formats/bmff/offset_adjustment_test.cc

// Copyright 2026 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//

#include "formats/bmff/offset_adjustment.h"

#include <cstdint>
#include <optional>
#include <string>
#include <vector>

#include "absl/status/status.h"
#include "absl/status/status_matchers.h"
#include "absl/strings/str_cat.h"
#include "absl/strings/string_view.h"
#include "formats/bmff/box_header.h"
#include "gmock/gmock.h"
#include "gtest/gtest.h"
#include "riegeli/base/types.h"
#include "riegeli/bytes/string_reader.h"
#include "riegeli/bytes/string_writer.h"
#include "testing/test_string_utils.h"

namespace credentio {
namespace {

using ::absl_testing::StatusIs;
using ::credentio_testing::Uint16Str;
using ::credentio_testing::Uint32Str;
using ::credentio_testing::Uint64Str;
using ::credentio_testing::Uint8Str;
using ::testing::ElementsAre;
using ::testing::HasSubstr;

class NoSizeStringReader : public riegeli::StringReader<> {
 public:
  using riegeli::StringReader<>::StringReader;
  bool SupportsSize() override { return false; }
};

class SizeNotValuedStringReader : public riegeli::StringReader<> {
 public:
  using riegeli::StringReader<>::StringReader;
  bool SupportsSize() override { return true; }

 protected:
  std::optional<riegeli::Position> SizeImpl() override { return std::nullopt; }
};

class CustomSizeStringReader : public riegeli::StringReader<> {
 public:
  explicit CustomSizeStringReader(absl::string_view src,
                                  riegeli::Position reported_size)
      : riegeli::StringReader<>(src), reported_size_(reported_size) {}
  bool SupportsSize() override { return true; }

 protected:
  std::optional<riegeli::Position> SizeImpl() override {
    return reported_size_;
  }

 private:
  riegeli::Position reported_size_;
};

TEST(OffsetAdjustmentTest, Stco) {
  std::string data = absl::StrCat(Uint32Str(2),    // entry_count
                                  Uint32Str(100),  // offset 1
                                  Uint32Str(200)   // offset 2
  );

  riegeli::StringReader reader(data);
  auto box_or = ParseStco(reader);
  ABSL_ASSERT_OK(box_or);
  StcoBox box = *box_or;
  EXPECT_THAT(box.offsets, ElementsAre(100, 200));

  AdjustOffsets(box, 50);
  EXPECT_THAT(box.offsets, ElementsAre(150, 250));

  std::string serialized;
  riegeli::StringWriter writer(&serialized);
  ABSL_ASSERT_OK(SerializeStco(box, writer));
  writer.Close();

  std::string expected_data = absl::StrCat(Uint32Str(2),    // entry_count
                                           Uint32Str(150),  // offset 1
                                           Uint32Str(250)   // offset 2
  );
  EXPECT_EQ(serialized, expected_data);
}

TEST(OffsetAdjustmentTest, Co64) {
  std::string data = absl::StrCat(Uint32Str(2),    // entry_count
                                  Uint64Str(100),  // offset 1
                                  Uint64Str(200)   // offset 2
  );

  riegeli::StringReader reader(data);
  auto box_or = ParseCo64(reader);
  ABSL_ASSERT_OK(box_or);
  Co64Box box = *box_or;
  EXPECT_THAT(box.offsets, ElementsAre(100, 200));

  AdjustOffsets(box, 50);
  EXPECT_THAT(box.offsets, ElementsAre(150, 250));

  std::string serialized;
  riegeli::StringWriter writer(&serialized);
  ABSL_ASSERT_OK(SerializeCo64(box, writer));
  writer.Close();

  std::string expected_data = absl::StrCat(Uint32Str(2),    // entry_count
                                           Uint64Str(150),  // offset 1
                                           Uint64Str(250)   // offset 2
  );
  EXPECT_EQ(serialized, expected_data);
}

TEST(OffsetAdjustmentTest, SaioVersion0NoAuxInfo) {
  BmffBoxHeader header;
  header.version = 0;
  header.flags = std::string("\x00\x00\x00", 3);

  std::string data = absl::StrCat(Uint32Str(2),    // entry_count
                                  Uint32Str(100),  // offset 1
                                  Uint32Str(200)   // offset 2
  );

  riegeli::StringReader reader(data);
  auto box_or = ParseSaio(reader, header);
  ABSL_ASSERT_OK(box_or);
  SaioBox box = *box_or;
  EXPECT_THAT(box.offsets, ElementsAre(100, 200));

