util.h
Go to the documentation of this file.
1 /*
2  * Copyright (c) 2020, James Jackson, Daniel Koch, and Trey Henrichsen, BYU MAGICC Lab
3  *
4  * All rights reserved.
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions are met:
8  *
9  * * Redistributions of source code must retain the above copyright notice, this
10  * list of conditions and the following disclaimer.
11  *
12  * * Redistributions in binary form must reproduce the above copyright notice,
13  * this list of conditions and the following disclaimer in the documentation
14  * and/or other materials provided with the distribution.
15  *
16  * * Neither the name of the copyright holder nor the names of its
17  * contributors may be used to endorse or promote products derived from
18  * this software without specific prior written permission.
19  *
20  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
21  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
23  * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
26  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
27  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
28  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
29  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30  */
31 
32 #ifndef ROSFLIGHT_FIRMWARE_UTIL_H
33 #define ROSFLIGHT_FIRMWARE_UTIL_H
34 
35 #include <cmath>
36 #include <cstddef>
37 #include <cstdint>
38 
39 namespace rosflight_firmware
40 {
52 inline uint16_t checksum_fletcher16(const uint8_t *src, size_t len, bool finalize = true, uint16_t start = 0)
53 {
54  static constexpr size_t max_block_length = 5800; // guarantee that no overflow will occur (reduce from standard value
55  // to account for values in 'start')
56 
57  uint32_t c1 = (start & 0xFF00) >> 8;
58  uint32_t c2 = start & 0x00FF;
59 
60  size_t block_length;
61  for (; len > 0; len -= block_length)
62  {
63  block_length = len < max_block_length ? len : max_block_length;
64  for (size_t i = 0; i < block_length; i++)
65  {
66  c1 += *(src++);
67  c2 += c1;
68  }
69 
70  c1 %= 255;
71  c2 %= 255;
72  }
73 
74  uint16_t checksum = c1 << 8 | c2;
75 
76  if (finalize && checksum == 0)
77  checksum = 0xFFFF;
78 
79  return checksum;
80 }
81 
82 } // namespace rosflight_firmware
83 
84 #endif // ROSFLIGHT_FIRMWARE_UTIL_H
ROSCPP_DECL void start()
uint16_t checksum_fletcher16(const uint8_t *src, size_t len, bool finalize=true, uint16_t start=0)
Fletcher 16-bit checksum.
Definition: util.h:52


rosflight_firmware
Author(s): Daniel Koch , James Jackson
autogenerated on Fri Oct 9 2020 03:17:17