Remove lazy_static dependancy (#52)

Author: josephlr

.travis.yml

@@ -102,13 +102,14 @@ matrix:
 
     - rust: nightly
       env: DESCRIPTION="cross-platform build only"
+      # Redox: wait for https://github.com/rust-lang/rust/issues/60139
       install:
         - rustup target add x86_64-sun-solaris
         - rustup target add x86_64-unknown-cloudabi
         - rustup target add x86_64-unknown-freebsd
         - rustup target add x86_64-fuchsia
         - rustup target add x86_64-unknown-netbsd
-        - rustup target add x86_64-unknown-redox
+        # - rustup target add x86_64-unknown-redox
         - rustup target add x86_64-fortanix-unknown-sgx
         # For no_std targets
         - rustup component add rust-src
@@ -119,7 +120,7 @@ matrix:
         - cargo build --target=x86_64-unknown-freebsd --all-features
         - cargo build --target=x86_64-fuchsia --all-features
         - cargo build --target=x86_64-unknown-netbsd --all-features
-        - cargo build --target=x86_64-unknown-redox --all-features
+        # - cargo build --target=x86_64-unknown-redox --all-features
         - cargo build --target=x86_64-fortanix-unknown-sgx --all-features
         - cargo xbuild --target=x86_64-unknown-uefi
         # also test minimum dependency versions are usable
@@ -129,7 +130,7 @@ matrix:
         - cargo build --target=x86_64-unknown-freebsd --all-features
         - cargo build --target=x86_64-fuchsia --all-features
         - cargo build --target=x86_64-unknown-netbsd --all-features
-        - cargo build --target=x86_64-unknown-redox --all-features
+        # - cargo build --target=x86_64-unknown-redox --all-features
         - cargo build --target=x86_64-fortanix-unknown-sgx --all-features
         - cargo xbuild --target=x86_64-unknown-uefi
 

Cargo.toml

@@ -20,17 +20,12 @@ members = ["tests/wasm_bindgen"]
 [dependencies]
 log = { version = "0.4", optional = true }
 
-[target.'cfg(any(unix, target_os = "wasi"))'.dependencies]
+[target.'cfg(any(unix, target_os = "redox", target_os = "wasi"))'.dependencies]
 libc = "0.2.54"
 
-# For holding file descriptors
-[target.'cfg(any(unix, target_os = "redox"))'.dependencies]
-lazy_static = "1.3.0"
-
 [target.wasm32-unknown-unknown.dependencies]
 wasm-bindgen = { version = "0.2.29", optional = true }
 stdweb = { version = "0.4.9", optional = true }
-lazy_static = "1.3.0"
 
 [features]
 std = []

src/lib.rs

@@ -142,11 +142,11 @@ extern crate std;
 
 mod error;
 pub use crate::error::Error;
+
 #[allow(dead_code)]
 mod util;
-
-// These targets need weak linkage to libc randomness functions.
-#[cfg(any(target_os = "macos", target_os = "solaris", target_os = "illumos"))]
+#[cfg(any(unix, target_os = "redox"))]
+#[allow(dead_code)]
 mod util_libc;
 
 // System-specific implementations.

src/use_file.rs

@@ -9,10 +9,15 @@
 //! Implementations that just need to read from a file
 extern crate std;
 
+use crate::util_libc::LazyFd;
 use crate::Error;
+use core::mem::ManuallyDrop;
 use core::num::NonZeroU32;
-use lazy_static::lazy_static;
-use std::{fs::File, io::Read};
+use std::os::unix::io::{FromRawFd, IntoRawFd, RawFd};
+use std::{
+    fs::File,
+    io::{self, Read},
+};
 
 #[cfg(target_os = "redox")]
 const FILE_PATH: &str = "rand:";
@@ -29,28 +34,31 @@ const FILE_PATH: &str = "/dev/urandom";
 const FILE_PATH: &str = "/dev/random";
 
 pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
-    lazy_static! {
-        static ref FILE: Result<File, Error> = init_file();
-    }
-    let mut f = FILE.as_ref()?;
+    static FD: LazyFd = LazyFd::new();
+    let fd = FD.init(init_file).ok_or(io::Error::last_os_error())?;
+    let file = ManuallyDrop::new(unsafe { File::from_raw_fd(fd) });
+    let mut file_ref: &File = &file;
 
     if cfg!(target_os = "emscripten") {
         // `Crypto.getRandomValues` documents `dest` should be at most 65536 bytes.
         for chunk in dest.chunks_mut(65536) {
-            f.read_exact(chunk)?;
+            file_ref.read_exact(chunk)?;
         }
     } else {
-        f.read_exact(dest)?;
+        file_ref.read_exact(dest)?;
     }
     Ok(())
 }
 
-fn init_file() -> Result<File, Error> {
+fn init_file() -> Option<RawFd> {
     if FILE_PATH == "/dev/urandom" {
         // read one byte from "/dev/random" to ensure that OS RNG has initialized
-        File::open("/dev/random")?.read_exact(&mut [0u8; 1])?;
+        File::open("/dev/random")
+            .ok()?
+            .read_exact(&mut [0u8; 1])
+            .ok()?;
     }
-    Ok(File::open(FILE_PATH)?)
+    Some(File::open(FILE_PATH).ok()?.into_raw_fd())
 }
 
