Implement %TypedArray%.prototype.slice

src/harmony-typedarray.js

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 (function(global, utils) {
 
 "use strict";
 
 %CheckIsBootstrapping();
 
@@ skipping 31 matching lines @@
 var InnerArrayForEach;
 var InnerArrayIndexOf;
 var InnerArrayJoin;
 var InnerArrayLastIndexOf;
 var InnerArrayMap;
 var InnerArrayReverse;
 var InnerArraySome;
 var InnerArraySort;
 var InnerArrayToLocaleString;
 var IsNaN;
+var MathMax;
+var MathMin;
 
 utils.Import(function(from) {
   ArrayFrom = from.ArrayFrom;
   ArrayToString = from.ArrayToString;
   InnerArrayCopyWithin = from.InnerArrayCopyWithin;
   InnerArrayEvery = from.InnerArrayEvery;
   InnerArrayFill = from.InnerArrayFill;
   InnerArrayFilter = from.InnerArrayFilter;
   InnerArrayFind = from.InnerArrayFind;
   InnerArrayFindIndex = from.InnerArrayFindIndex;
   InnerArrayForEach = from.InnerArrayForEach;
   InnerArrayIndexOf = from.InnerArrayIndexOf;
   InnerArrayJoin = from.InnerArrayJoin;
   InnerArrayLastIndexOf = from.InnerArrayLastIndexOf;
   InnerArrayMap = from.InnerArrayMap;
   InnerArrayReduce = from.InnerArrayReduce;
   InnerArrayReduceRight = from.InnerArrayReduceRight;
   InnerArrayReverse = from.InnerArrayReverse;
   InnerArraySome = from.InnerArraySome;
   InnerArraySort = from.InnerArraySort;
   InnerArrayToLocaleString = from.InnerArrayToLocaleString;
   IsNaN = from.IsNaN;
+  MathMax = from.MathMax;
+  MathMin = from.MathMin;
 });
 
 // -------------------------------------------------------------------
 
-function ConstructTypedArray(constructor, array) {
+function ConstructTypedArray(constructor, arg) {
   // TODO(littledan): This is an approximation of the spec, which requires
   // that only real TypedArray classes should be accepted (22.2.2.1.1)
   if (!%IsConstructor(constructor) || IS_UNDEFINED(constructor.prototype) ||
       !%HasOwnProperty(constructor.prototype, "BYTES_PER_ELEMENT")) {
     throw MakeTypeError(kNotTypedArray);
   }
 
   // TODO(littledan): The spec requires that, rather than directly calling
   // the constructor, a TypedArray is created with the proper proto and
   // underlying size and element size, and elements are put in one by one.
   // By contrast, this would allow subclasses to make a radically different
   // constructor with different semantics.
-  return new constructor(array);
+  return new constructor(arg);
 }
 
-function ConstructTypedArrayLike(typedArray, arrayContents) {
+function ConstructTypedArrayLike(typedArray, arg) {
   // TODO(littledan): The spec requires that we actuallly use
   // typedArray.constructor[Symbol.species] (bug v8:4093)
-  return ConstructTypedArray(typedArray.constructor, arrayContents);
+  // Also, it should default to the default constructor from
+  // table 49 if typedArray.constructor doesn't exist.
+  return ConstructTypedArray(typedArray.constructor, arg);
 }
 
 function TypedArrayCopyWithin(target, start, end) {
   if (!%IsTypedArray(this)) throw MakeTypeError(kNotTypedArray);
 
   var length = %_TypedArrayGetLength(this);
 
   // TODO(littledan): Replace with a memcpy for better performance
   return InnerArrayCopyWithin(target, start, end, this, length);
 }
@@ skipping 191 matching lines @@
 function TypedArrayReduceRight(callback, current) {
   if (!%IsTypedArray(this)) throw MakeTypeError(kNotTypedArray);
 
   var length = %_TypedArrayGetLength(this);
   return InnerArrayReduceRight(callback, current, this, length,
                                %_ArgumentsLength());
 }
 %FunctionSetLength(TypedArrayReduceRight, 1);
 
 
+function TypedArraySlice(start, end) {
+  if (!%IsTypedArray(this)) throw MakeTypeError(kNotTypedArray);
+  var len = %_TypedArrayGetLength(this);
+
+  var relativeStart = TO_INTEGER(start);
+
+  var k;
+  if (relativeStart < 0) {
+    k = MathMax(len + relativeStart, 0);
+  } else {
+    k = MathMin(relativeStart, len);
+  }
+
+  var relativeEnd;
+  if (IS_UNDEFINED(end)) {
+    relativeEnd = len;
+  } else {
+    relativeEnd = TO_INTEGER(end);
+  }
+
+  var final;
+  if (relativeEnd < 0) {
+    final = MathMax(len + relativeEnd, 0);
+  } else {
+    final = MathMin(relativeEnd, len);
+  }
+
+  var count = MathMax(final - k, 0);
+  var array = ConstructTypedArrayLike(this, count);
+  // The code below is the 'then' branch; the 'else' branch species
+  // a memcpy. Because V8 doesn't canonicalize NaN, the difference is
+  // unobservable.
+  var n = 0;
+  while (k < final) {
+    var kValue = this[k];
+    // TODO(littledan): The spec says to throw on an error in setting;
+    // does this throw?

[arv (Not doing code reviews), 2015/06/08 23:57:12]

If you make this function strict you should get the exception as needed.

+    array[n] = kValue;
+    k++;
+    n++;
+  }
+  return array;
+}
+
+
 // ES6 draft 08-24-14, section 22.2.2.2
 function TypedArrayOf() {
   var length = %_ArgumentsLength();
   var array = new this(length);
   for (var i = 0; i < length; i++) {
     array[i] = %_Arguments(i);
   }
   return array;
 }
 
@@ skipping 23 matching lines @@
     "find", TypedArrayFind,
     "findIndex", TypedArrayFindIndex,
     "indexOf", TypedArrayIndexOf,
     "join", TypedArrayJoin,
     "lastIndexOf", TypedArrayLastIndexOf,
     "forEach", TypedArrayForEach,
     "map", TypedArrayMap,
     "reduce", TypedArrayReduce,
     "reduceRight", TypedArrayReduceRight,
     "reverse", TypedArrayReverse,
+    "slice", TypedArraySlice,
     "some", TypedArraySome,
     "sort", TypedArraySort,
     "toString", TypedArrayToString,
     "toLocaleString", TypedArrayToLocaleString
   ]);
 endmacro
 
 TYPED_ARRAYS(EXTEND_TYPED_ARRAY)
 
 })