// Copyright 2019 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.


#include "components/services/storage/indexed_db/scopes/varint_coding.h"

#include <string_view>

#include "testing/gtest/include/gtest/gtest.h"

namespace content::indexed_db {
namespace {

static std::string WrappedEncodeVarInt(int64_t value) {
  std::string buffer;
  EncodeVarInt(value, &buffer);
  return buffer;
}

TEST(VarIntCoding, Encode) {
  EXPECT_EQ(1u, WrappedEncodeVarInt(0).size());
  EXPECT_EQ(1u, WrappedEncodeVarInt(1).size());
  EXPECT_EQ(2u, WrappedEncodeVarInt(255).size());
  EXPECT_EQ(2u, WrappedEncodeVarInt(256).size());
  EXPECT_EQ(5u, WrappedEncodeVarInt(0xffffffff).size());
  EXPECT_EQ(8u, WrappedEncodeVarInt(0xfffffffffffffll).size());
  EXPECT_EQ(9u, WrappedEncodeVarInt(0x7fffffffffffffffll).size());
}

TEST(VarIntCoding, Decode) {
  std::vector<int64_t> test_cases = {
      0,
      1,
      255,
      256,
      65535,
      655536,
      7711192431755665792ll,
      0x7fffffffffffffffll,
  };

  for (size_t i = 0; i < test_cases.size(); ++i) {
    int64_t n = test_cases[i];
    std::string v = WrappedEncodeVarInt(n);
    ASSERT_GT(v.size(), 0u);
    std::string_view slice(v);
    int64_t res;
    EXPECT_TRUE(DecodeVarInt(&slice, &res));
    EXPECT_EQ(n, res);
    EXPECT_TRUE(slice.empty());

    slice = std::string_view(&*v.begin(), v.size() - 1);
    EXPECT_FALSE(DecodeVarInt(&slice, &res));

    slice = std::string_view(&*v.begin(), static_cast<size_t>(0));
    EXPECT_FALSE(DecodeVarInt(&slice, &res));

    // Verify decoding at an offset, to detect unaligned memory access.
    v.insert(v.begin(), 1u, static_cast<char>(0));
    slice = std::string_view(v).substr(1u);
    EXPECT_TRUE(DecodeVarInt(&slice, &res));
    EXPECT_EQ(n, res);
    EXPECT_TRUE(slice.empty());
  }
}

TEST(VarIntCoding, SingleByteCases) {
  std::vector<unsigned char> test_cases = {0, 1, 127};

  for (size_t i = 0; i < test_cases.size(); ++i) {
    unsigned char n = test_cases[i];

    std::string a = std::string(1, n);
    std::string b = WrappedEncodeVarInt(static_cast<int64_t>(n));

    EXPECT_EQ(a.size(), b.size());
    EXPECT_EQ(*a.begin(), *b.begin());
  }
}

TEST(VarIntCoding, EmbeddedZeroByte) {
  auto arr = std::array<char, 3>{'\x81', '\x00', '\x07'};
  std::string_view input(arr.data(), arr.size());
  int64_t ignored;
  EXPECT_FALSE(DecodeVarInt(&input, &ignored));
}

// When using the max number of bytes (10), the top byte must be exactly 1.
TEST(VarIntCoding, JunkBitsInTopByte) {
  auto arr = std::array<char, 10>{'\x80', '\x80', '\x80', '\x80', '\x80',
                                  '\x80', '\x80', '\x80', '\x80', '\x05'};
  std::string_view input(arr.data(), arr.size());
  int64_t ignored;
  EXPECT_FALSE(DecodeVarInt(&input, &ignored));
}

}  // namespace
}  // namespace content::indexed_db