/**************************************************************************** * libs/libc/string/lib_ffsl.c * * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. The * ASF licenses this file to you under the Apache License, Version 2.0 (the * "License"); you may not use this file except in compliance with the * License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the * License for the specific language governing permissions and limitations * under the License. * ****************************************************************************/ /**************************************************************************** * Included Files ****************************************************************************/ #include #include /**************************************************************************** * Pre-processor Definitions ****************************************************************************/ #define NBITS (8 * sizeof(unsigned long)) /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: ffsl * * Description: * The ffsl() function will find the first bit set (beginning with the * least significant bit) in j, and return the index of that bit. Bits are * numbered starting at one (the least significant bit). * * Returned Value: * The ffsl() function will return the index of the first bit set. If j is * 0, then ffsl() will return 0. * ****************************************************************************/ int ffsl(long j) { int ret = 0; if (j != 0) { #ifdef CONFIG_HAVE_BUILTIN_CTZ /* Count trailing zeros function can be used to implement ffs. */ ret = __builtin_ctzl(j) + 1; #else unsigned long value = (unsigned long)j; int bitno; for (bitno = 1; bitno <= NBITS; bitno++, value >>= 1) { if ((value & 1) != 0) { ret = bitno; break; } } #endif } return ret; }