src/google/protobuf/io/zero_copy_stream_unittest.cc

// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file or at
// https://developers.google.com/open-source/licenses/bsd

// Author: kenton@google.com (Kenton Varda)
//  Based on original Protocol Buffers design by
//  Sanjay Ghemawat, Jeff Dean, and others.
//
// Testing strategy:  For each type of I/O (array, string, file, etc.) we
// create an output stream and write some data to it, then create a
// corresponding input stream to read the same data back and expect it to
// match.  When the data is written, it is written in several small chunks
// of varying sizes, with a BackUp() after each chunk.  It is read back
// similarly, but with chunks separated at different points.  The whole
// process is run with a variety of block sizes for both the input and
// the output.
//
// TODO:  Rewrite this test to bring it up to the standards of all
//   the other proto2 tests.  May want to wait for gTest to implement
//   "parametized tests" so that one set of tests can be used on all the
//   implementations.

#ifndef _WIN32
#include <sys/socket.h>
#include <unistd.h>
#endif
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/types.h>

#include <algorithm>
#include <chrono>
#include <iterator>
#include <memory>
#include <sstream>
#include <thread>
#include <utility>
#include <vector>

#include "google/protobuf/stubs/common.h"
#include "google/protobuf/testing/file.h"
#include "google/protobuf/testing/file.h"
#include <gtest/gtest.h>
#include "absl/log/absl_check.h"
#include "absl/log/absl_log.h"
#include "absl/status/status.h"
#include "absl/strings/cord.h"
#include "absl/strings/cord_buffer.h"
#include "absl/strings/str_cat.h"
#include "absl/strings/string_view.h"
#include "google/protobuf/io/coded_stream.h"
#include "google/protobuf/io/io_win32.h"
#include "google/protobuf/io/zero_copy_stream_impl.h"
#include "google/protobuf/test_util2.h"

#if HAVE_ZLIB
#include "google/protobuf/io/gzip_stream.h"
#endif


// Must be included last.
#include "google/protobuf/port_def.inc"

namespace google {
namespace protobuf {
namespace io {
namespace {

#ifdef _WIN32
#define pipe(fds) _pipe(fds, 4096, O_BINARY)
// DO NOT include <io.h>, instead create functions in io_win32.{h,cc} and import
// them like we do below.
using google::protobuf::io::win32::access;
using google::protobuf::io::win32::close;
using google::protobuf::io::win32::mkdir;
using google::protobuf::io::win32::open;
#endif

#ifndef O_BINARY
#ifdef _O_BINARY
#define O_BINARY _O_BINARY
#else
#define O_BINARY 0  // If this isn't defined, the platform doesn't need it.
#endif
#endif

class IoTest : public testing::Test {
 protected:
  // Test helpers.

  // Helper to write an array of data to an output stream.
  bool WriteToOutput(ZeroCopyOutputStream* output, const void* data, int size);
  // Helper to read a fixed-length array of data from an input stream.
  int ReadFromInput(ZeroCopyInputStream* input, void* data, int size);
  // Write a string to the output stream.
  void WriteString(ZeroCopyOutputStream* output, const std::string& str);
  // Read a number of bytes equal to the size of the given string and checks
  // that it matches the string.
  void ReadString(ZeroCopyInputStream* input, const std::string& str);
  // Writes some text to the output stream in a particular order.  Returns
  // the number of bytes written, in case the caller needs that to set up an
  // input stream.
  int WriteStuff(ZeroCopyOutputStream* output);
  // Reads text from an input stream and expects it to match what
  // WriteStuff() writes.
  void ReadStuff(ZeroCopyInputStream* input, bool read_eof = true);

  // Similar to WriteStuff, but performs more sophisticated testing.
  int WriteStuffLarge(ZeroCopyOutputStream* output);
  // Reads and tests a stream that should have been written to
  // via WriteStuffLarge().
  void ReadStuffLarge(ZeroCopyInputStream* input);

#if HAVE_ZLIB
  std::string Compress(const std::string& data,
                       const GzipOutputStream::Options& options);
  std::string Uncompress(const std::string& data);
#endif

  static const int kBlockSizes[];
  static const int kBlockSizeCount;
};

const int IoTest::kBlockSizes[] = {-1, 1, 2, 5, 7, 10, 23, 64};
const int IoTest::kBlockSizeCount = ABSL_ARRAYSIZE(IoTest::kBlockSizes);

bool IoTest::WriteToOutput(ZeroCopyOutputStream* output, const void* data,
                           int size) {
  const uint8_t* in = reinterpret_cast<const uint8_t*>(data);
  int in_size = size;

  void* out;
  int out_size;

  while (true) {
    if (!output->Next(&out, &out_size)) {
      return false;
    }
    EXPECT_GT(out_size, 0);

    if (in_size <= out_size) {
      memcpy(out, in, in_size);
      output->BackUp(out_size - in_size);
      return true;
    }

    memcpy(out, in, out_size);
    in += out_size;
    in_size -= out_size;
  }
}

#define MAX_REPEATED_ZEROS 100

int IoTest::ReadFromInput(ZeroCopyInputStream* input, void* data, int size) {
  uint8_t* out = reinterpret_cast<uint8_t*>(data);
  int out_size = size;

  const void* in;
  int in_size = 0;

  int repeated_zeros = 0;

  while (true) {
    if (!input->Next(&in, &in_size)) {
      return size - out_size;
    }
    EXPECT_GT(in_size, -1);
    if (in_size == 0) {
      repeated_zeros++;
    } else {
      repeated_zeros = 0;
    }
    EXPECT_LT(repeated_zeros, MAX_REPEATED_ZEROS);

    if (out_size <= in_size) {
      memcpy(out, in, out_size);
      if (in_size > out_size) {
        input->BackUp(in_size - out_size);
      }
      return size;  // Copied all of it.
    }

    memcpy(out, in, in_size);
    out += in_size;
    out_size -= in_size;
  }
}

void IoTest::WriteString(ZeroCopyOutputStream* output, const std::string& str) {
  EXPECT_TRUE(WriteToOutput(output, str.c_str(), str.size()));
}

void IoTest::ReadString(ZeroCopyInputStream* input, const std::string& str) {
  std::unique_ptr<char[]> buffer(new char[str.size() + 1]);
  buffer[str.size()] = '\0';
  EXPECT_EQ(ReadFromInput(input, buffer.get(), str.size()), str.size());
  EXPECT_STREQ(str.c_str(), buffer.get());
}

int IoTest::WriteStuff(ZeroCopyOutputStream* output) {
  WriteString(output, "Hello world!\n");
  WriteString(output, "Some te");
  WriteString(output, "xt.  Blah blah.");
  WriteString(output, "abcdefg");
  WriteString(output, "01234567890123456789");
  WriteString(output, "foobar");

  EXPECT_EQ(output->ByteCount(), 68);

  int result = output->ByteCount();
  return result;
}

// Reads text from an input stream and expects it to match what WriteStuff()
// writes.
void IoTest::ReadStuff(ZeroCopyInputStream* input, bool read_eof) {
  ReadString(input, "Hello world!\n");
  ReadString(input, "Some text.  ");
  ReadString(input, "Blah ");
  ReadString(input, "blah.");
  ReadString(input, "abcdefg");
  EXPECT_TRUE(input->Skip(20));
  ReadString(input, "foo");
  ReadString(input, "bar");

  EXPECT_EQ(input->ByteCount(), 68);

  if (read_eof) {
    uint8_t byte;
    EXPECT_EQ(ReadFromInput(input, &byte, 1), 0);
  }
}

int IoTest::WriteStuffLarge(ZeroCopyOutputStream* output) {
  WriteString(output, "Hello world!\n");
  WriteString(output, "Some te");
  WriteString(output, "xt.  Blah blah.");
  WriteString(output, std::string(100000, 'x'));  // A very long string
  WriteString(output, std::string(100000, 'y'));  // A very long string
  WriteString(output, "01234567890123456789");

