path: root/mysys/my_bitmap.c

/* Copyright (C) 2000 MySQL AB
   Copyright (c) 2000, 2011, Oracle and/or its affiliates.
   Copyright (C) 2009- 2011 Monty Program 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 */

/*
  Handling of uchar arrays as large bitmaps.

  API limitations (or, rather asserted safety assumptions,
  to encourage correct programming)

    * the internal size is a set of 32 bit words
    * the number of bits specified in creation can be any number > 0
    * there are THREAD safe versions of most calls called bitmap_lock_*
      many of those are not used and not compiled normally but the code
      already exist for them in an #ifdef:ed part. These can only be used
      if THREAD was specified in bitmap_init

  TODO:
  Make assembler THREAD safe versions of these using test-and-set instructions

  Original version created by Sergei Golubchik 2001 - 2004.
  New version written and test program added and some changes to the interface
  was made by Mikael Ronström 2005, with assistance of Tomas Ulin and Mats
  Kindahl.
*/

#include "mysys_priv.h"
#include <my_bitmap.h>
#include <m_string.h>
#include <my_bit.h>


/* Create a mask of the significant bits for the last byte (1,3,7,..255) */

static inline uchar last_byte_mask(uint bits)
{
  /* Get the number of used bits-1 (0..7) in the last byte */
  unsigned int const used= (bits - 1U) & 7U;
  /* Return bitmask for the significant bits */
  return ((2U << used) - 1);
}

/*
  Create a mask with the upper 'unused' bits set and the lower 'used'
  bits clear. The bits within each byte is stored in big-endian order.
*/

static inline uchar invers_last_byte_mask(uint bits)
{
  return last_byte_mask(bits) ^ 255;
}


void create_last_word_mask(MY_BITMAP *map)
{
  unsigned char const mask= invers_last_byte_mask(map->n_bits);

  /*
    The first bytes are to be set to zero since they represent real  bits
    in the bitvector. The last bytes are set to 0xFF since they  represent
    bytes not used by the bitvector. Finally the last byte contains  bits
    as set by the mask above.
  */
  unsigned char *ptr= (unsigned char*)&map->last_word_mask;

  map->last_word_ptr= map->bitmap + no_words_in_map(map)-1;
  switch (no_bytes_in_map(map) & 3) {
  case 1:
    map->last_word_mask= ~0U;
    ptr[0]= mask;
    return;
  case 2:
    map->last_word_mask= ~0U;
    ptr[0]= 0;
    ptr[1]= mask;
    return;
  case 3:
    map->last_word_mask= 0U;
    ptr[2]= mask;
    ptr[3]= 0xFFU;
    return;
  case 0:
    map->last_word_mask= 0U;
    ptr[3]= mask;
    return;
  }
}


static inline void bitmap_lock(MY_BITMAP *map __attribute__((unused)))
{
#ifdef THREAD
  if (map->mutex)
    pthread_mutex_lock(map->mutex);
#endif
}


static inline void bitmap_unlock(MY_BITMAP *map __attribute__((unused)))
{
#ifdef THREAD
  if (map->mutex)
    pthread_mutex_unlock(map->mutex);
#endif
}


my_bool bitmap_init(MY_BITMAP *map, my_bitmap_map *buf, uint n_bits,
		    my_bool thread_safe __attribute__((unused)))
{
  DBUG_ENTER("bitmap_init");
  if (!buf)
  {
    uint size_in_bytes= bitmap_buffer_size(n_bits);
    uint extra= 0;
#ifdef THREAD
    if (thread_safe)
    {
      size_in_bytes= ALIGN_SIZE(size_in_bytes);
      extra= sizeof(pthread_mutex_t);
    }
    map->mutex= 0;
#endif
    if (!(buf= (my_bitmap_map*) my_malloc(size_in_bytes+extra, MYF(MY_WME))))
      DBUG_RETURN(1);
#ifdef THREAD
    if (thread_safe)
    {
      map->mutex= (pthread_mutex_t *) ((char*) buf + size_in_bytes);
      pthread_mutex_init(map->mutex, MY_MUTEX_INIT_FAST);
    }
#endif
  }
#ifdef THREAD
  else
  {
    DBUG_ASSERT(thread_safe == 0);
  }
#endif

