| Current File : //usr/include/mysql/server/private/sql_bitmap.h |
/* Copyright (c) 2003, 2013, Oracle and/or its affiliates
Copyright (c) 2009, 2013, 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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335 USA */
/*
Implementation of a bitmap type.
The idea with this is to be able to handle any constant number of bits but
also be able to use 32 or 64 bits bitmaps very efficiently
*/
#ifndef SQL_BITMAP_INCLUDED
#define SQL_BITMAP_INCLUDED
#include <my_sys.h>
#include <my_bitmap.h>
#include <my_bit.h>
/* An iterator to quickly walk over bits in ulonglong bitmap. */
class Table_map_iterator
{
ulonglong bmp;
public:
Table_map_iterator(ulonglong t): bmp(t){}
uint next_bit()
{
if (!bmp)
return BITMAP_END;
uint bit= my_find_first_bit(bmp);
bmp &= ~(1ULL << bit);
return bit;
}
int operator++(int) { return next_bit(); }
enum { BITMAP_END= 64 };
};
template <uint width> class Bitmap
{
/*
Workaround GCC optimizer bug (generating SSE instuctions on unaligned data)
*/
#if defined (__GNUC__) && defined(__x86_64__) && (__GNUC__ < 6) && !defined(__clang__)
#define NEED_GCC_NO_SSE_WORKAROUND
#endif
#ifdef NEED_GCC_NO_SSE_WORKAROUND
#pragma GCC push_options
#pragma GCC target ("no-sse")
#endif
private:
static const int BITS_PER_ELEMENT= sizeof(ulonglong) * 8;
static const int ARRAY_ELEMENTS= (width + BITS_PER_ELEMENT - 1) / BITS_PER_ELEMENT;
static const ulonglong ALL_BITS_SET= ULLONG_MAX;
ulonglong buffer[ARRAY_ELEMENTS];
uint bit_index(uint n) const
{
DBUG_ASSERT(n < width);
return ARRAY_ELEMENTS == 1 ? 0 : n / BITS_PER_ELEMENT;
}
ulonglong bit_mask(uint n) const
{
DBUG_ASSERT(n < width);
return ARRAY_ELEMENTS == 1 ? 1ULL << n : 1ULL << (n % BITS_PER_ELEMENT);
}
ulonglong last_element_mask(int n) const
{
DBUG_ASSERT(n % BITS_PER_ELEMENT != 0);
return bit_mask(n) - 1;
}
public:
/*
The default constructor does nothing.
The caller is supposed to either zero the memory
or to call set_all()/clear_all()/set_prefix()
to initialize bitmap.
*/
Bitmap() = default;
explicit Bitmap(uint prefix)
{
set_prefix(prefix);
}
void init(uint prefix)
{
set_prefix(prefix);
}
uint length() const
{
return width;
}
void set_bit(uint n)
{
buffer[bit_index(n)] |= bit_mask(n);
}
void clear_bit(uint n)
{
buffer[bit_index(n)] &= ~bit_mask(n);
}
bool is_set(uint n) const
{
return buffer[bit_index(n)] & bit_mask(n);
}
void set_prefix(uint prefix_size)
{
set_if_smaller(prefix_size, width);
size_t idx= prefix_size / BITS_PER_ELEMENT;
for (size_t i= 0; i < idx; i++)
buffer[i]= ALL_BITS_SET;
if (prefix_size % BITS_PER_ELEMENT)
buffer[idx++]= last_element_mask(prefix_size);
for (size_t i= idx; i < ARRAY_ELEMENTS; i++)
buffer[i]= 0;
}
bool is_prefix(uint prefix_size) const
{
DBUG_ASSERT(prefix_size <= width);
size_t idx= prefix_size / BITS_PER_ELEMENT;
for (size_t i= 0; i < idx; i++)
if (buffer[i] != ALL_BITS_SET)
return false;
if (prefix_size % BITS_PER_ELEMENT)
if (buffer[idx++] != last_element_mask(prefix_size))
return false;
for (size_t i= idx; i < ARRAY_ELEMENTS; i++)
if (buffer[i] != 0)
return false;
return true;
}
void set_all()
{
if (width % BITS_PER_ELEMENT)
set_prefix(width);
else if (ARRAY_ELEMENTS > 1)
memset(buffer, 0xff, sizeof(buffer));
else
buffer[0] = ALL_BITS_SET;
}
void clear_all()
{
if (ARRAY_ELEMENTS > 1)
memset(buffer, 0, sizeof(buffer));
else
buffer[0]= 0;
}
void intersect(const Bitmap& map2)
{
for (size_t i= 0; i < ARRAY_ELEMENTS; i++)
buffer[i] &= map2.buffer[i];
}
private:
/*
Intersect with a bitmap represented as as longlong.