  EXPECT_EQ(output->ByteCount(), 200055);

  int result = output->ByteCount();
  return result;
}

// Reads text from an input stream and expects it to match what WriteStuff()
// writes.
void IoTest::ReadStuffLarge(ZeroCopyInputStream* input) {
  ReadString(input, "Hello world!\nSome text.  ");
  EXPECT_TRUE(input->Skip(5));
  ReadString(input, "blah.");
  EXPECT_TRUE(input->Skip(100000 - 10));
  ReadString(input, std::string(10, 'x') + std::string(100000 - 20000, 'y'));
  EXPECT_TRUE(input->Skip(20000 - 10));
  ReadString(input, "yyyyyyyyyy01234567890123456789");

  EXPECT_EQ(input->ByteCount(), 200055);

  uint8_t byte;
  EXPECT_EQ(ReadFromInput(input, &byte, 1), 0);
}

// ===================================================================

TEST_F(IoTest, ArrayIo) {
  const int kBufferSize = 256;
  uint8_t buffer[kBufferSize];

  for (int i = 0; i < kBlockSizeCount; i++) {
    for (int j = 0; j < kBlockSizeCount; j++) {
      int size;
      {
        ArrayOutputStream output(buffer, kBufferSize, kBlockSizes[i]);
        size = WriteStuff(&output);
      }
      {
        ArrayInputStream input(buffer, size, kBlockSizes[j]);
        ReadStuff(&input);
      }
    }
  }
}

TEST_F(IoTest, TwoSessionWrite) {
  // Test that two concatenated write sessions read correctly

  static const char* strA = "0123456789";
  static const char* strB = "WhirledPeas";
  const int kBufferSize = 2 * 1024;
  uint8_t* buffer = new uint8_t[kBufferSize];
  char* temp_buffer = new char[40];

  for (int i = 0; i < kBlockSizeCount; i++) {
    for (int j = 0; j < kBlockSizeCount; j++) {
      ArrayOutputStream* output =
          new ArrayOutputStream(buffer, kBufferSize, kBlockSizes[i]);
      CodedOutputStream* coded_output = new CodedOutputStream(output);
      coded_output->WriteVarint32(strlen(strA));
      coded_output->WriteRaw(strA, strlen(strA));
      delete coded_output;  // flush
      int64_t pos = output->ByteCount();
      delete output;
      output = new ArrayOutputStream(buffer + pos, kBufferSize - pos,
                                     kBlockSizes[i]);
      coded_output = new CodedOutputStream(output);
      coded_output->WriteVarint32(strlen(strB));
      coded_output->WriteRaw(strB, strlen(strB));
      delete coded_output;  // flush
      int64_t size = pos + output->ByteCount();
      delete output;

      ArrayInputStream* input =
          new ArrayInputStream(buffer, size, kBlockSizes[j]);
      CodedInputStream* coded_input = new CodedInputStream(input);
      uint32_t insize;
      EXPECT_TRUE(coded_input->ReadVarint32(&insize));
      EXPECT_EQ(strlen(strA), insize);
      EXPECT_TRUE(coded_input->ReadRaw(temp_buffer, insize));
      EXPECT_EQ(0, memcmp(temp_buffer, strA, insize));

      EXPECT_TRUE(coded_input->ReadVarint32(&insize));
      EXPECT_EQ(strlen(strB), insize);
      EXPECT_TRUE(coded_input->ReadRaw(temp_buffer, insize));
      EXPECT_EQ(0, memcmp(temp_buffer, strB, insize));

      delete coded_input;
      delete input;
    }
  }

  delete[] temp_buffer;
  delete[] buffer;
}

#if HAVE_ZLIB
TEST_F(IoTest, GzipIo) {
  const int kBufferSize = 2 * 1024;
  uint8* buffer = new uint8[kBufferSize];
  for (int i = 0; i < kBlockSizeCount; i++) {
    for (int j = 0; j < kBlockSizeCount; j++) {
      for (int z = 0; z < kBlockSizeCount; z++) {
        int gzip_buffer_size = kBlockSizes[z];
        int size;
        {
          ArrayOutputStream output(buffer, kBufferSize, kBlockSizes[i]);
          GzipOutputStream::Options options;
          options.format = GzipOutputStream::GZIP;
          if (gzip_buffer_size != -1) {
            options.buffer_size = gzip_buffer_size;
          }
          GzipOutputStream gzout(&output, options);
          WriteStuff(&gzout);
          gzout.Close();
          size = output.ByteCount();
        }
        {
          ArrayInputStream input(buffer, size, kBlockSizes[j]);
          GzipInputStream gzin(&input, GzipInputStream::GZIP, gzip_buffer_size);
          ReadStuff(&gzin);
        }
      }
    }
  }
  delete[] buffer;
}

TEST_F(IoTest, GzipIoWithFlush) {
  const int kBufferSize = 2 * 1024;
  uint8* buffer = new uint8[kBufferSize];
  // We start with i = 4 as we want a block size > 6. With block size <= 6
  // Flush() fills up the entire 2K buffer with flush markers and the test
  // fails. See documentation for Flush() for more detail.
  for (int i = 4; i < kBlockSizeCount; i++) {
    for (int j = 0; j < kBlockSizeCount; j++) {
      for (int z = 0; z < kBlockSizeCount; z++) {
        int gzip_buffer_size = kBlockSizes[z];
        int size;
        {
          ArrayOutputStream output(buffer, kBufferSize, kBlockSizes[i]);
          GzipOutputStream::Options options;
          options.format = GzipOutputStream::GZIP;
          if (gzip_buffer_size != -1) {
            options.buffer_size = gzip_buffer_size;
          }
          GzipOutputStream gzout(&output, options);
          WriteStuff(&gzout);
          EXPECT_TRUE(gzout.Flush());
          gzout.Close();
          size = output.ByteCount();
        }
        {
          ArrayInputStream input(buffer, size, kBlockSizes[j]);
          GzipInputStream gzin(&input, GzipInputStream::GZIP, gzip_buffer_size);
          ReadStuff(&gzin);
        }
      }
    }
  }
  delete[] buffer;
}

TEST_F(IoTest, GzipIoContiguousFlushes) {
  const int kBufferSize = 2 * 1024;
  uint8* buffer = new uint8[kBufferSize];

  int block_size = kBlockSizes[4];
  int gzip_buffer_size = block_size;
  int size;

  ArrayOutputStream output(buffer, kBufferSize, block_size);
  GzipOutputStream::Options options;
  options.format = GzipOutputStream::GZIP;
  if (gzip_buffer_size != -1) {
    options.buffer_size = gzip_buffer_size;
  }
  GzipOutputStream gzout(&output, options);
  WriteStuff(&gzout);
  EXPECT_TRUE(gzout.Flush());
  EXPECT_TRUE(gzout.Flush());
  gzout.Close();
  size = output.ByteCount();

  ArrayInputStream input(buffer, size, block_size);
  GzipInputStream gzin(&input, GzipInputStream::GZIP, gzip_buffer_size);
  ReadStuff(&gzin);

  delete[] buffer;
}

TEST_F(IoTest, GzipIoReadAfterFlush) {
  const int kBufferSize = 2 * 1024;
  uint8* buffer = new uint8[kBufferSize];

  int block_size = kBlockSizes[4];
  int gzip_buffer_size = block_size;
  int size;
  ArrayOutputStream output(buffer, kBufferSize, block_size);
  GzipOutputStream::Options options;
  options.format = GzipOutputStream::GZIP;
  if (gzip_buffer_size != -1) {
    options.buffer_size = gzip_buffer_size;
  }

