init
This commit is contained in:
blue-lemon0104
272
db_include/port/pg_bitutils.h
Executable file
272
db_include/port/pg_bitutils.h
Executable file
@@ -0,0 +1,272 @@
|
||||
/*-------------------------------------------------------------------------
|
||||
*
|
||||
* pg_bitutils.h
|
||||
* Miscellaneous functions for bit-wise operations.
|
||||
*
|
||||
*
|
||||
* Copyright (c) 2019-2021, PostgreSQL Global Development Group
|
||||
*
|
||||
* src/include/port/pg_bitutils.h
|
||||
*
|
||||
*-------------------------------------------------------------------------
|
||||
*/
|
||||
#ifndef PG_BITUTILS_H
|
||||
#define PG_BITUTILS_H
|
||||
|
||||
#ifndef FRONTEND
|
||||
extern PGDLLIMPORT const uint8 pg_leftmost_one_pos[256];
|
||||
extern PGDLLIMPORT const uint8 pg_rightmost_one_pos[256];
|
||||
extern PGDLLIMPORT const uint8 pg_number_of_ones[256];
|
||||
#else
|
||||
extern const uint8 pg_leftmost_one_pos[256];
|
||||
extern const uint8 pg_rightmost_one_pos[256];
|
||||
extern const uint8 pg_number_of_ones[256];
|
||||
#endif
|
||||
|
||||
/*
|
||||
* pg_leftmost_one_pos32
|
||||
* Returns the position of the most significant set bit in "word",
|
||||
* measured from the least significant bit. word must not be 0.
|
||||
*/
|
||||
static inline int
|
||||
pg_leftmost_one_pos32(uint32 word)
|
||||
{
|
||||
#ifdef HAVE__BUILTIN_CLZ
|
||||
Assert(word != 0);
|
||||
|
||||
return 31 - __builtin_clz(word);
|
||||
#else
|
||||
int shift = 32 - 8;
|
||||
|
||||
Assert(word != 0);
|
||||
|
||||
while ((word >> shift) == 0)
|
||||
shift -= 8;
|
||||
|
||||
return shift + pg_leftmost_one_pos[(word >> shift) & 255];
|
||||
#endif /* HAVE__BUILTIN_CLZ */
|
||||
}
|
||||
|
||||
/*
|
||||
* pg_leftmost_one_pos64
|
||||
* As above, but for a 64-bit word.
|
||||
*/
|
||||
static inline int
|
||||
pg_leftmost_one_pos64(uint64 word)
|
||||
{
|
||||
#ifdef HAVE__BUILTIN_CLZ
|
||||
Assert(word != 0);
|
||||
|
||||
#if defined(HAVE_LONG_INT_64)
|
||||
return 63 - __builtin_clzl(word);
|
||||
#elif defined(HAVE_LONG_LONG_INT_64)
|
||||
return 63 - __builtin_clzll(word);
|
||||
#else
|
||||
#error must have a working 64-bit integer datatype
|
||||
#endif
|
||||
#else /* !HAVE__BUILTIN_CLZ */
|
||||
int shift = 64 - 8;
|
||||
|
||||
Assert(word != 0);
|
||||
|
||||
while ((word >> shift) == 0)
|
||||
shift -= 8;
|
||||
|
||||
return shift + pg_leftmost_one_pos[(word >> shift) & 255];
|
||||
#endif /* HAVE__BUILTIN_CLZ */
|
||||
}
|
||||
|
||||
/*
|
||||
* pg_rightmost_one_pos32
|
||||
* Returns the position of the least significant set bit in "word",
|
||||
* measured from the least significant bit. word must not be 0.
|
||||
*/
|
||||
static inline int
|
||||
pg_rightmost_one_pos32(uint32 word)
|
||||
{
|
||||
#ifdef HAVE__BUILTIN_CTZ
|
||||
Assert(word != 0);
|
||||
|
||||
return __builtin_ctz(word);
|
||||
#else
|
||||
int result = 0;
|
||||
|
||||
Assert(word != 0);
|
||||
|
||||
while ((word & 255) == 0)
|
||||
{
|
||||
word >>= 8;
|
||||
result += 8;
|
||||
}
|
||||
result += pg_rightmost_one_pos[word & 255];
|
||||
return result;
|
||||
#endif /* HAVE__BUILTIN_CTZ */
|
||||
}
|
||||
|
||||
/*
|
||||
* pg_rightmost_one_pos64
|
||||
* As above, but for a 64-bit word.
|
||||
*/
|
||||
static inline int
|
||||
pg_rightmost_one_pos64(uint64 word)
|
||||
{
|
||||
#ifdef HAVE__BUILTIN_CTZ
|
||||
Assert(word != 0);
|
||||
|
||||
#if defined(HAVE_LONG_INT_64)
|
||||
return __builtin_ctzl(word);
|
||||
#elif defined(HAVE_LONG_LONG_INT_64)
|
||||
return __builtin_ctzll(word);
|
||||
#else
|
||||
#error must have a working 64-bit integer datatype
|
||||
#endif
|
||||
#else /* !HAVE__BUILTIN_CTZ */
|
||||
int result = 0;
|
||||
|
||||
Assert(word != 0);
|
||||
|
||||
while ((word & 255) == 0)
|
||||
{
|
||||
word >>= 8;
|
||||
result += 8;
|
||||
}
|
||||
result += pg_rightmost_one_pos[word & 255];
|
||||
return result;
|
||||
#endif /* HAVE__BUILTIN_CTZ */
|
||||
}
|
||||
|
||||
/*
|
||||
* pg_nextpower2_32
|
||||
* Returns the next higher power of 2 above 'num', or 'num' if it's
|
||||
* already a power of 2.
