The Tor Browser: js/src/builtin/Array.js@129ffea94266 (annotated)

js/src/builtin/Array.js@129ffea94266 (annotated)

js/src/builtin/Array.js

Sat, 03 Jan 2015 20:18:00 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Sat, 03 Jan 2015 20:18:00 +0100
branch: TOR_BUG_3246
changeset 7: 129ffea94266
permissions: -rw-r--r--

Conditionally enable double key logic according to:
private browsing mode or privacy.thirdparty.isolate preference and
implement in GetCookieStringCommon and FindCookie where it counts...
With some reservations of how to convince FindCookie users to test
condition and pass a nullptr when disabling double key logic.

 /* 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/. */
  /* ES5 15.4.4.14. */
 function ArrayIndexOf(searchElement/*, fromIndex*/) {
     /* Step 1. */
     var O = ToObject(this);
     /* Steps 2-3. */
     var len = TO_UINT32(O.length);
     /* Step 4. */
     if (len === 0)
         return -1;
     /* Step 5. */
     var n = arguments.length > 1 ? ToInteger(arguments[1]) : 0;
     /* Step 6. */
     if (n >= len)
         return -1;
     var k;
     /* Step 7. */
     if (n >= 0)
         k = n;
     /* Step 8. */
     else {
         /* Step a. */
         k = len + n;
         /* Step b. */
         if (k < 0)
             k = 0;
     }
     /* Step 9. */
     if (IsPackedArray(O)) {
         for (; k < len; k++) {
             if (O[k] === searchElement)
                 return k;
         }
     } else {
         for (; k < len; k++) {
             if (k in O && O[k] === searchElement)
                 return k;
         }
     }
     /* Step 10. */
     return -1;
 }
 function ArrayStaticIndexOf(list, searchElement/*, fromIndex*/) {
     if (arguments.length < 1)
         ThrowError(JSMSG_MISSING_FUN_ARG, 0, 'Array.indexOf');
     var fromIndex = arguments.length > 2 ? arguments[2] : 0;
     return callFunction(ArrayIndexOf, list, searchElement, fromIndex);
 }
 /* ES5 15.4.4.15. */
 function ArrayLastIndexOf(searchElement/*, fromIndex*/) {
     /* Step 1. */
     var O = ToObject(this);
     /* Steps 2-3. */
     var len = TO_UINT32(O.length);
     /* Step 4. */
     if (len === 0)
         return -1;
     /* Step 5. */
     var n = arguments.length > 1 ? ToInteger(arguments[1]) : len - 1;
     /* Steps 6-7. */
     var k;
     if (n > len - 1)
         k = len - 1;
     else if (n < 0)
         k = len + n;
     else
         k = n;
     /* Step 8. */
     if (IsPackedArray(O)) {
         for (; k >= 0; k--) {
             if (O[k] === searchElement)
                 return k;
         }
     } else {
         for (; k >= 0; k--) {
             if (k in O && O[k] === searchElement)
                 return k;
         }
     }
     /* Step 9. */
     return -1;
 }
 function ArrayStaticLastIndexOf(list, searchElement/*, fromIndex*/) {
     if (arguments.length < 1)
         ThrowError(JSMSG_MISSING_FUN_ARG, 0, 'Array.lastIndexOf');
     var fromIndex;
     if (arguments.length > 2) {
         fromIndex = arguments[2];
     } else {
         var O = ToObject(list);
         var len = TO_UINT32(O.length);
         fromIndex = len - 1;
     }
     return callFunction(ArrayLastIndexOf, list, searchElement, fromIndex);
 }
 /* ES5 15.4.4.16. */
 function ArrayEvery(callbackfn/*, thisArg*/) {
     /* Step 1. */
     var O = ToObject(this);
     /* Steps 2-3. */
     var len = TO_UINT32(O.length);
     /* Step 4. */
     if (arguments.length === 0)
         ThrowError(JSMSG_MISSING_FUN_ARG, 0, 'Array.prototype.every');
     if (!IsCallable(callbackfn))
         ThrowError(JSMSG_NOT_FUNCTION, DecompileArg(0, callbackfn));
