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#include <bitfield/bitfield.h>
#include <limits.h>
#include <string.h>
#include <stddef.h>
#define NIBBLE_SIZE (CHAR_BIT / 2)
uint64_t bitmask(const uint8_t numBits) {
return (((uint64_t)0x1) << numBits) - 1;
}
static uint16_t bitsToBytes(uint32_t bits) {
uint8_t byte_count = bits / CHAR_BIT;
if(bits % CHAR_BIT != 0) {
++byte_count;
}
return byte_count;
}
uint64_t getBitField(uint64_t data, const uint16_t startBit,
const uint16_t numBits, bool bigEndian) {
uint8_t result[8] = {0};
if(!bigEndian) {
data = __builtin_bswap64(data);
}
copyBitsRightAligned((const uint8_t*)&data, sizeof(data), startBit, numBits,
result, sizeof(result));
uint64_t int_result = 0;
if(!bigEndian) {
// we need to swap the byte order of the array to get it into a
// uint64_t, but it's been right aligned so we have to be more careful
for(int i = 0; i < bitsToBytes(numBits); i++) {
int_result |= result[bitsToBytes(numBits) - i - 1] << (CHAR_BIT * i);
}
} else {
int_result = *(uint64_t*)result;
}
return int_result;
}
/**
* TODO it would be nice to have a warning if you call with this a value that
* won't fit in the number of bits you've specified it should use.
*/
void setBitField(uint64_t* data, uint64_t value, const uint16_t startPos,
const uint16_t numBits) {
int shiftDistance = 64 - startPos - numBits;
value <<= shiftDistance;
*data &= ~(bitmask(numBits) << shiftDistance);
*data |= value;
}
uint8_t nthByte(const uint64_t source, const uint16_t byteNum) {
return (source >> (64 - ((byteNum + 1) * CHAR_BIT))) & 0xFF;
}
uint8_t getNibble(const uint8_t nibble_index, const uint8_t data[],
const uint8_t length) {
uint8_t byte_index = nibble_index / 2;
uint8_t result;
if(byte_index < length) {
result = data[byte_index];
if(nibble_index % 2 == 0) {
result >>= NIBBLE_SIZE;
}
}
result &= bitmask(NIBBLE_SIZE);
return result;
}
uint8_t getByte(const uint8_t byte_index, const uint8_t data[],
const uint8_t length) {
if(byte_index < length) {
return data[byte_index];
}
return 0;
}
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