  map->bitmap= buf;
  map->n_bits= n_bits;
  create_last_word_mask(map);
  bitmap_clear_all(map);
  DBUG_RETURN(0);
}


void bitmap_free(MY_BITMAP *map)
{
  DBUG_ENTER("bitmap_free");
  if (map->bitmap)
  {
#ifdef THREAD
    if (map->mutex)
      pthread_mutex_destroy(map->mutex);
#endif
    my_free((char*) map->bitmap, MYF(0));
    map->bitmap=0;
  }
  DBUG_VOID_RETURN;
}


/*
  test if bit already set and set it if it was not (thread unsafe method)

  SYNOPSIS
    bitmap_fast_test_and_set()
    MAP   bit map struct
    BIT   bit number

  RETURN
    0    bit was not set
    !=0  bit was set
*/

my_bool bitmap_fast_test_and_set(MY_BITMAP *map, uint bitmap_bit)
{
  uchar *value= ((uchar*) map->bitmap) + (bitmap_bit / 8);
  uchar bit= 1 << ((bitmap_bit) & 7);
  uchar res= (*value) & bit;
  *value|= bit;
  return res;
}


/*
  test if bit already set and set it if it was not (thread safe method)

  SYNOPSIS
    bitmap_fast_test_and_set()
    map          bit map struct
    bitmap_bit   bit number

  RETURN
    0    bit was not set
    !=0  bit was set
*/

my_bool bitmap_test_and_set(MY_BITMAP *map, uint bitmap_bit)
{
  my_bool res;
  DBUG_ASSERT(map->bitmap && bitmap_bit < map->n_bits);
  bitmap_lock(map);
  res= bitmap_fast_test_and_set(map, bitmap_bit);
  bitmap_unlock(map);
  return res;
}

/*
  test if bit already set and clear it if it was set(thread unsafe method)

  SYNOPSIS
    bitmap_fast_test_and_set()
    MAP   bit map struct
    BIT   bit number

  RETURN
    0    bit was not set
    !=0  bit was set
*/

my_bool bitmap_fast_test_and_clear(MY_BITMAP *map, uint bitmap_bit)
{
  uchar *byte= (uchar*) map->bitmap + (bitmap_bit / 8);
  uchar bit= 1 << ((bitmap_bit) & 7);
  uchar res= (*byte) & bit;
  *byte&= ~bit;
  return res;
}


my_bool bitmap_test_and_clear(MY_BITMAP *map, uint bitmap_bit)
{
  my_bool res;
  DBUG_ASSERT(map->bitmap && bitmap_bit < map->n_bits);
  bitmap_lock(map);
  res= bitmap_fast_test_and_clear(map, bitmap_bit);
  bitmap_unlock(map);
  return res;
}


uint bitmap_set_next(MY_BITMAP *map)
{
  uint bit_found;
  DBUG_ASSERT(map->bitmap);
  if ((bit_found= bitmap_get_first(map)) != MY_BIT_NONE)
    bitmap_set_bit(map, bit_found);
  return bit_found;
}


void bitmap_set_prefix(MY_BITMAP *map, uint prefix_size)
{
  uint prefix_bytes, prefix_bits, d;
  uchar *m= (uchar *)map->bitmap;

  DBUG_ASSERT(map->bitmap &&
	      (prefix_size <= map->n_bits || prefix_size == (uint) ~0));
  set_if_smaller(prefix_size, map->n_bits);
  if ((prefix_bytes= prefix_size / 8))
    memset(m, 0xff, prefix_bytes);
  m+= prefix_bytes;
  if ((prefix_bits= prefix_size & 7))
  {
    *m++= (1 << prefix_bits)-1;
    prefix_bytes++;
  }
  if ((d= no_bytes_in_map(map)-prefix_bytes))
    bzero(m, d);
}


my_bool bitmap_is_prefix(const MY_BITMAP *map, uint prefix_size)
{
  uint prefix_bits= prefix_size % 32;
  my_bitmap_map *word_ptr= map->bitmap, last_word;
  my_bitmap_map *end_prefix= word_ptr + prefix_size / 32;
  DBUG_ASSERT(word_ptr && prefix_size <= map->n_bits);

