/* Copyright (c) 2007, 2011, Oracle and/or its affiliates. Copyright (c) 2009, 2017, MariaDB Corporation. 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 02110-1301 USA */ #ifndef MY_BIT_INCLUDED #define MY_BIT_INCLUDED #include /* Some useful bit functions */ C_MODE_START extern const uchar _my_bits_reverse_table[256]; /* Find smallest X in 2^X >= value This can be used to divide a number with value by doing a shift instead */ static inline uint my_bit_log2(ulong value) { uint bit; for (bit=0 ; value > 1 ; value>>=1, bit++) ; return bit; } /* Count bits in 32bit integer Algorithm by Sean Anderson, according to: http://graphics.stanford.edu/~seander/bithacks.html under "Counting bits set, in parallel" (Orignal code public domain). */ static inline uint my_count_bits_uint32(uint32 v) { v = v - ((v >> 1) & 0x55555555); v = (v & 0x33333333) + ((v >> 2) & 0x33333333); return (((v + (v >> 4)) & 0xF0F0F0F) * 0x1010101) >> 24; } static inline uint my_count_bits(ulonglong x) { return my_count_bits_uint32((uint32)x) + my_count_bits_uint32((uint32)(x >> 32)); } /* Next highest power of two SYNOPSIS my_round_up_to_next_power() v Value to check RETURN Next or equal power of 2 Note: 0 will return 0 NOTES Algorithm by Sean Anderson, according to: http://graphics.stanford.edu/~seander/bithacks.html (Orignal code public domain) Comments shows how this works with 01100000000000000000000000001011 */ static inline uint32 my_round_up_to_next_power(uint32 v) { v--; /* 01100000000000000000000000001010 */ v|= v >> 1; /* 01110000000000000000000000001111 */ v|= v >> 2; /* 01111100000000000000000000001111 */ v|= v >> 4; /* 01111111110000000000000000001111 */ v|= v >> 8; /* 01111111111111111100000000001111 */ v|= v >> 16; /* 01111111111111111111111111111111 */ return v+1; /* 10000000000000000000000000000000 */ } static inline uint32 my_clear_highest_bit(uint32 v) { uint32 w=v >> 1; w|= w >> 1; w|= w >> 2; w|= w >> 4; w|= w >> 8; w|= w >> 16; return v & w; } static inline uint32 my_reverse_bits(uint32 key) { return ((uint32)_my_bits_reverse_table[ key & 255] << 24) | ((uint32)_my_bits_reverse_table[(key>> 8) & 255] << 16) | ((uint32)_my_bits_reverse_table[(key>>16) & 255] << 8) | (uint32)_my_bits_reverse_table[(key>>24) ]; } /* a number with the n lowest bits set an overflow-safe version of (1 << n) - 1 */ static inline uint32 my_set_bits(int n) { return (((1UL << (n - 1)) - 1) << 1) | 1; } C_MODE_END #endif /* MY_BIT_INCLUDED */