v8/test/unittests/unicode-unittest.cc

// Copyright 2016 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.

#include <memory>
#include <string>
#include <vector>

#include "src/unicode-decoder.h"
#include "src/unicode-inl.h"
#include "src/vector.h"
#include "testing/gtest/include/gtest/gtest.h"

namespace v8 {
namespace internal {

namespace {

void DecodeNormally(const std::vector<byte>& bytes,
                    std::vector<unibrow::uchar>* output) {
  size_t cursor = 0;
  while (cursor < bytes.size()) {
    output->push_back(
        unibrow::Utf8::ValueOf(bytes.data() + cursor, bytes.size(), &cursor));
  }
}

void DecodeUtf16(const std::vector<uint8_t>& bytes,
                 std::vector<unibrow::uchar>* output) {
  auto utf8_data = Vector<const uint8_t>::cast(VectorOf(bytes));
  Utf8Decoder decoder(utf8_data);

  std::vector<uint16_t> utf16(decoder.utf16_length());
  decoder.Decode(&utf16[0], utf8_data);

  // Decode back into code points
  for (size_t i = 0; i < utf16.size(); i++) {
    uint16_t b = utf16[i];
    if (unibrow::Utf16::IsLeadSurrogate(b)) {
      output->push_back(unibrow::Utf16::CombineSurrogatePair(b, utf16[++i]));
    } else {
      output->push_back(b);
    }
  }
}

void DecodeIncrementally(const std::vector<byte>& bytes,
                         std::vector<unibrow::uchar>* output) {
  unibrow::Utf8::Utf8IncrementalBuffer buffer = 0;
  unibrow::Utf8::State state = unibrow::Utf8::State::kAccept;
  const byte* cursor = &bytes[0];
  const byte* end = &bytes[bytes.size()];
  while (cursor < end) {
    unibrow::uchar result =
        unibrow::Utf8::ValueOfIncremental(&cursor, &state, &buffer);
    if (result != unibrow::Utf8::kIncomplete) {
      output->push_back(result);
    }
  }
  unibrow::uchar result = unibrow::Utf8::ValueOfIncrementalFinish(&state);
  if (result != unibrow::Utf8::kBufferEmpty) {
    output->push_back(result);
  }
}

}  // namespace

TEST(UnicodeTest, Utf16BufferReuse) {
  // Not enough continuation bytes before string ends.
  typedef struct {
    std::vector<byte> bytes;
    std::vector<unibrow::uchar> unicode_expected;
  } TestCase;

  TestCase data[] = {
      {{0x00}, {0x0}},
      {{0xC2, 0x80}, {0x80}},
      {{0xE0, 0xA0, 0x80}, {0x800}},
      {{0xF0, 0x90, 0x80, 0x80}, {0x10000}},
      {{0xE0, 0xA0, 0x80}, {0x800}},
      {{0xC2, 0x80}, {0x80}},
      {{0x00}, {0x0}},
  };
  for (auto test : data) {
    // For figuring out which test fails:
    fprintf(stderr, "test: ");
    for (auto b : test.bytes) {
      fprintf(stderr, "%x ", b);
    }
    fprintf(stderr, "\n");

    std::vector<unibrow::uchar> output_utf16;
    DecodeUtf16(test.bytes, &output_utf16);

    CHECK_EQ(output_utf16.size(), test.unicode_expected.size());
    for (size_t i = 0; i < output_utf16.size(); ++i) {
      CHECK_EQ(output_utf16[i], test.unicode_expected[i]);
    }
  }
}

TEST(UnicodeTest, SurrogateOverrunsBuffer) {
  std::vector<unibrow::uchar> output_utf16;
  // Not enough continuation bytes before string ends.
  DecodeUtf16({0x00, 0xF0, 0x90, 0x80, 0x80, 0x00}, &output_utf16);
  CHECK_EQ(output_utf16[0], 0x00);
  CHECK_EQ(output_utf16[1], 0x10000);
  CHECK_EQ(output_utf16[0], 0x00);
}

