| // Copyright 2019 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. |
| |
| namespace string_substring { |
| |
| extern macro SubString(String, intptr, intptr): String; |
| |
| transitioning macro ToSmiBetweenZeroAnd(implicit context: Context)( |
| value: Object, limit: Smi): Smi { |
| const valueInt: Number = |
| ToInteger_Inline(context, value, kTruncateMinusZero); |
| typeswitch (valueInt) { |
| case (valueSmi: Smi): { |
| if (SmiAbove(valueSmi, limit)) { |
| return valueSmi < 0 ? 0 : limit; |
| } |
| return valueSmi; |
| } |
| // {value} is a heap number - in this case, it is definitely out of |
| // bounds. |
| case (hn: HeapNumber): { |
| const valueFloat: float64 = LoadHeapNumberValue(hn); |
| return valueFloat < 0. ? 0 : limit; |
| } |
| } |
| } |
| |
| // ES6 #sec-string.prototype.substring |
| transitioning javascript builtin StringPrototypeSubstring( |
| js-implicit context: Context, receiver: Object)(...arguments): String { |
| // Check that {receiver} is coercible to Object and convert it to a String. |
| const string: String = ToThisString(receiver, 'String.prototype.substring'); |
| const length = string.length_smi; |
| |
| // Conversion and bounds-checks for {start}. |
| let start: Smi = ToSmiBetweenZeroAnd(arguments[0], length); |
| |
| // Conversion and bounds-checks for {end}. |
| let end: Smi = arguments[1] == Undefined ? |
| length : |
| ToSmiBetweenZeroAnd(arguments[1], length); |
| if (end < start) { |
| const tmp: Smi = end; |
| end = start; |
| start = tmp; |
| } |
| return SubString(string, SmiUntag(start), SmiUntag(end)); |
| } |
| } |