#include <limits.h>
#include <string.h>
-uint64_t bitmask(const uint8_t numBits) {
- return (((uint64_t)0x1) << numBits) - 1;
+#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 bitsToBytes(uint32_t bits) {
+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;
}
-uint64_t getBitField(uint64_t data, const uint16_t startBit,
- const uint16_t numBits, bool bigEndian) {
+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};
- if(!bigEndian) {
- data = __builtin_bswap64(data);
+ if(!big_endian) {
+ source = __builtin_bswap64(source);
}
- copyBitsRightAligned((const uint8_t*)&data, sizeof(data), startBit, numBits,
- result, sizeof(result));
+ copyBitsRightAligned((const uint8_t*)&source, sizeof(source), startBit,
+ bit_count, result, sizeof(result));
uint64_t int_result = 0;
- if(!bigEndian) {
+ 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 < bitsToBytes(numBits); i++) {
- int_result |= result[bitsToBytes(numBits) - i - 1] << (CHAR_BIT * i);
+ for(int i = 0; i < bits_to_bytes(bit_count); i++) {
+ int_result |= result[bits_to_bytes(bit_count) - i - 1] << (CHAR_BIT * i);
}
} else {
int_result = *(uint64_t*)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;
+void set_bit_field(uint64_t* destination, uint64_t value, const uint16_t offset,
+ const uint16_t bit_count) {
+ int shiftDistance = EIGHTBYTE_BIT - offset - bit_count;
value <<= shiftDistance;
- *data &= ~(bitmask(numBits) << shiftDistance);
- *data |= value;
+ *destination &= ~(bitmask(bit_count) << shiftDistance);
+ *destination |= value;
}
-uint8_t nthByte(const uint64_t source, const uint16_t byteNum) {
- return (source >> (64 - ((byteNum + 1) * CHAR_BIT))) & 0xFF;
+uint8_t nth_byte(const uint64_t source, const uint16_t byte_index) {
+ return (source >> (EIGHTBYTE_BIT - ((byte_index + 1) * CHAR_BIT))) & 0xFF;
}
// inefficient on 32-bit platforms. how much work is it to switch vi-firmware
// to using uint8_t*?
-/* Public: Reads a subset of bits from a byte array.
+/* Public: Reads a subset of bits into a uint64_t.
*
- * data - the bytes in question.
- * startPos - the starting index of the bit field (beginning from 0).
+ * source - the bytes in question.
+ * offset - the starting index of the bit field (beginning from 0).
* numBits - the width of the bit field to extract.
- * bigEndian - if the data passed in is little endian, set this to false and it
+ * big_endian - if the data passed in is little endian, set this to false and it
* will be flipped before grabbing the bit field.
*
* Bit fields are positioned according to big-endian bit layout, but inside the
* bit field, values are represented as little-endian. Therefore, to get the bit
- * field, we swap the overall byte order if bigEndian == false and
+ * field, we swap the overall byte order if big_endian == false and
* use the value we find in the field (assuming the embedded platform is little
* endian).
*
*
* Examples
*
- * uint64_t value = getBitField(data, 2, 4);
+ * uint64_t value = get_bit_field(data, 2, 4);
*
* Returns the value of the requested bit field.
*/
-uint64_t getBitField(uint64_t data, const uint16_t startPos,
- const uint16_t numBits, bool bigEndian);
+uint64_t get_bit_field(uint64_t source, const uint16_t offset,
+ const uint16_t bit_count, bool big_endian);
/* Public: Set the bit field in the given data array to the new value.
*
- * data - a byte array with size at least startPos + numBits.
+ * destination - a byte array with size at least offset + bit_count.
* value - the value to set in the bit field.
- * startPos - the starting index of the bit field (beginning from 0).
+ * offset - the starting index of the bit field (beginning from 0).
+ * bit_count - the number of bits to set in the data.
*/
-void setBitField(uint64_t* data, uint64_t value, const uint16_t startPos,
- const uint16_t numBits);
+void set_bit_field(uint64_t* destination, uint64_t value, const uint16_t offset,
+ const uint16_t bit_count);
/* Public: Retreive the nth byte out of 8 bytes in a uint64_t.
