(wtf8, start, end)
| 54 | // Compute the string that corresponds to the valid WTF-8 bytes from |
| 55 | // start (inclusive) to end (exclusive). |
| 56 | function decodeWtf8(wtf8, start, end) { |
| 57 | let result = '' |
| 58 | while (start < end) { |
| 59 | let cp; |
| 60 | let b0 = wtf8[start]; |
| 61 | if ((b0 & 0xC0) == 0x80) { |
| 62 | // The precondition is that we have valid WTF-8 bytes and that |
| 63 | // start and end are codepoint boundaries. Here we make a weak |
| 64 | // assertion about that invariant, that we don't start decoding |
| 65 | // with a continuation byte. |
| 66 | throw new Error('invalid wtf8'); |
| 67 | } |
| 68 | if (b0 <= 0x7F) { |
| 69 | cp = b0; |
| 70 | start += 1; |
| 71 | } else if (b0 <= 0xDF) { |
| 72 | cp = (b0 & 0x1f) << 6; |
| 73 | cp |= (wtf8[start + 1] & 0x3f); |
| 74 | start += 2; |
| 75 | } else if (b0 <= 0xEF) { |
| 76 | cp = (b0 & 0x0f) << 12; |
| 77 | cp |= (wtf8[start + 1] & 0x3f) << 6; |
| 78 | cp |= (wtf8[start + 2] & 0x3f); |
| 79 | start += 3; |
| 80 | } else { |
| 81 | cp = (b0 & 0x07) << 18; |
| 82 | cp |= (wtf8[start + 1] & 0x3f) << 12; |
| 83 | cp |= (wtf8[start + 2] & 0x3f) << 6; |
| 84 | cp |= (wtf8[start + 3] & 0x3f); |
| 85 | start += 4; |
| 86 | } |
| 87 | result += String.fromCodePoint(cp); |
| 88 | } |
| 89 | assertEquals(start, end); |
| 90 | return result; |
| 91 | } |
| 92 | |
| 93 | // We iterate over every one of these strings and every substring of it, |
| 94 | // so to keep test execution times fast on slow platforms, keep both this |
no test coverage detected