/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-

 * vim: set ts=8 sts=4 et sw=4 tw=99:

 * This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef js_SliceBudget_h

#define js_SliceBudget_h

#include "mozilla/TimeStamp.h"

#include <stdint.h>

#include "jstypes.h"

namespace js {

struct JS_PUBLIC_API(TimeBudget)

{

    int64_t budget;

    explicit TimeBudget(int64_t milliseconds) { budget = milliseconds; }

};

struct JS_PUBLIC_API(WorkBudget)

{

    int64_t budget;

    explicit WorkBudget(int64_t work) { budget = work; }

};

/*

 * This class records how much work has been done in a given collection slice,

 * so that we can return before pausing for too long. Some slices are allowed

 * to run for unlimited time, and others are bounded. To reduce the number of

 * gettimeofday calls, we only check the time every 1000 operations.

 */

class JS_PUBLIC_API(SliceBudget)

{

    static mozilla::TimeStamp unlimitedDeadline;

    static const intptr_t unlimitedStartCounter = INTPTR_MAX;

    bool checkOverBudget();

    SliceBudget();

  public:

    // Memory of the originally requested budget. If isUnlimited, neither of

    // these are in use. If deadline==0, then workBudget is valid. Otherwise

    // timeBudget is valid.

    TimeBudget timeBudget;

    WorkBudget workBudget;

    mozilla::TimeStamp deadline;

    intptr_t counter;

    static const intptr_t CounterReset = 1000;

    static const int64_t UnlimitedTimeBudget = -1;

    static const int64_t UnlimitedWorkBudget = -1;

    /* Use to create an unlimited budget. */

    static SliceBudget unlimited() { return SliceBudget(); }

    /* Instantiate as SliceBudget(TimeBudget(n)). */

    explicit SliceBudget(TimeBudget time);

    /* Instantiate as SliceBudget(WorkBudget(n)). */

    explicit SliceBudget(WorkBudget work);

    void makeUnlimited() {

        MOZ_ASSERT(unlimitedDeadline);

        deadline = unlimitedDeadline;

        counter = unlimitedStartCounter;

    }

    void step(intptr_t amt = 1) {

        counter -= amt;

    }

    bool isOverBudget() {

        if (counter > 0) {

            return false;

        }

        return checkOverBudget();

    }

    bool isWorkBudget() const { return deadline.IsNull(); }

    bool isTimeBudget() const { return !deadline.IsNull() && !isUnlimited(); }

    bool isUnlimited() const { return deadline == unlimitedDeadline; }

    int describe(char* buffer, size_t maxlen) const;

    static void Init();

};

} // namespace js

#endif /* js_SliceBudget_h */