  GzipOutputStream gzout(&output, options);
  WriteStuff(&gzout);
  EXPECT_TRUE(gzout.Flush());
  size = output.ByteCount();

  ArrayInputStream input(buffer, size, block_size);
  GzipInputStream gzin(&input, GzipInputStream::GZIP, gzip_buffer_size);
  ReadStuff(&gzin);

  gzout.Close();

  delete[] buffer;
}

TEST_F(IoTest, ZlibIo) {
  const int kBufferSize = 2 * 1024;
  uint8* buffer = new uint8[kBufferSize];
  for (int i = 0; i < kBlockSizeCount; i++) {
    for (int j = 0; j < kBlockSizeCount; j++) {
      for (int z = 0; z < kBlockSizeCount; z++) {
        int gzip_buffer_size = kBlockSizes[z];
        int size;
        {
          ArrayOutputStream output(buffer, kBufferSize, kBlockSizes[i]);
          GzipOutputStream::Options options;
          options.format = GzipOutputStream::ZLIB;
          if (gzip_buffer_size != -1) {
            options.buffer_size = gzip_buffer_size;
          }
          GzipOutputStream gzout(&output, options);
          WriteStuff(&gzout);
          gzout.Close();
          size = output.ByteCount();
        }
        {
          ArrayInputStream input(buffer, size, kBlockSizes[j]);
          GzipInputStream gzin(&input, GzipInputStream::ZLIB, gzip_buffer_size);
          ReadStuff(&gzin);
        }
      }
    }
  }
  delete[] buffer;
}

TEST_F(IoTest, ZlibIoInputAutodetect) {
  const int kBufferSize = 2 * 1024;
  uint8* buffer = new uint8[kBufferSize];
  int size;
  {
    ArrayOutputStream output(buffer, kBufferSize);
    GzipOutputStream::Options options;
    options.format = GzipOutputStream::ZLIB;
    GzipOutputStream gzout(&output, options);
    WriteStuff(&gzout);
    gzout.Close();
    size = output.ByteCount();
  }
  {
    ArrayInputStream input(buffer, size);
    GzipInputStream gzin(&input, GzipInputStream::AUTO);
    ReadStuff(&gzin);
  }
  {
    ArrayOutputStream output(buffer, kBufferSize);
    GzipOutputStream::Options options;
    options.format = GzipOutputStream::GZIP;
    GzipOutputStream gzout(&output, options);
    WriteStuff(&gzout);
    gzout.Close();
    size = output.ByteCount();
  }
  {
    ArrayInputStream input(buffer, size);
    GzipInputStream gzin(&input, GzipInputStream::AUTO);
    ReadStuff(&gzin);
  }
  delete[] buffer;
}

std::string IoTest::Compress(const std::string& data,
                             const GzipOutputStream::Options& options) {
  std::string result;
  {
    StringOutputStream output(&result);
    GzipOutputStream gzout(&output, options);
    WriteToOutput(&gzout, data.data(), data.size());
  }
  return result;
}

std::string IoTest::Uncompress(const std::string& data) {
  std::string result;
  {
    ArrayInputStream input(data.data(), data.size());
    GzipInputStream gzin(&input);
    const void* buffer;
    int size;
    while (gzin.Next(&buffer, &size)) {
      result.append(reinterpret_cast<const char*>(buffer), size);
    }
  }
  return result;
}

TEST_F(IoTest, CompressionOptions) {
  // Some ad-hoc testing of compression options.

  std::string golden_filename =
      TestUtil::GetTestDataPath("google/protobuf/testdata/golden_message");
  std::string golden;
  ABSL_CHECK_OK(File::GetContents(golden_filename, &golden, true));

  GzipOutputStream::Options options;
  std::string gzip_compressed = Compress(golden, options);

  options.compression_level = 0;
  std::string not_compressed = Compress(golden, options);

  // Try zlib compression for fun.
  options = GzipOutputStream::Options();
  options.format = GzipOutputStream::ZLIB;
  std::string zlib_compressed = Compress(golden, options);

  // Uncompressed should be bigger than the original since it should have some
  // sort of header.
  EXPECT_GT(not_compressed.size(), golden.size());

  // Higher compression levels should result in smaller sizes.
  EXPECT_LT(zlib_compressed.size(), not_compressed.size());

  // ZLIB format should differ from GZIP format.
  EXPECT_TRUE(zlib_compressed != gzip_compressed);

  // Everything should decompress correctly.
  EXPECT_TRUE(Uncompress(not_compressed) == golden);
  EXPECT_TRUE(Uncompress(gzip_compressed) == golden);
  EXPECT_TRUE(Uncompress(zlib_compressed) == golden);
}

TEST_F(IoTest, TwoSessionWriteGzip) {
  // Test that two concatenated gzip streams can be read correctly

  static const char* strA = "0123456789";
  static const char* strB = "QuickBrownFox";
  const int kBufferSize = 2 * 1024;
  uint8* buffer = new uint8[kBufferSize];
  char* temp_buffer = new char[40];

  for (int i = 0; i < kBlockSizeCount; i++) {
    for (int j = 0; j < kBlockSizeCount; j++) {
      ArrayOutputStream* output =
          new ArrayOutputStream(buffer, kBufferSize, kBlockSizes[i]);
      GzipOutputStream* gzout = new GzipOutputStream(output);
      CodedOutputStream* coded_output = new CodedOutputStream(gzout);
      int32 outlen = strlen(strA) + 1;
      coded_output->WriteVarint32(outlen);
      coded_output->WriteRaw(strA, outlen);
      delete coded_output;  // flush
      delete gzout;         // flush
      int64 pos = output->ByteCount();
      delete output;
      output = new ArrayOutputStream(buffer + pos, kBufferSize - pos,
                                     kBlockSizes[i]);
      gzout = new GzipOutputStream(output);
      coded_output = new CodedOutputStream(gzout);
      outlen = strlen(strB) + 1;
      coded_output->WriteVarint32(outlen);
      coded_output->WriteRaw(strB, outlen);
      delete coded_output;  // flush
      delete gzout;         // flush
      int64 size = pos + output->ByteCount();
      delete output;

      ArrayInputStream* input =
          new ArrayInputStream(buffer, size, kBlockSizes[j]);
      GzipInputStream* gzin = new GzipInputStream(input);
      CodedInputStream* coded_input = new CodedInputStream(gzin);
      uint32 insize;
      EXPECT_TRUE(coded_input->ReadVarint32(&insize));
      EXPECT_EQ(strlen(strA) + 1, insize);
      EXPECT_TRUE(coded_input->ReadRaw(temp_buffer, insize));
      EXPECT_EQ(0, memcmp(temp_buffer, strA, insize))
          << "strA=" << strA << " in=" << temp_buffer;

      EXPECT_TRUE(coded_input->ReadVarint32(&insize));
      EXPECT_EQ(strlen(strB) + 1, insize);
      EXPECT_TRUE(coded_input->ReadRaw(temp_buffer, insize));
      EXPECT_EQ(0, memcmp(temp_buffer, strB, insize))
          << " out_block_size=" << kBlockSizes[i]
          << " in_block_size=" << kBlockSizes[j] << " pos=" << pos
          << " size=" << size << " strB=" << strB << " in=" << temp_buffer;

      delete coded_input;
      delete gzin;
      delete input;
    }
  }

  delete[] temp_buffer;
  delete[] buffer;
}

TEST_F(IoTest, GzipInputByteCountAfterClosed) {
  std::string golden = "abcdefghijklmnopqrstuvwxyz";
  std::string compressed = Compress(golden, GzipOutputStream::Options());

  for (int i = 0; i < kBlockSizeCount; i++) {
    ArrayInputStream arr_input(compressed.data(), compressed.size(),
                               kBlockSizes[i]);
    GzipInputStream gz_input(&arr_input);
    const void* buffer;
    int size;
    while (gz_input.Next(&buffer, &size)) {
      EXPECT_LE(gz_input.ByteCount(), golden.size());
    }
    EXPECT_EQ(golden.size(), gz_input.ByteCount());
  }
}

