1 /***************************************************************************
2 * Copyright (c) 2024 Microsoft Corporation
3 *
4 * This program and the accompanying materials are made available under the
5 * terms of the MIT License which is available at
6 * https://opensource.org/licenses/MIT.
7 *
8 * SPDX-License-Identifier: MIT
9 **************************************************************************/
10
11
12 /**************************************************************************/
13 /**************************************************************************/
14 /** */
15 /** FileX Component */
16 /** */
17 /** Fault Tolerant */
18 /** */
19 /**************************************************************************/
20 /**************************************************************************/
21
22 #define FX_SOURCE_CODE
23
24 #include "fx_api.h"
25 #include "fx_fault_tolerant.h"
26 #include "fx_utility.h"
27
28
29 #ifdef FX_ENABLE_FAULT_TOLERANT
30 /**************************************************************************/
31 /* */
32 /* FUNCTION RELEASE */
33 /* */
34 /* _fx_fault_tolerant_calculate_checksum PORTABLE C */
35 /* 6.1 */
36 /* AUTHOR */
37 /* */
38 /* William E. Lamie, Microsoft Corporation */
39 /* */
40 /* DESCRIPTION */
41 /* */
42 /* This function calculates checksum for consecutive data. The size */
43 /* of the log file is required to be 4-byte aligned. Therefore this */
44 /* checksum routine is able to perform 4-byte access. */
45 /* */
46 /* INPUT */
47 /* */
48 /* data Pointer to data */
49 /* len Data length */
50 /* */
51 /* OUTPUT */
52 /* */
53 /* Computed checksum value */
54 /* */
55 /* CALLS */
56 /* */
57 /* _fx_utility_32_unsigned_read Read a UINT from memory */
58 /* */
59 /* CALLED BY */
60 /* */
61 /* _fx_fault_tolerant_enable */
62 /* _fx_fault_tolerant_cleanup_FAT_chain */
63 /* _fx_fault_tolerant_reset_log_file */
64 /* _fx_fault_tolerant_set_FAT_chain */
65 /* _fx_fault_tolerant_transaction_end */
66 /* */
67 /* RELEASE HISTORY */
68 /* */
69 /* DATE NAME DESCRIPTION */
70 /* */
71 /* 05-19-2020 William E. Lamie Initial Version 6.0 */
72 /* 09-30-2020 William E. Lamie Modified comment(s), */
73 /* resulting in version 6.1 */
74 /* */
75 /**************************************************************************/
_fx_fault_tolerant_calculate_checksum(UCHAR * data,UINT len)76 USHORT _fx_fault_tolerant_calculate_checksum(UCHAR *data, UINT len)
77 {
78 ULONG checksum = 0;
79 ULONG long_value;
80
81 while (len >= 4)
82 {
83
84 /* Read first long value. */
85 long_value = _fx_utility_32_unsigned_read(data);
86
87 /* Calculate checksum. */
88 checksum += (long_value >> 16) + (long_value & 0xFFFF);
89
90 /* Decrease length. */
91 len -= sizeof(ULONG);
92 data += sizeof(ULONG);
93 }
94
95 /* Trim high 16 bits of checksum. */
96 checksum = (checksum & 0xFFFF) + (checksum >> 16);
97 checksum = (checksum & 0xFFFF) + (checksum >> 16);
98
99 return((USHORT)((~checksum) & 0xFFFF));
100 }
101 #endif /* FX_ENABLE_FAULT_TOLERANT */
102
103
