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// 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: JSAny, 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: JSAny)(...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));
}
}
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