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  • Committer: Brian Aker
  • Date: 2010-01-22 00:53:13 UTC
  • Revision ID: brian@gaz-20100122005313-jmizcbcdi1lt4tcx
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drizzled/internal/my_bit.h
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/* -*- mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; -*-
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 *  vim:expandtab:shiftwidth=2:tabstop=2:smarttab:
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 *
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 *  Copyright (C) 2008, 2009 Sun Microsystems, Inc.
 
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 *  Copyright (C) 2008, 2009 Sun Microsystems
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 *
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 *  This program is free software; you can redistribute it and/or modify
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 *  it under the terms of the GNU General Public License as published by
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#ifndef DRIZZLED_INTERNAL_MY_BIT_H
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#define DRIZZLED_INTERNAL_MY_BIT_H
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namespace drizzled
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{
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namespace internal
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{
 
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#ifdef __cplusplus
 
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extern "C" {
 
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#endif
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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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} /* namespace internal */
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} /* namespace drizzled */
 
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#ifdef __cplusplus
 
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}
 
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#endif
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#endif /* DRIZZLED_INTERNAL_MY_BIT_H */