  AdjustOffsets(box, 50);
  EXPECT_THAT(box.offsets, ElementsAre(150, 250));

  std::string serialized;
  riegeli::StringWriter writer(&serialized);
  ABSL_ASSERT_OK(SerializeSaio(box, header, writer));
  writer.Close();

  std::string expected_data = absl::StrCat(Uint32Str(2),    // entry_count
                                           Uint32Str(150),  // offset 1
                                           Uint32Str(250)   // offset 2
  );
  EXPECT_EQ(serialized, expected_data);
}

TEST(OffsetAdjustmentTest, SaioVersion1WithAuxInfo) {
  BmffBoxHeader header;
  header.version = 1;
  header.flags = std::string("\x00\x00\x01", 3);  // flags & 1

  std::string data =
      absl::StrCat(Uint32Str(0x12345678),  // aux_info_type
                   Uint32Str(0xabcdef01),  // aux_info_type_parameter
                   Uint32Str(2),           // entry_count
                   Uint64Str(100),         // offset 1
                   Uint64Str(200)          // offset 2
      );

  riegeli::StringReader reader(data);
  auto box_or = ParseSaio(reader, header);
  ABSL_ASSERT_OK(box_or);
  SaioBox box = *box_or;
  EXPECT_EQ(box.aux_info_type, 0x12345678);
  EXPECT_EQ(box.aux_info_type_parameter, 0xabcdef01);
  EXPECT_THAT(box.offsets, ElementsAre(100, 200));

  AdjustOffsets(box, 50);
  EXPECT_THAT(box.offsets, ElementsAre(150, 250));

  std::string serialized;
  riegeli::StringWriter writer(&serialized);
  ABSL_ASSERT_OK(SerializeSaio(box, header, writer));
  writer.Close();

  std::string expected_data =
      absl::StrCat(Uint32Str(0x12345678),  // aux_info_type
                   Uint32Str(0xabcdef01),  // aux_info_type_parameter
                   Uint32Str(2),           // entry_count
                   Uint64Str(150),         // offset 1
                   Uint64Str(250)          // offset 2
      );
  EXPECT_EQ(serialized, expected_data);
}

TEST(OffsetAdjustmentTest, IlocVersion0) {
  BmffBoxHeader header;
  header.version = 0;

  // offset_size = 4, length_size = 4 -> 0x44
  // base_offset_size = 4, index_size = 0 -> 0x40
  std::string data =
      absl::StrCat(Uint8Str(0x44),  // offset_size, length_size
                   Uint8Str(0x40),  // base_offset_size, index_size
                   Uint16Str(1),    // item_count
                   // Item 1
                   Uint16Str(1),     // item_id
                   Uint16Str(0),     // data_reference_index
                   Uint32Str(1000),  // base_offset
                   Uint16Str(2),     // extent_count
                   // Extent 1
                   Uint32Str(100),  // offset
                   Uint32Str(20),   // length
                   // Extent 2
                   Uint32Str(200),  // offset
                   Uint32Str(30)    // length
      );

  riegeli::StringReader reader(data);
  auto box_or = ParseIloc(reader, header);
  ABSL_ASSERT_OK(box_or);
  IlocBox box = *box_or;
  EXPECT_EQ(box.offset_size, 4);
  EXPECT_EQ(box.length_size, 4);
  EXPECT_EQ(box.base_offset_size, 4);
  EXPECT_EQ(box.index_size, 0);
  ASSERT_EQ(box.items.size(), 1);
  EXPECT_EQ(box.items[0].item_id, 1);
  EXPECT_EQ(box.items[0].data_reference_index, 0);
  EXPECT_EQ(box.items[0].base_offset, 1000);
  ASSERT_EQ(box.items[0].extents.size(), 2);
  EXPECT_EQ(box.items[0].extents[0].offset, 100);
  EXPECT_EQ(box.items[0].extents[0].length, 20);
  EXPECT_EQ(box.items[0].extents[1].offset, 200);
  EXPECT_EQ(box.items[0].extents[1].length, 30);

