1 files changed, 44 insertions, 0 deletions
diff --git a/rand/rand_jitter/src/platform.rs b/rand/rand_jitter/src/platform.rs
new file mode 100644
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+++ b/rand/rand_jitter/src/platform.rs
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+// Copyright 2018 Developers of the Rand project.
+// Copyright 2013-2015 The Rust Project Developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[cfg(not(any(target_os = "macos", target_os = "ios", target_os = "windows")))]
+pub fn get_nstime() -> u64 {
+    use std::time::{SystemTime, UNIX_EPOCH};
+
+    let dur = SystemTime::now().duration_since(UNIX_EPOCH).unwrap();
+    // The correct way to calculate the current time is
+    // `dur.as_secs() * 1_000_000_000 + dur.subsec_nanos() as u64`
+    // But this is faster, and the difference in terms of entropy is
+    // negligible (log2(10^9) == 29.9).
+    dur.as_secs() << 30 | dur.subsec_nanos() as u64
+}
+
+#[cfg(any(target_os = "macos", target_os = "ios"))]
+pub fn get_nstime() -> u64 {
+    use libc;
+    
+    // On Mac OS and iOS std::time::SystemTime only has 1000ns resolution.
+    // We use `mach_absolute_time` instead. This provides a CPU dependent
+    // unit, to get real nanoseconds the result should by multiplied by
+    // numer/denom from `mach_timebase_info`.
+    // But we are not interested in the exact nanoseconds, just entropy. So
+    // we use the raw result.
+    unsafe { libc::mach_absolute_time() }
+}
+
+#[cfg(target_os = "windows")]
+pub fn get_nstime() -> u64 {
+    use winapi;
+
+    unsafe {
+        let mut t = super::mem::zeroed();
+        winapi::um::profileapi::QueryPerformanceCounter(&mut t);
+        *t.QuadPart() as u64
+    }
+}