TEST_F(IoTest, GzipInputByteCountAfterClosedConcatenatedStreams) {
  std::string golden1 = "abcdefghijklmnopqrstuvwxyz";
  std::string golden2 = "the quick brown fox jumps over the lazy dog";
  const size_t total_size = golden1.size() + golden2.size();
  std::string compressed = Compress(golden1, GzipOutputStream::Options()) +
                           Compress(golden2, GzipOutputStream::Options());

  for (int i = 0; i < kBlockSizeCount; i++) {
    ArrayInputStream arr_input(compressed.data(), compressed.size(),
                               kBlockSizes[i]);
    GzipInputStream gz_input(&arr_input);
    const void* buffer;
    int size;
    while (gz_input.Next(&buffer, &size)) {
      EXPECT_LE(gz_input.ByteCount(), total_size);
    }
    EXPECT_EQ(total_size, gz_input.ByteCount());
  }
}
#endif

// There is no string input, only string output.  Also, it doesn't support
// explicit block sizes.  So, we'll only run one test and we'll use
// ArrayInput to read back the results.
TEST_F(IoTest, StringIo) {
  std::string str;
  {
    StringOutputStream output(&str);
    WriteStuff(&output);
  }
  {
    ArrayInputStream input(str.data(), str.size());
    ReadStuff(&input);
  }
}


TEST(DefaultReadCordTest, ReadSmallCord) {
  std::string source = "abcdefghijk";
  ArrayInputStream input(source.data(), source.size());

  absl::Cord dest;
  EXPECT_TRUE(input.Skip(1));
  EXPECT_TRUE(input.ReadCord(&dest, source.size() - 2));

  EXPECT_EQ(dest, "bcdefghij");
}

TEST(DefaultReadCordTest, ReadSmallCordAfterBackUp) {
  std::string source = "abcdefghijk";
  ArrayInputStream input(source.data(), source.size());

  absl::Cord dest;
  const void* buffer;
  int size;
  EXPECT_TRUE(input.Next(&buffer, &size));
  input.BackUp(size - 1);

  EXPECT_TRUE(input.ReadCord(&dest, source.size() - 2));

  EXPECT_EQ(dest, "bcdefghij");
}

TEST(DefaultReadCordTest, ReadLargeCord) {
  std::string source = "abcdefghijk";
  for (int i = 0; i < 1024; i++) {
    source.append("abcdefghijk");
  }

  absl::Cord dest;
  ArrayInputStream input(source.data(), source.size());
  EXPECT_TRUE(input.Skip(1));
  EXPECT_TRUE(input.ReadCord(&dest, source.size() - 2));

  absl::Cord expected(source);
  expected.RemovePrefix(1);
  expected.RemoveSuffix(1);

  EXPECT_EQ(expected, dest);
}

TEST(DefaultReadCordTest, ReadLargeCordAfterBackup) {
  std::string source = "abcdefghijk";
  for (int i = 0; i < 1024; i++) {
    source.append("abcdefghijk");
  }

  absl::Cord dest;
  ArrayInputStream input(source.data(), source.size());

  const void* buffer;
  int size;
  EXPECT_TRUE(input.Next(&buffer, &size));
  input.BackUp(size - 1);

  EXPECT_TRUE(input.ReadCord(&dest, source.size() - 2));

  absl::Cord expected(source);
  expected.RemovePrefix(1);
  expected.RemoveSuffix(1);

  EXPECT_EQ(expected, dest);

  EXPECT_TRUE(input.Next(&buffer, &size));
  EXPECT_EQ("k", std::string(reinterpret_cast<const char*>(buffer), size));
}

TEST(DefaultReadCordTest, ReadCordEof) {
  std::string source = "abcdefghijk";

  absl::Cord dest;
  ArrayInputStream input(source.data(), source.size());
  input.Skip(1);
  EXPECT_FALSE(input.ReadCord(&dest, source.size()));

  absl::Cord expected(source);
  expected.RemovePrefix(1);
  EXPECT_EQ(expected, dest);
}

TEST(DefaultWriteCordTest, WriteEmptyCordToArray) {
  absl::Cord source;
  std::string buffer = "abc";
  ArrayOutputStream output(&buffer[0], static_cast<int>(buffer.length()));
  EXPECT_TRUE(output.WriteCord(source));
  EXPECT_EQ(output.ByteCount(), source.size());
  EXPECT_EQ(buffer, "abc");
}

TEST(DefaultWriteCordTest, WriteSmallCord) {
  absl::Cord source("foo bar");

  std::string buffer(source.size(), 'z');
  ArrayOutputStream output(&buffer[0], static_cast<int>(buffer.length()));
  EXPECT_TRUE(output.WriteCord(source));
  EXPECT_EQ(output.ByteCount(), source.size());
  EXPECT_EQ(buffer, source);
}

TEST(DefaultWriteCordTest, WriteLargeCord) {
  absl::Cord source;
  for (int i = 0; i < 1024; i++) {
    source.Append("foo bar");
  }
  // Verify that we created a fragmented cord.
  ASSERT_GT(std::distance(source.chunk_begin(), source.chunk_end()), 1);

  std::string buffer(source.size(), 'z');
  ArrayOutputStream output(&buffer[0], static_cast<int>(buffer.length()));
  EXPECT_TRUE(output.WriteCord(source));
  EXPECT_EQ(output.ByteCount(), source.size());
  EXPECT_EQ(buffer, source);
}

TEST(DefaultWriteCordTest, WriteTooLargeCord) {
  absl::Cord source;
  for (int i = 0; i < 1024; i++) {
    source.Append("foo bar");
  }

  std::string buffer(source.size() - 1, 'z');
  ArrayOutputStream output(&buffer[0], static_cast<int>(buffer.length()));
  EXPECT_FALSE(output.WriteCord(source));
  EXPECT_EQ(output.ByteCount(), buffer.size());
  EXPECT_EQ(buffer, source.Subcord(0, output.ByteCount()));
}

TEST(CordInputStreamTest, SkipToEnd) {
  absl::Cord source(std::string(10000, 'z'));
  CordInputStream stream(&source);
  EXPECT_TRUE(stream.Skip(10000));
  EXPECT_EQ(stream.ByteCount(), 10000);
}

TEST_F(IoTest, CordIo) {
  CordOutputStream output;
  int size = WriteStuff(&output);
  absl::Cord cord = output.Consume();
  EXPECT_EQ(size, cord.size());

  {
    CordInputStream input(&cord);
    ReadStuff(&input);
  }
}

template <typename Container>
absl::Cord MakeFragmentedCord(const Container& c) {
  absl::Cord result;
  for (const auto& s : c) {
    absl::string_view sv(s);
    auto buffer = absl::CordBuffer::CreateWithDefaultLimit(sv.size());
    absl::Span<char> out = buffer.available_up_to(sv.size());
    memcpy(out.data(), sv.data(), out.size());
    buffer.SetLength(out.size());
    result.Append(std::move(buffer));
  }
  return result;
}

// Test that we can read correctly from a fragmented Cord.
TEST_F(IoTest, FragmentedCordInput) {
  std::string str;
  {
    StringOutputStream output(&str);
    WriteStuff(&output);
  }

  for (int i = 0; i < kBlockSizeCount; i++) {
    int block_size = kBlockSizes[i];
    if (block_size < 0) {
      // Skip the -1 case.
      continue;
    }
    absl::string_view str_piece = str;

