1 /* 2 * util/rfc_1982.c - RFC 1982 Serial Number Arithmetic 3 * 4 * Copyright (c) 2023, NLnet Labs. All rights reserved. 5 * 6 * This software is open source. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 12 * Redistributions of source code must retain the above copyright notice, 13 * this list of conditions and the following disclaimer. 14 * 15 * Redistributions in binary form must reproduce the above copyright notice, 16 * this list of conditions and the following disclaimer in the documentation 17 * and/or other materials provided with the distribution. 18 * 19 * Neither the name of the NLNET LABS nor the names of its contributors may 20 * be used to endorse or promote products derived from this software without 21 * specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 24 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 25 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 26 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 27 * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 28 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED 29 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 30 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 31 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 32 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 33 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 34 */ 35 36 /** 37 * \file 38 * 39 * This file contains functions for RFC 1982 serial number arithmetic. 40 */ 41 #include "config.h" 42 #include "util/rfc_1982.h" 43 44 int 45 compare_1982(uint32_t a, uint32_t b) 46 { 47 /* for 32 bit values */ 48 const uint32_t cutoff = ((uint32_t) 1 << (32 - 1)); 49 50 if (a == b) { 51 return 0; 52 } else if ((a < b && b - a < cutoff) || (a > b && a - b > cutoff)) { 53 return -1; 54 } else { 55 return 1; 56 } 57 } 58 59 uint32_t 60 subtract_1982(uint32_t a, uint32_t b) 61 { 62 /* for 32 bit values */ 63 const uint32_t cutoff = ((uint32_t) 1 << (32 - 1)); 64 65 if(a == b) 66 return 0; 67 if(a < b && b - a < cutoff) { 68 return b-a; 69 } 70 if(a > b && a - b > cutoff) { 71 return ((uint32_t)0xffffffff) - (a-b-1); 72 } 73 /* wrong case, b smaller than a */ 74 return 0; 75 } 76