// Copyright (c) 2012 The Chromium 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 "base/files/file.h"

#include <errno.h>
#include <fcntl.h>
#include <stdint.h>
#include <sys/stat.h>
#include <unistd.h>

#include "base/logging.h"
#include "base/posix/eintr_wrapper.h"
#include "base/strings/utf_string_conversions.h"
#include "util/build_config.h"

namespace base {

// Make sure our Whence mappings match the system headers.
static_assert(File::FROM_BEGIN == SEEK_SET && File::FROM_CURRENT == SEEK_CUR &&
                  File::FROM_END == SEEK_END,
              "whence mapping must match the system headers");

namespace {

#if defined(OS_BSD) || defined(OS_MACOSX) || \
    defined(OS_ANDROID) && __ANDROID_API__ < 21
int CallFstat(int fd, stat_wrapper_t* sb) {
  return fstat(fd, sb);
}
#else
int CallFstat(int fd, stat_wrapper_t* sb) {
  return fstat64(fd, sb);
}
#endif

// Some systems don't provide the following system calls, so either simulate
// them or wrap them in order to minimize the number of #ifdef's in this file.
#if !defined(OS_AIX)
bool IsOpenAppend(PlatformFile file) {
  return (fcntl(file, F_GETFL) & O_APPEND) != 0;
}

int CallFtruncate(PlatformFile file, int64_t length) {
  return HANDLE_EINTR(ftruncate(file, length));
}

#if !defined(OS_FUCHSIA)
File::Error CallFcntlFlock(PlatformFile file, bool do_lock) {
  struct flock lock;
  lock.l_type = do_lock ? F_WRLCK : F_UNLCK;
  lock.l_whence = SEEK_SET;
  lock.l_start = 0;
  lock.l_len = 0;  // Lock entire file.
  if (HANDLE_EINTR(fcntl(file, F_SETLK, &lock)) == -1)
    return File::GetLastFileError();
  return File::FILE_OK;
}
#endif

#else   // !defined(OS_AIX)

bool IsOpenAppend(PlatformFile file) {
  // NaCl doesn't implement fcntl. Since NaCl's write conforms to the POSIX
  // standard and always appends if the file is opened with O_APPEND, just
  // return false here.
  return false;
}

int CallFtruncate(PlatformFile file, int64_t length) {
  NOTIMPLEMENTED();  // NaCl doesn't implement ftruncate.
  return 0;
}

File::Error CallFcntlFlock(PlatformFile file, bool do_lock) {
  NOTIMPLEMENTED();  // NaCl doesn't implement flock struct.
  return File::FILE_ERROR_INVALID_OPERATION;
}
#endif  // defined(OS_AIX)

}  // namespace

void File::Info::FromStat(const stat_wrapper_t& stat_info) {
  is_directory = S_ISDIR(stat_info.st_mode);
  is_symbolic_link = S_ISLNK(stat_info.st_mode);
  size = stat_info.st_size;

#if defined(OS_MACOSX)
  time_t last_modified_sec = stat_info.st_mtimespec.tv_sec;
  int64_t last_modified_nsec = stat_info.st_mtimespec.tv_nsec;
  time_t last_accessed_sec = stat_info.st_atimespec.tv_sec;
  int64_t last_accessed_nsec = stat_info.st_atimespec.tv_nsec;
  time_t creation_time_sec = stat_info.st_ctimespec.tv_sec;
  int64_t creation_time_nsec = stat_info.st_ctimespec.tv_nsec;
#elif defined(OS_AIX)
  time_t last_modified_sec = stat_info.st_mtime;
  int64_t last_modified_nsec = 0;
  time_t last_accessed_sec = stat_info.st_atime;
  int64_t last_accessed_nsec = 0;
  time_t creation_time_sec = stat_info.st_ctime;
  int64_t creation_time_nsec = 0;
#elif defined(OS_POSIX)
  time_t last_modified_sec = stat_info.st_mtim.tv_sec;
  int64_t last_modified_nsec = stat_info.st_mtim.tv_nsec;
  time_t last_accessed_sec = stat_info.st_atim.tv_sec;
  int64_t last_accessed_nsec = stat_info.st_atim.tv_nsec;
  time_t creation_time_sec = stat_info.st_ctim.tv_sec;
  int64_t creation_time_nsec = stat_info.st_ctim.tv_nsec;
#else
#error
#endif

