/* Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult AB
   
   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public
   License as published by the Free Software Foundation; either
   version 2 of the License, or (at your option) any later version.
   
   This library 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
   Library General Public License for more details.
   
   You should have received a copy of the GNU Library General Public
   License along with this library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
   MA 02111-1307, USA */

/*
  Cashing of files with only does (sequential) read or writes of fixed-
  length records. A read isn't allowed to go over file-length. A read is ok
  if it ends at file-length and next read can try to read after file-length
  (and get a EOF-error).
  Possibly use of asyncronic io.
  macros for read and writes for faster io.
  Used instead of FILE when reading or writing whole files.
  This will make mf_rec_cache obsolete.
  One can change info->pos_in_file to a higher value to skip bytes in file if
  also info->rc_pos is set to info->rc_end.
  If called through open_cached_file(), then the temporary file will
  only be created if a write exeeds the file buffer or if one calls
  flush_io_cache().  
*/

#define MAP_TO_USE_RAID
#include "mysys_priv.h"
#include <m_string.h>
#ifdef HAVE_AIOWAIT
#include "mysys_err.h"
static void my_aiowait(my_aio_result *result);
#endif
#include <assert.h>
#include <errno.h>

#ifdef MAIN
#include <my_dir.h>
#endif

static void init_read_function(IO_CACHE* info, enum cache_type type);
static void init_write_function(IO_CACHE* info, enum cache_type type);

static void init_read_function(IO_CACHE* info, enum cache_type type)
{
  switch (type)
  {
#ifndef MYSQL_CLIENT    
  case READ_NET:
    /* must be initialized by the caller. The problem is that
       _my_b_net_read has to be defined in sql directory because of
       the dependency on THD, and therefore cannot be visible to
       programs that link against mysys but know nothing about THD, such
       as myisamchk
    */
    break;
#endif
  case SEQ_READ_APPEND:
    info->read_function = _my_b_seq_read;
    break;
  default:
    info->read_function = _my_b_read;
  }
}

static void init_write_function(IO_CACHE* info, enum cache_type type)
{
  switch (type)
  {
  case SEQ_READ_APPEND:
    info->write_function = _my_b_append;
    break;
  default:
    info->write_function = _my_b_write;
  }
}

	/*
	** if cachesize == 0 then use default cachesize (from s-file)
	** if file == -1 then real_open_cached_file() will be called.
	** returns 0 if ok
	*/

int init_io_cache(IO_CACHE *info, File file, uint cachesize,
		  enum cache_type type, my_off_t seek_offset,
		  pbool use_async_io, myf cache_myflags)
{
  uint min_cache;
  DBUG_ENTER("init_io_cache");
  DBUG_PRINT("enter",("type: %d  pos: %ld",(int) type, (ulong) seek_offset));

  /* There is no file in net_reading */
  info->file= file;
  info->pre_close = info->pre_read = info->post_read = 0;
  info->arg = 0;
  if (!cachesize)
    if (! (cachesize= my_default_record_cache_size))
      DBUG_RETURN(1);				/* No cache requested */
  min_cache=use_async_io ? IO_SIZE*4 : IO_SIZE*2;
  info->alloced_buffer = 0;
  if (type == READ_CACHE || type == SEQ_READ_APPEND)
  {						/* Assume file isn't growing */
    if (cache_myflags & MY_DONT_CHECK_FILESIZE)
    {
      cache_myflags &= ~MY_DONT_CHECK_FILESIZE;
    }
    else
    {
      my_off_t file_pos,end_of_file;
      if ((file_pos=my_tell(file,MYF(0)) == MY_FILEPOS_ERROR))
	DBUG_RETURN(1);
      end_of_file=my_seek(file,0L,MY_SEEK_END,MYF(0));
      if (end_of_file < seek_offset)
	end_of_file=seek_offset;
      VOID(my_seek(file,file_pos,MY_SEEK_SET,MYF(0)));
      /* Trim cache size if the file is very small.
	 However, we should not do this with SEQ_READ_APPEND cache
      */
      if (type != SEQ_READ_APPEND &&
	  (my_off_t) cachesize > end_of_file-seek_offset+IO_SIZE*2-1)
      {
	cachesize=(uint) (end_of_file-seek_offset)+IO_SIZE*2-1;
	use_async_io=0;				/* No need to use async */
      }
    }
  }
  if ((int) type < (int) READ_NET)
  {
    uint buffer_block;
    for (;;)
    {
      buffer_block = cachesize=(uint) ((ulong) (cachesize + min_cache-1) &
			(ulong) ~(min_cache-1));
      if (type == SEQ_READ_APPEND)
	buffer_block *= 2;
      if (cachesize < min_cache)
	cachesize = min_cache;
      if ((info->buffer=
	   (byte*) my_malloc(buffer_block,
			     MYF((cache_myflags & ~ MY_WME) |
				 (cachesize == min_cache ? MY_WME : 0)))) != 0)
      {
	if (type == SEQ_READ_APPEND)
	  info->append_buffer = info->buffer + cachesize;
	info->alloced_buffer=1;
	break;					/* Enough memory found */
      }
      if (cachesize == min_cache)
	DBUG_RETURN(2);				/* Can't alloc cache */
      cachesize= (uint) ((long) cachesize*3/4); /* Try with less memory */
    }
  }
  else
    info->buffer=0;
  
