/* * Copyright (C) 2013 Freie Universität Berlin. * * This file is subject to the terms and conditions of the GNU Lesser * General Public License v2.1. See the file LICENSE in the top level * directory for more details. */ /** * @{ * @file * @brief Providing implementation for prototypes defined in net_help.h. * @author Oliver Gesch */ #include #include #include "thread.h" #include "net_help.h" uint16_t net_help_csum(uint16_t sum, uint8_t *buf, uint16_t len) { int count = len >> 1; if (count) { uint16_t carry = 0; do { uint16_t t = (*buf << 8) + *(buf + 1); count--; buf += 2; sum += carry; sum += t; carry = (t > sum); } while (count); sum += carry; } if (len & 1) { uint16_t u = (*buf << 8); sum += (*buf << 8); if (sum < u) { sum++; } } return sum; } /** * @} */