src/tools/rust-analyzer/crates/profile/src/google_cpu_profiler.rs

   1 //! https://github.com/gperftools/gperftools
   2
   3 use std::{
   4     ffi::CString,
   5     os::raw::c_char,
   6     path::Path,
   7     sync::atomic::{AtomicUsize, Ordering},
   8 };
   9
  10 #[link(name = "profiler")]
  11 #[allow(non_snake_case)]
  12 extern "C" {
  13     fn ProfilerStart(fname: *const c_char) -> i32;
  14     fn ProfilerStop();
  15 }
  16
  17 const OFF: usize = 0;
  18 const ON: usize = 1;
  19 const PENDING: usize = 2;
  20
  21 fn transition(current: usize, new: usize) -> bool {
  22     static STATE: AtomicUsize = AtomicUsize::new(OFF);
  23
  24     STATE.compare_exchange(current, new, Ordering::SeqCst, Ordering::SeqCst).is_ok()
  25 }
  26
  27 pub(crate) fn start(path: &Path) {
  28     if !transition(OFF, PENDING) {
  29         panic!("profiler already started");
  30     }
  31     let path = CString::new(path.display().to_string()).unwrap();
  32     if unsafe { ProfilerStart(path.as_ptr()) } == 0 {
  33         panic!("profiler failed to start")
  34     }
  35     assert!(transition(PENDING, ON));
  36 }
  37
  38 pub(crate) fn stop() {
  39     if !transition(ON, PENDING) {
  40         panic!("profiler is not started")
  41     }
  42     unsafe { ProfilerStop() };
  43     assert!(transition(PENDING, OFF));
  44 }