  DBUG_PRINT("info",("init_io_cache: cachesize = %u",cachesize));
  info->pos_in_file= seek_offset;
  info->read_length=info->buffer_length=cachesize;
  info->seek_not_done= test(file >= 0 && type != READ_FIFO &&
			    type != READ_NET);
  info->myflags=cache_myflags & ~(MY_NABP | MY_FNABP);
  info->rc_request_pos=info->rc_pos= info->write_pos = info->buffer;
  info->write_pos = info->write_end = 0;
  if (type == SEQ_READ_APPEND)
  {
    info->append_read_pos = info->write_pos = info->append_buffer;
    info->write_end = info->append_end =
      info->append_buffer + info->buffer_length;
#ifdef THREAD    
    pthread_mutex_init(&info->append_buffer_lock,MY_MUTEX_INIT_FAST);
#endif    
  }

  if (type == READ_CACHE || type == SEQ_READ_APPEND ||
      type == READ_NET || type == READ_FIFO)
  {
    info->rc_end=info->buffer;			/* Nothing in cache */
  }
  else /* type == WRITE_CACHE */
  {
    info->write_end=
      info->buffer+info->buffer_length- (seek_offset & (IO_SIZE-1));
    info->write_pos = info->buffer;
  }
  /* end_of_file may be changed by user later */
  info->end_of_file= ((type == READ_NET || type == READ_FIFO ) ? 0
		      : ~(my_off_t) 0);
  info->type=type;
  info->error=0;
  init_read_function(info,type);
  init_write_function(info,type);
#ifdef HAVE_AIOWAIT
  if (use_async_io && ! my_disable_async_io)
  {
    DBUG_PRINT("info",("Using async io"));
    info->read_length/=2;
    info->read_function=_my_b_async_read;
  }
  info->inited=info->aio_result.pending=0;
#endif
  DBUG_RETURN(0);
}						/* init_io_cache */


	/* Wait until current request is ready */

#ifdef HAVE_AIOWAIT
static void my_aiowait(my_aio_result *result)
{
  if (result->pending)
  {
    struct aio_result_t *tmp;
    for (;;)
    {
      if ((int) (tmp=aiowait((struct timeval *) 0)) == -1)
      {
	if (errno == EINTR)
	  continue;
	DBUG_PRINT("error",("No aio request, error: %d",errno));
	result->pending=0;			/* Assume everythings is ok */
	break;
      }
      ((my_aio_result*) tmp)->pending=0;
      if ((my_aio_result*) tmp == result)
	break;
    }
  }
  return;
}
#endif