    // Create a fragmented cord by splitting the input into many cord
    // functions.
    std::vector<absl::string_view> fragments;
    while (!str_piece.empty()) {
      size_t n = std::min<size_t>(str_piece.size(), block_size);
      fragments.push_back(str_piece.substr(0, n));
      str_piece.remove_prefix(n);
    }
    absl::Cord fragmented_cord = MakeFragmentedCord(fragments);

    CordInputStream input(&fragmented_cord);
    ReadStuff(&input);
  }
}

TEST_F(IoTest, ReadSmallCord) {
  absl::Cord source;
  source.Append("foo bar");

  absl::Cord dest;
  CordInputStream input(&source);
  EXPECT_TRUE(input.Skip(1));
  EXPECT_TRUE(input.ReadCord(&dest, source.size() - 2));

  EXPECT_EQ(absl::Cord("oo ba"), dest);
}

TEST_F(IoTest, ReadSmallCordAfterBackUp) {
  absl::Cord source;
  source.Append("foo bar");

  absl::Cord dest;
  CordInputStream input(&source);

  const void* buffer;
  int size;
  EXPECT_TRUE(input.Next(&buffer, &size));
  input.BackUp(size - 1);

  EXPECT_TRUE(input.ReadCord(&dest, source.size() - 2));

  EXPECT_EQ(absl::Cord("oo ba"), dest);
}

TEST_F(IoTest, ReadLargeCord) {
  absl::Cord source;
  for (int i = 0; i < 1024; i++) {
    source.Append("foo bar");
  }

  absl::Cord dest;
  CordInputStream input(&source);
  EXPECT_TRUE(input.Skip(1));
  EXPECT_TRUE(input.ReadCord(&dest, source.size() - 2));

  absl::Cord expected = source;
  expected.RemovePrefix(1);
  expected.RemoveSuffix(1);

  EXPECT_EQ(expected, dest);
}

TEST_F(IoTest, ReadLargeCordAfterBackUp) {
  absl::Cord source;
  for (int i = 0; i < 1024; i++) {
    source.Append("foo bar");
  }

  absl::Cord dest;
  CordInputStream input(&source);

  const void* buffer;
  int size;
  EXPECT_TRUE(input.Next(&buffer, &size));
  input.BackUp(size - 1);

  EXPECT_TRUE(input.ReadCord(&dest, source.size() - 2));

  absl::Cord expected = source;
  expected.RemovePrefix(1);
  expected.RemoveSuffix(1);

  EXPECT_EQ(expected, dest);

  EXPECT_TRUE(input.Next(&buffer, &size));
  EXPECT_EQ("r", std::string(reinterpret_cast<const char*>(buffer), size));
}

TEST_F(IoTest, ReadCordEof) {
  absl::Cord source;
  source.Append("foo bar");

  absl::Cord dest;
  CordInputStream input(&source);
  input.Skip(1);
  EXPECT_FALSE(input.ReadCord(&dest, source.size()));

  absl::Cord expected = source;
  expected.RemovePrefix(1);
  EXPECT_EQ(expected, dest);
}

TEST(CordOutputStreamTest, Empty) {
  CordOutputStream output;
  EXPECT_TRUE(output.Consume().empty());
}

TEST(CordOutputStreamTest, ConsumesCordClearingState) {
  CordOutputStream output(absl::Cord("abcdef"));
  EXPECT_EQ(output.Consume(), "abcdef");
  EXPECT_TRUE(output.Consume().empty());
}

TEST(CordOutputStreamTest, DonateEmptyCordBuffer) {
  absl::CordBuffer buffer = absl::CordBuffer::CreateWithDefaultLimit(500);
  absl::Span<char> available = buffer.available();
  void* available_data = available.data();
  CordOutputStream output(std::move(buffer));
  void* data;
  int size;
  EXPECT_TRUE(output.Next(&data, &size));
  EXPECT_EQ(data, available_data);
  EXPECT_EQ(size, static_cast<int>(available.size()));
  memset(data, 'a', static_cast<size_t>(size));

  absl::Cord cord = output.Consume();
  ASSERT_TRUE(cord.TryFlat());
  absl::string_view flat = *cord.TryFlat();
  EXPECT_EQ(flat, std::string(static_cast<size_t>(size), 'a'));
  EXPECT_EQ(flat.data(), available_data);
}

TEST(CordOutputStreamTest, DonatePartialCordBuffer) {
  absl::CordBuffer buffer = absl::CordBuffer::CreateWithDefaultLimit(500);
  absl::Span<char> available = buffer.available();
  memset(available.data(), 'a', 100);
  buffer.IncreaseLengthBy(100);
  void* available_data = available.data();
  CordOutputStream output(std::move(buffer));

  absl::Cord cord = output.Consume();
  ASSERT_TRUE(cord.TryFlat());
  absl::string_view flat = *cord.TryFlat();
  EXPECT_EQ(flat, std::string(100, 'a'));
  EXPECT_EQ(flat.data(), available_data);
}

TEST(CordOutputStreamTest, DonatePartialCordBufferAndUseExtraCapacity) {
  absl::CordBuffer buffer = absl::CordBuffer::CreateWithDefaultLimit(500);
  absl::Span<char> available = buffer.available();
  memset(available.data(), 'a', 100);
  buffer.IncreaseLengthBy(100);
  void* available_data = available.data();
  void* next_available_data = available.data() + 100;
  CordOutputStream output(std::move(buffer));
  void* data;
  int size;
  EXPECT_TRUE(output.Next(&data, &size));
  EXPECT_EQ(data, next_available_data);
  EXPECT_EQ(size, static_cast<int>(available.size() - 100));
  memset(data, 'b', static_cast<size_t>(size));

  absl::Cord cord = output.Consume();
  ASSERT_TRUE(cord.TryFlat());
  absl::string_view flat = *cord.TryFlat();
  EXPECT_EQ(flat, std::string(100, 'a') +
                      std::string(static_cast<size_t>(size), 'b'));
  EXPECT_EQ(flat.data(), available_data);
}

TEST(CordOutputStreamTest, DonateCordAndPartialCordBufferAndUseExtraCapacity) {
  absl::Cord cord(std::string(400, 'a'));
  absl::CordBuffer buffer = absl::CordBuffer::CreateWithDefaultLimit(500);
  absl::Span<char> available = buffer.available();
  memset(available.data(), 'b', 100);
  buffer.IncreaseLengthBy(100);
  void* next_available_data = available.data() + 100;
  CordOutputStream output(std::move(cord), std::move(buffer));
  void* data;
  int size;
  EXPECT_TRUE(output.Next(&data, &size));
  EXPECT_EQ(data, next_available_data);
  EXPECT_EQ(size, static_cast<int>(available.size() - 100));
  memset(data, 'c', static_cast<size_t>(size));

  cord = output.Consume();
  EXPECT_FALSE(cord.TryFlat());
  EXPECT_EQ(cord, std::string(400, 'a') + std::string(100, 'b') +
                      std::string(static_cast<size_t>(size), 'c'));
}

TEST(CordOutputStreamTest, DonateFullCordBuffer) {
  absl::CordBuffer buffer = absl::CordBuffer::CreateWithDefaultLimit(500);
  absl::Span<char> available = buffer.available();
  memset(available.data(), 'a', available.size());
  buffer.IncreaseLengthBy(available.size());
  CordOutputStream output(std::move(buffer));
  void* data;
  int size;
  EXPECT_TRUE(output.Next(&data, &size));
  memset(data, 'b', static_cast<size_t>(size));

  absl::Cord cord = output.Consume();
  EXPECT_FALSE(cord.TryFlat());
  EXPECT_EQ(cord, std::string(available.size(), 'a') +
                      std::string(static_cast<size_t>(size), 'b'));
}

