/* 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, version 2.0,
   as published by the Free Software Foundation.

   This program is also distributed with certain software (including
   but not limited to OpenSSL) that is licensed under separate terms,
   as designated in a particular file or component or in included license
   documentation.  The authors of MySQL hereby grant you an additional
   permission to link the program and your derivative works with the
   separately licensed software that they have included with MySQL.

   Without limiting anything contained in the foregoing, this file,
   which is part of C Driver for MySQL (Connector/C), is also subject to the
   Universal FOSS Exception, version 1.0, a copy of which can be found at
   http://oss.oracle.com/licenses/universal-foss-exception.

   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, version 2.0, 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 */

/*
  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>

#ifdef __sun
/*
 * On Solaris, memcmp() is normally faster than the unrolled ptr_compare_N
 * functions, as memcmp() is usually a platform-specific implementation
 * written in assembler, provided in /usr/lib/libc/libc_hwcap*.so.1.
 * This implementation is also usually faster than the built-in memcmp
 * supplied by GCC, so it is recommended to build with "-fno-builtin-memcmp"
 * in CFLAGS if building with GCC on Solaris.
 */

#include <string.h>

static int native_compare(size_t *length, unsigned char **a, unsigned char **b)
{
  return memcmp(*a, *b, *length);
}

#else	/* __sun */

/**
  Special case for ORDER BY / GROUP BY CHAR(0) NOT NULL
 */
static
int ptr_compare_zero_length(size_t *compare_length MY_ATTRIBUTE((unused)),
                            uchar **a MY_ATTRIBUTE((unused)),
                            uchar **b MY_ATTRIBUTE((unused)))
{
  return 0;
}
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);
#endif	/* __sun */

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

#ifdef __sun
qsort2_cmp get_ptr_compare (size_t size MY_ATTRIBUTE((unused)))
{
  return (qsort2_cmp) native_compare;
}
#else
qsort2_cmp get_ptr_compare (size_t size)
{
  if (size == 0)
    return (qsort2_cmp) ptr_compare_zero_length;
  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 */
}
#endif /* __sun */


	/*
	  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]

#ifndef __sun

static int ptr_compare(size_t *compare_length, uchar **a, uchar **b)
{
  reg3 int length= *compare_length;
  reg1 uchar *first,*last;

  DBUG_ASSERT(length > 0);
  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)
{
  reg3 int length= *compare_length;
  reg1 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)
{
  reg3 int length= *compare_length-1;
  reg1 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)
{
  reg3 int length= *compare_length-2;
  reg1 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)
{
  reg3 int length= *compare_length-3;
  reg1 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);
}

#endif /* !__sun */

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;
}

