base-coroutine 0.2.0

A fast and safe implementation of stackful coroutines with scheduler which supports preemptive scheduling.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90

// Copyright 2016 coroutine-rs Developers
//
// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
// http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
// http://opensource.org/licenses/MIT>, at your option. This file may not be
// copied, modified, or distributed except according to those terms.

use std::io;
use std::mem;
use std::os::raw::c_void;
use std::sync::atomic::{AtomicUsize, Ordering};
use std::usize;

use windows_sys::Win32::System::Memory::{
    VirtualAlloc, VirtualFree, VirtualProtect, MEM_COMMIT, MEM_RELEASE, MEM_RESERVE, PAGE_GUARD,
    PAGE_PROTECTION_FLAGS, PAGE_READWRITE, VIRTUAL_ALLOCATION_TYPE,
};
use windows_sys::Win32::System::SystemInformation::GetSystemInfo;

use crate::stack::Stack;

pub unsafe fn allocate_stack(size: usize) -> io::Result<Stack> {
    const NULL: *mut c_void = std::ptr::null_mut();
    const TYPE: VIRTUAL_ALLOCATION_TYPE = MEM_COMMIT | MEM_RESERVE;

    let ptr = VirtualAlloc(NULL, size, TYPE, PAGE_READWRITE);

    if ptr == NULL {
        Err(io::Error::last_os_error())
    } else {
        Ok(Stack::new(
            (ptr as usize + size) as *mut c_void,
            ptr as *mut c_void,
        ))
    }
}

pub unsafe fn protect_stack(stack: &Stack) -> io::Result<Stack> {
    const TYPE: PAGE_PROTECTION_FLAGS = PAGE_READWRITE | PAGE_GUARD;

    let page_size = page_size();
    let mut old_prot = 0;

    debug_assert!(stack.len() % page_size == 0 && !stack.is_empty());

    let ret = VirtualProtect(stack.bottom(), page_size, TYPE, &mut old_prot);

    if ret == 0 {
        Err(io::Error::last_os_error())
    } else {
        let bottom = (stack.bottom() as usize + page_size) as *mut c_void;
        Ok(Stack::new(stack.top(), bottom))
    }
}

pub unsafe fn deallocate_stack(ptr: *mut c_void, _: usize) {
    VirtualFree(ptr, 0, MEM_RELEASE);
}

pub fn page_size() -> usize {
    static PAGE_SIZE: AtomicUsize = AtomicUsize::new(0);

    let mut ret = PAGE_SIZE.load(Ordering::Relaxed);

    if ret == 0 {
        ret = unsafe {
            let mut info = mem::zeroed();
            GetSystemInfo(&mut info);
            info.dwPageSize as usize
        };

        PAGE_SIZE.store(ret, Ordering::Relaxed);
    }

    ret
}

// Windows does not seem to provide a stack limit API
pub fn min_stack_size() -> usize {
    page_size()
}

// Windows does not seem to provide a stack limit API
pub fn max_stack_size(protected: bool) -> usize {
    let page_size = page_size();
    let add_shift = i32::from(protected);
    let protected = page_size << add_shift;
    let size = (usize::MAX - 1) & !(page_size - 1);
    size - protected
}