/* * Copyright (c)2013-2020 ZeroTier, Inc. * * Use of this software is governed by the Business Source License included * in the LICENSE.TXT file in the project's root directory. * * Change Date: 2024-01-01 * * On the date above, in accordance with the Business Source License, use * of this software will be governed by version 2.0 of the Apache License. */ /****/ #ifndef ZT_RINGBUFFER_H #define ZT_RINGBUFFER_H #include <typeinfo> #include <cstdint> #include <stdlib.h> #include <memory.h> #include <algorithm> #include <math.h> namespace ZeroTier { /** * A circular buffer * * For fast handling of continuously-evolving variables (such as path quality metrics). * Using this, we can maintain longer sliding historical windows for important path * metrics without the need for potentially expensive calls to memcpy/memmove. * * Some basic statistical functionality is implemented here in an attempt * to reduce the complexity of code needed to interact with this type of buffer. */ template <class T,size_t S> class RingBuffer { private: T buf[S]; size_t begin; size_t end; bool wrap; public: RingBuffer() : begin(0), end(0), wrap(false) { memset(buf,0,sizeof(T)*S); } /** * @return A pointer to the underlying buffer */ inline T *get_buf() { return buf + begin; } /** * Adjust buffer index pointer as if we copied data in * @param n Number of elements to copy in * @return Number of elements we copied in */ inline size_t produce(size_t n) { n = std::min(n, getFree()); if (n == 0) { return n; } const size_t first_chunk = std::min(n, S - end); end = (end + first_chunk) % S; if (first_chunk < n) { const size_t second_chunk = n - first_chunk; end = (end + second_chunk) % S; } if (begin == end) { wrap = true; } return n; } /** * Fast erase, O(1). * Merely reset the buffer pointer, doesn't erase contents */ inline void reset() { consume(count()); } /** * adjust buffer index pointer as if we copied data out * @param n Number of elements we copied from the buffer * @return Number of elements actually available from the buffer */ inline size_t consume(size_t n) { n = std::min(n, count()); if (n == 0) { return n; } if (wrap) { wrap = false; } const size_t first_chunk = std::min(n, S - begin); begin = (begin + first_chunk) % S; if (first_chunk < n) { const size_t second_chunk = n - first_chunk; begin = (begin + second_chunk) % S; } return n; } /** * @param data Buffer that is to be written to the ring * @param n Number of elements to write to the buffer */ inline size_t write(const T * data, size_t n) { n = std::min(n, getFree()); if (n == 0) { return n; } const size_t first_chunk = std::min(n, S - end); memcpy(buf + end, data, first_chunk * sizeof(T)); end = (end + first_chunk) % S; if (first_chunk < n) { const size_t second_chunk = n - first_chunk; memcpy(buf + end, data + first_chunk, second_chunk * sizeof(T)); end = (end + second_chunk) % S; } if (begin == end) { wrap = true; } return n; } /** * Place a single value on the buffer. If the buffer is full, consume a value first. * * @param value A single value to be placed in the buffer */ inline void push(const T value) { if (count() == S) { consume(1); } const size_t first_chunk = std::min((size_t)1, S - end); *(buf + end) = value; end = (end + first_chunk) % S; if (begin == end) { wrap = true; } } /** * @return The most recently pushed element on the buffer */ inline T get_most_recent() { return *(buf + end); } /** * @param dest Destination buffer * @param n Size (in terms of number of elements) of the destination buffer * @return Number of elements read from the buffer */ inline size_t read(T *dest,size_t n) { n = std::min(n, count()); if (n == 0) { return n; } if (wrap) { wrap = false; } const size_t first_chunk = std::min(n, S - begin); memcpy(dest, buf + begin, first_chunk * sizeof(T)); begin = (begin + first_chunk) % S; if (first_chunk < n) { const size_t second_chunk = n - first_chunk; memcpy(dest + first_chunk, buf + begin, second_chunk * sizeof(T)); begin = (begin + second_chunk) % S; } return n; } /** * Return how many elements are in the buffer, O(1). * * @return The number of elements in the buffer */ inline size_t count() { if (end == begin) { return wrap ? S : 0; } else if (end > begin) { return end - begin; } else { return S + end - begin; } } /** * @return The number of slots that are unused in the buffer */ inline size_t getFree() { return S - count(); } /** * @return The arithmetic mean of the contents of the buffer */ inline float mean() { size_t iterator = begin; float subtotal = 0; size_t curr_cnt = count(); for (size_t i=0; i<curr_cnt; i++) { iterator = (iterator + S - 1) % curr_cnt; subtotal += (float)*(buf + iterator); } return curr_cnt ? subtotal / (float)curr_cnt : 0; } /** * @return The arithmetic mean of the most recent 'n' elements of the buffer */ inline float mean(size_t n) { n = n < S ? n : S; size_t iterator = begin; float subtotal = 0; size_t curr_cnt = count(); for (size_t i=0; i<n; i++) { iterator = (iterator + S - 1) % curr_cnt; subtotal += (float)*(buf + iterator); } return curr_cnt ? subtotal / (float)curr_cnt : 0; } /** * @return The sum of the contents of the buffer */ inline float sum() { size_t iterator = begin; float total = 0; size_t curr_cnt = count(); for (size_t i=0; i<curr_cnt; i++) { iterator = (iterator + S - 1) % curr_cnt; total += (float)*(buf + iterator); } return total; } /** * @return The sample standard deviation of element values */ inline float stddev() { return sqrt(variance()); } /** * @return The variance of element values */ inline float variance() { size_t iterator = begin; float cached_mean = mean(); size_t curr_cnt = count(); T sum_of_squared_deviations = 0; for (size_t i=0; i<curr_cnt; i++) { iterator = (iterator + S - 1) % curr_cnt; float deviation = (buf[i] - cached_mean); sum_of_squared_deviations += (T)(deviation*deviation); } float variance = (float)sum_of_squared_deviations / (float)(S - 1); return variance; } /** * @return The number of elements of zero value */ inline size_t zeroCount() { size_t iterator = begin; size_t zeros = 0; size_t curr_cnt = count(); for (size_t i=0; i<curr_cnt; i++) { iterator = (iterator + S - 1) % curr_cnt; if (*(buf + iterator) == 0) { zeros++; } } return zeros; } /** * @param value Value to match against in buffer * @return The number of values held in the ring buffer which match a given value */ inline size_t countValue(T value) { size_t iterator = begin; size_t cnt = 0; size_t curr_cnt = count(); for (size_t i=0; i<curr_cnt; i++) { iterator = (iterator + S - 1) % curr_cnt; if (*(buf + iterator) == value) { cnt++; } } return cnt; } /** * Print the contents of the buffer */ /* inline void dump() { size_t iterator = begin; for (size_t i=0; i<S; i++) { iterator = (iterator + S - 1) % S; if (typeid(T) == typeid(int)) { fprintf(stderr, "buf[%2zu]=%2d\n", iterator, (int)*(buf + iterator)); } else { fprintf(stderr, "buf[%2zu]=%2f\n", iterator, (float)*(buf + iterator)); } } } */ }; } // namespace ZeroTier #endif