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// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

use crate::sys::futex as imp;
use crate::Timespec;
use core::marker::PhantomData;
use core::sync::atomic::AtomicU32;
use core::time::Duration;
use sgx_types::error::OsResult;

impl_enum! {
    #[repr(u32)]
    #[derive(Clone, Copy, Debug, Eq, PartialEq)]
    pub enum FutexOp {
        Wait = 0,
        Wake = 1,
        Fd = 2,
        Requeue = 3,
        CmpRequeue = 4,
        WakeOp = 5,
        LockPI = 6,
        UnlockPI = 7,
        TryLockPI = 8,
        WaitBitset = 9,
        WakeBitset = 10,
        WaitRequeuePI = 11,
        CmpRequeuePI = 12,
    }
}

impl_bitflags! {
    #[repr(C)]
    #[derive(Clone, Copy, Debug, Eq, PartialEq)]
    pub struct FutexFlags: u32 {
        const PRIVATE = 0x80;
        const CLOCK_REALTIME = 0x100;
    }
}

impl From<FutexFlags> for FutexClockId {
    fn from(flags: FutexFlags) -> FutexClockId {
        if flags.contains(FutexFlags::CLOCK_REALTIME) {
            FutexClockId::RealTime
        } else {
            FutexClockId::Monotonic
        }
    }
}

impl_enum! {
    #[repr(u32)]
    #[derive(Clone, Copy, Debug, Eq, PartialEq)]
    pub enum FutexClockId {
        Monotonic = 0,
        RealTime = 0x100,
    }
}

pub struct Futex<'a> {
    futex: imp::Futex,
    marker: PhantomData<&'a AtomicU32>,
}

impl<'a> Futex<'a> {
    pub fn new(futex: &AtomicU32) -> Futex<'a> {
        Futex {
            futex: imp::Futex::new(futex as *const _ as usize),
            marker: PhantomData,
        }
    }

    #[inline]
    pub fn wait(&self, expected: u32, timeout: Option<Duration>) -> OsResult {
        self.futex.wait(expected, timeout)
    }

    #[inline]
    pub fn wait_bitset(
        &self,
        expected: u32,
        timeout: Option<(Timespec, FutexClockId)>,
        bitset: u32,
    ) -> OsResult {
        self.futex.wait_bitset(expected, timeout, bitset)
    }

    #[inline]
    pub fn wake(self, count: i32) -> OsResult<usize> {
        self.futex.wake(count as usize)
    }

    #[inline]
    pub fn wake_bitset(self, count: i32, bitset: u32) -> OsResult<usize> {
        self.futex.wake_bitset(count as usize, bitset)
    }

    #[inline]
    pub fn cmp_requeue(
        &self,
        nwakes: i32,
        new_futex: &Futex,
        nrequeues: i32,
        expected: u32,
    ) -> OsResult<usize> {
        self.futex.cmp_requeue(
            nwakes as usize,
            &new_futex.futex,
            nrequeues as usize,
            expected,
        )
    }

    #[inline]
    pub fn requeue(&self, nwakes: i32, new_futex: &Futex, nrequeues: i32) -> OsResult<usize> {
        self.futex
            .requeue(nwakes as usize, &new_futex.futex, nrequeues as usize)
    }
}