     /* Step 5. */
     var T = arguments.length > 1 ? arguments[1] : void 0;
     /* Steps 6-7. */
     /* Steps a (implicit), and d. */
     for (var k = 0; k < len; k++) {
         /* Step b */
         if (k in O) {
             /* Step c. */
             if (!callFunction(callbackfn, T, O[k], k, O))
                 return false;
         }
     }
     /* Step 8. */
     return true;
 }
 function ArrayStaticEvery(list, callbackfn/*, thisArg*/) {
     if (arguments.length < 2)
         ThrowError(JSMSG_MISSING_FUN_ARG, 0, 'Array.every');
     if (!IsCallable(callbackfn))
         ThrowError(JSMSG_NOT_FUNCTION, DecompileArg(1, callbackfn));
     var T = arguments.length > 2 ? arguments[2] : void 0;
     return callFunction(ArrayEvery, list, callbackfn, T);
 }
 /* ES5 15.4.4.17. */
 function ArraySome(callbackfn/*, thisArg*/) {
     /* Step 1. */
     var O = ToObject(this);
     /* Steps 2-3. */
     var len = TO_UINT32(O.length);
     /* Step 4. */
     if (arguments.length === 0)
         ThrowError(JSMSG_MISSING_FUN_ARG, 0, 'Array.prototype.some');
     if (!IsCallable(callbackfn))
         ThrowError(JSMSG_NOT_FUNCTION, DecompileArg(0, callbackfn));
     /* Step 5. */
     var T = arguments.length > 1 ? arguments[1] : void 0;
     /* Steps 6-7. */
     /* Steps a (implicit), and d. */
     for (var k = 0; k < len; k++) {
         /* Step b */
         if (k in O) {
             /* Step c. */
             if (callFunction(callbackfn, T, O[k], k, O))
                 return true;
         }
     }
     /* Step 8. */
     return false;
 }
 function ArrayStaticSome(list, callbackfn/*, thisArg*/) {
     if (arguments.length < 2)
         ThrowError(JSMSG_MISSING_FUN_ARG, 0, 'Array.some');
     if (!IsCallable(callbackfn))
         ThrowError(JSMSG_NOT_FUNCTION, DecompileArg(1, callbackfn));
     var T = arguments.length > 2 ? arguments[2] : void 0;
     return callFunction(ArraySome, list, callbackfn, T);
 }
 /* ES5 15.4.4.18. */
 function ArrayForEach(callbackfn/*, thisArg*/) {
     /* Step 1. */
     var O = ToObject(this);
     /* Steps 2-3. */
     var len = TO_UINT32(O.length);
     /* Step 4. */
     if (arguments.length === 0)
         ThrowError(JSMSG_MISSING_FUN_ARG, 0, 'Array.prototype.forEach');
     if (!IsCallable(callbackfn))
         ThrowError(JSMSG_NOT_FUNCTION, DecompileArg(0, callbackfn));
     /* Step 5. */
     var T = arguments.length > 1 ? arguments[1] : void 0;
     /* Steps 6-7. */
     /* Steps a (implicit), and d. */
     for (var k = 0; k < len; k++) {
         /* Step b */
         if (k in O) {
             /* Step c. */
             callFunction(callbackfn, T, O[k], k, O);
         }
     }
     /* Step 8. */
     return void 0;
 }
 /* ES5 15.4.4.19. */
 function ArrayMap(callbackfn/*, thisArg*/) {
     /* Step 1. */
     var O = ToObject(this);
     /* Step 2-3. */
     var len = TO_UINT32(O.length);
     /* Step 4. */
     if (arguments.length === 0)
         ThrowError(JSMSG_MISSING_FUN_ARG, 0, 'Array.prototype.map');
     if (!IsCallable(callbackfn))
         ThrowError(JSMSG_NOT_FUNCTION, DecompileArg(0, callbackfn));
     /* Step 5. */
     var T = arguments.length > 1 ? arguments[1] : void 0;
     /* Step 6. */
     var A = NewDenseArray(len);
     /* Step 7-8. */
     /* Step a (implicit), and d. */
     for (var k = 0; k < len; k++) {
         /* Step b */
         if (k in O) {
             /* Step c.i-iii. */
             var mappedValue = callFunction(callbackfn, T, O[k], k, O);
             // UnsafePutElements doesn't invoke setters, so we can use it here.
