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       1             : /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
       2             :  * vim: set ts=8 sts=4 et sw=4 tw=99:
       3             :  * This Source Code Form is subject to the terms of the Mozilla Public
       4             :  * License, v. 2.0. If a copy of the MPL was not distributed with this
       5             :  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
       6             : 
       7             : #ifndef js_SliceBudget_h
       8             : #define js_SliceBudget_h
       9             : 
      10             : #include <stdint.h>
      11             : 
      12             : namespace js {
      13             : 
      14             : struct JS_PUBLIC_API(TimeBudget)
      15             : {
      16             :     int64_t budget;
      17             : 
      18           3 :     explicit TimeBudget(int64_t milliseconds) { budget = milliseconds; }
      19             : };
      20             : 
      21             : struct JS_PUBLIC_API(WorkBudget)
      22             : {
      23             :     int64_t budget;
      24             : 
      25           3 :     explicit WorkBudget(int64_t work) { budget = work; }
      26             : };
      27             : 
      28             : /*
      29             :  * This class records how much work has been done in a given collection slice,
      30             :  * so that we can return before pausing for too long. Some slices are allowed
      31             :  * to run for unlimited time, and others are bounded. To reduce the number of
      32             :  * gettimeofday calls, we only check the time every 1000 operations.
      33             :  */
      34             : class JS_PUBLIC_API(SliceBudget)
      35             : {
      36             :     static const int64_t unlimitedDeadline = INT64_MAX;
      37             :     static const intptr_t unlimitedStartCounter = INTPTR_MAX;
      38             : 
      39             :     bool checkOverBudget();
      40             : 
      41             :     SliceBudget();
      42             : 
      43             :   public:
      44             :     // Memory of the originally requested budget. If isUnlimited, neither of
      45             :     // these are in use. If deadline==0, then workBudget is valid. Otherwise
      46             :     // timeBudget is valid.
      47             :     TimeBudget timeBudget;
      48             :     WorkBudget workBudget;
      49             : 
      50             :     int64_t deadline; /* in microseconds */
      51             :     intptr_t counter;
      52             : 
      53             :     static const intptr_t CounterReset = 1000;
      54             : 
      55             :     static const int64_t UnlimitedTimeBudget = -1;
      56             :     static const int64_t UnlimitedWorkBudget = -1;
      57             : 
      58             :     /* Use to create an unlimited budget. */
      59           0 :     static SliceBudget unlimited() { return SliceBudget(); }
      60             : 
      61             :     /* Instantiate as SliceBudget(TimeBudget(n)). */
      62             :     explicit SliceBudget(TimeBudget time);
      63             : 
      64             :     /* Instantiate as SliceBudget(WorkBudget(n)). */
      65             :     explicit SliceBudget(WorkBudget work);
      66             : 
      67           0 :     void makeUnlimited() {
      68           0 :         deadline = unlimitedDeadline;
      69           0 :         counter = unlimitedStartCounter;
      70           0 :     }
      71             : 
      72        3000 :     void step(intptr_t amt = 1) {
      73        3000 :         counter -= amt;
      74        3000 :     }
      75             : 
      76        5351 :     bool isOverBudget() {
      77        5351 :         if (counter > 0)
      78        5345 :             return false;
      79           6 :         return checkOverBudget();
      80             :     }
      81             : 
      82           0 :     bool isWorkBudget() const { return deadline == 0; }
      83           3 :     bool isTimeBudget() const { return deadline > 0 && !isUnlimited(); }
      84           6 :     bool isUnlimited() const { return deadline == unlimitedDeadline; }
      85             : 
      86             :     int describe(char* buffer, size_t maxlen) const;
      87             : };
      88             : 
      89             : } // namespace js
      90             : 
      91             : #endif /* js_SliceBudget_h */