/* * Copyright (c) 2018 Apple Inc. All rights reserved. * * @APPLE_OSREFERENCE_LICENSE_HEADER_START@ * * This file contains Original Code and/or Modifications of Original Code * as defined in and that are subject to the Apple Public Source License * Version 2.0 (the 'License'). You may not use this file except in * compliance with the License. The rights granted to you under the License * may not be used to create, or enable the creation or redistribution of, * unlawful or unlicensed copies of an Apple operating system, or to * circumvent, violate, or enable the circumvention or violation of, any * terms of an Apple operating system software license agreement. * * Please obtain a copy of the License at * http://www.opensource.apple.com/apsl/ and read it before using this file. * * The Original Code and all software distributed under the License are * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. * Please see the License for the specific language governing rights and * limitations under the License. * * @APPLE_OSREFERENCE_LICENSE_HEADER_END@ */ #ifndef _OS_HASH_H_ #define _OS_HASH_H_ #if PRIVATE #include <os/base.h> __BEGIN_DECLS /*! * @function os_hash_jenkins * * @brief * The original Jenkins "one at a time" hash. * * @discussion * TBD: There may be some value to unrolling here, * depending on the architecture. * * @param data * The address of the data to hash. * * @param length * The length of the data to hash * * @returns * The jenkins hash for this data. */ static inline uint32_t os_hash_jenkins(const void *data, size_t length) { const uint8_t *key = (const uint8_t *)data; uint32_t hash = 0; for (size_t i = 0; i < length; i++) { hash += key[i]; hash += (hash << 10); hash ^= (hash >> 6); } hash += (hash << 3); hash ^= (hash >> 11); hash += (hash << 15); return hash; } /*! * @function os_hash_kernel_pointer * * @brief * Hashes a pointer from a zone. * * @discussion * This is a really cheap and fast hash that will behave well for pointers * allocated by the kernel. * * This should be not used for untrusted pointer values from userspace, * or cases when the pointer is somehow under the control of userspace. * * This hash function utilizes knowledge about the span of the kernel * address space and inherent alignment of zalloc/kalloc. * * @param pointer * The pointer to hash. * * @returns * The hash for this pointer. */ static inline uint32_t os_hash_kernel_pointer(const void *pointer) { uintptr_t key = (uintptr_t)pointer >> 4; key *= 0x5052acdb; return (uint32_t)key ^ __builtin_bswap32((uint32_t)key); } __END_DECLS #endif // PRIVATE #endif // _OS_HASH_H_