my_read.c

/* Copyright (c) 2000, 2013, 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 "mysys_err.h"
#include <my_base.h>
#include <errno.h>

/*
  Read a chunk of bytes from a file with retry's if needed

  The parameters are:
    File descriptor
    Buffer to hold at least Count bytes
    Bytes to read
    Flags on what to do on error

    Return:
      -1 on error
      0  if flag has bits MY_NABP or MY_FNABP set
      N  number of bytes read.
*/

size_t my_read(File Filedes, uchar *Buffer, size_t Count, myf MyFlags)
{
  size_t readbytes, save_count;
  DBUG_ENTER("my_read");
  DBUG_PRINT("my",("fd: %d  Buffer: %p  Count: %lu  MyFlags: %d",
                   Filedes, Buffer, (ulong) Count, MyFlags));
  save_count= Count;

  for (;;)
  {
    errno= 0;                                   /* Linux, Windows don't reset this on EOF/success */
#ifdef _WIN32
    readbytes= my_win_read(Filedes, Buffer, Count);
#else
    readbytes= read(Filedes, Buffer, Count);
#endif
    DBUG_EXECUTE_IF ("simulate_file_read_error",
                     {
                       errno= ENOSPC;
                       readbytes= (size_t) -1;
                       DBUG_SET("-d,simulate_file_read_error");
                       DBUG_SET("-d,simulate_my_b_fill_error");
                     });

    if (readbytes != Count)
    {
      my_errno= errno;
      if (errno == 0 || (readbytes != (size_t) -1 &&
                         (MyFlags & (MY_NABP | MY_FNABP))))
        my_errno= HA_ERR_FILE_TOO_SHORT;
      DBUG_PRINT("warning",("Read only %d bytes off %lu from %d, errno: %d",
                            (int) readbytes, (ulong) Count, Filedes,
                            my_errno));

      if ((readbytes == 0 || (int) readbytes == -1) && errno == EINTR)
      {  
        DBUG_PRINT("debug", ("my_read() was interrupted and returned %ld",
                             (long) readbytes));
        continue;                              /* Interrupted */
      }

      if (MyFlags & (MY_WME | MY_FAE | MY_FNABP))
      {
        char errbuf[MYSYS_STRERROR_SIZE];
        if (readbytes == (size_t) -1)
          my_error(EE_READ, MYF(ME_BELL+ME_WAITTANG), my_filename(Filedes),
                   my_errno, my_strerror(errbuf, sizeof(errbuf), my_errno));
        else if (MyFlags & (MY_NABP | MY_FNABP))
          my_error(EE_EOFERR, MYF(ME_BELL+ME_WAITTANG), my_filename(Filedes),
                   my_errno, my_strerror(errbuf, sizeof(errbuf), my_errno));
      }
      if (readbytes == (size_t) -1 ||
          ((MyFlags & (MY_FNABP | MY_NABP)) && !(MyFlags & MY_FULL_IO)))
        DBUG_RETURN(MY_FILE_ERROR);     /* Return with error */
      if (readbytes != (size_t) -1 && (MyFlags & MY_FULL_IO))
      {
        Buffer+= readbytes;
        Count-= readbytes;
        continue;
      }
    }

    if (MyFlags & (MY_NABP | MY_FNABP))
      readbytes= 0;                     /* Ok on read */
    else if (MyFlags & MY_FULL_IO)
      readbytes= save_count;
    break;
  }
  DBUG_RETURN(readbytes);
} /* my_read */