// This file is part of libfringe, a low-level green threading library.
// Copyright (c) edef <edef@edef.eu>
// See the LICENSE file included in this distribution.
extern crate std;
extern crate libc;
use self::std::io::Error as IoError;
use self::libc::{c_void, c_int, size_t};
use self::libc::{mmap, mprotect, munmap};
use self::libc::MAP_FAILED;
use super::page_size;

use core::ptr;

#[cold]
pub fn sys_page_size() -> usize {
  unsafe {
    libc::sysconf(libc::_SC_PAGESIZE) as usize
  }
}

const GUARD_PROT:  c_int = libc::PROT_NONE;
const STACK_PROT:  c_int = libc::PROT_READ
                         | libc::PROT_WRITE;
#[cfg(not(any(target_os = "freebsd", target_os = "dragonfly")))]
const STACK_FLAGS: c_int = libc::MAP_STACK
                         | libc::MAP_PRIVATE
                         | libc::MAP_ANON;
// workaround for http://lists.freebsd.org/pipermail/freebsd-bugs/2011-July/044840.html
// according to libgreen, DragonFlyBSD suffers from this too
#[cfg(any(target_os = "freebsd", target_os = "dragonfly"))]
const STACK_FLAGS: c_int = libc::MAP_PRIVATE
                         | libc::MAP_ANON;

pub unsafe fn map_stack(len: usize) -> Result<*mut u8, IoError> {
  let ptr = mmap(ptr::null_mut(), len as size_t, STACK_PROT, STACK_FLAGS, -1, 0);
  if ptr == MAP_FAILED {
    Err(IoError::last_os_error())
  } else {
    Ok(ptr as *mut u8)
  }
}

pub unsafe fn protect_stack(ptr: *mut u8) -> Result<(), IoError> {
  if mprotect(ptr as *mut c_void, page_size() as size_t, GUARD_PROT) == 0 {
    Ok(())
  } else {
    Err(IoError::last_os_error())
  }
}

pub unsafe fn unmap_stack(ptr: *mut u8, len: usize) -> Result<(), IoError> {
  if munmap(ptr as *mut c_void, len as size_t) == 0 {
    Ok(())
  } else {
    Err(IoError::last_os_error())
  }
}