TEST(CordOutputStreamTest, DonateFullCordBufferAndCord) {
  absl::Cord cord(std::string(400, 'a'));
  absl::CordBuffer buffer = absl::CordBuffer::CreateWithDefaultLimit(500);
  absl::Span<char> available = buffer.available();
  memset(available.data(), 'b', available.size());
  buffer.IncreaseLengthBy(available.size());
  CordOutputStream output(std::move(cord), std::move(buffer));
  void* data;
  int size;
  EXPECT_TRUE(output.Next(&data, &size));
  memset(data, 'c', static_cast<size_t>(size));

  cord = output.Consume();
  EXPECT_FALSE(cord.TryFlat());
  EXPECT_EQ(cord, std::string(400, 'a') +
                      std::string(available.size(), 'b') +
                      std::string(static_cast<size_t>(size), 'c'));
}

TEST(CordOutputStreamTest, DonateFullCordBufferAndBackup) {
  absl::CordBuffer buffer = absl::CordBuffer::CreateWithDefaultLimit(500);
  absl::Span<char> available = buffer.available();
  memset(available.data(), 'a', available.size());
  buffer.IncreaseLengthBy(available.size());

  // We back up by 100 before calling Next()
  void* available_data = available.data();
  void* next_available_data = available.data() + available.size() - 100;
  CordOutputStream output(std::move(buffer));
  output.BackUp(100);

  void* data;
  int size;
  EXPECT_TRUE(output.Next(&data, &size));
  EXPECT_EQ(data, next_available_data);
  EXPECT_EQ(size, 100);
  memset(data, 'b', 100);

  absl::Cord cord = output.Consume();
  ASSERT_TRUE(cord.TryFlat());
  absl::string_view flat = *cord.TryFlat();
  EXPECT_EQ(flat,
            std::string(available.size() - 100, 'a') + std::string(100, 'b'));
  EXPECT_EQ(flat.data(), available_data);
}

TEST(CordOutputStreamTest, DonateCordAndFullCordBufferAndBackup) {
  absl::Cord cord(std::string(400, 'a'));
  absl::CordBuffer buffer = absl::CordBuffer::CreateWithDefaultLimit(500);
  absl::Span<char> available = buffer.available();
  memset(available.data(), 'b', available.size());
  buffer.IncreaseLengthBy(available.size());

  // We back up by 100 before calling Next()
  void* next_available_data = available.data() + available.size() - 100;
  CordOutputStream output(std::move(cord), std::move(buffer));
  output.BackUp(100);

  void* data;
  int size;
  EXPECT_TRUE(output.Next(&data, &size));
  EXPECT_EQ(data, next_available_data);
  EXPECT_EQ(size, 100);
  memset(data, 'c', 100);

  cord = output.Consume();
  EXPECT_FALSE(cord.TryFlat());
  EXPECT_EQ(cord, std::string(400, 'a') +
                      std::string(available.size() - 100, 'b') +
                      std::string(100, 'c'));
}

TEST(CordOutputStreamTest, ProperHintCreatesSingleFlatCord) {
  CordOutputStream output(2000);
  void* data;
  int size;
  ASSERT_TRUE(output.Next(&data, &size));
  ASSERT_EQ(size, 2000);
  memset(data, 'a', 2000);

  absl::Cord cord = output.Consume();
  ASSERT_TRUE(cord.TryFlat());
  absl::string_view flat = *cord.TryFlat();
  EXPECT_EQ(flat, std::string(2000, 'a'));
}

TEST(CordOutputStreamTest, SizeHintDicatesTotalSize) {
  absl::Cord cord(std::string(500, 'a'));
  CordOutputStream output(std::move(cord), 2000);
  void* data;
  int size;

  int remaining = 1500;
  while (remaining > 0) {
    ASSERT_TRUE(output.Next(&data, &size));
    ASSERT_LE(size, remaining);
    memset(data, 'b', static_cast<size_t>(size));
    remaining -= size;
  }
  ASSERT_EQ(remaining, 0);

  cord = output.Consume();
  EXPECT_EQ(cord, absl::StrCat(std::string(500, 'a'), std::string(1500, 'b')));
}

TEST(CordOutputStreamTest, BackUpReusesPartialBuffer) {
  CordOutputStream output(2000);
  void* data;
  int size;

  ASSERT_TRUE(output.Next(&data, &size));
  ASSERT_EQ(size, 2000);
  memset(data, '1', 100);
  output.BackUp(1900);

  ASSERT_TRUE(output.Next(&data, &size));
  ASSERT_EQ(size, 1900);
  memset(data, '2', 200);
  output.BackUp(1700);

  ASSERT_TRUE(output.Next(&data, &size));
  ASSERT_EQ(size, 1700);
  memset(data, '3', 400);
  output.BackUp(1300);

  ASSERT_TRUE(output.Next(&data, &size));
  ASSERT_EQ(size, 1300);
  memset(data, '4', 1300);

  absl::Cord cord = output.Consume();
  ASSERT_TRUE(cord.TryFlat());
  absl::string_view flat = *cord.TryFlat();
  EXPECT_EQ(flat, absl::StrCat(std::string(100, '1'), std::string(200, '2'),
                               std::string(400, '3'), std::string(1300, '4')));
}

TEST(CordOutputStreamTest, UsesPrivateCapacityInDonatedCord) {
  absl::Cord cord;
  absl::CordBuffer buffer = absl::CordBuffer::CreateWithDefaultLimit(2000);
  memset(buffer.data(), 'a', 500);
  buffer.SetLength(500);
  cord.Append(std::move(buffer));

  CordOutputStream output(std::move(cord), 2000);
  void* data;
  int size;

  ASSERT_TRUE(output.Next(&data, &size));
  ASSERT_EQ(size, 1500);
  memset(data, 'b', 1500);

  cord = output.Consume();
  ASSERT_TRUE(cord.TryFlat());
  absl::string_view flat = *cord.TryFlat();
  EXPECT_EQ(flat, absl::StrCat(std::string(500, 'a'), std::string(1500, 'b')));
}

TEST(CordOutputStreamTest, UsesPrivateCapacityInAppendedCord) {
  absl::Cord cord;
  absl::CordBuffer buffer = absl::CordBuffer::CreateWithDefaultLimit(2000);
  memset(buffer.data(), 'a', 500);
  buffer.SetLength(500);
  cord.Append(std::move(buffer));

  CordOutputStream output(2000);
  void* data;
  int size;

  // Add cord. Clearing it makes it privately owned by 'output' as it's non
  // trivial size guarantees it is ref counted, not deep copied.
  output.WriteCord(cord);
  cord.Clear();

  ASSERT_TRUE(output.Next(&data, &size));
  ASSERT_EQ(size, 1500);
  memset(data, 'b', 1500);

  cord = output.Consume();
  ASSERT_TRUE(cord.TryFlat());
  absl::string_view flat = *cord.TryFlat();
  EXPECT_EQ(flat, absl::StrCat(std::string(500, 'a'), std::string(1500, 'b')));
}

TEST(CordOutputStreamTest, CapsSizeAtHintButUsesCapacityBeyondHint) {
  // This tests verifies that when we provide a hint of 'x' bytes, that the
  // returned size from Next() will be capped at 'size_hint', but that if we
  // exceed size_hint, it will use the capacity in any internal buffer beyond
  // the size hint. We test this by providing a hint that is too large to be
  // inlined, but so small that we have a guarantee it's smaller than the
  // minimum flat size so we will have a 'capped' larger buffer as state.
  size_t size_hint = sizeof(absl::Cord) + 1;
  CordOutputStream output(size_hint);
  void* data;
  int size;

  ASSERT_TRUE(output.Next(&data, &size));
  ASSERT_EQ(size, size_hint);
  memset(data, 'a', static_cast<size_t>(size));

  ASSERT_TRUE(output.Next(&data, &size));
  memset(data, 'b', static_cast<size_t>(size));

