--- /dev/null
+#ifndef __BITFIELD_H__
+#define __BITFIELD_H__
+
+#include <stdint.h>
+#include <stdbool.h>
+
+/* Public: Reads a subset of bits from a byte array.
+ *
+ * data - the bytes in question.
+ * startPos - 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
+ * 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
+ * use the value we find in the field (assuming the embedded platform is little
+ * endian).
+ *
+ * For example, the bit layout of the value "42" (i.e. 00101010 set at position
+ * 14 with length 6 is:
+ *
+ * 000000000000001010100000000000000000000000000000000000000000000
+ *
+ * and the same value and position but with length 8 is:
+ *
+ * 000000000000000010101000000000000000000000000000000000000000000
+ *
+ * If the architecture where is code is running is little-endian, the input data
+ * will be swapped before grabbing the bit field.
+ *
+ * Examples
+ *
+ * uint64_t value = getBitField(data, 2, 4);
+ *
+ * Returns the value of the requested bit field.
+ */
+uint64_t getBitField(uint64_t data, int startPos, int numBits, bool bigEndian);
+
+/* Public: Set the bit field in the given data array to the new value.
+ *
+ * data - a byte array with size at least startPos + numBits.
+ * value - the value to set in the bit field.
+ * startPos - the starting index of the bit field (beginning from 0).
+ */
+void setBitField(uint64_t* data, uint64_t value, int startPos, int numBits);
+
+/* 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.
+ *
+ * Returns the requested byte from the source bytes.
+ */
+uint8_t nthByte(uint64_t source, int byteNum);
+
+#endif // __BITFIELD_H__
--- /dev/null
+#include <check.h>
+#include <stdint.h>
+#include <bitfield/bitfield.h>
+
+START_TEST (test_large_bitmask)
+{
+ // yeah, this isn't a public method but I wanted to unit test it to track
+ // down a bug
+ extern uint64_t bitmask(int numBits);
+ uint64_t result = bitmask(32);
+ fail_if(result != 0xffffffff);
+}
+END_TEST
+
+START_TEST (test_one_bit_not_swapped)
+{
+ uint64_t data = 0x80;
+ uint64_t result = getBitField(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);
+ fail_unless(result == 0x1,
+ "First bits in 0x%X was 0x%X instead of 0x1", data, result);
+}
+END_TEST
+
+START_TEST (test_32_bit_parse)
+{
+ uint64_t data = 0x0402574d555a0401;
+ uint64_t result = getBitField(data, 16, 32, false);
+ uint64_t expectedValue = 0x574d555a;
+ fail_unless(result == expectedValue,
+ "Field retrieved in 0x%X was 0x%X instead of %d", data,
+ result, expectedValue);
+}
+END_TEST
+
+START_TEST (test_16_bit_parse)
+{
+ uint64_t data = 0xF34DFCFF00000000;
+ uint64_t result = getBitField(data, 16, 16, false);
+ uint64_t expectedValue = 0xFCFF;
+ fail_unless(result == expectedValue,
+ "Field retrieved in 0x%X was 0x%X instead of %d", data,
+ result, expectedValue);
+}
+END_TEST
+
+START_TEST (test_one_byte)
+{
+ uint64_t data = 0xFA00000000000000;
+ uint64_t result = getBitField(data, 0, 4, false);
+ fail_unless(result == 0xF,
+ "First 4 bits in 0x%X was 0x%X instead of 0xF", data, result);
+ result = getBitField(data, 4, 4, false);
+ fail_unless(result == 0xA,
+ "First 4 bits in 0x%X was 0x%X instead of 0xA", data, result);
+ result = getBitField(data, 0, 8, false);
+ fail_unless(result == 0xFA,
+ "All bits in 0x%X were 0x%X instead of 0x%X", data, result, data);
+}
+END_TEST
+
+START_TEST (test_multi_byte)
+{
+ uint64_t data = 0x12FA000000000000;
+ uint64_t result = getBitField(data, 0, 4, false);
+ fail_unless(result == 0x1,
+ "First 4 bits in 0x%X was 0x%X instead of 0xF", (data >> 60) & 0xF,
