1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
|
#include <bitfield/bitfield.h>
#include <bitfield/8byte.h>
#include <stddef.h>
#include <limits.h>
#include <string.h>
#define EIGHTBYTE_BIT (8 * sizeof(uint64_t))
uint8_t eightbyte_get_nibble(const uint64_t source, const uint8_t nibble_index,
const bool data_is_big_endian) {
return eightbyte_get_bitfield(source, NIBBLE_SIZE * nibble_index, NIBBLE_SIZE,
data_is_big_endian);
}
uint8_t eightbyte_get_byte(uint64_t source, const uint8_t byte_index,
const bool data_is_big_endian) {
if(data_is_big_endian) {
source = __builtin_bswap64(source);
}
return (source >> (EIGHTBYTE_BIT - ((byte_index + 1) * CHAR_BIT))) & 0xFF;
}
// TODO is this funciton necessary anymore? is it any faster for uint64_t than
// get_bitfield(data[], ...)? is the performance better on a 32 bit platform
// like the PIC32?
uint64_t eightbyte_get_bitfield(uint64_t source, const uint16_t offset,
const uint16_t bit_count, const bool data_is_big_endian) {
int startByte = offset / CHAR_BIT;
int endByte = (offset + bit_count - 1) / CHAR_BIT;
if(!data_is_big_endian) {
source = __builtin_bswap64(source);
}
uint8_t* bytes = (uint8_t*)&source;
uint64_t ret = bytes[startByte];
if(startByte != endByte) {
// The lowest byte address contains the most significant bit.
for(uint8_t i = startByte + 1; i <= endByte; i++) {
ret = ret << 8;
ret = ret | bytes[i];
}
}
ret >>= 8 - find_end_bit(offset + bit_count);
return ret & bitmask(bit_count);
}
bool eightbyte_set_bitfield(uint64_t* destination, uint64_t value, const uint16_t offset,
const uint16_t bit_count) {
if(value > bitmask(bit_count)) {
return false;
}
int shiftDistance = EIGHTBYTE_BIT - offset - bit_count;
value <<= shiftDistance;
*destination &= ~(bitmask(bit_count) << shiftDistance);
*destination |= value;
return true;
}
|
