~drizzle-trunk/drizzle/development

/* Copyright (C) 2000 MySQL AB

   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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */

/*

  get_ptr_compare(len) returns a pointer to a optimal byte-compare function

  for a array of stringpointer where all strings have size len.

  The bytes are compare as unsigned chars.

  */

#include "mysys_priv.h"

#include <myisampack.h>

static int ptr_compare(size_t *compare_length, uchar **a, uchar **b);

static int ptr_compare_0(size_t *compare_length, uchar **a, uchar **b);

static int ptr_compare_1(size_t *compare_length, uchar **a, uchar **b);

static int ptr_compare_2(size_t *compare_length, uchar **a, uchar **b);

static int ptr_compare_3(size_t *compare_length, uchar **a, uchar **b);

	/* Get a pointer to a optimal byte-compare function for a given size */

qsort2_cmp get_ptr_compare (size_t size)

{

  if (size < 4)

    return (qsort2_cmp) ptr_compare;

  switch (size & 3) {

    case 0: return (qsort2_cmp) ptr_compare_0;

    case 1: return (qsort2_cmp) ptr_compare_1;

    case 2: return (qsort2_cmp) ptr_compare_2;

    case 3: return (qsort2_cmp) ptr_compare_3;

    }

  return 0;					/* Impossible */

}

	/*

	  Compare to keys to see witch is smaller.

	  Loop unrolled to make it quick !!

	*/

#define cmp(N) if (first[N] != last[N]) return (int) first[N] - (int) last[N]

static int ptr_compare(size_t *compare_length, uchar **a, uchar **b)

{

  register int length= *compare_length;

  register uchar *first,*last;

  first= *a; last= *b;

  while (--length)

  {

    if (*first++ != *last++)

      return (int) first[-1] - (int) last[-1];

  }

  return (int) first[0] - (int) last[0];

}

static int ptr_compare_0(size_t *compare_length,uchar **a, uchar **b)

{

  register int length= *compare_length;

  register uchar *first,*last;

  first= *a; last= *b;

 loop:

  cmp(0);

  cmp(1);

  cmp(2);

  cmp(3);

  if ((length-=4))

  {

    first+=4;

    last+=4;

    goto loop;

  }

  return (0);

}

static int ptr_compare_1(size_t *compare_length,uchar **a, uchar **b)

{

  register int length= *compare_length-1;

  register uchar *first,*last;

  first= *a+1; last= *b+1;

  cmp(-1);

 loop:

  cmp(0);

  cmp(1);

  cmp(2);

  cmp(3);

  if ((length-=4))

  {

    first+=4;

    last+=4;

    goto loop;

  }

  return (0);

}

static int ptr_compare_2(size_t *compare_length,uchar **a, uchar **b)

{

  register int length= *compare_length-2;

  register uchar *first,*last;

  first= *a +2 ; last= *b +2;

  cmp(-2);

  cmp(-1);

 loop:

  cmp(0);

  cmp(1);

  cmp(2);

  cmp(3);

  if ((length-=4))

  {

    first+=4;

    last+=4;

    goto loop;

  }

  return (0);

}

static int ptr_compare_3(size_t *compare_length,uchar **a, uchar **b)

{

  register int length= *compare_length-3;

  register uchar *first,*last;

  first= *a +3 ; last= *b +3;

  cmp(-3);

  cmp(-2);

  cmp(-1);

 loop:

  cmp(0);

  cmp(1);

  cmp(2);

  cmp(3);

  if ((length-=4))

  {

    first+=4;

    last+=4;

    goto loop;

  }

  return (0);

}

void my_store_ptr(uchar *buff, size_t pack_length, my_off_t pos)

{

  switch (pack_length) {

#if SIZEOF_OFF_T > 4

  case 8: mi_int8store(buff,pos); break;

  case 7: mi_int7store(buff,pos); break;

  case 6: mi_int6store(buff,pos); break;

  case 5: mi_int5store(buff,pos); break;

#endif

  case 4: mi_int4store(buff,pos); break;

  case 3: mi_int3store(buff,pos); break;

  case 2: mi_int2store(buff,pos); break;

  case 1: buff[0]= (uchar) pos; break;

  default: DBUG_ASSERT(0);

  }

  return;

}

my_off_t my_get_ptr(uchar *ptr, size_t pack_length)

{

  my_off_t pos;

  switch (pack_length) {

#if SIZEOF_OFF_T > 4

  case 8: pos= (my_off_t) mi_uint8korr(ptr); break;

  case 7: pos= (my_off_t) mi_uint7korr(ptr); break;

  case 6: pos= (my_off_t) mi_uint6korr(ptr); break;

  case 5: pos= (my_off_t) mi_uint5korr(ptr); break;

#endif

  case 4: pos= (my_off_t) mi_uint4korr(ptr); break;

  case 3: pos= (my_off_t) mi_uint3korr(ptr); break;

  case 2: pos= (my_off_t) mi_uint2korr(ptr); break;

  case 1: pos= (my_off_t) *(uchar*) ptr; break;

  default: DBUG_ASSERT(0); return 0;

  }

 return pos;

}