string-repeat.tq 2.24 KB
Newer Older
1 2 3 4
// 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.

5
namespace string {
6
const kBuiltinName: constexpr string = 'String.prototype.repeat';
7

8 9 10 11
builtin StringRepeat(implicit context: Context)(
    string: String, count: Smi): String {
  assert(count >= 0);
  assert(string != kEmptyString);
12

13 14 15
  let result: String = kEmptyString;
  let powerOfTwoRepeats: String = string;
  let n: intptr = Convert<intptr>(count);
16

17 18
  while (true) {
    if ((n & 1) == 1) result = result + powerOfTwoRepeats;
19

20 21
    n = n >> 1;
    if (n == 0) break;
22

23
    powerOfTwoRepeats = powerOfTwoRepeats + powerOfTwoRepeats;
24
  }
25

26 27 28 29 30 31 32 33 34
  return result;
}

// https://tc39.github.io/ecma262/#sec-string.prototype.repeat
transitioning javascript builtin StringPrototypeRepeat(
    js-implicit context: NativeContext, receiver: JSAny)(count: JSAny): String {
  // 1. Let O be ? RequireObjectCoercible(this value).
  // 2. Let S be ? ToString(O).
  const s: String = ToThisString(receiver, kBuiltinName);
35

36 37 38 39 40 41
  try {
    // 3. Let n be ? ToInteger(count).
    typeswitch (ToInteger_Inline(count)) {
      case (n: Smi): {
        // 4. If n < 0, throw a RangeError exception.
        if (n < 0) goto InvalidCount;
42

43 44
        // 6. If n is 0, return the empty String.
        if (n == 0 || s.length_uint32 == 0) goto EmptyString;
45

46
        if (n > kStringMaxLength) goto InvalidStringLength;
47

48 49 50 51 52 53 54
        // 7. Return the String value that is made from n copies of S appended
        // together.
        return StringRepeat(s, n);
      }
      case (heapNum: HeapNumber): deferred {
        assert(IsNumberNormalized(heapNum));
        const n = LoadHeapNumberValue(heapNum);
55

56 57 58
        // 4. If n < 0, throw a RangeError exception.
        // 5. If n is +∞, throw a RangeError exception.
        if (n == V8_INFINITY || n < 0.0) goto InvalidCount;
59

60 61
        // 6. If n is 0, return the empty String.
        if (s.length_uint32 == 0) goto EmptyString;
62

63
        goto InvalidStringLength;
64 65
      }
    }
66 67 68 69 70 71
  } label EmptyString {
    return kEmptyString;
  } label InvalidCount deferred {
    ThrowRangeError(MessageTemplate::kInvalidCountValue, count);
  } label InvalidStringLength deferred {
    ThrowInvalidStringLength(context);
72
  }
73
}
74
}