* Copyright (c) 2017 Apple Inc. All rights reserved.
* 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.
* extern uint32_t os_cpu_in_cksum(const void *data, uint32_t len,
* uint32_t initial_sum);
* input :
* data : starting address
* len : byte stream length
* initial_sum : 32-bit sum
* output :
* This function returns the partial 16-bit checksum accumulated in
* a 32-bit variable (withouth 1's complement); caller is responsible
* for folding the 32-bit sum into 16-bit and performinng the 1's
* complement if applicable