  // We should have received the same buffer on each Next() call
  absl::Cord cord = output.Consume();
  ASSERT_TRUE(cord.TryFlat());
  absl::string_view flat = *cord.TryFlat();
  EXPECT_EQ(flat, absl::StrCat(std::string(size_hint, 'a'),
                               std::string(static_cast<size_t>(size), 'b')));
}

TEST(CordOutputStreamTest, SizeDoublesWithoutHint) {
  CordOutputStream output;
  void* data;
  int size;

  // Whitebox: we are guaranteed at least 128 bytes initially. We also assume
  // that the maximum size is roughly 4KiB - overhead without being precise.
  int min_size = 128;
  const int max_size = 4000;
  ASSERT_TRUE(output.Next(&data, &size));
  memset(data, 0, static_cast<size_t>(size));
  ASSERT_GE(size, min_size);

  for (int i = 0; i < 6; ++i) {
    ASSERT_TRUE(output.Next(&data, &size));
    memset(data, 0, static_cast<size_t>(size));
    ASSERT_GE(size, min_size);
    min_size = (std::min)(min_size * 2, max_size);
  }
}

TEST_F(IoTest, WriteSmallCord) {
  absl::Cord source;
  source.Append("foo bar");

  CordOutputStream output(absl::Cord("existing:"));
  EXPECT_TRUE(output.WriteCord(source));
  absl::Cord cord = output.Consume();
  EXPECT_EQ(absl::Cord("existing:foo bar"), cord);
}

TEST_F(IoTest, WriteLargeCord) {
  absl::Cord source;
  for (int i = 0; i < 1024; i++) {
    source.Append("foo bar");
  }

  CordOutputStream output(absl::Cord("existing:"));
  EXPECT_TRUE(output.WriteCord(source));
  absl::Cord cord = output.Consume();

  absl::Cord expected = source;
  expected.Prepend("existing:");
  EXPECT_EQ(expected, cord);
}

// Test that large size hints lead to large block sizes.
TEST_F(IoTest, CordOutputSizeHint) {
  CordOutputStream output1;
  CordOutputStream output2(12345);

  void* data1;
  void* data2;
  int size1, size2;
  ASSERT_TRUE(output1.Next(&data1, &size1));
  ASSERT_TRUE(output2.Next(&data2, &size2));

  // Prevent 'unflushed output' debug checks and warnings
  output1.BackUp(size1);
  output2.BackUp(size2);

  EXPECT_GT(size2, size1);

  // Prevent any warnings on unused or unflushed data
  output1.Consume();
  output2.Consume();
}

// Test that when we use a size hint, we get a buffer boundary exactly on that
// byte.
TEST_F(IoTest, CordOutputBufferEndsAtSizeHint) {
  static const int kSizeHint = 12345;

  CordOutputStream output(kSizeHint);

  void* data;
  int size;
  int total_read = 0;

  while (total_read < kSizeHint) {
    ASSERT_TRUE(output.Next(&data, &size));
    memset(data, 0, static_cast<size_t>(size));  // Avoid uninitialized data UB
    total_read += size;
  }

  EXPECT_EQ(kSizeHint, total_read);

  // We should be able to keep going past the size hint.
  ASSERT_TRUE(output.Next(&data, &size));
  EXPECT_GT(size, 0);

  // Prevent any warnings on unused or unflushed data
  output.Consume();
}


// To test files, we create a temporary file, write, read, truncate, repeat.
TEST_F(IoTest, FileIo) {
  std::string filename =
      absl::StrCat(::testing::TempDir(), "/zero_copy_stream_test_file");

  for (int i = 0; i < kBlockSizeCount; i++) {
    for (int j = 0; j < kBlockSizeCount; j++) {
      // Make a temporary file.
      int file =
          open(filename.c_str(), O_RDWR | O_CREAT | O_TRUNC | O_BINARY, 0777);
      ASSERT_GE(file, 0);

      {
        FileOutputStream output(file, kBlockSizes[i]);
        WriteStuff(&output);
        EXPECT_EQ(0, output.GetErrno());
      }

      // Rewind.
      ASSERT_NE(lseek(file, 0, SEEK_SET), (off_t)-1);

      {
        FileInputStream input(file, kBlockSizes[j]);
        ReadStuff(&input);
        EXPECT_EQ(0, input.GetErrno());
      }

      close(file);
    }
  }
}

#ifndef _WIN32
// This tests the FileInputStream with a non blocking file. It opens a pipe in
// non blocking mode, then starts reading it. The writing thread starts writing
// 100ms after that.
TEST_F(IoTest, NonBlockingFileIo) {
  for (int i = 0; i < kBlockSizeCount; i++) {
    for (int j = 0; j < kBlockSizeCount; j++) {
      int fd[2];
      // On Linux we could use pipe2 to make the pipe non-blocking in one step,
      // but we instead use pipe and fcntl because pipe2 is not available on
      // Mac OS.
      ASSERT_EQ(pipe(fd), 0);
      ASSERT_EQ(fcntl(fd[0], F_SETFL, O_NONBLOCK), 0);
      ASSERT_EQ(fcntl(fd[1], F_SETFL, O_NONBLOCK), 0);

      std::mutex go_write;
      go_write.lock();

      bool done_reading = false;

      std::thread write_thread([this, fd, &go_write, i]() {
        go_write.lock();
        go_write.unlock();
        FileOutputStream output(fd[1], kBlockSizes[i]);
        WriteStuff(&output);
        EXPECT_EQ(0, output.GetErrno());
      });

      std::thread read_thread([this, fd, &done_reading, j]() {
        FileInputStream input(fd[0], kBlockSizes[j]);
        ReadStuff(&input, false /* read_eof */);
        done_reading = true;
        close(fd[0]);
        close(fd[1]);
        EXPECT_EQ(0, input.GetErrno());
      });

      // Sleeping is not necessary but makes the next expectation relevant: the
      // reading thread waits for the data to be available before returning.
      std::this_thread::sleep_for(std::chrono::milliseconds(100));
      EXPECT_FALSE(done_reading);
      go_write.unlock();
      write_thread.join();
      read_thread.join();
      EXPECT_TRUE(done_reading);
    }
  }
}

TEST_F(IoTest, BlockingFileIoWithTimeout) {
  int fd[2];

  for (int i = 0; i < kBlockSizeCount; i++) {
    ASSERT_EQ(socketpair(AF_UNIX, SOCK_STREAM, 0, fd), 0);
    struct timeval tv {
      .tv_sec = 0, .tv_usec = 5000
    };
    ASSERT_EQ(setsockopt(fd[0], SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv)), 0);
    FileInputStream input(fd[0], kBlockSizes[i]);
    uint8_t byte;
    EXPECT_EQ(ReadFromInput(&input, &byte, 1), 0);
    EXPECT_EQ(EAGAIN, input.GetErrno());
  }
}
#endif

#if HAVE_ZLIB
TEST_F(IoTest, GzipFileIo) {
  std::string filename =
      absl::StrCat(::testing::TempDir(), "/zero_copy_stream_test_file");

  for (int i = 0; i < kBlockSizeCount; i++) {
    for (int j = 0; j < kBlockSizeCount; j++) {
      // Make a temporary file.
      int file =
          open(filename.c_str(), O_RDWR | O_CREAT | O_TRUNC | O_BINARY, 0777);
      ASSERT_GE(file, 0);
      {
        FileOutputStream output(file, kBlockSizes[i]);
        GzipOutputStream gzout(&output);
        WriteStuffLarge(&gzout);
        gzout.Close();
        output.Flush();
        EXPECT_EQ(0, output.GetErrno());
      }

      // Rewind.
      ASSERT_NE(lseek(file, 0, SEEK_SET), (off_t)-1);