             UnsafePutElements(A, k, mappedValue);
         }
     }
     /* Step 9. */
     return A;
 }
 function ArrayStaticMap(list, callbackfn/*, thisArg*/) {
     if (arguments.length < 2)
         ThrowError(JSMSG_MISSING_FUN_ARG, 0, 'Array.map');
     if (!IsCallable(callbackfn))
         ThrowError(JSMSG_NOT_FUNCTION, DecompileArg(1, callbackfn));
     var T = arguments.length > 2 ? arguments[2] : void 0;
     return callFunction(ArrayMap, list, callbackfn, T);
 }
 function ArrayStaticForEach(list, callbackfn/*, thisArg*/) {
     if (arguments.length < 2)
         ThrowError(JSMSG_MISSING_FUN_ARG, 0, 'Array.forEach');
     if (!IsCallable(callbackfn))
         ThrowError(JSMSG_NOT_FUNCTION, DecompileArg(1, callbackfn));
     var T = arguments.length > 2 ? arguments[2] : void 0;
     callFunction(ArrayForEach, list, callbackfn, T);
 }
 /* ES5 15.4.4.21. */
 function ArrayReduce(callbackfn/*, initialValue*/) {
     /* Step 1. */
     var O = ToObject(this);
     /* Steps 2-3. */
     var len = TO_UINT32(O.length);
     /* Step 4. */
     if (arguments.length === 0)
         ThrowError(JSMSG_MISSING_FUN_ARG, 0, 'Array.prototype.reduce');
     if (!IsCallable(callbackfn))
         ThrowError(JSMSG_NOT_FUNCTION, DecompileArg(0, callbackfn));
     /* Step 6. */
     var k = 0;
     /* Steps 5, 7-8. */
     var accumulator;
     if (arguments.length > 1) {
         accumulator = arguments[1];
     } else {
         /* Step 5. */
         if (len === 0)
             ThrowError(JSMSG_EMPTY_ARRAY_REDUCE);
         if (IsPackedArray(O)) {
             accumulator = O[k++];
         } else {
             var kPresent = false;
             for (; k < len; k++) {
                 if (k in O) {
                     accumulator = O[k];
                     kPresent = true;
                     k++;
                     break;
                 }
             }
             if (!kPresent)
               ThrowError(JSMSG_EMPTY_ARRAY_REDUCE);
         }
     }
     /* Step 9. */
     /* Steps a (implicit), and d. */
     for (; k < len; k++) {
         /* Step b */
         if (k in O) {
             /* Step c. */
             accumulator = callbackfn(accumulator, O[k], k, O);
         }
     }
     /* Step 10. */
     return accumulator;
 }
 function ArrayStaticReduce(list, callbackfn) {
     if (arguments.length < 2)
         ThrowError(JSMSG_MISSING_FUN_ARG, 0, 'Array.reduce');
     if (!IsCallable(callbackfn))
         ThrowError(JSMSG_NOT_FUNCTION, DecompileArg(1, callbackfn));
     if (arguments.length > 2)
         return callFunction(ArrayReduce, list, callbackfn, arguments[2]);
     else
         return callFunction(ArrayReduce, list, callbackfn);
 }
 /* ES5 15.4.4.22. */
 function ArrayReduceRight(callbackfn/*, initialValue*/) {
     /* Step 1. */
     var O = ToObject(this);
     /* Steps 2-3. */
     var len = TO_UINT32(O.length);
     /* Step 4. */
     if (arguments.length === 0)
         ThrowError(JSMSG_MISSING_FUN_ARG, 0, 'Array.prototype.reduce');
     if (!IsCallable(callbackfn))
         ThrowError(JSMSG_NOT_FUNCTION, DecompileArg(0, callbackfn));
     /* Step 6. */
     var k = len - 1;
     /* Steps 5, 7-8. */
     var accumulator;
     if (arguments.length > 1) {
         accumulator = arguments[1];
     } else {
         /* Step 5. */
         if (len === 0)
             ThrowError(JSMSG_EMPTY_ARRAY_REDUCE);
         if (IsPackedArray(O)) {
             accumulator = O[k--];
         } else {
             var kPresent = false;
             for (; k >= 0; k--) {
                 if (k in O) {
                     accumulator = O[k];
                     kPresent = true;
                     k--;
                     break;
                 }
             }
             if (!kPresent)
                 ThrowError(JSMSG_EMPTY_ARRAY_REDUCE);
         }
     }
     /* Step 9. */
     /* Steps a (implicit), and d. */
     for (; k >= 0; k--) {
         /* Step b */
         if (k in O) {
             /* Step c. */
             accumulator = callbackfn(accumulator, O[k], k, O);
         }
     }
     /* Step 10. */
     return accumulator;
 }
 function ArrayStaticReduceRight(list, callbackfn) {
     if (arguments.length < 2)
         ThrowError(JSMSG_MISSING_FUN_ARG, 0, 'Array.reduceRight');
     if (!IsCallable(callbackfn))
         ThrowError(JSMSG_NOT_FUNCTION, DecompileArg(1, callbackfn));
     if (arguments.length > 2)
         return callFunction(ArrayReduceRight, list, callbackfn, arguments[2]);
     else
         return callFunction(ArrayReduceRight, list, callbackfn);
 }