	/* Use this to reset cache to start or other type */
	/* Some simple optimizing is done when reinit in current buffer */

my_bool reinit_io_cache(IO_CACHE *info, enum cache_type type,
			my_off_t seek_offset,
			pbool use_async_io __attribute__((unused)),
			pbool clear_cache)
{
  DBUG_ENTER("reinit_io_cache");

  info->seek_not_done= test(info->file >= 0);	/* Seek not done */

  /* If the whole file is in memory, avoid flushing to disk */
  if (! clear_cache &&
      seek_offset >= info->pos_in_file &&
      seek_offset <= info->pos_in_file +
      (uint) (info->rc_end - info->rc_request_pos))
  {						/* use current buffer */
    if (info->type == WRITE_CACHE && type == READ_CACHE)
    {
      info->rc_end=info->write_pos;
      info->end_of_file=my_b_tell(info);
    }
    else if (type == WRITE_CACHE)
    {
      if (info->type == READ_CACHE)
      {
	info->write_end=info->buffer+info->buffer_length;
	info->write_pos=info->rc_pos;
      }
      info->end_of_file = ~(my_off_t) 0;
    }
    if (type == WRITE_CACHE)
      info->write_pos=info->rc_request_pos+(seek_offset-info->pos_in_file);
    else  
      info->rc_pos=info->rc_request_pos+(seek_offset-info->pos_in_file);
#ifdef HAVE_AIOWAIT
    my_aiowait(&info->aio_result);		/* Wait for outstanding req */
#endif
  }
  else
  {
    /*
      If we change from WRITE_CACHE to READ_CACHE, assume that everything
      after the current positions should be ignored
    */
    if (info->type == WRITE_CACHE && type == READ_CACHE)
      info->end_of_file=my_b_tell(info);
    /* No need to flush cache if we want to reuse it */
    if ((type != WRITE_CACHE || !clear_cache) && flush_io_cache(info))
      DBUG_RETURN(1);
    if (info->pos_in_file != seek_offset)
    {
      info->pos_in_file=seek_offset;
      info->seek_not_done=1;
    }
    info->rc_request_pos=info->rc_pos=info->buffer;
    if (type == READ_CACHE || type == READ_NET || type == READ_FIFO)
    {
      info->rc_end=info->buffer;		/* Nothing in cache */
    }
    else
    {
      info->rc_end=info->buffer+info->buffer_length-
	(seek_offset & (IO_SIZE-1));
      info->end_of_file= ((type == READ_NET || type == READ_FIFO) ? 0 :
			  ~(my_off_t) 0);
    }
  }
  if (info->type == SEQ_READ_APPEND)
  {
    info->append_read_pos = info->write_pos = info->append_buffer;
  }
  if (!info->write_pos)
    info->write_pos = info->buffer;
  if (!info->write_end)
    info->write_end = info->buffer+info->buffer_length-
      (seek_offset & (IO_SIZE-1));
  info->type=type;
  info->error=0;
  init_read_function(info,type);
  init_write_function(info,type);
#ifdef HAVE_AIOWAIT
  if (type != READ_NET)
  {
    if (use_async_io && ! my_disable_async_io &&
	((ulong) info->buffer_length <
	 (ulong) (info->end_of_file - seek_offset)))
    {
      info->read_length=info->buffer_length/2;
      info->read_function=_my_b_async_read;
    }
  }
  info->inited=0;
#endif
  DBUG_RETURN(0);
} /* reinit_io_cache */



	/*
	  Read buffered. Returns 1 if can't read requested characters
	  This function is only called from the my_b_read() macro
	  when there isn't enough characters in the buffer to
	  satisfy the request.
	  Returns 0 we succeeded in reading all data
	*/

int _my_b_read(register IO_CACHE *info, byte *Buffer, uint Count)
{
  uint length,diff_length,left_length;
  my_off_t max_length, pos_in_file;
  