  AdjustOffsets(box, 50);
  EXPECT_EQ(box.items[0].base_offset, 1050);
  EXPECT_EQ(box.items[0].extents[0].offset, 100);
  EXPECT_EQ(box.items[0].extents[1].offset, 200);

  std::string serialized;
  riegeli::StringWriter writer(&serialized);
  ABSL_ASSERT_OK(SerializeIloc(box, header, writer));
  writer.Close();

  std::string expected_data =
      absl::StrCat(Uint8Str(0x44),  // offset_size, length_size
                   Uint8Str(0x40),  // base_offset_size, index_size
                   Uint16Str(1),    // item_count
                   // Item 1
                   Uint16Str(1),     // item_id
                   Uint16Str(0),     // data_reference_index
                   Uint32Str(1050),  // base_offset
                   Uint16Str(2),     // extent_count
                   // Extent 1
                   Uint32Str(100),  // offset
                   Uint32Str(20),   // length
                   // Extent 2
                   Uint32Str(200),  // offset
                   Uint32Str(30)    // length
      );
  EXPECT_EQ(serialized, expected_data);
}

TEST(OffsetAdjustmentTest, IlocVersion1WithIndex) {
  BmffBoxHeader header;
  header.version = 1;

  // offset_size = 4, length_size = 4 -> 0x44
  // base_offset_size = 4, index_size = 4 -> 0x44
  std::string data =
      absl::StrCat(Uint8Str(0x44),  // offset_size, length_size
                   Uint8Str(0x44),  // base_offset_size, index_size
                   Uint16Str(1),    // item_count
                   // Item 1
                   Uint16Str(1),       // item_id
                   Uint16Str(0x1230),  // reserved_and_construction_method
                   Uint16Str(0),       // data_reference_index
                   Uint32Str(1000),    // base_offset
                   Uint16Str(1),       // extent_count
                   // Extent 1
                   Uint32Str(5),    // index
                   Uint32Str(100),  // offset
                   Uint32Str(20)    // length
      );

  riegeli::StringReader reader(data);
  auto box_or = ParseIloc(reader, header);
  ABSL_ASSERT_OK(box_or);
  IlocBox box = *box_or;
  EXPECT_EQ(box.offset_size, 4);
  EXPECT_EQ(box.length_size, 4);
  EXPECT_EQ(box.base_offset_size, 4);
  EXPECT_EQ(box.index_size, 4);
  ASSERT_EQ(box.items.size(), 1);
  EXPECT_EQ(box.items[0].item_id, 1);
  EXPECT_EQ(box.items[0].construction_method, 0x1230);
  EXPECT_EQ(box.items[0].data_reference_index, 0);
  EXPECT_EQ(box.items[0].base_offset, 1000);
  ASSERT_EQ(box.items[0].extents.size(), 1);
  EXPECT_EQ(box.items[0].extents[0].index, 5);
  EXPECT_EQ(box.items[0].extents[0].offset, 100);
  EXPECT_EQ(box.items[0].extents[0].length, 20);

  AdjustOffsets(box, 50);
  EXPECT_EQ(box.items[0].base_offset, 1050);
  EXPECT_EQ(box.items[0].extents[0].offset, 100);

  std::string serialized;
  riegeli::StringWriter writer(&serialized);
  ABSL_ASSERT_OK(SerializeIloc(box, header, writer));
  writer.Close();

  std::string expected_data =
      absl::StrCat(Uint8Str(0x44),  // offset_size, length_size
                   Uint8Str(0x44),  // base_offset_size, index_size
                   Uint16Str(1),    // item_count
                   // Item 1
                   Uint16Str(1),       // item_id
                   Uint16Str(0x1230),  // reserved_and_construction_method
                   Uint16Str(0),       // data_reference_index
                   Uint32Str(1050),    // base_offset
                   Uint16Str(1),       // extent_count
                   // Extent 1
                   Uint32Str(5),    // index
                   Uint32Str(100),  // offset
                   Uint32Str(20)    // length
      );
  EXPECT_EQ(serialized, expected_data);
}

TEST(OffsetAdjustmentTest, IlocVersion2LargeSizes) {
  BmffBoxHeader header;
  header.version = 2;

