bits.c revision 84f697c5e30565823619abaaeb57164c789d4b66
02c335c23bf5fa225a467c19f2c063fb0dc7b8c3Timo Sirainen/* Copyright (c) 2001-2016 Dovecot authors, see the included COPYING file */
3637a2ad3b2ead17efd5591f73effd3b140d8d2dPhil Carmody
3637a2ad3b2ead17efd5591f73effd3b140d8d2dPhil Carmody#include "lib.h"
3637a2ad3b2ead17efd5591f73effd3b140d8d2dPhil Carmody
3637a2ad3b2ead17efd5591f73effd3b140d8d2dPhil Carmodysize_t nearest_power(size_t num)
3637a2ad3b2ead17efd5591f73effd3b140d8d2dPhil Carmody{
3637a2ad3b2ead17efd5591f73effd3b140d8d2dPhil Carmody size_t n = 1;
3637a2ad3b2ead17efd5591f73effd3b140d8d2dPhil Carmody
3637a2ad3b2ead17efd5591f73effd3b140d8d2dPhil Carmody i_assert(num <= ((size_t)1 << (CHAR_BIT*sizeof(size_t) - 1)));
3637a2ad3b2ead17efd5591f73effd3b140d8d2dPhil Carmody
3637a2ad3b2ead17efd5591f73effd3b140d8d2dPhil Carmody while (n < num) n <<= 1;
3637a2ad3b2ead17efd5591f73effd3b140d8d2dPhil Carmody return n;
3637a2ad3b2ead17efd5591f73effd3b140d8d2dPhil Carmody}
3637a2ad3b2ead17efd5591f73effd3b140d8d2dPhil Carmody
84f697c5e30565823619abaaeb57164c789d4b66Phil Carmody#if __GNUC__ > 2
84f697c5e30565823619abaaeb57164c789d4b66Phil Carmody/* Lucky you, it's all inline intrinsics */
84f697c5e30565823619abaaeb57164c789d4b66Phil Carmody#else
3637a2ad3b2ead17efd5591f73effd3b140d8d2dPhil Carmodyunsigned int bits_required8(uint8_t num)
3637a2ad3b2ead17efd5591f73effd3b140d8d2dPhil Carmody{
3637a2ad3b2ead17efd5591f73effd3b140d8d2dPhil Carmody int ret = 0;
3637a2ad3b2ead17efd5591f73effd3b140d8d2dPhil Carmody if (num > 0xf) { ret += 4; num >>= 4; }
3637a2ad3b2ead17efd5591f73effd3b140d8d2dPhil Carmody if (num > 0x3) { ret += 2; num >>= 2; }
3637a2ad3b2ead17efd5591f73effd3b140d8d2dPhil Carmody num &= ~(num>>1); /* 3->2, else unchanged */
3637a2ad3b2ead17efd5591f73effd3b140d8d2dPhil Carmody return ret + num;
3637a2ad3b2ead17efd5591f73effd3b140d8d2dPhil Carmody}
84f697c5e30565823619abaaeb57164c789d4b66Phil Carmody#endif