TEST(UnicodeTest, IncrementalUTF8DecodingVsNonIncrementalUtf8Decoding) {
  // Unfortunately, V8 has two UTF-8 decoders. This test checks that they
  // produce the same result. This test was inspired by
  // https://www.cl.cam.ac.uk/~mgk25/ucs/examples/UTF-8-test.txt .
  typedef struct {
    std::vector<byte> bytes;
    std::vector<unibrow::uchar> unicode_expected;
  } TestCase;

  TestCase data[] = {
      // Correct UTF-8 text.
      {{0xCE, 0xBA, 0xE1, 0xBD, 0xB9, 0xCF, 0x83, 0xCE, 0xBC, 0xCE, 0xB5},
       {0x3BA, 0x1F79, 0x3C3, 0x3BC, 0x3B5}},

      // First possible sequence of a certain length:
      // 1 byte
      {{0x00}, {0x0}},
      // 2 bytes
      {{0xC2, 0x80}, {0x80}},
      // 3 bytes
      {{0xE0, 0xA0, 0x80}, {0x800}},
      // 4 bytes
      {{0xF0, 0x90, 0x80, 0x80}, {0x10000}},
      // 5 bytes (not supported)
      {{0xF8, 0x88, 0x80, 0x80, 0x80},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      // 6 bytes (not supported)
      {{0xFC, 0x84, 0x80, 0x80, 0x80, 0x80},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},

      // Last possible sequence of certain length:
      // 1 byte
      {{0x7F}, {0x7F}},
      // 2 bytes
      {{0xDF, 0xBF}, {0x7FF}},
      // 3 bytes
      {{0xEF, 0xBF, 0xBF}, {0xFFFF}},
      // 4 bytes (this sequence is not a valid code point)
      {{0xF7, 0xBF, 0xBF, 0xBF}, {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      // 5 bytes (not supported)
      {{0xFB, 0xBF, 0xBF, 0xBF, 0xBF},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      // 6 bytes (not supported)
      {{0xFD, 0xBF, 0xBF, 0xBF, 0xBF, 0xBF},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      // Other boundary conditions:
      {{0xED, 0x9F, 0xBF}, {0xD7FF}},
      {{0xEE, 0x80, 0x80}, {0xE000}},
      // U+fffd (invalid code point)
      {{0xEF, 0xBF, 0xBD}, {0xFFFD}},
      // U+10ffff (last valid code point)
      {{0xF4, 0x8F, 0xBF, 0xBF}, {0x10FFFF}},
      // First invalid (too large) code point
      {{0xF4, 0x90, 0x80, 0x80}, {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},