  // offset_size = 8, length_size = 8 -> 0x88
  // base_offset_size = 8, index_size = 8 -> 0x88
  std::string data =
      absl::StrCat(Uint8Str(0x88),  // offset_size, length_size
                   Uint8Str(0x88),  // base_offset_size, index_size
                   Uint32Str(1),    // item_count (32-bit in v2)
                   // Item 1
                   Uint32Str(1),       // item_id (32-bit in v2)
                   Uint16Str(0x1230),  // reserved_and_construction_method
                   Uint16Str(0),       // data_reference_index
                   Uint64Str(1000),    // base_offset
                   Uint16Str(1),       // extent_count
                   // Extent 1
                   Uint64Str(5),    // index
                   Uint64Str(100),  // offset
                   Uint64Str(20)    // length
      );

  riegeli::StringReader reader(data);
  auto box_or = ParseIloc(reader, header);
  ABSL_ASSERT_OK(box_or);
  IlocBox box = *box_or;
  EXPECT_EQ(box.offset_size, 8);
  EXPECT_EQ(box.length_size, 8);
  EXPECT_EQ(box.base_offset_size, 8);
  EXPECT_EQ(box.index_size, 8);
  ASSERT_EQ(box.items.size(), 1);
  EXPECT_EQ(box.items[0].item_id, 1);
  EXPECT_EQ(box.items[0].construction_method, 0x1230);
  EXPECT_EQ(box.items[0].data_reference_index, 0);
  EXPECT_EQ(box.items[0].base_offset, 1000);
  ASSERT_EQ(box.items[0].extents.size(), 1);
  EXPECT_EQ(box.items[0].extents[0].index, 5);
  EXPECT_EQ(box.items[0].extents[0].offset, 100);
  EXPECT_EQ(box.items[0].extents[0].length, 20);

  AdjustOffsets(box, 50);
  EXPECT_EQ(box.items[0].base_offset, 1050);
  EXPECT_EQ(box.items[0].extents[0].offset, 100);

  std::string serialized;
  riegeli::StringWriter writer(&serialized);
  ABSL_ASSERT_OK(SerializeIloc(box, header, writer));
  writer.Close();

  std::string expected_data =
      absl::StrCat(Uint8Str(0x88),  // offset_size, length_size
                   Uint8Str(0x88),  // base_offset_size, index_size
                   Uint32Str(1),    // item_count (32-bit in v2)
                   // Item 1
                   Uint32Str(1),       // item_id (32-bit in v2)
                   Uint16Str(0x1230),  // reserved_and_construction_method
                   Uint16Str(0),       // data_reference_index
                   Uint64Str(1050),    // base_offset
                   Uint16Str(1),       // extent_count
                   // Extent 1
                   Uint64Str(5),    // index
                   Uint64Str(100),  // offset
                   Uint64Str(20)    // length
      );
  EXPECT_EQ(serialized, expected_data);
}

TEST(OffsetAdjustmentTest, IlocNonZeroDataReferenceIndexNotAdjusted) {
  BmffBoxHeader header;
  header.version = 0;

  std::string data =
      absl::StrCat(Uint8Str(0x44),  // offset_size, length_size
                   Uint8Str(0x40),  // base_offset_size, index_size
                   Uint16Str(1),    // item_count
                   // Item 1
                   Uint16Str(1),     // item_id
                   Uint16Str(1),     // data_reference_index (Non-zero)
                   Uint32Str(1000),  // base_offset
                   Uint16Str(1),     // extent_count
                   // Extent 1
                   Uint32Str(100),  // offset
                   Uint32Str(20)    // length
      );

  riegeli::StringReader reader(data);
  auto box_or = ParseIloc(reader, header);
  ABSL_ASSERT_OK(box_or);
  IlocBox box = *box_or;
  AdjustOffsets(box, 50);
  // Offset should NOT be adjusted because data_reference_index != 0
  EXPECT_EQ(box.items[0].extents[0].offset, 100);
}

TEST(OffsetAdjustmentTest, IlocZeroBaseOffsetSize) {
  BmffBoxHeader header;
  header.version = 0;

