1 #include <bitfield/bitfield.h>
2 #include <bitfield/8byte.h>
7 #define EIGHTBYTE_BIT (8 * sizeof(uint64_t))
9 uint64_t bitmask(const uint8_t bit_count) {
10 return (((uint64_t)0x1) << bit_count) - 1;
13 uint8_t eightbyte_get_nibble(const uint64_t source, const uint8_t nibble_index,
14 const bool big_endian) {
15 return get_bit_field(source, NIBBLE_SIZE * nibble_index, NIBBLE_SIZE,
19 uint8_t eightbyte_get_byte(const uint64_t source, const uint8_t byte_index,
20 const bool big_endian) {
21 // TODO we're not handling swapped endianness - we could use get_bit_field
22 // but this might be more efficient
23 return (source >> (EIGHTBYTE_BIT - ((byte_index + 1) * CHAR_BIT))) & 0xFF;
26 uint64_t get_bit_field(uint64_t source, const uint16_t offset,
27 const uint16_t bit_count, const bool big_endian) {
28 int startByte = offset / CHAR_BIT;
29 int endByte = (offset + bit_count - 1) / CHAR_BIT;
32 source = __builtin_bswap64(source);
35 uint8_t* bytes = (uint8_t*)&source;
36 uint64_t ret = bytes[startByte];
37 if(startByte != endByte) {
38 // The lowest byte address contains the most significant bit.
40 for(i = startByte + 1; i <= endByte; i++) {
46 ret >>= 8 - find_end_bit(offset + bit_count);
47 return ret & bitmask(bit_count);
50 bool set_bit_field(uint64_t* destination, uint64_t value, const uint16_t offset,
51 const uint16_t bit_count) {
52 if(value > bitmask(bit_count)) {
56 int shiftDistance = EIGHTBYTE_BIT - offset - bit_count;
57 value <<= shiftDistance;
58 *destination &= ~(bitmask(bit_count) << shiftDistance);
59 *destination |= value;