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Checksum.cpp
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1 // ======================================================================
2 // \title CFDP/Checksum/Checksum.cpp
3 // \author bocchino
4 // \brief cpp file for CFDP checksum class
5 //
6 // \copyright
7 // Copyright 2009-2016, by the California Institute of Technology.
8 // ALL RIGHTS RESERVED. United States Government Sponsorship
9 // acknowledged.
10 //
11 // ======================================================================
12 
14 #include "Fw/Types/Assert.hpp"
15 
16 static U32 min(const U32 a, const U32 b) {
17  return (a < b) ? a : b;
18 }
19 
20 namespace CFDP {
21 
23  Checksum() : m_value(0)
24  {
25 
26  }
27 
29  Checksum(const U32 value) : m_value(value)
30  {
31 
32  }
33 
35  Checksum(const Checksum &original)
36  {
37  this->m_value = original.getValue();
38  }
39 
41  ~Checksum()
42  {
43 
44  }
45 
47  operator=(const Checksum& checksum)
48  {
49  this->m_value = checksum.m_value;
50  return *this;
51  }
52 
54  operator==(const Checksum& checksum) const
55  {
56  return this->m_value == checksum.m_value;
57  }
58 
60  operator!=(const Checksum& checksum) const
61  {
62  return not (*this == checksum);
63  }
64 
66  getValue() const
67  {
68  return this->m_value;
69  }
70 
72  update(
73  const U8 *const data,
74  const U32 offset,
75  const U32 length
76  )
77  {
78  U32 index = 0;
79 
80  // Add the first word unaligned if necessary
81  const U32 offsetMod4 = offset % 4;
82  if (offsetMod4 != 0) {
83  const U8 wordLength = static_cast<U8>(min(length, 4 - offsetMod4));
84  this->addWordUnaligned(
85  &data[index],
86  static_cast<U8>(offset + index),
87  wordLength
88  );
89  index += wordLength;
90  }
91 
92  // Add the middle words aligned
93  for ( ; index + 4 <= length; index += 4) {
94  addWordAligned(&data[index]);
95  }
96 
97  // Add the last word unaligned if necessary
98  if (index < length) {
99  const U8 wordLength = static_cast<U8>(length - index);
100  this->addWordUnaligned(
101  &data[index],
102  static_cast<U8>(offset + index),
103  wordLength
104  );
105  }
106 
107  }
108 
109  void Checksum ::
110  addWordAligned(const U8 *const word)
111  {
112  for (U8 i = 0; i < 4; ++i) {
113  addByteAtOffset(word[i], i);
114  }
115  }
116 
117  void Checksum ::
118  addWordUnaligned(
119  const U8 *word,
120  const U8 position,
121  const U8 length
122  )
123  {
124  FW_ASSERT(length < 4);
125  U8 offset = position % 4;
126  for (U8 i = 0; i < length; ++i) {
127  addByteAtOffset(word[i], offset);
128  ++offset;
129  if (offset == 4) {
130  offset = 0;
131  }
132  }
133  }
134 
135  void Checksum ::
136  addByteAtOffset(
137  const U8 byte,
138  const U8 offset
139  )
140  {
141  FW_ASSERT(offset < 4);
142  const U32 addend = static_cast<U32>(byte) << (8*(3-offset));
143  this->m_value += addend;
144  }
145 
146 }
#define FW_ASSERT(...)
Definition: Assert.hpp:14
uint8_t U8
8-bit unsigned integer
Definition: BasicTypes.h:30
static U32 min(const U32 a, const U32 b)
Definition: Checksum.cpp:16
Class representing a 32-bit checksum as mandated by the CCSDS File Delivery Protocol.
Definition: Checksum.hpp:53
Checksum & operator=(const Checksum &checksum)
Assign checksum to this.
Definition: Checksum.cpp:47
U32 getValue() const
Get the checksum value.
Definition: Checksum.cpp:66
~Checksum()
Destroy a Checksum object.
Definition: Checksum.cpp:41
bool operator!=(const Checksum &checksum) const
Compare checksum and this for inequality.
Definition: Checksum.cpp:60
bool operator==(const Checksum &checksum) const
Compare checksum and this for equality.
Definition: Checksum.cpp:54
Checksum()
Construct a fresh Checksum object.
Definition: Checksum.cpp:23
void update(const U8 *const data, const U32 offset, const U32 length)
Definition: Checksum.cpp:72