+ result);
+ result = getBitField(data, 4, 4, false);
+ fail_unless(result == 0x2,
+ "Second 4 bits in 0x%X was %d instead of 0xA", (data >> 56) & 0xF,
+ result);
+ result = getBitField(data, 8, 4, false);
+ fail_unless(result == 0xF,
+ "First 4 bits in 0x%X was %d instead of 0x1", (data >> 52) & 0xF,
+ result);
+ result = getBitField(data, 12, 4, false);
+ fail_unless(result == 0xA,
+ "Second 4 bits in 0x%X was %d instead of 0x2", (data >> 48) % 0xF,
+ result);
+}
+END_TEST
+
+START_TEST (test_get_multi_byte)
+{
+ uint64_t data = 0x12FA000000000000;
+ uint64_t result = getBitField(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);
+ 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);
+ ck_assert_int_eq(result, 0x1);
+ data = 0;
+ setBitField(&data, 1, 1, 1);
+ result = getBitField(data, 1, 1, false);
+ ck_assert_int_eq(result, 0x1);
+
+ data = 0;
+ setBitField(&data, 0xf, 3, 4);
+ result = getBitField(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);
+ fail_unless(result == 0x4fc8,
+ "Field retrieved in 0x%X was 0x%X instead of 0x%X", data, result,
+ 0xc84f);
+
+ data = 0x8000000000000000;
+ setBitField(&data, 1, 21, 1);
+ fail_unless(data == 0x8000040000000000LLU,
+ "Expected combined value 0x8000040000000000 but got 0x%X%X",
+ data >> 32, data);
+}
+END_TEST
+
+START_TEST (test_set_off_byte_boundary)
+{
+ uint64_t data = 0xFFFC4DF300000000;
+ setBitField(&data, 0x12, 12, 8);
+ uint64_t result = getBitField(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);
+ fail_unless(result == 0x12,
+ "Field set in 0x%X%X%X%X was %d instead of %d", data, result,
+ 0x12);
+
+ data = 0xFFFC4DF300000000LLU;
+ setBitField(&data, 0x2, 11, 5);
+ result = getBitField(data, 11, 5, false);
+ fail_unless(result == 0x2,
+ "Field set in 0x%X%X%X%X was %d instead of %d", data, result,
+ 0x2);
+}
+END_TEST
+
+START_TEST(test_nth_byte)
+{
+ uint64_t data = 0x00000000F34DFCFF;
+ uint8_t result = nthByte(data, 0);
+ uint8_t expected = 0x0;
+ ck_assert_int_eq(result, expected);
+
+ result = nthByte(data, 4);
+ expected = 0xF3;
+ ck_assert_int_eq(result, expected);
+
+ result = nthByte(data, 5);
+ expected = 0x4D;
+ ck_assert_int_eq(result, expected);
+
+ result = nthByte(data, 6);
+ expected = 0xFC;
+ ck_assert_int_eq(result, expected);
+
+ result = nthByte(data, 7);
+ expected = 0xFF;
+ ck_assert_int_eq(result, expected);
+}
+END_TEST
+
+Suite* bitfieldSuite(void) {
+ Suite* s = suite_create("bitfield");
+ TCase *tc_core = tcase_create("core");
+ tcase_add_test(tc_core, test_large_bitmask);
+ tcase_add_test(tc_core, test_one_bit);
+ tcase_add_test(tc_core, test_one_bit_not_swapped);
+ tcase_add_test(tc_core, test_one_byte);
+ tcase_add_test(tc_core, test_16_bit_parse);
+ tcase_add_test(tc_core, test_32_bit_parse);
+ tcase_add_test(tc_core, test_multi_byte);
+ tcase_add_test(tc_core, test_get_multi_byte);
+ tcase_add_test(tc_core, test_get_off_byte_boundary);
+ tcase_add_test(tc_core, test_set_field);
+ tcase_add_test(tc_core, test_set_doesnt_clobber_existing_data);
+ tcase_add_test(tc_core, test_set_off_byte_boundary);
+ tcase_add_test(tc_core, test_set_odd_number_of_bits);
+ tcase_add_test(tc_core, test_nth_byte);
+ suite_add_tcase(s, tc_core);
+
+ return s;
+}
+
+int main(void) {
+ int numberFailed;
+ Suite* s = bitfieldSuite();
+ SRunner *sr = srunner_create(s);
+ // Don't fork so we can actually use gdb
+ srunner_set_fork_status(sr, CK_NOFORK);
+ srunner_run_all(sr, CK_NORMAL);
+ numberFailed = srunner_ntests_failed(sr);
+ srunner_free(sr);
+ return (numberFailed == 0) ? 0 : 1;
+}