*
* source - the source data to retreive the byte from.
- * byteNum - the index of the byte, starting at 0 and assuming big-endian order.
+ * byte_index - the index of the byte, starting at 0 and assuming big-endian order.
*
* Returns the requested byte from the source bytes.
*/
-uint8_t nthByte(const uint64_t source, const uint16_t byteNum);
+uint8_t nth_byte(const uint64_t source, const uint16_t byte_index);
#ifdef __cplusplus
}
START_TEST (test_one_bit_not_swapped)
{
uint64_t data = 0x80;
- uint64_t result = getBitField(data, 0, 1, false);
+ uint64_t result = get_bit_field(data, 0, 1, false);
fail_if(result == 1);
}
END_TEST
START_TEST (test_one_bit)
{
uint64_t data = 0x8000000000000000;
- uint64_t result = getBitField(data, 0, 1, false);
+ uint64_t result = get_bit_field(data, 0, 1, false);
fail_unless(result == 0x1,
"First bit in 0x%llx was 0x%llx instead of 0x1", data, result);
}
START_TEST (test_32_bit_parse)
{
uint64_t data = 0x0402574d555a0401;
- uint64_t result = getBitField(data, 16, 32, false);
+ uint64_t result = get_bit_field(data, 16, 32, false);
uint64_t expectedValue = 0x574d555a;
fail_unless(result == expectedValue,
"Field retrieved in 0x%llx was 0x%llx instead of 0x%llx", data,
START_TEST (test_16_bit_parse)
{
uint64_t data = 0xF34DFCFF00000000;
- uint64_t result = getBitField(data, 16, 16, false);
+ uint64_t result = get_bit_field(data, 16, 16, false);
uint64_t expectedValue = 0xFCFF;
fail_unless(result == expectedValue,
"Field retrieved in 0x%llx was 0x%llx instead of 0x%llx", data,
START_TEST (test_one_byte)
{
uint64_t data = 0xFA00000000000000;
- uint64_t result = getBitField(data, 0, 4, false);
+ uint64_t result = get_bit_field(data, 0, 4, false);
fail_unless(result == 0xF,
"First 4 bits in 0x%llx was 0x%llx instead of 0xF", data, result);
- result = getBitField(data, 4, 4, false);
+ result = get_bit_field(data, 4, 4, false);
fail_unless(result == 0xA,
"First 4 bits in 0x%llx was 0x%llx instead of 0xA", data, result);
- result = getBitField(data, 0, 8, false);
+ result = get_bit_field(data, 0, 8, false);
fail_unless(result == 0xFA,
"All bits in 0x%llx were 0x%llx instead of 0x%llx", data, result, data);
}
START_TEST (test_multi_byte)
{
uint64_t data = 0x12FA000000000000;
- uint64_t result = getBitField(data, 0, 4, false);
+ uint64_t result = get_bit_field(data, 0, 4, false);
fail_unless(result == 0x1,
"First 4 bits in 0x%llx was 0x%llx instead of 0xF", (data >> 60) & 0xF,
result);
- result = getBitField(data, 4, 4, false);
+ result = get_bit_field(data, 4, 4, false);
fail_unless(result == 0x2,
"Second 4 bits in 0x%llx was 0x%llx instead of 0xA", (data >> 56) & 0xF,
result);
- result = getBitField(data, 8, 4, false);
+ result = get_bit_field(data, 8, 4, false);
fail_unless(result == 0xF,
"First 4 bits in 0x%llx was 0x%llx instead of 0x1", (data >> 52) & 0xF,
result);
- result = getBitField(data, 12, 4, false);
+ result = get_bit_field(data, 12, 4, false);
fail_unless(result == 0xA,
"Second 4 bits in 0x%llx was 0x%llx instead of 0x2", (data >> 48) % 0xF,
result);
START_TEST (test_get_multi_byte)
{
uint64_t data = 0x12FA000000000000;
- uint64_t result = getBitField(data, 0, 9, false);
