> for String {
 impl<'a> From<&'a str> for String {
     #[inline]
     fn from(s: &'a str) -> String {
-        s.to_string()
+        String { vec: <[_]>::to_vec(s.as_bytes()) }
     }
 }
 
diff --git a/src/libcollectionstest/string.rs b/src/libcollectionstest/string.rs
index 3184f842e9ae9..389fe85eb72cd 100644
--- a/src/libcollectionstest/string.rs
+++ b/src/libcollectionstest/string.rs
@@ -13,7 +13,7 @@ use std::iter::repeat;
 use std::str::Utf8Error;
 use std::string::as_string;
 
-use test::Bencher;
+use test::{self, Bencher};
 
 #[test]
 fn test_as_string() {
@@ -450,3 +450,30 @@ fn bench_exact_size_shrink_to_fit(b: &mut Bencher) {
         r
     });
 }
+
+#[bench]
+fn bench_from_str(b: &mut Bencher) {
+    let s = "Hello there, the quick brown fox jumped over the lazy dog! \
+             Lorem ipsum dolor sit amet, consectetur. ";
+    b.iter(|| {
+        test::black_box(String::from_str(s));
+    })
+}
+
+#[bench]
+fn bench_from(b: &mut Bencher) {
+    let s = "Hello there, the quick brown fox jumped over the lazy dog! \
+             Lorem ipsum dolor sit amet, consectetur. ";
+    b.iter(|| {
+        test::black_box(String::from(s));
+    })
+}
+
+#[bench]
+fn bench_to_string(b: &mut Bencher) {
+    let s = "Hello there, the quick brown fox jumped over the lazy dog! \
+             Lorem ipsum dolor sit amet, consectetur. ";
+    b.iter(|| {
+        test::black_box(s.to_string());
+    })
+}