Rollup merge of rust-lang#47328 - mbrubeck:fs_read, r=sfackler

Use the new fs_read_write functions in rustc internals

Uses `fs::read` and `fs::write` (added by rust-lang#45837) where appropriate, to simplify code and dog-food these new APIs.  This also improves performance, when combined with rust-lang#47324.

Author: kennytm

src/librustc/lib.rs

@@ -48,6 +48,7 @@
 #![feature(drain_filter)]
 #![feature(dyn_trait)]
 #![feature(from_ref)]
+#![feature(fs_read_write)]
 #![feature(i128)]
 #![feature(i128_type)]
 #![feature(inclusive_range)]

src/librustc/util/common.rs

@@ -218,13 +218,10 @@ pub fn record_time<T, F>(accu: &Cell<Duration>, f: F) -> T where
 // Memory reporting
 #[cfg(unix)]
 fn get_resident() -> Option<usize> {
-    use std::fs::File;
-    use std::io::Read;
+    use std::fs;
 
     let field = 1;
-    let mut f = File::open("/proc/self/statm").ok()?;
-    let mut contents = String::new();
-    f.read_to_string(&mut contents).ok()?;
+    let contents = fs::read_string("/proc/self/statm").ok()?;
     let s = contents.split_whitespace().nth(field)?;
     let npages = s.parse::<usize>().ok()?;
     Some(npages * 4096)

src/librustc_back/lib.rs

@@ -28,6 +28,7 @@
 
 #![feature(box_syntax)]
 #![feature(const_fn)]
+#![feature(fs_read_write)]
 
 extern crate syntax;
 extern crate rand;

src/librustc_back/target/mod.rs

@@ -47,7 +47,6 @@
 use serialize::json::{Json, ToJson};
 use std::collections::BTreeMap;
 use std::default::Default;
-use std::io::prelude::*;
 use syntax::abi::{Abi, lookup as lookup_abi};
 
 use {LinkerFlavor, PanicStrategy, RelroLevel};
@@ -811,14 +810,12 @@ impl Target {
     pub fn search(target: &str) -> Result<Target, String> {
         use std::env;
         use std::ffi::OsString;
-        use std::fs::File;
+        use std::fs;
         use std::path::{Path, PathBuf};
         use serialize::json;
 
         fn load_file(path: &Path) -> Result<Target, String> {
-            let mut f = File::open(path).map_err(|e| e.to_string())?;
-            let mut contents = Vec::new();
-            f.read_to_end(&mut contents).map_err(|e| e.to_string())?;
+            let contents = fs::read(path).map_err(|e| e.to_string())?;
             let obj = json::from_reader(&mut &contents[..])
                            .map_err(|e| e.to_string())?;
             Target::from_json(obj)

src/librustc_incremental/assert_dep_graph.rs

@@ -55,7 +55,7 @@ use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
 use rustc::ich::{ATTR_IF_THIS_CHANGED, ATTR_THEN_THIS_WOULD_NEED};
 use graphviz::IntoCow;
 use std::env;
-use std::fs::File;
+use std::fs::{self, File};
 use std::io::Write;
 use syntax::ast;
 use syntax_pos::Span;
@@ -260,7 +260,7 @@ fn dump_graph(tcx: TyCtxt) {
         let dot_path = format!("{}.dot", path);
         let mut v = Vec::new();
         dot::render(&GraphvizDepGraph(nodes, edges), &mut v).unwrap();
-        File::create(&dot_path).and_then(|mut f| f.write_all(&v)).unwrap();
+        fs::write(dot_path, v).unwrap();
     }
 }
 

src/librustc_incremental/lib.rs

@@ -16,6 +16,7 @@
 #![deny(warnings)]
 
 #![feature(conservative_impl_trait)]
+#![feature(fs_read_write)]
 #![feature(i128_type)]
 #![feature(inclusive_range_syntax)]
 #![feature(specialization)]

src/librustc_incremental/persist/file_format.rs

@@ -21,7 +21,7 @@
 
 use std::io::{self, Read};
 use std::path::Path;
-use std::fs::File;
+use std::fs;
 use std::env;
 
 use rustc::session::config::nightly_options;
@@ -66,11 +66,7 @@ pub fn read_file(report_incremental_info: bool, path: &Path)
         return Ok(None);
     }
 
-    let mut file = File::open(path)?;
-    let file_size = file.metadata()?.len() as usize;
-
-    let mut data = Vec::with_capacity(file_size);
-    file.read_to_end(&mut data)?;
+    let data = fs::read(path)?;
 
     let mut file = io::Cursor::new(data);
 

src/librustc_incremental/persist/save.rs

@@ -15,8 +15,8 @@ use rustc::util::common::time;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_serialize::Encodable as RustcEncodable;
 use rustc_serialize::opaque::Encoder;
-use std::io::{self, Cursor, Write};
-use std::fs::{self, File};
+use std::io::{self, Cursor};
+use std::fs;
 use std::path::PathBuf;
 
 use super::data::*;
@@ -125,7 +125,7 @@ fn save_in<F>(sess: &Session, path_buf: PathBuf, encode: F)
 
     // write the data out
     let data = wr.into_inner();
-    match File::create(&path_buf).and_then(|mut file| file.write_all(&data)) {
+    match fs::write(&path_buf, data) {
         Ok(_) => {
             debug!("save: data written to disk successfully");
         }

src/librustc_metadata/lib.rs

@@ -15,6 +15,7 @@
 
 #![feature(box_patterns)]
 #![feature(conservative_impl_trait)]
+#![feature(fs_read_write)]
 #![feature(i128_type)]
 #![feature(libc)]
 #![feature(proc_macro_internals)]

src/librustc_metadata/locator.rs

@@ -237,7 +237,7 @@ use rustc_back::target::Target;
 
 use std::cmp;
 use std::fmt;
-use std::fs::{self, File};
+use std::fs;
 use std::io::{self, Read};
 use std::path::{Path, PathBuf};
 use std::time::Instant;
@@ -870,10 +870,7 @@ fn get_metadata_section_imp(target: &Target,
             }
         }
         CrateFlavor::Rmeta => {
-            let mut file = File::open(filename).map_err(|_|
-                format!("could not open file: '{}'", filename.display()))?;
-            let mut buf = vec![];
-            file.read_to_end(&mut buf).map_err(|_|
+            let buf = fs::read(filename).map_err(|_|
                 format!("failed to read rmeta metadata: '{}'", filename.display()))?;
             OwningRef::new(buf).map_owner_box().erase_owner()
         }