+ uint64_t result = get_bit_field(data, 0, 9, false);
ck_assert_int_eq(result, 0x25);
}
END_TEST
START_TEST (test_get_off_byte_boundary)
{
uint64_t data = 0x000012FA00000000;
- uint64_t result = getBitField(data, 12, 8, false);
+ uint64_t result = get_bit_field(data, 12, 8, false);
ck_assert_int_eq(result, 0x01);
} END_TEST
START_TEST (test_set_field)
{
uint64_t data = 0;
- setBitField(&data, 1, 0, 1);
- uint64_t result = getBitField(data, 0, 1, false);
+ set_bit_field(&data, 1, 0, 1);
+ uint64_t result = get_bit_field(data, 0, 1, false);
ck_assert_int_eq(result, 0x1);
data = 0;
- setBitField(&data, 1, 1, 1);
- result = getBitField(data, 1, 1, false);
+ set_bit_field(&data, 1, 1, 1);
+ result = get_bit_field(data, 1, 1, false);
ck_assert_int_eq(result, 0x1);
data = 0;
- setBitField(&data, 0xf, 3, 4);
- result = getBitField(data, 3, 4, false);
+ set_bit_field(&data, 0xf, 3, 4);
+ result = get_bit_field(data, 3, 4, false);
ck_assert_int_eq(result, 0xf);
}
END_TEST
START_TEST (test_set_doesnt_clobber_existing_data)
{
uint64_t data = 0xFFFC4DF300000000;
- setBitField(&data, 0x4fc8, 16, 16);
- uint64_t result = getBitField(data, 16, 16, false);
+ set_bit_field(&data, 0x4fc8, 16, 16);
+ uint64_t result = get_bit_field(data, 16, 16, false);
fail_unless(result == 0x4fc8,
"Field retrieved in 0x%llx was 0x%llx instead of 0x%x", data, result,
0xc84f);
data = 0x8000000000000000;
- setBitField(&data, 1, 21, 1);
+ set_bit_field(&data, 1, 21, 1);
fail_unless(data == 0x8000040000000000LLU,
"Expected combined value 0x8000040000000000 but got 0x%llx%llx",
data >> 32, data);
START_TEST (test_set_off_byte_boundary)
{
uint64_t data = 0xFFFC4DF300000000;
- setBitField(&data, 0x12, 12, 8);
- uint64_t result = getBitField(data, 12, 12, false);
+ set_bit_field(&data, 0x12, 12, 8);
+ uint64_t result = get_bit_field(data, 12, 12, false);
ck_assert_int_eq(result,0x12d);
}
END_TEST
START_TEST (test_set_odd_number_of_bits)
{
uint64_t data = 0xFFFC4DF300000000LLU;
- setBitField(&data, 0x12, 11, 5);
- uint64_t result = getBitField(data, 11, 5, false);
+ set_bit_field(&data, 0x12, 11, 5);
+ uint64_t result = get_bit_field(data, 11, 5, false);
fail_unless(result == 0x12,
"Field set in 0x%llx%llx%llx%llx was 0x%llx instead of 0x%llx", data, result,
0x12);
data = 0xFFFC4DF300000000LLU;
- setBitField(&data, 0x2, 11, 5);
- result = getBitField(data, 11, 5, false);
+ set_bit_field(&data, 0x2, 11, 5);
+ result = get_bit_field(data, 11, 5, false);
fail_unless(result == 0x2,
"Field set in 0x%llx%llx%llx%llx was 0x%llx instead of 0x%llx", data, result,
0x2);
START_TEST(test_nth_byte)
{
uint64_t data = 0x00000000F34DFCFF;
- uint8_t result = nthByte(data, 0);
+ uint8_t result = nth_byte(data, 0);
uint8_t expected = 0x0;
ck_assert_int_eq(result, expected);
- result = nthByte(data, 4);
+ result = nth_byte(data, 4);
expected = 0xF3;
ck_assert_int_eq(result, expected);
- result = nthByte(data, 5);
+ result = nth_byte(data, 5);
expected = 0x4D;
ck_assert_int_eq(result, expected);
- result = nthByte(data, 6);
+ result = nth_byte(data, 6);
expected = 0xFC;
ck_assert_int_eq(result, expected);
- result = nthByte(data, 7);
+ result = nth_byte(data, 7);
expected = 0xFF;
ck_assert_int_eq(result, expected);
}