 /* ES6 draft 2013-05-14 15.4.3.23. */
 function ArrayFind(predicate/*, thisArg*/) {
     /* Steps 1-2. */
     var O = ToObject(this);
     /* Steps 3-5. */
     var len = ToInteger(O.length);
     /* Step 6. */
     if (arguments.length === 0)
         ThrowError(JSMSG_MISSING_FUN_ARG, 0, 'Array.prototype.find');
     if (!IsCallable(predicate))
         ThrowError(JSMSG_NOT_FUNCTION, DecompileArg(0, predicate));
     /* Step 7. */
     var T = arguments.length > 1 ? arguments[1] : undefined;
     /* Steps 8-9. */
     /* Steps a (implicit), and e. */
     /* Note: this will hang in some corner-case situations, because of IEEE-754 numbers'
      * imprecision for large values. Example:
      * var obj = { 18014398509481984: true, length: 18014398509481988 };
      * Array.prototype.find.call(obj, () => true);
      */
     for (var k = 0; k < len; k++) {
         /* Steps b and c (implicit) */
         if (k in O) {
             /* Step d. */
             var kValue = O[k];
             if (callFunction(predicate, T, kValue, k, O))
                 return kValue;
         }
     }
     /* Step 10. */
     return undefined;
 }
 /* ES6 draft 2013-05-14 15.4.3.23. */
 function ArrayFindIndex(predicate/*, thisArg*/) {
     /* Steps 1-2. */
     var O = ToObject(this);
     /* Steps 3-5. */
     var len = ToInteger(O.length);
     /* Step 6. */
     if (arguments.length === 0)
         ThrowError(JSMSG_MISSING_FUN_ARG, 0, 'Array.prototype.find');
     if (!IsCallable(predicate))
         ThrowError(JSMSG_NOT_FUNCTION, DecompileArg(0, predicate));
     /* Step 7. */
     var T = arguments.length > 1 ? arguments[1] : undefined;
     /* Steps 8-9. */
     /* Steps a (implicit), and e. */
     /* Note: this will hang in some corner-case situations, because of IEEE-754 numbers'
      * imprecision for large values. Example:
      * var obj = { 18014398509481984: true, length: 18014398509481988 };
      * Array.prototype.find.call(obj, () => true);
      */
     for (var k = 0; k < len; k++) {
         /* Steps b and c (implicit) */
         if (k in O) {
             /* Step d. */
             if (callFunction(predicate, T, O[k], k, O))
                 return k;
         }
     }
     /* Step 10. */
     return -1;
 }
 // ES6 draft 2014-04-05 22.1.3.6
 function ArrayFill(value, start = 0, end = undefined) {
     // Steps 1-2.
     var O = ToObject(this);
     // Steps 3-5.
     // FIXME: Array operations should use ToLength (bug 924058).
     var len = ToInteger(O.length);
     // Steps 6-7.
     var relativeStart = ToInteger(start);
     // Step 8.
     var k = relativeStart < 0
             ? std_Math_max(len + relativeStart, 0)
             : std_Math_min(relativeStart, len);
     // Steps 9-10.
     var relativeEnd = end === undefined ? len : ToInteger(end);
     // Step 11.
     var final = relativeEnd < 0
                 ? std_Math_max(len + relativeEnd, 0)
                 : std_Math_min(relativeEnd, len);
     // Step 12.
     for (; k < final; k++) {
         O[k] = value;
     }
     // Step 13.
     return O;
 }
 #define ARRAY_ITERATOR_SLOT_ITERATED_OBJECT 0
 #define ARRAY_ITERATOR_SLOT_NEXT_INDEX 1
 #define ARRAY_ITERATOR_SLOT_ITEM_KIND 2
 #define ITEM_KIND_VALUE 0
 #define ITEM_KIND_KEY_AND_VALUE 1
 #define ITEM_KIND_KEY 2
 // ES6 draft specification, section 22.1.5.1, version 2013-09-05.
 function CreateArrayIteratorAt(obj, kind, n) {
     var iteratedObject = ToObject(obj);
     var iterator = NewArrayIterator();
     UnsafeSetReservedSlot(iterator, ARRAY_ITERATOR_SLOT_ITERATED_OBJECT, iteratedObject);
     UnsafeSetReservedSlot(iterator, ARRAY_ITERATOR_SLOT_NEXT_INDEX, n);
     UnsafeSetReservedSlot(iterator, ARRAY_ITERATOR_SLOT_ITEM_KIND, kind);
     return iterator;
 }
 function CreateArrayIterator(obj, kind) {
     return CreateArrayIteratorAt(obj, kind, 0);
 }
 function ArrayIteratorIdentity() {
     return this;
 }
 function ArrayIteratorNext() {
     // FIXME: ArrayIterator prototype should not pass this test.  Bug 924059.
     if (!IsObject(this) || !IsArrayIterator(this))
         ThrowError(JSMSG_INCOMPATIBLE_METHOD, "ArrayIterator", "next", ToString(this));
     var a = UnsafeGetReservedSlot(this, ARRAY_ITERATOR_SLOT_ITERATED_OBJECT);
     var index = UnsafeGetReservedSlot(this, ARRAY_ITERATOR_SLOT_NEXT_INDEX);
     var itemKind = UnsafeGetReservedSlot(this, ARRAY_ITERATOR_SLOT_ITEM_KIND);
     // FIXME: This should be ToLength, which clamps at 2**53.  Bug 924058.
     if (index >= TO_UINT32(a.length)) {
         // When the above is changed to ToLength, use +1/0 here instead
         // of MAX_UINT32.
