Merge pull request rust-lang#3096 from otavio/use-bytecount-count

utils: rewrite `count_newlines` using `bytecount::count`

Author: nrc

Cargo.lock

@@ -51,6 +51,7 @@ rustc-ap-rustc_target = "272.0.0"
 rustc-ap-syntax = "272.0.0"
 rustc-ap-syntax_pos = "272.0.0"
 failure = "0.1.1"
+bytecount = { version = "0.3", features = ["simd-accel"] }
 
 [dev-dependencies]
 assert_cli = "0.6"

Cargo.toml

@@ -17,6 +17,7 @@
 #[macro_use]
 extern crate derive_new;
 extern crate atty;
+extern crate bytecount;
 extern crate diff;
 extern crate failure;
 extern crate itertools;

src/lib.rs

@@ -10,6 +10,8 @@
 
 use std::borrow::Cow;
 
+use bytecount;
+
 use rustc_target::spec::abi;
 use syntax::ast::{
     self, Attribute, CrateSugar, MetaItem, MetaItemKind, NestedMetaItem, NestedMetaItemKind, Path,
@@ -305,8 +307,8 @@ pub fn stmt_expr(stmt: &ast::Stmt) -> Option<&ast::Expr> {
 
 #[inline]
 pub fn count_newlines(input: &str) -> usize {
-    // Using `as_bytes` to omit UTF-8 decoding
-    input.as_bytes().iter().filter(|&&c| c == b'\n').count()
+    // Using bytes to omit UTF-8 decoding
+    bytecount::count(input.as_bytes(), b'\n')
 }
 
 // For format_missing and last_pos, need to use the source callsite (if applicable).