  if ((left_length=(uint) (info->rc_end-info->rc_pos)))
  {
    dbug_assert(Count >= left_length);	/* User is not using my_b_read() */
    memcpy(Buffer,info->rc_pos, (size_t) (left_length));
    Buffer+=left_length;
    Count-=left_length;
  }
  /* pos_in_file always point on where info->buffer was read */
  pos_in_file=info->pos_in_file+(uint) (info->rc_end - info->buffer);
  if (info->seek_not_done)
  {					/* File touched, do seek */
    VOID(my_seek(info->file,pos_in_file,MY_SEEK_SET,MYF(0)));
    info->seek_not_done=0;
  }
  diff_length=(uint) (pos_in_file & (IO_SIZE-1));
  if (Count >= (uint) (IO_SIZE+(IO_SIZE-diff_length)))
  {					/* Fill first intern buffer */
    uint read_length;
    if (info->end_of_file == pos_in_file)
    {					/* End of file */
      info->error=(int) left_length;
      return 1;
    }
    length=(Count & (uint) ~(IO_SIZE-1))-diff_length;
    if ((read_length=my_read(info->file,Buffer,(uint) length,info->myflags))
	!= (uint) length)
    {
      info->error= read_length == (uint) -1 ? -1 :
	(int) (read_length+left_length);
      return 1;
    }
    Count-=length;
    Buffer+=length;
    pos_in_file+=length;
    left_length+=length;
    diff_length=0;
  }
  max_length=info->read_length-diff_length;
  if (info->type != READ_FIFO &&
      (info->end_of_file - pos_in_file) < max_length)
    max_length = info->end_of_file - pos_in_file;
  if (!max_length)
  {
    if (Count)
    {
      info->error= left_length;		/* We only got this many char */
      return 1;
    }
    length=0;				/* Didn't read any chars */
  }
  else if ((length=my_read(info->file,info->buffer,(uint) max_length,
			   info->myflags)) < Count ||
	   length == (uint) -1)
  {
    if (length != (uint) -1)
      memcpy(Buffer,info->buffer,(size_t) length);
    info->error= length == (uint) -1 ? -1 : (int) (length+left_length);
    return 1;
  }
  info->rc_pos=info->buffer+Count;
  info->rc_end=info->buffer+length;
  info->pos_in_file=pos_in_file;
  memcpy(Buffer,info->buffer,(size_t) Count);
  return 0;
}

/* Do sequential read from the SEQ_READ_APPEND cache
   we do this in three stages:
    - first read from info->buffer
    - then if there are still data to read, try the file descriptor
    - afterwards, if there are still data to read, try append buffer
*/

int _my_b_seq_read(register IO_CACHE *info, byte *Buffer, uint Count)
{
  uint length,diff_length,left_length,save_count;
  my_off_t max_length, pos_in_file;
  save_count=Count;
  /* first, read the regular buffer */
  if ((left_length=(uint) (info->rc_end-info->rc_pos)))
  {
    dbug_assert(Count >= left_length);	/* User is not using my_b_read() */
    memcpy(Buffer,info->rc_pos, (size_t) (left_length));
    Buffer+=left_length;
    Count-=left_length;
  }
  /* pos_in_file always point on where info->buffer was read */
  if ((pos_in_file=info->pos_in_file+(uint) (info->rc_end - info->buffer)) >=
      info->end_of_file)
  {
    info->pos_in_file=pos_in_file;
    goto read_append_buffer;
  }
  /* no need to seek since the read is guaranteed to be sequential */
  diff_length=(uint) (pos_in_file & (IO_SIZE-1));
  
  /* now the second stage begins - read from file descriptor */
  if (Count >= (uint) (IO_SIZE+(IO_SIZE-diff_length)))
  {					/* Fill first intern buffer */
    uint read_length;
    if (info->end_of_file == pos_in_file)
    {					/* End of file */
      goto read_append_buffer;
    }
    length=(Count & (uint) ~(IO_SIZE-1))-diff_length;
    if ((read_length=my_read(info->file,Buffer,(uint) length,info->myflags))
	!= (uint) length)
    {
      if (read_length != (uint)-1)
      {
	Count -= read_length;
	Buffer += read_length;
      }
      goto read_append_buffer;
    }
    Count-=length;
    Buffer+=length;
    pos_in_file+=length;
    left_length+=length;
    diff_length=0;
  }
  max_length=info->read_length-diff_length;
  if ((info->end_of_file - pos_in_file) < max_length)
    max_length = info->end_of_file - pos_in_file;
  if (!max_length)
  {
    if (Count)
    {
      goto read_append_buffer;
    }
    length=0;				/* Didn't read any chars */
  }
  else if ((length=my_read(info->file,info->buffer,(uint) max_length,
			   info->myflags)) < Count ||
	   length == (uint) -1)
  {
    if (length != (uint) -1)
    {
      memcpy(Buffer,info->buffer,(size_t) length);
      Count -= length;
      Buffer += length;
    }
    goto read_append_buffer;
  }
  info->rc_pos=info->buffer+Count;
  info->rc_end=info->buffer+length;
  info->pos_in_file=pos_in_file;
  memcpy(Buffer,info->buffer,(size_t) Count);
  return 0;
read_append_buffer:
  lock_append_buffer(info);
  if (!Count) return 0;
  {
    uint copy_len = (uint)(info->append_read_pos -
			   info->write_pos);
    dbug_assert(info->append_read_pos <= info->write_pos);
    if (copy_len > Count)
      copy_len = Count;
    memcpy(Buffer, info->append_read_pos,
	 copy_len);
    info->append_read_pos += copy_len;
    Count -= copy_len;
    if (Count)
      info->error = save_count - Count; 
  }
  unlock_append_buffer(info);
  return Count ? 1 : 0;
}