         UnsafeSetReservedSlot(this, ARRAY_ITERATOR_SLOT_NEXT_INDEX, 0xffffffff);
         return { value: undefined, done: true };
     }
     UnsafeSetReservedSlot(this, ARRAY_ITERATOR_SLOT_NEXT_INDEX, index + 1);
     if (itemKind === ITEM_KIND_VALUE)
         return { value: a[index], done: false };
     if (itemKind === ITEM_KIND_KEY_AND_VALUE) {
         var pair = NewDenseArray(2);
         pair[0] = index;
         pair[1] = a[index];
         return { value: pair, done : false };
     }
     assert(itemKind === ITEM_KIND_KEY, itemKind);
     return { value: index, done: false };
 }
 function ArrayValuesAt(n) {
     return CreateArrayIteratorAt(this, ITEM_KIND_VALUE, n);
 }
 function ArrayValues() {
     return CreateArrayIterator(this, ITEM_KIND_VALUE);
 }
 function ArrayEntries() {
     return CreateArrayIterator(this, ITEM_KIND_KEY_AND_VALUE);
 }
 function ArrayKeys() {
     return CreateArrayIterator(this, ITEM_KIND_KEY);
 }
 #ifdef ENABLE_PARALLEL_JS
 /*
  * Strawman spec:
  *   http://wiki.ecmascript.org/doku.php?id=strawman:data_parallelism
  */
 /**
  * Creates a new array by applying |func(e, i, self)| for each element |e|
  * with index |i|.
  */
 function ArrayMapPar(func, mode) {
   if (!IsCallable(func))
     ThrowError(JSMSG_NOT_FUNCTION, DecompileArg(0, func));
   var self = ToObject(this);
   var length = self.length;
   var buffer = NewDenseArray(length);
   parallel: for (;;) {
     // Avoid parallel compilation if we are already nested in another
     // parallel section or the user told us not to parallelize. The
     // use of a for (;;) loop is working around some ion limitations:
     //
     // - Breaking out of named blocks does not currently work (bug 684384);
     // - Unreachable Code Elim. can't properly handle if (a && b) (bug 669796)
     if (ShouldForceSequential())
       break parallel;
     if (!TRY_PARALLEL(mode))
       break parallel;
     var slicesInfo = ComputeSlicesInfo(length);
     ForkJoin(mapThread, 0, slicesInfo.count, ForkJoinMode(mode));
     return buffer;
   }
   // Sequential fallback:
   ASSERT_SEQUENTIAL_IS_OK(mode);
   for (var i = 0; i < length; i++)
     UnsafePutElements(buffer, i, func(self[i], i, self));
   return buffer;
   function mapThread(workerId, sliceStart, sliceEnd) {
     var sliceShift = slicesInfo.shift;
     var sliceId;
     while (GET_SLICE(sliceStart, sliceEnd, sliceId)) {
       var indexStart = SLICE_START_INDEX(sliceShift, sliceId);
       var indexEnd = SLICE_END_INDEX(sliceShift, indexStart, length);
       for (var i = indexStart; i < indexEnd; i++)
         UnsafePutElements(buffer, i, func(self[i], i, self));
     }
     return sliceId;
   }
   return undefined;
 }
 /**
  * Reduces the elements in an array in parallel. Order is not fixed and |func|
  * is assumed to be associative.
  */
 function ArrayReducePar(func, mode) {
   if (!IsCallable(func))
     ThrowError(JSMSG_NOT_FUNCTION, DecompileArg(0, func));
   var self = ToObject(this);
   var length = self.length;
   if (length === 0)
     ThrowError(JSMSG_EMPTY_ARRAY_REDUCE);
   parallel: for (;;) { // see ArrayMapPar() to explain why for(;;) etc
     if (ShouldForceSequential())
       break parallel;
     if (!TRY_PARALLEL(mode))
       break parallel;
     var slicesInfo = ComputeSlicesInfo(length);
     var numSlices = slicesInfo.count;
     var subreductions = NewDenseArray(numSlices);
     ForkJoin(reduceThread, 0, numSlices, ForkJoinMode(mode));
     var accumulator = subreductions[0];
     for (var i = 1; i < numSlices; i++)
       accumulator = func(accumulator, subreductions[i]);
     return accumulator;
   }
   // Sequential fallback:
   ASSERT_SEQUENTIAL_IS_OK(mode);
   var accumulator = self[0];
   for (var i = 1; i < length; i++)
     accumulator = func(accumulator, self[i]);
   return accumulator;
   function reduceThread(workerId, sliceStart, sliceEnd) {
     var sliceShift = slicesInfo.shift;
     var sliceId;
     while (GET_SLICE(sliceStart, sliceEnd, sliceId)) {
       var indexStart = SLICE_START_INDEX(sliceShift, sliceId);
       var indexEnd = SLICE_END_INDEX(sliceShift, indexStart, length);
       var accumulator = self[indexStart];
       for (var i = indexStart + 1; i < indexEnd; i++)
         accumulator = func(accumulator, self[i]);
       UnsafePutElements(subreductions, sliceId, accumulator);
     }
     return sliceId;
   }
   return undefined;
 }
 /**
  * Returns an array [s_0, ..., s_N] where |s_i| is equal to the reduction (as
  * per |reduce()|) of elements |0..i|. This is the generalization of partial
  * sum.