      // Malformed sequences:
      // Unexpected continuation bytes:
      // First continuation byte
      {{0x80}, {0xFFFD}},
      // Last continuation byte
      {{0xBF}, {0xFFFD}},
      // 2 continuation bytes
      {{0x80, 0xBF}, {0xFFFD, 0xFFFD}},
      // 3 continuation bytes
      {{0x80, 0xBF, 0x80}, {0xFFFD, 0xFFFD, 0xFFFD}},
      // 4 continuation bytes
      {{0x80, 0xBF, 0x80, 0xBF}, {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      // 5 continuation bytes
      {{0x80, 0xBF, 0x80, 0xBF, 0x80},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      // 6 continuation bytes
      {{0x80, 0xBF, 0x80, 0xBF, 0x80, 0xBF},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      // 7 continuation bytes
      {{0x80, 0xBF, 0x80, 0xBF, 0x80, 0xBF, 0xBF},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      // Sequence of all 64 possible continuation bytes
      {{0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89, 0x8A,
        0x8B, 0x8C, 0x8D, 0x8E, 0x8F, 0x90, 0x91, 0x92, 0x93, 0x94, 0x95,
        0x96, 0x97, 0x98, 0x99, 0x9A, 0x9B, 0x9C, 0x9D, 0x9E, 0x9F, 0xA0,
        0xA1, 0xA2, 0xA3, 0xA4, 0xA5, 0xA6, 0xA7, 0xA8, 0xA9, 0xAA, 0xAB,
        0xAC, 0xAD, 0xAE, 0xAF, 0xB0, 0xB1, 0xB2, 0xB3, 0xB4, 0xB5, 0xB6,
        0xB7, 0xB8, 0xB9, 0xBA, 0xBB, 0xBC, 0xBD, 0xBE, 0xBF},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD,
        0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD,
        0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD,
        0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD,
        0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD,
        0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD,
        0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD,
        0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      // Using each possible continuation byte in a two-byte sequence:
      {{0xD0, 0x80, 0xD0, 0x81, 0xD0, 0x82, 0xD0, 0x83, 0xD0, 0x84, 0xD0, 0x85,
        0xD0, 0x86, 0xD0, 0x87, 0xD0, 0x88, 0xD0, 0x89, 0xD0, 0x8A, 0xD0, 0x8B,
        0xD0, 0x8C, 0xD0, 0x8D, 0xD0, 0x8E, 0xD0, 0x8F, 0xD0, 0x90, 0xD0, 0x91,
        0xD0, 0x92, 0xD0, 0x93, 0xD0, 0x94, 0xD0, 0x95, 0xD0, 0x96, 0xD0, 0x97,
        0xD0, 0x98, 0xD0, 0x99, 0xD0, 0x9A, 0xD0, 0x9B, 0xD0, 0x9C, 0xD0, 0x9D,
        0xD0, 0x9E, 0xD0, 0x9F, 0xD0, 0xA0, 0xD0, 0xA1, 0xD0, 0xA2, 0xD0, 0xA3,
        0xD0, 0xA4, 0xD0, 0xA5, 0xD0, 0xA6, 0xD0, 0xA7, 0xD0, 0xA8, 0xD0, 0xA9,
        0xD0, 0xAA, 0xD0, 0xAB, 0xD0, 0xAC, 0xD0, 0xAD, 0xD0, 0xAE, 0xD0, 0xAF,
        0xD0, 0xB0, 0xD0, 0xB1, 0xD0, 0xB2, 0xD0, 0xB3, 0xD0, 0xB4, 0xD0, 0xB5,
        0xD0, 0xB6, 0xD0, 0xB7, 0xD0, 0xB8, 0xD0, 0xB9, 0xD0, 0xBA, 0xD0, 0xBB,
        0xD0, 0xBC, 0xD0, 0xBD, 0xD0, 0xBE, 0xD0, 0xBF},
       {0x400, 0x401, 0x402, 0x403, 0x404, 0x405, 0x406, 0x407, 0x408, 0x409,
        0x40A, 0x40B, 0x40C, 0x40D, 0x40E, 0x40F, 0x410, 0x411, 0x412, 0x413,
        0x414, 0x415, 0x416, 0x417, 0x418, 0x419, 0x41A, 0x41B, 0x41C, 0x41D,
        0x41E, 0x41F, 0x420, 0x421, 0x422, 0x423, 0x424, 0x425, 0x426, 0x427,
        0x428, 0x429, 0x42A, 0x42B, 0x42C, 0x42D, 0x42E, 0x42F, 0x430, 0x431,
        0x432, 0x433, 0x434, 0x435, 0x436, 0x437, 0x438, 0x439, 0x43A, 0x43B,
        0x43C, 0x43D, 0x43E, 0x43F}},