  /* 1: Words that should be filled with 1 */
  for (; word_ptr < end_prefix; word_ptr++)
    if (*word_ptr != 0xFFFFFFFF)
      return FALSE;

  last_word= *map->last_word_ptr & ~map->last_word_mask;

  /* 2: Word which contains the end of the prefix (if any) */
  if (prefix_bits)
  {
    if (word_ptr == map->last_word_ptr)
      return uint4korr((uchar*)&last_word) == (uint32)((1 << prefix_bits) - 1);
    if (uint4korr((uchar*)word_ptr) != (uint32)((1 << prefix_bits) - 1))
      return FALSE;
    word_ptr++;
  }

  /* 3: Words that should be filled with 0 */
  for (; word_ptr < map->last_word_ptr; word_ptr++)
    if (*word_ptr != 0)
      return FALSE;

  /*
    We can end up here in two situations:
    1) We went through the whole bitmap in step 1. This will happen if the
       whole bitmap is filled with 1 and prefix_size is a multiple of 32
       (i.e. the prefix does not end in the middle of a word).
       In this case word_ptr will be larger than map->last_word_ptr.
    2) We have gone through steps 1-3 and just need to check that also
       the last word is 0.
  */
  return word_ptr > map->last_word_ptr || last_word == 0;
}


my_bool bitmap_is_set_all(const MY_BITMAP *map)
{
  my_bitmap_map *data_ptr= map->bitmap;
  my_bitmap_map *end= map->last_word_ptr;

  for (; data_ptr < end; data_ptr++)
    if (*data_ptr != 0xFFFFFFFF)
      return FALSE;
  return (*data_ptr | map->last_word_mask) == 0xFFFFFFFF;
}


my_bool bitmap_is_clear_all(const MY_BITMAP *map)
{
  my_bitmap_map *data_ptr= map->bitmap;
  my_bitmap_map *end= map->last_word_ptr;

  for (; data_ptr < end; data_ptr++)
    if (*data_ptr)
      return FALSE;
  return (*data_ptr & ~map->last_word_mask) == 0;
}

/* Return TRUE if map1 is a subset of map2 */

my_bool bitmap_is_subset(const MY_BITMAP *map1, const MY_BITMAP *map2)
{
  my_bitmap_map *m1= map1->bitmap, *m2= map2->bitmap, *end;

  DBUG_ASSERT(map1->bitmap && map2->bitmap &&
              map1->n_bits==map2->n_bits);

  end= map1->last_word_ptr;
  while (m1 < end)
  {
    if ((*m1++) & ~(*m2++))
      return 0;
  }
  /* here both maps have the same number of bits - see assert above */
  return ((*m1 & ~*m2 & ~map1->last_word_mask) ? 0 : 1);
}

/* True if bitmaps has any common bits */

my_bool bitmap_is_overlapping(const MY_BITMAP *map1, const MY_BITMAP *map2)
{
  my_bitmap_map *m1= map1->bitmap, *m2= map2->bitmap, *end;

  DBUG_ASSERT(map1->bitmap && map2->bitmap &&
              map1->n_bits==map2->n_bits);

  end= map1->last_word_ptr;
  while (m1 < end)
  {
    if ((*m1++) & (*m2++))
      return 1;
  }
  /* here both maps have the same number of bits - see assert above */
  return ((*m1 & *m2 & ~map1->last_word_mask) ? 1 : 0);
}


void bitmap_intersect(MY_BITMAP *map, const MY_BITMAP *map2)
{
  my_bitmap_map *to= map->bitmap, *from= map2->bitmap, *end;
  uint len= no_words_in_map(map), len2 = no_words_in_map(map2);

  DBUG_ASSERT(map->bitmap && map2->bitmap);

  end= to+min(len,len2);
  while (to < end)
    *to++ &= *from++;

  if (len2 <= len)
  {
    to[-1]&= ~map2->last_word_mask; /* Clear last not relevant bits */
    end+= len-len2;
    while (to < end)
      *to++= 0;
  }
}