  // offset_size = 4, length_size = 4 -> 0x44
  // base_offset_size = 0, index_size = 0 -> 0x00
  std::string data =
      absl::StrCat(Uint8Str(0x44),  // offset_size, length_size
                   Uint8Str(0x00),  // base_offset_size, index_size
                   Uint16Str(1),    // item_count
                   // Item 1
                   Uint16Str(1),  // item_id
                   Uint16Str(0),  // data_reference_index
                   Uint16Str(1),  // extent_count
                   // Extent 1
                   Uint32Str(100),  // offset
                   Uint32Str(20)    // length
      );

  riegeli::StringReader reader(data);
  auto box_or = ParseIloc(reader, header);
  ABSL_ASSERT_OK(box_or);
  IlocBox box = *box_or;
  AdjustOffsets(box, 50);
  // Extent offset should be adjusted because base_offset_size == 0
  EXPECT_EQ(box.items[0].extents[0].offset, 150);
}

TEST(OffsetAdjustmentTest, IlocZeroOffsetSize) {
  BmffBoxHeader header;
  header.version = 0;

  // offset_size = 0, length_size = 4 -> 0x04
  // base_offset_size = 4, index_size = 0 -> 0x40
  std::string data =
      absl::StrCat(Uint8Str(0x04),  // offset_size, length_size
                   Uint8Str(0x40),  // base_offset_size, index_size
                   Uint16Str(1),    // item_count
                   // Item 1
                   Uint16Str(1),     // item_id
                   Uint16Str(0),     // data_reference_index
                   Uint32Str(1000),  // base_offset
                   Uint16Str(1),     // extent_count
                   // Extent 1
                   Uint32Str(20)  // length (No offset)
      );

  riegeli::StringReader reader(data);
  auto box_or = ParseIloc(reader, header);
  ABSL_ASSERT_OK(box_or);
  IlocBox box = *box_or;
  AdjustOffsets(box, 50);
  // Base offset should be adjusted
  EXPECT_EQ(box.items[0].base_offset, 1050);
}

TEST(OffsetAdjustmentTest, IlocNonZeroConstructionMethodNotAdjusted) {
  BmffBoxHeader header;
  header.version = 1;

  // offset_size = 4, length_size = 4 -> 0x44
  // base_offset_size = 4, index_size = 0 -> 0x40
  std::string data =
      absl::StrCat(Uint8Str(0x44),  // offset_size, length_size
                   Uint8Str(0x40),  // base_offset_size, index_size
                   Uint16Str(1),    // item_count
                   // Item 1
                   Uint16Str(1),       // item_id
                   Uint16Str(0x0001),  // reserved (0), method (1)
                   Uint16Str(0),       // data_reference_index
                   Uint32Str(1000),    // base_offset
                   Uint16Str(1),       // extent_count
                   // Extent 1
                   Uint32Str(100),  // offset
                   Uint32Str(20)    // length
      );

  riegeli::StringReader reader(data);
  auto box_or = ParseIloc(reader, header);
  ABSL_ASSERT_OK(box_or);
  IlocBox box = *box_or;
  AdjustOffsets(box, 50);
  // Offset should NOT be adjusted because construction_method != 0
  EXPECT_EQ(box.items[0].base_offset, 1000);
  EXPECT_EQ(box.items[0].extents[0].offset, 100);
}

TEST(OffsetAdjustmentTest, IlocSerializeInvalidSize) {
  BmffBoxHeader header;
  header.version = 0;

  IlocBox box;
  box.offset_size = 4;
  box.length_size = 4;
  box.base_offset_size = 1;  // Invalid size
  box.index_size = 0;
  box.items.resize(1);
  box.items[0].item_id = 1;
  box.items[0].data_reference_index = 0;
  box.items[0].base_offset = 1000;
  box.items[0].extents.resize(1);
  box.items[0].extents[0].offset = 100;
  box.items[0].extents[0].length = 20;

  std::string serialized;
  riegeli::StringWriter writer(&serialized);
  EXPECT_THAT(SerializeIloc(box, header, writer),
              StatusIs(absl::StatusCode::kInvalidArgument,
                       HasSubstr("invalid byte_size: 1")));
  writer.Close();
}

// The following tests use counts that exceed the remaining data. They must fail
// before reserving memory for the declared entries, which would otherwise take
// gigabytes.