  */
 function ArrayScanPar(func, mode) {
   if (!IsCallable(func))
     ThrowError(JSMSG_NOT_FUNCTION, DecompileArg(0, func));
   var self = ToObject(this);
   var length = self.length;
   if (length === 0)
     ThrowError(JSMSG_EMPTY_ARRAY_REDUCE);
   var buffer = NewDenseArray(length);
   parallel: for (;;) { // see ArrayMapPar() to explain why for(;;) etc
     if (ShouldForceSequential())
       break parallel;
     if (!TRY_PARALLEL(mode))
       break parallel;
     var slicesInfo = ComputeSlicesInfo(length);
     var numSlices = slicesInfo.count;
     // Scan slices individually (see comment on phase1()).
     ForkJoin(phase1, 0, numSlices, ForkJoinMode(mode));
     // Compute intermediates array (see comment on phase2()).
     var intermediates = [];
     var accumulator = buffer[finalElement(0)];
     ARRAY_PUSH(intermediates, accumulator);
     for (var i = 1; i < numSlices - 1; i++) {
       accumulator = func(accumulator, buffer[finalElement(i)]);
       ARRAY_PUSH(intermediates, accumulator);
     }
     // Complete each slice using intermediates array (see comment on phase2()).
     //
     // We start from slice 1 instead of 0 since there is no work to be done
     // for slice 0.
     if (numSlices > 1)
       ForkJoin(phase2, 1, numSlices, ForkJoinMode(mode));
     return buffer;
   }
   // Sequential fallback:
   ASSERT_SEQUENTIAL_IS_OK(mode);
   scan(self[0], 0, length);
   return buffer;
   function scan(accumulator, start, end) {
     UnsafePutElements(buffer, start, accumulator);
     for (var i = start + 1; i < end; i++) {
       accumulator = func(accumulator, self[i]);
       UnsafePutElements(buffer, i, accumulator);
     }
     return accumulator;
   }
   /**
    * In phase 1, we divide the source array into |numSlices| slices and
    * compute scan on each slice sequentially as if it were the entire
    * array. This function is responsible for computing one of those
    * slices.
    *
    * So, if we have an array [A,B,C,D,E,F,G,H,I], |numSlices === 3|,
    * and our function |func| is sum, then we would wind up computing a
    * result array like:
    *
    *     [A, A+B, A+B+C, D, D+E, D+E+F, G, G+H, G+H+I]
    *      ^~~~~~~~~~~~^  ^~~~~~~~~~~~^  ^~~~~~~~~~~~~^
    *      Slice 0        Slice 1        Slice 2
    *
    * Read on in phase2 to see what we do next!
    */
   function phase1(workerId, sliceStart, sliceEnd) {
     var sliceShift = slicesInfo.shift;
     var sliceId;
     while (GET_SLICE(sliceStart, sliceEnd, sliceId)) {
       var indexStart = SLICE_START_INDEX(sliceShift, sliceId);
       var indexEnd = SLICE_END_INDEX(sliceShift, indexStart, length);
       scan(self[indexStart], indexStart, indexEnd);
     }
     return sliceId;
   }
   /**
    * Computes the index of the final element computed by the slice |sliceId|.
    */
   function finalElement(sliceId) {
     var sliceShift = slicesInfo.shift;
     return SLICE_END_INDEX(sliceShift, SLICE_START_INDEX(sliceShift, sliceId), length) - 1;
   }
   /**
    * After computing the phase1 results, we compute an
    * |intermediates| array. |intermediates[i]| contains the result
    * of reducing the final value from each preceding slice j<i with
    * the final value of slice i. So, to continue our previous
    * example, the intermediates array would contain:
    *
    *   [A+B+C, (A+B+C)+(D+E+F), ((A+B+C)+(D+E+F))+(G+H+I)]
    *
    * Here I have used parenthesization to make clear the order of
    * evaluation in each case.
    *
    *   An aside: currently the intermediates array is computed
    *   sequentially. In principle, we could compute it in parallel,
    *   at the cost of doing duplicate work. This did not seem
    *   particularly advantageous to me, particularly as the number
    *   of slices is typically quite small (one per core), so I opted
    *   to just compute it sequentially.
    *
    * Phase 2 combines the results of phase1 with the intermediates
    * array to produce the final scan results. The idea is to
    * reiterate over each element S[i] in the slice |sliceId|, which
    * currently contains the result of reducing with S[0]...S[i]
    * (where S0 is the first thing in the slice), and combine that
    * with |intermediate[sliceId-1]|, which represents the result of
    * reducing everything in the input array prior to the slice.
    *
    * To continue with our example, in phase 1 we computed slice 1 to
    * be [D, D+E, D+E+F]. We will combine those results with
    * |intermediates[1-1]|, which is |A+B+C|, so that the final
    * result is [(A+B+C)+D, (A+B+C)+(D+E), (A+B+C)+(D+E+F)]. Again I
    * am using parentheses to clarify how these results were reduced.