/* True if union of bitmaps have all bits set */

my_bool bitmap_union_is_set_all(const MY_BITMAP *map1, const MY_BITMAP *map2)
{
  my_bitmap_map *m1= map1->bitmap, *m2= map2->bitmap, *end;

  DBUG_ASSERT(map1->bitmap && map2->bitmap &&
              map1->n_bits==map2->n_bits);
  end= map1->last_word_ptr;
  while ( m1 < end)
    if ((*m1++ | *m2++) != 0xFFFFFFFF)
      return FALSE;
  /* here both maps have the same number of bits - see assert above */
  return ((*m1 | *m2 | map1->last_word_mask) != 0xFFFFFFFF);
}



/*
  Set/clear all bits above a bit.

  SYNOPSIS
    bitmap_set_above()
    map                  RETURN The bitmap to change.
    from_byte                   The bitmap buffer byte offset to start with.
    use_bit                     The bit value (1/0) to use for all upper bits.

  NOTE
    You can only set/clear full bytes.
    The function is meant for the situation that you copy a smaller bitmap
    to a bigger bitmap. Bitmap lengths are always multiple of eigth (the
    size of a byte). Using 'from_byte' saves multiplication and division
    by eight during parameter passing.

  RETURN
    void
*/

void bitmap_set_above(MY_BITMAP *map, uint from_byte, uint use_bit)
{
  uchar use_byte= use_bit ? 0xff : 0;
  uchar *to= (uchar *)map->bitmap + from_byte;
  uchar *end= (uchar *)map->bitmap + (map->n_bits+7)/8;

  while (to < end)
    *to++= use_byte;
}


void bitmap_subtract(MY_BITMAP *map, const MY_BITMAP *map2)
{
  my_bitmap_map *to= map->bitmap, *from= map2->bitmap, *end;
  DBUG_ASSERT(map->bitmap && map2->bitmap &&
              map->n_bits==map2->n_bits);

  end= map->last_word_ptr;

  while (to <= end)
    *to++ &= ~(*from++);
}


void bitmap_union(MY_BITMAP *map, const MY_BITMAP *map2)
{
  my_bitmap_map *to= map->bitmap, *from= map2->bitmap, *end;

  DBUG_ASSERT(map->bitmap && map2->bitmap &&
              map->n_bits==map2->n_bits);
  end= map->last_word_ptr;

  while (to <= end)
    *to++ |= *from++;
}


void bitmap_xor(MY_BITMAP *map, const MY_BITMAP *map2)
{
  my_bitmap_map *to= map->bitmap, *from= map2->bitmap, *end= map->last_word_ptr;
  DBUG_ASSERT(map->bitmap && map2->bitmap &&
              map->n_bits==map2->n_bits);
  while (to <= end)
    *to++ ^= *from++;
}


void bitmap_invert(MY_BITMAP *map)
{
  my_bitmap_map *to= map->bitmap, *end;

  DBUG_ASSERT(map->bitmap);
  end= map->last_word_ptr;

  while (to <= end)
    *to++ ^= 0xFFFFFFFF;
}


uint bitmap_bits_set(const MY_BITMAP *map)
{
  my_bitmap_map *data_ptr= map->bitmap;
  my_bitmap_map *end= map->last_word_ptr;
  uint res= 0;
  DBUG_ASSERT(map->bitmap);

  for (; data_ptr < end; data_ptr++)
    res+= my_count_bits_uint32(*data_ptr);

  /*Reset last bits to zero*/
  res+= my_count_bits_uint32(*map->last_word_ptr & ~map->last_word_mask);
  return res;
}


void bitmap_copy(MY_BITMAP *map, const MY_BITMAP *map2)
{
  my_bitmap_map *to= map->bitmap, *from= map2->bitmap, *end;
  DBUG_ASSERT(map->bitmap && map2->bitmap &&
              map->n_bits==map2->n_bits);
  end= map->last_word_ptr;

  while (to <= end)
    *to++ = *from++;
}


uint bitmap_get_first_set(const MY_BITMAP *map)
{
  uchar *byte_ptr;
  uint i,j,k;
  my_bitmap_map *data_ptr, *end= map->last_word_ptr;

