From 89bbaf460cd1df53eb2af0eab74793b263248edd Mon Sep 17 00:00:00 2001
From: Dan Gohman <dev@sunfishcode.online>
Date: Thu, 18 Feb 2021 08:25:03 -0800
Subject: [PATCH] Add a convenient wrapper for calling
 `QueryPerformanceFrequency`.

---
 Cargo.toml  |  1 +
 src/lib.rs  |  2 ++
 src/time.rs | 17 +++++++++++++++++
 3 files changed, 20 insertions(+)
 create mode 100644 src/time.rs

diff --git a/Cargo.toml b/Cargo.toml
index e1fb776..610dca3 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -21,6 +21,7 @@ features = [
   "fileapi",
   "minwindef",
   "processenv",
+  "profileapi",
   "winbase",
   "wincon",
   "winerror",
diff --git a/src/lib.rs b/src/lib.rs
index 0bb259d..9e57a31 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -29,4 +29,6 @@ pub mod console;
 #[cfg(windows)]
 pub mod file;
 #[cfg(windows)]
+pub mod time;
+#[cfg(windows)]
 mod win;
diff --git a/src/time.rs b/src/time.rs
new file mode 100644
index 0000000..1e0918e
--- /dev/null
+++ b/src/time.rs
@@ -0,0 +1,17 @@
+use std::io;
+use std::mem;
+
+use winapi::um::{
+    profileapi::QueryPerformanceFrequency, winnt::LARGE_INTEGER,
+};
+
+pub fn perf_counter_frequency() -> io::Result<u64> {
+    unsafe {
+        let mut frequency: LARGE_INTEGER = mem::zeroed();
+        let rc = QueryPerformanceFrequency(&mut frequency);
+        if rc == 0 {
+            return Err(io::Error::last_os_error());
+        };
+        Ok(*frequency.QuadPart() as u64)
+    }
+}