    */
   function phase2(workerId, sliceStart, sliceEnd) {
     var sliceShift = slicesInfo.shift;
     var sliceId;
     while (GET_SLICE(sliceStart, sliceEnd, sliceId)) {
       var indexPos = SLICE_START_INDEX(sliceShift, sliceId);
       var indexEnd = SLICE_END_INDEX(sliceShift, indexPos, length);
       var intermediate = intermediates[sliceId - 1];
       for (; indexPos < indexEnd; indexPos++)
         UnsafePutElements(buffer, indexPos, func(intermediate, buffer[indexPos]));
     }
     return sliceId;
   }
   return undefined;
 }
 /**
  * |scatter()| redistributes the elements in the array into a new array.
  *
  * - targets: The index targets[i] indicates where the ith element
  *   should appear in the result.
  *
  * - defaultValue: what value to use for indices in the output array that
  *   are never targeted.
  *
  * - conflictFunc: The conflict function. Used to resolve what
  *   happens if two indices i and j in the source array are targeted
  *   as the same destination (i.e., targets[i] === targets[j]), then
  *   the final result is determined by applying func(targets[i],
  *   targets[j]). If no conflict function is provided, it is an error
  *   if targets[i] === targets[j].
  *
  * - length: length of the output array (if not specified, uses the
  *   length of the input).
  *
  * - mode: internal debugging specification.
  */
 function ArrayScatterPar(targets, defaultValue, conflictFunc, length, mode) {
   if (conflictFunc && !IsCallable(conflictFunc))
     ThrowError(JSMSG_NOT_FUNCTION, DecompileArg(2, conflictFunc));
   var self = ToObject(this);
   if (length === undefined)
     length = self.length;
   var targetsLength = std_Math_min(targets.length, self.length);
   if (!IS_UINT32(targetsLength) || !IS_UINT32(length))
     ThrowError(JSMSG_BAD_ARRAY_LENGTH);
   // FIXME: Bug 965609: Find a better parallel startegy for scatter.
   // Sequential fallback:
   ASSERT_SEQUENTIAL_IS_OK(mode);
   return seq();
   function seq() {
     var buffer = NewDenseArray(length);
     var conflicts = NewDenseArray(length);
     for (var i = 0; i < length; i++) {
       UnsafePutElements(buffer, i, defaultValue);
       UnsafePutElements(conflicts, i, false);
     }
     for (var i = 0; i < targetsLength; i++) {
       var x = self[i];
       var t = checkTarget(i, targets[i]);
       if (conflicts[t])
         x = collide(x, buffer[t]);
       UnsafePutElements(buffer, t, x, conflicts, t, true);
     }
     return buffer;
   }
   function collide(elem1, elem2) {
     if (conflictFunc === undefined)
       ThrowError(JSMSG_PAR_ARRAY_SCATTER_CONFLICT);
     return conflictFunc(elem1, elem2);
   }
   function checkTarget(i, t) {
     if (TO_INT32(t) !== t)
       ThrowError(JSMSG_PAR_ARRAY_SCATTER_BAD_TARGET, i);
     if (t < 0 || t >= length)
       ThrowError(JSMSG_PAR_ARRAY_SCATTER_BOUNDS);
     // It's not enough to return t, as -0 | 0 === -0.
     return TO_INT32(t);
   }
   return undefined;
 }
 /**
  * The filter operation applied in parallel.
  */
 function ArrayFilterPar(func, mode) {
   if (!IsCallable(func))
     ThrowError(JSMSG_NOT_FUNCTION, DecompileArg(0, func));
   var self = ToObject(this);
   var length = self.length;
   parallel: for (;;) { // see ArrayMapPar() to explain why for(;;) etc
     if (ShouldForceSequential())
       break parallel;
     if (!TRY_PARALLEL(mode))
       break parallel;
     var slicesInfo = ComputeSlicesInfo(length);
     // Step 1. Compute which items from each slice of the result buffer should
     // be preserved. When we're done, we have a uint8 array |survivors|
     // containing 0 or 1 for each source element, indicating which members of
     // the chunk survived. We also keep an array |counts| containing the total
     // number of items that are being preserved from within one slice.
     var numSlices = slicesInfo.count;
     var counts = NewDenseArray(numSlices);
     for (var i = 0; i < numSlices; i++)
       UnsafePutElements(counts, i, 0);
     var survivors = new Uint8Array(length);
     ForkJoin(findSurvivorsThread, 0, numSlices, ForkJoinMode(mode));
     // Step 2. Compress the slices into one contiguous set.
     var count = 0;
     for (var i = 0; i < numSlices; i++)
       count += counts[i];
     var buffer = NewDenseArray(count);
     if (count > 0)
       ForkJoin(copySurvivorsThread, 0, numSlices, ForkJoinMode(mode));
     return buffer;
   }
   // Sequential fallback:
   ASSERT_SEQUENTIAL_IS_OK(mode);
   var buffer = [];
   for (var i = 0; i < length; i++) {
     var elem = self[i];
     if (func(elem, i, self))
       ARRAY_PUSH(buffer, elem);
   }
   return buffer;
   /**
    * As described above, our goal is to determine which items we will preserve
    * from a given slice, storing "to-keep" bits into 32-bit chunks.
