text: /* 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 <m_string.h>
  #include <errno.h>
  
  
  /*
    Read a chunk of bytes from a file from a given position
  
    SYNOPSIOS
      my_pread()
      Filedes	File decsriptor
      Buffer	Buffer to read data into
      Count	Number of bytes to read
      offset	Position to read from
      MyFlags	Flags
  
    NOTES
      This differs from the normal pread() call in that we don't care
      to set the position in the file back to the original position
      if the system doesn't support pread().
  
    RETURN
      (size_t) -1   Error
      #             Number of bytes read
  */
  
  size_t my_pread(File Filedes, uchar *Buffer, size_t Count, my_off_t offset,
                  myf MyFlags)
  {
    size_t readbytes;
    int error= 0;
    DBUG_ENTER("my_pread");
    DBUG_PRINT("my",("fd: %d  Seek: %llu  Buffer: %p  Count: %lu  MyFlags: %d",
               Filedes, (ulonglong)offset, Buffer, (ulong)Count, MyFlags));
    for (;;)
    {
      errno= 0;    /* Linux, Windows don't reset this on EOF/success */
  #if defined(_WIN32)
      readbytes= my_win_pread(Filedes, Buffer, Count, offset);
  #else
      readbytes= pread(Filedes, Buffer, Count, offset);
  #endif
      error= (readbytes != Count);
      if(error)
      {
        my_errno= errno ? errno : -1;
        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 %u from %d, errno: %d",
                              (int) readbytes, (uint) Count,Filedes,my_errno));
  
        if ((readbytes == 0 || readbytes == (size_t) -1) && errno == EINTR)
        {
          DBUG_PRINT("debug", ("my_pread() was interrupted and returned %d",
                               (int) 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(0), my_filename(Filedes),
                     my_errno, my_strerror(errbuf, sizeof(errbuf), my_errno));
          else if (MyFlags & (MY_NABP | MY_FNABP))
            my_error(EE_EOFERR, MYF(0), my_filename(Filedes),
                     my_errno, my_strerror(errbuf, sizeof(errbuf), my_errno));
        }
        if (readbytes == (size_t) -1 || (MyFlags & (MY_FNABP | MY_NABP)))
          DBUG_RETURN(MY_FILE_ERROR);         /* Return with error */
      }
      if (MyFlags & (MY_NABP | MY_FNABP))
        DBUG_RETURN(0);                      /* Read went ok; Return 0 */
      DBUG_RETURN(readbytes);                /* purecov: inspected */
    }
  } /* my_pread */
  
  
  /**
    Write a chunk of bytes to a file at a given position
  
    SYNOPSIOS
      my_pwrite()
      Filedes	File decsriptor
      Buffer	Buffer to write data from
      Count	Number of bytes to write
      offset	Position to write to
      MyFlags	Flags
  
    NOTES
      This differs from the normal pwrite() call in that we don't care
      to set the position in the file back to the original position
      if the system doesn't support pwrite()
  
    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_pwrite(File Filedes, const uchar *Buffer, size_t Count,
                   my_off_t offset, myf MyFlags)
  {
    size_t writtenbytes;
    size_t sum_written= 0;
    uint errors= 0;
    const size_t initial_count= Count;
  
    DBUG_ENTER("my_pwrite");
    DBUG_PRINT("my",("fd: %d  Seek: %llu  Buffer: %p  Count: %lu  MyFlags: %d",
               Filedes, offset, Buffer, (ulong)Count, MyFlags));
  
    for (;;)
    {
      errno= 0;
  #if defined (_WIN32)
      writtenbytes= my_win_pwrite(Filedes, Buffer, Count, offset);
  #else
      writtenbytes= pwrite(Filedes, Buffer, Count, offset);
  #endif
      if(writtenbytes == Count)
      {
        sum_written+= writtenbytes;
        break;
      }
      my_errno= errno;
      if (writtenbytes != (size_t) -1)
      {
        sum_written+= writtenbytes;
        Buffer+= writtenbytes;
        Count-= writtenbytes;
        offset+= writtenbytes;
      }
      DBUG_PRINT("error",("Write only %u bytes", (uint) writtenbytes));
  
      if (mysys_thread_var()->abort)
        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++;
        continue;
      }
      if (writtenbytes != 0 && writtenbytes != (size_t) -1)
        continue;
      else if (my_errno == EINTR)
      {
        continue;                                 /* Retry */
      }
      else if (writtenbytes == 0 && !errors++)    /* Retry once */
      {
        /* We may come here if the file quota is exeeded */
        continue;
      }
      break;                                  /* Return bytes written */
    }
    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);
    }
    DBUG_EXECUTE_IF("check", my_seek(Filedes, -1, SEEK_SET, MYF(0)););
  
    if (sum_written == 0)
      DBUG_RETURN(MY_FILE_ERROR);
  
    DBUG_RETURN(sum_written);
  } /* my_pwrite */
  