#ifdef HAVE_AIOWAIT

int _my_b_async_read(register IO_CACHE *info, byte *Buffer, uint Count)
{
  uint length,read_length,diff_length,left_length,use_length,org_Count;
  my_off_t max_length;
  my_off_t next_pos_in_file;
  byte *read_buffer;

  memcpy(Buffer,info->rc_pos,
	 (size_t) (left_length=(uint) (info->rc_end-info->rc_pos)));
  Buffer+=left_length;
  org_Count=Count;
  Count-=left_length;

  if (info->inited)
  {						/* wait for read block */
    info->inited=0;				/* No more block to read */
    my_aiowait(&info->aio_result);		/* Wait for outstanding req */
    if (info->aio_result.result.aio_errno)
    {
      if (info->myflags & MY_WME)
	my_error(EE_READ, MYF(ME_BELL+ME_WAITTANG),
		 my_filename(info->file),
		 info->aio_result.result.aio_errno);
      my_errno=info->aio_result.result.aio_errno;
      info->error= -1;
      return(1);
    }
    if (! (read_length = (uint) info->aio_result.result.aio_return) ||
	read_length == (uint) -1)
    {
      my_errno=0;				/* For testing */
      info->error= (read_length == (uint) -1 ? -1 :
		    (int) (read_length+left_length));
      return(1);
    }
    info->pos_in_file+=(uint) (info->rc_end - info->rc_request_pos);

    if (info->rc_request_pos != info->buffer)
      info->rc_request_pos=info->buffer;
    else
      info->rc_request_pos=info->buffer+info->read_length;
    info->rc_pos=info->rc_request_pos;
    next_pos_in_file=info->aio_read_pos+read_length;

	/* Check if pos_in_file is changed
	   (_ni_read_cache may have skipped some bytes) */

    if (info->aio_read_pos < info->pos_in_file)
    {						/* Fix if skipped bytes */
      if (info->aio_read_pos + read_length < info->pos_in_file)
      {
	read_length=0;				/* Skipp block */
	next_pos_in_file=info->pos_in_file;
      }
      else
      {
	my_off_t offset= (info->pos_in_file - info->aio_read_pos);
	info->pos_in_file=info->aio_read_pos; /* Whe are here */
	info->rc_pos=info->rc_request_pos+offset;
	read_length-=offset;			/* Bytes left from rc_pos */
      }
    }
#ifndef DBUG_OFF
    if (info->aio_read_pos > info->pos_in_file)
    {
      my_errno=EINVAL;
      return(info->read_length= -1);
    }
#endif
	/* Copy found bytes to buffer */
    length=min(Count,read_length);
    memcpy(Buffer,info->rc_pos,(size_t) length);
    Buffer+=length;
    Count-=length;
    left_length+=length;
    info->rc_end=info->rc_pos+read_length;
    info->rc_pos+=length;
  }
  else
    next_pos_in_file=(info->pos_in_file+ (uint)
		      (info->rc_end - info->rc_request_pos));