      // Lonely first bytes:
      // All 32 first bytes of 32-byte sequences, each followed by a space
      // (generates 32 invalid char + space sequences.
      {{0xC0, 0x20, 0xC1, 0x20, 0xC2, 0x20, 0xC3, 0x20, 0xC4, 0x20, 0xC5,
        0x20, 0xC6, 0x20, 0xC7, 0x20, 0xC8, 0x20, 0xC9, 0x20, 0xCA, 0x20,
        0xCB, 0x20, 0xCC, 0x20, 0xCD, 0x20, 0xCE, 0x20, 0xCF, 0x20, 0xD0,
        0x20, 0xD1, 0x20, 0xD2, 0x20, 0xD3, 0x20, 0xD4, 0x20, 0xD5, 0x20,
        0xD6, 0x20, 0xD7, 0x20, 0xD8, 0x20, 0xD9, 0x20, 0xDA, 0x20, 0xDB,
        0x20, 0xDC, 0x20, 0xDD, 0x20, 0xDE, 0x20, 0xDF, 0x20},
       {0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20,
        0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20,
        0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20,
        0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20,
        0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20,
        0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20,
        0xFFFD, 0x20, 0xFFFD, 0x20}},
      // All 16 first bytes of 3-byte sequences, each followed by a space
      // (generates 16 invalid char + space sequences):
      {{0xE0, 0x20, 0xE1, 0x20, 0xE2, 0x20, 0xE3, 0x20, 0xE4, 0x20, 0xE5,
        0x20, 0xE6, 0x20, 0xE7, 0x20, 0xE8, 0x20, 0xE9, 0x20, 0xEA, 0x20,
        0xEB, 0x20, 0xEC, 0x20, 0xED, 0x20, 0xEE, 0x20, 0xEF, 0x20},
       {0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20,
        0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20,
        0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20,
        0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20}},
      // All 8 first bytes of 4-byte sequences, each followed by a space
      // (generates 8 invalid char + space sequences):
      {{0xF0, 0x20, 0xF1, 0x20, 0xF2, 0x20, 0xF3, 0x20, 0xF4, 0x20, 0xF5, 0x20,
        0xF6, 0x20, 0xF7, 0x20},
       {0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20,
        0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20}},
      // All 4 first bytes of 5-byte sequences (not supported), each followed by
      // a space (generates 4 invalid char + space sequences):
      {{0xF8, 0x20, 0xF9, 0x20, 0xFA, 0x20, 0xFB, 0x20},
       {0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20, 0xFFFD, 0x20}},
      // All 2 first bytes of 6-byte sequences (not supported), each followed by
      // a space (generates 2 invalid char + space sequences):
      {{0xFC, 0x20, 0xFD, 0x20}, {0xFFFD, 0x20, 0xFFFD, 0x20}},

      // Sequences with last continuation byte missing. Normally the whole
      // incomplete sequence generates a single invalid character (exceptions
      // explained below).

      // 2-byte sequences with last byte missing
      {{0xC0}, {0xFFFD}},
      {{0xDF}, {0xFFFD}},
      // 3-byte sequences with last byte missing.
      {{0xE8, 0x80}, {0xFFFD}},
      {{0xE0, 0xBF}, {0xFFFD}},
      {{0xEF, 0xBF}, {0xFFFD}},
      // Start of an overlong sequence. The first "maximal subpart" is the first
      // byte; it creates an invalid character. Each following byte generates an
      // invalid character too.
      {{0xE0, 0x80}, {0xFFFD, 0xFFFD}},
      // 4-byte sequences with last byte missing
      {{0xF1, 0x80, 0x80}, {0xFFFD}},
      {{0xF4, 0x8F, 0xBF}, {0xFFFD}},
      // Start of an overlong sequence. The first "maximal subpart" is the first
      // byte; it creates an invalid character. Each following byte generates an
      // invalid character too.
      {{0xF0, 0x80, 0x80}, {0xFFFD, 0xFFFD, 0xFFFD}},
      // 5-byte sequences (not supported) with last byte missing
      {{0xF8, 0x80, 0x80, 0x80}, {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xFB, 0xBF, 0xBF, 0xBF}, {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      // 6-byte sequences (not supported) with last byte missing
      {{0xFC, 0x80, 0x80, 0x80, 0x80},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xFD, 0xBF, 0xBF, 0xBF, 0xBF},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},

      // Concatenation of incomplete sequences: above incomplete sequences
      // concatenated.
      {{0xC0, 0xDF, 0xE8, 0x80, 0xE0, 0xBF, 0xEF, 0xBF, 0xE0, 0x80,
        0xF1, 0x80, 0x80, 0xF4, 0x8F, 0xBF, 0xF0, 0x80, 0x80, 0xF8,
        0x80, 0x80, 0x80, 0xFB, 0xBF, 0xBF, 0xBF, 0xFC, 0x80, 0x80,
        0x80, 0x80, 0xFD, 0xBF, 0xBF, 0xBF, 0xBF},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD,
        0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD,
        0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD,
        0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},

      // Incomplete sequence tests repeated with a space after the incomplete
      // sequence.

