prlog2.c (735B)
1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ 2 /* This Source Code Form is subject to the terms of the Mozilla Public 3 * License, v. 2.0. If a copy of the MPL was not distributed with this 4 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ 5 6 #include "prbit.h" 7 8 /* 9 ** Compute the log of the least power of 2 greater than or equal to n 10 */ 11 PR_IMPLEMENT(PRIntn) PR_CeilingLog2(PRUint32 n) { 12 PRIntn log2; 13 PR_CEILING_LOG2(log2, n); 14 return log2; 15 } 16 17 /* 18 ** Compute the log of the greatest power of 2 less than or equal to n. 19 ** This really just finds the highest set bit in the word. 20 */ 21 PR_IMPLEMENT(PRIntn) PR_FloorLog2(PRUint32 n) { 22 PRIntn log2; 23 PR_FLOOR_LOG2(log2, n); 24 return log2; 25 }