TEST(OffsetAdjustmentTest, StcoEntryCountExceedsData) {
  std::string data = absl::StrCat(Uint32Str(0xffffffff), Uint32Str(100));
  riegeli::StringReader reader(data);
  EXPECT_THAT(ParseStco(reader),
              StatusIs(absl::StatusCode::kDataLoss,
                       HasSubstr("entry count 4294967295 exceeds the "
                                 "remaining 4 bytes")));
}

TEST(OffsetAdjustmentTest, Co64EntryCountExceedsData) {
  // Two entries need 16 bytes, but only 15 remain.
  std::string data =
      absl::StrCat(Uint32Str(2), Uint64Str(100), std::string(7, '\0'));
  riegeli::StringReader reader(data);
  EXPECT_THAT(ParseCo64(reader),
              StatusIs(absl::StatusCode::kDataLoss,
                       HasSubstr("entry count 2 exceeds the remaining 15 "
                                 "bytes")));
}

TEST(OffsetAdjustmentTest, SaioEntryCountExceedsData) {
  BmffBoxHeader header;
  header.version = 1;
  header.flags = std::string("\x00\x00\x00", 3);
  std::string data = absl::StrCat(Uint32Str(0xffffffff), Uint64Str(100));
  riegeli::StringReader reader(data);
  EXPECT_THAT(ParseSaio(reader, header),
              StatusIs(absl::StatusCode::kDataLoss,
                       HasSubstr("entry count 4294967295 exceeds the "
                                 "remaining 8 bytes")));
}

TEST(OffsetAdjustmentTest, SaioVersion0EntryCountExceedsData) {
  // Two version 0 entries need 8 bytes, but only 7 remain.
  BmffBoxHeader header;
  header.version = 0;
  header.flags = std::string("\x00\x00\x00", 3);
  std::string data =
      absl::StrCat(Uint32Str(2), Uint32Str(100), std::string(3, '\0'));
  riegeli::StringReader reader(data);
  EXPECT_THAT(ParseSaio(reader, header),
              StatusIs(absl::StatusCode::kDataLoss,
                       HasSubstr("entry count 2 exceeds the remaining 7 "
                                 "bytes")));
}

TEST(OffsetAdjustmentTest, IlocItemCountExceedsData) {
  BmffBoxHeader header;
  header.version = 2;
  std::string data = absl::StrCat(Uint8Str(0x44),  // offset/length size
                                  Uint8Str(0x00),  // base offset/index size
                                  Uint32Str(0xffffffff),  // item_count
                                  Uint32Str(1));          // item_ID
  riegeli::StringReader reader(data);
  EXPECT_THAT(ParseIloc(reader, header),
              StatusIs(absl::StatusCode::kDataLoss,
                       HasSubstr("entry count 4294967295 exceeds the "
                                 "remaining 4 bytes")));
}

TEST(OffsetAdjustmentTest, IlocExtentCountExceedsData) {
  BmffBoxHeader header;
  header.version = 0;
  std::string data = absl::StrCat(Uint8Str(0x44),     // offset/length size
                                  Uint8Str(0x00),     // base offset/index size
                                  Uint16Str(1),       // item_count
                                  Uint16Str(1),       // item_ID
                                  Uint16Str(0),       // data_reference_index
                                  Uint16Str(0xffff),  // extent_count
                                  Uint32Str(100),     // extent_offset
                                  Uint32Str(20));     // extent_length
  riegeli::StringReader reader(data);
  EXPECT_THAT(ParseIloc(reader, header),
              StatusIs(absl::StatusCode::kDataLoss,
                       HasSubstr("entry count 65535 exceeds the remaining 8 "
                                 "bytes")));
}

TEST(OffsetAdjustmentTest, IlocZeroSizeExtent) {
  // With all extent fields absent, a single extent occupies no bytes and refers
  // to the entire referenced container.
  BmffBoxHeader header;
  header.version = 0;
  std::string data = absl::StrCat(Uint8Str(0x00),  // offset/length size
                                  Uint8Str(0x00),  // base offset/index size
                                  Uint16Str(1),    // item_count
                                  Uint16Str(1),    // item_ID
                                  Uint16Str(0),    // data_reference_index
                                  Uint16Str(1));   // extent_count
  riegeli::StringReader reader(data);
  auto box_or = ParseIloc(reader, header);
  ABSL_ASSERT_OK(box_or);
  const IlocBox& box = *box_or;
  ASSERT_EQ(box.items.size(), 1);
  ASSERT_EQ(box.items[0].extents.size(), 1);
  EXPECT_EQ(box.items[0].extents[0].offset, 0);
  EXPECT_EQ(box.items[0].extents[0].length, 0);
}