	/* If reading large blocks, or first read or read with skipp */
  if (Count)
  {
    if (next_pos_in_file == info->end_of_file)
    {
      info->error=(int) (read_length+left_length);
      return 1;
    }
    VOID(my_seek(info->file,next_pos_in_file,MY_SEEK_SET,MYF(0)));
    read_length=IO_SIZE*2- (uint) (next_pos_in_file & (IO_SIZE-1));
    if (Count < read_length)
    {					/* Small block, read to cache */
      if ((read_length=my_read(info->file,info->rc_request_pos,
			       read_length, info->myflags)) == (uint) -1)
	return info->error= -1;
      use_length=min(Count,read_length);
      memcpy(Buffer,info->rc_request_pos,(size_t) use_length);
      info->rc_pos=info->rc_request_pos+Count;
      info->rc_end=info->rc_request_pos+read_length;
      info->pos_in_file=next_pos_in_file;	/* Start of block in cache */
      next_pos_in_file+=read_length;

      if (Count != use_length)
      {					/* Didn't find hole block */
	if (info->myflags & (MY_WME | MY_FAE | MY_FNABP) && Count != org_Count)
	  my_error(EE_EOFERR, MYF(ME_BELL+ME_WAITTANG),
		   my_filename(info->file),my_errno);
	info->error=(int) (read_length+left_length);
	return 1;
      }
    }
    else
    {						/* Big block, don't cache it */
      if ((read_length=my_read(info->file,Buffer,(uint) Count,info->myflags))
	  != Count)
      {
	info->error= read_length == (uint)  -1 ? -1 : read_length+left_length;
	return 1;
      }
      info->rc_pos=info->rc_end=info->rc_request_pos;
      info->pos_in_file=(next_pos_in_file+=Count);
    }
  }

	/* Read next block with asyncronic io */
  max_length=info->end_of_file - next_pos_in_file;
  diff_length=(next_pos_in_file & (IO_SIZE-1));

  if (max_length > (my_off_t) info->read_length - diff_length)
    max_length= (my_off_t) info->read_length - diff_length;
  if (info->rc_request_pos != info->buffer)
    read_buffer=info->buffer;
  else
    read_buffer=info->buffer+info->read_length;
  info->aio_read_pos=next_pos_in_file;
  if (max_length)
  {
    info->aio_result.result.aio_errno=AIO_INPROGRESS;	/* Marker for test */
    DBUG_PRINT("aioread",("filepos: %ld  length: %ld",
			  (ulong) next_pos_in_file,(ulong) max_length));
    if (aioread(info->file,read_buffer,(int) max_length,
		(my_off_t) next_pos_in_file,MY_SEEK_SET,
		&info->aio_result.result))
    {						/* Skipp async io */
      my_errno=errno;
      DBUG_PRINT("error",("got error: %d, aio_result: %d from aioread, async skipped",
			  errno, info->aio_result.result.aio_errno));
      if (info->rc_request_pos != info->buffer)
      {
	bmove(info->buffer,info->rc_request_pos,
	      (uint) (info->rc_end - info->rc_pos));
	info->rc_request_pos=info->buffer;
	info->rc_pos-=info->read_length;
	info->rc_end-=info->read_length;
      }
      info->read_length=info->buffer_length;	/* Use hole buffer */
      info->read_function=_my_b_read;		/* Use normal IO_READ next */
    }
    else
      info->inited=info->aio_result.pending=1;
  }
  return 0;					/* Block read, async in use */
} /* _my_b_async_read */
#endif


/* Read one byte when buffer is empty */

int _my_b_get(IO_CACHE *info)
{
  byte buff;
  IO_CACHE_CALLBACK pre_read,post_read;
  if ((pre_read = info->pre_read))
    (*pre_read)(info);
  if ((*(info)->read_function)(info,&buff,1))
    return my_b_EOF;
  if ((post_read = info->post_read))
    (*post_read)(info);
  return (int) (uchar) buff;
}

	/* Returns != 0 if error on write */

int _my_b_write(register IO_CACHE *info, const byte *Buffer, uint Count)
{
  uint rest_length,length;