      {
        FileInputStream input(file, kBlockSizes[j]);
        GzipInputStream gzin(&input);
        ReadStuffLarge(&gzin);
        EXPECT_EQ(0, input.GetErrno());
      }

      close(file);
    }
  }
}
#endif

// MSVC raises various debugging exceptions if we try to use a file
// descriptor of -1, defeating our tests below.  This class will disable
// these debug assertions while in scope.
class MsvcDebugDisabler {
 public:
#if defined(_MSC_VER) && _MSC_VER >= 1400
  MsvcDebugDisabler() {
    old_handler_ = _set_invalid_parameter_handler(MyHandler);
    old_mode_ = _CrtSetReportMode(_CRT_ASSERT, 0);
  }
  ~MsvcDebugDisabler() {
    old_handler_ = _set_invalid_parameter_handler(old_handler_);
    old_mode_ = _CrtSetReportMode(_CRT_ASSERT, old_mode_);
  }

  static void MyHandler(const wchar_t* expr, const wchar_t* func,
                        const wchar_t* file, unsigned int line,
                        uintptr_t pReserved) {
    // do nothing
  }

  _invalid_parameter_handler old_handler_;
  int old_mode_;
#else
  // Dummy constructor and destructor to ensure that GCC doesn't complain
  // that debug_disabler is an unused variable.
  MsvcDebugDisabler() {}
  ~MsvcDebugDisabler() {}
#endif
};

// Test that FileInputStreams report errors correctly.
TEST_F(IoTest, FileReadError) {
  MsvcDebugDisabler debug_disabler;

  // -1 = invalid file descriptor.
  FileInputStream input(-1);

  const void* buffer;
  int size;
  EXPECT_FALSE(input.Next(&buffer, &size));
  EXPECT_EQ(EBADF, input.GetErrno());
}

// Test that FileOutputStreams report errors correctly.
TEST_F(IoTest, FileWriteError) {
  MsvcDebugDisabler debug_disabler;

  // -1 = invalid file descriptor.
  FileOutputStream input(-1);

  void* buffer;
  int size;

  // The first call to Next() succeeds because it doesn't have anything to
  // write yet.
  EXPECT_TRUE(input.Next(&buffer, &size));

  // Second call fails.
  EXPECT_FALSE(input.Next(&buffer, &size));

  EXPECT_EQ(EBADF, input.GetErrno());
}

// Pipes are not seekable, so File{Input,Output}Stream ends up doing some
// different things to handle them.  We'll test by writing to a pipe and
// reading back from it.
TEST_F(IoTest, PipeIo) {
  int files[2];

  for (int i = 0; i < kBlockSizeCount; i++) {
    for (int j = 0; j < kBlockSizeCount; j++) {
      // Need to create a new pipe each time because ReadStuff() expects
      // to see EOF at the end.
      ASSERT_EQ(pipe(files), 0);

      {
        FileOutputStream output(files[1], kBlockSizes[i]);
        WriteStuff(&output);
        EXPECT_EQ(0, output.GetErrno());
      }
      close(files[1]);  // Send EOF.

      {
        FileInputStream input(files[0], kBlockSizes[j]);
        ReadStuff(&input);
        EXPECT_EQ(0, input.GetErrno());
      }
      close(files[0]);
    }
  }
}

// Test using C++ iostreams.
TEST_F(IoTest, IostreamIo) {
  for (int i = 0; i < kBlockSizeCount; i++) {
    for (int j = 0; j < kBlockSizeCount; j++) {
      {
        std::stringstream stream;

        {
          OstreamOutputStream output(&stream, kBlockSizes[i]);
          WriteStuff(&output);
          EXPECT_FALSE(stream.fail());
        }

        {
          IstreamInputStream input(&stream, kBlockSizes[j]);
          ReadStuff(&input);
          EXPECT_TRUE(stream.eof());
        }
      }

      {
        std::stringstream stream;

        {
          OstreamOutputStream output(&stream, kBlockSizes[i]);
          WriteStuffLarge(&output);
          EXPECT_FALSE(stream.fail());
        }

        {
          IstreamInputStream input(&stream, kBlockSizes[j]);
          ReadStuffLarge(&input);
          EXPECT_TRUE(stream.eof());
        }
      }
    }
  }
}

// To test ConcatenatingInputStream, we create several ArrayInputStreams
// covering a buffer and then concatenate them.
TEST_F(IoTest, ConcatenatingInputStream) {
  const int kBufferSize = 256;
  uint8_t buffer[kBufferSize];

  // Fill the buffer.
  ArrayOutputStream output(buffer, kBufferSize);
  WriteStuff(&output);

  // Now split it up into multiple streams of varying sizes.
  ASSERT_EQ(68, output.ByteCount());  // Test depends on this.
  ArrayInputStream input1(buffer, 12);
  ArrayInputStream input2(buffer + 12, 7);
  ArrayInputStream input3(buffer + 19, 6);
  ArrayInputStream input4(buffer + 25, 15);
  ArrayInputStream input5(buffer + 40, 0);
  // Note:  We want to make sure we have a stream boundary somewhere between
  // bytes 42 and 62, which is the range that it Skip()ed by ReadStuff().  This
  // tests that a bug that existed in the original code for Skip() is fixed.
  ArrayInputStream input6(buffer + 40, 10);
  ArrayInputStream input7(buffer + 50, 18);  // Total = 68 bytes.

  ZeroCopyInputStream* streams[] = {&input1, &input2, &input3, &input4,
                                    &input5, &input6, &input7};

  // Create the concatenating stream and read.
  ConcatenatingInputStream input(streams, ABSL_ARRAYSIZE(streams));
  ReadStuff(&input);
}

// To test LimitingInputStream, we write our golden text to a buffer, then
// create an ArrayInputStream that contains the whole buffer (not just the
// bytes written), then use a LimitingInputStream to limit it just to the
// bytes written.
TEST_F(IoTest, LimitingInputStream) {
  const int kBufferSize = 256;
  uint8_t buffer[kBufferSize];

  // Fill the buffer.
  ArrayOutputStream output(buffer, kBufferSize);
  WriteStuff(&output);

  // Set up input.
  ArrayInputStream array_input(buffer, kBufferSize);
  LimitingInputStream input(&array_input, output.ByteCount());

  ReadStuff(&input);
}

// Checks that ByteCount works correctly for LimitingInputStreams where the
// underlying stream has already been read.
TEST_F(IoTest, LimitingInputStreamByteCount) {
  const int kHalfBufferSize = 128;
  const int kBufferSize = kHalfBufferSize * 2;
  uint8_t buffer[kBufferSize] = {};

  // Set up input. Only allow half to be read at once.
  ArrayInputStream array_input(buffer, kBufferSize, kHalfBufferSize);
  const void* data;
  int size;
  EXPECT_TRUE(array_input.Next(&data, &size));
  EXPECT_EQ(kHalfBufferSize, array_input.ByteCount());
  // kHalfBufferSize - 1 to test limiting logic as well.
  LimitingInputStream input(&array_input, kHalfBufferSize - 1);
  EXPECT_EQ(0, input.ByteCount());
  EXPECT_TRUE(input.Next(&data, &size));
  EXPECT_EQ(kHalfBufferSize - 1, input.ByteCount());
}

// Check that a zero-size array doesn't confuse the code.
TEST(ZeroSizeArray, Input) {
  ArrayInputStream input(nullptr, 0);
  const void* data;
  int size;
  EXPECT_FALSE(input.Next(&data, &size));
}

TEST(ZeroSizeArray, Output) {
  ArrayOutputStream output(nullptr, 0);
  void* data;
  int size;
  EXPECT_FALSE(output.Next(&data, &size));
}

}  // namespace
}  // namespace io
}  // namespace protobuf
}  // namespace google