TEST(OffsetAdjustmentTest, IlocZeroSizeMultipleExtents) {
  BmffBoxHeader header;
  header.version = 0;
  std::string data = absl::StrCat(Uint8Str(0x00),  // offset/length size
                                  Uint8Str(0x00),  // base offset/index size
                                  Uint16Str(1),    // item_count
                                  Uint16Str(1),    // item_ID
                                  Uint16Str(0),    // data_reference_index
                                  Uint16Str(3));   // extent_count
  riegeli::StringReader reader(data);
  EXPECT_THAT(ParseIloc(reader, header),
              StatusIs(absl::StatusCode::kDataLoss,
                       HasSubstr("iloc item 1 has 3 extents of size 0")));
}

// When the reader cannot report its size, counts cannot be checked up front, so
// parsing proceeds entry by entry and fails at the end of the data.
TEST(OffsetAdjustmentTest, Co64NoSizeReader) {
  std::string data = absl::StrCat(Uint32Str(2), Uint64Str(100), Uint64Str(200));
  NoSizeStringReader reader(data);
  auto box_or = ParseCo64(reader);
  ABSL_ASSERT_OK(box_or);
  EXPECT_THAT(box_or->offsets, ElementsAre(100, 200));
}

TEST(OffsetAdjustmentTest, Co64NoSizeReaderEntryCountExceedsData) {
  std::string data = absl::StrCat(Uint32Str(0xffffffff), Uint64Str(100));
  NoSizeStringReader reader(data);
  EXPECT_THAT(ParseCo64(reader), StatusIs(absl::StatusCode::kDataLoss,
                                          HasSubstr("Failed to read offset")));
}

TEST(OffsetAdjustmentTest, Co64UnknownSizeEntryCountExceedsData) {
  std::string data = absl::StrCat(Uint32Str(0xffffffff), Uint64Str(100));
  SizeNotValuedStringReader reader(data);
  EXPECT_THAT(ParseCo64(reader), StatusIs(absl::StatusCode::kDataLoss,
                                          HasSubstr("Failed to read offset")));
}

TEST(OffsetAdjustmentTest, Co64ReportedSizeSmallerThanPos) {
  std::string data = absl::StrCat(Uint32Str(1), Uint64Str(100));
  CustomSizeStringReader reader(data, /*reported_size=*/0);
  EXPECT_THAT(ParseCo64(reader),
              StatusIs(absl::StatusCode::kDataLoss,
                       HasSubstr("entry count 1 exceeds the remaining 0 "
                                 "bytes")));
}

// When the reader reports a size large enough to satisfy the entry count check
// (e.g. a sparse file or spoofed size), the initial reservation is still capped
// at kMaxEntryCountToReserve rather than allocating for all declared entries.
TEST(OffsetAdjustmentTest, StcoLargeReportedSizeCapsReserve) {
  std::string data = absl::StrCat(Uint32Str(0xffffffff), Uint32Str(100));
  CustomSizeStringReader reader(data, /*reported_size=*/uint64_t{1} << 40);
  EXPECT_THAT(ParseStco(reader), StatusIs(absl::StatusCode::kDataLoss,
                                          HasSubstr("Failed to read offset")));
}

TEST(OffsetAdjustmentTest, Co64LargeReportedSizeCapsReserve) {
  std::string data = absl::StrCat(Uint32Str(0xffffffff), Uint64Str(100));
  CustomSizeStringReader reader(data, /*reported_size=*/uint64_t{1} << 40);
  EXPECT_THAT(ParseCo64(reader), StatusIs(absl::StatusCode::kDataLoss,
                                          HasSubstr("Failed to read offset")));
}

TEST(OffsetAdjustmentTest, SaioLargeReportedSizeCapsReserve) {
  BmffBoxHeader header;
  header.version = 1;
  header.flags = std::string("\x00\x00\x00", 3);
  std::string data = absl::StrCat(Uint32Str(0xffffffff), Uint64Str(100));
  CustomSizeStringReader reader(data, /*reported_size=*/uint64_t{1} << 40);
  EXPECT_THAT(ParseSaio(reader, header),
              StatusIs(absl::StatusCode::kDataLoss,
                       HasSubstr("Failed to read offset")));
}

