return byte_count;
}
-uint64_t get_bit_field(uint64_t source, const uint16_t startBit,
- const uint16_t bit_count, bool big_endian) {
- uint8_t result[8] = {0};
+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);
}
- copyBitsRightAligned((const uint8_t*)&source, sizeof(source), startBit,
- bit_count, result, sizeof(result));
- uint64_t int_result = 0;
- if(!big_endian) {
- // 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 < bits_to_bytes(bit_count); i++) {
- int_result |= result[bits_to_bytes(bit_count) - i - 1] << (CHAR_BIT * i);
+ 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];
}
- } else {
- int_result = *(uint64_t*)result;
}
- return int_result;
+
+ 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,
*destination |= value;
return true;
}
-
-uint8_t nth_byte(const uint64_t source, const uint16_t byte_index) {
- return (source >> (EIGHTBYTE_BIT - ((byte_index + 1) * CHAR_BIT))) & 0xFF;
-}
-