      // 2-byte sequences with last byte missing
      {{0xC0, 0x20}, {0xFFFD, 0x20}},
      {{0xDF, 0x20}, {0xFFFD, 0x20}},
      // 3-byte sequences with last byte missing
      {{0xE8, 0x80, 0x20}, {0xFFFD, 0x20}},
      {{0xE0, 0xBF, 0x20}, {0xFFFD, 0x20}},
      {{0xEF, 0xBF, 0x20}, {0xFFFD, 0x20}},
      // Start of overlong 3-byte sequence with last byte missing
      {{0xE0, 0x80, 0x20}, {0xFFFD, 0xFFFD, 0x20}},
      // 4-byte sequences with last byte missing
      {{0xF1, 0x80, 0x80, 0x20}, {0xFFFD, 0x20}},
      {{0xF4, 0x8F, 0xBF, 0x20}, {0xFFFD, 0x20}},
      // Start of overlong 4-byte sequence with last byte missing
      {{0xF0, 0x80, 0x80, 0x20}, {0xFFFD, 0xFFFD, 0xFFFD, 0x20}},
      // 5-byte sequences (not supported) with last byte missing
      {{0xF8, 0x80, 0x80, 0x80, 0x20}, {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0x20}},
      {{0xFB, 0xBF, 0xBF, 0xBF, 0x20}, {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0x20}},
      // 6-byte sequences (not supported) with last byte missing
      {{0xFC, 0x80, 0x80, 0x80, 0x80, 0x20},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0x20}},
      {{0xFD, 0xBF, 0xBF, 0xBF, 0xBF, 0x20},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0x20}},

      // Impossible bytes
      {{0xFE}, {0xFFFD}},
      {{0xFF}, {0xFFFD}},
      {{0xFE, 0xFE, 0xFF, 0xFF}, {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      // Lead-byte-like bytes which aren't valid lead bytes.
      {{0xC0}, {0xFFFD}},
      {{0xC0, 0xAA}, {0xFFFD, 0xFFFD}},
      {{0xC1}, {0xFFFD}},
      {{0xC1, 0xAA}, {0xFFFD, 0xFFFD}},
      {{0xF5}, {0xFFFD}},
      {{0xF5, 0xAA, 0xAA, 0xAA}, {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xF6}, {0xFFFD}},
      {{0xF6, 0xAA, 0xAA, 0xAA}, {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xF7}, {0xFFFD}},
      {{0xF7, 0xAA, 0xAA, 0xAA}, {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xF8}, {0xFFFD}},
      {{0xF8, 0xAA, 0xAA, 0xAA}, {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xF9}, {0xFFFD}},
      {{0xF9, 0xAA, 0xAA, 0xAA}, {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xFA}, {0xFFFD}},
      {{0xFA, 0xAA, 0xAA, 0xAA}, {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xFB}, {0xFFFD}},
      {{0xFB, 0xAA, 0xAA, 0xAA}, {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xFC}, {0xFFFD}},
      {{0xFC, 0xAA, 0xAA, 0xAA}, {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xFD}, {0xFFFD}},
      {{0xFD, 0xAA, 0xAA, 0xAA}, {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xFE}, {0xFFFD}},
      {{0xFE, 0xAA, 0xAA, 0xAA}, {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xFF}, {0xFFFD}},
      {{0xFF, 0xAA, 0xAA, 0xAA}, {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},

      // Overlong sequences:

      // Overlong encodings for "/"
      {{0xC0, 0xAF}, {0xFFFD, 0xFFFD}},
      {{0xE0, 0x80, 0xAF}, {0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xF0, 0x80, 0x80, 0xAF}, {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      // 5-byte sequence (not supported anyway)
      {{0xF8, 0x80, 0x80, 0x80, 0xAF},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      // 6-byte sequence (not supported anyway)
      {{0xFC, 0x80, 0x80, 0x80, 0x80, 0xAF},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},

