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/**************************************************************************/
/* */
/* Copyright (c) Microsoft Corporation. All rights reserved. */
/* */
/* This software is licensed under the Microsoft Software License */
/* Terms for Microsoft Azure RTOS. Full text of the license can be */
/* found in the LICENSE file at https://aka.ms/AzureRTOS_EULA */
/* and in the root directory of this software. */
/* */
/**************************************************************************/
/**************************************************************************/
/**************************************************************************/
/** */
/** FileX Component */
/** */
/** Fault Tolerant */
/** */
/**************************************************************************/
/**************************************************************************/
#define FX_SOURCE_CODE
#include "fx_api.h"
#include "fx_fault_tolerant.h"
#include "fx_utility.h"
#ifdef FX_ENABLE_FAULT_TOLERANT
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _fx_fault_tolerant_calculate_checksum PORTABLE C */
/* 6.1 */
/* AUTHOR */
/* */
/* William E. Lamie, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function calculates checksum for consecutive data. The size */
/* of the log file is required to be 4-byte aligned. Therefore this */
/* checksum routine is able to perform 4-byte access. */
/* */
/* INPUT */
/* */
/* data Pointer to data */
/* len Data length */
/* */
/* OUTPUT */
/* */
/* Computed checksum value */
/* */
/* CALLS */
/* */
/* _fx_utility_32_unsigned_read Read a UINT from memory */
/* */
/* CALLED BY */
/* */
/* _fx_fault_tolerant_enable */
/* _fx_fault_tolerant_cleanup_FAT_chain */
/* _fx_fault_tolerant_reset_log_file */
/* _fx_fault_tolerant_set_FAT_chain */
/* _fx_fault_tolerant_transaction_end */
/* */
/* RELEASE HISTORY */
/* */
/* DATE NAME DESCRIPTION */
/* */
/* 05-19-2020 William E. Lamie Initial Version 6.0 */
/* 09-30-2020 William E. Lamie Modified comment(s), */
/* resulting in version 6.1 */
/* */
/**************************************************************************/
USHORT _fx_fault_tolerant_calculate_checksum(UCHAR *data, UINT len)
{
ULONG checksum = 0;
ULONG long_value;
while (len >= 4)
{
/* Read first long value. */
long_value = _fx_utility_32_unsigned_read(data);
/* Calculate checksum. */
checksum += (long_value >> 16) + (long_value & 0xFFFF);
/* Decrease length. */
len -= sizeof(ULONG);
data += sizeof(ULONG);
}
/* Trim high 16 bits of checksum. */
checksum = (checksum & 0xFFFF) + (checksum >> 16);
checksum = (checksum & 0xFFFF) + (checksum >> 16);
return((USHORT)((~checksum) & 0xFFFF));
}
#endif /* FX_ENABLE_FAULT_TOLERANT */
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