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drizzled/internal/my_bit.h
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#ifndef DRIZZLED_INTERNAL_MY_BIT_H
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#define DRIZZLED_INTERNAL_MY_BIT_H
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#ifdef __cplusplus
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extern "C" {
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#endif
 
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namespace drizzled
 
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{
 
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namespace internal
 
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{
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extern const char _my_bits_nbits[256];
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extern const unsigned char _my_bits_reverse_table[256];
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}
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/*
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  Next highest power of two
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  SYNOPSIS
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    my_round_up_to_next_power()
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    v           Value to check
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  RETURN
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    Next or equal power of 2
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    Note: 0 will return 0
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  NOTES
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    Algorithm by Sean Anderson, according to:
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    http://graphics.stanford.edu/~seander/bithacks.html
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    (Orignal code public domain)
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    Comments shows how this works with 01100000000000000000000000001011
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*/
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static inline uint32_t my_round_up_to_next_power(uint32_t v)
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{
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  v--;                  /* 01100000000000000000000000001010 */
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  v|= v >> 1;           /* 01110000000000000000000000001111 */
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  v|= v >> 2;           /* 01111100000000000000000000001111 */
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  v|= v >> 4;           /* 01111111110000000000000000001111 */
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  v|= v >> 8;           /* 01111111111111111100000000001111 */
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  v|= v >> 16;          /* 01111111111111111111111111111111 */
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  return v+1;           /* 10000000000000000000000000000000 */
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}
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static inline uint32_t my_clear_highest_bit(uint32_t v)
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{
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  uint32_t w=v >> 1;
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     _my_bits_reverse_table[(key>>24)      ];
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}
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#ifdef __cplusplus
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}
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#endif
 
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} /* namespace internal */
 
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} /* namespace drizzled */
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#endif /* DRIZZLED_INTERNAL_MY_BIT_H */