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#include <bitfield/bitfield.h>
#include <bitfield/8byte.h>
#include <stddef.h>
#include <limits.h>
#include <string.h>
#define EIGHTBYTE_BIT (8 * sizeof(uint64_t))
uint64_t bitmask(const uint8_t bit_count) {
return (((uint64_t)0x1) << bit_count) - 1;
}
static uint16_t bits_to_bytes(uint32_t bits) {
uint8_t byte_count = bits / CHAR_BIT;
if(bits % CHAR_BIT != 0) {
++byte_count;
}
return byte_count;
}
uint8_t eightbyte_get_nibble(const uint64_t source, const uint8_t nibble_index,
const bool big_endian) {
return get_bit_field(source, NIBBLE_SIZE * nibble_index, NIBBLE_SIZE,
big_endian);
}
uint8_t eightbyte_get_byte(const uint64_t source, const uint8_t byte_index,
const bool big_endian) {
// TODO we're not handling swapped endianness - we could use get_bit_field
// but this might be more efficient
return (source >> (EIGHTBYTE_BIT - ((byte_index + 1) * CHAR_BIT))) & 0xFF;
}
uint64_t get_bit_field(uint64_t source, const uint16_t offset,
const uint16_t bit_count, const bool big_endian) {
int startByte = offset / CHAR_BIT;
int endByte = (offset + bit_count - 1) / CHAR_BIT;
if(!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.
int i;
for(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 set_bit_field(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;
}
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