  rest_length=(uint) (info->write_end - info->write_pos);
  memcpy(info->write_pos,Buffer,(size_t) rest_length);
  Buffer+=rest_length;
  Count-=rest_length;
  info->write_pos+=rest_length;
  if (info->pos_in_file+info->buffer_length > info->end_of_file)
  {
    my_errno=errno=EFBIG;
    return info->error = -1;
  }    
  if (flush_io_cache(info))
    return 1;
  if (Count >= IO_SIZE)
  {					/* Fill first intern buffer */
    length=Count & (uint) ~(IO_SIZE-1);
    if (info->seek_not_done)
    {					/* File touched, do seek */
      VOID(my_seek(info->file,info->pos_in_file,MY_SEEK_SET,MYF(0)));
      info->seek_not_done=0;
    }
    if (my_write(info->file,Buffer,(uint) length,info->myflags | MY_NABP))
      return info->error= -1;
    Count-=length;
    Buffer+=length;
    info->pos_in_file+=length;
  }
  memcpy(info->write_pos,Buffer,(size_t) Count);
  info->write_pos+=Count;
  return 0;
}

int _my_b_append(register IO_CACHE *info, const byte *Buffer, uint Count)
{
  uint rest_length,length;

  rest_length=(uint) (info->append_end -
		      info->write_pos);
  memcpy(info->write_pos,Buffer,(size_t) rest_length);
  Buffer+=rest_length;
  Count-=rest_length;
  info->write_pos+=rest_length;
  if (flush_io_cache(info))
    return 1;
  if (Count >= IO_SIZE)
  {					/* Fill first intern buffer */
    length=Count & (uint) ~(IO_SIZE-1);
    if (my_write(info->file,Buffer,(uint) length,info->myflags | MY_NABP))
      return info->error= -1;
    Count-=length;
    Buffer+=length;
  }
  memcpy(info->write_pos,Buffer,(size_t) Count);
  info->write_pos+=Count;
  return 0;
}


/*
  Write a block to disk where part of the data may be inside the record
  buffer.  As all write calls to the data goes through the cache,
  we will never get a seek over the end of the buffer
*/

int my_block_write(register IO_CACHE *info, const byte *Buffer, uint Count,
		   my_off_t pos)
{
  uint length;
  int error=0;

  if (pos < info->pos_in_file)
  {
    /* Of no overlap, write everything without buffering */
    if (pos + Count <= info->pos_in_file)
      return my_pwrite(info->file, Buffer, Count, pos,
		       info->myflags | MY_NABP);
    /* Write the part of the block that is before buffer */
    length= (uint) (info->pos_in_file - pos);
    if (my_pwrite(info->file, Buffer, length, pos, info->myflags | MY_NABP))
      info->error=error=-1;
    Buffer+=length;
    pos+=  length;
    Count-= length;
  }

  /* Check if we want to write inside the used part of the buffer.*/
  length= (uint) (info->rc_end - info->buffer);
  if (pos < info->pos_in_file + length)
  {
    uint offset= (uint) (pos - info->pos_in_file);
    length-=offset;
    if (length > Count)
      length=Count;
    memcpy(info->buffer+offset, Buffer, length);
    Buffer+=length;
    Count-= length;
    /* Fix length of buffer if the new data was larger */
    if (info->buffer+length > info->write_pos)
      info->write_pos=info->buffer+length;
    if (!Count)
      return (error);
  }
  /* Write at the end of the current buffer; This is the normal case */
  if (_my_b_write(info, Buffer, Count))
    error= -1;
  return error;
}

/* avoid warning about empty if body */
#ifdef THREAD
#define IF_APPEND_CACHE if (append_cache)
#else
#define IF_APPEND_CACHE
#endif

	/* Flush write cache */

int flush_io_cache(IO_CACHE *info)
{
  uint length;
  int append_cache;
  DBUG_ENTER("flush_io_cache");
  append_cache = (info->type == SEQ_READ_APPEND);
  if (info->type == WRITE_CACHE || append_cache)
  {
    if (info->file == -1)
    {
      if (real_open_cached_file(info))
	DBUG_RETURN((info->error= -1));
    }
    IF_APPEND_CACHE
      lock_append_buffer(info);
    if (info->write_pos != info->buffer)
    {
      length=(uint) (info->write_pos - info->buffer);
      if (info->seek_not_done)
      {					/* File touched, do seek */
	if (my_seek(info->file,info->pos_in_file,MY_SEEK_SET,MYF(0)) ==
	    MY_FILEPOS_ERROR)
	{
	  IF_APPEND_CACHE
	    unlock_append_buffer(info);
	  DBUG_RETURN((info->error= -1));
	}
	info->seek_not_done=0;
      }
      info->write_pos=info->buffer;
      info->pos_in_file+=length;
      info->write_end=(info->buffer+info->buffer_length-
		    (info->pos_in_file & (IO_SIZE-1)));
      if (append_cache)
      {
	info->append_read_pos = info->buffer;
	info->append_end = info->write_end;
      }
      if (my_write(info->file,info->buffer,length,info->myflags | MY_NABP))
        info->error= -1;
      else
	info->error= 0;
      IF_APPEND_CACHE
        unlock_append_buffer(info);
      DBUG_RETURN(info->error);
    }
  }
#ifdef HAVE_AIOWAIT
  else if (info->type != READ_NET)
  {
    my_aiowait(&info->aio_result);	/* Wait for outstanding req */
    info->inited=0;
  }
#endif
  DBUG_RETURN(0);
}