    */
   function findSurvivorsThread(workerId, sliceStart, sliceEnd) {
     var sliceShift = slicesInfo.shift;
     var sliceId;
     while (GET_SLICE(sliceStart, sliceEnd, sliceId)) {
       var count = 0;
       var indexStart = SLICE_START_INDEX(sliceShift, sliceId);
       var indexEnd = SLICE_END_INDEX(sliceShift, indexStart, length);
       for (var indexPos = indexStart; indexPos < indexEnd; indexPos++) {
         var keep = !!func(self[indexPos], indexPos, self);
         UnsafePutElements(survivors, indexPos, keep);
         count += keep;
       }
       UnsafePutElements(counts, sliceId, count);
     }
     return sliceId;
   }
   /**
    * Copies the survivors from this slice into the correct position. Note
    * that this is an idempotent operation that does not invoke user
    * code. Therefore, we don't expect bailouts and make an effort to proceed
    * chunk by chunk or avoid duplicating work.
    */
   function copySurvivorsThread(workerId, sliceStart, sliceEnd) {
     var sliceShift = slicesInfo.shift;
     var sliceId;
     while (GET_SLICE(sliceStart, sliceEnd, sliceId)) {
       // Total up the items preserved by previous slices.
       var total = 0;
       for (var i = 0; i < sliceId + 1; i++)
         total += counts[i];
       // Are we done?
       var count = total - counts[sliceId];
       if (count === total)
         continue;
       var indexStart = SLICE_START_INDEX(sliceShift, sliceId);
       var indexEnd = SLICE_END_INDEX(sliceShift, indexStart, length);
       for (var indexPos = indexStart; indexPos < indexEnd; indexPos++) {
         if (survivors[indexPos]) {
           UnsafePutElements(buffer, count++, self[indexPos]);
           if (count == total)
             break;
         }
       }
     }
     return sliceId;
   }
   return undefined;
 }
 /**
  * "Comprehension form": This is the function invoked for
  * |Array.{build,buildPar}(len, fn)| It creates a new array with length |len|
  * where index |i| is equal to |fn(i)|.
  *
  * The final |mode| argument is an internal argument used only during our
  * unit-testing.
  */
 function ArrayStaticBuild(length, func) {
   if (!IS_UINT32(length))
     ThrowError(JSMSG_BAD_ARRAY_LENGTH);
   if (!IsCallable(func))
     ThrowError(JSMSG_NOT_FUNCTION, DecompileArg(1, func));
   var buffer = NewDenseArray(length);
   for (var i = 0; i < length; i++)
     UnsafePutElements(buffer, i, func(i));
   return buffer;
 }
 function ArrayStaticBuildPar(length, func, mode) {
   if (!IS_UINT32(length))
     ThrowError(JSMSG_BAD_ARRAY_LENGTH);
   if (!IsCallable(func))
     ThrowError(JSMSG_NOT_FUNCTION, DecompileArg(1, func));
   var buffer = NewDenseArray(length);
   parallel: for (;;) {
     if (ShouldForceSequential())
       break parallel;
     if (!TRY_PARALLEL(mode))
       break parallel;
     var slicesInfo = ComputeSlicesInfo(length);
     ForkJoin(constructThread, 0, slicesInfo.count, ForkJoinMode(mode));
     return buffer;
   }
   // Sequential fallback:
   ASSERT_SEQUENTIAL_IS_OK(mode);
   for (var i = 0; i < length; i++)
     UnsafePutElements(buffer, i, func(i));
   return buffer;
   function constructThread(workerId, sliceStart, sliceEnd) {
     var sliceShift = slicesInfo.shift;
     var sliceId;
     while (GET_SLICE(sliceStart, sliceEnd, sliceId)) {
       var indexStart = SLICE_START_INDEX(sliceShift, sliceId);
       var indexEnd = SLICE_END_INDEX(sliceShift, indexStart, length);
       for (var i = indexStart; i < indexEnd; i++)
         UnsafePutElements(buffer, i, func(i));
     }
     return sliceId;
   }
   return undefined;
 }
 /*
  * Mark the main operations as clone-at-callsite for better precision.
  * This is slightly overkill, as all that we really need is to
  * specialize to the receiver and the elemental function, but in
  * practice this is likely not so different, since element functions
  * are often used in exactly one place.
  */
 SetScriptHints(ArrayMapPar,         { cloneAtCallsite: true });
 SetScriptHints(ArrayReducePar,      { cloneAtCallsite: true });
 SetScriptHints(ArrayScanPar,        { cloneAtCallsite: true });
 SetScriptHints(ArrayScatterPar,     { cloneAtCallsite: true });
 SetScriptHints(ArrayFilterPar,      { cloneAtCallsite: true });
 SetScriptHints(ArrayStaticBuildPar, { cloneAtCallsite: true });
 #endif /* ENABLE_PARALLEL_JS */