  constexpr uint64_t kNano = 1'000'000'000;
  last_modified = last_modified_sec * kNano + last_modified_nsec;
  last_accessed = last_accessed_sec * kNano + last_accessed_nsec;
  creation_time = creation_time_sec * kNano + creation_time_nsec;
}

bool File::IsValid() const {
  return file_.is_valid();
}

PlatformFile File::GetPlatformFile() const {
  return file_.get();
}

PlatformFile File::TakePlatformFile() {
  return file_.release();
}

void File::Close() {
  if (!IsValid())
    return;

  file_.reset();
}

int64_t File::Seek(Whence whence, int64_t offset) {
  DCHECK(IsValid());

  static_assert(sizeof(int64_t) == sizeof(off_t), "off_t must be 64 bits");
  return lseek(file_.get(), static_cast<off_t>(offset),
               static_cast<int>(whence));
}

int File::Read(int64_t offset, char* data, int size) {
  DCHECK(IsValid());
  if (size < 0)
    return -1;

  int bytes_read = 0;
  int rv;
  do {
    rv = HANDLE_EINTR(pread(file_.get(), data + bytes_read, size - bytes_read,
                            offset + bytes_read));
    if (rv <= 0)
      break;

    bytes_read += rv;
  } while (bytes_read < size);

  return bytes_read ? bytes_read : rv;
}

int File::ReadAtCurrentPos(char* data, int size) {
  DCHECK(IsValid());
  if (size < 0)
    return -1;

  int bytes_read = 0;
  int rv;
  do {
    rv = HANDLE_EINTR(read(file_.get(), data + bytes_read, size - bytes_read));
    if (rv <= 0)
      break;

    bytes_read += rv;
  } while (bytes_read < size);

  return bytes_read ? bytes_read : rv;
}

int File::ReadNoBestEffort(int64_t offset, char* data, int size) {
  DCHECK(IsValid());
  return HANDLE_EINTR(pread(file_.get(), data, size, offset));
}

int File::ReadAtCurrentPosNoBestEffort(char* data, int size) {
  DCHECK(IsValid());
  if (size < 0)
    return -1;

  return HANDLE_EINTR(read(file_.get(), data, size));
}

int File::Write(int64_t offset, const char* data, int size) {
  if (IsOpenAppend(file_.get()))
    return WriteAtCurrentPos(data, size);

  DCHECK(IsValid());
  if (size < 0)
    return -1;

  int bytes_written = 0;
  int rv;
  do {
    rv = HANDLE_EINTR(pwrite(file_.get(), data + bytes_written,
                             size - bytes_written, offset + bytes_written));
    if (rv <= 0)
      break;

    bytes_written += rv;
  } while (bytes_written < size);

  return bytes_written ? bytes_written : rv;
}

int File::WriteAtCurrentPos(const char* data, int size) {
  DCHECK(IsValid());
  if (size < 0)
    return -1;

  int bytes_written = 0;
  int rv;
  do {
    rv = HANDLE_EINTR(
        write(file_.get(), data + bytes_written, size - bytes_written));
    if (rv <= 0)
      break;

    bytes_written += rv;
  } while (bytes_written < size);

  return bytes_written ? bytes_written : rv;
}

int File::WriteAtCurrentPosNoBestEffort(const char* data, int size) {
  DCHECK(IsValid());
  if (size < 0)
    return -1;

  return HANDLE_EINTR(write(file_.get(), data, size));
}

int64_t File::GetLength() {
  DCHECK(IsValid());

  stat_wrapper_t file_info;
  if (CallFstat(file_.get(), &file_info))
    return -1;

  return file_info.st_size;
}

bool File::SetLength(int64_t length) {
  DCHECK(IsValid());

  return !CallFtruncate(file_.get(), length);
}

bool File::GetInfo(Info* info) {
  DCHECK(IsValid());

  stat_wrapper_t file_info;
  if (CallFstat(file_.get(), &file_info))
    return false;

  info->FromStat(file_info);
  return true;
}

#if !defined(OS_FUCHSIA)
File::Error File::Lock() {
  return CallFcntlFlock(file_.get(), true);
}

File::Error File::Unlock() {
  return CallFcntlFlock(file_.get(), false);
}
#endif

File File::Duplicate() const {
  if (!IsValid())
    return File();

  PlatformFile other_fd = HANDLE_EINTR(dup(GetPlatformFile()));
  if (other_fd == -1)
    return File(File::GetLastFileError());