int end_io_cache(IO_CACHE *info)
{
  int error=0;
  IO_CACHE_CALLBACK pre_close;
  DBUG_ENTER("end_io_cache");
  if((pre_close=info->pre_close))
    (*pre_close)(info);
  if (info->alloced_buffer)
  {
    info->alloced_buffer=0;
    if (info->file != -1)			/* File doesn't exist */
      error=flush_io_cache(info);
    my_free((gptr) info->buffer,MYF(MY_WME));
    info->buffer=info->rc_pos=(byte*) 0;
    info->alloced_buffer = 0;
  }
  DBUG_RETURN(error);
} /* end_io_cache */

#ifdef MAIN
void die(const char* fmt, ...)
{
  va_list va_args;
  va_start(va_args,fmt);
  fprintf(stderr,"Error:");
  vfprintf(stderr, fmt,va_args);
  fprintf(stderr,", errno=%d\n", errno);
  exit(1);
}

int open_file(const char* fname, IO_CACHE* info, int cache_size)
{
  int fd;
  if ((fd=my_open(fname,O_CREAT|O_APPEND|O_RDWR,MYF(MY_WME))) < 0)
    die("Could not open %s", fname);
  if (init_io_cache(info, fd, cache_size, SEQ_READ_APPEND, 0,0,MYF(MY_WME)))
    die("failed in init_io_cache()");
  return fd;
}

void close_file(IO_CACHE* info)
{
  end_io_cache(info);
  my_close(info->file, MYF(MY_WME));
}

int main(int argc, char** argv)
{
  IO_CACHE sra_cache; /* SEQ_READ_APPEND */
  MY_STAT status;
  const char* fname="/tmp/iocache.test";
  int cache_size=16384;
  char llstr_buf[22];
  int max_block,total_bytes=0;
  int i,num_loops=100,error=0;
  char *p;
  char* block, *block_end;
  MY_INIT(argv[0]);
  max_block = cache_size*3;
  if (!(block=(char*)my_malloc(max_block,MYF(MY_WME))))
    die("Not enough memory to allocate test block");
  block_end = block + max_block;
  for (p = block,i=0; p < block_end;i++)
  {
    *p++ = (char)i;
  }
  if (my_stat(fname,&status, MYF(0)) &&
      my_delete(fname,MYF(MY_WME)))
    {
      die("Delete of %s failed, aborting", fname);
    }
  open_file(fname,&sra_cache, cache_size);
  for (i = 0; i < num_loops; i++)
  {
    char buf[4];
    int block_size = abs(rand() % max_block);
    int4store(buf, block_size);
    if (my_b_write(&sra_cache,buf,4) ||
	my_b_write(&sra_cache, block, block_size))
      die("write failed");
    total_bytes += 4+block_size;
  }
  close_file(&sra_cache);
  my_free(block,MYF(MY_WME));
  if (!my_stat(fname,&status,MYF(MY_WME)))
    die("%s failed to stat, but I had just closed it,\
 wonder how that happened");
  printf("Final size of %s is %s, wrote %d bytes\n",fname,
	 llstr(status.st_size,llstr_buf),
	 total_bytes);
  my_delete(fname, MYF(MY_WME));
  /* check correctness of tests */
  if (total_bytes != status.st_size)
  {
    fprintf(stderr,"Not the same number of bytes acutally  in file as bytes \
supposedly written\n");
    error=1;
  }
  exit(error);
  return 0;
}
#endif