bitops.h

/*
Copyright 2013-present Barefoot Networks, Inc.
 
Licensed 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.
*/
 
#ifndef LIB_BITOPS_H_
#define LIB_BITOPS_H_
 
#include <limits.h>
 
#include "bitvec.h"
 
namespace P4 {
 
static inline unsigned bitcount(unsigned v) {
#if defined(__GNUC__) || defined(__clang__)
    unsigned rv = __builtin_popcount(v);
#else
    unsigned rv = 0;
    while (v) {
        v &= v - 1;
        ++rv;
    }
#endif
    return rv;
}
 
static inline int floor_log2(unsigned v) {
    int rv = -1;
#if defined(__GNUC__) || defined(__clang__)
    if (v) rv = CHAR_BIT * sizeof(unsigned) - __builtin_clz(v) - 1;
#else
    while (v) {
        rv++;
        v >>= 1;
    }
#endif
    return rv;
}
 
static inline int ceil_log2(unsigned v) { return v ? floor_log2(v - 1) + 1 : -1; }
 
static inline unsigned bitmask2bytemask(const bitvec &a) {
    int max = a.max().index();
    if (max < 0) return 0;
    unsigned rv = 0;
    for (unsigned i = 0; i <= max / 8U; i++)
        if (a.getrange(i * 8, 8)) rv |= 1 << i;
    return rv;
}
 
}  // namespace P4
 
#endif /* LIB_BITOPS_H_ */