my_write.c

/* Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */

#include "mysys_priv.h"
#include "my_sys.h"
#include "mysys_err.h"
#include <errno.h>
#include "my_thread_local.h"


/**
  Write a chunk of bytes to a file

  if (MyFlags & (MY_NABP | MY_FNABP))
  @returns
    0  if Count == 0
    On succes, 0
    On failure, (size_t)-1 == MY_FILE_ERROR

  otherwise
  @returns
    0  if Count == 0
    On success, the number of bytes written.
    On partial success (if less than Count bytes could be written),
       the actual number of bytes written.
    On failure, (size_t)-1 == MY_FILE_ERROR
*/
size_t my_write(File Filedes, const uchar *Buffer, size_t Count, myf MyFlags)
{
  size_t writtenbytes;
  size_t sum_written= 0;
  uint errors= 0;
  const size_t initial_count= Count;

  DBUG_ENTER("my_write");
  DBUG_PRINT("my",("fd: %d  Buffer: %p  Count: %lu  MyFlags: %d",
		   Filedes, Buffer, (ulong) Count, MyFlags));

  /* The behavior of write(fd, buf, 0) is not portable */
  if (unlikely(!Count))
    DBUG_RETURN(0);
  
  DBUG_EXECUTE_IF ("simulate_no_free_space_error",
                   { DBUG_SET("+d,simulate_file_write_error");});
  for (;;)
  {
    errno= 0;
#ifdef _WIN32
    writtenbytes= my_win_write(Filedes, Buffer, Count);
#else
    writtenbytes= write(Filedes, Buffer, Count);
#endif
    DBUG_EXECUTE_IF("simulate_file_write_error",
                    {
                      errno= ENOSPC;
                      writtenbytes= (size_t) -1;
                    });
    if (writtenbytes == Count)
    {
      sum_written+= writtenbytes;
      break;
    }
    if (writtenbytes != (size_t) -1)
    {						/* Safeguard */
      sum_written+= writtenbytes;
      Buffer+= writtenbytes;
      Count-= writtenbytes;
    }
    set_my_errno(errno);
    DBUG_PRINT("error",("Write only %ld bytes, error: %d",
			(long) writtenbytes, my_errno()));
    if (is_killed_hook(NULL))
      MyFlags&= ~ MY_WAIT_IF_FULL;		/* End if aborted by user */

    if ((my_errno() == ENOSPC || my_errno() == EDQUOT) &&
        (MyFlags & MY_WAIT_IF_FULL))
    {
      wait_for_free_space(my_filename(Filedes), errors);
      errors++;
      DBUG_EXECUTE_IF("simulate_no_free_space_error",
                      { DBUG_SET("-d,simulate_file_write_error");});
      continue;
    }

    if (writtenbytes != 0 && writtenbytes != (size_t) -1)
      continue;                                 /* Retry if something written */
    else if (my_errno() == EINTR)
    {
      DBUG_PRINT("debug", ("my_write() was interrupted and returned %ld",
                           (long) writtenbytes));
      continue;                                 /* Interrupted, retry */
    }
    else if (writtenbytes == 0 && !errors++)    /* Retry once */
    {
      /* We may come here if the file quota is exeeded */
      continue;
    }
    break;
  }
  if (MyFlags & (MY_NABP | MY_FNABP))
  {
    if (sum_written == initial_count)
      DBUG_RETURN(0);        /* Want only errors, not bytes written */
    if (MyFlags & (MY_WME | MY_FAE | MY_FNABP))
    {
      char errbuf[MYSYS_STRERROR_SIZE];
      my_error(EE_WRITE, MYF(0), my_filename(Filedes),
               my_errno(), my_strerror(errbuf, sizeof(errbuf), my_errno()));
    }
    DBUG_RETURN(MY_FILE_ERROR);
  }

  if (sum_written == 0)
    DBUG_RETURN(MY_FILE_ERROR);

  DBUG_RETURN(sum_written);
} /* my_write */