      // Maximum overlong sequences
      {{0xC1, 0xBF}, {0xFFFD, 0xFFFD}},
      {{0xE0, 0x9F, 0xBF}, {0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xF0, 0x8F, 0xBF, 0xBF}, {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      // 5-byte sequence (not supported anyway)
      {{0xF8, 0x87, 0xBF, 0xBF, 0xBF},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      // 6-byte sequence (not supported anyway)
      {{0xFC, 0x83, 0xBF, 0xBF, 0xBF, 0xBF},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},

      // Overlong encodings for 0
      {{0xC0, 0x80}, {0xFFFD, 0xFFFD}},
      {{0xE0, 0x80, 0x80}, {0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xF0, 0x80, 0x80, 0x80}, {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      // 5-byte sequence (not supported anyway)
      {{0xF8, 0x80, 0x80, 0x80, 0x80},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      // 6-byte sequence (not supported anyway)
      {{0xFC, 0x80, 0x80, 0x80, 0x80, 0x80},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},

      // Illegal code positions:

      // Single UTF-16 surrogates
      {{0xED, 0xA0, 0x80}, {0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xED, 0xA0, 0x80}, {0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xED, 0xAD, 0xBF}, {0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xED, 0xAE, 0x80}, {0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xED, 0xAF, 0xBF}, {0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xED, 0xB0, 0x80}, {0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xED, 0xBE, 0x80}, {0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xED, 0xBF, 0xBF}, {0xFFFD, 0xFFFD, 0xFFFD}},

      // Paired surrogates
      {{0xED, 0xA0, 0x80, 0xED, 0xB0, 0x80},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xED, 0xA0, 0x80, 0xED, 0xBF, 0xBF},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xED, 0xAD, 0xBF, 0xED, 0xB0, 0x80},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xED, 0xAD, 0xBF, 0xED, 0xBF, 0xBF},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xED, 0xAE, 0x80, 0xED, 0xB0, 0x80},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xED, 0xAE, 0x80, 0xED, 0xBF, 0xBF},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xED, 0xAF, 0xBF, 0xED, 0xB0, 0x80},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},
      {{0xED, 0xAF, 0xBF, 0xED, 0xBF, 0xBF},
       {0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD}},

      // Surrogates with the last byte missing.
      {{0xED, 0xA0}, {0xFFFD, 0xFFFD}},
      {{0xED, 0xA0}, {0xFFFD, 0xFFFD}},
      {{0xED, 0xAD}, {0xFFFD, 0xFFFD}},
      {{0xED, 0xAE}, {0xFFFD, 0xFFFD}},
      {{0xED, 0xAF}, {0xFFFD, 0xFFFD}},
      {{0xED, 0xB0}, {0xFFFD, 0xFFFD}},
      {{0xED, 0xBE}, {0xFFFD, 0xFFFD}},
      {{0xED, 0xBF}, {0xFFFD, 0xFFFD}},