  DBUG_ASSERT(map->bitmap);
  data_ptr= map->bitmap;

  for (i=0; data_ptr < end; data_ptr++, i++)
    if (*data_ptr)
      goto found;
  if (!(*data_ptr & ~map->last_word_mask))
    return MY_BIT_NONE;

found:
  {
    byte_ptr= (uchar*)data_ptr;
    for (j=0; ; j++, byte_ptr++)
    {
      if (*byte_ptr)
      {
        for (k=0; ; k++)
        {
          if (*byte_ptr & (1 << k))
            return (i*32) + (j*8) + k;
        }
      }
    }
  }
  DBUG_ASSERT(0);
  return MY_BIT_NONE;                           /* Impossible */
}


uint bitmap_get_first(const MY_BITMAP *map)
{
  uchar *byte_ptr;
  uint i,j,k;
  my_bitmap_map *data_ptr, *end= map->last_word_ptr;

  DBUG_ASSERT(map->bitmap);
  data_ptr= map->bitmap;
  *map->last_word_ptr|= map->last_word_mask;

  for (i=0; data_ptr < end; data_ptr++, i++)
    if (*data_ptr != 0xFFFFFFFF)
      goto found;
  if ((*data_ptr | map->last_word_mask) == 0xFFFFFFFF)
    return MY_BIT_NONE;

found:
  {
    byte_ptr= (uchar*)data_ptr;
    for (j=0; ; j++, byte_ptr++)
    {
      if (*byte_ptr != 0xFF)
      {
        for (k=0; ; k++)
        {
          if (!(*byte_ptr & (1 << k)))
            return (i*32) + (j*8) + k;
        }
      }
    }
  }
  DBUG_ASSERT(0);
  return MY_BIT_NONE;                           /* Impossible */
}


uint bitmap_lock_set_next(MY_BITMAP *map)
{
  uint bit_found;
  bitmap_lock(map);
  bit_found= bitmap_set_next(map);
  bitmap_unlock(map);
  return bit_found;
}


void bitmap_lock_clear_bit(MY_BITMAP *map, uint bitmap_bit)
{
  bitmap_lock(map);
  DBUG_ASSERT(map->bitmap && bitmap_bit < map->n_bits);
  bitmap_clear_bit(map, bitmap_bit);
  bitmap_unlock(map);
}


#ifdef NOT_USED
my_bool bitmap_lock_is_prefix(const MY_BITMAP *map, uint prefix_size)
{
  my_bool res;
  bitmap_lock((MY_BITMAP *)map);
  res= bitmap_is_prefix(map, prefix_size);
  bitmap_unlock((MY_BITMAP *)map);
  return res;
}


void bitmap_lock_set_all(MY_BITMAP *map)
{
  bitmap_lock(map);
  bitmap_set_all(map);
  bitmap_unlock(map);
}


void bitmap_lock_clear_all(MY_BITMAP *map)
{
  bitmap_lock(map);
  bitmap_clear_all(map);
  bitmap_unlock(map);
}


void bitmap_lock_set_prefix(MY_BITMAP *map, uint prefix_size)
{
  bitmap_lock(map);
  bitmap_set_prefix(map, prefix_size);
  bitmap_unlock(map);
}


my_bool bitmap_lock_is_clear_all(const MY_BITMAP *map)
{
  uint res;
  bitmap_lock((MY_BITMAP *)map);
  res= bitmap_is_clear_all(map);
  bitmap_unlock((MY_BITMAP *)map);
  return res;
}


my_bool bitmap_lock_is_set_all(const MY_BITMAP *map)
{
  uint res;
  bitmap_lock((MY_BITMAP *)map);
  res= bitmap_is_set_all(map);
  bitmap_unlock((MY_BITMAP *)map);
  return res;
}


