| // 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. |
| |
| // Date: Tue Feb 25 23:43:39 CST 2014 |
| |
| // Provide functions to get/set bits of an integral array. These functions |
| // are not threadsafe because operations on different bits may modify a same |
| // integer. |
| |
| #ifndef BUTIL_BIT_ARRAY_H |
| #define BUTIL_BIT_ARRAY_H |
| |
| #include <stdint.h> |
| |
| namespace butil { |
| |
| // Create an array with at least |nbit| bits. The array is not cleared. |
| inline uint64_t* bit_array_malloc(size_t nbit) |
| { |
| if (!nbit) { |
| return NULL; |
| } |
| return (uint64_t*)malloc((nbit + 63 ) / 64 * 8/*different from /8*/); |
| } |
| |
| // Set bit 0 ~ nbit-1 of |array| to be 0 |
| inline void bit_array_clear(uint64_t* array, size_t nbit) |
| { |
| const size_t off = (nbit >> 6); |
| memset(array, 0, off * 8); |
| const size_t last = (off << 6); |
| if (last != nbit) { |
| array[off] &= ~((((uint64_t)1) << (nbit - last)) - 1); |
| } |
| } |
| |
| // Set i-th bit (from left, counting from 0) of |array| to be 1 |
| inline void bit_array_set(uint64_t* array, size_t i) |
| { |
| const size_t off = (i >> 6); |
| array[off] |= (((uint64_t)1) << (i - (off << 6))); |
| } |
| |
| // Set i-th bit (from left, counting from 0) of |array| to be 0 |
| inline void bit_array_unset(uint64_t* array, size_t i) |
| { |
| const size_t off = (i >> 6); |
| array[off] &= ~(((uint64_t)1) << (i - (off << 6))); |
| } |
| |
| // Get i-th bit (from left, counting from 0) of |array| |
| inline uint64_t bit_array_get(const uint64_t* array, size_t i) |
| { |
| const size_t off = (i >> 6); |
| return (array[off] & (((uint64_t)1) << (i - (off << 6)))); |
| } |
| |
| // Find index of first 1-bit from bit |begin| to |end| in |array|. |
| // Returns |end| if all bits are 0. |
| // This function is of O(nbit) complexity. |
| inline size_t bit_array_first1(const uint64_t* array, size_t begin, size_t end) |
| { |
| size_t off1 = (begin >> 6); |
| const size_t first = (off1 << 6); |
| if (first != begin) { |
| const uint64_t v = |
| array[off1] & ~((((uint64_t)1) << (begin - first)) - 1); |
| if (v) { |
| return std::min(first + __builtin_ctzl(v), end); |
| } |
| ++off1; |
| } |
| |
| const size_t off2 = (end >> 6); |
| for (size_t i = off1; i < off2; ++i) { |
| if (array[i]) { |
| return i * 64 + __builtin_ctzl(array[i]); |
| } |
| } |
| const size_t last = (off2 << 6); |
| if (last != end && array[off2]) { |
| return std::min(last + __builtin_ctzl(array[off2]), end); |
| } |
| return end; |
| } |
| |
| } // end namespace butil |
| |
| #endif // BUTIL_BIT_ARRAY_H |