      // Other non-characters
      {{0xEF, 0xBF, 0xBE}, {0xFFFE}},
      {{0xEF, 0xBF, 0xBF}, {0xFFFF}},
      {{0xEF, 0xB7, 0x90, 0xEF, 0xB7, 0x91, 0xEF, 0xB7, 0x92, 0xEF, 0xB7, 0x93,
        0xEF, 0xB7, 0x94, 0xEF, 0xB7, 0x95, 0xEF, 0xB7, 0x96, 0xEF, 0xB7, 0x97,
        0xEF, 0xB7, 0x98, 0xEF, 0xB7, 0x99, 0xEF, 0xB7, 0x9A, 0xEF, 0xB7, 0x9B,
        0xEF, 0xB7, 0x9C, 0xEF, 0xB7, 0x9D, 0xEF, 0xB7, 0x9E, 0xEF, 0xB7, 0x9F,
        0xEF, 0xB7, 0xA0, 0xEF, 0xB7, 0xA1, 0xEF, 0xB7, 0xA2, 0xEF, 0xB7, 0xA3,
        0xEF, 0xB7, 0xA4, 0xEF, 0xB7, 0xA5, 0xEF, 0xB7, 0xA6, 0xEF, 0xB7, 0xA7,
        0xEF, 0xB7, 0xA8, 0xEF, 0xB7, 0xA9, 0xEF, 0xB7, 0xAA, 0xEF, 0xB7, 0xAB,
        0xEF, 0xB7, 0xAC, 0xEF, 0xB7, 0xAD, 0xEF, 0xB7, 0xAE, 0xEF, 0xB7, 0xAF},
       {0xFDD0, 0xFDD1, 0xFDD2, 0xFDD3, 0xFDD4, 0xFDD5, 0xFDD6, 0xFDD7,
        0xFDD8, 0xFDD9, 0xFDDA, 0xFDDB, 0xFDDC, 0xFDDD, 0xFDDE, 0xFDDF,
        0xFDE0, 0xFDE1, 0xFDE2, 0xFDE3, 0xFDE4, 0xFDE5, 0xFDE6, 0xFDE7,
        0xFDE8, 0xFDE9, 0xFDEA, 0xFDEB, 0xFDEC, 0xFDED, 0xFDEE, 0xFDEF}},
      {{0xF0, 0x9F, 0xBF, 0xBE, 0xF0, 0x9F, 0xBF, 0xBF, 0xF0, 0xAF, 0xBF,
        0xBE, 0xF0, 0xAF, 0xBF, 0xBF, 0xF0, 0xBF, 0xBF, 0xBE, 0xF0, 0xBF,
        0xBF, 0xBF, 0xF1, 0x8F, 0xBF, 0xBE, 0xF1, 0x8F, 0xBF, 0xBF, 0xF1,
        0x9F, 0xBF, 0xBE, 0xF1, 0x9F, 0xBF, 0xBF, 0xF1, 0xAF, 0xBF, 0xBE,
        0xF1, 0xAF, 0xBF, 0xBF, 0xF1, 0xBF, 0xBF, 0xBE, 0xF1, 0xBF, 0xBF,
        0xBF, 0xF2, 0x8F, 0xBF, 0xBE, 0xF2, 0x8F, 0xBF, 0xBF},
       {0x1FFFE, 0x1FFFF, 0x2FFFE, 0x2FFFF, 0x3FFFE, 0x3FFFF, 0x4FFFE, 0x4FFFF,
        0x5FFFE, 0x5FFFF, 0x6FFFE, 0x6FFFF, 0x7FFFE, 0x7FFFF, 0x8FFFE,
        0x8FFFF}},
  };

  for (auto test : data) {
    // For figuring out which test fails:
    fprintf(stderr, "test: ");
    for (auto b : test.bytes) {
      fprintf(stderr, "%x ", b);
    }
    fprintf(stderr, "\n");

    std::vector<unibrow::uchar> output_normal;
    DecodeNormally(test.bytes, &output_normal);

    CHECK_EQ(output_normal.size(), test.unicode_expected.size());
    for (size_t i = 0; i < output_normal.size(); ++i) {
      CHECK_EQ(output_normal[i], test.unicode_expected[i]);
    }

    std::vector<unibrow::uchar> output_incremental;
    DecodeIncrementally(test.bytes, &output_incremental);

    CHECK_EQ(output_incremental.size(), test.unicode_expected.size());
    for (size_t i = 0; i < output_incremental.size(); ++i) {
      CHECK_EQ(output_incremental[i], test.unicode_expected[i]);
    }

    std::vector<unibrow::uchar> output_utf16;
    DecodeUtf16(test.bytes, &output_utf16);

    CHECK_EQ(output_utf16.size(), test.unicode_expected.size());
    for (size_t i = 0; i < output_utf16.size(); ++i) {
      CHECK_EQ(output_utf16[i], test.unicode_expected[i]);
    }
  }
}

}  // namespace internal
}  // namespace v8