///////////////////////////////////////////////////////////////////////////////
//
//  Microsoft Research Singularity
//
//  Copyright (c) Microsoft Corporation.  All rights reserved.
//
//  File:   IoIrq.cs
//

//#define DEBUG_DISPATCH_IO

using System;
using System.Runtime.CompilerServices;
using System.Threading;
using Microsoft.Singularity.Hal;

namespace Microsoft.Singularity.Io
{
    [CLSCompliant(false)]
    public sealed class IoIrq
    {
        private readonly byte irq;
        private AutoResetEvent! signal;
        private IoIrq next;

        //////////////////////////////////////////////////////////////////////
        //
        //
        private const int MaxInterrupts = 256;
        private static IoIrq[]! registered;
        private static SpinLock regLock;

        static IoIrq()
        {
            registered = new IoIrq [MaxInterrupts];
            regLock = new SpinLock();
        }

        [NoHeapAllocation]
        private static bool AcquireLock()
        {
            bool enabled = Processor.DisableInterrupts();
#if SINGULARITY_MP
            regLock.Acquire();
#endif // SINGULARITY_MP
            return enabled;
        }

        [NoHeapAllocation]
        private static void ReleaseLock(bool enabled)
        {
#if SINGULARITY_MP
            regLock.Release();
#endif // SINGULARITY_MP
            Processor.RestoreInterrupts(enabled);
        }

        // This doesn't need a lock because Register and Release
        // insure that the list is *always* valid (even when being updated).
        [NoHeapAllocation]
        public static void SignalInterrupt(byte irq)
        {
#if DEBUG_DISPATCH_IO
            DebugStub.WriteLine("++ SetInterruptEvent: Irq={0:x2}", __arglist(irq));
#endif
            for (IoIrq step = registered[irq]; step != null; step = step.next) {
                step.signal.Set();
            }
        }

        public IoIrq(byte irq)
        {
            this.irq = irq;
            this.next = null;
            this.signal = new AutoResetEvent(false);
        }

        public byte Irq
        {
            [NoHeapAllocation]
            get { return irq; }
        }

        // Insert the IoIrq into the linked list for this irq.
        // If it is the first entry, then notify HAL to enable its irq.
        // Returns true if this IoIrq caused the irq to be enabled.
        public bool RegisterInterrupt()
        {
            bool enabled = AcquireLock();
            try {
                Tracing.Log(Tracing.Debug, "Register Irq={0:x2}", irq);
#if DEBUG_DISPATCH_IO
                DebugStub.WriteLine("++ Register Irq={0:x2}", __arglist(irq));
#endif

                next = registered[irq];
                registered[irq] = this;

                if (next == null) {
                    HalDevices.EnableIoInterrupt(irq);
                    return true;
                }
            }
            finally {
                ReleaseLock(enabled);
            }
            return false;
        }

        // Remove the IoIrq into the linked list for this irq.
        // If it is the last entry, then notify HAL to disable its irq.
        // Returns true if this IoIrq caused the irq to be disabled.
        public bool ReleaseInterrupt()
        {
            bool enabled = AcquireLock();
            try {
                Tracing.Log(Tracing.Debug, "Release Irq={0:x2}", irq);
#if DEBUG_DISPATCH_IO
                DebugStub.WriteLine("++ Release Irq={0:x2}", __arglist(irq));
#endif

                if (registered[irq] == this) {
                    registered[irq] = this.next;
                }
                else {
                    IoIrq! prev = (!)registered[irq];
                    while (prev.next != this) {
                        prev = prev.next;
                    }
                    prev.next = this.next;
                }

                if (registered[irq] == null) {
                    HalDevices.DisableIoInterrupt(irq);
                    return true;
                }
            }
            finally {
                ReleaseLock(enabled);
            }
            return true;
        }

        public bool WaitForInterrupt()
        {
            if (signal != null) {
                return signal.WaitOne();
            }
            return false;
        }

        public bool WaitForInterrupt(TimeSpan timeout)
        {
            if (signal != null) {
                return signal.WaitOne(timeout);
            }
            return false;
        }

        public void Pulse()
        {
            signal.Set();
        }

        public bool AckInterrupt()
        {
#if DEBUG_DISPATCH_IO
            DebugStub.WriteLine("++ AckInterrupt: Irq={0:x2}", __arglist(irq));
#endif
            HalDevices.EnableIoInterrupt(irq);
            return true;
        }

        public override string! ToString()
        {
            return String.Format("IRQ:{0,2:x2}", irq);
        }
    }
}