In addition, pad the rest of the bitmap with 0 or 1 bits
depending on pad_with_ones parameter.
*/
void intersect_and_pad(ulonglong map2buff, bool pad_with_ones)
{
buffer[0] &= map2buff;
for (size_t i= 1; i < ARRAY_ELEMENTS; i++)
buffer[i]= pad_with_ones ? ALL_BITS_SET : 0;
if (ARRAY_ELEMENTS > 1 && (width % BITS_PER_ELEMENT) && pad_with_ones)
buffer[ARRAY_ELEMENTS - 1]= last_element_mask(width);
}
public:
void intersect(ulonglong map2buff)
{
intersect_and_pad(map2buff, 0);
}
/* Use highest bit for all bits above first element. */
void intersect_extended(ulonglong map2buff)
{
intersect_and_pad(map2buff, (map2buff & (1ULL << 63)));
}
void subtract(const Bitmap& map2)
{
for (size_t i= 0; i < ARRAY_ELEMENTS; i++)
buffer[i] &= ~(map2.buffer[i]);
}
void merge(const Bitmap& map2)
{
for (size_t i= 0; i < ARRAY_ELEMENTS; i++)
buffer[i] |= map2.buffer[i];
}
bool is_clear_all() const
{
for (size_t i= 0; i < ARRAY_ELEMENTS; i++)
if (buffer[i])
return false;
return true;
}
bool is_subset(const Bitmap& map2) const
{
for (size_t i= 0; i < ARRAY_ELEMENTS; i++)
if (buffer[i] & ~(map2.buffer[i]))
return false;
return true;
}
bool is_overlapping(const Bitmap& map2) const
{
for (size_t i= 0; i < ARRAY_ELEMENTS; i++)
if (buffer[i] & map2.buffer[i])
return true;
return false;
}
bool operator==(const Bitmap& map2) const
{
if (ARRAY_ELEMENTS > 1)
return !memcmp(buffer,map2.buffer,sizeof(buffer));
return buffer[0] == map2.buffer[0];
}
bool operator!=(const Bitmap& map2) const
{
return !(*this == map2);
}
/*
Print hexadecimal representation of bitmap.
Truncate trailing zeros.
*/
char *print(char *buf) const
{
size_t last; /*index of the last non-zero element, or 0. */
for (last= ARRAY_ELEMENTS - 1; last && !buffer[last]; last--){}
const int HEX_DIGITS_PER_ELEMENT= BITS_PER_ELEMENT / 4;
for (size_t i= 0; i < last; i++)
{
ulonglong num = buffer[i];
uint shift = BITS_PER_ELEMENT - 4;
size_t pos= i * HEX_DIGITS_PER_ELEMENT;
for (size_t j= 0; j < HEX_DIGITS_PER_ELEMENT; j++)
{
buf[pos + j]= _dig_vec_upper[(num >> shift) & 0xf];
shift += 4;
}
}
longlong2str(buffer[last], buf, 16);
return buf;
}
ulonglong to_ulonglong() const
{
return buffer[0];
}
uint bits_set()
{
uint res= 0;
for (size_t i= 0; i < ARRAY_ELEMENTS; i++)
res += my_count_bits(buffer[i]);
return res;
}
class Iterator
{
const Bitmap& map;
uint offset;
Table_map_iterator tmi;
public:
Iterator(const Bitmap<width>& map2) : map(map2), offset(0), tmi(map2.buffer[0]) {}
int operator++(int)
{
for (;;)
{
int nextbit= tmi++;
if (nextbit != Table_map_iterator::BITMAP_END)
return offset + nextbit;
if (offset + BITS_PER_ELEMENT >= map.length())
return BITMAP_END;
offset += BITS_PER_ELEMENT;
tmi= Table_map_iterator(map.buffer[offset / BITS_PER_ELEMENT]);
}
}
enum { BITMAP_END = width };
};
#ifdef NEED_GCC_NO_SSE_WORKAROUND
#pragma GCC pop_options
#undef NEED_GCC_NO_SSE_WORKAROUND
#endif
};
typedef Bitmap<MAX_INDEXES> key_map; /* Used for finding keys */
#endif /* SQL_BITMAP_INCLUDED */