queues     = queuesa[:0]
		mreply     []byte
		dstPfx     []byte
		checkReply = len(reply) > 0
	)

	sub := subPool.Get().(*subscription)

	if subjectStartsWithGatewayReplyPrefix(subject) {
		dstPfx = subject[:8]
	}
	for i := 0; i < len(gws); i++ {
		gwc := gws[i]
		if dstPfx != nil {
			gwc.mu.Lock()
			ok := bytes.Equal(dstPfx, gwc.gw.cfg.replyPfx)
			gwc.mu.Unlock()
			if !ok {
				continue

	dstoff, err := dst.Seek(0, io.SeekCurrent)
	if err != nil {
		t.Fatal(err)
	}
	srcoff, err := src.Seek(0, io.SeekCurrent)
	if err != nil {
		t.Fatal(err)
	}
	if dstoff != srcoff {
		t.Errorf("offsets differ: dstoff = %d, srcoff = %d", dstoff, srcoff)
	}
	if dstoff != int64(len(data)) {
		t.Errorf("dstoff = %d, want %d", dstoff, len(data))
	}
	if n != int64(len(data)) {

  //   If file exists, truncate its size to 0.
  int dst_fd = open(dst, O_WRONLY | O_CREAT | O_TRUNC, open_mode);
  if (dst_fd < 0) {
    close(src_fd);
    return -1;
  }

  // Both files have been opened, do the transfer.
  // Since errno would be overridden by `close` below, save it here.
  int error_code = 0;
  if (CopyFileContents(dst_fd, src_fd, size) < 0) error_code = errno;

  close(src_fd);

#include "tensorflow/c/experimental/filesystem/plugins/posix/copy_file.h"

namespace tf_posix_filesystem {

// Transfers up to `size` bytes from `dst_fd` to `src_fd`.
//
// This method uses `sendfile` specific to linux after 2.6.33.
int CopyFileContents(int dst_fd, int src_fd, off_t size) {
  off_t offset = 0;
  int bytes_transferred = 0;
  int rc = 1;
  // When `sendfile` returns 0 we stop copying and let callers handle this.

// SendFile wraps the sendfile system call.
func SendFile(dstFD *FD, src int, pos, remain int64) (written int64, err error, handled bool) {
	defer func() {
		TestHookDidSendFile(dstFD, src, written, err, handled)
	}()
	if err := dstFD.writeLock(); err != nil {
		return 0, err, false
	}
	defer dstFD.writeUnlock()

	if err := dstFD.pd.prepareWrite(dstFD.isFile); err != nil {
		return 0, err, false
	}

    return 0;
  }

  @Override
  int internalArrayEnd() {
    return array.length;
  }

  @Override
  int copyIntoArray(@Nullable Object[] dst, int dstOff) {
    System.arraycopy(array, 0, dst, dstOff, array.length);
    return dstOff + array.length;
  }

  // The fake cast to E is safe because the creation methods only allow E's
  @Override
  @SuppressWarnings("unchecked")
  public E get(int index) {

// SendFile wraps the sendfile system call.
func SendFile(dstFD *FD, src int, remain int64) (written int64, err error, handled bool) {
	defer func() {
		TestHookDidSendFile(dstFD, src, written, err, handled)
	}()
	if err := dstFD.writeLock(); err != nil {
		return 0, err, false
	}
	defer dstFD.writeUnlock()

	if err := dstFD.pd.prepareWrite(dstFD.isFile); err != nil {
		return 0, err, false
	}

	dst := dstFD.Sysfd

#include <memory>

#include "tensorflow/c/experimental/filesystem/plugins/posix/copy_file.h"

namespace tf_posix_filesystem {

// Transfers up to `size` bytes from `dst_fd` to `src_fd`.
//
// This method uses a temporary buffer to hold contents.
int CopyFileContents(int dst_fd, int src_fd, off_t size) {
  // Use a copy buffer of 128KB but don't store it on the stack.
  constexpr static size_t kPosixCopyFileBufferSize = 128 * 1024;

    return 0;
  }

  @Override
  int internalArrayEnd() {
    return size;
  }

  @Override
  int copyIntoArray(@Nullable Object[] dst, int dstOff) {
    System.arraycopy(array, 0, dst, dstOff, size);
    return dstOff + size;
  }

  // The fake cast to E is safe because the creation methods only allow E's
  @Override
  @SuppressWarnings("unchecked")
  public E get(int index) {

// SendFile wraps the sendfile system call.
func SendFile(dstFD *FD, src int, pos, remain int64) (written int64, err error, handled bool) {
	defer func() {
		TestHookDidSendFile(dstFD, src, written, err, handled)
	}()
	if err := dstFD.writeLock(); err != nil {
		return 0, err, false
	}
	defer dstFD.writeUnlock()

	if err := dstFD.pd.prepareWrite(dstFD.isFile); err != nil {
		return 0, err, false
	}