my_bool bitmap_lock_is_set(const MY_BITMAP *map, uint bitmap_bit)
{
  my_bool res;
  DBUG_ASSERT(map->bitmap && bitmap_bit < map->n_bits);
  bitmap_lock((MY_BITMAP *)map);
  res= bitmap_is_set(map, bitmap_bit);
  bitmap_unlock((MY_BITMAP *)map);
  return res;
}


my_bool bitmap_lock_is_subset(const MY_BITMAP *map1, const MY_BITMAP *map2)
{
  uint res;
  bitmap_lock((MY_BITMAP *)map1);
  bitmap_lock((MY_BITMAP *)map2);
  res= bitmap_is_subset(map1, map2);
  bitmap_unlock((MY_BITMAP *)map2);
  bitmap_unlock((MY_BITMAP *)map1);
  return res;
}


my_bool bitmap_lock_cmp(const MY_BITMAP *map1, const MY_BITMAP *map2)
{
  uint res;

  DBUG_ASSERT(map1->bitmap && map2->bitmap &&
              map1->n_bits==map2->n_bits);
  bitmap_lock((MY_BITMAP *)map1);
  bitmap_lock((MY_BITMAP *)map2);
  res= bitmap_cmp(map1, map2);
  bitmap_unlock((MY_BITMAP *)map2);
  bitmap_unlock((MY_BITMAP *)map1);
  return res;
}


void bitmap_lock_intersect(MY_BITMAP *map, const MY_BITMAP *map2)
{
  bitmap_lock(map);
  bitmap_lock((MY_BITMAP *)map2);
  bitmap_intersect(map, map2);
  bitmap_unlock((MY_BITMAP *)map2);
  bitmap_unlock(map);
}


void bitmap_lock_subtract(MY_BITMAP *map, const MY_BITMAP *map2)
{
  bitmap_lock(map);
  bitmap_lock((MY_BITMAP *)map2);
  bitmap_subtract(map, map2);
  bitmap_unlock((MY_BITMAP *)map2);
  bitmap_unlock(map);
}


void bitmap_lock_union(MY_BITMAP *map, const MY_BITMAP *map2)
{
  bitmap_lock(map);
  bitmap_lock((MY_BITMAP *)map2);
  bitmap_union(map, map2);
  bitmap_unlock((MY_BITMAP *)map2);
  bitmap_unlock(map);
}


/*
  SYNOPSIS
    bitmap_bits_set()
      map
  RETURN
    Number of set bits in the bitmap.
*/
uint bitmap_lock_bits_set(const MY_BITMAP *map)
{
  uint res;
  bitmap_lock((MY_BITMAP *)map);
  DBUG_ASSERT(map->bitmap);
  res= bitmap_bits_set(map);
  bitmap_unlock((MY_BITMAP *)map);
  return res;
}


/* 
  SYNOPSIS
    bitmap_get_first()
      map
  RETURN 
    Number of first unset bit in the bitmap or MY_BIT_NONE if all bits are set.
*/
uint bitmap_lock_get_first(const MY_BITMAP *map)
{
  uint res;
  bitmap_lock((MY_BITMAP*)map);
  res= bitmap_get_first(map);
  bitmap_unlock((MY_BITMAP*)map);
  return res;
}


uint bitmap_lock_get_first_set(const MY_BITMAP *map)
{
  uint res;
  bitmap_lock((MY_BITMAP*)map);
  res= bitmap_get_first_set(map);
  bitmap_unlock((MY_BITMAP*)map);
  return res;
}


void bitmap_lock_set_bit(MY_BITMAP *map, uint bitmap_bit)
{
  DBUG_ASSERT(map->bitmap && bitmap_bit < map->n_bits);
  bitmap_lock(map);
  bitmap_set_bit(map, bitmap_bit);
  bitmap_unlock(map);
}


void bitmap_lock_flip_bit(MY_BITMAP *map, uint bitmap_bit)
{
  DBUG_ASSERT(map->bitmap && bitmap_bit < map->n_bits);
  bitmap_lock(map);
  bitmap_flip_bit(map, bitmap_bit);
  bitmap_unlock(map);
}
#endif /* NOT_USED */