|
||||
*
|
||||
* 'num' mustn't be 0 or be above PG_UINT32_MAX / 2 + 1.
|
||||
*/
|
||||
static inline uint32
|
||||
pg_nextpower2_32(uint32 num)
|
||||
{
|
||||
Assert(num > 0 && num <= PG_UINT32_MAX / 2 + 1);
|
||||
|
||||
/*
|
||||
* A power 2 number has only 1 bit set. Subtracting 1 from such a number
|
||||
* will turn on all previous bits resulting in no common bits being set
|
||||
* between num and num-1.
|
||||
*/
|
||||
if ((num & (num - 1)) == 0)
|
||||
return num; /* already power 2 */
|
||||
|
||||
return ((uint32) 1) << (pg_leftmost_one_pos32(num) + 1);
|
||||
}
|
||||
|
||||
/*
|
||||
* pg_nextpower2_64
|
||||
* Returns the next higher power of 2 above 'num', or 'num' if it's
|
||||
* already a power of 2.
|
||||
*
|
||||
* 'num' mustn't be 0 or be above PG_UINT64_MAX / 2 + 1.
|
||||
*/
|
||||
static inline uint64
|
||||
pg_nextpower2_64(uint64 num)
|
||||
{
|
||||
Assert(num > 0 && num <= PG_UINT64_MAX / 2 + 1);
|
||||
|
||||
/*
|
||||
* A power 2 number has only 1 bit set. Subtracting 1 from such a number
|
||||
* will turn on all previous bits resulting in no common bits being set
|
||||
* between num and num-1.
|
||||
*/
|
||||
if ((num & (num - 1)) == 0)
|
||||
return num; /* already power 2 */
|
||||
|
||||
return ((uint64) 1) << (pg_leftmost_one_pos64(num) + 1);
|
||||
}
|
||||
|
||||
/*
|
||||
* pg_nextpower2_size_t
|
||||
* Returns the next higher power of 2 above 'num', for a size_t input.
|
||||
*/
|
||||
#if SIZEOF_SIZE_T == 4
|
||||
#define pg_nextpower2_size_t(num) pg_nextpower2_32(num)
|
||||
#else
|
||||
#define pg_nextpower2_size_t(num) pg_nextpower2_64(num)
|
||||
#endif
|
||||
|
||||
/*
|
||||
* pg_prevpower2_32
|
||||
* Returns the next lower power of 2 below 'num', or 'num' if it's
|
||||
* already a power of 2.
|
||||
*
|
||||
* 'num' mustn't be 0.
|
||||
*/
|
||||
static inline uint32
|
||||
pg_prevpower2_32(uint32 num)
|
||||
{
|
||||
return ((uint32) 1) << pg_leftmost_one_pos32(num);
|
||||
}
|
||||
|
||||
/*
|
||||
* pg_prevpower2_64
|
||||
* Returns the next lower power of 2 below 'num', or 'num' if it's
|
||||
* already a power of 2.
|
||||
*
|
||||
* 'num' mustn't be 0.
|
||||
*/
|
||||
static inline uint64
|
||||
pg_prevpower2_64(uint64 num)
|
||||
{
|
||||
return ((uint64) 1) << pg_leftmost_one_pos64(num);
|
||||
}
|
||||
|
||||
/*
|
||||
* pg_prevpower2_size_t
|
||||
* Returns the next lower power of 2 below 'num', for a size_t input.
|
||||
*/
|
||||
#if SIZEOF_SIZE_T == 4
|
||||
#define pg_prevpower2_size_t(num) pg_prevpower2_32(num)
|
||||
#else
|
||||
#define pg_prevpower2_size_t(num) pg_prevpower2_64(num)
|
||||
#endif
|
||||
|
||||
/*
|
||||
* pg_ceil_log2_32
|
||||
* Returns equivalent of ceil(log2(num))
|
||||
*/
|
||||
static inline uint32
|
||||
pg_ceil_log2_32(uint32 num)
|
||||
{
|
||||
if (num < 2)
|
||||
return 0;
|
||||
else
|
||||
return pg_leftmost_one_pos32(num - 1) + 1;
|
||||
}
|
||||
|
||||
/*
|
||||
* pg_ceil_log2_64
|
||||
* Returns equivalent of ceil(log2(num))
|
||||
*/
|
||||
static inline uint64
|
||||
pg_ceil_log2_64(uint64 num)
|
||||
{
|
||||
if (num < 2)
|
||||
return 0;
|
||||
else
|
||||
return pg_leftmost_one_pos64(num - 1) + 1;
|
||||
}
|
||||
|
||||
/* Count the number of one-bits in a uint32 or uint64 */
|
||||
extern int (*pg_popcount32) (uint32 word);
|
||||
extern int (*pg_popcount64) (uint64 word);
|
||||
|
||||
/* Count the number of one-bits in a byte array */
|
||||
extern uint64 pg_popcount(const char *buf, int bytes);
|
||||
|
||||
/*
|
||||
* Rotate the bits of "word" to the right by n bits.
|
||||
*/
|
||||
static inline uint32
|
||||
pg_rotate_right32(uint32 word, int n)
|
||||
{
|
||||
return (word >> n) | (word << (sizeof(word) * BITS_PER_BYTE - n));
|
||||
}
|
||||
|
||||
#endif /* PG_BITUTILS_H */
|
||||
Reference in New Issue
Block a user