TEST(OffsetAdjustmentTest, IlocLargeReportedSizeCapsReserve) {
  BmffBoxHeader header;
  header.version = 2;
  std::string data = absl::StrCat(Uint8Str(0x44),         // offset/length size
                                  Uint8Str(0x00),         // base offset/index
                                  Uint32Str(0xffffffff),  // item_count
                                  Uint32Str(1));          // item_ID
  CustomSizeStringReader reader(data, /*reported_size=*/uint64_t{1} << 40);
  EXPECT_THAT(ParseIloc(reader, header), StatusIs(absl::StatusCode::kDataLoss,
                                                  HasSubstr("Failed to read")));
}

// The following tests pin the minimum item and extent sizes for each iloc
// version: the data holds enough bytes for the count only if the size is
// underestimated.

TEST(OffsetAdjustmentTest, IlocVersion2ItemCountUsesFourByteItemId) {
  // A version 2 item has at least 10 bytes: item_ID (4),
  // construction_method (2), data_reference_index (2), and extent_count (2).
  BmffBoxHeader header;
  header.version = 2;
  std::string data = absl::StrCat(Uint8Str(0x44),  // offset/length size
                                  Uint8Str(0x00),  // base offset/index size
                                  Uint32Str(2),    // item_count
                                  std::string(16, '\0'));
  riegeli::StringReader reader(data);
  EXPECT_THAT(ParseIloc(reader, header),
              StatusIs(absl::StatusCode::kDataLoss,
                       HasSubstr("entry count 2 exceeds the remaining 16 "
                                 "bytes")));
}

TEST(OffsetAdjustmentTest, IlocVersion1ItemCountIncludesConstructionMethod) {
  // A version 1 item has at least 8 bytes: item_ID (2),
  // construction_method (2), data_reference_index (2), and extent_count (2).
  BmffBoxHeader header;
  header.version = 1;
  std::string data = absl::StrCat(Uint8Str(0x44),  // offset/length size
                                  Uint8Str(0x00),  // base offset/index size
                                  Uint16Str(2),    // item_count
                                  std::string(12, '\0'));
  riegeli::StringReader reader(data);
  EXPECT_THAT(ParseIloc(reader, header),
              StatusIs(absl::StatusCode::kDataLoss,
                       HasSubstr("entry count 2 exceeds the remaining 12 "
                                 "bytes")));
}

TEST(OffsetAdjustmentTest, IlocItemCountIncludesBaseOffset) {
  // A version 0 item with a 4 byte base_offset has at least 10 bytes:
  // item_ID (2), data_reference_index (2), base_offset (4), and
  // extent_count (2).
  BmffBoxHeader header;
  header.version = 0;
  std::string data = absl::StrCat(Uint8Str(0x44),  // offset/length size
                                  Uint8Str(0x40),  // base offset/index size
                                  Uint16Str(2),    // item_count
                                  std::string(16, '\0'));
  riegeli::StringReader reader(data);
  EXPECT_THAT(ParseIloc(reader, header),
              StatusIs(absl::StatusCode::kDataLoss,
                       HasSubstr("entry count 2 exceeds the remaining 16 "
                                 "bytes")));
}

TEST(OffsetAdjustmentTest, IlocVersion1ExtentCountIncludesIndex) {
  // Each extent has an extent_index (4), extent_offset (4), and
  // extent_length (4).
  BmffBoxHeader header;
  header.version = 1;
  std::string data = absl::StrCat(Uint8Str(0x44),  // offset/length size
                                  Uint8Str(0x04),  // base offset/index size
                                  Uint16Str(1),    // item_count
                                  Uint16Str(1),    // item_ID
                                  Uint16Str(0),    // construction_method
                                  Uint16Str(0),    // data_reference_index
                                  Uint16Str(2),    // extent_count
                                  std::string(16, '\0'));
  riegeli::StringReader reader(data);
  EXPECT_THAT(ParseIloc(reader, header),
              StatusIs(absl::StatusCode::kDataLoss,
                       HasSubstr("entry count 2 exceeds the remaining 16 "
                                 "bytes")));
}

}  // namespace
}  // namespace credentio