 #[inline(always)]

src/util.rs

@@ -6,10 +6,26 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use core::sync::atomic::{AtomicUsize, Ordering};
+use core::sync::atomic::{AtomicUsize, Ordering::Relaxed};
 
 // This structure represents a laziliy initialized static usize value. Useful
 // when it is perferable to just rerun initialization instead of locking.
+// Both unsync_init and sync_init will invoke an init() function until it
+// succeeds, then return the cached value for future calls.
+//
+// Both methods support init() "failing". If the init() method returns UNINIT,
+// that value will be returned as normal, but will not be cached.
+//
+// Users should only depend on the _value_ returned by init() functions.
+// Specifically, for the following init() function:
+//      fn init() -> usize {
+//          a();
+//          let v = b();
+//          c();
+//          v
+//      }
+// the effects of c() or writes to shared memory will not necessarily be
+// observed and additional syncronization methods with be needed.
 pub struct LazyUsize(AtomicUsize);
 
 impl LazyUsize {
@@ -19,20 +35,44 @@ impl LazyUsize {
 
     // The initialization is not completed.
     pub const UNINIT: usize = usize::max_value();
+    // The initialization is currently running.
+    pub const ACTIVE: usize = usize::max_value() - 1;
 
     // Runs the init() function at least once, returning the value of some run
-    // of init(). Unlike std::sync::Once, the init() function may be run
-    // multiple times. If init() returns UNINIT, future calls to unsync_init()
-    // will always retry. This makes UNINIT ideal for representing failure.
+    // of init(). Multiple callers can run their init() functions in parallel.
+    // init() should always return the same value, if it succeeds.
     pub fn unsync_init(&self, init: impl FnOnce() -> usize) -> usize {
         // Relaxed ordering is fine, as we only have a single atomic variable.
-        let mut val = self.0.load(Ordering::Relaxed);
+        let mut val = self.0.load(Relaxed);
         if val == Self::UNINIT {
             val = init();
-            self.0.store(val, Ordering::Relaxed);
+            self.0.store(val, Relaxed);
         }
         val
     }
+
+    // Synchronously runs the init() function. Only one caller will have their
+    // init() function running at a time, and exactly one successful call will
+    // be run. The init() function should never return LazyUsize::ACTIVE.
+    pub fn sync_init(&self, init: impl FnOnce() -> usize, mut wait: impl FnMut()) -> usize {
+        // Common and fast path with no contention. Don't wast time on CAS.
+        match self.0.load(Relaxed) {
+            Self::UNINIT | Self::ACTIVE => {}
+            val => return val,
+        }
+        // Relaxed ordering is fine, as we only have a single atomic variable.
+        loop {
+            match self.0.compare_and_swap(Self::UNINIT, Self::ACTIVE, Relaxed) {
+                Self::UNINIT => {
+                    let val = init();
+                    self.0.store(val, Relaxed);
+                    return val;
+                }
+                Self::ACTIVE => wait(),
+                val => return val,
+            }
+        }
+    }
 }
 
 // Identical to LazyUsize except with bool instead of usize.

src/util_libc.rs

@@ -36,3 +36,29 @@ impl Weak {
         NonNull::new(addr as *mut _)
     }
 }
+
+pub struct LazyFd(LazyUsize);
+
+impl LazyFd {
+    pub const fn new() -> Self {
+        Self(LazyUsize::new())
+    }
+
+    // If init() returns Some(x), x should be nonnegative.
+    pub fn init(&self, init: impl FnOnce() -> Option<libc::c_int>) -> Option<libc::c_int> {
+        let fd = self.0.sync_init(
+            || match init() {
+                // OK as val >= 0 and val <= c_int::MAX < usize::MAX
+                Some(val) => val as usize,
+                None => LazyUsize::UNINIT,
+            },
+            || unsafe {
+                libc::usleep(1000);
+            },
+        );
+        match fd {
+            LazyUsize::UNINIT => None,
+            val => Some(val as libc::c_int),
+        }
+    }
+}

src/wasm32_stdweb.rs

@@ -15,7 +15,7 @@ use stdweb::web::error::Error as WebError;
 use stdweb::{_js_impl, js};
 
 use crate::Error;
-use lazy_static::lazy_static;
+use std::sync::Once;
 
 #[derive(Clone, Copy, Debug)]
 enum RngSource {
@@ -25,11 +25,14 @@ enum RngSource {
 
 pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
     assert_eq!(mem::size_of::<usize>(), 4);
-
-    lazy_static! {
-        static ref RNG_SOURCE: Result<RngSource, Error> = getrandom_init();
-    }
-    getrandom_fill((*RNG_SOURCE)?, dest)
+    static ONCE: Once = Once::new();
+    static mut RNG_SOURCE: Result<RngSource, Error> = Err(Error::UNAVAILABLE);
+
+    // SAFETY: RNG_SOURCE is only written once, before being read.
+    ONCE.call_once(|| unsafe {
+        RNG_SOURCE = getrandom_init();
+    });
+    getrandom_fill(unsafe { RNG_SOURCE }?, dest)
 }
 
 fn getrandom_init() -> Result<RngSource, Error> {