  File other(other_fd);
  if (async())
    other.async_ = true;
  return other;
}

// Static.
File::Error File::OSErrorToFileError(int saved_errno) {
  switch (saved_errno) {
    case EACCES:
    case EISDIR:
    case EROFS:
    case EPERM:
      return FILE_ERROR_ACCESS_DENIED;
    case EBUSY:
    case ETXTBSY:
      return FILE_ERROR_IN_USE;
    case EEXIST:
      return FILE_ERROR_EXISTS;
    case EIO:
      return FILE_ERROR_IO;
    case ENOENT:
      return FILE_ERROR_NOT_FOUND;
    case ENFILE:  // fallthrough
    case EMFILE:
      return FILE_ERROR_TOO_MANY_OPENED;
    case ENOMEM:
      return FILE_ERROR_NO_MEMORY;
    case ENOSPC:
      return FILE_ERROR_NO_SPACE;
    case ENOTDIR:
      return FILE_ERROR_NOT_A_DIRECTORY;
    default:
      // This function should only be called for errors.
      DCHECK_NE(0, saved_errno);
      return FILE_ERROR_FAILED;
  }
}

// TODO(erikkay): does it make sense to support FLAG_EXCLUSIVE_* here?
void File::DoInitialize(const FilePath& path, uint32_t flags) {
  DCHECK(!IsValid());

  int open_flags = 0;
  if (flags & FLAG_CREATE)
    open_flags = O_CREAT | O_EXCL;

  created_ = false;

  if (flags & FLAG_CREATE_ALWAYS) {
    DCHECK(!open_flags);
    DCHECK(flags & FLAG_WRITE);
    open_flags = O_CREAT | O_TRUNC;
  }

  if (flags & FLAG_OPEN_TRUNCATED) {
    DCHECK(!open_flags);
    DCHECK(flags & FLAG_WRITE);
    open_flags = O_TRUNC;
  }

  if (!open_flags && !(flags & FLAG_OPEN) && !(flags & FLAG_OPEN_ALWAYS)) {
    NOTREACHED();
    errno = EOPNOTSUPP;
    error_details_ = FILE_ERROR_FAILED;
    return;
  }

  if (flags & FLAG_WRITE && flags & FLAG_READ) {
    open_flags |= O_RDWR;
  } else if (flags & FLAG_WRITE) {
    open_flags |= O_WRONLY;
  } else if (!(flags & FLAG_READ) && !(flags & FLAG_WRITE_ATTRIBUTES) &&
             !(flags & FLAG_APPEND) && !(flags & FLAG_OPEN_ALWAYS)) {
    NOTREACHED();
  }

  if (flags & FLAG_TERMINAL_DEVICE)
    open_flags |= O_NOCTTY | O_NDELAY;

  if (flags & FLAG_APPEND && flags & FLAG_READ)
    open_flags |= O_APPEND | O_RDWR;
  else if (flags & FLAG_APPEND)
    open_flags |= O_APPEND | O_WRONLY;

  static_assert(O_RDONLY == 0, "O_RDONLY must equal zero");

  int mode = S_IRUSR | S_IWUSR;
  int descriptor = HANDLE_EINTR(open(path.value().c_str(), open_flags, mode));

  if (flags & FLAG_OPEN_ALWAYS) {
    if (descriptor < 0) {
      open_flags |= O_CREAT;
      if (flags & FLAG_EXCLUSIVE_READ || flags & FLAG_EXCLUSIVE_WRITE)
        open_flags |= O_EXCL;  // together with O_CREAT implies O_NOFOLLOW

      descriptor = HANDLE_EINTR(open(path.value().c_str(), open_flags, mode));
      if (descriptor >= 0)
        created_ = true;
    }
  }

  if (descriptor < 0) {
    error_details_ = File::GetLastFileError();
    return;
  }

  if (flags & (FLAG_CREATE_ALWAYS | FLAG_CREATE))
    created_ = true;

  if (flags & FLAG_DELETE_ON_CLOSE)
    unlink(path.value().c_str());

  async_ = ((flags & FLAG_ASYNC) == FLAG_ASYNC);
  error_details_ = FILE_OK;
  file_.reset(descriptor);
}

bool File::Flush() {
  DCHECK(IsValid());

#if defined(OS_LINUX)
  return !HANDLE_EINTR(fdatasync(file_.get()));
#else
  return !HANDLE_EINTR(fsync(file_.get()));
#endif
}

void File::SetPlatformFile(PlatformFile file) {
  DCHECK(!file_.is_valid());
  file_.reset(file);
}

// static
File::Error File::GetLastFileError() {
  return base::File::OSErrorToFileError(errno);
}

}  // namespace base