1// Copyright 2019 the V8 project authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5namespace string {
6const kBuiltinName: constexpr string = 'String.prototype.repeat';
7
8builtin StringRepeat(implicit context: Context)(
9    string: String, count: Smi): String {
10  dcheck(count >= 0);
11  dcheck(string != kEmptyString);
12
13  let result: String = kEmptyString;
14  let powerOfTwoRepeats: String = string;
15  let n: intptr = Convert<intptr>(count);
16
17  while (true) {
18    if ((n & 1) == 1) result = result + powerOfTwoRepeats;
19
20    n = n >> 1;
21    if (n == 0) break;
22
23    powerOfTwoRepeats = powerOfTwoRepeats + powerOfTwoRepeats;
24  }
25
26  return result;
27}
28
29// https://tc39.github.io/ecma262/#sec-string.prototype.repeat
30transitioning javascript builtin StringPrototypeRepeat(
31    js-implicit context: NativeContext, receiver: JSAny)(count: JSAny): String {
32  // 1. Let O be ? RequireObjectCoercible(this value).
33  // 2. Let S be ? ToString(O).
34  const s: String = ToThisString(receiver, kBuiltinName);
35
36  try {
37    // 3. Let n be ? ToInteger(count).
38    typeswitch (ToInteger_Inline(count)) {
39      case (n: Smi): {
40        // 4. If n < 0, throw a RangeError exception.
41        if (n < 0) goto InvalidCount;
42
43        // 6. If n is 0, return the empty String.
44        if (n == 0 || s.length_uint32 == 0) goto EmptyString;
45
46        if (n > kStringMaxLength) goto InvalidStringLength;
47
48        // 7. Return the String value that is made from n copies of S appended
49        // together.
50        return StringRepeat(s, n);
51      }
52      case (heapNum: HeapNumber): deferred {
53        dcheck(IsNumberNormalized(heapNum));
54        const n = LoadHeapNumberValue(heapNum);
55
56        // 4. If n < 0, throw a RangeError exception.
57        // 5. If n is +∞, throw a RangeError exception.
58        if (n == V8_INFINITY || n < 0) goto InvalidCount;
59
60        // 6. If n is 0, return the empty String.
61        if (s.length_uint32 == 0) goto EmptyString;
62
63        goto InvalidStringLength;
64      }
65    }
66  } label EmptyString {
67    return kEmptyString;
68  } label InvalidCount deferred {
69    ThrowRangeError(MessageTemplate::kInvalidCountValue, count);
70  } label InvalidStringLength deferred {
71    ThrowInvalidStringLength(context);
72  }
73}
74}
75