src/libstd/sys/wasm/thread.rs

   1 // Copyright 2017 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use boxed::FnBox;
  12 use ffi::CStr;
  13 use io;
  14 use sys::{unsupported, Void};
  15 use time::Duration;
  16
  17 pub struct Thread(Void);
  18
  19 pub const DEFAULT_MIN_STACK_SIZE: usize = 4096;
  20
  21 impl Thread {
  22     pub unsafe fn new<'a>(_stack: usize, _p: Box<dyn FnBox() + 'a>)
  23         -> io::Result<Thread>
  24     {
  25         unsupported()
  26     }
  27
  28     pub fn yield_now() {
  29         // do nothing
  30     }
  31
  32     pub fn set_name(_name: &CStr) {
  33         // nope
  34     }
  35
  36     #[cfg(not(target_feature = "atomics"))]
  37     pub fn sleep(_dur: Duration) {
  38         panic!("can't sleep");
  39     }
  40
  41     #[cfg(target_feature = "atomics")]
  42     pub fn sleep(dur: Duration) {
  43         use arch::wasm32::atomic;
  44         use cmp;
  45
  46         // Use an atomic wait to block the current thread artificially with a
  47         // timeout listed. Note that we should never be notified (return value
  48         // of 0) or our comparison should never fail (return value of 1) so we
  49         // should always only resume execution through a timeout (return value
  50         // 2).
  51         let mut nanos = dur.as_nanos();
  52         while nanos > 0 {
  53             let amt = cmp::min(i64::max_value() as u128, nanos);
  54             let mut x = 0;
  55             let val = unsafe { atomic::wait_i32(&mut x, 0, amt as i64) };
  56             debug_assert_eq!(val, 2);
  57             nanos -= amt;
  58         }
  59     }
  60
  61     pub fn join(self) {
  62         match self.0 {}
  63     }
  64 }
  65
  66 pub mod guard {
  67     pub type Guard = !;
  68     pub unsafe fn current() -> Option<Guard> { None }
  69     pub unsafe fn init() -> Option<Guard> { None }
  70     pub unsafe fn deinit() {}
  71 }
  72
  73 cfg_if! {
  74     if #[cfg(all(target_feature = "atomics", feature = "wasm-bindgen-threads"))] {
  75         #[link(wasm_import_module = "__wbindgen_thread_xform__")]
  76         extern {
  77             fn __wbindgen_current_id() -> u32;
  78             fn __wbindgen_tcb_get() -> u32;
  79             fn __wbindgen_tcb_set(ptr: u32);
  80         }
  81         pub fn my_id() -> u32 {
  82             unsafe { __wbindgen_current_id() }
  83         }
  84
  85         // These are currently only ever used in `thread_local_atomics.rs`, if
  86         // you'd like to use them be sure to update that and make sure everyone
  87         // agrees what's what.
  88         pub fn tcb_get() -> *mut u8 {
  89             use mem;
  90             assert_eq!(mem::size_of::<*mut u8>(), mem::size_of::<u32>());
  91             unsafe { __wbindgen_tcb_get() as *mut u8 }
  92         }
  93
  94         pub fn tcb_set(ptr: *mut u8) {
  95             unsafe { __wbindgen_tcb_set(ptr as u32); }
  96         }
  97
  98         // FIXME: still need something for hooking exiting a thread to free
  99         // data...
 100
 101     } else if #[cfg(target_feature = "atomics")] {
 102         pub fn my_id() -> u32 {
 103             panic!("thread ids not implemented on wasm with atomics yet")
 104         }
 105
 106         pub fn tcb_get() -> *mut u8 {
 107             panic!("thread local data not implemented on wasm with atomics yet")
 108         }
 109
 110         pub fn tcb_set(ptr: *mut u8) {
 111             panic!("thread local data not implemented on wasm with atomics yet")
 112         }
 113     } else {
 114         // stubbed out because no functions actually access these intrinsics
 115         // unless atomics are enabled
 116     }
 117 }